WO2021191116A1

WO2021191116A1 - Co2-neutral liquid fuel

Info

Publication number: WO2021191116A1
Application number: PCT/EP2021/057201
Authority: WO
Inventors: Frank Obrist
Original assignee: Obrist Technologies Gmbh
Priority date: 2020-03-23
Filing date: 2021-03-22
Publication date: 2021-09-30
Also published as: DE102020107903A1

Abstract

The invention relates to a CO2-neutral liquid fuel for universal use, especially in internal combustion engines, preferably reciprocating piston engines, comprising the following components as a mixture: - between 15 vol% and 50 vol% of water, - between 3 vol% and 16 vol% of a cold-starting assistant having a boiling point at 1 atm of less than 64.7°C and - balance, especially between 34 vol% and 82 vol%, of methanol from renewable production. The invention also relates to the use of such a liquid fuel, to the production thereof, and to a method of operating a four-stroke reciprocating piston engine with such a liquid fuel.

Description

C0 ₂ -neutral liquid fuel

DESCRIPTION

The invention relates to a CC -neutral liquid fuel for universal use, in particular in internal combustion engines. The invention also relates to the use of a liquid fuel and a method for its lowering position. Another aspect of the invention relates to a method for operating a spark-ignited four-stroke floating piston engine with such a liquid fuel.

It has long been known that the high emissions of carbon dioxide (CO2) on earth contribute significantly to global warming and thus to changes in the overall climate on our only planet. For this reason, various measures are already being taken to reduce CC emissions.

Many measures are aimed at reducing local _{CO 2} emissions.

However, the aim should be to contribute to a global reduction in CC emissions, because the problem of global warming is not limited to local areas.

Internal combustion engines make a significant contribution to CC emissions. In particular, engines, be it in block-type thermal power stations or in mobile applications, especially vehicles, have a significant share in the high C0 _{2 emissions.} For this reason, various approaches are already being pursued in order to reduce CC emissions, especially in the field of motor vehicle mobility.

An essential aspect is the provision of new fuels for internal combustion engines, with a proportion of fuel produced from biomass being added to the fossil fuel. Gasoline fuels are known that contain up to 10% bioethanol.

Another additional fuel that is used is methanol. In racing, for example, methanol is used as an admixture to petrol, the methanol being used in particular to increase performance. So far, however, methanol has mainly been produced from natural gas, i.e. a fossil fuel. Methanol produced in this way has a negative climate balance because im fossil fuel-bound CO2 is released into the atmosphere and thus increases global warming.

_{Emissions of nitrogen oxides (NO x} ), which are also harmful to the climate, represent a major additional problem with internal combustion engines. These also occur when methanol is burned, especially since methanol burns at high temperatures. With reciprocating piston engines there is another problem in the cold start process, since the methanol remains liquid in this phase and is therefore unwilling to ignite.

Against the background of the entire problem, it is the object of the invention to provide a universally usable liquid fuel which is C0 ₂ -neutral and whose nitrogen oxide emissions are as low as possible during combustion.

Furthermore, the fuel should be capable of cold start. Another object of the invention is to propose the use of such a liquid fuel and a method for its production. Finally, the object of the invention is to provide a method for operating an externally ignited four-stroke reciprocating piston engine with such a liquid fuel.

According to the invention, this object is achieved with regard to the liquid fuel by the subject matter of claim 1, with regard to its use by the subject matter of claim 5, with regard to the manufacturing process by the subject matter of claim 6 and in

With regard to the operating method solved by the subject matter of claim 7.

The invention is based on the idea of _{specifying a C0 2} -neutral liquid fuel for universal use, in particular in internal combustion engines, preferably reciprocating piston engines, the liquid fuel comprising the following components as a mixture:

- between 15 vol% and 50 vol% water,

- between 3 vol-% and 16 vol-% of a cold start auxiliary material which has a boiling point at 1 atm of less than 64.7 ° C and - The rest, in particular between 34 vol% and 82 vol%, methanol from regenerative production.

The addition of water to methanol produced from regenerative production has the particular advantage that the combustion temperature of the liquid fuel is reduced in this way. At low combustion temperatures, fewer nitrogen oxides are produced, so that NO _c emissions can be reduced considerably.

