Method and apparatus for converting an alcohol into a fuel mixture

Abstract

A method for converting an alcohol into a fuel mixture consisting of alcohol, ether and water, suitable for operating an internal combustion engine (5), in particular an internal combustion engine in a motor vehicle, wherein the alcohol is converted into the fuel mixture in a reactor (3) at a suitable reaction temperature, wherein the mixing ratio of alcohol content, ether content and water content in the fuel mixture is adjusted by controlling at least one reaction parameter of a reaction taking place in the reactor (3), characterized in that the control of at least one reaction parameter is dependent on operating parameters of the internal combustion engine (5), wherein the operating parameters include a boost pressure, a rotational speed and / or a load.

Description

[0001] The invention relates to a method for converting an alcohol into a fuel mixture according to the preamble of claim 1 and a device for carrying it out according to claim 10.

[0002] The substitution of conventional fossil fuels with alternative fuels is becoming increasingly important. In this context, alcohols such as methanol or ethanol are particularly interesting, as they can be produced relatively easily from renewable sources. However, these fuels cannot be used in compression-ignition diesel engines due to their low cetane number. To enable combustion in diesel engines, additives such as dimethyl ether or diethyl ether can be added to these fuels to increase their cetane number.

[0003] A mixture of alcohol, ether and water can also be produced directly during the operation of an internal combustion engine in an upstream process step from alcohol, for example from methanol or ethanol, with the help of a suitable catalyst.

[0004] From US patent 44 22 412 A, a process for converting alcohol into a fuel mixture is known, in which, by means of a catalyst in a reactor, the alcohol, for example methanol, heated to a suitable reaction temperature, is converted into a fuel mixture according to the attached reaction equation: 2CH3OH ↔ CH3-O-CH3 + H2O Reaction 1

[0005] The methanol (CH3OH) used here also produces dimethyl ether (CH3-O-CH3) and water (H2O) in the reactor. If, on the other hand, ethanol is used to produce the fuel mixture for the conversion process, a mixture of ethanol, diethyl ether, and water can be produced using the reactor. Gamma-aluminum can be used as a catalyst in the reactor.

[0006] The fuel mixture produced according to this known method is subject to very strong quality fluctuations, which manifests itself in a highly variable water content. Therefore, its use in diesel engines is not practical. These quality fluctuations lead to widely varying cetane numbers and, consequently, to widely varying ignition timing. Furthermore, the resulting fuel mixture is not always equally suitable for all engine operating points.

[0007] The invention is based on the objective of providing a method for converting an alcohol into a fuel mixture for an internal combustion engine, with which a consistent quality of the resulting fuel mixture can be achieved.

[0008] The solution to this problem is obtained by the features specified in claim 1. Particularly advantageous embodiments of the method according to the invention are disclosed in dependent claims 2 to 9.

[0009] According to the characterizing part of claim 1, the mixing ratio of alcohol, ether, and water in the fuel mixture is adjusted by controlling at least one reaction parameter. The mixing ratio of the fuel mixture resulting from the conversion of the alcohol depends, among other things, on the reaction temperature; therefore, the mixing ratio can be adjusted by appropriately setting the reaction temperature. The following table shows, by way of example, the dependence of the mixing ratio on the reaction temperature at a reactor pressure of 2 MPa when using methanol as the alcohol, which is converted in a reactor into a fuel mixture of alcohol, ether, and water: Reaction temperature [°C] Alcohol content [%] Ether content [%] Water content [%] 200 8 67 25 300 14 62 24 400 19 59 22 500 22 57 21

[0010] The desired reaction temperature can be set by appropriately controlling the temperature of the supplied alcohol, for example, the supplied methanol. Another reaction parameter with which the mixing ratio of the fuel mixture produced according to the invention can be adjusted is the reaction pressure.

