NO179298B - Methods and facilities for providing mechanical energy - Google Patents

Abstract

The invention concerns a process for the continuous conversion of energy chemically bound in a starting fuel based on C-H compounds into useful mechanical energy. For this purpose, a gas turbine is used, and in order to obtain a high mechanical efficiency combustion of at least part of the fuel is carried out with a fuel obtained from the starting fuel by means of an endothermic reaction, the reaction chamber being heated for the endothermic reaction either by means of compressed combustion air heated by the exhaust gases or by means of the hot exhaust gases themselves.

Description

The invention relates to a method for providing mechanical energy as stated in the introduction to patent claim 1, and also relates to a device for carrying out the method as stated in claim 13.

In most thermal power plants, for the production of electrical energy, superheated steam is first provided by burning fossil fuels in boiler plants. This steam is released in steam turbines and converted into mechanical energy. The steam turbines are connected to electrical generators, so that this mechanical energy is converted into electrical energy. This latter transformation takes place with an efficiency of well over 90Sé. However, the efficiency for the conversion of the chemically bound energy in the fuel used into mechanical energy is very modest, as the turbine efficiency, even with large turbines, is a maximum of around 37% and you also have to take into account losses in the boiler. In many cases, you can therefore only use approximately 35% of the heat released during combustion, for the efficient production of electricity, while around 65% is lost as waste heat and can only be used for pure heating purposes.

In recent times, it has been possible to achieve a significant increase in the overall efficiency, whereby a combination of gas turbines and steam turbines has been used to convert the heat energy into mechanical energy. The hot combustion gases are first released in gas turbines and the heat in the exhaust gas from these gas turbines is used to provide steam for the steam turbines. Further possibilities for improvement consist in leading the de-stressed steam flowing out of a steam turbine back to the combustion chamber in the upstream gas turbine and thus providing a larger volume flow for operation of the gas turbine. These measures have enabled a total efficiency for the conversion of thermal energy to mechanical energy in larger plants (over 50 MW) in the order of magnitude of around 48 to 5056.

Such a combined gas/steam turbine process is known, for example, from DE 33 31 153 Al. To provide the necessary hot combustion gases for the gas turbine, ordinary "flowing" fuels are used, i.e. liquid or gaseous coal water substances. In order to largely avoid the formation of nitrogen oxides, the combustion chamber temperature is lowered by a part of the steam provided with the heat in the gas turbine exhaust gas being fed into the combustion chamber. With a total output of 300 MW, an efficiency of 48% can be achieved in this process.

In the journal VGB Kraft twerkstechnik 68 (No. 5, May 1988, pages 461-468) a combined gas/steam turbine process is described in connection with a coal gasification. The combustible gas provided by the coal gasification is, after cleaning, partially combusted with compressed air in a first combustion chamber. The thereby provided hot combustion gases are first used for superheating water vapor for the coal gasification and for heating the allothermal coal gasification, before it is released in a first gas turbine, which in turn drives a compressor for the necessary combustion air. The other part of the combustible gas produced during the coal gasification is burned in a second combustion chamber and is then de-stressed in a second gas turbine, which is connected to a further compressor for the combustion air required in the second combustion chamber and to an electric generator for the provision of electrical energy. The de-stressed turbine exhaust gas from the second gas turbine is used together with the de-stressed gas from the first gas turbine (compressor-drive turbine) for steam production before it goes out into the atmosphere. This steam is released in a steam turbine, which is also connected to a generator, for the production of electrical energy. A part of the steam is taken out from the steam turbine after a partial relaxation and is then used for the coal gasification after the already mentioned overheating with the combustion gases in the first combustion chamber.

In this well-known plant, coal is used as the starting fuel. The coals are first made usable for a gas turbine process by first gasifying them. From a technical point of view, this transformation is absolutely necessary because of the ash content arising during combustion, which will have a destructive effect on a gas turbine. Fuels based on coal-hydrogen compounds, on the other hand, are in liquid or gaseous form, contain no ash and can therefore be used directly in a combined gas/steam turbine process. A characteristic of these known plants is that the combustion gases are first fed in two completely independent sub-streams in different sub-processes, before they are used together for steam production at the end of the process. The net efficiency of this plant is stated at around 42%, with an internal energy requirement for the process management of around 7.5%.

