Processes and systems for producing fuels from a feed fuel

Abstract

The disclosure relates to processes and systems for producing two fuels, including a main fuel and a secondary fuel, from a feed fuel that comprises alcohol, suitable for use in connection with a compression ignition engine. The process involves the catalytic conversion, in a reactor, of the alcohol content in the feed fuel into an ether, with a water byproduct. The reactor output, which comprises unreacted alcohol in addition to the ether and water; is condensed and then a liquid product comprising unreacted alcohol and water is separated from an ether-concentrated vapour. The ether-concentrated vapour is used to produce the secondary fuel. The liquid unreacted alcohol and water byproduct, with a lower ether content, is then re-directed within the process. Also described are strategies to protect the catalyst used in the catalytic conversion.

Description

PROCESSES AND SYSTEMS FOR PRODUCING FUELS FROM A FEED FUELFIELD

[0001] The present application relates to processes and systems for producing two fuels, including a main fuel and a secondary fuel,, from a feed fuel. The present application also relates to the use of a feed fuel to produce two such fuel compositions. The process, systems and uses are particularly suited to the production of two fuels for the operation of a compression ignition engine fueled with both the main fuel and the secondary fuel. The present application further concerns strategies for producing a secondary fuel from a feed fuel in a mobile environment. The present application claims priority from AU202S900114, the entirety of which is incorporated by cross-reference.BACKGROUND

[0002] Cleaner fuels for use in compression ignition engines - commonly referred to as "diesel fuels" are more of a necessity today than ever before, and a number of options are being examined by industry.

[0003] Fuels based on either methanol or ethanol for use in compression ignition engines have gained increased interest in recent times, but commercial uptake at industrial scale has not yet been achieved. Alcohols can be produced from renewable resources, and have the potential to significantly lower engine emissions. Emissions are further lowered by using a combination of water with the methanol in the fuel in accordance with the technology described by Gane Energy & Resources Pty Ltd in International patent application PCT / AU2011 / 001531. While methanol has a low cetane number, and is difficult to ignite in a compression ignition engine, this problem is overcome by using a pilot fuel to initiate ignition, following which methanol combustion can take place. While the use of a pilot fuel (which may be described as a secondary fuel) provides a promising approach for the use of methanol in compression ignition engines, a number of impediments persist for a range of applications.

[0004] As one example, there is resistance in industry to create the infrastructure to deliver two separate fuel compositions to fueling locations for vehicles or machinery to be run on methanol or other alcohol-based fuels. Fueling of engines has historically been based on the delivery of one fuel composition (e.g. diesel fuel) to a fueling location, and while it may appear on its face straight-forward to replicate that infrastructure for the delivery of a secondary fuel, there are many technical factors that make this unattractive. Secondary fuels may introduce additional work in terms of supply chain and fuels management. Current engines typically require only one fuel composition to be used, and there is resistance to adopting a change that would add to supply chain complexity.

[0005] One solution to the problem of supply of two fuel compositions involves production of the secondary fuel on-board the engine, where the secondary fuel is created from the primary fuel delivered to the engine. This option is possible where the secondary fuel is an ether, as ether is able to be produced from alcohols through a dehydration reaction. On-board conversion of methanol to dimethyl ether, andfrom ethanol to diethyl ether has been explored previously, and test work has been promising. However, challenges remain.

[0006] For one example, test work exploring the ability to convert a primary fuel into a secondary fuel on-board the engine tends to focus on the use of chemical-grade methanol (typically >99.8%) as the main fuel. There is a scarcity of literature exploring the suitability of use of mixed-component fuel compositions, or lower purity commercial grades of alcohols as the fuel source, and how those mixed-component or impure feed fuels may be incorporated into a commercially viable system. The presence of multiple components in the input feed fuel has the potential to cause downstream issues that need to be addressed, and work completed to date does not sufficiently address some key downstream problems.

[0007] Another related impediment to commercial uptake is fuel cost. As noted above, test work to date has been predominantly performed using higher grades of methanol (e.g. IMPCA specification methanol). However, such grades of methanol are more costly to produce. Fuel grades of methanol are more cost-effective for use in fuel compositions, but the contaminants present need to be taken into account when devising complete systems for use in engines.

[0008] Even where conversion of alcohol (e.g. methanol) to ether (e.g. dimethyl ether, or DME) for the production of DME from alcohol has been contemplated, the dehydration reaction from alcohol to ether is incomplete. This has an impact on the control of the composition of the pilot fuel delivered to the engine. While upgrading of the reactor output has been contemplated previously, prior disclosed approaches are impractical. Other test work has assumed the delivery of 100% DME to the engine as the secondary fuel, which comes with its own challenges. A more practical and complete solution for addressing the problem of the reactor composition output is desired.

[0009] A further problem where there is production of a secondary fuel from a main fuel is the reliability of the conversion process. Dehydration of alcohols to the corresponding ethers requires a catalyst for conversion, and in addition to normal deactivation of such catalysts over time, there can be accelerated decline due to build-up of carbon or other degrading species and / or physical or structural catalyst damage. Carbon build-up can be accelerated when the catalyst is exposed to excessively high temperature conditions. Structural damage can be accelerated due to the impact of free water and / or freezing of water in the catalyst material. It would lower the impediments to commercial uptake if such problems are reduced or circumvented in the processes to be used when generating two fuel compositions from a single feed fuel for the fueling of a compression ignition engine.

[0010] Additional problems may, in some operations, relate to reliability of supply of ether (such as dimethyl ether) in terms of continuity of supply and quality; overall engine reliability for extended periods where the secondary fuel is produced within the engine; the desirability to accommodate variable conversion rates for conversion of the main fuel to the secondary fuel; tolerance to a wide range of climatic conditions and / or altitudes; catalyst integrity; dealing with byproducts such as water, especiallyfor applications where a waste accumulation cannot be tolerated; the need for flexibility in operation of the unit; and efficiency (e.g. maximum ether delivery capability for a unit of minimum size).

[0011] It is an object of the present application to provide strategies to address one or more of the above problems.SUMMARY

[0012] A comprehensive process for the production of two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel, and for operating an engine with those two fuel compositions, has been devised. A number of independent strategies have been implemented in the comprehensive process, each of which may be used independently or in combination. In the following, a number of those strategies are articulated in separate aspects of the invention. Each strategy addresses a problem that is faced with existing technologies for operating a compression ignition engine with a dual-fuel system.

[0013] In a first aspect, there is provided a process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel comprising alcohol, the process comprising:- storing the feed fuel in a feed fuel tank;- directing a first stream of the feed fuel from the feed fuel tank to a heater and heating the first stream of feed fuel to evaporate alcohol in the feed fuel;- optionally separating a liquid residue from the evaporated alcohol;- producing main fuel from a second stream of the feed fuel;- directing the evaporated alcohol to a reactor and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water; - condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output;- producing secondary fuel from the ether-concentrated portion of the reactor output; and- combining the separated unreacted alcohol and water with one or more of:(i) the first stream of the feed fuel, upstream of said heating step, or upstream of, or at, said liquid residue separation; or(ii) the reactor output, upstream of the condensation of the reactor output, or(iii) the second stream of the feed fuel, for incorporation as a component of the main fuel.

[0014] In a variant of the above first aspect, there is provided a process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel comprising alcohol, the process comprising:- storing the feed fuel in a feed fuel tank;- directing a first stream of the feed fuel from the feed fuel tank to a separator and separating alcohol from a liquid residue;- combining the residue with a second stream of the feed fuel to produce the main fuel;- directing the separated alcohol (which may be in vapour form) to a reactor and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water;- condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output; and- producing secondary fuel from the ether-concentrated portion of the reactor output.

[0015] Preferably, the process of the variant described above further comprises:- directing the separated unreacted alcohol and water to the first stream of the feed fuel prior to alcohol separation, or directing the separated unreacted alcohol and water to be combined with the reactor output upstream of the condensation step, or directing the separated unreacted alcohol and water to the second stream of the feed fuel, for incorporation as a component of the main fuel. The separated unreacted alcohol and water is typically in the form of a liquid product.

[0016] The above first aspect addresses the fact that the product of the dehydration reaction performed on the alcohol in the reactor comprises water byproduct, in addition to the target ether and unreacted alcohol. If this product is directly delivered to the engine (e.g. a compression ignition engine) for use as a secondary fuel, optionally by way of combination with inlet air directed into intake air of the engine, then there is a potential lack of control on the composition of the secondary fuel (e.g. the concentration of ether, such as dimethyl ether or diethyl ether) going into the engine as secondary fuel. By condensing the reactor output and separating out at least a part of the unreacted alcohol and water, the secondary fuel composition can be better controlled, and can at a minimum be controlled to have a higher ether content than is achieved when using the reactor output directly. This arrangement involving a condensation and separation of a liquid (low-ether content) stream from an ether-concentrated vapour stream, the ether-concentrated vapour stream having a higher ether content than the reactor output, provides better control of the secondary fuel composition and allows for high ether content secondary fuels to be produced prior to delivery to the engine. At the same time, the potential waste byproduct, i.e. the unreacted alcohol / water liquid product, is cleverly integrated into the process through (i) re-use in the return to the first stream of feed fuel, or (ii) for cooling the reactor output stream, or (iii) for incorporation into the main fuel.

[0017] In preferred embodiments, this process is a closed-loop process. That is, there is no waste byproduct that requires disposal, and potential waste streams are integrated into the process, with all liquid outputs being directed into the main fuel and secondary fuel, for use in an engine.

[0018] The process may further comprise directly injecting the main fuel into the engine. The engine is suitably a compression ignition engine. The process may additionally comprise combining the secondary fuel with air and directing the combination into the air intake of an engine, or directly injecting secondary fuel into a cylinder of an engine. In the case of direct injection of secondary fuel into the engine, this is conducted separately to the direct injection of the main fuel.

[0019] In accordance with preferred embodiments, using a simple combination of a condenser to at least partially condense the vapour output of the reactor and then a simple gas / liquid separator to separate an ether-concentrated vapour stream from the liquid condensation product (comprising primarily unreacted alcohol and water), allows for the ether upgrading process to be conducted on-board or in a mobile environment. This simple arrangement is to be distinguished from industrial distillation columns used in high purity chemical production by chemical manufacturing companies comprising an integrated arrangement of components for the repeated vaporisation and condensation of components into purified products (e.g. greater than 98% purity). The compact design afforded by this arrangement makes it possible to conduct the process in a mobile or on-board system. That said, in some alternate operations, such as electricity production from a diesel engine, the same strategies can be used for the production of the two fuel compositions from the feed fuel in a permanent location, without such mobility being required.

[0020] In a preferred form of the first aspect of the present application, the separated unreacted alcohol and water is directed to the first stream of the feed fuel prior to (i.e. upstream of) heating, or upstream of or at alcohol separation from the liquid residue. This feature allows for recovery and re-use of this stream, which can then in other optional embodiments lead to some flexibility in the control of the degree of ether production in the reactor. This feature also allows what might otherwise be considered a waste stream to be conveniently re-combined with input feed material, so that there is no need for accumulation of the waste stream for disposal, which could be problematic in some environments, such as closed-system or mobile environments. Even in fixed location operations, avoiding the need for liquid waste processing is advantageous. Re-directing the waste stream to this location (upstream of heating or upstream of alcohol separation, when alcohol separation is conducted) also has the advantage of enabling the water content of the recycled stream to be used in the control of the reactor (e.g. to reduce the temperature in the reactor, as described further below).

[0021] In an alternative arrangement, the separated unreacted alcohol and water may be directed for combining with the reactor output prior to the condensation step, so as to effect a temperature reduction in the reactor output stream before the condensation step. This use of the unreacted alcohol and water stream in this way provides the advantage of reducing the temperature of the hot reactor output, further supported by recirculation of the (low) liquid ether content in the unreacted alcohol and water stream. Through investigative work detailed further below, it has been determined that the condensed alcohol / water liquid product has a suitable temperature and composition to effect an initial cooling of the reactor output stream prior to further cooling of that reactor output stream in the condenser. This is an effective and energy-efficient use of the separated unreacted alcohol / water liquid stream.

[0022] In a further alternative arrangement, the separated unreacted alcohol and water may be directed to the second stream of the feed fuel, for incorporation as a component of the main fueldelivered to the engine. The directing of the unreacted alcohol and water stream may be via another process stream that is eventually combined with the second stream of the feed fuel, such as a liquid product stream downstream of alcohol separation when the alcohol separation step is performed. If this option is selected, there may need to be an adjustment to the operating conditions for the separation of the unreacted alcohol and water from the ether-concentrated portion. This may involve adjusting the temperature of the separator to better match the temperature of the stream to which the unreacted alcohol and water stream is delivered (such as the liquid product stream, prior to or following cooling of that liquid product stream). Otherwise, a cooler may be used to conduct the cooling of the unreacted alcohol and water stream.

[0023] The system for conducting the process may comprise fluid conduits for one of these selected arrangements, or for two selections of these arrangements. In some embodiments, fluid conduits may be provided for all three of these alternative arrangements. If one suitable arrangement is selected, then the unit has the advantage of simplicity of design, and fewer controls are required, leading to reduced cost. In other arrangements, suitable control systems may be accommodated.

[0024] In some embodiments, alcohol separation is performed to separate evaporated alcohol from a liquid residue, and the separated unreacted alcohol and water is directed to the first stream of the feed fuel prior to alcohol separation. In some embodiments, the separated unreacted alcohol and water is combined with the reactor output prior to the condensation step.

[0025] In addition to performing the condensation of the reactor output and separation of some unreacted alcohol and water (for example, in a flash separator), in some embodiments, two (or more) stages of condensation and separation are performed. The two-stages of condensation and separation enable a high (or selected, controlled) concentration ether product to be produced, which again provides flexibility in the control of the composition of the secondary fuel delivered to the engine. Typically, there will be not more than three stages of condensation and separation, to achieve a sufficient increase in the ether concentration in the ether-concentrated stream while maintaining processing simplicity. In some embodiments there are just one or two stages of condensation and separation for ether concentration upgrading of the reactor output to produce a concentrated ether output with an ether concentration of between 60 wt% and 97 wt%. In some embodiments, there is a single-stage of condensation and separation only.

[0026] The ether content of the reactor output in some embodiments is less than 55 wt% ether prior to the condensation and separation steps. The ether concentration is suitably increased by at least 20%, or at least 40% or at least 60% or at least 70% in the concentration and separation steps. Using the example of a 55 wt% ether reactor output, a 20% concentration increase takes the ether content to 66 wt%.

[0027] In a two-stage process, there is a first stage of partial-condensation, and a second stage of partial-condensation. Such a two-stage process may comprise the following:- in a first partial condensation step, a first partial condensation liquid product comprising alcohol and water and a first percentage of ether is condensed and separated from an ether-concentrated vapour phase, and- in the second partial condensation step (performed on the ether-concentrated vapour phase), a second partial condensation liquid product comprising alcohol, water and a second percentage of ether is condensed and separated from a more concentrated ether vapour phase. The second percentage of ether is higher than the first percentage of ether.

[0028] In the above two-stage process, each "partial condensation step" is typically conducted in a sequence of a partial condenser followed by a separator.

[0029] Conducting this staged concentrating of the ether product using simple componentry and without the use of a distillation column is a clever arrangement that enables on-board or mobile processing of the feed fuel to produce the two fuel parts in close proximity to the subject engine being fueled by the two fuel parts. This combination enables the production of a concentrated ether product with an ether content that is sufficiently high to meet the demands of the fumigation and pilot ignition to run the compression ignition engine on the main fuel, while avoiding the use of an industrial distillation column as used in industrial scale chemical production.

[0030] In one optional embodiment of that two-stage partial condensation process, the second partial condensation liquid product may be combined with the reactor output prior to said first partial condensation step. Then the first partial condensation step can be performed on the combination of the reactor output and the second partial condensation liquid product. In another option, the second partial condensation liquid product may be combined with the partially condensed stream exiting the first stage partial condenser.

[0031] The above-described arrangement involving a single or staged increase of the ether content of the reactor output provides a novel way of producing a high purity or targeted purity DME stream. This arrangement also allows for the separated streams to be re-used in a closed-system arrangement, without the need for waste product accumulation and removal.

[0032] It was found that by mixing the second partial condensation liquid product (ether flash bottoms) with the (hot) reactor output from the reactor in some embodiments, it was possible to produce a high-quality ether (e.g. dimethyl ether or diethyl ether).

[0033] In preferred embodiments, the process comprises:- superheating the vaporised alcohol, prior to directing the superheated vaporised alcohol to the reactor.

[0034] In some operations, the feed fuel subjected to the process of the first aspect comprises between 0 and 30% by weight water, and at least 50 ppm (on a weight basis) of a lubricity improver in addition to the alcohol. In the separation step, the lubricity improver separates into the liquid residue.This pre-processing of the first stream of the feed fuel prior to entry into the reactor ensures that the reactor is protected from potential fouling caused by any lubricity improver (and / or other additives or impurities). The liquid residue separated from the evaporated alcohol may then be combined with the second stream of the feed fuel for the preparation of the main fuel. In this embodiment, there is also the option to make use of engine exhaust heat to heat that feed fuel to perform the initial separation. This is described in further detail below with reference to the second aspect of the present application.

[0035] In a second aspect, there is provided a process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel, the process comprising:- storing a feed fuel in a feed fuel tank, the feed fuel comprising an alcohol, between 0 and 30% by weight water, and at least 50 ppm (on a weight basis) of a lubricity improver;- directing a first stream of the feed fuel to a heater for heating of the first stream of the feed fuel, evaporating alcohol from the first stream of feed fuel and separating a residue therefrom, the residue comprising lubricity improver;- directing the alcohol separated from the residue to a reactor, catalytically converting the alcohol to an ether, and producing the secondary fuel from the ether;- combining the residue separated from the evaporated alcohol with a second stream of the feed fuel to produce the main fuel;- directing the main fuel to an engine for fueling the engine; and- directing the secondary fuel to an engine separately to the main fuel.

[0036] In a preferred embodiment thereof, the process further comprises:- using heat from an engine exhaust for said heating of the first stream of feed fuel.

[0037] In this second aspect, the process accommodates the use of a mixed-component single feed fuel comprising an alcohol such as methanol, optionally water, and a lubricity improver (i.e. an alcohol fuel lubricity improver). The feed fuel may suitably comprise additional components as described in further detail below. Rather than directing the entire feed fuel composition into a reactor for catalytically converting the alcohol to an ether, which may create challenges for the catalytic conversion process (e.g. catalyst degradation), the lubricity improver is separated from the alcohol, and the separated residue combined with a second stream of the feed fuel to produce the main fuel with a higher content of the lubricity improver as compared to the feed fuel. It is the separated alcohol stream that is substantially free of lubricity improver (the alcohol stream optionally comprising additional alcohol and water from a recycle stream as described in further detail below), that is directed to the reactor. The separation of alcohol is achieved in this embodiment in a two-stage process, the two stages including heating the feed fuel in a heater, to evaporate or vaporise the alcohol into the gas phase, and then separating the alcohol from a liquid residue comprising the lubricity improver (e.g. in a flash separator). Heat requirements for the heater may in preferred embodiments be provided in part or entirely by engine exhaust. This combination of features allows for an optimum manner of achieving the required separation of lubricityimprover (and any other high boiling point materials present in the feed fuel), and use of a heating resource to effect the required heating to achieve the separation. Using flash separation as the means of evaporating the alcohol and substantially separating the higher boiling point components also provides a useful way to conduct a purity improvement in the alcohol stream, without the use of a distillation system or distillation column. This is significant when on-board or mobile production of ether from alcohol is required.

[0038] As described in further detail below, the engine exhaust heat exchange may be via any suitable medium, such as an oil heater circulation loop. The oil heater may be used to effect exchange of heat into an oil medium or equivalent, and then that medium passed through the heater to exchange heat from the medium into the feed fuel.

[0039] The present application further provides in a third aspect a process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel using a catalyst, the process comprising:- storing a feed fuel comprising alcohol in a feed fuel tank;- vaporising alcohol in a first stream of the feed fuel from the feed fuel tank;- directing the vaporised alcohol to a reactor comprising the catalyst and catalytically converting the alcohol to an ether and a water byproduct;- storing the ether in an ether storage tank;- flushing the reactor with ether from the ether storage tank to flush water byproduct from the reactor; - producing main fuel from a second stream of the feed fuel, and- producing secondary fuel from the ether produced in the reactor.

[0040] In this third aspect, the flushing of the reactor with ether is performed when required, to flush water byproduct from the reactor, to protect the catalyst from the impact of extended water contact when the reactor is not in operation, and / or to protect the catalyst from the impact of water condensation and / or freezing when the catalyst is cooled down.

[0041] The flushing is performed periodically. This may be performed, for example, at (or during) shut-down of the reactor. Typically, during shut-down of the reactor, the flow of alcohol is discontinued. When ether flushing is performed at shut-down, ether is flushed through the reactor after the flow of alcohol is discontinued. The flow of ether through the reactor may be conducted while the reactor remains at an elevated temperature. After ether flushing has taken place to flush water from the reactor, the reactor is shut down.

[0042] In some operations, the process of the third aspect may be combined with one or both of the processes of the first and second aspects. However, this is not always necessary, depending on the objectives and challenges faced in performing a particular process. When combining with the second aspect, the step of vaporising the alcohol may comprise heating the first stream of the feed fuel from the feed fuel tank to vaporise the alcohol and directing the heated first stream of the feed fuel to a separatorto separate the vaporised alcohol from a liquid residue. Thereafter the liquid residue may be combined with the second stream of the feed fuel to produce the main fuel. Where the feed fuel comprises a lubricity improver, this allows the lubricity improver component to be directed to the feed fuel rather than to the reactor comprising the catalyst as an additional means for protecting the catalyst from the impact of the lubricity improver. Additional details of processes making use of combinations of these aspects are described below.

[0043] In a fourth aspect, there is provided an alternative approach for producing two fuel compositions from a feed fuel using a catalyst, while protecting that catalyst from early deterioration. In the fourth aspect, there is provided a process for producing two fuel compositions including a main fuel and a secondary fuel, from a feed fuel using a catalyst, the process comprising:- storing the feed fuel in a feed fuel tank, the feed fuel comprising alcohol;- directing a first stream of the feed fuel to a heater for heating of the first stream of the feed fuel and evaporating alcohol in the first stream of feed fuel;- producing the main fuel from a second stream of the feed fuel;- directing the evaporated alcohol to a reactor comprising the catalyst and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water;- producing secondary fuel from the ether produced in the reactor;- receiving data indicative of an unacceptable temperature in the reactor; and- performing one or more of the following steps, based on the data, to return the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing temperature of feed material fed into the reactor, said feed material comprising the alcohol evaporated in the first stream of feed fuel;- changing the residence time of the feed material fed into the reactor; and- increasing the water content of the feed material fed into the reactor.

[0044] The fourth aspect provides a range of options for controlling the temperature within the reactor so as to preserve catalyst integrity.

[0045] Varying the flow rate of alcohol through the reactor may be by way of increasing the flow rate of alcohol through the reactor. The catalytic conversion from alcohol to ether is exothermic. If the flow rate is increased, there is shorter residence time for alcohol in the reactor, and therefore lower conversion to ether, and results in a drop in temperature in the reactor.

[0046] Changing the temperature of the feed material fed into the reactor may suitably involve reducing the temperature of the feed material fed into the reactor. This impacts on the extent of conversion from alcohol to ether. For an exothermic alcohol dehydration reaction, a lowering of the input temperature of the feed material fed into the reactor results in a lowering of conversion (of alcohol toether), requiring adjustment by way of an increase in the reactor feed rate (i.e. alcohol feed rate into the reactor). The feed rate (of alcohol going into the reactor, as distinct from total volume of feed material going into the reactor) is increased when the input temperature is decreased, to offset the reduced conversion of alcohol to ether. This adjustment maintains the targeted ether production while leaving a greater volume of unreacted alcohol in the reactor output. The reactor output with a higher wt% amount of unreacted alcohol, in some embodiments, is returned upstream of the reactor to become part of the reactor input. In the detailed description below, an example is provided to demonstrate this.

[0047] Changing the residence time that the feed material remains in the reactor also has an impact on the temperature within the reactor. The residence time on a mass basis refers to: (mass of catalyst in kg) / (flow through the catalyst bed in kg / second) - with an overall unit of measurement being in "seconds". The residence time also has an impact on the reactor temperature in the reaction space, and can be controlled to reduce the temperature in that space. While residence time is one factor that can be adjusted, in preferred embodiments, it is one or more of the other factors (flow rate, temperature and water content) that is changed to reduce the temperature in the reaction space.

