Methanol production plant and method of producing methanol

Abstract

Disclosed is a methanol production plant comprising a synthesis system that comprises one or more synthesis reactors configured for catalytically converting a syngas to methanol, the synthesis system being configured to synthesize methanol in a synthesis loop, an extraction system configured for extracting a purge stream from the synthesis loop, a combustion system configured for combusting at least part of the purge stream, the combustion system comprising one or more pilot lights, and a fluid conduit system configured for supplying the purge stream to the combustion system, wherein the combustion system is further configured to supply part of the purge stream to at least one of the one or more pilot lights, and wherein the at least one of the one or more pilot lights is configured for using the supplied part of the purge stream as fuel. Also disclosed is a method of producing methanol from a syngas and a pilot light for a combustion system.

Description

[0001] METHANOL PRODUCTION PLANT AND METHOD OF PRODUCING METHANOL

[0002] Technical field

[0003] The present disclosure relates to a methanol production plant and method of producing methanol from a syngas, in particular a method of reducing greenhouse gas emissions while producing methanol from a syngas. Also, the disclosure relates to a pilot light for a combustion system and a combustion system, such as a flare or a thermal oxidizer, comprising a pilot light.

[0004] Background

[0005] Methanol has a number of uses, for example as a base chemical, and is a promising energy carrier / storage system. The alcohol may be produced from a variety of carbonbased feedstocks and is often referred to with a colour designating the type of feedstock that was used: "brown methanol" was produced using coal, "grey methanol" was produced using natural gas, "blue methanol" was produced using captured CO2, which would otherwise be released into the environment, and "green methanol" is produced using biomass or using captured carbon dioxide and green hydrogen, i.e. hydrogen produced using electricity from renewable energy sources; In the latter case, the green methanol is referred to as "e-methanol".

[0006] The production of green methanol is the more carbon neutral of the above described ways to produce methanol. With the attraction of being environmentally friendlier, green methanol, and in particular e-methanol, are desirable products.

[0007] A methanol production plant synthesizes methanol, CH3OH, by converting carbon oxides to methanol by thermal catalytic hydrogenation. For example, by converting CO and / or CO2 via any of the reactions:

[0008] CO + 2H2-> CH30H CO2+ 3H2-> CH30H + H2O The components for the reaction are provided as syngas, a gas mixture comprising either carbon monoxide or carbon dioxide or both carbon oxides as well as hydrogen. The methanol synthesis can be done in a so-called synthesis loop, wherein unreacted carbon oxide(s) and hydrogen is recirculated and partly re-used. In the synthesis loop so- called "inert" components will build up, such as nitrogen, argon, methane etc., components which are not inert as such, but which are considered inert in the sense that they are unable to react within the synthesis loop. To avoid this build-up of inert components, a purge stream is extracted from the synthesis loop in any of well-known manners. For example, a purge gas line may be attached to the recycling stream. In some cases, an extracted purge stream may simply be vented, i.e. discharged as off-gas from a production plant. However, in the case of a methanol synthesis loop, the purge stream comprises the greenhouse gas CO2, and in order to reduce venting of greenhouse gas, the gas in the purge stream is usually burned off, also referred to as the gas being flared or combusted. However, burning off of the purge stream may mean that the only use made of the purge stream is to generate heat, which may then be distributed. Alternatively, or additionally, the purge stream may be treated in order to separate components, such as hydrogen, in order to use the separated components elsewhere. Additional uses of purge stream extracted from a methanol synthesis loop is desirable.

[0009] On this background, despite previous efforts, it remains desirable to provide an improved method of producing methanol, for example a method of reducing greenhouse gas emissions while producing methanol from a syngas, and a methanol production plant that solve one or more of the above problems and / or other problems, and / or that have other benefits, or that at least provide an alternative to existing solutions.

[0010] It is thus desirable to provide an improved methanol production plant.

[0011] It is further desirable to provide an improved methanol production plant, which is environmentally friendlier. It is further desirable to provide an improved methanol production plant and method of producing methanol, which utilises the extracted purge stream, or part of the extracted purge stream.

[0012] It is further desirable to provide an improved method of producing methanol, in particular an improved method of reducing greenhouse gas emissions while producing methanol from a syngas.