A further combined gas/steam turbine process for the provision of electrical energy, where coal gasification is first carried out, is known from US-PS 4,478,039. There, the provided gas is burned under excess pressure in a combustion chamber. The resulting hot combustion gases are then released in a gas turbine, which drives an electric generator and a compressor for the compression of the combustion air. The decompressed turbine exhaust gas is then used for heating the coal gasification plant and for producing steam for the steam turbine process. The steam turbine also drives an electric generator. Nothing is said in the patent document about the utilization of starting fuels based on coal-hydrogen compounds.

Furthermore, from DE 37 40 865 Al, a method and a device for the extraction of hydrogen is known, in that a gaseous starting fuel, i.e. a coal-hydrogen compound, is converted in a steam reforming into a hydrogen-rich gas with an increased absolute heat value compared to the flow rate of the starting fuel.

By "absolute heating value" here, as usual, is not to be understood a heating value calculated on a unit of weight. On the contrary, this means the total amount of heat of combustion that is contained in a specific quantity of the starting fuel or in a quantity of the converted fuel, and which is produced by the endothermic conversion of the same amount of starting fuel. In a steam reforming, the total amount of the converted fuel is increased significantly compared to the original amount of starting fuel, as a result of the water vapor portion added during the conversion, so that the calorific value calculated with regard to the weight will be less than originally, even though during the combustion of the converted fuel releasable amount of heat has become greater.

The raw gas provided in this process according to DE 37 40 865 Ål is processed in a purification step (for example a pressure exchange absorption plant) for the extraction of pure hydrogen gas, where pollutants (for example CO, COg, HgO, unconverted coal water substances) are separated and carried away as waste gas. This combustible waste gas, which necessarily also contains certain residual proportions of hydrogen gas, is after compression in a compressor to a higher pressure than the fuel gas, for example burned with compressed air in the heating chamber of the indirectly heated steam reformer. As a result of the extensive separation of the water substance from the raw gas, the absolute heating value of the exhaust gas stream in the purification stage will drop significantly in relation to the absolute heating value of the raw gas and will be below the heating value of the starting fuel used. It is therefore often necessary to provide direct co-combustion of a partial stream of the output fuel during the heating of the steam reformer. After the heating of the steam reformer, the combustion exhaust gas is fed as a moderator gas for lowering the temperature in a combustion chamber, where a partial flow of the output fuel is combusted with compressed air. The stream of combustion exhaust gases leaving this combustion chamber is then de-stressed in a gas turbine. The gas turbine will provide the necessary compressor drive energy in the process and also enables the production of electrical energy with the help of an associated generator.

In this known method, the conversion of the starting fuel is fat in and of itself only because the aim is to provide hydrogen gas, which is necessary for arbitrary applications outside the process. There is nothing in DE 37 40 865 Al to indicate that such an endothermic fuel conversion would also be advantageous when the converted fuel is then to be burned, in order to provide mechanical energy. The combustion of the converted fuel used in this known process is only carried out in order to be able to utilize a side product. It is important to be aware that during combustion only a portion of the combustible components originally present in the converted fuel will be present, because the hydrogen portion, which makes up the majority of the absolute heating value, has already been separated to a large extent. For this reason, the purely calculable ratio between the usable mechanical/electrical energy provided and the amount of chemically bound energy contained in the used starting fuel is very small in this process - less than 10%.

From EP 0 318 122 A2, a method and a plant for providing mechanical energy from gaseous fuels is known, where the mechanical energy usable, for example for power production, is exclusively supplied from a gas turbine. This gas turbine, which is particularly designed for an area of 50 to 3000 kW, will have an efficiency of approx. 42%. It is a prerequisite that combustion air is first compressed in a compressor. This compressed combustion air is then heated in an exhaust gas heat exchanger, partially de-stressed in a first gas turbine, which only drives the compressor, and then led to a combustion chamber, where fuel is burned with this combustion air. The hot exhaust gas produced during combustion drives a second gas turbine, which supplies the actual usable mechanical energy. The still hot exhaust gas flowing out of the second gas turbine is used to operate the exhaust gas heat exchanger for heating the compressed combustion air.

From US 3,167,913 there is also known a plant with a single combustion chamber, in front of the compressor turbine, i.e. the high-pressure part, in the turbine plant. Such high-pressure systems require that the combustion chamber be dimensioned for high pressures.