[0048] In some embodiments, the step of heating the feed fuel in a heater and evaporating alcohol from the first stream of the feed fuel comprises an initial heating step in the heater to evaporate the alcohol, and then separating a liquid residue from the evaporated alcohol in a separator. That liquid residue in preferred embodiments is combined with the second stream of the feed fuel to produce the main fuel. Water may be present in the feed material fed into the reactor (i.e. the evaporated alcohol stream, particularly where there is water present in the composition subjected to alcohol evaporation.) In addition, in many embodiments, there is water generated in the catalytic reaction, and water is separated and may be returned to the stream circulating that finds its way to the reactor. For example, water may be separated from the reactor output (with unreacted alcohol), and returned to the first stream of feed fuel. Alternatively, water is present in the fuel feed. In the alcohol separation step of the process, while a significant proportion of any water component in the material subjected to the heating and separation steps will report to the liquid residue, there is some water co-evaporated with the separated alcohol that then passes through with the alcohol to the reactor. By increasing the water content of the separated alcohol stream in the alcohol separation step, for example, by changing the settings (e.g. temperature) of the alcohol separation unit, a higher proportion of water may be fed into the reactor, with a consequent impact on the reactor temperature. This provides an additional unique means of controlling the reactor temperature.

[0049] In the process of any of the above-described aspects, the reactor may comprise a single reactor, or the reactor may comprise a series of at least two reactors, including a first reactor and a second reactor. Catalytic conversion of alcohol to an ether takes place progressively through each reactor in series.

[0050] Where there is a series of at least two reactors in series, the process of the fourth aspect may comprise one or more of the following steps to return the temperature in the reactor to be within an acceptable range:- varying the flow rate of alcohol through each of the reactors;- changing the temperature of feed material fed into the first reactor in the series;- changing the total residence time of the feed material fed through the reactors; and- increasing the water content of the feed material fed into the first reactor.

[0051] The changing of the residence time of the feed material fed into the reactor may in this case comprise changing the total residence time of feed material fed through the series of reactors. This may involve selectively by-passing one or more reactors or reactor beds to shorten the overall residence time.

[0052] As noted above, in any of the first to fourth aspects, the reactor may comprise a series of at least two reactors, including a first reactor and a second reactor, and catalytic conversion of alcohol to an ether takes place progressively through each reactor in the series. In some embodiments, a residence time of fluid fed through each reactor in the series of reactors increases from one reactor to the following reactor in the series. In some embodiments, an intercooler is positioned between two sequential reactors in the series, and the process comprises intercooling between the sequential reactors.

[0053] The feed fuel used in the process of any of the above aspects is described in detail below. In broad terms, the feed fuel may comprise said alcohol, between 0 and 30% by weight water, and optionally at least 50ppm (on a weight basis - and preferably at least 100ppm) of a lubricity improver.

[0054] The present application further provides, in a fifth aspect, a new use of a feed fuel comprising (a) alcohol, (b) between 0 and 30% by weight water and (c) at least 50 ppm (on a weight basis) of a lubricity improver, to produce two fuel compositions including a main fuel comprising alcohol and lubricity improver, and a secondary fuel comprising ether, wherein the two fuel compositions are produced from the feed fuel by:- heating a first stream of the feed fuel and evaporating alcohol in the first stream of feed fuel,- separating a residue from the evaporated alcohol, the residue comprising lubricity improver;- directing the alcohol separated from the residue to a reactor and catalytically converting the alcohol to an ether and water in the reactor, wherein the reactor output comprises unreacted alcohol in addition to said ether and water;- producing the secondary fuel from the ether produced in the reactor; and- combining the residue separated from the evaporated alcohol with a second stream of the feed fuel to produce the main fuel.

[0055] Preferred details of the feed fuel composition are set out below. In brief, the feed fuel preferably comprises methanol or ethanol as the alcohol. The feed fuel preferably comprises at least 0.2% by weight water. The feed fuel may further comprise at least 10ppm corrosion inhibitor and / or a flame colour additive. In the case of corrosion inhibitor and / or flame colour additive, these are separated intothe residue separated from the alcohol, in addition to the lubricity improver. In some embodiments, the feed fuel comprises one or more high-boiling point materials with a boiling point higher than 100°C, other than the lubricity improver, and the high-boiling point materials are separated into the residue with the lubricity improver to be separated from the alcohol in the separation step. As examples, the high-boiling point materials are selected from a corrosion inhibitor and a feed fuel colour additive. The feed fuel may also comprise one or more impurities selected from the group consisting of acetone, an alcohol other than methanol and ethanol, sulphur and inorganic matter. Additional optional components of the feed fuel are also described below.

[0056] In a sixth aspect, the present application provides for the use of a feed fuel comprising alcohol, between 0 and 30% by weight water and at least 50ppm (preferably 100ppm) (on a weight basis) of a lubricity improver, to produce two fuel compositions including a main fuel comprising alcohol and lubricity improver and a secondary fuel comprising ether, wherein the two fuel compositions are produced from the feed fuel by:- heating a first stream of the feed fuel and evaporating alcohol in the first stream of feed fuel;- separating a residue from the evaporated alcohol, the residue comprising lubricity improver;- directing the alcohol separated from the residue to a reactor, and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water;- condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output;- combining the residue separated from the evaporated alcohol with a second stream of the feed fuel to produce the main fuel; and- producing secondary fuel from the ether-concentrated portion of the reactor output.

[0057] In seventh, eighth, ninth and tenth aspects of the present application there are provided systems suitable for performing the processes of the first to fourth aspects described above, respectively. These systems are set out below.

[0058] In a seventh aspect, there is provided a system for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel comprising alcohol, the system comprising:- a feed fuel tank;- a first feed fuel pump fluidically connected to the feed fuel tank configured to pump a first stream of the feed fuel from the feed fuel tank to a heater;- a second feed fuel pump fluidically connected to the feed fuel tank configured to pump a second stream of the feed fuel through a conduit along which main fuel can produced from the feed fuel;- the heater configured to receive the first stream of the feed fuel from the feed fuel tank, and configured to heat the feed fuel to enable evaporation of alcohol in the feed fuel;- optionally an alcohol separator configured to receive the feed fuel heated in the heater, the alcohol separator configured to separate evaporated alcohol from a liquid residue;- a reactor configured to receive the evaporated alcohol and to catalytically convert the evaporated alcohol to an ether and water, the reactor output comprising unreacted alcohol in addition to said ether and water;- a condenser configured to receive the reactor output and at least partially condense the reactor output; - a water separator configured to receive the at least partially condensed reactor output, the separator configured to separate a liquid product comprising at least a portion of the unreacted alcohol and water from the reactor output, and an ether-concentrated portion of the reactor output;- a secondary fuel tank in fluid communication with the water separator, for storing secondary fuel comprising ether from the ether-concentrated portion of the reactor output; and- a liquid product pump configured to pump the liquid product comprising at least a portion of the unreacted alcohol and water from the water separator for combining with at least one of:(i) the first stream of the feed fuel, upstream of the heater, or upstream of, or at, the alcohol separator;(ii) the reactor output upstream of the condenser; and(iii) the second stream of the feed fuel, for producing the main fuel from the combination of the feed fuel and the liquid product.

[0059] In a preferred variant of the seventh aspect, the system further comprises:- a main fuel pump configured to pump main fuel to the engine.

[0060] In one embodiment, the system comprises the alcohol separator, and further comprises: - a residue pump configured to pump a liquid residue separated from the evaporated alcohol in the alcohol separator for combination with the second stream of the feed fuel, enabling a main fuel to be produced from a combination of the feed fuel and the residue.

[0061] In one embodiment of the seventh aspect, the liquid product pump is configured to pump the liquid product for (i) combining with the first stream of the feed fuel prior to delivery of the first stream of the feed fuel to the heater.

[0062] In an eighth aspect, there is provided a system for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel, the system comprising:- a feed fuel tank for storing a feed fuel comprising an alcohol, between 0 and 30% by weight water, and at least 50ppm (on a weight basis) (e.g. at least 100ppm) of a lubricity improver;- a first feed fuel pump fluidically connected to the feed fuel tank configured to pump a first stream of the feed fuel from the feed fuel tank to a heater;- a second feed fuel pump fluidically connected to the feed fuel tank configured to pump a second stream of the feed fuel from the feed fuel tank towards an engine;- the heater that receives the first stream of the feed fuel from the feed fuel tank, the heater configured to heat the feed fuel to enable evaporation of alcohol in the feed fuel;- an alcohol separator that receives the feed fuel heated in the heater, the separator configured to separate alcohol in the first stream of feed fuel from a liquid residue comprising lubricity improver; - a reactor that receives the evaporated alcohol separated by the alcohol separator, the reactor configured to catalytically convert the alcohol to an ether and water, from which the secondary fuel is produced;- a secondary fuel tank in fluid communication with the reactor, for storing secondary fuel comprising ether produced in the reactor, wherein the secondary fuel tank is in fluid communication with an engine for the delivery of the secondary fuel to the engine;- a residue pump configured to pump the liquid residue separated from the evaporated alcohol in the separator for combination with the second stream of the feed fuel, enabling the production of the main fuel from a combination of the feed fuel and the residue.

[0063] In a preferred variant, the system may further comprise:- a main fuel pump configured to pump main fuel to the engine.

[0064] In a ninth aspect, there is provided a system for protecting a catalyst used to produce a secondary fuel composition from a feed fuel, the system comprising:- a feed fuel tank;- a first feed fuel pump fluidically connected to the feed fuel tank configured to pump a first stream of the feed fuel from the feed fuel tank to a heater;- the heater that receives the first stream of the feed fuel from the feed fuel tank, the heater configured to heat the feed fuel to enable evaporation of alcohol in the feed fuel;- an optional alcohol separator that receives the feed fuel heated in the heater, the alcohol separator configured to separate evaporated alcohol from a liquid residue;- a reactor that receives the evaporated alcohol, the reactor comprising a reactor space where the alcohol comes into contact with the catalyst, the reactor configured to catalytically convert the alcohol to an ether and a water byproduct,- a secondary fuel tank in fluid communication with the reactor, for storing secondary fuel comprising ether produced in the reactor; and- an ether flushing conduit in fluid communication with the secondary fuel tank, the ether flushing conduit configured to allow ether to be conveyed from the secondary fuel tank, through the reactor, to flush the reactor space with ether.

[0065] In some embodiments, the system further comprises:- conduits for combining a liquid residue separated from the alcohol in the alcohol evaporator with a second stream of feed fuel from the feed fuel tank to produce a main fuel from a combination of the feed fuel and the liquid residue.

[0066] In a tenth aspect, there is provided a system for controlling the temperature in a reactor used to produce a secondary fuel from a feed fuel, the system comprising:- a feed fuel tank;- a first feed fuel pump fluidically connected to the feed fuel tank configured to pump a first stream of the feed fuel from the feed fuel tank to a heater;- the heater that receives the first stream of the feed fuel from the feed fuel tank, the heater configured to heat the feed fuel to enable evaporation of alcohol in the feed fuel;- an optional alcohol separator that receives the feed fuel heated in the heater, the alcohol separator configured to separate evaporated alcohol from a liquid residue;- a reactor that receives the evaporated alcohol, the reactor comprising a reactor space where the alcohol comes into contact with a catalyst, the reactor configured to catalytically convert the alcohol to an ether and a water byproduct,- a secondary fuel tank in fluid communication with the reactor, for storing secondary fuel comprising ether produced in the reactor; and- a reactor temperature control unit structured to:- receive data indicative of an unacceptable temperature in the reactor; and- perform one or more of the following steps, based on the data, to return the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing temperature of feed material fed into the reactor, said feed material comprising the evaporated alcohol;- changing the residence time of the feed material fed into the reactor; and- increasing the water content of the feed material fed into the reactor.

[0067] In the seventh to tenth aspects described above, it should be noted that the term "fluidically" is interchangeable with the term "fluidly".

[0068] In each of the seventh to tenth aspects, the system preferably further comprises:- a superheater, for superheating the evaporated alcohol prior to delivery of the superheated evaporated alcohol to the reactor.

[0069] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

[0070] The reference to any prior art in this specification is not and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

[0071] The term "comprising" is interpreted in the inclusive sense, to require the presence of the stated feature or steps, with the optional inclusion of other features or steps. However, where acomposition or process is said to be "free" of a particular feature or step, then such features or steps are specifically excluded.

[0072] References to "a", "an" or "the" feature should be understood to extend to plural of such features, unless the context indicates otherwise. As one example, references to the production of "an ether" from "an alcohol" extends to the production of more than one type of ether from more than one type of alcohol.BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Selected embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0074] Figure 1 is a schematic diagram of the process and system for the production of two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel, in accordance with one embodiment incorporating features of multiple aspects.

[0075] Figure 2 is a schematic diagram of a more simplified version of the process and system for the production of two fuel compositions from a feed fuel in accordance with a second embodiment of the invention.

[0076] Figure 3 is graph of load (y-axis), measured in N-m, vs. engine crankshaft rpm (x-axis) - this co-ordinate system referred to as the engine map. This graph also forms the basis of a power vs. rpm plot. The plotted parameter is the percentage on a mass basis of the proportion of DME in the total mass entering the engine. That is, (DME) / (DME + main fuel + combustion air) x 100%. Note that in this case, the DME represents the secondary fuel.

[0077] Figure 4 is a schematic diagram of a third embodiment of the process and system for the production of two fuel compositions from a feed fuel, which is a variation of the first embodiment shown in Figure 1.DETAILED DESCRIPTION

[0078] A number of terms used in the specification are defined below, to provide clarity on the meaning of those terms.

[0079] The term "fuel" refers to any combustible or energy-providing substance suitable for use in an internal combustion engine to produce power. The class of fuels that are the subject of the present application are alcohol-based fuels (also referred to as "alcohol fuels"), which contain alcohol as one of the fuel components. The fuels are more specifically compression ignition engine fuels. The fuels may be classified as "diesel replacement fuels". As used herein, "feed fuel" refers to the fuel composition delivered to a fuel tank for subsequent conversion into the two fuels to be supplied to an engine, "main fuel" refers to the primary fuel source delivered into the engine for combustion within the engine, typically via direct injection, and "secondary fuel" refers to an auxiliary fuel component, of a differentcomposition to the "main fuel", introduced into the engine. The "secondary fuel" may be injected into the intake air stream, or may be direct-injected (separately to the main fuel).

[0080] The term "alcohol" refers to an organic compound comprising at least one hydroxyl (-OH) functional group bonded to a saturated carbon atom. An alcohol may be a primary, secondary, or tertiary alcohol. Prime examples are the C1-C8 aliphatic alcohols, such as the C1-C4 aliphatic alcohols, which may be straight-chained or branched, and preferably straight-chained. Preferred alcohols in the context of the fuel comprising alcohol are methanol and ethanol. Further discussion of the fuel composition, including alcohol content and the content of other optional components, is set out further below in the context of the preferred embodiments.

[0081] The term "storing" in the context of the storing of a feed fuel in a fuel tank is used in the conventional sense as referring to retaining the fuel in the fuel tank for any duration (temporary or extended) prior to its intended use or transfer elsewhere. The term "tank" refers to any container vessel or enclosed structure designed or adapted to hold the indicated substance, such as the fuel.

[0082] The terms "vaporising" and "evaporating" refer to the physical process by which a liquid substance, such as an alcohol, is converted into its gaseous phase (also referred to a vapour phase). This transition occurs when molecules of the liquid gain sufficient energy to overcome intermolecular forces and enter the vapour state. The process may occur through the application of heat, reduction of pressure, or exposure to other conditions that facilitate the phase change. The process may be partial or complete. In some examples, the vaporised component, such as alcohol, is subjected to a subsequent operation such as being directed to a reactor, optionally via any other processing stage, such as a superheater. It will be understood that the vaporised or evaporated product (e.g. "vaporised alcohol") may contain additional vaporised components (e.g. water), and that a portion of the material subjected to vaporisation may remain in liquid form. The vaporised alcohol stream is typically of a high alcohol content, such as at least 90% or at least 95% or higher alcohol content. The terms "vaporised alcohol" and "evaporated alcohol" are used interchangeably. The terms are also used interchangeably with "separated alcohol", particularly where the vaporisation of the alcohol has facilitated the separation of alcohol from other components. It should be noted that a "separated alcohol" may nevertheless contain a lower content of those components from which it has been substantially separated. The extent of separation required to meet a “substantial" extent of separation is dependent on the context and the component involved, in the context of lubricity improver removal from a separated alcohol stream conducted in the alcohol separator, "substantially" means at least 95 wt% or at least 99 wt% removal of the lubricity improver from the separated alcohol stream. In the context of water, the extent of separation may be a significant reduction. In one example, for a 20 wt% water content of the total composition entering the alcohol separator, the water content of the separated alcohol stream may be in the vicinity of 10 wt%.

[0083] The term "stream" refers to a flow of fluid, such as liquid, vapor, or a mixture thereof, moving from one location to another (e.g. within a system or apparatus). The stream may be conveyed through a conduit, passage, or other flow path, and may be continuous or intermittent. The term "conduit" is used in the conventional sense, and extends to any passageway or flow path through which a fluid passes in a controlled manner from one location to another.

[0084] The term "reactor" refers to a vessel, chamber, or apparatus configured to facilitate a chemical reaction under controlled conditions of temperature, pressure, and flow. In the context of the present specification, the reactor is adapted to receive vaporised alcohol and catalytically convert at least a portion of the alcohol to an ether and water.

[0085] The term "ether" refers to an organic compound comprising an oxygen atom bonded to two alkyl groups. The alkyl groups may be C1-C8 alkyl groups, or C1-C4 alkyl groups. Each alkyl group may be the same or different. In preferred embodiments, the ether is formed by catalytic conversion of the corresponding alcohol. Notable ethers in the present context are dimethyl ether when methanol is used as the alcohol, methyl ethyl ether, and diethyl ether.

[0086] The term "alkyl" refers to a saturated hydrocarbon group consisting of carbon and hydrogen atoms arranged in a straight or branched chain. The C1-C4 alkyls are methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, isobutyl, and tert-butyl.

[0087] The term "reactor output" refers to the fluid composition discharged from the reactor following catalytic conversion. The reactor output comprises ether, water, and unreacted alcohol.

[0088] The term "condenser" refers to an apparatus configured to cool a vapour stream and convert at least a portion of the vapour into liquid phase. Condensation may be partial or complete. A partial condenser is a condenser configured to effect at least partial condensation. Partial condensation facilitates a subsequent separation of a liquid product (which may in some embodiments comprise unreacted alcohol and water) from a vapour (e.g. an ether-concentrated vapor).

[0089] As used herein, the term "liquid product" refers to a product, or composition, in the liquid phase. The term "product" is used simply to distinguish from other liquid streams, such as a "liquid residue", which arises in a different part of the process.

[0090] The term "liquid residue" refers to a residual component, which is in the liquid phase. " Residue" indicates a remainder after the removal of a component, or a reduction in the amount of one or more components (e.g. a reduced alcohol content after removal of at least a part of the alcohol content, by way of flash evaporation or otherwise).

[0091] The term "ether-concentrated vapour" refers to a vapour containing a higher concentration of ether relative to the preceding stream from which it was derived - such as the reactor output. The "ether-concentrated vapor" may contain some alcohol and water vapor, at a lowerconcentration than the preceding stream (e.g. a reduced alcohol and water content as compared to the reactor output).

[0092] The expression "producing secondary fuel from the ether" (or "from the reactor output") is used broadly to encompass the direct use of that ether or reactor output (comprising) ether, or the performance of additional operations on the ether-containing stream (or reactor output) prior to using that further processed stream or a component thereof (or a blend of that stream with another stream) as a secondary fuel. Similarly, references to the production of a main fuel from a stream of feed fuel encompasses the use of the feed fuel directly for that purpose, or following the addition of further process streams or components, such as a liquid product stream, or the performance of any other operation on that stream.

[0093] The term "directing" refers to causing or controlling the movement of a fluid stream from one location to another (e.g. within a process, system or apparatus). This may include guiding, channeling, or conveying the stream through a conduit, passage, or other flow path, and may involve pumps, valves, or other flow-control mechanisms. " Directing" encompasses any action or arrangement that results in the intended transfer of a stream between process steps. The phrase "prior to" refers to an action or step occurring upstream or at another specified action or step in the process sequence, without necessarily requiring immediate succession. " Upstream" is used in the same sense." Downstream" refers to an action or step occurring following or downstream of another specified action or step in the process sequence or flow path, without requiring immediate succession. The phrase "for incorporation as a component" refers to introducing or combining a substance or stream into another composition such that it becomes part of the resulting mixture or formulation, whether as a major or minor constituent.

[0094] The term "compression ignition engine" refers to an internal combustion engine in which ignition of the fuel-air mixture occurs primarily due to the heat generated by compressing air within the combustion chamber, rather than by a spark. In such engines, fuel is typically injected (or "direct injected") into highly compressed, hot air, causing combustion after a small ignition delay. Compression ignition engines are sometimes referred to as "diesel engines", as diesel fuel is a grade of petrochemical fuel that is commonly used as the fuel for such engines. Diesel fuel refers to a hydrocarbon-based fuel composition suitable for use in compression ignition engines, typically comprising a mixture of hydrocarbons derived from petroleum or alternative sources, with a boiling range generally between about 180 °C and 400 °C. Diesel fuel may include conventional petroleum diesel, biodiesel (fatty acid methyl esters), synthetic diesel, or blends thereof. Where the present-described two-part fuel is said to be a "complete replacement" for diesel fuel, this means that conventional petroleum diesel is completely replaced by the two-part fuel, and conventional petroleum diesel is not used either as the main fuel or as a pilot fuel (secondary fuel).

[0095] As used herein, a "lubricity improver" is a fuel-soluble additive (or additive package) that, when incorporated at an effective treat rate into the relevant fuel (i.e. the feed fuel or main fuel), improves the fuel's boundary lubrication characteristics within the fuel supply system of an internal combustion engine. An improvement in the fuel's lubrication characteristics is evidenced by a reduction in wear scar diameter, tested under standard lubricity test conditions (i.e. a HFRR or High-Frequency Reciprocating Rig test). A suitable HFRR test for testing lubricity of a fuel treated with a lubricity improver additive is provided in IP PM FK / 24, as published by the Energy Institute (see https: / / www.energyinst.org / technical / publications / topics / ip-test-methods / ip-pm-fk-methanol-fuel-assessment-of-lubricity-using-the-high-frequency-reciprocating-rig-hfrr). An improvement of the fuel lubricity (tested without and with the additive, for comparison purposes) may be determined by reference to a % improvement in the wear scar diameter measured in the HFRR test, under the same conditions. The improvement should be a minimum of a 20% improvement (reduced wear scar). A test amount for the lubricity improver in the fuel composition should be the treat rate proposed for inclusion in the fuel (or actually included in the fuel) - or if a reference point is required, the lubricity improver additive level should be tested at 1000ppm. In the context of on-road diesel fuels, a wear scar diameter for a suitably lubricated diesel fuel should be below 460μm at 60°C. Test work indicates that for methanol and methanol-water based fuels (with a minimum total water and methanol content of >95%, and a water content between 0 and 25%), the wear scar diameter for the fuel without a lubricity improver additive is between about 410 μm and 680 μm (as measured under IP PM FK / 24 at 25°C). Where the methanol or methanol-water fuel (>95% total MeOH + H2O, 0-25% water) contains an additive that reduces the wear scar diameter under the same test conditions to below 242 μm, it is to be taken as inherent that the fuel contains lubricity improver additive at a minimum 50ppm level. It should be noted that additives that are "lubricity improvers" for different fuel classes, such as diesel fuel lubricity improvers and petroleum fuel lubricity improvers, do not necessarily provide lubricity improvement for alcohol-based fuels (and alcohol-water blend fuels). Unlike diesel and petroleum fuels, which are relatively hydrophobic and readily solvate nonpolar lubricity agents, alcohol-based fuels are highly polar and hygroscopic, so they require lubricity improvers with stronger polar functionality and alcohol miscibility— such as fatty-acids, fatty acid esters or diethanolamine derivatives— rather than the predominantly hydrocarbon-based additives suited to diesel. To test for solubility / miscibility of the lubricity improver in the alcohol-based fuel (i.e. to test whether the lubricity improver is fuel-soluble), a "clear and bright" test is used. The 'clear and bright' test refers to visually inspecting a fuel sample after addition of the lubricity improver at the proposed treat rate (or at 1000ppm if no specific treat rate is specified); if the mixture remains transparent and free of haze or phase separation, the additive is considered soluble and miscible in the alcohol-based fuel. A suitable 'clear and bright' test is set out in ASTM D4176. The test temperature for meeting the solubility requirement should be measured at 0°C. Traditional diesel fuel lubricity improvers will tend to fail the "clear and bright" test in an alcohol-basedfuel. Castor oil is one such example of a diesel fuel lubricity improver that does not meet the requirements of a "lubricity improver" (specifically, an alcohol-based fuel lubricity improver") as defined herein.