[0013] In particular, it is desirable to provide an improved method of producing green methanol or e-methanol.

[0014] The present disclosure relates to different aspects each yielding one or more of the benefits and advantages described in connection with one or more of the other aspects, and each having one or more embodiments corresponding to the embodiments described in connection with one or more of the other aspects and / or disclosed in the appended claims.

[0015] According to an aspect, disclosed herein are embodiments of a methanol production plant, the plant comprising:

[0016] - a synthesis system comprising one or more synthesis reactors configured for catalytically converting a syngas to methanol, the synthesis system being configured to synthesize methanol in a synthesis loop,

[0017] - an extraction system configured for extracting a purge stream from the synthesis loop,

[0018] - a combustion system configured for combusting at least part of the purge stream, the combustion system comprising one or more pilot lights, and

[0019] - a fluid conduit system configured for supplying the purge stream to the combustion system, wherein the combustion system is configured to supply a part of the purge stream to at least one of the one or more pilot lights, and wherein the at least one of the one or more pilot lights is configured for using the supplied part of the purge stream as fuel. In a methanol production plant that produces green methanol, the hydrogen and carbon oxide(s) in the syngas have been obtained using biomass or using captured carbon dioxide and green hydrogen. In some embodiments, the methanol production plant is configured to produce green methanol. If green methanol is produced using captured carbon dioxide and green hydrogen, i.e. hydrogen produced by using electricity that was obtained using renewable energy, the produced methanol may be referred to as e- methanol. For example, green hydrogen may be produced by electrolysis of water, where the electrolysis is powered by solar power, e.g. by power generated from solar panels. In some embodiments, the methanol production plant is configured to produce e-methanol.

[0020] The combustion system may comprise one or more combustion units of any type of suitable combustion unit, such as one or more flares and / or one or more thermal oxidisers. In some embodiments, the combustion system comprises one or more flares and / or one or more thermal oxidisers. The combustion unit is suitable for combusting purge stream, the gas in the purge stream being rich in hydrogen. The combustion system further comprises one or more pilot lights, which is an ignition source for the more powerful burner unit, such as for a thermal oxidizer or a flare. Preferably, the one or more pilot lights are dedicated pilot lights. A dedicated pilot light is a pilot light configured to use or 'handle' syngas whereby it then typically cannot handle 'normal fuel' like propane, NG (natural gas), etc. See also additionally in the following. Each pilot light is characterised by comprising a single nozzle. When the plant is in normal operation, i.e. when the synthesis loop is running and purge stream is being extracted from the synthesis loop, the combustion system is configured to supply part of the purge stream to at least one of the one or more pilot lights comprised in the combustion system, where the pilot light receiving part of the purge stream is configured to use the supplied part of the purge stream as fuel. A part of the purge stream may be all of the purge stream, i.e. the whole part. The combustion system may be configured to supply substantially 20% to 100% of the extracted purge stream to at least one of the one or more pilot lights, such as supply substantially 35% to 100% of the extracted purge stream, such as supply 45% to 100% of the extracted purge stream. The extraction system may be configured for extracting the purge stream continuously or intermittently. Thus, advantageously, when the methanol production plant is running normally, purge gas will be used as fuel for a pilot light, which will reduce the consumption of other types of fuel for a pilot light, such as propane. Since the purge stream would be combusted anyway, the purge gas is free fuel. If the purge stream originates from captured CO2 and green hydrogen, any CO2 emissions are neutral, while if the purge stream originates from biogenic CO2 and green hydrogen, the CO2 emissions from the methanol production plant are entirely, or almost entirely, biogenic. In contrast, if another fuel, for example propane, natural gas and / or LPG (Liquefied petroleum gas), is used as pilot light fuel the methanol production plant may emit fossil CO2.

