Method and system for the generation of electricity and / or heat

Abstract

The invention relates to an electricity and / or heat generation method in which a gaseous fuel is burnt, the fuel used containing or consisting of DME.

Description

[0001] DESCRIPTION

[0002] METHOD AND PLANT FOR GENERATING ELECTRIC POWER AND / OR HEAT

[0003] The present invention relates to a method for generating electrical power and / or heat, in which a gaseous fuel is burned. Furthermore, the invention relates to a plant for carrying out such a method with a burner for combustion of a gaseous fuel.

[0004] The invention thus relates, for example, to the operation of gas-fired power plants that use chemical energy from the combustion of a fuel gas, such as natural gas, biogas, wood gas, etc., as primary energy. Electricity generation using gas-fired power plants is referred to as gas-fired power generation and can be achieved using various types of thermal power plants. In addition to traditional steam power plants (gas turbines) fired with natural gas, gas and steam combined cycle power plants (CCPPs) are particularly common. Fuel cell power plants are also used, which are not referred to as gas-fired power plants, although they also use a fuel gas, usually hydrogen, which can be obtained, for example, from natural gas reforming.

[0005] Pure gas-fired power plants, in particular, are often used with load-flexible features (demand-side management and redispatch) to balance electricity generation from renewable energies with electricity demand and, in particular, to compensate for fluctuations in electricity generation from renewable energies. Combined cycle power plants are more efficient than pure gas-fired power plants, but are not as load-flexible as pure gas-fired power plants. To reduce CO2 emissions in electricity generation, both the direct use of electrical energy from renewable energy sources such as photovoltaics or wind power and the use of non-fossil fuels such as hydrogen (H2) and ammonia (NH3) are being tested.

[0006] CO2 capture from flue gases and subsequent storage in rock layers (Carbon Capture and Storage CCS) is also being discussed. However, this process is very complex. Furthermore, CO2 storage carries long-term risks, is not socially acceptable in Germany, and is only being implemented with delays, as it currently takes a very long time for appropriate reservoirs to be qualified and approved. Furthermore, this technology can only reduce emissions by approximately 90%.

[0007] Since the sustainable production of hydrogen (H2) or ammonia (NH3) is highly energy-intensive and therefore difficult to implement in Central and Northern Europe, imports are necessary to supply local industrial plants. Because hydrogen is difficult to transport over long distances as a gas, it must be liquefied (LH2). Alternatively, the hydrogen can be converted through chemical reactions into liquid organic hydrogen carriers (LOHC) or into liquid or easily liquefiable hydrogen carriers such as ammonia (NH3) for transport.

[0008] There is currently no developed infrastructure for liquid hydrogen. Furthermore, liquefaction is very energy-intensive. Currently, relatively small liquefiers with a capacity of 5–30 tpd of H2 are still being built. These require up to 12 kWh / kg of hydrogen for liquefaction. Therefore, the transport of hydrogen via bulk chemicals such as ammonia (NH3) is preferred, as the transport infrastructure for these is available.

[0009] However, the direct use of ammonia as fuel gas requires a complex NO XDistance and burner design are important due to the poor fuel gas properties of ammonia. Unlike power plants, however, glass and cement plants do not have gas processing systems such as DeNox or FGD. For this reason, in many concepts, the ammonia is first decomposed into nitrogen (N2) and hydrogen (H2) or into forming gas (a stoichiometric mixture of N2 and H2 in a ratio of 1:3) by an NH3 cracker and then used in the furnace. This leads to energy losses on the one hand and high capital costs on the other.

[0010] The object of the present invention is therefore to design a method for generating electrical power and / or heat of the type mentioned above in such a way that CO2 emissions can be reduced or avoided.

[0011] Furthermore, an annex for carrying out the procedure should be specified.

[0012] This object is achieved according to the invention in a process of the type mentioned at the outset in that a fuel is used which contains more than 50 mol%, in particular more than 60 mol% DME (dimethyl ether), wherein the DME (dimethyl ether) is supplied in liquid form and evaporated before combustion in order to bring it into a gaseous state, and that the gaseous DME is combusted without further conversion into a hydrogen carrier other than DME, in particular without a reforming step following evaporation. According to a preferred embodiment, a fuel is used which contains at least 75 mol%, in particular at least 85 mol% and in particular more than 90 mol% DME, wherein, in particular, in one operating mode of the process a gaseous fuel is combusted which, apart from impurities, contains exclusively DME.