[0096] The term "organic" in the context of "organic lubricity improvers" refers to lubricity improvers that are organic compound-based, as distinct from inorganic (e.g. metal salts or chlorides). An organic compound contains carbon atoms covalently bonded to hydrogen atoms, and also optionally to other elements (e.g. oxygen).

[0097] The term "fatty acid" refers to a C8-C24 hydrocarbon chain, which may be saturated or unsaturated (mono- or poly- unsaturated), with a single carboxylic acid (-CO2H) end. Fatty acids with a single carboxylic acid group may be referred to as mono-carboxylic acids. The hydrocarbon chain may be branched or unbranched, but is preferably unbranched. Notable examples include oleic acid, linoleic acid, palmitic acid and linolenic acid.

[0098] The term "fatty acid ester" refers to a compound formed by the esterification of a fatty acid with an alcohol. The fatty acid component typically contains a C8-C24 hydrocarbon chain, which may be saturated or unsaturated, with a single carboxylic acid end, which is esterified with an alcohol component, where the alcohol component is a mono-, di-, or polyhydric alcohol. The alcohol component in the context of the fatty acid ester may be aliphatic or aromatic. The ester may be straight-chain or branched. Examples include alkyl esters, glycerol esters, and complex esters.

[0099] " Diethanolamine and derivatives thereof" refers to diethanolamine (DEA), a compound having the formula HN(CH2CH2OH)2, and any chemical species derived from it by substitution, addition, or modification of one or more functional groups. Such derivatives include alkylated or aryl-substituted diethanolamines, esterified forms resulting from reaction of one or both hydroxyl groups with carboxylic acids (alky groups with -CO2H substitution) or their functional equivalents (-CO2-alkyl), ether derivatives formed by reaction of hydroxyl groups with alkyl or aryl halides or epoxides, salts including protonated or quaternized forms, and other modified structures that retain the core diethanolamine backbone. Suitable diethanolamines and derivatives thereof have lubricity improving properties for alcohol-based fuels.

[0100] " Fluorosurfactant" refers to a surface-active compound containing one or more fluorinated alkyl or aryl groups covalently bonded to a hydrophilic moiety, such as an anionic, cationic, nonionic, or amphoteric functional group. These compounds exhibit strong interfacial activity due to the presence of fluorine atoms, which impart low surface energy and chemical stability. Suitable fluorosurfactants function as lubricity improvers in alcohol-based fuel compositions by reducing friction and wear between contacting surfaces.

[0101] The term "renewable material" refers to a material or substance that can be replenished through natural processes and can be used without depletion of resources. Biochemicals, extracted from plants, are renewable. Biomaterials producible from organic matter that can be re-grown or re-produced through natural processes are also examples of renewable materials. Chemicals produced from non-renewable resources, such as coal, natural gas and oil are not renewable, as those resources are finite. Similar expressions such as "renewably sourced" or "renewable resource" should be interpreted correspondingly.

[0102] The term "corrosion inhibitor" refers to a material that inhibits corrosion on the surfaces within the fuel supply system of an engine. Suitable corrosion inhibitors in the present context are materials that are soluble or miscible in the alcohol-based fuel, and meet the "clear and bright" test.

[0103] A "stable" fuel composition is one that remains clear and bright after testing for 28 days at 0°C. The clear and bright test is as outlined above in the context of the lubricity improver definition. A fuel that is "stable under the environmental temperature conditions at which the fuel is used" is a fuel that meets the clear and bright test after testing for 28 days at the relevant environmental temperature. This may be a temperature of -20°C for low temperature environments. This may be a temperature of +30°C for high temperature environments.

[0104] A "significant" amount refers to an amount that is significant - and more than incidental or trifling. In the context of a fuel that contains a "significant" water content, this refers to an amount greater than an impurity level amount. In some embodiments, a "significant" water (in a fuel composition) content is at least 0.5wt%, or at least lwt%, or at least 2 wt% or at least 3 wt%.

[0105] " Catalytic conversion" refers to a chemical process in which one or more reactants are transformed into different chemical species through the action of a catalyst, wherein the catalyst facilitates the reaction without being consumed in the process. As used herein, the term "catalyst" refers to a substance that increases the rate of a chemical reaction without being consumed or permanently altered in the overall process, typically by providing active sites or an alternative reaction pathway that lowers the activation energy. In the context of the present application, the catalyst is one that is suitable for the dehydration of an alcohol to an ether. Where there is a reference to an amount or degree of "conversion" from alcohol to ether, this refers to the weight fraction of ether product relative to alcohol feed.

[0106] The processes and systems of some embodiments of the present application are described as being "mobile" or "on-board". As used herein, "mobile" refers to a configuration in which the combination of operational components is integrated with or mounted on or within a structure that moves with an engine (or associated vehicle powered by the engine), such that the production of the two fuel parts from the feed fuel occurs during operation and in proximity to the engine rather than at a fixed, stationary location. The term "mobile process" refers to a process where the production of the two fuel parts from the feed fuel, each used in fueling the engine, is performed on-board or in conjunction with the engine system, distinguishing it from conventional chemical production processes carried out in permanent installations or fixed plants. " On-board" is a similar term that refers to the requirement that the operational components are on-board a vehicle associated with an engine being powered by the two-part fuel. The vehicle may be, for instance, a ship, train, truck, bus or otherwise.

[0107] " Closed-loop" or "closed-system" refers to a requirement that all conversion products generated from the feed fuel are integrated into the process, such that the only waste products arising from the fuel conversion process are gaseous products (e.g. engine exhaust), and there are no liquid byproducts that need to be drained from the system, or accumulated and removed for sending to waste. Catalyst that may degrade and require regeneration or eventual disposal will be understood to fall outside of the fuel stream.

[0108] The term "superheating" refers to a process of increasing the temperature of a vapour above its saturation temperature at a given pressure, without causing condensation, thereby producing a superheated vapour. This improves efficiency in downstream operations such as chemical reaction. A superheater is a device or apparatus configured to perform superheating. In the context of alcohol vapour, the superheater is adapted to receive alcohol vapour, typically generated by an upstream evaporator, and apply controlled thermal energy to elevate the vapour temperature above its boiling point at the given pressure.

[0109] " Separation" refers to a process or operation in which a mixture comprising two or more components is divided into two fractions based on differences in physical or chemical properties, such as phase, volatility or chemical composition. A separator is a device or apparatus configured to perform such a separation.

[0110] " Flash separation" (or similarly, "flash evaporation") in the present specification refers to a process in which a mixed gas- and liquid-containing fluid mixture is partitioned into a gas (vapour) fraction and a liquid fraction. The "flash separator" or "flash evaporator" is a unit comprising an enlarged space / chamber with structural features for collecting the liquid fraction at a lower end and for allowing the separation of the vapour fraction at a top end. The flash separator may be designed with structural features for facilitating coalescence and collection of liquid droplets from the fluid mixture, and to minimize entrainment of liquid into the vapour fraction.

[0111] The present inventions will now be described in further detail with reference to the drawings. The drawings have been provided for the purpose of illustrating preferred embodiments of the present invention. Therefore, it will be understood that the present invention should not be considered to be limited solely to the features as shown in the drawings.

[0112] Hgure 1 shows the system components and corresponding process details for the production of two fuel compositions from a feed fuel. The system will be described using the example of a feed fuel comprising methanol as the alcohol, 10% by weight water and 1000ppm of lubricity improver. The main fuel in this example consequently comprises methanol as the alcohol, and the secondary fuel comprises dimethyl ether (DM E) as the ether. However, it will be appreciated that the range of feed fuel compositions that may be used in the process to produce the main and secondary fuels can vary from this composition. This description of the systems of Figures 1-4 should be read in this context. Therefore, forexample, it will be understood that the "methanol flash evaporator" and " DME flash separator" could equally be described as an “alcohol flash evaporator" and an “ether flash separator", respectively.

[0113] in the arrangement of Figure 1, there is provided as a complete system for the delivery of a single feed fuel, stored in feed fuel tank (1) (which may alternatively be also referred to as a first fuel tank), for the production and delivery of two fuel compositions, including a main fuel and a secondary fuel, to an engine (2).

[0114] A first stream of the feed fuel is pumped by a pump (3) through a conduit (4), to a heater (5) where the first stream of feed fuel is heated. Heating of the feed fuel in the heater is through use of heat from an engine exhaust as described in further detail below. This heat may be supplemented by other heat sources (not shown), or In alternative embodiments, a different heat source for the heater may be used.

[0115] The heater (5), which is in the form of a heat exchanger, effects heating of the feed fuel (which may be combined with a returned stream of unreacted alcohol and water, as described further below) to an elevated temperature, which is suitably higher than the boiling point of the subject alcohol in the composition entering the heater. A suitable temperature range for the heating of the feed fuel will be dependent on the feed fuel composition, but a suitable temperature range in one illustrative embodiment is about 110 to 180°C based on about 7 bar gauge pressure. For methanol In this embodiment, the temperature may be around 140:’C + / - 20’C, and for ethanol the heating temperature may be 15-20’C higher. The set temperature will vary depending on the type of alcohol and system pressure. Alcohol is evaporated from the first stream of feed fuel and the evaporated alcohol is separated from a residue in a separator, in the form of a flash evaporator, referred to here as methanol flash evaporator (6). The evaporated or vapourised methanol, shown as dashed region (7) in the methanol flash evaporator (6) may contain a small amount of entrained liquids, such as entrained water. The amount of entrained water will depend on the operation and design of the flash evaporator. A liquid residue (8) is separated from the vapourised alcohol. The liquid residue comprises the lubricity improver, which is not significantly entrained into the separated alcohol stream. When present, corrosion inhibitor and / or feed fuel colour additives are also high boiling point materials, and are substantially separated from the alcohol into the liquid residue. The relative amount of alcohol, and the extent of entrainment of other components into the vapourised alcohol portion, is controlled by setting the operating temperature and pressure of the methanol flash evaporator to suitable levels. These settings also impact the amount of water that is co-evaporated with the evaporated alcohol, where water is present in the composition (e.g, feed fuel containing any recycle stream) subjected to separation.

[0116] As noted above, while the residue (8), separated from the first stream in the alcohol separation step will contain water (and typically a significant proportion of the water present in the feed fuel), some water vapour will be present in the alcohol vapour that is separated from the residue.Accordingly, it will be appreciated that references to an alcohol separation step should not be interpretedas suggesting that this step effects separation of alcohol from all other components in the feed fuel. Nevertheless, the alcohol separation step does result in the substantial separation of particular target components present in the feed fuel, which are important to remove prior to contact with the catalyst. This includes high boiling point materials (e.g. lubricity improver). This also includes particulate matter that may be present in the feed fuel. This also allows for the return of those separated components into a second stream of the feed fuel, to increase the content of those target components (notably the lubricity improver, and if present, the corrosion inhibitor and optionally water) in the main fuel that is produced from the feed fuel with supplementation by the residue.

[0117] The liquid residue (8) comprising lubricity improver, is optionally cooled in the bottoms cooler (9), and sent to a bottoms tank (10). The cooled liquid residue may also pass via a filter (11) for filtration of any solids, prior to delivery to the bottoms tank.

[0118] The vapourised methanol (7) - which comes from the overheads stream of the flash evaporator (6) - then passes via a conduit (12) to a superheater (13) for superheating of the methanol. The superheater raises the temperature of the alcohol separated in the alcohol separation step. The superheater utilizes sensible heat to superheat a vapour (in this case, an alcohol vapour) in order to increase its enthalpy. The superheated separated methanol then passes through conduit (14) to a series of two reactors, including a first reactor (15) and a second reactor (16), separated by an intercooler (17). The reactors may be operated in a plug flow reactor arrangement. The reactors contain catalyst, and in the reactors the alcohol, such as methanol, present in the feed material fed to the reactor, is converted to an ether (in this case, dimethyl ether, hereafter referred to as DME) and water.

[0119] The first reactor is of a first length or diameter, and the second reactor is of a second length and / or diameter which is different to that of the first reactor. The catalyst beds are in the illustrated embodiment arranged in order of increasing residence time (declining space velocity) allowing for least conversion in the first bed when the catalyst is at its highest risk of overtemperature with the highest proportion of fresh reactor feed. The subsequent reactor (or reactors if more than two subsequent reactors) receives feed with an increased concentration of reaction products. This arrangement acts as a brake on the rate of conversion and minimizes risk of hot-spot generation.

[0120] The intercooler (17) aids in controlling the input temperature to the catalyst bed in the second reactor (16).

[0121] Each reactor (15,16) may comprise a modular catalyst basket holding the catalyst within the reaction zone of each reactor (not shown in detail). The modular basket arrangement allows for the rapid removal of degraded catalyst from the reactor and replacement with a replacement basket of fresh or regenerated catalyst. The removed basket of degraded catalyst can then be regenerated and returned to the unit in future when the next basket of degraded catalyst requires removal and replacement. This modular arrangement provides another means for enabling minimum down-time due to catalyst degradation. There may be a service centre that receives baskets of degraded catalyst for regenerationand / or recycling or disposal of the spent catalyst. Thus, in embodiments containing this feature, there is provided a modular catalyst basket allowing for removal of degraded catalyst from the reactor and replacement with an equivalent catalyst basket comprising fresh or regenerated catalyst.

[0122] The first reactor may additionally optionally comprise an inert adsorbent bed (not shown) to further remove contamination species from the feed material fed into the reactor. The contaminants that may be removed include particulates, sulphur and base species such as amine. The adsorbent bed may utilize any suitable material, such as alpha alumina which is robust in terms of strength and can handle high temperatures.

[0123] The catalyst used in the catalyst bed may be of any suitable type. The catalyst may be a zeolite catalyst, or an alumina-based catalyst. In the test work performed herein, the catalyst was a zeolite-based catalyst supplied by BASF. The catalyst is preferably free of precious metal (i.e. it is a nonprecious metal conversion catalyst). Preferred catalysts have a high Tmax(or maximum safe operational temperature range). Preferred catalysts are resistant to water degradation - although in some embodiments strategies are implemented to further minimize the risk of degradation due to water presence. Catalyst materials are subject to expansion and contraction on heating up to operational temperature, and cooling at the end of an operating cycle (i.e. "off time"). Preferred catalysts have a lower target conversion temperature. Each catalyst has its own operational temperature range. An unacceptable temperature range is a temperature above the upper limit of the operational temperature range for the catalyst, and may be a temperature that is at least 10°C or more above the operational temperature range.

[0124] The reactor output from the second reactor (16) may pass through an optional filter (18).

[0125] The reactor output from the second reactor (16) is then directed via conduit (19) to a condenser - in this embodiment a first partial condenser (20) - and then to an associated first flash separator (21), where the condensed liquid product (22) comprising alcohol and water is separated from an ether-concentrated vapour (23) in the overhead space.

[0126] The ether-concentrated vapour (23) then passes through to a second partial condenser (24) and an associated second flash separator (25) - also referred to as the DME flash separator. In the DME flash separator (25), there is separation of a second stage condensation liquid product (26) which comprises alcohol and water and some ether (a higher amount than may be present in the first condensed liquid product (22)) from a higher purity ether vapour (27). " Higher purity" refers to the fact that the ether concentration of the separated vapour in this step is higher than that separated from the liquid phase in the preceding partial condensation step. Each stage of partial condensation and separation effects a progressive increase in the ether content of the separated vapour. The ether vapour (27) separated in the second stage of flash separation may be totally condensed or partially condensed in an optional DME condenser (28). In one example, this ether vapour coming from the second flash separator and condensed in the DME condenser may have "high" ether content - that is, in the region of90-97% by weight. Thereafter the condensed ether is delivered to a secondary fuel storage tank (29) -alternatively referred to as an ether storage tank. In the secondary fuel storage tank, a liquid secondary fuel (30) comprising ether is stored, and ether vapour (31) exists in an upper region of the tank, which may be used for ether flushing of the reactor as described in further detail below. The ether may also be used to prevent sub-atmospheric (or vacuum) conditions, preventing ingress of air, into selected parts of the circuit (e.g. tanks). The ether stored in the secondary fuel storage tank also allows for accumulation of ether during operation of the reactor (and during operation of the engine). Thereafter, when the engine is cold-started, accumulated ether in the secondary fuel storage tank (29) can be used as the secondary fuel delivered to the engine for initial operation, noting that ether production in the reactor will be delayed for a period of time from engine start-up. In an alternative arrangement, the entire ether upgrading circuit from (18) to (31) could be replaced with a different arrangement for the delivery of reactor output to the engine without ether upgrading, and in the vapour form.

[0127] The arrangement of Figure 1 also provides for a number of recycle or return streams for effective management of the components in the feed fuel and / or the main and secondary fuels produced in the process.

[0128] The liquid residue (8) that accumulates in the bottoms tank (10) is pumped by bottoms pump (32) to join a second stream of the feed fuel (33), which is conveyed through feed fuel pump (34), producing a main fuel (35) that is conveyed to the engine (2). The main fuel is directly injected into cylinders of the engine (not shown in detail).

[0129] The liquid product (22) comprising unreacted alcohol and water that is separated in the first flash separator (21) is pumped by liquid product pump (36) and directed to enter the first stream of feed fuel in conduit (4). This therefore allows for unreacted alcohol to return to the stream of feed fuel that is eventually directed back to the reactor (15,16), and allows for the water byproduct to be separated into the liquid residue (8) that is separated in the flash separator (6), and eventually become part of the main fuel (35) delivered to the engine (2). This provides an effective way of recovering and reusing alcohol that is not reacted in the reactor (15,16), and allows for a number of modes of operation of the reactor for the production of ether to be used, depending on the selected operating conditions. These can be controlled to ensure the required production of ether, while protecting the catalyst from excessive temperatures and / or hot-spot formation in zones of the reactor. These modes of operation are described in further detail below.

[0130] A further recycle stream involves the return of the full condensation liquid product (26) comprising some water, alcohol and ether, to conduit (19) to be combined with the reactor output upstream of the first partial condenser (20).

[0131] A variation on the process of Figure 1 is illustrated in Figure 4. In the process of Figure 4, a different set of recycle streams are shown. The same numerals are used in Figure 4 as for Figure 1 to indicate the corresponding operational components in the system.

[0132] As for Figure 1, the liquid residue (8) that accumulates in the bottoms tank (10) joins a second stream of the feed fuel (33), which is conveyed through feed fuel pump (34), to produce the main fuel (35) that is conveyed to the engine (2). However, in a variation on the process, the entirety of the feed fuel may be vaporised (e.g. in a heater only, such that the separator (6) is optional), and the entire vaporised feed fuel stream may be directed to the superheater (13) prior to entry into the reactor. In this variation, separation of a liquid product is avoided. The main fuel may in that case be produced by adding to a second stream of the feed fuel a separate lubricity additive (not shown) to produce the main fuel separately. The disadvantage of this process is that all feed fuel components progress through the reactor. However, for higher purity feed fuels (e.g. methanol with low impurity content), this may be tolerated.

[0133] In the alternative process of Figure 4, the liquid product (22) comprising unreacted alcohol and water that is separated in the first flash separator (21) is directed to one of three different locations - either (i) via conduit (46) towards conduit (4) for joining the first stream of feed fuel leading towards the heater (5) and the separator (6), or (ii) via conduit (47) towards conduit (48) for joining the liquid residue (8) that is directed to bottoms tank (10) (and eventual incorporation into the main fuel), or (ill) via conduit (49) towards conduit (19), for combination with the reactor output leading to the first partial condenser (20). The process may include one, two or all three of those conduits (46), (47) and (48), depending on the selected operational arrangement.

[0134] Where the liquid product (22) is directed via conduit (49) to join the reactor output stream before delivery to the first partial condenser (20) in accordance with option (iii), this has the advantage of reducing the temperature of the reactor output to a suitable degree. By way of example, a typical reactor output stream temperature may be about 230-270°C, and the liquid product stream about 100-120°C, and in view of the typical relative volumes of each, the temperature of the combined product may be about 130-150°C. The liquid product (22) contains water, alcohol and some co-condensed ether, and retention of the ether through this stream allows for ether recovery.

[0135] If option (ii) is selected, depending on the temperature and pressure of the liquid product (22) exiting the first flash separator (21), the conduit (47) may join the liquid residue exiting the methanol flash evaporator (6) prior to bottoms cooler (9) (as illustrated), or following bottoms cooler (9) (not shown). In the event that conduit directs the liquid product (22) to join liquid residue (8) following bottoms cooler (9), there may be an additional cooler for cooling of the liquid product (22) between the first flash separator (21) and the junction where that liquid product (22) is combined with the cooled liquid residue (8). The additional cooler is required to reduce the temperature of the liquid product (22) to be similar to that of the cooled liquid residue (8).

[0136] In the alternative process of Figure 4, a further recycle stream involves the return of the full condensation liquid product (26) comprising some water, alcohol and ether, to conduit (50) to be combined with the fluid output from the first partial condenser (20). Whilst this is illustrated, it is alsopossible for the process to contain just one stage of condensation and separation, in a condenser (20) and flash separator (21), and to omit the second condenser (24) and second flash separator (25). In this case, the ether vapour (23) from the first flash separator may be directed to DME condenser (28) and to the secondary fuel storage tank (29). Alternatively, the DME condenser (28) can be omitted, and the ether vapour can be delivered directly to the engine. In a further alternative, the entire ether upgrading circuit from (18) to (31) could be replaced with a different arrangement for the delivery of reactor output to the engine without ether upgrading, and in the vapour form.

[0137] Additional variations on the process of Figure 4 are also possible. For example, conduit (46) may be repositioned to join the conduit between the heater (5) and the methanol flash evaporator (6). Given the relative temperatures of the liquid product (22) compared to the feed fuel, and the temperature of the feed fuel following heating in heater (5), delivery of the liquid product to the conduit following the heater (5) may be selected. Alternatively, conduit (46) may direct the liquid product (22) directly into the alcohol flash evaporator (6). The liquid product may contain a significant DME and methanol content, and these components may be separated into the vapour phase, together with the methanol from the feed fuel, in the flash evaporator (6).

[0138] The positioning of filters, pumps, conduits and other flow control features in Figures 1 and 4 may be modified.

[0139] These variants are provided as examples only, and further modifications may be incorporated into the process as desired.