[0021] A pilot light in a combustion system at a methanol production plant may be configured to burn substantially continuously to ensure that the combustion system is ready for emergency cases or when otherwise needed. In emergency cases, a combustion system in a methanol production plant is often further configured to combust gasses during process upset conditions, such as e.g. emergency shut downs, fire etc., which may require release of a large volume of gas. As the synthesis loop may not be running continuously, the methanol production plant may further comprise a pilot light fuel tank, such as a propane tank, natural gas tank and / or LPG (Liquefied petroleum gas) tank, from which secondary fuel for one or more pilot lights can be supplied, e.g. where the secondary fuel may be propane, natural gas and / or LPG. In some embodiments, the pilot light fuel tank is configured to store fuel for one or more of the one or more pilot lights, and thus, at least one pilot light may be configured for using secondary fuel from the pilot light fuel tank as fuel. This will allow for at least one pilot light to be burning substantially continuously, while the plant is operational. Thus, while fuel from the pilot light fuel tank has been stored in the tank prior to usage, the part of the purge stream supplied to a pilot light may be supplied directly after, i.e. shortly after, the purge stream being extracted. Alternatively, or additionally, the part of the purge stream supplied to a pilot light may have been stored prior to being supplied to a pilot light as fuel. Furthermore, the purge stream may be set by the system (or method) independently of any requirements of the fuel system / combustion system. The pilot light may typically require a certain heating value to supply stable flame. The purge gas composition and heating value may be determined by the upstream system and does not need to be adjusted to match a standard pilot light system. Instead, the pilot light is a dedicated pilot light dedicated and configured to handle a range of syngas composition so that the pilot light can be operated with expected compositions without having to adjust the upstream system to match pilot light requirements. This ensures optimized purge for the upstream process(es) instead of alternating the purge flow or adding hydrogen to match a certain purge gas composition required for pilot lights.

[0022] In some embodiments, the combustion system is configured to provide fuel from the pilot light fuel tank to at least one pilot light configured for using secondary fuel only when the supplied part of the purge stream is insufficient as fuel for at least one pilot light. Thus, the methanol production plant may be configured to use part of the extracted purge stream as fuel for at least one pilot light, while a purge stream is available in sufficient quantity and quality, and to use fuel from the pilot light fuel tank as fuel for at least one pilot light, when a purge stream is not available in sufficient quantity and quality. The combustion system may be configured to stop the supply of fuel from the pilot light fuel tank, when it is determined that the extracted purge stream is sufficient for fuelling one or more pilot lights. For example, the combustion system may be configured to stop the supply of fuel from the pilot light fuel tank, when it is determined that purge stream is available for fuelling one or more pilot lights.

[0023] Control of fuel flow to the one or more pilot lights may comprise mechanical control, such as e.g. via valves and piping, and / or computational control, such as e.g. by a circuit or processing system configured for making determinations, for example determinations on the quantity and / or quality of the purge stream. A processing system may comprise any circuit and / or device suitably adapted to perform functions as described herein. In particular, a processing system may comprise a general- or special-purpose programmable microprocessor unit, such as a central processing unit (CPU) of a computer or of another data processing system, a digital signal processing unit (DSP), an application specific integrated circuits (ASIC), a programmable logic arrays (PLA), a field programmable gate array (FPGA), a special purpose electronic circuit, etc., or a combination thereof. If the combustion system comprises a plurality of pilot lights, the two or more pilot lights may be part of different combustion units within the combustion system, or one or more combustion units within the combustion system may comprise more than one pilot light. A combustion unit may be e.g. a flare or a thermal oxidizer.

[0024] A single pilot light may be configured to use part of the purge stream as fuel or to be fuelled by secondary fuel from the pilot light fuel tank. Thus, in some embodiments, at least one of the one or more pilot lights is a multi-burn pilot light configured to be fuelled by either of supplied purge stream or secondary fuel from the pilot light fuel tank. The combustion system may be configured such that fuel from the pilot light fuel tank to the at least one multi-burn pilot light is supplied primarily, or only, when the supplied purge stream is insufficient. Thus, in some embodiments, the combustion system is configured to provide fuel from the pilot light fuel tank to the at least one multi-burn pilot light when the supplied purge stream is insufficient, such as only when the supplied purge stream is insufficient.

[0025] In some embodiments, the combustion system comprises two or more pilot lights and at least one pilot light, other than the pilot light configured for being fuelled by purge stream, is configured for using secondary fuel from the pilot light fuel tank as fuel, for example if the supplied purge stream is insufficient.