[0013] Accordingly, the plant for carrying out the method is characterized in that the burner is designed to burn a gaseous fuel which contains more than 50 mol%, in particular more than 60 mol% DME (dimethyl ether), and in that an evaporation device is provided upstream of the burner, which is designed to evaporate liquid DME and thus bring it into a gaseous state, wherein the evaporation device is connected to the burner directly, that is to say without the interposition of a device, in particular a reforming device, for converting the gaseous DME into a hydrogen carrier other than DME, in order to feed the gaseous DME directly to the burner.The burner is preferably designed to burn a gaseous fuel which contains more than 70 mol%, in particular more than 85 mol% and preferably more than 95 mol% DME, wherein the burner should be designed to burn a gaseous fuel which, apart from impurities, contains exclusively DME.

[0014] The invention is therefore based on the idea of ​​using dimethyl ether as a fuel for electricity generation and / or heat generation. Dimethyl ether can be used equally as a fuel in gas-fired power plants, combined cycle power plants, or fuel cell power plants. In a preferred embodiment of the invention of the method according to the invention, it is provided that the combustion of the gaseous fuel takes place in a burner / combustion chamber of a heat engine operating according to a non-closed cycle with supercritical CO2 as the working medium, in particular according to the Brayton, Matiant, or Allem cycle or process variants derived therefrom, or the combustion of the gaseous fuel takes place in the burner / combustion chamber of a gas-fired power plant and / or a gas and steam power plant and / or during the operation of a fuel cell.Accordingly, the system according to this embodiment is characterized in that the burner is part of a heat engine operating according to a non-closed cycle with supercritical CO2 as the working medium, in particular according to the Brayton, Matiant, or Allem cycle or process variants derived therefrom, or part of a gas power plant and / or a combined cycle power plant and / or a fuel cell plant, in particular a gas turbine. In particular, the burner / combustion chamber can be designed to combust DME with supercritical CO2 as the working medium with O2.

[0015] Dimethyl ether is a fuel that can be produced from CO2 and sustainably produced hydrogen. In other words, the combustion process releases only CO2 that was previously extracted from the environment to produce dimethyl ether. This makes the combustion process and the DME production process combined CO2-neutral.

[0016] Essential to the invention is that the DME according to the invention is combusted directly, meaning that no conversion of the gaseous DME into another hydrogen carrier takes place. This eliminates the need for investments such as the use of a reforming plant or hydrogen purification system, which are associated with the use of other hydrogen-based fuels, such as NH3 or LOHC. Since dimethyl ether is typically transported in liquid form, the invention provides for the DME (dimethyl ether) to be supplied in liquid form and vaporized before combustion. For this purpose, a corresponding vaporization device is provided upstream of the burner.

[0017] According to one embodiment of the invention, it can further be provided that carbon dioxide (CO2) is separated from the flue gas / gas mixture produced during fuel combustion. For this purpose, a corresponding CO2 separation device is provided downstream of the burner.

[0018] CO2 capture can be carried out, for example, using DME as a scrubbing agent. In this case, the flue gas / gas mixture is conveniently dried before CO2 capture. It is also possible to separate some of the water contained in the flue gas through condensation. Condensation of the water takes place at temperatures as low as possible above freezing. After scrubbing with DME, the flue gas / gas mixture can be further scrubbed with water to avoid DME losses.

[0019] Alternatively, the CO2 removal can be carried out by chemical scrubbing, in particular by amine scrubbing in one or two stages and / or by physical scrubbing, in particular based on methanol and / or by a membrane process and / or by an adsorption process.

[0020] Here, too, it is possible to at least partially liquefy the carbon dioxide (CO2) separated from the flue gas / gas mixture. For CO2 liquefaction, waste heat from DME evaporation is conveniently used. To achieve this, the carbon dioxide (CO2) is liquefied at a higher pressure than the DME is evaporated. Since DME can be evaporated at a lower pressure, the carbon dioxide (CO2) only needs to be compressed above the critical pressure before liquefaction. Overall, the process is energy-efficient.

[0021] The carbon dioxide (CO2) separated from the flue gas / gas mixture is preferably fed into a DME production process to create a closed cycle. Since the DME production process is highly energy-intensive, it will usually take place spatially separate from the power generation site. In this case, the carbon dioxide (CO2) is transported to the DME production site using transport vehicles. Tankers can be used as a transport vehicle, with tankers being preferred for transporting DME from the DME production site to the endothermic production process site. This design is based on the consideration that the physical properties of DME and CO2 are very similar, so that CO2 and DME can be transported or stored in the same transport vessel using the same tanks.The tanks can either be equipped with a membrane so that DME and CO2 do not mix, or additional stationary tanks can be installed to prevent mixing of DME and CO2.