[0140] In Tables 1, 2 and 3 below, simulation results are shown for a range of partial condenser and total condenser operation conditions for system pressures of 3 bar absolute, 8 bar absolute, and 13 bar absolute, respectively. It should be noted that a wide range of operational pressures may be selected, from atmospheric to 25 bar absolute. The indicated pressures were selected for demonstration purposes. In tables 1 and 2, there is a first section showing the operation of the first stage partial condenser, and then a second section showing the operation of the second stage condenser - referred to here as the "total condenser" (also referred to herein as a full condenser). In table 3, the simulation test results for a system pressure of 13 bar (absolute) is provided, with the partial condenser and total condenser data set out in the left-hand side and right-hand side, respectively. The tables illustrate the data obtained without a recycle loop (for the separated unreacted alcohol and water being re-directed to re-join the feed fuel stream upstream of the reactor), and with partial condensation followed by total condensation of the overheads. The data provides a demonstration of the effectiveness of a simplified version of the separation for purifying the DME. By the end of total condensation, it will be noted that with appropriate controls, high purity DME product is available from total condensation of the separator overheads.Table 1. Simulation results over a range of partial condenser operating conditions for a system pressure of 3 bar(a) (i.e. bar absolute)Partial CondenserOperating Liquid Mass Mass Composition Water DutyTemp.(°C) Flow Rate H2O Meth DME Recovery in (kW)(kg / hr) Liquid 20 14.3 50.63% 30.18% 19.19% -9.15 99.6% 40 12.6 56.91% 32.35% 10.74% -8.55 98.7% 60 11.1 62.38% 31.44% 6.18% -7.77 95.7% 80 9.0 70.16% 26.79% 3.05% -6.60 86.8% 100 5.2 80.17% 18.57% 1.27% -4.55 57.4% 110 1.4 85.20% 14.05% 0.75% -2.47 17.0%Total CondenserOperat- Mass Composition Product Vapouring H2O Meth DME Vapour Mass Duty DME Temp. Pressure Flow Rate (kW) Recovery (°C) at 37.8°C (kg / hr)(bar) 1.9 10.0 0.26% 0.93% 98.81% -1.31 78.3% 8.28 2.9 11.7 0.83% 2.85% 96.32% -1.68 89.3% 7.98 5.2 13.1 2.36% 6.85% 90.79% -2.16 94.6% 7.37 8.6 15.3 6.24% 13.03% 80.73% -3.07 97.8% 6.52 10.9 19.1 16.17% 17.99% 65.84% -5.14 99.5% 5.88 9.5 22.8 26.35% 18.37% 55.27% -7.58 99.9% 5.86Table 2. Simulation results over a range of partial condenser operating conditions for a system pressure of 8 bar(a)Partial CondenserOperating Liquid Mass Mass Composition Water DutyTemp.(°C) Flow Rate H2O Meth DME Recovery in (kW)(kg / hr) Liquid 60 16.0 44.86% 26.49% 28.65% -8.46 99.1% 80 12.6 55.65% 30.59% 13.75% -7.54 96.9% 100 10.6 62.50% 30.37% 7.13% -6.56 91.7% 120 8.4 68.36% 27.96% 3.68% -5.30 79.0%140 4.2 73.45% 24.75% 1.80% -3.19 43.0%Total CondenserOperat- Vapour Mass CompositionProduct ing Mass H2O Meth DME Duty DMEVapour Temp. Flow Rate (kW) RecoveryPressure(°C) (kg / hr)at 37.8°C (bar) 36.4 8.3 0.80% 1.88% 97.32% -1.03 63.7% 8.09 38.6 11.6 1.95% 4.62% 93.44% -1.67 86.3% 7.64 41.7 13.6 4.42% 8.56% 87.02% -2.32 94.0% 7.04 45.4 15.9 9.58% 12.93% 77.49% -3.38 97.6% 6.4148.2 20.0 20.62% 16.71% 62.68% -5.72 99.4% 5.98 Table 3. Simulation results over a range of partial condenser operating conditions for a system operating pressure of 13 bar (a)Corsfers w? cfcsl Soft® SB setas am ssta-m -oi « 1.1W 2,24^ -525 $ 133 SfcStm SS SSS KW -533 33.1 23'!^ 4211s 32. SW - 532 123 332W ®?.» -5- 25 32 32.5W >223 722 US 55.3W 233536 4.53^ U. TS m 11,43^ rs.sm -JSS 55s153 375ZM tS -SSS 2. M -2 3T.3 SSW U. W SS.451& -5. SS 3.15

[0141] Points of note arising from the above data are as follows:1. High purity ether (e.g. DME of at least 90%, and typically up to 97%) can be produced without the need for distillation and its associated complexities. At the same time, the system can be operated to produce lower ether (DME) concentrations, with the balance comprising unreacted alcohol, and water.2. If greater unreacted alcohol is required in the fumigant product with low water presence, one way to do this is to directly blend alcohol rich feed with lower purity ether product. The offsetting effects of this are: on the negative side that reactor temperature is not being minimized. By lowering conversion temperature and providing additional unreacted alcohol to the secondary fuel, the temperature rise and risk of hot spots will be minimized, adding to the sustainability of ongoing active catalyst performance. On the plus side all major components of the ether production unit can be smaller for a given production of secondary fuel, a space saving and duty lowering benefit on key items of equipment. It remains advantageous to keep the fumigant water level low, so an optimal level in the simplified case described above a target DME content for the secondary fuel accumulating in tank (29) could range from, in the 8 bar case, from 85 to 90% by weight DME, corresponding to water contents of 5% to 3% wt. respectively. While secondary fuel compositions with higher water contents are also possible, through suitable adjustments as presented in the tables or through blending of the secondary fuel produced and stored in tank (29) with another process stream (e.g. another stream of main fuel), some issues may arise that require management. Such issues associated with higher amounts of water in the secondary fuel that is injected into the air inlet of the engine include (a)phase separation in the secondary fuel storage tank (29), (b) increased risk of delayed or poor ignition in the engine (2), due to higher water presence, especially at low load, (c) the secondary fuel (or "fumigant") droplets impacting the cylinder liner, causing increased liner wear. Therefore, it may be desirable to control the water content of the final secondary fuel composition delivered into the engine to be not more than 10%.3. Lower purity ether, such as DME, can be achieved by operating the first flash separator (21) at a higher cut temperature, drawing additional water and methanol into the overheads ether (DME) rich stream. The second flash separator (25) is the final stage where water and alcohol (e.g. methanol in this example) can be removed from the fumigant used by the engine by lowering the condenser operating temperature.4. It should be noted that higher carbon number alcohols produce ethers with a higher carbon number, and ethers mixed with significant alcohol content condense more easily, due to higher boiling points of higher carbon number alcohols and their associated ethers. This reduces the need for higher pressure condensation against ambient air in such situations.

[0142] It will be noted that during dehydration of alcohol to ether in the reactor, water is coproduced with the ether. Water vapour arising from the conversion may be about 50% by volume of the reactor. The quantity of water in the reactor at shutdown will be the sum of the water entering the reactor with the feed material going into the reactor, plus co-produced water from the dehydration reaction. This water will be adsorbed into the catalyst mass, and will increase with every shutdown until an equilibrium is reached. This potential increase in water on catalyst (depending on the reactor temperature profile during operation) can be a factor that causes accelerated catalyst decline. It is even more desirable to avoid water condensation following shut-down in operations conducted in cold climates, since frozen water expands, and the expansion of the water in the catalyst space can have an impact on catalyst integrity. In some aspects and embodiments, a conduit (37) is provided to allow ether vapour (31) in secondary fuel tank (29) (or ether storage tank) to be delivered through the reactor, via a conduit (in this case, conduit (12)) upstream of the reactor, through which ether vapour (31) can be used to flush or purge the reactor space to flush water therefrom. The water flushing from the reactor, using this ether vapour, may be conducted at a suitable time, such as during a shut-down procedure for shutting down of the reactor.

[0143] Conduit (37) is an ether flushing conduit and is configured to deliver the ether vapour upstream of the alcohol superheater, allowing ether to be conveyed from the secondary fuel tank, through the alcohol superheater, and then through the reactor to flush a reactor space within the reactor with ether. The ether may then pass through the reactor in the same manner as ether produced in the reactor, so as to pass through any of the processing steps following the reactor and return to the secondary fuel tank.

[0144] As noted above, ether flushing is preferably conducted during a shut-down procedure for the reactor. When the reactor is turned off, the reactor will be in a hot condition (e.g. reactor space temperature in the vicinity of about 200 - 250°C). While the reactor space is still at an elevated temperature, ether gas may be directed through reactor space (15,16) at an elevated temperature - for example, at a temperature of at least 180°C. The gas may be directed through this space through the operation of any gas flow generator, such as a fan or blower, or through the application of a differential pressure between the reactor inlet and outlet. The gas may be heated prior to being directed through the reactor space. This may be through heating in the alcohol superheater or otherwise. Examples of other heater types include electric heaters.

[0145] At the time when the reactor is turned off, the contents of the reactor will contain over 50% water by volume, with the balance predominantly being ether and alcohol. There will be small compositional changes as the reactor cools down. If the ether flushing is not employed, the catalytic reactor, which is typically in the form of a tube reactor, will gradually cool down to ambient temperature, first at the walls, and then inwardly towards the middle of the tubes. As the unit cools, the reactor will also lose pressure, which is a factor that delays condensation of water, particularly in the middle of the reactor. Without the operation of the ether flushing, or any other form of inert gas flushing of the reactor space, the condensed liquid phase will have an adverse impact on the catalyst. This is particularly the case in freezing conditions where hydrogen bonding will have the largest effect, and where there is a potential impact on catalyst pore strength. There will also be radially more water on the catalyst close to the walls, where condensation commences. While one may consider maintaining hot catalyst walls to avoid this water accumulation in these zones, this may not be viable and a dry purge gas may not be available for such applications, particularly if on-board an engine. Using the ether gas that is stored in the system provides a very unique and effective way to address water accumulation at shut-down, without requiring a separate inert gas source.

[0146] The ether directed through the reactor is suitably substantially free of water, or has a water content of less than 10%, less than 5%, less 3%, less than 2% or less than 1%. The ether in this example is suitably passed through the reactor space at an elevated temperature, such as at least 180°C, (e.g. 195 - 210°C) in the vapour phase. This may vary depending on the catalyst, and may be higher for alumina catalysts, for one example. Any suitable additional control steps and units may be utilized in the performance of the ether gas flushing during shut-down of the reactor.

[0147] The engine (2) is operated with main fuel being delivered to the engine through high pressure fuel injectors. Secondary fuel is either combined with air for delivery into the inlet air directed to cylinders of the engine. Delivery of secondary fuel into the engine is controlled through a secondary fuel delivery control (38). In one mode of operation, there is the option for a consistent amount of secondary fuel to be delivered to all cylinders of the engine. In an alternative mode of operation, the amount of secondary fuel delivered may be controlled separately for each cylinder, in response to the separateneeds of each cylinder. In an alternative arrangement, the secondary fuel may be directly injected into cylinders of the engine, rather than via inlet air, but separately to the main fuel injection.

[0148] The engine (2) produces an engine exhaust, which is shown schematically as exiting the engine at location (39). The engine exhaust in the first aspect of the invention, and in some embodiments, is used to provide the heat source for heating of the main fuel in heater (5). The heating in the illustrated embodiment is achieved via an oil heater, which is schematically indicated by unit (40) which incorporates an oil circulation loop extending between the engine exhaust and the heater (5). A heatable fluid, such as one of the commercially available heat transfer fluids, may alternatively be used in the circulation loop.

[0149] The system may further comprise a control unit (41) which controls operation of the components in the system. The control unit receives data and controls the system in response to the data received. One data input in some embodiments is data indicative of an unacceptable temperature in the reactor. The data may be a temperature sensor or otherwise. In response to the data, the control unit may control components of the system or process steps to return the temperature in the reactor within an acceptable range. Those control options may include one or more of (a) varying the flow rate of alcohol through the reactor; (b) changing the temperature of feed material fed into the reactor, said feed material comprising the alcohol evaporated from the first stream of the feed fuel and separated from the residue, (c) changing the residence time of the feed material fed into the reactor; and (d) increasing the water content of the feed material fed into the reactor. Excessive temperature in the reactor has an impact on the catalyst life. In particular, there is a maximum temperature, Tmax, above which coke may accumulate on the catalyst bed. By using the above controls, the risk of coke accumulation is minimized.

[0150] The system may also involve a range of different modes of operation for the production of the ether from the alcohol in the feed fuel, those modes of operation having a potential impact on catalyst longevity. In the following, some modes of operation are described. In the following, it should be understood that an "off" time refers to a time during which the engine is operating but the units for the production of ether in the system are not in operation (e.g. accumulated ether produced previously is used, and the quantity stored in the storage tank does not need replenishment). An "on" time refers to a time when the engine is running and the ether production units are also operating.

[0151] " Zero-off": In one mode of operation, there may be zero "off" time, in which case the catalyst throughput would correspond with the average flow requirement, resulting in the ether inventory storage level taking all demand fluctuations deviating from the average flow.

[0152] " On-Off": In another mode of operation, the ether production unit, or EPU, which comprises at least the reactor(s) of the system, operates so as to produce ether at an ether production level corresponding to the higher of the maximum rated torque and the maximum rated power, and when sufficient ether is produced, the EPU is turned off.

[0153] " Maximum-off": In this mode of operation, the EPU is operated at design load, which may, for example, correspond to 150% or 200% of the maximum rated power / torque of the engine.

[0154] The duration of the off mode in the maximum off mode of operation (and also the on-off operation mode) may be from minutes to hours. Through use of the ether flushing steps described above, water can be flushed from the reactor as a means to reduce or avoid catalyst decline due to the presence of water, and the impact of contraction and expansion under the variation in the temperature in the reactor (from operational temperature to "off" temperature, and vice versa).

[0155] Other factors that may impact on coke formation, beyond temperature, include pressure - higher pressures may lead to accelerated coking, and also excessively low pressures can also lead to coking due to a lower precursor concentration compared to feed, which can drive forward the cokeforming reaction. Different alcohols have a different tendency to form coke under dehydrating reaction conditions. Fortunately, methanol has a lower tendency to generate coke compared to ethanol, and longer chain alcohols (C3 and above) can have a higher tendency to cause coking of catalyst. Increasing water presence can reduce coke formation, but excessive water presence can also be problematic, so a balance is desired.

[0156] Starting up an engine under cold or freezing weather conditions is potentially challenging for alcohol-based feed fuels and alcohol-based main fuels. Having an ether fuel source available from the EPU greatly assists in low temperature start-up phase in the following respects:(a) The system and process of preferred embodiments provide the ability to prepare "start up secondary fuel" (fumigant) with a high ether content and minimal water content - for example, less than 10% water, less than 5% water, less than 3% water, less than 2% water, and even as little as 1% water. This high ether concentration is advantageous for start-up operation. In existing processes, the output of an ether production unit typically has a much higher water and unreacted alcohol content, and no on-board avenues to provide a higher ether content secondary fuel to the engine.(b) The engine may be run in predominantly "fumigation mode" (i.e. a mode where the secondary fuel is temporarily used as the predominant fuel source for the engine), with no cold fuel entering the freezing engine before the engine has had time to heat up. Such an approach can reduce ice formation and potential sensor (eg NOX) blockage while the engine warms up. An additional benefit of this start-up approach is the avoidance of lubricity additive dilution with very low vapour pressure alcohol fuel. Start-up engine cycles are closely regulated, and misfiring due to low alcohol volatility are not acceptable in emissions regulated jurisdictions.(c) A stream of ether produced in the reactor, such as one of the higher ether content streams (e.g. secondary fuel stream) could be delivered to the main fuel during start up to increase the fuel volatility making it easier to ignite under low freezing temperature conditions. This would require the addition of further components not currently shown in the arrangement of Figure 1.(d) The above-described stages for processing the reactor output, as per the second aspect and preferred embodiments, allow for the production of high ether-content secondary fuel, with low water content. In some embodiments, the ether content of the secondary fuel delivered to the engine may be at least 80%, at least 85%, at least 90%, at least 95% or as high as 99% by weight. Secondary fuel may also contain some residual water - such as at least 0.3% by weight or more water, which places an upper limit on the ether that may be present in the secondary fuel. The balance of the secondary fuel is largely made up of water and unreacted alcohol.

[0157] Figure 2 illustrates a more simplified version of the system for the production of two fuel compositions - a main fuel (35) and a secondary fuel (30) - from a feed fuel (42). In the system of Figure 2, a small stream (42a) is fed to the EPU, which is represented schematically by the four boxes illustrated in the upper part of Figure 2. The stream (42a) is typically less than about 10% by weight of the total feed fuel input, averaged across an extended time of operation of the engine (e.g. 24 hours). This small stream of feed fuel is heated (43) to vaporise the feed fuel stream. In a separation step (44), which may be performed in a flash separator, the light overheads (predominantly the alcohol, such as methanol) are separated from the heavy bottoms (8) (predominantly water, lubricity improver and other heavy additives). The overheads stream enters a reactor (45) containing the catalyst, where the alcohol -methanol - is converted to ether- DME - and water. The water-rich bottoms (8) from the alcohol separation step (44) are fed to a high pressure pump (not shown) and integrated with the high pressure injection of the feed fuel to the engine - the integrated product constituting the main fuel (35). The reactor output goes through cooling and separation (46), which may optionally involve an ether upgrading step (to increase the percentage of ether in the stream as compared to the ether content exiting the reactor). The ether-rich output stream is then cooled to a liquid phase, and serves as a secondary fuel (30) injected into the engine or stored in a tank which is used for start-up and transient accommodation.

[0158] it will be noted that although the system and process of the illustrated embodiment is shown as a single unit comprising one feed fuel tank, one engine, one grouping of components for separating alcohol from the feed fuel, one grouping of components for converting the alcohol to ether, one grouping of components for increasing the ether content of the reactor output, one engine exhaust heat recycle loop, and single storage tank for the secondary fuel, the system may comprise multiples of the individual components in the system. So, as one example, there may be a bank of engines. Either a single secondary fuel storage tank may supply secondary fuel to the plural engines, or plural secondary fuel storage tanks may supply secondary fuel to plural engines, Engine exhaust gas heat capture and reuse may come from the engine being delivered the fuel or another engine or engines in the arrangement. The components may be located within a single engine environment, or the components may be spaced more distantly from one another. In the second aspect, reference is made to "an engine" in multiple instances, to reflect that each reference to "an engine" may be to either the same engine, or differentengines. References to "an engine" in other aspects and embodiments are used in a similar manner. In seme embodiments, the engine is the same engine. Figure 1 demonstrates the process as applied to one engine, where the engine exhaust of the engine fed with the two fuel compositions is the engine producing an exhaust that is used for the initial heating step. In such embodiments, after the first reference to “an engine", the references to "an engine" can be replaced with references to "the engine". In other embodiments (not illustrated), the system and process may contain just those features necessary for the production of the two fuels from the feed fuel.

[0159] in additional variations, the claimed process may be a process for catalytically converting a feed fuel comprising alcohol into a secondary fuel comprising ether, the process comprising:- directing a stream of the feed fuel to a reactor comprising the catalyst and catalytically converting the alcohol in the feed fuel to an ether and a water byproduct;- storing the ether in an ether storage tank;- flushing the reactor with ether from the ether storage tank to flush water byproduct from the reactor; and- producing secondary fuel from the ether produced in the reactor.

[0160] As it will be appreciated, the above variation is suitable for converting certain feed fuel compositions into a secondary fuel, and without the need to add a residue to another stream of the feed fuel to produce the main fuel. As an example, for a feed fuel comprising a high percentage of alcohol and low water and / or other components, this feed fuel may not require the initial separation process to be performed, and the feed fuel may be sent directly to a reactor. Water accumulation in the reactor is an issue regardless of the composition of the reactor feed material, as water constitutes up to about 50 volume % of the reactor output. In this aspect, the feed fuel may be used without modification as a main fuel directly injected into the cylinders of an engine, and the ether produced in the reactor may be used as a secondary fuel, either as-is or with further modification. This concept provides a means for protecting catalyst from the impact of water, and may be used in the present process for the production of two fuels from a feed fuel, or may be used in any other process involving catalytic dehydration of alcohol to produce ether, with water as a byproduct.

[0161] In a further variation on the fourth aspect, the present application provides a process for catalytically converting a feed fuel comprising alcohol Into a secondary fuel comprising ether, the process comprising:- directing stream of feed fuel comprising alcohol to a reactor comprising a catalyst and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water;- receiving data indicative of an unacceptable temperature in the reactor; and- performing one or more of the following steps, based on the data, to return the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing temperature of feed material fed into the reactor, said feed material comprising the alcohol evaporated from the first stream of feed fuel and separated from the residue;- changing the residence time of the feed material fed into the reactor; and- increasing the water content of the feed material fed into the reactor.

[0162] In a variation on the first aspect, the present application also provides a process for producing a secondary fuel comprising ether from a feed fuel comprising alcohol, the process comprising: - storing the feed fuel in a feed fuel tank;- directing a first stream of the feed fuel from the first fuel tank to a separator and separating alcohol from a liquid residue;- directing the separated alcohol to a reactor and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water; - condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output;- directing the separated unreacted alcohol and water to the first stream of the feed fuel prior to alcohol separation, and- producing secondary fuel from the ether-concentrated portion of the reactor output.

[0163] In another variant of the first aspect, the present application further provides a process for the production of ether from a feed fuel comprising alcohol, the process comprising:- vaporising alcohol from a first stream of the feed fuel;- catalytically converting the vaporised alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water;- condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output; and- producing secondary fuel from the ether-concentrated portion of the reactor output.Feed Fuel Composition

[0164] The feed fuel comprises alcohol. The alcohol is preferably methanol or ethanol. In some embodiments the alcohol is methanol.

[0165] The methanol content of the feed fuel may broadly be at least 0.2% by weight, or at least 0.5%, at least 0.8%, at least 1% at least 2%, at least 3%, at least 4%, at least 5%, at least 10%, at least 20%, at least 30%, at least 40% at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% by weight, at least 96%, at least 97%, at least 98%, at least 99%, at least 99.5% or at least 99.85% by weight methanol. The upper amount of methanol in a feed fuel where the alcohol comprises methanol will be dependent on the amount of water in the feed fuel. Excluding the water component, the upper amount of methanol may be 99.9%, 99.85%, 99.8%, 99.75%, 99.5%, 99%, 98%, 97.5%, 95% or 90% by weight of the water-free component of the feed fuel. Including water, the upper amount of methanol inthe methanol-containing fuel may be 99.9%, 99.85%, 99.8%, 99.75%, 99.5%, 99%, 98%, 97.5%, 95%, 94.9%, 94.85%, 94.5%, 94%, 90%, 89.9%, 89.85%, 89.5%, 89%, 85%, 84.9%, 84.85%, 84.5%, 84%, 80%, 79.9%, 79.85%, 79.5%, 79% or 75% of the methanol fuel content. Each of the lower limits and upper limits may be combined to form a range for the methanol content of the fuel - noting that any lower limit combined with an upper limit must be less than the upper limit. The amount of methanol may therefore be within a range of: 0.2% - 99.85%, 5% - 99.85%, 80% - 99.85%, 89.85% - 99.85%, 94.85% - 99.85% of the water-free content of the feed fuel, or within a range of 0.2% - 99.85%, 5% - 99.85%, 80% - 99.85%, 89.85% - 99.85%, 94.85% - 99.85% by weight of the total feed fuel composition.

[0166] To use the example of a 10% water content methanol-water fuel, the methanol content of the feed fuel may be at least 0.2% by weight, or at least 0.5%, at least 0.8%, at least 1% at least 2%, at least 3%, at least 4%, at least 5%, at least 10%, at least 20%, at least 30%, at least 40% at least 50%, at least 60%, at least 70%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 89.5% or at least 89.85% by weight methanol.

[0167] The balance of the feed fuel may be constituted by lubricity additive, additional performance additive(s) (such as corrosion inhibitor, fuel colour additive, fuel extender, and so forth) optional water and impurities (such as impurities coming from the alcohol (e.g. methanol) or water source).

[0168] The remaining portion of the feed fuel (e.g. the remaining 0.5%, for an 89.5% methanol content fuel with 10% water) may, for example, include one or more of: a performance additive such as a lubricity improver, corrosion inhibitor, fuel extender, and so forth), impurities (such as alcohols other than methanol (e.g. ethanol), acetone, chlorine-containing compound(s), sulphur-containing compound(s) and inorganic iron-containing compound(s)).

[0169] Where ethanol is the alcohol in the feed fuel, The ethanol content of the feed fuel may broadly be at least 0.2% by weight, or at least 0.5%, at least 0.8%, at least 1% at least 2%, at least 3%, at least 4%, at least 5%, at least 10%, at least 20%, at least 30%, at least 40% at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% by weight, at least 96%, at least 97%, at least 98%, at least 99%, at least 99.5% or at least 99.85% by weight ethanol. The upper amount of ethanol in a feed fuel where the alcohol comprises ethanol will be dependent on the amount of water in the feed fuel. Excluding the water component, the upper amount of ethanol may be 99.9%, 99.85%, 99.8%, 99.75%, 99.5%, 99%, 98%, 97.5%, 95% or 90% by weight of the water-free component of the feed fuel. Including water, the upper amount of ethanol in the ethanol-containing fuel may be 99.9%, 99.85%, 99.8%, 99.75%, 99.5%, 99%, 98%, 97.5%, 95%, 94.9%, 94.85%, 94.5%, 94%, 90%, 89.9%, 89.85%, 89.5%, 89%, 85%, 84.9%, 84.85%, 84.5%, 84%, 80%, 79.9%, 79.85%, 79.5%, 79% or 75% of the ethanol fuel content. Each of the lower limits and upper limits may be combined to form a range for the ethanol content of the fuel -noting that any lower limit combined with an upper limit must be less than the upper limit. The amount of ethanol may therefore be within a range of: 0.2% - 99.85%, 5% - 99.85%, 80% - 99.85%, 89.85% -99.85%, 94.85% - 99.85% of the water-free content of the feed fuel, or within a range of 0.2% - 99.85%, 5% - 99.85%, 80% - 99.85%, 89.85% - 99.85%, 94.85% - 99.85% by weight of the total feed fuel composition. The remaining portion of the feed fuel (e.g. the remaining 0.5%, for an 89.5% ethanol content fuel with 10% water) may, for example, include one or more of: a lubricity improver, corrosion inhibitor, alcohols other than ethanol (e.g. methanol), acetone, chlorine-containing compound(s), sulphur-containing compound(s) and inorganic iron-containing compound(s).