[0026] According to another aspect provided is a method for producing methanol from a syngas, the method comprising the steps:

[0027] - providing the syngas to a synthesis system configured to synthesize methanol from the syngas in a synthesis loop,

[0028] - extracting a purge stream from the synthesis loop,

[0029] - supplying the purge stream to a combustion system, the combustion system comprising one or more pilot lights,

[0030] - providing at least one of the one or more pilot lights with part of the purge stream as fuel. In some embodiments, the syngas comprises carbon oxide(s) obtained from biomass and / or captured carbon dioxide. In some embodiments, wherein the syngas further comprises green hydrogen.

[0031] In some embodiments, the method further comprises supplying secondary fuel from a pilot light fuel tank to at least one of the one or more pilot light, the at least one pilot light using the supplied secondary fuel as fuel.

[0032] In some embodiments, the method further comprises determining whether purge stream is sufficient, such as whether purge stream is available, for fuelling the at least one pilot light configured for being fuelled by purge stream.

[0033] In some embodiments, the step of supplying secondary fuel further comprises secondary fuel from the pilot light fuel tank being used as fuel for a pilot light when the supplied purge stream is insufficient as fuel for the pilot light.

[0034] In some embodiments, the combustion system comprises one or more flares and / or one or more thermal oxidisers.

[0035] In some embodiments, at least one of the one or more pilot lights is a multi-burn pilot light configured to be fuelled by either supplied purge stream or by secondary fuel from the pilot light fuel tank.

[0036] In some embodiments, the combustion system comprises two or more pilot lights and at least one pilot light is configured for using secondary fuel from the pilot light fuel tank as fuel if the supplied purge stream is insufficient, and at least one pilot light is configured for using part of the purge stream as fuel.

[0037] According to another aspect provided is a methanol production plant configured to perform steps of the method for producing methanol from a syngas disclosed herein. According to another aspect provided is a pilot light for a combustion system, the combustion system being configured for combustion of a purge stream extracted from a methanol synthesis loop, wherein the pilot light is configured for being fuelled by either purge stream or by a secondary fuel, such as propane, natural gas and / or LPG (Liquefied petroleum gas).

[0038] According to another aspect provided is a combustion system configured for combustion of a purge stream (e.g. or preferably as provided in or by the other aspects) extracted from a methanol synthesis loop, the combustion system comprising a pilot light wherein the pilot light is configured for being fuelled by either a part of the purge stream or by a secondary fuel, such as propane, natural gas and / or LPG (Liquefied petroleum gas).

[0039] In some embodiments, of the mentioned aspects, the purge stream is a hydrogen rich purge stream.

[0040] In the aspects disclosed herein, terms and features relate to the terms and features having the same name in the other aspects and therefore the descriptions and explanations of terms and features given in one aspect apply, with appropriate changes, to the other aspects. Additional aspects, embodiments, features and advantages will be made apparent from the following detailed description of embodiments and with reference to the accompanying drawings.

[0041] Brief iption of the

[0042] Preferred embodiments will be described in more detail in connection with the appended drawings, where:

[0043] FIGS. 1 and 2 show a schematic view of parts of a methanol production plant according to some embodiments, and

[0044] FIGS. 3 and 4 show a schematic flow diagram of a method for producing methanol from a syngas according to some embodiments.

[0045] Detailed description FIGS. 1 and 2 show a schematic view of parts of a methanol production plant according to some embodiments. The methanol production plant is generally referenced by the reference numeral 1 and comprises a synthesis system 21, a methanol storage 23, a combustion system 25, and a pilot light fuel tank 29.

[0046] Arrows are used in figs. 1 and 2 to denote a fluid flow. The fluid may be directed using a fluid conduit system comprising piping, valves, and other known components of a conduit system for fluids.

[0047] The synthesis system comprises one or more synthesis reactors (not shown) configured to catalytically convert syngas to methanol, possibly to methanol and water. The synthesis system is configured to synthesize methanol in a synthesis loop, wherein unreacted carbon oxide(s) and hydrogen is recirculated and partly re-used.