In order to increase turbine efficiency, high combustion temperatures are sought, whereby more harmful substances are produced. As a result of the high compression of the combustion air, it will have a high temperature, which must also be taken into account during the design of the exhaust gas heat exchanger. This not only increases the construction costs, but the overall efficiency also deteriorates.

The purpose of the present invention is to further develop a method and a plant of this type in such a way that the efficiency for the conversion of the energy contained in a fuel based on C-H compounds (lower calorific value) into mechanical energy amounts to over 50% for smaller plants (50 to 3000 kW) and at least 55% in larger plants. In the following, efficiency shall always mean the "mechanical" efficiency, i.e. the ratio between the usable mechanical energy provided in the turbine and the energy introduced in the output fuel (on the basis of the lower heating value Hu).

This purpose is achieved with the characteristic features stated in patent claim 1. Advantageous further developments of this method are stated in the independent claims 2-12. A plant according to the invention, for carrying out the method, is characterized by the features indicated in the characteristic in patent claim 13, and advantageous further developments of the plant are indicated in the independent claims 14-19.

A significant inventive feature is that the plant design known from EP 0 318 122 A2 is expanded with a reactor for an endothermic chemical reaction, where the used fuel (output fuel) is converted into a higher value fuel, which is then combusted with compressed air from the compressor.

Here, the heat energy for operating the reactor is preferably taken from the exhaust gas heat to those from the gas turbine, where the usable mechanical energy is provided, flowing exhaust gases. However, other hot process gas streams can also be used for heating the reactor. In the case of exhaust gas heat utilization for the reactor, this cooled exhaust gas can for example also be used in an exhaust gas heat exchanger for heating the compressed combustion air.

With the conversion of the output fuel, it is achieved that, in the same way as in a heat pump, heat from the exhaust gas in the gas turbine or another heat flow is raised to a higher "potential temperature level", so that this heat becomes better technically usable than heat with a lower temperature. This "raising" of the temperature level takes place in the form of an increased absolute heat value for the new fuel (for example E2 and CO) formed during the reaction in the reactor of the original fuel (for example natural gas).

The method and the plant according to the invention make it possible to systematically capture and efficiently utilize the waste heat that occurs in the process. There is a rather special advantage in that the endothermic reaction for providing the higher value fuel, which reaction can be carried out in particular as a steam reforming, for example of natural gas, can be carried out at relatively low temperatures. Usually such steam reforming is carried out on a large technical scale only at temperatures in the range of 780 to 900°C. According to the invention, an upper temperature limit of 780°C or even better 700 or even 650°C should not be exceeded.

The disadvantage, that with the lower temperature you have to count on a poorer conversion rate for the original fuel, i.e. an increase in the proportion of unconverted fuels, is more than canceled out by the advantage that lies in a better utilization of the waste heat from the gas turbine or the heat in a different process hot gas flow during the reactor heating, and a reduction of the temperature to the fresh steam required for the endothermic reaction. The reduced temperature level also entails advantages with regard to the costs of a plant according to the invention, because the thermal stresses on the materials used are lower than in the previously known technique.

Of particular decisive importance is also the fact that the fuel combustion, for example by nozzle delivery of water or steam in the combustion chamber or chambers in the plant, can be affected so that nitrogen oxides do not occur or possibly only occur in smaller quantities. Here, the flame temperature is limited to values of a maximum of 1700°C (adiabatic flame temperature) and the inlet temperature in the gas turbine is limited to a maximum of 1250°C, so that the implementation of the new method is made possible in an exceptionally environmentally friendly way, without the need for an expensive nitrogen removal plant. All this is made possible as a result of the inventive integration of fuel conversion and the production of mechanical energy from the heat released by fuel combustion. This enables such efficient utilization of heat flows that it is possible to achieve previously unattainable efficiencies. Typical values are in the range 50 to 70%, as small plants will be in the lower range, while larger plants will be in the upper range. The new facilities are particularly well suited for decentralised, consumer-close production of electricity and thus offer the additional advantage that losses in energy transport over larger distances and/or as a result of power transformation are largely avoided. Experience shows that these losses for large power plants amount to approximately 10% of the electrical energy provided.

For the new method, there are two main variants which are considered particularly preferred. In the first main variant, as already mentioned, the compressed combustion air is heated in an exhaust gas heat exchanger before it is introduced into the combustion chamber, the exhaust gas heat exchanger being supplied with exhaust gas from the gas turbine which supplies the usable mechanical energy. The wastewater heat exchanger is preferably designed as a recuperator.