[0011] Investigations have shown that the formation of dimethyl ether (DME) according to reaction 1 follows the following rate approach: with: Rate of change of mass of DME K M : Equilibrium constant of methanol p M : Methanol partial pressure k r : Rate constant of the reaction (Arrhenius approach) E A : Activation energy (approx. 60 kJ mol )

[0012] This makes it clear that the rate at which DME is formed depends on the methanol partial pressure as well as on the temperature dependence of the rate constant k. r , depends on the reaction temperature.

[0013] By adjusting the mixing ratio of alcohol, ether, and water in the fuel mixture, a desired cetane number can be achieved using relatively simple control systems. To operate an internal combustion engine in the homogeneous compression ignition range, a cetane number below 50 and / or an octane number above 95 RON can be achieved, while for diesel engine operation, a fuel mixture with a cetane number above 50 can be produced by appropriately controlling the reaction taking place in the reactor.

[0014] The control of at least one reaction parameter can also be achieved, in particular, depending on the operating parameters of the internal combustion engine for which the fuel mixture is intended. This allows the fuel mixture's properties to be adapted, for example, to operating parameters such as boost pressure, engine speed, and / or load, in order to achieve optimized engine operation.

[0015] Reaction parameters can also be controlled depending on the operating parameters of an exhaust aftertreatment system, for example to achieve the lowest possible emissions during combustion in the internal combustion engine.

[0016] The reaction parameters can also depend on the nature of the alcohol used, whereby the purity of the alcohol used can also be taken into account as a reaction parameter.

[0017] For the conversion of an alcohol into a fuel mixture, methanol or ethanol can be used, for example; however, a methanol-ethanol mixture can also be used as the alcohol to be converted in order to achieve desired fuel properties. The fuel mixture produced by the process according to the invention can therefore contain dimethyl ether and / or diethyl ether as the ether component.

[0018] The invention also aims to provide a device for converting an alcohol into a fuel mixture for an internal combustion engine, with which the fuel mixture can be varied with respect to its mixture proportions.

[0019] The solution to the problem relating to the device is achieved by the features of claim 10. Particularly advantageous embodiments of the device according to the invention are disclosed in dependent claims 11 to 15.

[0020] In the device according to claim 10, the alcohol supplied to the reactor is heated by means of a heating device. According to the characterizing part of claim 10, a control device is provided which adjusts the heating of the alcohol in the heating device depending on reaction parameters of a conversion process taking place in the reactor and / or operating parameters of an associated internal combustion engine. By heating the supplied alcohol accordingly, different reaction temperatures result, which can be varied, for example, in a range between 200 and 500°C. Depending on the set reaction temperature, a fuel mixture with a desired alcohol-ether-water mixture ratio is obtained as the reaction product. The mixture ratio significantly determines the combustion properties of the fuel mixture in the internal combustion engine.These combustion properties can be easily adjusted by controlling the reaction temperature.

[0021] The preferred embodiment of the device according to the invention has a heating unit consisting of an exhaust gas heat exchanger and an air heat exchanger. At least one of the two heat exchangers is controlled with respect to the heat transfer to the alcohol flowing through it, which is supplied to the reactor. The air heat exchanger preferably serves as a cooling device to cool the alcohol, heated in the upstream exhaust gas heat exchanger, to a desired process temperature. It may be sufficient to control only the cooling by the air heat exchanger to achieve a desired reaction temperature in the reactor.

[0022] Using sensors that measure the temperature and / or pressure in the reactor, a control unit, as part of a control system, can regulate the heating of the supplied alcohol. Such a temperature control system can be implemented with relatively simple means.

[0023] Furthermore, the pressure in the reactor can also be regulated or changed independently of the temperature, for example with the help of a pressure regulating valve and / or by varying the amount supplied and / or discharged.

[0024] The reaction process taking place in the reactor can also be controlled depending on the cylinder pressure and / or knock sensor signals. For this purpose, cylinder pressure sensors and / or knock sensors can be mounted on the internal combustion engine, transmitting their signals via measuring lines to the control unit for adjusting the heating of the alcohol and / or the pressure in the reactor.