[0048] Syngas 3 is provided to the synthesis system 21. Traditionally, syngas was produced by gasification of coal, a process that may result in a number of air pollutants such as carbon dioxide, sulphur dioxide and nitrogen oxides. A more environmentally friendly way of producing a syngas is to use captured CO2 mixed with hydrogen, such as green hydrogen.

[0049] If the carbon oxide in the syngas is primarily CO2, for example captured CO2, the conversion produces a mixture of methanol and water. A distillation system (not shown) may be used to separate methanol from the mixture. After a purification process, such as a distillation and / or other purification processes of the methanol, the purified / distilled methanol 5 is sent to a methanol storage 23 configured for storing the methanol. The methanol may later be distributed from the storage, for example to be used as fuel or as a base chemical in the manufacturing of another product.

[0050] When producing methanol from syngas in a synthesis loop, "inert" components may accumulate as un-reacted syngas is recycled in the loop. To alleviate this accumulation an extraction system is configured to extract a purge stream 7 from the synthesis loop, that is to purge an amount of gas from the gas being recycled in the synthesis loop. In conventional methanol manufacturing plants the purge stream is combusted in an integrated fired heater or furnace. However, in methanol manufacturing plants that do not have an integrated fired heater or furnace, such as e-methanol manufacturing plants, this option is not available.

[0051] A fluid conduit system supplies the purge stream 7 to the combustion system 25. The combustion system may comprise one or more combustion units (not shown), such as one or more flares and / or one or more thermal oxidizers. The combustion units are ones that are suitable for combusting the gasses comprised in the purge stream 7 and possibly other gasses as well. Each combustion unit comprises one or more pilot lights 27, which are ignition sources for the more powerful combustion units. Preferably, the one or more pilot lights are dedicated pilot lights dedicated and configured to handle a range of syngas composition so that the pilot light can be operated with expected compositions without having to adjust the upstream system to match pilot light requirements.

[0052] A pilot light may generally be operated on demand or intermittently or continuously, or in a combination of these. A combustion unit in a methanol manufacturing plant may be part of plant safety measures and the pilot light of the combustion unit may be operated continuously to ensure that the combustion unit is ready at any time.

[0053] The combustion system supplies part of the purge stream 9 to the pilot light 27, which is configured to use the supplied part of the purge stream as fuel, while any remainder of the purge stream is sent for combustion in a combustion unit. That is, the purge stream that is delivered to the combustion system is separated and provided in part to the pilot light and in part to a combustion chamber of a combustion unit, for example the combustion unit which the pilot light is part of. The part of the purge stream that is delivered to a pilot light is used as pilot light fuel.

[0054] The pilot light 27 may be further configured to be fuelled by a secondary fuel obtained from the pilot light fuel tank 29. The secondary fuel may be propane or other suitable fuel, e.g. natural gas and / or LPG (Liquefied petroleum gas). Thus, the pilot light 27 may be a multi-burn pilot light, which can be fuelled by two or more sources. This allows the pilot light 27 to operate with a continuous burn as it is not dependent on purge gas being sufficient, such as being available and of high enough quality. The pilot light may be connected to the pilot light fuel tank 29 via piping, such as gas piping, allowing the secondary fuel 11 to be delivered to the pilot light.

[0055] The combustion system 25 may comprise one or more sensing units used in the control of fuel to the pilot light 27. For example, the combustion system may comprise a first sensing system 13 coupled to the fluid conduit system upstream from the pilot light 27 and downstream from where a part of the purge stream is separated from the remainder. The first sensing system may comprise e.g. a volumetric flow meter configured to monitor the flow of purge gas to the pilot light. Further, the first sensing system 13 may comprise one or more sensing units suitable for measuring one or more characteristics of the extracted purge stream, such as the composition, the presence of one or more constituents, the temperature, the pressure, etc. The measurements done by the first sensing system 13 may be used for one or more determinations, such as a determination of the sufficiency of the part of the purge stream as fuel.