[0170] In general terms, alcohol content (measured as a total alcohol content) of the feed fuel is typically at least 59.85%, at least 60%, at least 74.85%, at least 75%, at least 79.85%, at least 80%, at least 84.85%, at least 85%, at least 89.85%, at least 90% or at least 94.85% by weight of the feed fuel composition. Excluding the water component, the minimum amount of alcohol may be at least 90%, 94.85%, 95%, 96%, 97%, 98% or 99% by weight of the water-free component of the feed fuel. The balance may be provided by one or more components selected from: optional water, one or more performance additive such as a lubricity improver, corrosion inhibitor, fuel extender, and so forth, impurities (such as alcohols other than methanol and ethanol, acetone, formate, chlorine-containing compound(s), sulphur-containing compound(s) and inorganic iron-containing compound(s)). Excluding the water component, the minimum amount of alcohol may be at least 90%, 94.85%, 95%, 96%, 97%, 98% or 99% by weight of the water-free component of the feed fuel. Excluding the water component, the upper amount of alcohol may be 99.9%, 99.85%, 99.8%, 99.75%, 99.5%, 99%, 98%, 97.5%, 95% or 90% by weight of the water-free component of the feed fuel.

[0171] In some embodiments, the alcohol is methanol. In some embodiments, the alcohol is ethanol. In such embodiments where a particular alcohol is specified as the alcohol, any other alcohol may be viewed as an impurity, which may be present as a byproduct or contaminant that arises during the production of that specified alcohol.

[0172] The alcohol source for the feed fuel is suitably a chemical grade alcohol rather than an analytical grade of alcohol (noting that analytical grades are of high purity). As one example, a chemical grade of methanol is methanol that meets the specification of IMPCA. The alcohol source for the feed fuel is suitably a "fuel grade" of alcohol. Fuel grades of alcohol are those grades of alcohols that meet the specifications of recognized bodies for use in fuel applications, such as the Brazilian government's ethanol and hydrous ethanol specifications, or any international standards set for fuel use. There are a range of fuel grades of alcohol, which may be alcohols only or hydrous alcohol grades, that may be used as the feed fuel. Hydrous alcohols are those grades specified by recognized bodies with either a water content as specified by that body, or with added water. In some embodiments, such as those embodiments where the feed fuel also comprises lubricity improver, the feed fuel comprises a chemical grade or fuel grade of alcohol, preferably of methanol or ethanol, combined with lubricity improver. The alcohol is preferably a renewably sourced alcohol. The lubricity improver is also preferably a renewably sourced lubricity improver. Ethanol is produced from various renewable raw materials, such as biomass, such assugar cane, wheat and sugar beet, corn and other grains, among other materials. In some embodiments, the methanol is one produced from biomass.

[0173] A range of grades of alcohol including hydrous alcohols have been studied for use in the EPU unit of the preferred embodiments of the invention described above. The results are set out in Table 4 below:Table 4: Feed Fuels and resultant ether produced following catalytic conversion:No. Feed ~ln-Tank ~LHV Ether Indicative NOX Indicative operating Water produced from combustion temperature% wt Gj / mt g / kWhr DegC 1 IMPCA MeOH 0.1 20 DME 2.0 245(IM)2 IM8 incl 8% 8 18.2 DME 1.8 245water (HM)3 Marine C 1.0 19.8 DME 2.0 245MeOH (MCM)4 Hydrous 8 24.4 DEE + 2.1 200Ethanol (HE) minimalethylene5 HM 73.6 8 23.1 DME + DEE + 2.1 220HE 18.4 EMEW 8

[0174] In the above table, the grades of fuels that were studied included the following:

[0175] (1) IMPCA MeOH - methanol meeting the International Methanol Producers & Consumers Association (IMPCA) specifications as in effect in October 2024. This is abbreviated to " IM". Key features of this chemical grade of methanol are as follows (noting that methods of testing are as specified in the IMPCA specifications):Clear appearanceMinimum 99.895% purity (% w / w)Acetone content maximum 30 ppm (mg / kg).Ethanol content maximum 50 ppm (mg / kg)Chloride as Cl- content maximum 0.5ppm (mg / kg) - although note that in blends of water with IMPCA methanol typically take the chloride content of the blend well above this amount.Sulphur - max 0.5 ppm (mg / kg).Acidity as acetic acid - maximum 30 ppm (mg / kg)Iron in solution - maximum 0.1 mg / kg

[0176] (2) IM8 - as per IMPCA methanol specification above, with addition of 8% water by weight. Abbreviated to " HM".

[0177] (3) Marine C MeOH - This refers to the MMC grade ("marine methanol C grade") of bulk methanol supply for shipping, as set out in ISO / CD 6583:2024. Key features of this chemical grade of methanol are as follows:Minimum 99.7% methanol content on a dry basis (wt%)Ethanol content maximum 150ppmAcetone content maximum 30 ppmInorganic chloride content maximum 2.0 ppmSulphur content maximum 10 ppmWater content maximum 0.5 wt% (noting that if combined with water for the feed fuel, the total water content will be higher).

[0178] (4) Hydrous Ethanol - ethanol meeting the specification of Brazilian ethanol supply specification, EHC grade. Key features of this grade of ethanol are as follows:Clear and free from visible impuritiesAlcohol content - 92.5 - 94.6 w / w%Ethanol content - minimum 94.5% by volumeWater content - maximum 7.5% w / w.Chloride content maximum 1 ppm (mg / kg)Sulphur content maximum 4 ppm (mg / kg)Iron content maximum 5 ppm (mg / kg)Sodium content maximum 2 (mg / kg)Methanol content maximum 0.5% by volume.

[0179] (5) A blend containing HM (hydrous methanol, as described in line 2 of the table) and HE (hydrous ethanol as per line 4 of the table) was also studied. " W8" refers to 8% by weight water.

[0180] The fuel composition of some embodiments comprises a lubricity improver. The lubricity improver may be referred to more specifically as an alcohol fuel lubricity improver. The lubricity improver is preferably an organic lubricity improver. According to some embodiments, the lubricity improver is selected from the group consisting of diethanolamine and derivatives thereof, fluorosurfactants, fattyacids (carboxylic acids) and fatty acid esters. The lubricity improver is preferably other than castor oil. The lubricity improver is preferably free of castor oil.

[0181] The lubricity improver is preferably a renewable material. The applicant has sourced a lubricity improver that is produced from renewable materials, such as fatty acids. When the alcohol (such as methanol or ethanol) is also produced from a renewable resource such as biomass, and is itself renewable, then the feed fuel can be produced from entirely renewable resources.

[0182] The amount of lubricity improver may be at least 50ppm or at least lOOppm. The amount of lubricity improver may be within one of the following ranges (by weight): lOOppm - 10,000ppm, lOOppm - 7,500ppm, lOOppm - 5,000ppm, lOOppm - 2,500ppm, lOOppm - 2,000ppm, lOOppm -l,500ppm, 150ppm - 2,000ppm, 150ppm - l,500ppm, 200ppm - 2,000ppm, 200ppm - l,500ppm, lOOppm - l,200ppm, 150ppm - l,200ppm, 200ppm - l,200ppm.

[0183] The feed fuel may comprise a corrosion inhibitor. Corrosion inhibitors are materials that inhibit corrosion of the surfaces within the fuel supply system of an engine. In view of the potential water component in the fuel composition, which may come from the feed fuel or through water by-product produced in the conversion of alcohol to ether, corrosion inhibitor may be a significant addition. Suitable corrosion inhibitors may include amines and ammonium derivatives, among others.

[0184] The amount of corrosion inhibitor may be at least lOppm, when present. The amount may be within one of the following ranges: lOppm - 5,000ppm, lOppm - 2,500ppm, lOppm - 2,000ppm, lOppm - l,500ppm, lOppm - l,000ppm, 50ppm - 2,000ppm, 50ppm - l,500ppm, lOOppm - 2,000ppm or lOOppm - l,500ppm.

[0185] The feed fuel may comprise a feed fuel colour additive. Colour or colloration additives assist to ensure that the fuel composition could not be mistaken for a liquid beverage such as water. Any water soluble colourant may be used, such as a yellow, red, blue, orange or green colourant or a combination of these colourants. The colourant may be a standard accepted industry liquid colourants. The amount of colour additive may be at least lOppm, when present. The amount may be within one of the following ranges: lOppm - 5,000ppm, lOppm - 2,500ppm, lOppm - 2,000ppm, lOppm - l,500ppm, lOppm - l,000ppm, 50ppm - 2,000ppm, 50ppm - l,500ppm, lOOppm - 2,000ppm or lOOppm -l,500ppm.

[0186] The feed fuel colour additive is suitably separated into the residue that remains on separation of the alcohol in the alcohol separation step.

[0187] In embodiments of the invention, the feed fuel comprises methanol and a detectable amount of each of ethanol, acetone, chloride and sulphur. In other embodiments, the feed fuel comprises ethanol and a detectable amount of each of methanol, chloride, sulphur, iron, sodium and methanol.

[0188] The feed fuel may further comprise any other components as desired in the art. An advantage of the processes, systems and uses of embodiments of the present application is that there isaccommodation of a variety of components such that key additives are removed from the stream of the feed fuel directed to the reactor, so that the additives do not impair the reactor performance.

[0189] Components of the feed fuel may include one or more high-boiling point materials with a boiling point higher than 100°C, additional to the lubricity improver. In the process and use, the high-boiling point materials are separated into the residue with the lubricity improver to be separated from the alcohol in the separation step.

[0190] The feed fuel in some embodiments comprises one or more impurities selected from the group consisting of acetone, an alcohol other than methanol and ethanol, sulphur and inorganic matter.

[0191] When present, the water in the feed fuel may come from any suitable source. The water source may introduce impurities into the feed fuel, which can be accommodated in the processes, systems and uses described herein.

[0192] Among the range of additional additives that may be accommodated, there may be mentioned the following. Each of these is preferably not present in an amount exceeding 20%, preferably 15%, 10%, 5%, 2% or 1% of the feed fuel composition. The amount is preferably at least lOppm for each additive that is chosen for inclusion in the composition. The amount of each additive specifically selected for inclusion in the composition may be an amount may be within one of the following ranges: lOppm -5,000ppm, lOppm - 2,500ppm, lOppm - 2,000ppm, lOppm - l,500ppm, lOppm - l,000ppm, 50ppm -2,000ppm, 50ppm - l,500ppm, lOOppm - 2,000ppm or lOOppm - l,500ppm.

[0193] 1. Ignition improver additives. These may also be referred to as ignition enhancers. An ignition improver is a component that promotes the onset of combustion. Molecules of this type are inherently unstable, and this instability leads to "self start" reaction leading to combustion of the main fuel component (for example, methanol). The ignition improver may be selected from materials known in the art to have ignition enhancing properties, such as, ethers (including C1-C6 ethers such as dimethyl ether or diethyl ether), alkyl nitrates, alkyl peroxides, volatile hydrocarbons, oxygenated hydrocarbons, and mixtures thereof.

[0194] 2. Fuel extenders. A fuel extender is a material that provides heat energy to drive the engine. Materials used as fuel extenders may have this purpose as the main purpose for its inclusion in the fuel composition, or an additive material may provide this function and another function. Examples of such Fuel Extenders are: a) Carbohydrates. Carbohydrates include sugars and starch. The carbohydrate may be included for fuel extender purposes, although it may also function as an ignition improver, and / or a combustion improver. The carbohydrate is preferably water / methanol soluble, with higher water levels accommodating greater dissolution of sugar, for example, in the main fuel. An enriched water (single phase) main fuel composition enables dissolution of the carbohydrate, such as sugar, however as the liquid solvent (water / methanol) in the fuel composition evaporates in the engine, the carbohydrate solute can form micro-fine high surface area suspended particles of low LEL (lower explosive limit) composition which will decompose / react under engine conditions, improving the ignitability of the mainfuel mixture, b) Soluble Fuel Extender additives. Fuel extender additives are combustible materials. These additives may be added as separate components or may be part of an undistilled methanol used to produce the main fuel composition. Such additives include C2-C8 alcohols, ethers, ketones, aldehydes, fatty acid esters and mixtures thereof. Fatty acid esters such as fatty acid methyl esters may have a biofuel origin. These may be sourced through any biofuel sources or processes. Typical processes for their production involve transesterification of plant-derived oils, such as rapeseed, palm or soybean oil, amongst others.

[0195] 3. Combustion enhancers. These may also be referred to as combustion improvers. An example of a combustion enhancer is a nitrated ammonium compound, for example ammonium nitrate.

[0196] 4. One or more of: flame colour additives, biocides, oxygen absorbing oils, freeze point depressants, deposit reductants, denaturants and pH control agents. In the case of ethanol as the alcohol, the feed fuel preferably comprises a deposit reductant. Thus, in some embodiments, the feed fuel comprises at least lOppm deposit reductant, and the residue separated from the first stream of the feed fuel comprises deposit reductant in addition to said lubricity improver.

[0197] The feed fuel is suitably a single-phase fuel. The feed fuel is suitably clear and bright. The feed fuel is suitably free of emulsifier and is not in the form of an emulsion. The feed fuel preferably is entirely formed from renewal materials. The feed fuel is suitably a stable fuel composition. A stable fuel composition is one that remains clear and bright after testing for 28 days at 0°C.Main Fuel and Secondary Fuel

[0198] The features of the main fuel and the secondary fuel flow from the features of the feed fuel.

[0199] In relation to the main fuel, in some embodiments, the composition of the main fuel is similar to that of the feed fuel, but with the addition of the residue from the alcohol separation step. Consequently, the main fuel suitably comprises alcohol, preferably methanol and / or ethanol, lubricity improver, and any of the additional additives referred to above in the context of the feed fuel composition. The amount of lubricity improver is preferably higher than is present in the main fuel. However, since only a small amount of main fuel is sent to the ether processing unit for conversion of the alcohol to ether, and only a small proportion of that stream is separated into a residue portion, the adjustment amount is relatively small. Using the example of a feed fuel comprising 1000ppm lubricity improver, the increased amount present in the main fuel may be in the region of 1-20% higher than the feed fuel amount, and may therefore be in the region of a lOppm - 200ppm increase, for a total amount in the region of l,010ppm - l,200ppm. If the lubricity improver amount in the feed fuel is within a broader range in the feed fuel (e.g. the range of lOOppm - 10,000ppm), allowing for the residue stream return, the main fuel may comprise lOlppm - 12,000ppm lubricity improver, with the proviso that the amount is higher than is present in the feed fuel.

[0200] Even if the feed fuel does not contain significant water, in view of the recycle streams and the recovery of water byproduct from the conversion of alcohol to ether, the main fuel typically will comprise water. The amount of water in the main fuel is higher than the amount of water in the feed fuel. The amount is typically at least 0.5% by weight, for example at least 1%, at least 2%, at least 3%, at least 4% or at least 5% by weight, in the main fuel composition.

[0201] It is a feature of a class of fuels developed by the applicant, referred to as " Gane fuel", that the fuel comprises a significant water content. The applicant has previously demonstrated the efficacy of its fuel compositions for use in compression ignition engines, with favourable low NOX emissions, and high break thermal efficiency. Accordingly, it is preferred that the main fuel comprises water, and further, the feed fuel preferably also comprises water to achieve a significant water content in the main fuel.

[0202] In preferred embodiments, the feed fuel comprises from 0.2% to 30% by weight water, or an amount of water (by weight) within one of the following ranges: 0.5-30%; 0.8-30%; 1-30%, 2-30%; 3-30%, 4-30%, 5-30%, 0.2-20%, 0.5-20%, 0.8-20%; 1-20%, 2-20%; 3-20%, 4-20%, 5-20%, 0.2-15%, 0.5-15%, 0.8-15%; 1-15%, 2-15%; 3-15%, 4-15% or 5-15%. In preferred embodiments, the main fuel comprises an amount of water (by weight) within one of the following ranges: 0.5-30%; 0.8-30%; 1-30%, 2-30%; 3-30%, 4-30%, 5-30%, 0.5-20%, 0.8-20%; 1-20%, 2-20%; 3-20%, 4-20%, 5-20%, 0.5-15%, 0.8-15%; 1-15%, 2-15%; 3-15%, 4-15% or 5-15%.

[0203] The secondary fuel comprises ether. The ether is preferably dimethyl ether or diethyl ether or a combination thereof. The secondary fuel may also comprise ethyl methyl ether (EME), particularly if the alcohol in the feed fuel comprises methanol and ethanol. The ether content of the secondary fuel may in some embodiments be between 60% and 97% of the secondary fuel.Catalyst

[0204] The catalyst for use in the dehydration of the alcohol to an ether may be any of the alcohol dehydration catalysts known in the art. The catalyst is suitably a solid catalyst. The catalyst is suitably a solid-acid catalyst. Suitable catalyst classes that may be used include zeolites, alumina (e.g. y-AI2O3) and zirconia. The catalyst may be a modified catalyst. For example, the modified catalyst may be modified with silica and / or phosphorous. One particular subclass is the modified alumina catalyst class, which includes Al2O3–B2O3as one example. The catalyst may be an amorphous catalyst. The catalyst is preferably a zeolite catalyst. Zeolites are minerals based on hydrated aluminosilicates of sodium, potassium, calcium and / or barium. Suitable catalysts are available from commercial catalyst suppliers, including BASF among others.

[0205] Properties of the catalyst useful for reliable longer-term use include the following:(a) hardness to prevent excess fines generation;(b) operation at reduced temperature to limit wear caused by repeated expansion and contraction; (c) high water tolerance; and / or(d) high capability to handle multiple regeneration cycles with return to good recovery of activity.Regeneration may require removal of coke and / or sulphur.

[0206] Catalyst conversion naturally decreases over time with aging, and degradation can be accelerated in the event of excessive temperatures, temperature fluctuations causing mechanical degradation, and the impact of water, among other things. A service life of about two years is typical for a number of industrial catalyst applications. Start of run and end of run conversion targets may be defined for the catalyst, leading to a total required catalyst inventory (CInv), and when the conversion falls below the end of run level it is time to regenerate the catalyst. If catalyst activity cannot be recovered, the catalyst may be replaced.

[0207] A back-up catalyst may also be added into the system. The amount of back-up catalyst may be in the amount of between 5% and 100% of CInvto ensure minimum conversion levels are achieved between maintenance periods.

[0208] The fuel composition is for the complete replacement of traditional diesel fuel in compression ignition engines.EXAMPLES

[0209] A number of experiments were undertaken to demonstrate the efficacy of various aspects of the present application and some preferred embodiments,

[0210] In the examples, reference is made to " Gane fuel", which for the purposes of the examples, is defined as system comprising a feed fuel comprising methanol, water and lubricity improver, which is used in the production of a main fuel also comprising methanol, water and lubricity improver, and a secondary fuel comprising DME, those two fuel compositions then constituting the fuel system for fueling an engine.1.1 Gane Fuel Tested Blend

[0211] One blend of feed fuel comprising 89.7% methanol, 10.2% water and l,000ppm lubricity improver was subjected to preliminary testing to determine the fuel properties. The results are shown in Table 5 below:Table 5: Fuel properties of the tested blend.Property Unit ResultUHV MJ / kg 20.4LHV MJ / kg 17.7Density@15C kg / l 0.8256Density@20C kg / l 0.8214Density@25C kg / l 0.8171%Carbon %m 33.7%Hydrogen %m 12.4%Oxygen %m 53.9MW g / mol 29.7Water %m 10.2Methanol %m 89.7Lubricity Gane fuel@25C HFRR um 220Lubricity Diesel fuel@25C HFRR um 250Lubricity Diesel fuel@60C HFRR um 440NACE Rust Test TM-01-72 Rating B++1.1.1 DME-based secondary fuel

[0212] The use of a secondary fuel comprising ether, in the case of the examples, DME, is central to the performance of the Gane fuel as a feed fuel (and main fuel) for compression ignition engine operation. DME has excellent ability to trigger ignition of high pressure injected low cetane methanol / water, even under conditions of extreme dilution at high lambda high rpm and low load. Bench testing on a turbocharged 12 litre diesel engine for Gane Energy by IAV GmbH in Berlin demonstrated the efficacy of DME in meeting its task to ignite a 90 / 10 methanol / water mix across the full engine map. (See Figure 3.)

[0213] Figure 3 demonstrates the capability of a secondary fuel comprising a high percentage of DME (in this case, 100% DME) to ignite a main fuel in the form of Gane fuel which included 10% water, across the full map. Points of note are the following:The DME as a proportion of total mass flow into the engine was less than 1.0% by mass, at any point of the map.On the full load curve, the % DME required was approximately 0.2% by mass from 1500 to 1900 rpm, 0.3% by mass from 1000 to 1400 rpm and from 0.8% by mass to 0.5% by mass from 650 rpm to 900 rpm.Stable combustion was achieved at all load points tested on the map.The highest DM E flow was required at high RPM and low load.The % of DME required to achieve ignition is well below the lower flammability limit of DME in air, which is 3.4% by vol or 5.3 % by mass.

[0214] A second fuel composition was tested with 82% by weight methanol and 18% by weight water using DME as the secondary fuel, with no difficulty experienced.

[0215] In addition to the points listed above, DME can contribute to improved diesel engine operation as demonstrated below.

[0216] DME use as fumigant (secondary fuel) may be further reduced compared to what is shown in Figure 3 by incorporating additional steps as follows:Using air temperature adjustment under appropriate load conditions to reduce DME flow into the engine, in some cases to zero.Injecting as fumigant an appropriate mixture comprising DME and methanol to reduce the engine's need for DME.1.1.2 Methanol as the alcohol in the feed fuel and main fuel

[0217] Of the alcohols that may be used in the feed fuel and main fuel, methanol has some unique properties that are advantageous in the processes and uses of the present application:- Methanol has a strong affinity with water. This interaction results in shrinkage of the overall volume when water is added to methanol to a point of maximum density, after which shrinkage declines as additional water is added.- When DME of lower polarity is added to the methanol water mixture, the ternary solution is less accommodating of DME in the liquid, increasing vapour pressure of the mixture nonlinearity with respect to DME.- Has high octane sensitivity, demonstrating its stability and resistance to ignition under mild stress while showing increasing willingness to ignite and combust as thermal and free radical conditions gain strength. Such behaviour is a good match with Gane fuel HCCI combustion of DME controlling ignition, with mild ignition of dilute DME acting as ignitor of the high pressure injected fuel late in compression stroke. Such an approach enables high or low compression ratio engines to be used with appropriate dosage and purity of DME as secondary fuel.- Methanol has the most favourable carbon reduction (at the same efficiency) compared to diesel and other alcohols including ethanol. See Table 6 below:Table 6: Fuel carbon fraction vs. DieselFuel Units MeOH Diesel Gane fuel (10%W) carbon fraction wt / wt 0.375 0.859 0.337LHV gj / mt 20 42.74 17.7carbon % / LHV % / Gj 1.88 2.01 1.90Carbon comparison (Diesel = 100) 93.3 100.0 94.7Carbon reduction % vs diesel -6.7 0.0 -5.3

[0218] Table 6 shows that at the same BTE, methanol has a 6.7% carbon reduction compared to diesel, and Gane fuel with 10% water, has 5.3% carbon reduction compared to diesel.1.1.3 Water component of feed fuel

[0219] Water and methanol have a high degree of compatibility at all concentrations, each molecule though small, has high polarity with correspondingly high boiling points. The result is a mixture that does not require pressurisation or refrigeration to remain a liquid under ambient conditions.

[0220] It may be expected that water would have a negative effect on engine efficiency at all concentrations, soaking up sensible and evaporative heat out of the combusting fuel air mixture and lowering in-cylinder combustion temperature. Such expectations of negative impact on efficiency are true in many circumstances but not all.

[0221] It has previously been demonstrated that including water in fuel fed to a compression ignition engine under high pressure, and igniting the main fuel mixture along with secondary fuel (comprising DME in the manner of a fumigant) leads to definite reduction in NOx and can simultaneously lead to an increase in BTE.