Specifically, it is provided that the liquid fuel 15 vol% to 50 vol%, in particular 15 vol% to 45 vol%, in particular 15 vol% to 40 vol%, in particular 18 vol% to 35 vol%, in particular 20% by volume to 33% by volume, in particular 23% by volume to 30% by volume, in particular 23% by volume to 27% by volume,

Has water.

It is already known to spray water into the combustion chamber of a Flub piston engine in addition to a gasoline fuel in order to reduce the combustion temperatures. In the invention, however, the liquid fuel already contains the corresponding amount of water, so that a corresponding injection, in particular also an additional storage of the water in a motor vehicle, for example by means of a separate tank, is not necessary. The liquid fuel can thus be used particularly universally, namely also in internal combustion engines that do not have any additional water injection facility.

The problem of the cold start in fluid piston engines is solved with the universally usable liquid fuel according to the invention in that the liquid fuel comprises a cold start filler. The cold start F additive should have a boiling point at 1 atm of less than 64.7 ° C. It is particularly advantageous if the boiling point of the cold start filler is at most 60.degree. C., in particular at most 45.degree. C., particularly preferably at most 35.degree. C., in particular about 31.8.degree.

Preferably 3 vol% to 16 vol%, in particular 7 vol% to 16 vol%, in particular 8 vol% to 14 vol%, in particular 9 vol% to 12 vol%, of the mixture or of the Liquid fuel formed by the cold start F additive. Of the Cold start additive increases the ignitability of the liquid fuel. In particular, the cold start auxiliary substance can be ignited, as a result of which heat is generated, which leads to evaporation of the methanol or methanol-water mixture. A rapid ignition of the entire liquid fuel, in particular in a reciprocating piston engine, can thus be achieved.

The liquid fuel preferably has a methanol content between 34 vol% and 82 vol%. It is also possible that the proportion of methanol in the liquid fuel is between 34 vol% and 78 vol%, in particular between 40 vol% and 75 vol%, in particular between 45 vol% and 70 vol%, in particular between 48 vol% vol% and 67 vol%, in particular between 50 vol% and 63 vol%, in particular between 50 vol% and 60 vol%.

In order to maintain the C0 ₂ neutrality of the liquid fuel, it is preferably provided that the methanol comes from regenerative production. In particular, only renewable energy can be used to produce methanol, for example from photovoltaic systems or wind turbines. If carbon from the carbon dioxide in the atmosphere (atmospheric CO2) is also used to produce the methanol, the overall proportion of atmospheric carbon dioxide that contributes to global warming can be kept neutral with the liquid fuel according to the invention. When the liquid fuel is burned, only the same amount of CO2 is released that was previously removed from the atmosphere.

With regard to the C0 ₂ neutrality, it is particularly preferred if the cold start auxiliary is a methanol derivative. In this way, the cold start additive can be generated directly from the methanol. This makes the production of the liquid fuel particularly efficient and - with the exclusive use of renewable energy sources - also completely C0 ₂ -neutral.

Dimethyl ether, for example, can be used as a cold start auxiliary. It is particularly preferred if methyl formate is used as the cold start auxiliary. Methyl formate has a low boiling point and therefore ignites easily.

This largely solves the cold start problem. In addition, methyl formate burns extremely cleanly, so that overall combustion emissions are reduced. In order to be able to clearly distinguish the liquid fuel according to the invention from other fuels and also to avoid the liquid fuel being drunk, it is advantageous to provide that the mixture of the liquid fuel additionally contains a maximum of 1% by volume of additives, the additive preferably being blue color . In particular, the blue dye can be the only additive that is mixed in in addition to water, methanol and the catalyst.

In this context, it should be noted that the mixture preferably consists exclusively of the aforementioned components. In particular, the liquid fuel can exclusively contain water, a cold start auxiliary, methanol and, if appropriate, a blue dye. In this respect, the term “comprising” in the present application is generally to be understood not only as “having” but also as “containing” or “consisting of”.

A secondary aspect of the invention relates to the use of a previously described liquid fuel as fuel in a four-stroke piston engine with a compression ratio in the compression stroke of at least 1:16. Furthermore, the compression ratio in the compression stroke can also be at least 1:18, in particular 1:20 and 1:25 , amount.