[0056] Further, the combustion system may comprise a second sensing system 15 coupled to the fluid conduit system upstream from the pilot light 27 and downstream from the pilot light fuel tank 29. The second sensing system may comprise e.g. a volumetric flow meter configured to monitor the flow of secondary fuel from the pilot light fuel tank towards the pilot light. Further, the second sensing system 15 may comprise one or more sensing units suitable for determining characteristics of the secondary fuel, either while the secondary fuel is still in the tank 29 or as it flows towards the pilot light, such as the composition, the presence of one or more constituents, the temperature, the pressure, etc. The measurements done by the second sensing system 15 may be used for one or more determinations, such as a determination of the flow of secondary fuel to the pilot light 27. Further, the combustion system may comprise a third sensing system 15 coupled to the fluid conduit system upstream from the separation point, where a part of the purge stream is separated from the remainder so as to be used as fuel, and downstream from the extraction point, where the purge gas is extracted from the synthesis loop. The third sensing system may comprise e.g. a volumetric flow meter configured to monitor the flow of purge stream. Further, the third sensing system 15 may comprise one or more sensing units suitable for determining characteristics of the purge stream, such as the composition, the presence of one or more constituents, the temperature, the pressure, etc. The measurements done by the third sensing system 15 may be used for one or more determinations, such as a determination of the sufficiency of the extracted purge stream as fuel.

[0057] The combustion system 25 may further comprise a control system (not shown) configured to control the flow of fuel to the pilot light 27. The control system may comprise mechanical control, such as valves and piping, and / or computational control, such as one or more circuits or processing systems. The control system may be configured to make determinations, such as on the quantity and / or quality of the purge stream. The control system may be coupled to the first and / or second and / or third sensor system 13, 15, 17 and be configured to obtain information on the purge stream and / or on fuel from or in the pilot light fuel tank. For example, the control system may be configured to control the flow of purge stream, for example to the pilot light, and / or the flow of fuel from the fuel tank to the pilot light and may do so based on one or more determinations, such as one or more determinations based on the information obtained from the first and / or second sensor system. If the control system determines that the purge stream being supplied to the combustion system is insufficient, i.e. insufficient for the fuelling of the pilot light, it may close the line supplying the purge stream and open the line supplying fuel from the pilot light fuel tank to the pilot light. Alternatively, the control system may in that instance open the line supplying secondary fuel from the pilot light fuel tank to the pilot light, while leaving the flow line supplying purge stream open, and monitor the line supplying the purge stream. The lines supplying fuel for the pilot light may be part of a fluid conduit system. If the pilot light is configured for burning two or more fuel sources simultaneously, the control system may regulate the flow from each fuel source, such as the flow of the purge stream and of the secondary fuel to the pilot light. For example, the pilot light may be configured to burn either purge stream or secondary fuel or a combination thereof. Thus, the control system may be configured to regulate the flow from each fuel source so as to provide fuel from a single fuel source or so as to optimise the composition of the combined fuel being provided to the pilot light. Thus, the pilot light 27 may be configured to operate with purge gas or secondary fuel, such as propane, natural gas, LPG, etc., or with a combination of the two fuel sources.

[0058] Optimally, very little or no fossil fuel is required to operate the pilot light 27 such that it runs almost entirely, or entirely, on purge stream. When the pilot light is fuelled only by purge stream, no further fossil-fuel-generated CO2 is introduced to the atmosphere, but only carbon neutral CO2; Thus, the amount of fossil-fuel-generated CO2 released by the methanol manufacturing plant is reduced or eliminated.

[0059] FIG. 2 shows an embodiment of the combustion system 25 of the methanol manufacturing plant 1, which may be an alternative to the embodiment shown in fig. 1 or used together with the embodiment shown in fig. 1. Common elements in figs. 1 and 2 are numbered the same.

[0060] In the embodiment shown in fig. 2, the combustion system 25 comprises a first pilot light 27' and a second pilot light 27". The first pilot light 27' is configured to receive purge gas that has been purged from the synthesis loop and may be adapted for being fuelled solely with purge gas (or other gas with similar composition). The second pilot light 27" is configured to being fuelled by secondary fuel from the pilot light fuel tank 29. The secondary fuel may be a fossil fuel such as propane, natural gas and / or LPG (Liquefied petroleum gas). The second pilot light 27" may be designed solely for use with a fossil fuel received from the pilot light fuel tank 29 and may be a conventional pilot light. The first and second pilot lights may be part of the same combustion unit, e.g. be positioned in the same flare or thermal oxidizer. The first and second pilot light may be operated simultaneously or one at a time.