[0222] While some applications such as ships have ready access to water using desalination techniques, some other applications do not, being remote from any water source. In such cases the feed fuel (and correspondingly the main fuel) will source water from other means including recovery of dehydration reaction water or use of co-produced water with fuel methanol production. It may not be economical to create a separate purified water supply chain to blend with methanol.2.1 Testing of secondary fuel compositions, produced from feed fuel in the EPU, as fumigants into an engine with a methanol-water main fuel composition2.1.1 Secondary fuel compositions and phase control

[0223] In Table 7, a number of secondary fuel compositions that may be produced in the EPU from a methanol-based feed fuel (in accordance with the processes of the present application) are presented. To produce the "high" fumigant purity secondary fuel, the reactor output is subjected to the condensation and separation procedures to increase the ether content to the "high" range of 90-97%. This will typically require at least two stages of partial condensation, with each stage effecting an increase in the % ether content in the ether-enriched stream. Using these stages of partial condensation and separation, it is possible to increase the ether content of the ether-rich stream to as high as about 97% ether (with 0.5 wt% water and 2.5 wt% methanol remaining). A "medium" fumigant purity secondary fuel can be produced by subjecting the reactor output to condensation and separation procedures, albeit with a lower extent of removal of the unreacted methanol and water byproduct. Similarly, a "lower" fumigant purity secondary fuel can be produced with less removal of the unreacted methanol and water byproduct. The reactor output at 80% conversion delivers an initial composition containing 52% DME, 30% water and 18% methanol, so this guides the extent of removal of water and methanol that is required in the subsequent processing steps to increase the secondary fuel (fumigant) purity to come within the low, medium and high purity ranges. Similarly, for a reactor output at 64% conversion, a greater amount of the remaining unreacted methanol and water needs to be removed.Table 7: Secondary fuel compositions for ignition of methanol-water main fuelFumigant Purity DME Water MeOHrange %High 90- 97 0.5-4 2.5 - 6Medium 75 - 89 4 - 10 7 - 15Low 60 - 74 10 - 20 16 - 20Reactor Out 80% conversion 52 *30 *18Reactor Out 64% conversion 4226 32

[0224] Liquid and gaseous systems for the delivery of secondary fuel comprising or consisting of DME have been examined using process simulation. Gas and liquid phase injection of the secondary fuel are both options, each having advantages and disadvantages. Currently, the liquid injection option is preferred due to its fewer hardware and control challenges.2.1.2 Secondary fuel injection options - blending

[0225] There is the option to blend some of the feed fuel with the secondary fuel produced in the process, and using that blend for fumigation into an engine. If the secondary fuel produced in accordance with the process as described above is a very high purity secondary fuel - containing in this example 97% ether, 0.5 wt% water and 2.5 wt% methanol - then when bended with different amounts of Gane fuel as feed fuel, the final fumigant composition (comprising the secondary fuel and feed fuel blend) is still of a sufficiently high ether content to suit the fumigation process.

[0226] In table 8 a number of blends are demonstrated. Referring to the line "nil Gane fuel" - it is shown that the overall fumigant blend comprises 100% of the secondary fuel (with 97% DME), and 0% Gane fuel. Referring to the "high" line of the table, it can be seen that if 92.8% of the secondary fuel (which has 97% DME) is blended with 7.2% Gane fuel, then the blend still contains 90% DME, which is within the "high" DME range composition indicated in Table 7 (the 90-97% range). As shown in the "medium" row, a medium DME-content blend (within the 75 - 89% range) can be produced by blending 22.7% Gane fuel with 77.3% of 97% DME secondary fuel. That blend can then be fumigated into the engine.

[0227] Overall, these examples demonstrate the flexibility that is available for creating different qualities of fumigant. See Table 8 below.Table 8: Fumigants from blends of secondary fuel comprising 97% DME with Gane fuelQuality % Base % Gane DME Water MeOHDME fuel %m %m %mfumigant 10%waterGane fuel 0 10 9097 0.5 2.5Base Fumigant,highest DMEresultantfumigantnil Gane fuel 100 0 97 0.5 2.5high 92.8 7.2 90.0 1.2 8.8medium 77.3 22.7 75.0 2.7 22.4low 61.9 38.1 60.0 4.1 35.9

[0228] If the blending option is adopted, with a consequent reduction in the DME content of the fumigant and increase in the water content of the fumigant, the following effects may be observed:Lowering fumigant ignitability due to less DM E, higher heat of evaporation and vapour heat capacity; More water liquid injected during upstroke; andDelayed ignition of the fumigant, providing opportunity for favorable ignition timing of the resulting fumigant mixture.

[0229] The use of high purity DME (about 97%) as the secondary fuel, as produced in the EPU, provides a good gradient for control of the blending of Gane fuel into the fumigant mixture and consequently the ignition of secondary fuel (i.e. fumigant). The Gane fuel added to fumigant can be changed suddenly if required to match engine requirements, without the need for slower process adjustments.

[0230] The use of lower "quality" fumigant (compared to the 97% example provided above) is also possible. This can be achieved by blending of Gane fuel with a higher quality secondary fuel (e.g. 97% DME content secondary fuel), or creating a lower DME-content secondary fuel from the outset, by using higher flow rate of alcohol through the reactor (i.e. lower conversion of alcohol to ether) to meet the ignition requirements of the engine.

[0231] Three modes for the use of fumigant were considered:

[0232] (1) Run a consistently higher fumigant flow into the engine, as compared to the minimum that the engine requires. This approach would generate higher emissions lower efficiency and use more DME than necessary. While this means that the engine can be operated without finer fumigant volume control, this operating mode is not preferred.

[0233] (2) Control the fumigant flow into the engine as required. For example, if:" PD" means " Produced DME baseline of consistent quality";" GF" means Gane fuel,x = required flow of PD, andy = required flow of GF for a given load point, then:Total fumigant = x + y, with the objective being to minimize x.

[0234] (3) As per (2) above, but with PD also variable with a slower rate of change, to reflect the slower reaction time of the DPU process compared to the engine demand.

[0235] Each engine will require calibration and optimization of these parameters to determine the best quality PD, either static or variable, and x and y values for a given engine operation.

[0236] Highly loaded engines such as those that drive container ships should be able to minimize DME use and maximize the Gane fuel content of the fumigant blend.2.1.3 DPU Process Simulation Results

[0237] The qualities the DPU input and output streams achieved during simulation runs are shown in Tables 9 and 10.Table 9: High DME conversion (80%)Stream MeOH Water DME RVP (kPa)% m % m % mFuel Feed ex Tank 91.9 8.0 0 32DME fumigant to Engine 2.8 0.5 96.7Fuel to Engine High Pressure 88.8 11.1 0 31PumpTable 10: Low DME Conversion (64%)Stream MeOH Water DME RVP (kPa)% m % m % mFuel Feed ex Tank 91.9 8.0 0 32DME fumigant to Engine 3.5 0.3 96.2Fuel to Engine High Pressure 88.8 11.1 0 31Pump

[0238] It can be seen that the DME fumigant quality changes to a small extent, falling from 96.7% to 96.2%, and water decreases from 0.5 to 0.3%. At lower conversion, the methanol content of fumigant increased by 0.7%, from 2.8% to 3.5%.

[0239] Other points of note from the above tables are:The water content of feed to the high pressure pump increased by 3% compared to the Gane fuel feed, rising from 8 % to 11% by weight. This water increase was due to:o A concentration of water in feed to the high pressure pump due to the concentrating effect of removing an essentially water-free fumigant stream; ando Recovery of dehydration reaction water to high pressure pump (HPP) feed.The RVP (Reid Vapour Pressure) of feed to the HPP was a little lower that Gane fuel feed due to: o Displacement of methanol by water due to inclusion of dehydration water; ando Effective removal of DME from dehydration water prior to its inclusion with HPP feed.

[0240] As a result of the process simulations, the following points can be a stated regarding the design of the ether processing unit (DPU):Running high purity chemical grade methanol feedstocks was not the design target of the DPU. The DPU can accommodate a range of Gane feed fuel qualities while producing the required secondary fuel (fumigant) for main fuel ignition.Variable catalyst conversion levels can be accepted while producing the required fumigant without the production of unwanted by products.The fuel volatility into the high pressure pump can be reduced to a small extent due to the added presence of co-produced water in the fuel directed to the HPP, accompanied by trace amounts of DME.3.1 Engine Testing

[0241] Engine tests have been performed using Gane fuel, and with inlet air fumigation with secondary fuel comprising dimethyl ether as the ether. Figure 3 demonstrates the capability of a secondary fuel comprising a high percentage of DME (in this case, 100% DME) to ignite a main fuel in the form of Gane fuel which included 10% water, across the full engine map.4.1 Lubricity Improver Tests4.1.1 Stability

[0242] Stability tests were performed on a range of fuel compositions comprising methanol (approx.80-100%), water (approx.0-20%), and a lubricity improver (0 or 1000ppm) supplied by Infineum. The tested fuel compositions were found to be stable over a range of temperatures from -15°C to 20°C and for extended periods of time (up to 28 days of testing). The tested fuel compositions remained "clear and bright", without sedimentation, at those temperatures across the 28 day testing period.4.1.2 HFRR Test

[0243] A high frequency reciprocating rig (HFRR) test was conducted to check the lubricity of the tested main fuel compositions. This test work was based on ISO12156 (Assessment of lubricity of diesel fuel). The outcome of the HFRR test work indicated that the tested methanol-based fuel compositions containing varying amounts of methanol (approx. 80-100%) and water (approx.0-20%), and with 1000ppm lubricity additive, resulted in significantly reduced HFRR wear scars as compared to the corresponding fuel samples that were free of the lubricity additive.Observations

[0244] Methanol-based Gane fuel has been extensively tested in a 12 litre Cl engine with engine performance comparable to diesel fuel.

[0245] Emissions of key pollutants such as Pm, Pn, NOx and soot were substantially reduced or eliminated. Unburnt species were effectively removed with the use of an oxidation catalyst.

[0246] DME can be made from methanol dehydration unit using a portion of the methanol in Gane fuel to ignite the high pressure fuel injected into the engine. The DPU can deliver high target DME purity.

[0247] The DPU does not require chemical grade methanol. The process and system developed and described herein allows for the feed fuel to contain high water levels and the presence of other species such as lubricity improver, and for removal of such components to an acceptable level to allow the DPU to produce DME from the methanol.

[0248] Acceptable engine operation was achieved at all load points in seven standard emissions cycles, including three transient cycles.

[0249] The engine testing included the use of a lubricity improver in the fuel, which demonstrated its effectiveness over a range of fuel water contents to 20%.

[0250] 28-day additive stability test demonstrated that the addition of 1000ppm lubricity improver did not adversely impact the stability of the tested fuels (with methanol 80-100% and water 0-20%), at temperatures down to -15°C.