In order to understand the use described above, it is essential that the liquid fuel be used as the main fuel in the four-stroke reciprocating piston engine. The liquid fuel therefore does not form an additive that is mixed with another fuel. Rather, the liquid fuel is used in such a way that the four-stroke flub piston engine is operated by means of the liquid fuel.

The liquid fuel that is used here, with its methanol content, has a property that is essential for increasing the efficiency of a four-stroke piston engine. Specifically, the methanol-based liquid fuel can be used with an otherwise unusually high compression ratio in gasoline engines. In the case of high compression, a considerable increase in efficiency is achieved, especially in operation with a balanced combustion air ratio (l = 1). This can also be done with little Liquid fuel use high performance can be achieved in a four-stroke reciprocating engine.

A particularly important aspect of the invention is the specification of a method for producing the liquid fuel described above. According to the invention it is provided in this regard that in the method according to the invention for producing the liquid fuel

- Hydrogen is provided by electrolysis of water, the electrolysis being operated exclusively with renewable electricity, in particular from a photovoltaic system;

the hydrogen is reacted with carbon to form methanol, the carbon being obtained from biomass or from atmospheric carbon dioxide; and

- The methanol, water and a cold start auxiliary is added, so that the liquid fuel between 15 vol% and 50 vol% water, between 3 vol% and 16 vol% of the cold start auxiliary, the cold start auxiliary having a boiling point at 1 atm of less than 64.7 ° C., in particular at most 35 ° C., and the remainder having methanol.

The above-described alternative mixing ratios of the individual components of the liquid fuel naturally also apply to the liquid fuel produced by the method described here.

If the method steps described above are complied with, it is ensured that the liquid _{fuel is overall C0 2 -neutral.} In particular, the methanol contained in the liquid fuel is produced _{100% C0 2 -neutral.}

The C0 ₂ neutrality is guaranteed by the fact that the hydrogen used to generate the methanol is provided by electrolysis, with only renewable electricity being used for this electrolysis. In the context of the present application, an electrical current is referred to as renewable current that was generated exclusively from one or more renewable sources. Such a source can be, for example, a photovoltaic system or a wind turbine. Other regenerative or renewable sources are also conceivable. The production of methanol is preferably achieved by reacting the hydrogen with carbon, using, for example, a methanol reactor. For this purpose, a selective catalyst is preferably used which suppresses the formation of methane during the reaction.

The methanol production can take place in particular in the low pressure process at pressures of 5 to 10 MPa and temperatures between 220 ° C and 320 ° C. It is particularly preferred if, during the production of the methanol, a methanol derivative, preferably methyl formate, is produced which can later be added to the methanol as a cold start auxiliary in order to produce the liquid fuel in this way.

A further secondary aspect of the invention relates to a method for operating an externally ignited four-stroke reciprocating engine, in particular a four-stroke Otto engine, which has an intake stroke, a compression stroke, a power stroke and an exhaust stroke, with air being passed into a combustion chamber in the intake stroke and an additional one described above Liquid fuel is fed into the combustion chamber so that an air-fuel mixture is formed, and the air-fuel mixture in the compression stroke at a compression ratio of at least 1:16, in particular at least 1:18, in particular between 1:20 and 1 : 25, compressed and ignited by an ignition spark.

In the method it can be provided that the liquid fuel is already mixed with the air in an intake pipe in front of the combustion chamber. Alternatively, the liquid fuel can also be injected directly into the combustion chamber.

If the four-stroke reciprocating piston engine is used to drive a generator to generate electricity for a hybrid drive of a hybrid vehicle, then the hybrid vehicle is operated as a whole in a CO2-neutral manner, since the liquid fuel is CO2-neutral. In the best case, even the combustion inside the four-stroke reciprocating piston engine can run so cleanly that the emissions resulting from the combustion contain fewer pollutants than the outside air previously present in large cities. This is achieved in particular by the proportion of water in the liquid fuel, which _{lowers the combustion temperature and thus the NO x} emissions. A particularly good emission result is obtained if a combustion air ratio in the compression stroke of 1, i.e. l = 1, is set in the operating method. With such a combustion air ratio, particularly clean combustion is guaranteed and, at the same time, the efficiency of the four-stroke reciprocating engine is additionally increased.