[0061] If sufficient purge gas is provided to the first pilot light 27' to charge the combustion unit it is part of, the second pilot light 27" may not be operated. Alternatively, if no purge gas, or insufficient purge gas, is available to charge the first pilot light, the second pilot light may be operated and may provide all of the energy to charge the combustion unit it is part of.

[0062] Thus, in some embodiments, the first pilot light and the second pilot light are part of the same combustion unit and the combustion unit is configured to operate the two pilot lights simultaneously to provide the required amount of energy for the combustion unit. Alternatively, the first and second pilot lights are part of different combustion units.

[0063] FIG. 3 shows a schematic flow diagram of a method for producing methanol from a syngas according to some embodiments.

[0064] In step S31, syngas is provided to a synthesis system which is configured to synthesize methanol from the syngas in a synthesis loop. Thus, the synthesis system is configured to synthesize methanol in a synthesis loop, wherein unreacted carbon oxide(s) and hydrogen is recirculated and partly re-used.

[0065] The syngas may comprise carbon oxide(s) obtained from biomass and / or captured carbon dioxide, and further comprise green hydrogen. The synthesis system may be a synthesis system as described herein.

[0066] In step S32, a purge stream is extracted from the synthesis loop. Purging from the synthesis loop alleviates the accumulation of "inert" components that may otherwise result from un-reacted syngas being recycled in the loop. In step S34, the purge stream is supplied to a combustion system, which comprises one or more pilot lights. A fluid conduit system may supply the purge stream to the combustion system. The combustion system may comprise one or more combustion units, such as one or more flares and / or one or more thermal oxidizers. The combustion units are suitable for combusting the gasses comprised in the purge stream and possibly other gasses as well. Each combustion unit comprises one or more pilot lights, which are ignition sources for the more powerful combustion units. The combustion system may be a combustion system as described herein.

[0067] In step S35, at least one of the one or more pilot lights is provided with part of the purge stream as fuel. A part of the purge stream may be all of the purge stream, i.e. the whole part. Thus, a part of the purge stream is used as fuel for the pilot light, while any remaining purge stream supplied to the combustion system is burned off.

[0068] FIG. 4 shows a schematic flow diagram of a method for producing methanol from a syngas according to some embodiments.

[0069] Steps S41, S42, S44 and S45 may be as described, respectively, in steps S31, S32, S34, and S35 in connection with fig. 3.

[0070] In step S43, a determination is made whether the extracted purge stream is sufficient, such as whether purge stream is available, for fuelling a pilot light configured for being fuelled by purge stream.

[0071] In step S45, secondary fuel from a pilot light fuel tank is supplied to at least one of the one or more pilot lights, the at least one pilot light using the supplied secondary fuel as fuel when the supplied purge stream is insufficient as fuel for the pilot light.

[0072] In some embodiments, the pilot light receiving purge stream and the pilot light receiving secondary fuel is the same pilot light, and this pilot light is a multi-burn pilot light configured to be fuelled by supplied purge stream or by secondary fuel from the pilot light fuel tank. The multi-burn pilot light may be a multi-burn pilot light as described herein. In some embodiments, the combustion system comprises two or more pilot lights and at least one pilot light is configured for using secondary fuel from the pilot light fuel tank as fuel if the supplied purge stream is insufficient, and at least one other pilot light is configured for using part of the purge stream as fuel.

[0073] It should be emphasized that the term "comprises / comprising" when used in this specification is taken to specify the presence of stated features, elements, steps or components but does not preclude the presence or addition of one or more other features, elements, steps, components or groups thereof.