[0025] The control unit, which regulates the heating of the alcohol supplied to the reactor, can also take into account other operating parameters of the internal combustion engine and its exhaust aftertreatment system in order to optimize fuel combustion. In particular, this can lead to a reduction in pollutants and improved fuel efficiency.

[0026] The invention is described below with reference to a figure shown in the drawing. 1 The illustrated embodiment is explained in more detail.

[0027] Fig. Figure 1 shows a schematic representation of a device for converting alcohol into a fuel mixture, which serves as fuel for the operation of an internal combustion engine.

[0028] The device has a tank 1 , in which, for example, methanol or ethanol is present as an alcohol, which is supplied by means of a first pump P1 via a heating device 2 a reactor3 is supplied to the reactor. 3 The alcohol is converted into a fuel mixture at a suitable reaction temperature, which is then transported via a chamber 4 and a second pump P2 of the internal combustion engine 5 is supplied. At the internal combustion engine 5 These include fuel injectors. 6 until 9 arranged, through which the fuel mixture enters the combustion chambers of the internal combustion engine 5 is injected.

[0029] The in Fig. The device shown in 1 can in particular be arranged in a motor vehicle whose internal combustion engine 5 a diesel engine.

[0030] So that the internal combustion engine 5 supplied fuel mixture for the internal combustion engine 5 Once a suitable mixing ratio of the proportions of alcohol, ether and water has been achieved, the alcohol is added before it enters the reactor. 3is supplied to a suitable temperature in the heating device. 2 heated. The heating process is controlled by a control unit. 10 depending on several operating parameters. The control unit 10 This is obtained from within the reactor 3 and on the internal combustion engine 5 intended sensors via measurement signal lines 11 until 13 Measurement signals representing different operating parameters. From the reactor 3 The control unit receives 10 The reaction temperature and reaction pressure are used as measurement signals upon which the mixing ratio of alcohol, ether, and water in the fuel mixture depends. The control unit also receives... 10 from a knock sensor 14 and a cylinder pressure sensor 15corresponding measurement signals, which together with other operating condition signals, such as speed, load and acceleration, determine the current operating condition of the internal combustion engine 5 to identify. Depending on these operating parameters of the internal combustion engine 5 can the control unit 10 determine a suitable mixing ratio for the fuel mixture and appropriately control the reaction in the reactor 3 undertake.

[0031] In the illustrated embodiment, the heating device consists of 2 from an exhaust gas heat exchanger 16 and an air heat exchanger 17 Through the exhaust gas heat exchanger 16 the exhaust pipe 18 the internal combustion engine 5 , which are in the exhaust gas heat exchanger 16 which also passes through the exhaust gas heat exchanger 16 The alcohol is heated by the circulating stream. The heated alcohol exits the exhaust gas heat exchanger. 16to the air heat exchanger 17 , where the alcohol can be cooled to a desired temperature by means of ambient air flowing through it. Both the exhaust gas heat exchanger 16 as well as the air heat exchanger 17 These can be controllable heat exchangers, which allow for the control of heat transfer. For example, in the exhaust gas heat exchanger 16 Through a bypass control system, only a more or less significant portion of the exhaust gas flow is used to heat the alcohol flowing through it. In the case of the air heat exchanger... 17 For example, the airflow through the air heat exchanger can be used to regulate the cooling of the alcohol flowing through it. 17 from the control unit 10 can be controlled.

[0032] Of course, the heat exchanger can be used 17 Instead of air, other heat transfer media such as water or oil (not shown here) can also be used.

[0033] In addition to temperature, the pressure in the reactor can also be varied using control devices. This can be achieved, firstly, by changing the amount of methanol delivered by pump P1, for example, by altering its speed or stroke, or by using a variable throttle on the suction side of pump P1. Alternatively, a pressure control valve can be used on the discharge side of pump P1, allowing the pressure in the reactor to be set independently of the reactor temperature.