The greater the amount of heat exchanged in this recuperator per time unit is, the stronger the building volume of this heat exchanger unit grows. In larger plants of the inventive type (in the range from approx. 50 to 80 MW), the recuperator will be very large and correspondingly expensive in comparison with the other plant parts. For larger installations, the second main variant is therefore recommended, where a recuperator is completely dispensed with.

In the second main variant, the gas turbine's exhaust gas (possibly after heating the reactor for the fuel conversion) is used for steam production. This steam is superheated by means of a hot gas flow present in the process and is then de-stressed in a steam turbine for the provision of additional mechanical energy, as is known from the so-called "Combined-Cycle" power plants. The efficiency of the process will admittedly be somewhat lower in such large plants than it will in principle be possible to achieve in a plant according to the first main variant, but the plant costs are in return significantly lower.

The invention will be explained in more detail below with reference to the drawings, where: Fig. 1 shows a plant with a recuperator, and fig. 2 shows a plant with a steam turbine.

In the one in fig. 1 embodiment of the invention, combustion air is sucked in through a pipeline 9 by means of a compressor 3a in a compressor unit 3, which also contains a second compressor 3b. The compressed combustion air is intermediately cooled in a cooler 4 and is then compressed to an even higher pressure in the second compressor 3b. Both compressors 3a and 3b are mechanically connected to a compressor drive gas turbine unit 2 by means of shafts 24,25. Through a pipeline 10, the compressed combustion air from the second compressor 3b goes to an exhaust gas heat exchanger 8 designed as a recuperator and is there after indirect heating to a first combustion chamber 5 through a pipeline 11.

Into the combustion chamber 5, a portion of a fuel, which is provided in a reactor 7 as a result of an endothermic reaction of an output fuel, is introduced through a fuel line 20, and this portion of fuel is burned in the combustion chamber 5. The hot gas mixture formed, which in addition to the combustion products also contain excess combustion air, are passed through the hot gas line 12 to the compressor propellant gas turbine unit 2 and are there partially relaxed and thereby somewhat cooled while releasing the drive energy required for the compressor unit 3.

This still hot gas mixture then passes through the hot gas line 13 into a second combustion chamber 6, where fuel is likewise introduced from the fuel line 20. In this second combustion chamber 6, combustion takes place with excess air, so that the exhaust gas is again brought up to a higher temperature overall.

The hot exhaust gas produced during this combustion is led through a hot gas line 14 to a gas turbine 1, which provides the usable mechanical energy, and from the gas turbine the hot gas exits after relaxation through the exhaust line 15. The compressor drive gas turbine unit 2 and the gas turbine 1 can be arranged on one and the same shaft and can even be designed as a single turbine unit to simplify the entire plant. It is also possible with several compressor stages to have these partially driven by the gas turbine 1. An optimal coordination of compressors and turbines can then be carried out.

By nozzle introduction of, for example, water or water vapor into the combustion chambers 5 and 6, the adiabatic flame temperature can be limited to below 1700°C and the inlet temperature in the gas turbine 1 can be limited to approx. 1250°C, in many cases even to even lower values of down to 800°C, at which temperatures significant amounts of nitrogen oxides do not occur. In this context, it is a great advantage of the invention that the formation of nitrogen oxides is nevertheless significantly reduced by the fact that converted fuels with a higher absolute heating value produced in the endothermic reaction are burned to a large extent instead of the starting fuel. This will in itself (depending on the excess air) give an adiabatic flame temperature that is 300-550°C lower than the adiabatic flame temperature when burning the starting fuel.

It is also possible to carry out the combustion of the supplied fuel in a single combustion chamber 5, so that the combustion chamber 6 can be omitted. When using two combustion chambers, the measures for deliberately lowering the flame temperature can also be limited to the second combustion chamber 6, because the nitrogen oxides formed in the first combustion chamber 5 are largely decomposed as a result of the heat effect during the subsequent second combustion. This means that during the first combustion one can work with high exhaust gas temperatures and thus with favorable conditions for the compressor drive gas turbine with a view to achieving the highest possible turbine efficiency, without this leading to a higher NOX content. The controlled temperature control is therefore primarily of particular importance for the last combustion stage.