[0251] Various modifications can be made to the embodiments described above, without varying from the spirit and scope of the inventions described herein.ITEMS1. A process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel comprising alcohol, the process comprising:- storing the feed fuel in a feed fuel tank;- directing a first stream of the feed fuel from the feed fuel tank to a heater and heating the first stream of feed fuel to evaporate alcohol in the feed fuel;- optionally separating a liquid residue from the evaporated alcohol;- producing main fuel from a second stream of the feed fuel;- directing the evaporated alcohol to a reactor and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water; - condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output;- producing secondary fuel from the ether-concentrated portion of the reactor output; and- combining the separated unreacted alcohol and water with one or more of:(i) the first stream of the feed fuel upstream of said heating step or upstream or at said liquid residue separation; or(ii) the reactor output upstream of the condensation of the reactor output, or(iii) the second stream of the feed fuel for incorporation as a component of the main fuel.2. A process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel comprising alcohol, the process comprising:- storing the feed fuel in a feed fuel tank;- directing a first stream of the feed fuel from the feed fuel tank to a heater and heating the first stream of feed fuel to evaporate alcohol in the feed fuel;- optionally directing the heated first stream of the feed fuel to a separator and separating the evaporated alcohol from a liquid residue;- producing main fuel from a second stream of the feed fuel- directing the evaporated alcohol to a reactor and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water;- condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output; and- producing secondary fuel from the ether-concentrated portion of the reactor output; and- directing the separated unreacted alcohol and water to (i) the first stream of the feed fuel upstream of said heating step or upstream of, or at, said liquid residue separation; or (ii) directing said separated liquid product to be combined with the reactor output, upstream of the condensation step, or (iii) directing said separated liquid product to a second stream of the feed fuel for incorporation as a component of the main fuel.3. The process of item 1 or item 2, comprising conducting the step of separating the liquid residue from the evaporated alcohol, and combining the separated unreacted alcohol and water to the first stream of the feed fuel upstream of the separation of the liquid residue from the evaporated alcohol. 4. The process of any one of items 1 to 3, wherein the step of condensing the reactor output comprises at least two stages of condensation, including a first partial condensation step and a second partial condensation step, and wherein:- in the first partial condensation step a first partial condensation liquid product comprising alcohol and water is condensed and separated from an ether-concentrated vapour, and- in the second partial condensation step, a second partial condensation liquid product comprising methanol, water and ether is condensed and separated from a second concentrated ether vapour.5. The process of item 4, wherein the second partial condensation liquid product is combined with the reactor output upstream of said first partial condensation step, or is combined with the partially condensed stream downstream of the first stage partial condenser.6. The process of item 5, wherein the first partial condensation liquid product constitutes said separated unreacted alcohol and water that is combined with either (i) the first stream of the feed fuel prior to or upstream of said heating step, or (ii) the reactor output upstream of the condensation step, or (iii) the second stream of the feed fuel for incorporation as a component of the main fuel.7. The process of any one of items 1 to 6, further comprising:- directing the main fuel to an engine for direct injection into a cylinder of the engine;- either combining the secondary fuel with air and directing the combination into the air intake of an engine, or directly injecting secondary fuel into a cylinder of an engine.8. The process of item 7, further comprising:- receiving engine exhaust from an engine and using heat from the engine exhaust for heating the first stream of feed fuel in a heater prior to or upstream of said separating of the alcohol from the liquid residue.9. The process of item 8, wherein the step of receiving engine exhaust from an engine and using heat from the engine exhaust for said heating of the first stream of feed fuel comprises:- receiving engine exhaust from the engine into an oil heater;- exchanging heat from the engine exhaust into oil circulating in the oil heater to raise a temperature of the oil circulating in the heater,- pumping the oil from the oil heater to said heater where the first stream of the feed fuel is heated; and - exchanging heat from the oil into the feed fuel in the heater.10. The process of item 9, exchanging heat from the oil into the feed fuel in the heater to raise the temperature of the feed fuel to a temperature above the boiling point of the alcohol present in the feed fuel.11. The process of any one of items 1 to 10, further comprising superheating the vaporised alcohol (e.g. alcohol separated from the residue in the alcohol separation step), prior to delivery of the superheated vaporised alcohol to the reactor.12. The process of any one of items 1 to 11, further comprising:- storing the secondary fuel comprising ether in a secondary fuel storage tank;- flushing the reactor with ether vapour from the secondary fuel storage tank to flush water byproduct from the reactor to protect catalyst in the reactor from the impact of extended water contact.13. The process of item 12, wherein the ether is conveyed to the reactor via a superheater, such that the ether vapour flows through the alcohol superheater then through the reactor.14. The process of any one of items 1 to 13, further comprising:- receiving data indicative of an unacceptable temperature in the reactor; and- performing one or more of the following steps, based on the data, to bring the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing the temperature of feed material fed into the reactor, said feed material comprising the alcohol evaporated from the first stream of feed fuel (and optionally separated from the residue);- changing the residence time of the feed material fed into the reactor; and- increasing the water content of the feed material fed into the reactor.15. The process of any one of items 1 to 14, wherein the reactor comprises a series of at least two reactors, including a first reactor and a second reactor, and catalytic conversion of alcohol to an ether takes place progressively through each reactor in series.16. The process of item 15, wherein a residence time of fluid fed through each reactor in the series of reactors increases from one reactor to the following reactor in the series.17. The process of item 15 or item 16, wherein an intercooler is positioned between two sequential reactors in the series, and the process comprises intercooling between the sequential reactors.18. The process of any one of items 1 to 17, wherein the feed fuel comprises said alcohol, between 0 and 30% by weight water, and at least 100ppm (on a weight basis) of a lubricity improver.19. The process of item 18, wherein the feed fuel comprises at least 10ppm corrosion inhibitor and / or a feed fuel colour additive, and wherein the liquid residue separated from the first stream of the feed fuel comprises corrosion inhibitor and / or feed fuel colour additive in addition to said lubricity improver.20. The process of any one of items 18 to 19, wherein:the feed fuel comprises from 0.5% to 30% by weight water, or an amount of water (by weight) within one of the following ranges: 0.8-30%; 1-30%, 2-30%; 3-30%, 4-30%, 5-30%, 0.5-20%, 0.8-20%; 1-20%, 2-20%; 3-20%, 4-20%, 5-20%, 0.5-15%, 0.8-15%; 1-15%, 2-15%; 3-15%, 4-15% or 5-15%;and wherein the residue separated from the first stream of the feed fuel comprises water in addition to said lubricity improver.21. The process of any one of items 18 to 20, wherein the alcohol in the feed fuel comprises methanol.22. The process of any one of items 18 to 21, wherein the alcohol in the feed fuel comprises ethanol.23. The process of any one of items 18 to 22, wherein the ether is dimethyl ether or diethyl ether.24. The process of any one of items 18 to 23, wherein the feed fuel comprises one or more high-boiling point materials with a boiling point higher than 100°C, other than the lubricity improver, and the high-boiling point materials are separated into the residue with the lubricity improver to be separated from the alcohol in the separation step.25. The process of item 24, wherein the feed fuel comprises one or more impurities selected from the group consisting of acetone, an alcohol other than methanol and ethanol, sulphur, inorganic matter.26. The process of item 1, comprising conducting the step of separating the liquid residue from the evaporated alcohol, and combining the separated unreacted alcohol and water with the first stream of the feed fuel upstream of the separation of the liquid residue from the evaporated alcohol. 27. The process any one of items 1 to 26, wherein the step of separating the liquid product comprising unreacted alcohol and water from the ether-concentrated vapour comprises flash separation.28. The process of any one of items 1 to 27, wherein the ether content of the reactor output is less than 55 wt% ether.29. The process of any one of items 1 to 28, wherein the ether content of the secondary fuel (or the ether-concentrated vapour produced following the condensation and separation steps performed on the reactor output) is between 60wt% and 97 wt%, or between 60 wt% and 89 wt%, or between 60wt% and 74 wt%, or between 75wt% and 97 wt%, or between 75 wt% and 89wt%, or between 90 and 97 wt%. 30. The process of item 28 or item 29, wherein the ether content of the secondary fuel (or the ether-concentrated vapour) is at least 20%, or at least 40% or at least 60% or at least 70% higher than the ether content of the reactor output.31. The process of any one of items 28 to 30, wherein the secondary fuel is directed to an engine and has an ether concentration on delivery to the engine of between 60wt% and 97 wt%, or between 60 wt% and 89 wt%, or between 60wt% and 74 wt%, or between 75wt% and 97 wt%, or between 75 wt% and 89wt%, or between 90 and 97 wt%.32. The process of any one of items 1 to 5, wherein the process is conducted in a mobile operation.33. The process of any one of the preceding items, wherein the process is a closed-loop process. 34. A process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel, the process comprising:- storing a feed fuel in a feed fuel tank, the feed fuel comprising an alcohol, between 0 and 30% by weight water, and at least 50 ppm (on a weight basis) of a lubricity improver;- directing a first stream of the feed fuel to a heater for heating of the first stream of the feed fuel;- evaporating alcohol from the first stream of feed fuel and separating a residue therefrom, the residue comprising lubricity improver;- directing the alcohol separated from the residue to a reactor, catalytically converting the alcohol to an ether, and producing the secondary fuel from the ether;- combining the residue separated from the evaporated alcohol with a second stream of the feed fuel to produce the main fuel;- directing the main fuel to an engine for fueling the engine; and- directing the secondary fuel to an engine separately to the main fuel.35. The process of item 34, comprising- using heat from an engine exhaust for said heating of the first stream of feed fuel.36. The process of item 34, wherein the secondary fuel is combined with air and directed into the air intake of an engine or is directly injected into a cylinder of an engine.37. The process of item 34, wherein the secondary fuel is combined with air and directed into the air intake of an engine.38. The process of any one of items 34 to 37, wherein the step of receiving engine exhaust from an engine and using heat from the engine exhaust for said heating of the first stream of feed fuel comprises: - receiving engine exhaust from the engine into an oil heater;- exchanging heat from the engine exhaust into oil circulating in the oil heater to raise a temperature of the oil circulating in the oil heater, and- pumping the oil from the oil heater to said heater where the first stream of the feed fuel is heated; - exchanging heat from the oil into the feed fuel in the heater.39. The process of item 38, exchanging heat from the oil into the feed fuel in the heater to raise the temperature of the feed fuel to a temperature above the boiling point of the alcohol present in the feed fuel.40. The process of any one of items 34 to 39, further comprising superheating the alcohol separated from the residue in the alcohol separation step, prior to delivery of the superheated separated alcohol to the reactor.41. The process of any one of items 34 to 40, wherein a reactor output of the reactor comprises ether, water, and unreacted alcohol, and the process further comprises:- condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output; and- producing the secondary fuel from the ether-concentrated portion of the reactor output.42. The process of item 41, comprising:- directing the separated unreacted alcohol and water to the first stream of the feed fuel for combination with the first stream of the feed fuel prior to delivery of the first stream of the feed fuel to the heater, or directing said separated liquid product to be combined with the reactor output prior to the condensation step, or directing said separated liquid product to a second stream of the feed fuel for incorporation as a component of the main fuel.43. The process of item 41, comprising:- directing the separated unreacted alcohol and water to the first stream of the feed fuel for combination with the first stream of the feed fuel prior to delivery of the first stream of the feed fuel to the heater.44. The process of any one of items 41 or item 43, wherein the step of condensing the reactor output comprises at least two stages of condensation, including a first partial condensation step and a second partial condensation step, and wherein:- in the first partial condensation step a first partial condensation liquid product comprising alcohol and water, and a first percentage of ether, is condensed and separated from an ether-concentrated vapour, and- in the second partial condensation step performed on the ether-concentrated vapour, a second partial condensation liquid product comprising methanol, water and a second percentage of ether is condensed and separated from a second concentrated ether vapour, wherein the second percentage of ether is higher than the first percentage of ether.45. The process of item 44, wherein the second partial condensation liquid product is combined with the reactor output prior to said first partial condensation step and the first partial condensation step isperformed on the combination of the reactor output and the second partial condensation liquid product, or the second partial condensation liquid product is combined with the partially condensed stream exiting the first stage partial condenser.46. The process of item 45, wherein the first partial condensation liquid product constitutes said separated unreacted alcohol and water that is directed to the first stream of the feed fuel prior to said feed fuel heating step.47. The process of any one of items 34 to 46, further comprising:- storing the secondary fuel comprising ether produced in the reactor in a secondary fuel storage tank; - flushing the reactor with ether vapour from the secondary fuel storage tank to flush water byproduct from the reactor to protect catalyst in the reactor from the impact of extended water contact.48. The process of item 47, wherein the ether is conveyed to the reactor via an alcohol superheater, such that the ether vapour flows through the alcohol superheater then through the reactor.49. The process of any one of items 34 to 48, further comprising:- receiving data indicative of an unacceptable temperature in the reactor; and- performing one or more of the following steps, based on the data, to return the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing the temperature of feed material fed into the reactor, said feed material comprising the alcohol evaporated from the first stream of feed fuel and separated from the residue;- changing the residence time of the feed material fed into the reactor; and- increasing the water content of the feed material fed into the reactor.50. The process of any one of items 34 to 49, wherein the reactor comprises a series of at least two reactors, including a first reactor and a second reactor, and catalytic conversion of alcohol to an ether takes place progressively through each reactor in series.51. The process of item 50, wherein a residence time of fluid fed through each reactor in the series of reactors increases from one reactor to the following reactor in the series.52. The process of item 50 or item 51, wherein an intercooler is positioned between two sequential reactors in the series, and the process comprises intercooling between the sequential reactors.53. The process of any one of items 34 to 52, wherein the feed fuel comprises at least 10ppm corrosion inhibitor and / or a feed fuel colour additive, and wherein the residue separated from the first stream of the feed fuel comprises corrosion inhibitor and / or feed fuel colour additive in addition to said lubricity improver.54. The process of any one of items 34 to 53, wherein:the feed fuel comprises from 0.5% to 30% by weight water, or an amount of water (by weight) within one of the following ranges: 0.8-30%; 1-30%, 2-30%; 3-30%, 4-30%, 5-30%, 0.5-20%, 0.8-20%; 1-20%, 2-20%; 3-20%, 4-20%, 5-20%, 0.5-15%, 0.8-15%; 1-15%, 2-15%; 3-15%, 4-15% or 5-15%;and wherein the residue separated from the first stream of the feed fuel comprises water in addition to said lubricity improver.55. The process of any one of items 34 to 54, wherein the alcohol in the feed fuel comprises methanol.56. The process of any one of items 34 to 55, wherein the alcohol in the feed fuel comprises ethanol.57. The process of any one of items 34 to 56, wherein the ether is dimethyl ether or diethyl ether.58. The process of any one of items 34 to 57, wherein the feed fuel comprises one or more high-boiling point materials with a boiling point higher than 100°C, other than the lubricity improver, and the high-boiling point materials are separated into the residue with the lubricity improver to be separated from the alcohol in the separation step.59. The process of item 58, wherein the feed fuel comprises one or more impurities selected from the group consisting of acetone, an alcohol other than methanol and ethanol, sulphur and inorganic matter.60. A process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel using a catalyst, the process comprising:- storing a feed fuel comprising alcohol in a feed fuel tank;- vaporising alcohol in a first stream of the feed fuel taken from the feed fuel tank;- directing the vaporised alcohol to a reactor comprising the catalyst and catalytically converting the alcohol to an ether and a water byproduct;- storing the ether in an ether storage tank;- flushing the reactor with ether from the ether storage tank to flush water byproduct from the reactor; - producing main fuel from a second stream of the feed fuel, and- producing secondary fuel from the ether produced in the reactor.61. The process of item 60, wherein the step of vaporising alcohol in the first stream of the feed fuel comprises heating the feed fuel to raise the temperature of the feed fuel to a temperature above the boiling point of the alcohol present in the feed fuel and directing the heated first stream of the feed fuel to a separator to separate the vaporised alcohol from a liquid residue.62. The process of item 60 or 61, wherein the ether is flushed through the reactor in vapour form.63. The process of any one of items 60 to 62, wherein the flushing of the reactor with ether is conducted prior to shutdown of the reactor.64. The process of any one of items 60 to 63, further comprising:- receiving data indicative of water accumulation in the reactor; and- purging the reactor with ether, based on the data, to reduce the presence of water in the reactor. 65. The process of any one of items 60 to 64, wherein the ether is conveyed to the reactor via a superheater, such that the ether flows through the superheater then through the reactor.66. The process of any one of items 60 to 65, further comprising:- directing the main fuel to an engine for direct injection into a cylinder of the engine;- either combining the secondary fuel with air and directing the combination into the air intake of an engine, or directly injecting secondary fuel into a cylinder of an engine; and- receiving engine exhaust from an engine and using heat from the engine exhaust for heating the first stream of feed fuel in a heater prior to said separating of the alcohol from the liquid residue.67. The process of item 66, wherein the step of receiving engine exhaust from an engine and using heat from the engine exhaust for said heating of the first stream of feed fuel comprises:- receiving engine exhaust from the engine into an oil heater;- exchanging heat from the engine exhaust into oil circulating in the oil heater to raise a temperature of the oil circulating in the heater, and- pumping the oil from the oil heater to said heater where the first stream of the feed fuel is heated; - exchanging heat from the oil into the feed fuel in the heater.68. The process of any one of items 60 to 67, wherein a reactor output of the reactor comprises ether, water, and unreacted alcohol, and the process further comprises:- condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output,- directing the separated unreacted alcohol and water to the first stream of the feed fuel prior to the separation of the alcohol from the liquid residue;- producing the secondary fuel from the ether-concentrated portion of the reactor output, and- storing the secondary fuel in the ether storage tank, the ether storage tank constituting a secondary fuel storage tank.69. The process of item 68, further comprising:- heating the first stream of feed fuel in a heater prior to separating the alcohol from the liquid residue, and directing the separated alcohol and water to enter into the first stream of feed fuel upstream of the heater.70. The process of item 68 or item 69, wherein the step of condensing the reactor output comprises at least two stages of condensation, including a first partial condensation step and a second partial condensation step, and wherein:- in the first partial condensation step a first partial condensation liquid product comprising alcohol and water a first percentage of ether is condensed and separated from an ether-concentrated vapour, and - in the second partial condensation step performed on the ether-concentrated vapour phase, a second partial condensation liquid product comprising methanol, water and second percentage of ether is condensed and separated from a second concentrated ether vapour, wherein the second percentage of ether is higher than the first percentage of ether.71. The process of item 70, wherein the second partial condensation liquid product is combined with the reactor output prior to said first partial condensation step and the first partial condensation step is performed on the combination of the reactor output and the second partial condensation liquid product.72. The process of any one of items 60 to 71, further comprising:- receiving data indicative of an unacceptable temperature in the reactor; and- performing one or more of the following steps, based on the data, to bring the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing the temperature of feed material fed into the reactor, said feed material comprising the alcohol evaporated from the first stream of feed fuel and separated from the residue;- changing the residence time of the feed material fed into the reactor; and- increasing the water content of the feed material fed into the reactor.73. The process of any one of items 60 to 72, wherein the reactor comprises a series of at least two reactors, including a first reactor and a second reactor, and catalytic conversion of alcohol to an ether takes place progressively through each reactor in series.74. The process of item 73, wherein a residence time of fluid fed through each reactor in the series of reactors increases from one reactor to the following reactor in the series.75. The process of item 73 or item 74, wherein an intercooler is positioned between two sequential reactors in the series, and the process comprises intercooling between the sequential reactors.76. The process of any one of items 60 to 75, wherein the feed fuel comprises said alcohol, between 0 and 30% by weight water, and at least 50ppm (on a weight basis) of a lubricity improver.77. The process of item 76, wherein the feed fuel comprises at least 10ppm corrosion inhibitor and / or a feed fuel colour additive, and wherein the liquid residue separated from the first stream of the feed fuel comprises corrosion inhibitor and / or feed fuel colour additive in addition to said lubricity improver.78. The process of any one of items 76 to 77, wherein:the feed fuel comprises from 0.5% to 30% by weight water, or an amount of water (by weight) within one of the following ranges: 0.8-30%; 1-30%, 2-30%; 3-30%, 4-30%, 5-30%, 0.5-20%, 0.8-20%; 1-20%, 2-20%; 3-20%, 4-20%, 5-20%, 0.5-15%, 0.8-15%; 1-15%, 2-15%; 3-15%, 4-15% or 5-15%;and wherein the residue separated from the first stream of the feed fuel comprises water in addition to said lubricity improver.79. The process of any one of items 76 to 78, wherein the alcohol in the feed fuel comprises methanol.80. The process of any one of items 76 to 79, wherein the alcohol in the feed fuel comprises ethanol.81. The process of any one of items 76 to 80, wherein the ether is dimethyl ether or diethyl ether.82. The process of any one of items 76 to 81, wherein the feed fuel comprises one or more high-boiling point materials with a boiling point higher than 100°C, other than the lubricity improver, and the high-boiling point materials are separated into the residue with the lubricity improver to be separated from the alcohol in the separation step.83. The process of item 82, wherein the feed fuel comprises one or more impurities selected from the group consisting of acetone, an alcohol other than methanol and ethanol, sulphur, inorganic matter.84. A process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel using a catalyst, the process comprising:- storing the feed fuel in a feed fuel tank, the feed fuel comprising alcohol;- directing a first stream of the feed fuel to a heater for heating of the first stream of the feed fuel and evaporating alcohol from the first stream of feed fuel;- producing the main fuel from a second stream of the feed fuel;- directing the evaporated alcohol to a reactor comprising the catalyst and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water;- producing secondary fuel from the ether produced in the reactor;- receiving data indicative of an unacceptable temperature in the reactor; and- performing one or more of the following steps, based on the data, to return the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing temperature of feed material fed into the reactor, said feed material comprising the alcohol evaporated from the first stream of feed fuel;- changing the residence time of the feed material fed into the reactor; and- increasing the water content of the feed material fed into the reactor.85. The process of item 84, wherein further comprising separating a liquid residue from the evaporated alcohol in a separator, and the step of producing main fuel from a second stream of the feed fuel comprises combining the liquid residue with the second stream of the feed fuel.86. The process of item 84 or 85, wherein the reactor comprises a series of at least two reactors, including a first reactor and a second reactor, and catalytic conversion of alcohol to an ether takes place progressively through each reactor in series, and wherein said one or more steps performed to return the temperature in the reactor within an acceptable range, based on the data, are:- varying the flow rate of alcohol through each of the reactors;- changing the temperature of feed material fed into the first reactor in the series;- changing the residence time of the feed material fed through each reactor; and- increasing the water content of the feed material fed into the first reactor.87. The process of item 86, wherein a residence time of fluid fed through each reactor in the series of reactors increases from one reactor to the following reactor in the series.88. The process of item 86 or item 87, wherein an intercooler is positioned between two sequential reactors in the series, and the process comprises intercooling between the sequential reactors.89. The process of any one of items 86 to 88, further comprising:- directing the main fuel to an engine for direct injection into a cylinder of the engine;- either combining the secondary fuel with air and directing the combination into the air intake of an engine, or directly injecting secondary fuel into a cylinder of an engine; and- receiving engine exhaust from an engine and using heat from the engine exhaust for heating the first stream of feed fuel in a heater prior to said separating of the alcohol from the residue.90. The process of any one of items 86 to 89, further comprising raising the temperature of the alcohol separated from the residue in the alcohol separation step in a superheater, prior to delivery of the separated alcohol to the reactor, and wherein the step of changing the temperature of feed fuel comprising the separated alcohol fed into the reactor comprises changing output temperature of the output of the superheater.91. The process of any one of items 86 to 90, comprising:- condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output;- producing the secondary fuel from the ether-concentrated portion of the reactor output; and- directing the separated unreacted alcohol and water to the first stream of the feed fuel for combination with the first stream of the feed fuel prior to delivery of the first stream of the feed fuel to the heater. 92. The process of item 91, wherein the step of condensing the reactor output comprises at least two stages of condensation, including a first partial condensation step and a second partial condensation step, and wherein:- in the first partial condensation step a first partial condensation liquid product comprising alcohol and water a first percentage of ether is separated from an ether-concentrated vapour, and the first partial condensation liquid product constitutes said separated unreacted alcohol and water that is directed to the first stream of the feed fuel prior to said feed fuel heating step,- in the second partial condensation step performed on the ether-concentrated vapour phase, a second partial condensation liquid product comprising methanol, water and second percentage of ether is separated from a second concentrated ether vapour, wherein the second percentage of ether is higher than the first percentage of ether; and- the second partial condensation liquid product is combined with the reactor output prior to said first partial condensation step.93. The process of any one of items 86 to 92, further comprising:- storing the secondary fuel comprising ether in a secondary fuel storage tank;- flushing the reactor with ether vapour from the secondary fuel storage tank to flush water byproduct from the reactor to protect catalyst in the reactor from the impact of extended water contact.94. The process of any one of items 86 to 93, wherein the feed fuel comprises said alcohol, between 0 and 30% by weight water, and at least 50ppm (on a weight basis) of a lubricity improver.95. The process of item 94, wherein the feed fuel comprises at least 10ppm corrosion inhibitor and / or a feed fuel colour additive, and wherein the liquid residue separated from the first stream of the feed fuel comprises corrosion inhibitor and / or feed fuel colour additive in addition to said lubricity improver.96. The process of any one of items 86 to 95, wherein:the feed fuel comprises from 0.5% to 30% by weight water, or an amount of water (by weight) within one of the following ranges: 0.8-30%; 1-30%, 2-30%; 3-30%, 4-30%, 5-30%, 0.5-20%, 0.8-20%; 1-20%, 2-20%; 3-20%, 4-20%, 5-20%, 0.5-15%, 0.8-15%; 1-15%, 2-15%; 3-15%, 4-15% or 5-15%;and wherein the residue separated from the first stream of the feed fuel comprises water in addition to said lubricity improver.97. The process of any one of items 94 to 96, wherein the alcohol in the feed fuel comprises methanol.98. The process of any one of items 94 to 97, wherein the alcohol in the feed fuel comprises ethanol.99. The process of any one of items 94 to 98, wherein the ether is dimethyl ether or diethyl ether.100. The process of any one of items 94 to 99, wherein the feed fuel comprises one or more high-boiling point materials with a boiling point higher than 100°C, other than the lubricity improver, and the high-boiling point materials are separated into the residue with the lubricity improver to be separated from the alcohol in the separation step.101. The process of item 100, wherein the feed fuel comprises one or more impurities selected from the group consisting of acetone, an alcohol other than methanol and ethanol, sulphur, inorganic matter.102. Use of a feed fuel comprising alcohol, between 0 and 30% by weight water and at least 50 ppm (on a weight basis) of a lubricity improver, to produce two fuel compositions including a main fuel comprising alcohol and lubricity improver, and a secondary fuel comprising ether, wherein the two fuel compositions are produced from the feed fuel by:- heating a first stream of the feed fuel and evaporating alcohol in the first stream of feed fuel,- separating a residue from the evaporated alcohol, the residue comprising lubricity improver;- directing the alcohol separated from the residue to a reactor and catalytically converting the alcohol to an ether and water in the reactor, wherein the reactor output comprises unreacted alcohol in addition to said ether and water;- producing the secondary fuel from the ether produced in the reactor; and- combining the residue separated from the evaporated alcohol with a second stream of the feed fuel to produce the main fuel.103. The use of item 102, wherein the feed fuel comprises at least 100ppm lubricity improver, or an amount of lubricity improver (by weight) within one of the following ranges: 100ppm – 10,000ppm, 100ppm – 7,500ppm, 100ppm – 5,000ppm, 100ppm – 2,500ppm, 100ppm – 2,000ppm, 100ppm – 1,500ppm, 150ppm – 2,000ppm, 150ppm – 1,500ppm, 200ppm – 2,000ppm, 200ppm – 1,500ppm, 100ppm – 1,200ppm, 150ppm – 1,200ppm, 200ppm – 1,200ppm.104. The use of item 102 or item 103, wherein the feed fuel comprises at least 10ppm corrosion inhibitor, and wherein the residue separated from the first stream of the feed fuel comprises corrosion inhibitor in addition to said lubricity improver.105. The use of any one of items 102 to 104, wherein the feed fuel comprises a feed fuel colour additive, and wherein the residue separated from the first stream of the feed fuel comprises feed fuel colour additive in addition to said lubricity improver.106. The use of any one of items 102 to 105, wherein:the feed fuel comprises from 0.2% to 30% by weight water, or an amount of water (by weight) within one of the following ranges: 0.5-30%; 0.8-30%; 1-30%, 2-30%; 3-30%, 4-30%, 5-30%, 0.2-20%, 0.5-20%, 0.8-20%; 1-20%, 2-20%; 3-20%, 4-20%, 5-20%, 0.2-15%, 0.5-15%, 0.8-15%; 1-15%, 2-15%; 3-15%, 4-15% or 5-15%;and wherein the residue separated from the first stream of the feed fuel comprises water in addition to said lubricity improver.107. The use of any one of items 102 to 106, wherein:the feed fuel has an alcohol content (measured as a total alcohol content) of at least 59.85%, at least 60%, at least 74.85%, at least 75%, at least 79.85%, at least 80%, at least 84.85%, at least 85%, at least 89.85%, at least 90% or at least 94.85% by weight of the feed fuel composition; and / orthe alcohol content of the water-free component of the feed fuel is at least 90%, 94.85%, 95%, 96%, 97%, 98% or 99% by weight; and / orthe alcohol content of the water-free component of the feed fuel is not more than 99.5%, 99.85%, 99.8%, 99.75%, 99.5%, 99%, 98%, 97.5%, 95% or 90% by weight.108. The use of any one of items 102 to 107, wherein the alcohol in the feed fuel comprises methanol.109. The use of item 108, wherein:the feed fuel has a methanol content of at least 59.85%, at least 60%, at least 74.85%, at least 75%, at least 79.85%, at least 80%, at least 84.85%, at least 85%, at least 89.85%, at least 90% or at least 94.85% by weight of the feed fuel composition; and / orthe methanol content of the water-free component of the feed fuel is at least 90%, 94.85%, 95%, 96%, 97%, 98% or 99% by weight; and / orthe methanol content of the water-free component of the feed fuel is not more than 99.5%, 99.85%, 99.8%, 99.75%, 99.5%, 99%, 98%, 97.5%, 95% or 90% by weight.110. The use of any one of items 102 to 109, wherein the ether is dimethyl ether or diethyl ether.111. The use of any one of items 102 to 107, wherein the alcohol in the feed fuel comprises ethanol.112. The use of item 111, wherein:the feed fuel has a methanol content of at least 59.85%, at least 60%, at least 74.85%, at least 75%, at least 79.85%, at least 80%, at least 84.85%, at least 85%, at least 89.85%, at least 90% or at least 94.85% by weight of the feed fuel composition; and / orthe ethanol content of the water-free component of the feed fuel is at least 90%, 94.85%, 95%, 96%, 97%, 98% or 99% by weight; and / orthe ethanol content of the water-free component of the feed fuel is not more than 99.5%, 99.85%, 99.8%, 99.75%, 99.5%, 99%, 98%, 97.5%, 95% or 90% by weight.113. The use of any one of items 102 to 112, wherein the feed fuel comprises one or more high-boiling point materials with a boiling point higher than 100°C, other than the lubricity improver, and the high-boiling point materials are separated into the residue with the lubricity improver to be separated from the alcohol in the separation step, and optionally wherein the high-boiling point materials are selected from a corrosion inhibitor and a feed fuel colour additive.114. The use of item 113, wherein the feed fuel comprises one or more impurities selected from the group consisting of acetone, an alcohol other than methanol and ethanol, sulphur and inorganic matter.115. The use of any one of items 102 to 114, further comprising:- receiving engine exhaust from an engine and using heat from the engine exhaust for said heating of the first stream of feed fuel.116. The use of item 115, wherein the main fuel is directed to an engine for fueling the engine, and the secondary fuel is combined with air and directed into the air intake of an engine or is directly injected into a cylinder of an engine.117. The use of item 115 or item 116, wherein the step of receiving engine exhaust from an engine and using heat from the engine exhaust for said heating of the first stream of feed fuel comprises:- receiving engine exhaust from the engine into an oil heater;- exchanging heat from the engine exhaust into oil circulating in the oil heater to raise a temperature of the oil circulating in the heater,- pumping the oil from the oil heater to said heater where the first stream of the feed fuel is heated; and - exchanging heat from the oil into the feed fuel in the heater.118. The use of any one of items 102 to 117, further comprising superheating the alcohol separated from the residue in the alcohol separation step, and feeding the superheated alcohol into the reactor. 119. The use of any one of items 102 to 118, further comprising:- condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output, and- using the ether-concentrated portion to produce the secondary fuel.120. The use of item 119, further comprising:- directing the separated unreacted alcohol and water to the first stream of the feed fuel prior to said heating of the first stream of the feed fuel.121. The use of item 119 or item 120, wherein the step of condensing the reactor output comprises at least two stages of condensation, including a first partial condensation step and a second partial condensation step, and wherein:- in the first partial condensation step a first partial condensation liquid product comprising alcohol and water a first percentage of ether is separated from an ether-concentrated vapour, and- in the second partial condensation step performed on the ether-concentrated vapour, a second partial condensation liquid product comprising methanol, water and a second percentage of ether is separated from a second concentrated ether vapour, wherein the second percentage of ether is higher than the first percentage of ether.122. The use of item 121, wherein the second partial condensation liquid product is combined with the reactor output prior to said first partial condensation step and the first partial condensation step is performed on the combination of the reactor output and the second partial condensation liquid product.123. The use of item 122, wherein the first partial condensation liquid product constitutes said separated unreacted alcohol and water that is directed to the first stream of the feed fuel prior to said feed fuel heating step.124. Use of a feed fuel comprising alcohol, between 0 and 30% by weight water and at least 50ppm (on a weight basis) of a lubricity improver, to produce two fuel compositions including a main fuel comprising alcohol and lubricity improver and a secondary fuel comprising ether, wherein the two fuel compositions are produced from the feed fuel by:- heating a first stream of the feed fuel and evaporating alcohol in the first stream of feed fuel;- separating a residue from the evaporated alcohol, the residue comprising lubricity improver;- directing the alcohol separated from the residue to a reactor, and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water;- condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output;- combining the residue separated from the evaporated alcohol with a second stream of the feed fuel to produce the main fuel; and- producing secondary fuel from the ether-concentrated portion of the reactor output.125. The use of item 124, further comprising:- directing the separated unreacted alcohol and water to the first stream of the feed fuel prior to said heating of the first stream of the feed fuel.126. The use of item 124 or item 125, wherein the feed fuel has the composition as defined in any one of items 88 to 99.127. A system for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel comprising alcohol, the system comprising:- a feed fuel tank;- a first feed fuel pump fluidically connected to the feed fuel tank configured to pump a first stream of the feed fuel from the feed fuel tank to a heater;- a second feed fuel pump fluidically connected to the feed fuel tank configured to pump a second stream of the feed fuel through a conduit along which main fuel can produced from the feed fuel;- the heater configured to receive the first stream of the feed fuel from the feed fuel tank, and configured to heat the feed fuel to enable evaporation of alcohol in the feed fuel;- optionally an alcohol separator configured to receive the feed fuel heated in the heater, the alcohol separator configured to separate evaporated alcohol from a liquid residue;- a reactor configured to receive the evaporated alcohol and to catalytically convert the evaporated alcohol to an ether and water, the reactor output comprising unreacted alcohol in addition to said ether and water;- a condenser configured to receive the reactor output and at least partially condense the reactor output; - a water separator configured to receive the at least partially condensed reactor output, the separator configured to separate a liquid product comprising at least a portion of the unreacted alcohol and water from the reactor output, and an ether-concentrated portion of the reactor output;- a secondary fuel tank in fluid communication with the water separator, for storing secondary fuel comprising ether from the ether-concentrated portion of the reactor output; and- a liquid product pump configured to pump the liquid product comprising at least a portion of the unreacted alcohol and water from the water separator for combining with at least one of:(i) the first stream of the feed fuel, upstream of the heater, or upstream of, or at, the alcohol separator;(ii) the reactor output upstream of the condenser; and(iii) the second stream of the feed fuel, for producing the main fuel from the combination of the feed fuel and the liquid product.128. The system of item 127, wherein the system comprises the alcohol separator, and the system further comprises:- a residue pump configured to pump a liquid residue separated from the evaporated alcohol in the alcohol separator for combination with the second stream of the feed fuel, enabling the main fuel to be produced from a combination of the feed fuel and the liquid residue.129. The system of item 127 or 128, further comprising:- a second partial condenser that receives the ether-concentrated portion from the water separator and is configured to partially condense the ether concentrated portion;- an ether separator that receives the partially condensed output of the second partial condenser, the ether separator configured to separate a second partial condensation liquid product comprising alcohol, water and ether from a concentrated ether vapour.130. The system of item 129, further comprising:- an ether recycle pump that receives the second partial condensation liquid product, the ether recycle pump configured to pump the second partial condensation liquid product for combination with the reactor output prior to delivery of the reactor output to the first partial condenser.131. The system of any one of items 127 to 130, wherein the heater is configured to heat the feed fuel using engine waste heat.132. The system of item 131, wherein the system comprises:- an oil heater in contact with the engine exhaust, the oil heater configured to enable engine exhaust heat to transfer into oil circuiting in the oil heater to raise the temperature of the oil circulating in the heater; and- a pump for pumping oil from the oil heater to said heater where the first stream of the feed fuel is heated; the heater being configured to enable heat to be exchanged from the oil into the feed fuel in the heater.133. The system of item 132, wherein the heater is configured to enable heat to be exchanged from the oil circulating in the oil heater into the feed fuel to raise the temperature of the feed fuel to a temperature above the boiling point of the alcohol in the feed fuel.134. The system of any one of items 127 to 133, further comprising:- a secondary fuel conduit for delivering secondary fuel into the air intake of the engine.135. The system of any one of items 127 to 134, further comprising:- a main fuel conduit for delivering main fuel to fuel injectors for direct injection into cylinders of the engine.136. The system of any one of items 127 to 135, further comprising:- an ether flushing conduit in fluid communication with the secondary fuel tank, the ether flushing conduit configured to allow ether to be conveyed from the secondary fuel tank, through the reactor, to flush a reactor space within the reactor with ether.137. The system of item 136, further comprising:- a superheater downstream of the heater and upstream of the reactor, configured to superheat the alcohol separated from the liquid residue prior to delivery of the separated alcohol to the reactor.138. The system of item 137, wherein the ether flushing conduit is configured to direct the ether the reactor via the superheater.139. The system of any one of items 127 to 138, wherein the reactor comprises a series of at least two reactors, including a first reactor and a second reactor, the reactors configured to enable catalytic conversion of alcohol to ether take place progressively through each reactor in series.140. The system of item 139, wherein the dimensions and configuration of the reactors in the series is such that a residence time of fluid fed through each reactor in the series of reactors increases from one reactor to the following reactor in the series.141. The system of item 139 or item 140, wherein an intercooler is positioned between two sequential reactors in the series, and the intercooler is configured to provide intercooling between the sequential reactors.142. The system of any one of items 127 to 141, further comprising:- a reactor temperature control unit structured to:- receive data indicative of an unacceptable temperature in the reactor; and- perform one or more of the following steps, based on the data, to return the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing temperature of feed material fed into the reactor, said feed material comprising the alcohol evaporated from the first stream of feed fuel and separated from the residue;- changing the residence time of the feed material fed into the reactor; and- increasing the water content of the feed material fed into the reactor.143. A system for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel, the system comprising:- a feed fuel tank for storing a feed fuel comprising an alcohol, between 0 and 30% by weight water, and at least 50ppm (on a weight basis) of a lubricity improver;- a first feed fuel pump fluidically connected to the feed fuel tank configured to pump a first stream of the feed fuel from the feed fuel tank to a heater;- a second feed fuel pump fluidically connected to the feed fuel tank configured to pump a second stream of the feed fuel from the feed fuel tank towards an engine;- the heater that receives the first stream of the feed fuel from the feed fuel tank, the heater configured to heat the feed fuel to enable evaporation of alcohol in the feed fuel;- an alcohol separator that receives the feed fuel heated in the heater, the separator configured to separate evaporated alcohol in the first stream of feed fuel from a liquid residue comprising lubricity improver;- a reactor that receives the evaporated alcohol separated by the alcohol separator, the reactor configured to catalytically convert the alcohol to an ether, from which the secondary fuel is produced; - a secondary fuel tank in fluid communication with the reactor, for storing secondary fuel comprising ether produced in the reactor, wherein the secondary fuel tank is in fluid communication with an engine for the delivery of the secondary fuel to the engine;- a residue pump configured to pump the liquid residue separated from the evaporated alcohol in the separator for combination with the second stream of the feed fuel, enabling the production of the main fuel from a combination of the feed fuel and the residue.144. The system of item 143, wherein the heater is configured to heat the feed fuel using engine waste heat.145. The system of item 144, wherein the system comprises:- an oil heater in contact with the engine exhaust, the oil heater configured to enable engine exhaust heat to transfer into oil circuiting in the oil heater to raise the temperature of the oil circulating in the heater; and- a pump for pumping oil from the oil heater to said heater where the first stream of the feed fuel is heated; the heater being configured to enable heat to be exchanged from the oil into the feed fuel in the heater.146. The system of item 145, wherein the heater is configured to enable heat to be exchanged from the oil circulating in the oil heater into the feed fuel to raise the temperature of the feed fuel to a temperature above the boiling point of the alcohol in the feed fuel.147. The system of any one of items 143 to 146, further comprising:- a secondary fuel conduit for delivering secondary fuel into the air intake of the engine.148. The system of any one of items 143 to 147, further comprising:- a main fuel conduit for delivering main fuel to fuel injectors for direct injection into cylinders of the engine.149. The system of any one of items 143 to 148, further comprising:- a first partial condenser that receives a reactor output from the reactor and is configured to partially condense the reactor output and produce a partially condensed reactor output;- a water separator that receives the partially condensed reactor output, the water separator configured to separate a liquid product comprising at least a portion of the unreacted alcohol and water from the reactor output, and an ether-concentrated portion of the reactor output;- a liquid product pump that receives the liquid product comprising at least a portion of the unreacted alcohol and water from the water separator, the liquid product pump configured to pump the liquid product for combination with the first stream of the feed fuel prior to delivery of the first stream of the feed fuel with the liquid product to the heater.150. The system of item 149, further comprising:- a second partial condenser that receives the ether-concentrated portion from the first separator and is configured to partially condense the ether concentrated portion;- an ether separator that receives the partially condensed output of the second partial condenser, the ether separator configured to separate a second partial condensation liquid product comprising methanol, water and ether from a concentrated ether vapour.151. The system of item 150, further comprising:- an ether recycle pump that receives the second partial condensation liquid product, the ether recycle pump configured to pump the second partial condensation liquid product for combination with the reactor output prior to delivery of the reactor output to the first partial condenser.152. The system of any one of items 143 to 151, further comprising:- an ether flushing conduit in fluid communication with the secondary fuel tank, the ether flushing conduit configured to allow ether to be conveyed from the secondary fuel tank, through the reactor, to flush a reactor space within the reactor with ether.153. The system of item 152, further comprising:- a superheater downstream of the heater and upstream of the reactor, configured to superheat the alcohol separated from the liquid residue prior to delivery of the separated alcohol to the reactor.154. The system of item 153, wherein the ether flushing conduit is configured to direct the ether the reactor via the superheater.155. The system of any one of items 143 to 154, wherein the reactor comprises a series of at least two reactors, including a first reactor and a second reactor, the reactors configured to enable catalytic conversion of alcohol to ether take place progressively through each reactor in series.156. The system of item 155, wherein the dimensions and configuration of the reactors in the series is such that a residence time of fluid fed through each reactor in the series of reactors increases from one reactor to the following reactor in the series.157. The system of item 155 or item 156, wherein an intercooler is positioned between two sequential reactors in the series, and the intercooler is configured to provide intercooling between the sequential reactors.158. The system of any one of items 143 to 157, further comprising:- a reactor temperature control unit structured to:- receive data indicative of an unacceptable temperature in the reactor; and- perform one or more of the following steps, based on the data, to return the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing temperature of feed material fed into the reactor, said feed material comprising the alcohol evaporated from the first stream of feed fuel and separated from the residue;- changing the residence time of the feed material fed into the reactor; and- increasing the water content of the feed material fed into the reactor.159. A system for protecting a catalyst used to produce a secondary fuel composition from a feed fuel, the system comprising:- a feed fuel tank;- a first feed fuel pump fluidically connected to the feed fuel tank configured to pump a first stream of the feed fuel from the feed fuel tank to a heater;- the heater that receives the first stream of the feed fuel from the feed fuel tank, the heater configured to heat the feed fuel to enable evaporation of alcohol in the feed fuel;- an optional alcohol separator that receives the feed fuel heated in the heater, the alcohol separator configured to separate evaporated alcohol from a liquid residue;- a reactor that receives the evaporated alcohol, the reactor comprising a reactor space where the alcohol comes into contact with the catalyst, the reactor configured to catalytically convert the alcohol to an ether and a water byproduct,- a secondary fuel tank in fluid communication with the reactor, for storing secondary fuel comprising ether produced in the reactor; and- an ether flushing conduit in fluid communication with the secondary fuel tank, the ether flushing conduit configured to allow ether to be conveyed from the secondary fuel tank, through the reactor, to flush the reactor space with ether.160. The system of item 159, comprising said alcohol separator, and further comprising- conduits for combining a liquid residue separated from the alcohol in the alcohol separator with a second stream of feed fuel from the feed fuel tank to produce a main fuel from a combination of the feed fuel and the liquid residue.161. The system of item 159 or item 160, wherein the secondary fuel tank is in fluid communication with an engine for the delivery of the secondary fuel to the engine, and the system comprises a main fuel pump configured to pump the main fuel to the engine.162. The system of item 159 or item 161, wherein the ether flushing conduit is configured to allow ether vapour in the ether storage tank to be conveyed to the reactor to flush the reactor space with ether vapour.163. The system of item 162, wherein the system further comprises an alcohol superheater for superheating evaporated alcohol prior to delivery of the alcohol into the reactor, and the ether flushing conduit delivers ether vapour to a conduit upstream of the alcohol superheater.164. The system of any one of items 159 to 163, wherein the heater is configured to heat the feed fuel using engine waste heat.165. The system of item 164, wherein the system comprises:- an oil heater in contact with the engine exhaust, the oil heater configured to enable engine exhaust heat to transfer into oil circuiting in the oil heater to raise the temperature of the oil circulating in the heater; and- a pump for pumping oil from the oil heater to said heater where the first stream of the feed fuel is heated; the heater being configured to enable heat to be exchanged from the oil into the feed fuel in the heater.166. The system of item 165, wherein the heater is configured to enable heat to be exchanged from the oil circulating in the oil heater into the feed fuel to raise the temperature of the feed fuel to a temperature above the boiling point of the alcohol in the feed fuel.167. The system of any one of items 159 to 166, further comprising:- a first partial condenser that receives a reactor output from the reactor and is configured to partially condense the reactor output;- a water separator that receives the partially condensed reactor output, the water separator configured to separate a liquid product comprising at least a portion of the unreacted alcohol and water from the reactor output, and an ether-concentrated portion of the reactor output;- a liquid product pump that receives the liquid product comprising at least a portion of the unreacted alcohol and water from the water separator, the liquid product pump configured to pump the liquid product for combination with the first stream of the feed fuel prior to delivery of the first stream of the feed fuel with the liquid product to the heater.168. The system of item 167, further comprising:- a second partial condenser that receives the ether-concentrated portion from the water separator and is configured to partially condense the ether concentrated portion;- an ether separator that receives the partially condensed output of the second partial condenser, the ether separator configured to separate a second partial condensation liquid product comprising methanol, water and ether from a concentrated ether vapour.169. The system of item 168, further comprising:- an ether recycle pump that receives the second partial condensation liquid product, the ether recycle pump configured to pump the second partial condensation liquid product for combination with the reactor output prior to delivery of the reactor output to the first partial condenser.170. The system of any one of items 159 to 169, wherein the reactor comprises a series of at least two reactors, including a first reactor and a second reactor, the reactors configured to enable catalytic conversion of alcohol to ether take place progressively through each reactor in series.171. The system of item 170, wherein the dimensions and configuration of the reactors in the series is such that a residence time of fluid fed through each reactor in the series of reactors increases from one reactor to the following reactor in the series.172. The system of item 170 or item 171, wherein an intercooler is positioned between two sequential reactors in the series, and the intercooler is configured to provide intercooling between the sequential reactors.173. The system of any one of items 159 to 172, further comprising:- a reactor temperature control unit structured to:- receive data indicative of an unacceptable temperature in the reactor; and- perform one or more of the following steps, based on the data, to return the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing temperature of feed material fed into the reactor, said feed material comprising the alcohol evaporated from the first stream of feed fuel and separated from the residue;- changing the residence time of the feed material fed into the reactor; and- increasing the water content of the feed material fed into the reactor.174. A system for controlling the temperature in a reactor used to produce a secondary fuel from a feed fuel, the system comprising:- a feed fuel tank;- a first feed fuel pump fluidically connected to the feed fuel tank configured to pump a first stream of the feed fuel from the feed fuel tank to a heater;- the heater that receives the first stream of the feed fuel from the feed fuel tank, the heater configured to heat the feed fuel to enable evaporation of alcohol in the feed fuel;- an optional alcohol separator that receives the feed fuel heated in the heater, the alcohol separator configured to separate evaporated alcohol from a liquid residue;- a reactor that receives the evaporated alcohol, the reactor comprising a reactor space where the alcohol comes into contact with a catalyst, the reactor configured to catalytically convert the alcohol to an ether and a water byproduct,- a secondary fuel tank in fluid communication with the reactor, for storing secondary fuel comprising ether produced in the reactor; and- a reactor temperature control unit structured to:- receive data indicative of an unacceptable temperature in the reactor; and- perform one or more of the following steps, based on the data, to return the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing temperature of feed material fed into the reactor, said feed material comprising the evaporated alcohol;- changing the residence time of the feed material fed into the reactor; and- increasing the water content of the feed material fed into the reactor.175. The system of item 174, further comprising:- an ether flushing conduit in fluid communication with the secondary fuel tank, the ether flushing conduit configured to allow ether to be conveyed from the secondary fuel tank, through the reactor, to flush the reactor space with ether.176. A process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel comprising alcohol, the process comprising:- storing the feed fuel in a feed fuel tank;- directing a first stream of the feed fuel from the feed fuel tank to a separator and separating alcohol from a liquid residue;- combining the residue with a second stream of the feed fuel to produce the main fuel;- directing the separated alcohol to a reactor and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water; - condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output; and- producing secondary fuel from the ether-concentrated portion of the reactor output.177. A system for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel comprising alcohol, the system comprising:- a feed fuel tank;- a first feed fuel pump fluidically connected to the feed fuel tank configured to pump a first stream of the feed fuel from the feed fuel tank to a heater;- a second feed fuel pump fluidically connected to the feed fuel tank configured to pump a second stream of the feed fuel from the feed fuel tank towards an engine;- the heater that receives the first stream of the feed fuel from the feed fuel tank, the heater configured to heat the feed fuel to enable evaporation of alcohol in the feed fuel;- an alcohol separator that receives the feed fuel heated in the heater, the alcohol separator configured to separate alcohol from a liquid residue;- a reactor that receives the evaporated alcohol separated by the alcohol separator, the reactor configured to catalytically convert the alcohol to an ether and water, the reactor output comprising unreacted alcohol in addition to said ether and water;- a partial condenser that receives the reactor output and is configured to partially condense the reactor output;- a water separator that receives the partially condensed reactor output, the separator configured to separate a liquid product comprising at least a portion of the unreacted alcohol and water from the reactor output, and an ether-concentrated portion of the reactor output;- a liquid product pump that receives the liquid product comprising at least a portion of the unreacted alcohol and water from the water separator, the liquid product pump configured to pump the liquid product for combination with the first stream of the feed fuel prior to delivery of the first stream of the feed fuel with the liquid product to the heater;- a secondary fuel tank in fluid communication with the water separator, for storing secondary fuel comprising ether from the ether-concentrated portion of the reactor output, wherein the secondary fuel tank is in fluid communication with an engine for the delivery of the secondary fuel to the engine;- a residue pump that receives the residue separated from the evaporated alcohol in the alcohol separator, the residue pump configured to pump the residue for combination with the second stream of the feed fuel, thereby producing the main fuel from a combination of the feed fuel and the residue; and- a main fuel pump configured to pump main fuel to the engine.