[0022] Overall, the invention creates a closed CO2 cycle in which the CO2 released during DME combustion is captured and fed back into DME production as a carbon source. This eliminates CO2 storage, and the environment is not burdened with CO2 emissions due to the combustion itself.

[0023] According to the invention, DME is used as the fuel. At times when no DME or insufficient DME is available, the process can also be carried out using other fuels. Thus, in at least one operating mode of the process, a fuel containing primarily DME and additionally other fuels, in particular hydrogen (H2) and / or methane (CH4), can be used. In another operating mode of the process, a fuel containing pure hydrogen (H2) and / or methane (CH4) without DME can be used for a limited period of time.

[0024] In a further development of the method according to the invention, it is provided that pure oxygen (O2) is supplied to the combustion for O2 enrichment, wherein, in particular, the oxygen (O2) is generated by electrolysis from water and / or by cryogenic air separation and / or by a high-temperature membrane process and / or wherein, in particular, carbon dioxide (CO2) produced during combustion is separated from the flue gas produced during combustion by condensation. In this embodiment, the combustion air is enriched with oxygen (O2) to achieve better efficiency (oxyfuel process). The oxygen (O2) is generated by electrolysis from water and / or by cryogenic air separation and / or by a high-temperature process. As a rule, the maximum flame temperature must be observed when oxygenating the combustion air, so that the oxygen enrichment (without recycling) is limited.In this case, CO2 separation takes place as described above, but is more efficient due to the higher CO2 partial pressure. According to the invention, unconverted oxygen (O2) is separated from the flue gas produced during fuel combustion and / or during the production process, and the oxygen (O2) is returned to the combustion process. A certain proportion of carbon dioxide (CO2), which was separated from the flue gas, can also be added to the oxygen (O2) in order to adjust the flame temperature. To further increase efficiency, it is possible to use waste heat from the flue gas / gas mixture produced during combustion to preheat combustion air and / or to evaporate DME.

[0025] For further embodiments of the invention, reference is made to the claims and the following description with reference to the accompanying drawings. The drawing shows:

[0026] Figure 1 is a diagram in which the method according to the invention for generating electrical current is schematically shown,

[0027] Figure 2 is a circuit diagram showing an example of CO2 separation from flue gas produced by the process according to the invention, and

[0028] Figure 3 is a circuit diagram schematically showing the treatment of the flue gas produced in the process according to the invention when using DME-based oxyfuel.

[0029] Figure 1 schematically illustrates the method according to the invention for carrying out endothermic production processes with DME firing and CO2 capture (carbon capture CC). The method is carried out in a plant whose main components are an evaporation device 1 for evaporating liquid dimethyl ether (DME), a combustion chamber or burner 2 in which the endothermic production process is carried out and which is fired by the combustion of DME, and a CO2 capture device 3 downstream of the burner 2, in which carbon dioxide (CO2) is captured from the flue gas / gas mixture produced during the production process and combustion.

[0030] During operation, liquid DME is fed to the evaporation device 1, as indicated by arrow A in Figure 1, and the DME is converted into a gaseous state in the evaporation device 1. The energy required for this can be provided at least partially by the waste heat from the flue gas generated during combustion in the production process, as will be described below.

[0031] The gaseous fuel is fed from the evaporation device 1 to the burner 2, where it is combusted with combustion air to generate the thermal energy required for the endothermic production process. The combustion air required for combustion can optionally be enriched with oxygen (O2) (oxyfuel process) to improve combustion efficiency (see arrow B in Figure 1). As a rule, the maximum flame temperature must be observed when oxygenating the combustion air. To adjust the flame temperature, a certain amount of carbon dioxide (CO2) can be added to the oxygen (O2), which is then recycled from the CO2 separation device 3 to the production process.

[0032] The oxygen (O2) is generated from water by electrolysis and / or by cryogenic air separation and / or by a high-temperature membrane process. By enriching the combustion air with oxygen (O2), oxygen (O2) not converted during combustion can also be separated from the flue gas and recycled to enrich the combustion air for oxygen. The recirculation of carbon dioxide (CO2) and oxygen (O2) will be discussed below. According to the invention, the burner 2 is designed to burn gaseous DME.