The mechanical energy provided by the relaxation in the turbine 1 can be utilized with the output shaft 26 and can, for example, be used to operate a generator G for the provision of electric current. The exhaust gas, although somewhat cooled during the relaxation, but still hot, will go through the exhaust gas line 15 into the heating area of the indirectly heated reactor 7 for the endothermic reaction.

With the help of this endothermic reaction, which can for example take place as steam reforming, a new fuel with a higher absolute heating value is formed from the starting fuel, which has a specific absolute heating value. If it concerns steam reforming of natural gas, which is, for example, supplied through the fuel line 18, then a steam line 19 is also used for the introduction of steam into the reactor's 7 reaction space.

As a rule, it will be appropriate to mix the steam with the fuel in advance. The provided new fuel, which consists of a mixture of Etø, CO, COg, unconverted CH4 and water vapour, is fed through the supply line 20 from the reaction space to the combustion chambers 5 and 6 and is burned there as described above. It is of course also possible, for optimization of the combustion processes (temperature, mass flow) in the combustion chambers 5 and 6, to add a proportion of the starting fuel to the higher value fuel and only then carry out the combustion. A mixture is then suitably used with a proportion of at least 50%, preferably even more than 80% of the converted fuel. The less converted fuel is present, the more tendentially the efficiency is affected. The principle that the fuel burned in total must have a higher calorific value than the starting fuel is maintained in all cases. Part of the higher-quality fuel can of course also be removed from the process and used in other processes.

In the aforementioned steam reforming of natural gas (mainly CE4), the absolute heating value of the fuel is increased approx. 30%. In the case of a hydrogenation of the starting fuel toluene, the heating value increase amounts to approx. 15$. Instead of steam reforming, the endothermic reaction can, for example, also take place by means of dehydrogenation. With ethane as the starting fuel, this will give heating value increases of approx. 10-20% and when using methanol see increases of approx. 20 to 30%. A further example of an endothermic reaction is the steam cracking of arbitrary coal-hydrogen compounds, (for example biogas, LPG, naphtha, kerosene, etc.).

Precisely this latter possibility is interesting, because it will enable the alternating utilization of a large number of different fuels for the provision of the mechanical energy, without the gas turbine having to be converted to the new fuel by changing the fuel.

The endothermic reaction is best carried out at temperatures below 780<*>C and best below 700°C. The exhaust gas used for heating leaves the heating area of the reactor 7 through the exhaust gas line 16 and still has a relatively high temperature. According to the invention, it is used, for example, for heating the exhaust gas heat exchanger 8, where the compressed combustion air is heated. The cooled exhaust gas finally passes through the exhaust gas line 17 out of the exhaust gas heat exchanger 8.

In the case of an endothermic reaction where the use of steam is necessary, the new method can certainly be operated as a closed system, since the steam can be produced using the heat present in the individual hot process volume streams. To achieve an even higher overall efficiency in the process, at least part of the required fresh steam can also be supplied to the reactor from outside, from arbitrary steam sources. In the plant diagram, dashed lines optionally indicate relevant steam generators 21,22,23, which can be operated alternatively or simultaneously. The steam generator 21 is built into the exhaust gas line 17 at the end of the plant and can therefore only provide steam with a relatively low temperature. At this location, a heat exchanger can possibly be arranged for preheating the output fuel (or a fuel/steam mixture) or for feed water preheating for steam remst i11 ingen.

Another possible location for a steam generator 22 is suggested between the exhaust gas heat exchanger 8 and the reactor 7, in the exhaust gas line 16.

A preferred location is that shown for the steam generator 23, between the compressor drive gas turbine unit 2 and the second combustion chamber 6, as such a location will have a positive effect with regard to reducing the combustion temperature in the combustion chamber 6. If several simultaneous steam generators 21 are arranged to 23, then these can be connected in such a way that, for example, one (21) can produce steam at a relatively low temperature and then superheat this in another producer (for example 22 and/or 23) to achieve a higher temperature. In principle, the heat from an intermediate cooling during the compression of the combustion air (cooler 4) can also be used for steam production.