Claims

1. CLAIMS:

1. A process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel comprising alcohol, the process comprising:- storing the feed fuel in a feed fuel tank;- directing a first stream of the feed fuel from the feed fuel tank to a heater and heating the first stream of feed fuel to evaporate alcohol in the feed fuel;- optionally separating a liquid residue from the evaporated alcohol;- producing main fuel from a second stream of the feed fuel;- directing the evaporated alcohol to a reactor and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water; - condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output;- producing the secondary fuel from the ether-concentrated portion of the reactor output;and- combining the separated unreacted alcohol and water with one or more of:(i) the first stream of the feed fuel upstream of said heating step, or upstream of, or at, said liquid residue separation, or(ii) the reactor output upstream, of the condensation of the reactor output, or(iii) the second stream of the feed fuel for incorporation as a component of the main fuel.

2. The process of claim 1, comprising conducting the step of separating the liquid residue from the evaporated alcohol, and combining the separated unreacted alcohol and water with the first stream of the feed fuel upstream of, or at, the separation of the liquid residue from the evaporated alcohol.

3. The process of claim 1 or claim 2 wherein the ether content of the reactor output is less than 55 wt% ether.

4. The process of any one of claims 1 to 3, wherein the ether content of the secondary fuel produced following the condensation and separation steps performed on the reactor output is between 60wt% and 97 wt%, or between 60 wt% and 89 wt%, or between 60wt% and 74 wt%, or between 75wt% and 97 wt%, or between 75 wt% and 89wt%, or between 90 and 97 wt%.

5. The process of any one of claims 1 to 4, wherein the ether content of the secondary fuel is at least 20%, or at least 40% or at least 60% or at least 70% higher than the ether content of the reactor output.

6. The process of any one of claims 1 to 5, wherein the process is a closed-loop process.

7. The process of any one of claims 1 to 6, wherein the step of condensing the reactor output comprises at least two stages of condensation, including a first partial condensation step and a second partial condensation step, and wherein:- in the first partial condensation step a first partial condensation liquid product comprising alcohol and water is condensed and separated from an ether-concentrated vapour, and- in the second partial condensation step, a second partial condensation liquid product comprising methanol, water and ether is condensed and separated from a second concentrated ether vapour.

8. The process of any one of claims 1 to 7, comprising:- conducting the step of separating the liquid residue from the evaporated alcohol; and- combining the liquid residue with the second stream of the feed fuel to produce the main fuel.

9. The process of any one of claims 1 to 8, wherein the feed fuel comprises said alcohol, between 0 and 30% by weight water, and at least 100ppm (on a weight basis) of a lubricity improver.

10. The process of claim 9, wherein the feed fuel comprises at least 10ppm corrosion inhibitor and / or a feed fuel colour additive, and wherein the liquid residue separated from the evaporated alcohol comprises corrosion inhibitor and / or feed fuel colour additive in addition to said lubricity improver.

11. The process of claim 9 or claim 10, wherein:the feed fuel comprises from 0.5% to 30% by weight water;and wherein the liquid residue separated from the evaporated alcohol comprises water in addition to said lubricity improver.

12. The process of any one of claims 1 to 11, wherein the alcohol in the feed fuel comprises methanol and / or ethanol, and the ether is dimethyl ether and / or diethyl ether.

13. The process of claim 12, wherein the feed fuel comprises one or more impurities selected from the group consisting of acetone, an alcohol other than methanol and ethanol, sulphur, inorganic matter.

14. The process of any one of claims 1 to 13, further comprising:- directing the main fuel to an engine for direct injection into a cylinder of the engine; and- either combining the secondary fuel with air and directing the combination into the air intake of an engine, or directly injecting secondary fuel into a cylinder of an engine.

15. The process of claim 14, further comprising:- receiving engine exhaust from an engine and using heat from the engine exhaust for heating the first stream of feed fuel in the heater.

16. The process of any one of claims 1 to 15, further comprising:- storing the secondary fuel comprising ether in a secondary fuel storage tank;- flushing the reactor with ether vapour from the secondary fuel storage tank to flush water byproduct from the reactor to protect catalyst in the reactor from the impact of extended water contact.

17. The process of any one of claims 1 to 16, further comprising:- receiving data indicative of an unacceptable temperature in the reactor; and- performing one or more of the following steps, based on the data, to bring the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing the temperature of feed material fed into the reactor, said feed material comprising the alcohol evaporated in the first stream of feed fuel;- changing the residence time of the feed material fed into the reactor; and - increasing the water content of the feed material fed into the reactor.

18. A process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel, the process comprising:- storing a feed fuel in a feed fuel tank, the feed fuel comprising an alcohol, between 0 and 30% by weight water, and at least 50 ppm (on a weight basis) of a lubricity improver;- directing a first stream of the feed fuel to a heater for heating of the first stream of the feed fuel, evaporating alcohol from the first stream of feed fuel and separating a residue therefrom, the residue comprising lubricity improver;- directing the alcohol separated from the residue to a reactor, catalytically converting the alcohol to an ether, and producing the secondary fuel from the ether;- combining the residue separated from the evaporated alcohol with a second stream of the feed fuel to produce the main fuel;- directing the main fuel to an engine for fueling the engine; and- directing the secondary fuel to an engine separately to the main fuel.

19. A process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel using a catalyst, the process comprising:- storing a feed fuel comprising alcohol in a feed fuel tank;- vaporising alcohol in a first stream of the feed fuel taken from the feed fuel tank;- directing the vaporised alcohol to a reactor comprising the catalyst and catalytically converting the alcohol to an ether and a water byproduct;- storing the ether in an ether storage tank;- flushing the reactor with ether from the ether storage tank to flush water byproduct from the reactor; - producing main fuel from a second stream of the feed fuel, and- producing secondary fuel from the ether produced in the reactor.

20. A process for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel using a catalyst, the process comprising:- storing the feed fuel in a feed fuel tank, the feed fuel comprising alcohol;- directing a first stream of the feed fuel to a heater for heating of the first stream of the feed fuel and evaporating alcohol in the first stream of feed fuel;- producing the main fuel from a second stream of the feed fuel;- directing the evaporated alcohol to a reactor comprising the catalyst and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water;- producing secondary fuel from the ether produced in the reactor;- receiving data indicative of an unacceptable temperature in the reactor; and- performing one or more of the following steps, based on the data, to return the temperature in the reactor within an acceptable range:- varying the flow rate of alcohol through the reactor;- changing temperature of feed material fed into the reactor, said feed material comprising the alcohol evaporated in the first stream of feed fuel;- changing the residence time of the feed material fed into the reactor; and- increasing the water content of the feed material fed into the reactor.

21. Use of a feed fuel comprising alcohol, between 0 and 30% by weight water and at least 50ppm (on a weight basis) of a lubricity improver, to produce two fuel compositions including a main fuel comprising alcohol and lubricity improver and a secondary fuel comprising ether, wherein the two fuel compositions are produced from the feed fuel by:- heating a first stream of the feed fuel and evaporating alcohol in the first stream of feed fuel;- separating a residue from the evaporated alcohol, the residue comprising lubricity improver;- directing the alcohol separated from the residue to a reactor, and catalytically converting the alcohol to an ether and water, wherein the reactor output comprises unreacted alcohol in addition to said ether and water;- condensing the reactor output and separating at least a portion of the unreacted alcohol and water from an ether-concentrated portion of the reactor output;- combining the residue separated from the evaporated alcohol with a second stream of the feed fuel to produce the main fuel; and- producing secondary fuel from the ether-concentrated portion of the reactor output.

22. A system for producing two fuel compositions, including a main fuel and a secondary fuel, from a feed fuel comprising alcohol, the system comprising:- a feed fuel tank;- a first feed fuel pump fluidically connected to the feed fuel tank configured to pump a first stream of the feed fuel;- a second feed fuel pump fluidically connected to the feed fuel tank configured to pump a second stream of the feed fuel through a conduit along which main fuel can be produced from the feed fuel;- the heater configured to receive the first stream of the feed fuel from the feed fuel tank, and configured to heat the feed fuel to enable evaporation of alcohol in the feed fuel;- optionally an alcohol separator configured to receive the feed fuel heated in the heater, the alcohol separator configured to separate evaporated alcohol from a liquid residue;- a reactor configured to receive the evaporated alcohol and to catalytically convert the evaporated alcohol to an ether and water, the reactor output comprising unreacted alcohol in addition to said ether and water;- a condenser configured to receive the reactor output and at least partially condense the reactor output;- a water separator configured to receive the at least partially condensed reactor output, the separator configured to separate a liquid product comprising at least a portion of the unreacted alcohol and water from the reactor output, and an ether-concentrated portion of the reactor output;- a secondary fuel tank in fluid communication with the water separator, for storing secondary fuel comprising ether from the ether-concentrated portion of the reactor output; and- a liquid product pump configured to pump the liquid product comprising at least a portion of the unreacted alcohol and water from the water separator for combining with at least one of:(i) the first stream of the feed fuel upstream of the heater or upstream of, or at, the alcohol separator;(ii) the reactor output upstream of the condenser; and(iii) the second stream of the feed fuel, for producing the main fuel from the combination of the feed fuel and the liquid product.

23. The system of claim 22, wherein the system comprises the alcohol separator, and further comprises: - a residue pump configured to pump a liquid residue separated from the evaporated alcohol in the alcohol separator for combination with the second stream of the feed fuel, enabling the main fuel to be produced from a combination of the feed fuel and the liquid residue.

24. The system of any one of claims 22 to 23, further comprising:- a second partial condenser that receives the ether-concentrated portion from the water separator and is configured to partially condense the ether-concentrated portion;- an ether separator that receives the partially condensed output of the second partial condenser, the ether separator configured to separate a second partial condensation liquid product comprising alcohol, water and ether from a concentrated ether vapour.

25. The system of any one of claims 22 to 24, further comprising:- a secondary fuel conduit for delivering secondary fuel into the air intake of the engine, and- a main fuel conduit for delivering main fuel to fuel injectors for direct injection into cylinders of the engine.

26. The system of any one of claims 22 to 25, wherein the heater is configured to heat the feed fuel using engine waste heat.

27. The system of any one of claims 22 to 26, further comprising:- an ether flushing conduit in fluid communication with the secondary fuel tank, the ether flushing conduit configured to allow ether to be conveyed from the secondary fuel tank, through the reactor, to flush a reactor space within the reactor with ether.

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