[0034] The one in the reactor 3 The generated fuel mixture can be placed in a reactor 3 downstream chamber 4 Further treatment or temporary storage may be required. QUOTES INCLUDED IN THE DESCRIPTION

[0035] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0036] US 4422412 A

[0004]

Claims

[1] Method for converting an alcohol into a fuel mixture consisting of alcohol, ether and water, which can be used to operate an internal combustion engine ( 5 ), in particular an internal combustion engine in a motor vehicle, is suitable, wherein the alcohol is reacted at a suitable reaction temperature in a reactor ( 3 ) is converted into the fuel mixture, characterized by that the mixing ratio of alcohol content, ether content, and water content in the fuel mixture can be controlled by controlling at least one reaction parameter in the reactor ( 3 ) the ongoing reaction is stopped. [2] Method according to claim 1, characterized by that the mixing ratio is adjusted by controlling the reaction temperature and / or the reaction pressure in the reactor. [3] Method according to one of claims 1 or 2, characterized bythat the control of at least one reaction parameter depending on operating parameters of the internal combustion engine ( 5 ). [4] Method according to any one of the preceding claims, characterized by that the control of at least one reaction parameter depends on the operating parameters of an exhaust aftertreatment system. [5] Method according to any one of the preceding claims, characterized by that the control of at least one reaction parameter depends on the nature of the alcohol to be converted. [6] Method according to any one of the preceding claims, characterized by that a methanol-ethanol mixture is used as the alcohol to be converted in the process. [7] Method according to any one of the preceding claims, characterized by that the fuel mixture produced according to the process contains dimethyl ether and / or diethyl ether as the ether component. [8] Method according to any one of the preceding claims, characterized by that the internal combustion engine ( 5 ) is operated in the homogeneous compression ignition operating range. [9] Method according to any one of claims 1 to 7, characterized by that the conversion of the alcohol into a fuel mixture takes place in such a way that the cetane number of the fuel mixture is above 50. [10] Device with a reactor ( 3 ), which uses a heating device ( 2 ) heated alcohol into a fuel mixture for the operation of an internal combustion engine ( 5 ) converts, in particular to carry out the method according to claim 1, characterized by that a control device ( 10 ) the heating of the alcohol in the heating device ( 2 ) and / or the pressure in the reactor as a function of reaction parameters of a process in the reactor ( 3 ) ongoing reaction and / or depending on operating parameters of the internal combustion engine (5 ) sets up. [11] Device according to claim 10, characterized by that the heating device ( 2 ) from an exhaust gas heat exchanger ( 16 ) for heating and, if necessary, at least one second heat exchanger ( 17 ), with air or liquids as the transfer medium, for cooling, and that at least in one of the two heat exchangers ( 16 , 17 ) the heat transfer to the flowing alcohol by means of the control device ( 10 ) is controllable. [12] Device according to one of claims 10 or 11, characterized by that the second heat exchanger ( 17 ) between the exhaust gas heat exchanger ( 16 ) and the reactor ( 3 ) is arranged and uses ambient air or a liquid, in particular water or oil, to transfer heat to the exhaust gas heat exchanger ( 16 ) heated alcohol to a temperature suitable for the reactor ( 3) the ongoing reaction cools to a suitable temperature and / or pressure value. [13] Device according to any one of claims 10 to 12, characterized by that sensors measure the temperature and / or pressure in the reactor ( 3 ) measure and send the measured values ​​as measurement signals to the control unit ( 10 ) transmitted. [14] Device according to any one of claims 10 to 13, characterized by that one or more cylinder pressure sensors ( 15 ) and / or one or more knock sensors ( 14 ) on the internal combustion engine ( 5 ) are provided which send their measurement signals to the control unit ( 10 ) as operating parameters of the internal combustion engine ( 5 ) to adjust the heating of the alcohol being converted and / or the pressure in the reactor. [15] Device according to any one of claims 10 to 14, characterized by that the control unit ( 10 ) the speed and load of the internal combustion engine ( 5) as operating parameters when adjusting the heating of the alcohol to be converted and / or the pressure in the reactor.

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