In the form in fig. 1, the reactor 7 is connected to the exhaust gas lines 15, 16 from the gas turbine 1. However, it is also possible to heat the reactor with a hot gas stream taken out earlier in the process. The reactor 7 can thus in principle also be connected to the lines 11,12,13 or 14. A temperature reduction of the hot gas stream will indeed reduce the turbine efficiency of turbines 1 and 2 respectively, but at the same time NOx formation is also reduced. Therefore, the method parameters must be coordinated with each other with a view to achieving the most optimal effect possible.

For starting the plant from the cold state, where there is neither a hot gas stream nor sufficient converted fuel available, it can alternatively or at the same time be ensured that at least over a certain period of time the original fuel (for example natural gas) can be introduced and burned in the combustion chamber 5 and in the heating area in the reactor 7.

The corresponding (not shown here) special fuel lines can also be connected for a short time when and if the heat available in these aggregates is temporarily insufficient. The plant's overall operation can thereby be regulated in a very simple way. In order to achieve better regulation and an optimization of the overall system, it can also be ensured that part of the energy provided in the gas turbine 2 for the compressor operation is emitted externally as usable mechanical energy.

In fig. 2, the second main variant of the new method is shown schematically. Functionally similar installation parts have largely the same reference number as in fig. 1. What has been said before in fig. 1 therefore applies accordingly to such components, and below only the differences will be described in more detail.

The significant difference compared to fig. 1 is that the exhaust gas heat exchanger 8 used as a recuperator for the combustion air preheating is missing and that a system for providing superheated steam has been installed instead, which is utilized in a steam turbine 31 for providing mechanical energy. This steam production system consists of a steam boiler 30 and a steam superheater 29.

The steam boiler 30 is heated with the residual heat in waste gas from the gas turbine 1, after this waste gas has passed through the reactor's 7 heating room and has given off heat there. The supplied steam goes through pipeline 37 to the superheater 29 and from there through pipeline 38 to the steam inlet side of the steam turbine 31. The de-stressed steam is led from the steam turbine 31 to a condenser 32. The condensate pump 33 brings the condensed water to a degassing device 34.

From there, the prepared boiler water goes by means of the boiler feed pump 35 through a pipeline to the steam boiler 30. Thus, the steam/water system represents an essentially closed circuit system. Water loss is compensated with a water addition not shown.

Such water losses occur in particular when, as indicated in fig. 2 with the dotted line 36, steam is taken out after the high-pressure part of the steam turbine 31 and is led to the combustion chambers 5 and 6 for temperature regulation and mass flow increase there. The pipeline 19, which can also be considered optional, can in the same way take steam from the circuit system and lead it into the reaction chamber of the reactor 7. However, this steam can also, as mentioned above in connection with fig. 1, is provided elsewhere in the facility or supplied from outside. The water required for filling the steam/water circuit can be taken from the condensate that is separated in the exhaust line 17.

It should also be mentioned that the supply of compressed pre-combustion air to the first combustion chamber 5 in fig. 2 is denoted by the reference number 27 and that the hot gas line from the steam superheater 29 to the second combustion chamber 6 is denoted by the reference number 28.

In principle, this also applies to the variant in fig. 2 that the reactor 7 can be placed in another place in the hot gas lines. A preferred solution is one where the locations of the reactor 7 and the steam superheater 29 are interchanged.

A further advantageous design according to the invention, which is not shown in fig. 1 and 2, relate to the utilization of the hot exhaust gas released in the gas turbine 1. This exhaust gas usually still contains a considerable proportion of C^, because the combustion is carried out with an excess of C^. The exhaust gas can therefore, for example, be used as cathode gas for C2 supply of a fuel cell system, where electric current is produced. In such fuel cell systems, it is an advantage that the cathode gas is supplied approximately at a temperature that corresponds to the operating temperature of the fuel cells. Depending on the fuel cell system type, the operating temperature will be at a different level. Therefore, the fuel cell system is connected at a suitable place in the exhaust gas pipeline 15,16,17, i.e. the cooling of the de-stressed exhaust gas, with heating of other media flows necessary in the process (air preheating, steam production, reformer heating) is carried out down to approximately the desired operating temperature, after which the exhaust gas flow or part of it is fed into the cathode compartment of the fuel cell system. The fuel cell system can be supplied with fuel from any E2 gas source (for example, a pipeline or a gas accumulator). A partial flow of an H2-rich gas provided in the reactor 7 can also be fed into the anode compartment of the fuel cells.