The invention is explained in more detail below with reference to the accompanying schematic drawings. Show in it:

1 shows a process diagram for the production of an inventive

Liquid fuel according to a preferred embodiment; FIG. 2 is a diagram showing the ratio of NO _x emissions at different combustion temperatures; FIG.

3 is a diagram showing the ratio of NO _x emissions with different water proportions in a diesel reciprocating engine; and FIG. 4 is a diagram showing the relationship between

Compression ratio and compression end temperature in comparison of different liquid fuels.

In Fig. 1, a preferred process for the production of the liquid fuel according to the invention is shown. The starting point is essentially water, which is first split into hydrogen and oxygen, preferably by means of electrolysis. The electrical current required for the electrolysis is preferably produced by means of regenerative energy sources, in particular photovoltaics or wind power. This means that the electrolysis is climate-neutral or CO2-neutral. The oxygen produced by electrolysis can be released into the atmosphere. Alternatively, the oxygen can also be stored and reused for later process steps. The hydrogen is then converted to methanol in a methanol reactor by adding carbon. The carbon source can form carbon dioxide or carbon monoxide. A mixture of carbon dioxide and carbon monoxide is also possible as a source for the carbon that is used for the methanol conversion. The carbon dioxide or CO2 or the carbon monoxide (CO) can be obtained from biomass. Alternatively, it is possible that atmospheric CO2 or CO is used for the methanol conversion.

It is particularly preferred to obtain CO2 or CO from flue gas emissions from power plants. In this way, for example, CO2 emissions from coal-fired power plants or natural gas power plants that are still in operation can be reduced. The CO2 produced there can therefore be used for the production of methanol. If atmospheric CO2 is used, the amount of CO2 in the atmosphere is first reduced during the production of the liquid fuel. The CO2 is only released again when the liquid fuel is burned, but only in the amount previously removed from the atmosphere. Thus, the liquid fuel is completely C0 ₂ -neutral.

In the context of methanol production, methyl formate can also be produced by further conversion. At normal pressure (1 atm), methyl formate has a boiling point of around 32 ° C, specifically 31.8 ° C. In liquid fuel, which is preferably called "aFuel", methyl formate with its low boiling point ensures that the liquid fuel can ignite easily. In particular, the methyl formate can ignite so that temperatures are quickly reached at which the methanol is in a vaporous state passes over, so that it finally ignites.

The liquid fuel is then mixed from the methanol obtained during production and the methyl formate with the addition of water.

The mixture preferably contains between 3 vol% and 16 vol% methyl formate as a cold start auxiliary. Between 15 vol% and 50 vol% of the liquid fuel is formed by water. The rest is methanol. The proportion of methanol is preferably between 82% by volume and 34% by volume.

When using the liquid fuel according to the invention in reciprocating engines, there are very special advantages. Thus, FIG. 2 shows that the combustion temperature has a considerable influence on the NO _c emissions. Specifically, the amount of NO _x emissions increases exponentially as the combustion temperature rises. High combustion temperatures and the associated high NO _x emissions arise in particular when burning petrol ("gasoline"). Diesel fuel burns at lower temperatures and thus releases less NOx In comparison to the aforementioned fossil fuels, there is a further, significant reduction in NO _x emissions.

From the diagram according to FIG. 3 it can also be derived what effects the proportion of water in the mixture of liquid fuel has _{on the NO x emissions.}

3 shows specifically the course of the NO _x emissions with different proportions of water that is injected into a diesel fuel in a diesel engine. With this very complex technology, the diesel engine has an additional injection nozzle for water, so that finely atomized water can be fed into the diesel-air mixture in a combustion chamber. This method is comparatively complex, but leads to a noticeable reduction in the combustion temperature and thus to a reduction in NO _x emissions.

3 clearly shows that the NO _x emissions decrease significantly with increasing water content. It is to be expected that this effect will also be achieved with the liquid fuel according to the invention, the water already being contained in the liquid fuel. Complex water injection technology including a separate water storage tank is therefore not required.