[0033] Preferably, the burner 2 is further configured to also combust other fuels, in particular hydrogen (H2) and / or methane (CH4). In this case, it is possible to fire the furnace burner 2 with a mixture of gaseous DME, hydrogen, and / or methane. At times when no DME is available, a fuel containing pure hydrogen (H2) and / or methane (CH4) without DME can then be used for a limited period of time in an operating mode of the method according to the invention. An operating mode in which the thermal energy is generated at least partially via electrical energy is also conceivable.

[0034] The CO2 separation in the CO2 separation device 3 can be carried out by chemical scrubbing, in particular by amine scrubbing in one or two stages, and / or by physical scrubbing, in particular based on methanol, and / or by a membrane process and / or by an adsorption process.

[0035] From the CO2 separation device 3, the low-CO2 flue gas is released into the environment, if necessary after further treatment stages, as indicated by the arrow E in Figure 1, and the separated CO2 is transported back to the site of DME production, if necessary after liquefaction, to serve there as a carbon source for DME production (see arrow F in Figure 1).

[0036] Since the physical properties of DME and CO2 are very similar, CO2 and DME can be transported or stored in the same transport vessel using the same tanks. The tanks can be equipped with a membrane to prevent DME and CO2 from mixing. Alternatively, at least one additional stationary tank can be installed on the transport vessel to prevent DME and CO2 from mixing.

[0037] Figure 2 illustrates in more detail a process for separating CO2 from the flue gas in the CO2 separation device 3. The flue gas D coming from the burner 2 is first cooled in a heat exchanger 4 and then fed via a flue gas blower 5 to another heat exchanger 6, in which heat is extracted from the flue gas D and fed to the liquid DME for evaporation. The heat exchanger 6 thus also forms part of the evaporation device 1.

[0038] The flue gas, now cooled to approximately 5°C, is fed to a drying unit 7, in which condensate condensed from the flue gas is removed, see arrow G.

[0039] From the drying unit 7, the flue gas is fed to a first scrubbing column 8, see arrow H in Figure 2. In the scrubbing column 8, the actual CO2 removal from the flue gas takes place, for example, using DME as a scrubbing agent. Additionally, a cleaning process with water (H2O) is performed. For this purpose, DME is fed to one point of the scrubbing column 8, water (H2O) is fed to another point, and a mixture of DME and water is fed to another point. The scrubbing process is known per se and will therefore not be described in detail.

[0040] The purified flue gas is discharged from scrubbing column 8 at point E1, and water and a mixture of DME and CO2 are discharged from scrubbing column 8 at point I. This stream is first compressed or conveyed in a pump 9 and fed into a separation column 10. On its way from pump 9 to separation column 10, the stream passes through a heat exchanger 11, where it is cooled. The heat is used to heat a mixture of DME and water, which is fed to the first scrubbing column 8.

[0041] In the separation column 10, CO2 is obtained at the top and a mixture of DME and H2O is obtained in the bottom.

[0042] The mixture of DME and H2O is fed from the separation column 10 via a line 12 to a heat exchanger 13, where it is cooled, and then to another separation column 14, where the DME is purified from the water. The DME / H2O mixture is discharged via a line 15. A portion of the mixture is evaporated in a reboiler 16 and fed back into the separation column 14 via a separation device 18. The DME is recycled to the first scrubbing column 8, and the water is released to the environment. A portion of the water is recycled via line 19 to the first scrubbing column 8 to prevent DME emissions in the flue gas stream E1. Inert gases can be released to the environment via the top (see arrow E3).

[0043] A mixture of DME and H2O is partially taken from the first wash column 8 (see arrow K) and fed directly into the separation column 10 or into the separation column 14.

[0044] Figure 3 shows the treatment of flue gas when the DM E fuel is enriched with oxygen during combustion, i.e., when an oxyfuel is burned. In this case, the flue gas D coming from burner 2 is rich in carbon dioxide (CO2), water (H2O), and oxygen (O2). The flue gas stream is cooled in a heat exchanger 20 and fed to a first drying unit 21. In this drying unit 21, liquid condensate is separated from the flue gas and removed (see arrow M). The thus pre-dried flue gas is fed via a line 22 to a compressor 23 and compressed there, then cooled in a heat exchanger 24 and fed to a second drying unit 25, in which liquid condensate is again separated from the flue gas (see arrow N).

[0045] The remaining flue gas is partially recycled via line 26 to be mixed with the oxygen used to enrich the combustion air.