The way the new method works will be explained in more detail below in the form of an implementation example. A facility as shown in fig. 1. The heat exchanger 21 is used for providing water vapor and for preheating natural gas, while the heat exchanger 22 is used for superheating the water vapor/natural gas mixture, before this mixture is fed to the steam reformer 7. The natural gas used as output fuel has a line pressure of 20 bar, and the water has a temperature of approx. 15°C. The steam/carbon ratio (mol/mol) is 2.0. Otherwise, the method parameters have been selected in accordance with the tabular arrangement set out below. In the list, reference numbers taken from fig. 1.

During a steam reforming of the natural gas consisting mainly of methane, approx. 12% of the methane portion was not converted and was burned in combustion chambers 5 and 6 in its original form. With the exception of the energy for the compression of the natural gas, which was available with sufficient line pressure, the entire energy requirement in the process was covered by the process itself, so that no energy supply from outside was necessary. The thereby achieved total efficiency, i.e. the ratio between the electrical energy provided and the energy quantity of fuel used on the basis of the lower calorific value, was 65%, i.e. the efficiency was at a previously unachieved level of order of magnitude. In addition, the exhaust gas excelled at a low nitrogen oxide content, without the use of nitrogen removal measures.

The great advantage achieved with the invention is considered to be that it not only enables a drastic increase in the degree of efficiency during the production of mechanical energy with the starting point in fuels based on coal-hydrogen compounds, but that this increase in efficiency can be achieved at the same time with a reduction of the proportion of harmful substances in the exhaust gas. In addition, the new plant's special applicability in connection with decentralized electricity production results in a strong reduction of the losses arising from the use of conventional large-scale power plant technology as a result of electricity transport over greater distances and transformation of the electricity.

Claims (19)