Specifically, it can be seen that with 50% load on the four-stroke reciprocating engine, the NO _x emissions are more than 10 g / kWh with a water content of around 3%. If the water content increases to over 30%, the NO _x emissions drop to less than 4 g / kWh. A high proportion of water in the liquid fuel is therefore advantageous in order to significantly reduce _{NO x emissions.} Adding the cold start additive to the liquid fuel mixture also has particular advantages in four-stroke reciprocating engines. The cold start additive makes the liquid fuel ignitable, so that good combustion is achieved despite a high water content. A water content of 30% by volume and higher is therefore easily possible.

The temperature in the combustion chamber of the four-stroke reciprocating engine is decisive for reducing NO _{x emissions.} 4 clearly shows that the use of methanol as the main component of the liquid fuel compared to previous gasoline fuels already achieves a significant reduction in the compression end temperature in the combustion chamber. It can also be seen that this reduction is significant even at higher compression ratios.

Conventional petrol has a compression end temperature of over 600 ° C with a combustion air ratio of 1 (l = 1) and a compression ratio of 1:17. However, under the same conditions, methanol shows a compression end temperature of less than 400 ° C. By reducing the temperatures in the combustion chamber, it is avoided that a large number of nitrogen oxides are formed.

The reduction of NOx is promoted by the fact that a four-stroke reciprocating engine operated with the liquid fuel is preferably operated continuously with a combustion air ratio of 1 (l = 1), so that essentially all oxygen atoms are "consumed" during combustion "Unused" oxygen that could form NOx compounds.

As a result, a significant reduction in NO _x emissions is achieved through the combination of methanol and water. By increasing the

Compression ratio compared to gasoline engines also achieves a particularly high level of efficiency. Since the liquid _{fuel is produced C0 2} -neutral, a completely C0 ₂ -neutral drive system can g

Claims

EXPECTATIONS

1. C0 ₂ -neutral liquid fuel for universal use, especially in internal combustion engines, preferably reciprocating engines, comprising the following components as a mixture:

- between 15 vol% and 50 vol% water,

- between 3 vol-% and 16 vol-% of a cold start auxiliary material which has a boiling point at 1 atm of less than 64.7 ° C and

- The rest, in particular between 34 vol% and 82 vol%, methanol from regenerative production.

2. Liquid fuel according to claim 1, characterized in that the cold start auxiliary is a methanol derivative.

3. Liquid fuel according to claim 1 or 2, dad u rch geken nzeich net that the cold start auxiliary is methyl formate or dimethyl ether.

4. Liquid fuel according to one of the preceding claims, dad u rch geken nzeich net that the mixture additionally has a maximum of 1% by volume of additives, with blue dye being provided as, preferably the only, additive.

5. Use of a liquid fuel according to one of the preceding claims as fuel in a four-stroke reciprocating engine with a compression ratio in the compression stroke of at least 1:16, in particular at least 1:18, in particular between 1:20 and 1:25.

6. A method for producing a liquid fuel according to any one of claims 1 to 4, wherein

- Hydrogen is provided by electrolysis of water, the electrolysis being operated exclusively with renewable electricity, in particular from a photovoltaic system; the hydrogen is reacted with carbon to form methanol, the carbon being obtained from biomass or from atmospheric carbon dioxide; and

- The methanol water and a cold start auxiliary is added, so that the liquid fuel between 15 vol% and 50 vol% water, between 3 vol% and 16 vol% of the cold start auxiliary, the cold start auxiliary a Has a boiling point at 1 atm of less than 64.7 ° C, and the balance has methanol.

7. A method for operating a spark-ignited four-stroke reciprocating engine, in particular a four-stroke Otto engine, which has an intake stroke, a compression stroke, a power stroke and an exhaust stroke, with air being passed into a combustion chamber in the intake stroke and additionally a liquid fuel according to one of claims 1 to 4 is fed into the combustion chamber, so that an air-fuel mixture is formed, and in which im

Compression stroke, the air-fuel mixture is compressed at a compression ratio of at least 1:16, in particular at least 1:18, in particular between 1:20 and 1:25, and ignited by an ignition spark.

8. The method according to claim 7, d a d u r c h g e k e n n z e i c h n e t that a combustion air ratio in the compression stroke is 1 (l = 1).