[0074] List of references

[0075] I Methanol production plant (parts of)

[0076] 3 Syngas

[0077] 5 Methanol

[0078] 7 Purge stream

[0079] 9 Pilot light purge stream fuel

[0080] II Pilot light secondary fuel

[0081] 13 First sensing system

[0082] 15 Second sensing system

[0083] 17 Third sensing system

[0084] 21 Synthesis system

[0085] 23 Methanol storage

[0086] 25 Combustion system 1 Pilot light

[0087] 29 Pilot light fuel tank

Claims

Claims1. A methanol production plant comprising:- a synthesis system comprising one or more synthesis reactors configured for catalytically converting a syngas to methanol, the synthesis system being configured to synthesize methanol in a synthesis loop,- an extraction system configured for extracting a purge stream from the synthesis loop,- a combustion system configured for combusting at least part of the purge stream, the combustion system comprising one or more pilot lights, and- a fluid conduit system configured for supplying the purge stream to the combustion system, wherein the combustion system is further configured to supply part of the purge stream to at least one of the one or more pilot lights, and wherein the at least one of the one or more pilot lights is configured for using the supplied part of the purge stream as fuel.

2. The methanol production plant according to claim 1, wherein the methanol production plant further comprises a pilot light fuel tank, such as a propane tank, natural gas tank and / or LPG (Liquefied petroleum gas) tank, the pilot light fuel tank being configured to store fuel for one or more of the one or more pilot lights, and wherein at least one pilot light is configured for using secondary fuel from the pilot light fuel tank as fuel.

3. The methanol production plant according to claim 2, wherein the combustion system is configured to provide fuel from the pilot light fuel tank to the at least one pilot light configured for using secondary fuel when the supplied part of the purge stream is insufficient as fuel for the at least one pilot light.

4. The methanol production plant according to any of the previous claims, wherein at least one of the one or more pilot lights is a multi-burn pilot light configured to be fuelled by either supplied purge stream or by secondary fuel from the pilot light fuel tank.

5. The methanol production plant according to any of claims 1-3, wherein the combustion system comprises two or more pilot lights and at least one pilot light, other than the pilot light configured for being fuelled by purge stream, is configured for using secondary fuel from the pilot light fuel tank as fuel.

6. A method of producing methanol from a syngas comprising hydrogen and carbon oxides, the method comprising:- providing the syngas to a synthesis system configured to synthesize methanol from the syngas in a synthesis loop,- extracting a purge stream from the synthesis loop,- supplying the purge stream to a combustion system, the combustion system comprising one or more pilot lights,- providing at least one of the one or more pilot lights with part of the purge stream as fuel.

7. The method according to claim 6, wherein the method further comprises:- supplying secondary fuel from a pilot light fuel tank to at least one of the one or more pilot lights, the at least one pilot light using the supplied secondary fuel as fuel.

8. The method according to claim 7, wherein the method further comprises determining whether the extracted purge stream is sufficient, such as whether purge stream is available, for fuelling the at least one pilot light configured for being fuelled by purge stream, and wherein the step of supplying secondary fuel further comprises secondary fuel from the pilot light fuel tank being used as fuel for a pilot light when the supplied purge stream is insufficient as fuel for the pilot light.

9. The method according to any of claims 6-8, wherein at least one of the one or more pilot lights is a multi-burn pilot light configured to be fuelled by either supplied purge stream or by secondary fuel from the pilot light fuel tank.

10. The method according to any of claims 6-8, wherein the combustion system comprises two or more pilot lights and at least one pilot light is configured forusing secondary fuel from the pilot light fuel tank as fuel if the supplied purge stream is insufficient, and at least one pilot light is configured for using part of the purge stream as fuel.

11. A pilot light for a combustion system configured for combustion of a purge stream extracted from a methanol synthesis loop, wherein the pilot light is configured for being fuelled by either, or both of, purge stream and / or a secondary fuel, such as propane, natural gas and / or LPG (Liquefied petroleum gas).

12. The pilot light according to claim 11, wherein the purge stream is provided by the method according to any one of claims 6 - 10.

13. The methanol production plant according to any one of claim 1 - 5, the method according to any one of claims 6 - 10, and / or the pilot light according to claim 11 or 12, wherein the gas in the purge stream is rich in hydrogen whereby the purge stream is a hydrogen rich purge stream.

14. The methanol production plant according to any one of claim 1 - 5, the method according to any one of claims 6 - 10, and / or the pilot light according to claim 11 or 12, wherein the one or more pilot lights are dedicated pilot lights configured to handle a range of syngas composition whereby the pilot light can be operated with predetermined expected compositions.