1. Process for the continuous conversion of an output fuel based on C-H compounds chemically bound energy into usable mechanical energy, where combustion air is compressed (3), the drive energy for the compression of the combustion air is extracted using a compressor drive gas turbine unit (2), where at least the volume flow of the compressed combustion air is conducted under partial relaxation, the hot exhaust gas produced by burning fuel with the compressed combustion air is de-stressed in a gas turbine (1), with which at least part of the usable mechanical energy is provided, and the residual heat of the exhaust gas flowing from the gas turbine (1) is used for heating a media stream used in the process, e.g. the output fuel, the starting fuel in an endothermic reaction (7) is converted into a converted fuel with a higher absolute heat value, the combustion takes place with the use of the converted fuel, with or without the addition of starting fuel f, as the separate combustible components in the converted fuel produced during the conversion are quantitatively completely or at least predominantly still contained in the converted fuel to be burned, and the heating of the reaction space (7) for endothermic reaction either takes place with the help of the compressed combustion air, which has previously been brought up to a higher temperature level by means of indirect heat exchange with the hot exhaust gas from the combustion, or with the total flow of the hot exhaust gas produced during the combustion , before or after its relaxation, characterized in that the combustion takes place in two stages, in which the hot exhaust gas provided in the first stage (5) and showing a high excess of air is partially relaxed in the compressor drive gas turbine unit (2) and is then led to the second stage (16) together with further converted fuel, and by the fact that the hot exhaust gas provided in the second stage (6) is relaxed in the gas turbine (1), releasing usable mechanical energy. 2. Method according to claim 1, characterized in that the hot exhaust gas after the relaxation in the gas turbine (1) is used for heating the reaction space (7) for the endothermic reaction. 3. Method according to claim 1 or 2, characterized in that the residual heat of the hot exhaust gas released in the gas turbine (1) is used for the heating (8) of the compressed combustion air. 4. Method according to claims 1 and 3, characterized in that the hot exhaust gas, before it is partially de-stressed in the compressor drive gas turbine unit (2), is used for heating the reaction space (7) for the endothermic reaction. 5. Method according to claims 1 and 3, characterized in that the hot exhaust gas after its partial relaxation in the compressor drive gas turbine unit (2), but before the relaxation in the gas turbine (1), is used for heating the reaction space (7) for the endothermic reaction. 6. Method according to one of the claims 1-5, characterized in that the composition of the media introduced in the combustion step or steps is set in such a way to reduce the formation of nitrogen oxides that a flame temperature of less than 1700°C occurs (adiabatic flame temperature) and the inlet temperature in the gas turbine (1) is below 1250°C. 7. Method according to claim 6, characterized in that the regulation of the outlet temperature takes place by nozzle introduction of water or steam into the combustion chamber (5,6). 8. Method according to one of claims 1, 2 or 4-7, characterized in that residual heat in the hot exhaust gas released in the gas turbine (1) is used for the production of steam, which is superheated (29) while utilizing the heat previously present at a higher temperature level exhaust gas flow and is used to operate a steam turbine (31), which also provides usable mechanical energy. 9. Method according to claim 8, characterized in that the superheating of the provided steam takes place before the hot exhaust gas stream enters the second combustion stage (6), and that the heating of the reaction space (7) for the endothermic reaction takes place with the heat coming from the gas turbine (1) exhaust gas flow, before this is used for steam production (29). 10. Method according to one of claims 1-9, characterized in that the endothermic reaction is carried out as a steam reforming of C-H compounds, particularly in the form of a conversion of soil gas or biogas (CH4) to synthesis gas (CO and H2). 11. Method according to one of claims 1-10, characterized in that the endothermic reaction is carried out at a temperature below 780°C, preferably below 700°C, in particular below 650°C. 12. Method according to one of the claims 8-11, characterized in that part of the not yet completely de-stressed steam is taken from the steam turbine (31), which is then fed to the steam reformer (7). 13. Installation for carrying out the method according to claim 1, which installation in addition to a gas turbine (1) for providing usable mechanical energy contains at least the following components: one of at least one compressor (3a, 3b) consisting of a compressor unit (3) for compressing combustion air , a compressor drive gas turbine unit (2) connected to the compressor unit (3) in drive technology, whose gas inlet side through a pipeline (10,11,12,27) is connected to the gas outlet side of the compressor unit (3), at least one arranged in front of the compressor drive gas turbine unit (2) first combustion chamber (5), where the pipeline (11) respectively (27) for combustion air and a fuel supply line (20) opens, a hot gas supply line (12,13,14,28) from the first combustion chamber (5) to the gas inlet side of the gas turbine (1) and an exhaust line (15,16) from the gas outlet side of the gas turbine (1) to a heat exchanger unit (8 and 30, respectively) for utilization of the residual heat of the exhaust gas, a reactor (7) for an endothermic chemical reaction, in h in which reactor the output fuel supplied through a fuel supply line (18) can provide a converted fuel with a higher absolute heating value, the reactor (7) with its heating part being connected to one of the pipelines carrying a hot medium (11,12,13,14, 15), and a fuel supply line (20) for the converted fuel led directly from the reactor (7) to the first combustion chamber (5), characterized in that between the compressor drive gas turbine unit (2) and the gas turbine (1) a second combustion chamber (6) in the hot gas supply line (13,14), and that the second combustion chamber (6) is likewise connected to the reactor (7) through a line (20) for converted fuel. 14. Plant according to claim 13, characterized in that the reactor (7) is designed as a steam reforming plant. 15 . Plant according to one of claims 13 or 2, characterized in that the compressor drive gas turbine unit (2) and the gas turbine (1) are arranged on a common shaft. 16. Installation according to one of the cavities 13-15, characterized in that the reactor (7) with its heating part is connected to the exhaust gas line (15) carried out from the gas turbine (1), and in that the heat exchanger unit for utilization of the waste gas residual heat, which unit is connected to the one from the reactor (7) performed exhaust gas line (16), is designed as an exhaust gas heat exchanger (8), whose heat-absorbing side is connected to the pipeline (10, 11) for the compressed combustion air from the compressor (3) and to the first combustion chamber (5). 17. Plant according to one of the claims 13-15, characterized in that the heat exchanger unit for utilizing the waste gas heat in the exhaust gas line (15,16) is designed as a steam boiler (30), that a steam line (37) runs from the steam boiler (30) to a steam superheater (29) ), whose heating part is connected to one of the hot-exhaust pipelines (13,15), and in that a steam turbine (31) is arranged, whose steam inlet side is connected to the steam superheater (29) through a steam line (38). 18. Plant according to one of the claims 13-17, characterized by a steam system, with which the steam provided in one or more steam generators (21,22,23) can be introduced into the reaction space of the steam reforming plant (7), particularly after a mixture with output fuel. 19. Plant according to one of claims 13-18, characterized in that the combustion chambers (5,6) for regulating the combustion temperature have a connection for nozzle introduction of water or steam (line 36).