[0046] The remaining flue gas (line 27) is further compressed in a compressor 28, cooled in a heat exchanger 29, and then fed to a third drying unit 30, where liquid condensate is separated from the flue gas (see arrow O). The flue gas exiting the third drying unit 30 is fed to a fourth drying unit 32 via a line 31, where water is separated from the flue gas (see arrow P). The flue gas exiting the fourth drying unit 30 is only practically water-free and is cooled once again in a heat exchanger 33. In a CO2 liquefaction unit 34, CO2 is condensed at approximately -50°C, and the CO2 condensate is removed for further use (see arrow Q).

[0047] The flue gas stream leaving the fifth drying unit 34 is rich in oxygen (O2). It is partially recycled to the furnace burner 2 for O2 enrichment (line 35) and the remainder is purified to remove inert components before being released into the environment (arrow E4).

[0048] 1 evaporation device

[0049] 2 burners

[0050] 3 CO2 separation device

[0051] 4 heat exchangers

[0052] 5 flue gas blowers

[0053] 6 heat exchangers

[0054] 7 Drying unit

[0055] 8 first wash column

[0056] 9 Pump

[0057] 10 Separation column

[0058] 11 heat exchangers

[0059] 12 Line

[0060] 13 heat exchangers

[0061] 14 Separation column

[0062] 15 Line

[0063] 16 reboilers

[0064] 17 heat exchangers

[0065] 18 Separator

[0066] 19 Management

[0067] 20 heat exchangers

[0068] 21 first drying unit

[0069] 22 Line

[0070] 23 compressors

[0071] 24 heat exchangers

[0072] 25 second drying unit

[0073] 26 Line

[0074] 27 Line

[0075] 28 Compressor 29 Heat exchanger

[0076] 30 third drying unit

[0077] 31 Line

[0078] 32 fourth drying unit 33 heat exchanger

[0079] 34 CO2 liquefaction

[0080] 35 Line

Claims

CLAIMS 1. A process for generating electrical power and / or heat, in which a gaseous fuel is burned, characterized in that a fuel is used which contains more than 50 mol%, in particular more than 60 mol% DME (dimethyl ether), wherein the DME (dimethyl ether) is supplied in liquid form and is evaporated before combustion in order to bring it into a gaseous state, and that the gaseous DME is burned without further conversion into a hydrogen carrier other than DME, in particular without a reforming step following the evaporation.

2. Process according to claim 1, characterized in that a fuel is used which contains at least 75 mol%, in particular at least 85 mol% and in particular more than 90 mol% DME, wherein, in particular, at least in one operating mode of the process a gaseous fuel is burned which, apart from impurities, contains exclusively DME.

3. The method according to claim 1 or 2, characterized in that at least in one operating mode of the method, a fuel is used which mainly comprises DME and additionally other fuels, in particular hydrogen (H2) and / or methane (CH4).

4. The method according to claim 2 or 3, characterized in that in one operating mode of the method, a fuel containing pure hydrogen (H2) and / or methane (CH4) without DME is used for a limited period of time.

5. Method according to one of the preceding claims, characterized in that pure oxygen is supplied to the gaseous fuel for O2 enrichment, wherein, in particular, the oxygen (O2) is produced by means of electrolysis from water and / or by cryogenic air separation and / or by a high-temperature membrane process and / or wherein, in particular, carbon dioxide (CO2) produced during combustion is separated from the flue gas by means of condensation.

6. Process according to one of the preceding claims, characterized in that carbon dioxide (CO2) is separated from the flue gas / gas mixture produced during the combustion of the fuel.

7. A process according to claim 5 or 6, characterized in that the carbon dioxide (CO2) separated from the flue gas is at least partially liquefied.

8. Process according to claim 7, characterized in that waste heat from the CO2 liquefaction is used for DM E evaporation.

9. Process according to one of claims 5 to 8, characterized in that the CO2 separation is carried out using DME as a scrubbing agent, wherein in particular the flue gas is dried before the CO2 separation and / or a part of the water contained in the flue gas is separated by condensation.

10. Process according to claim 9, characterized in that the flue gas is additionally washed with water after washing with DME.

11. Process according to one of claims 5 to 10, characterized in that the CO2 separation is carried out by chemical washing, in particular by amine washing in one or two stages, and / or by physical washing, in particular based on methanol, and / or by a membrane process and / or in an adsorption process.

12. A process according to any one of claims 5 to 11, characterized in that carbon dioxide (CO2) separated from the flue gas is fed to a process for producing DME.

13. Process according to claim 12, characterized in that the DME produced is returned to the process.

14. The method according to claim 12 or 13, characterized in that the process for producing DME takes place spatially separated from the location of electrical power generation and the carbon dioxide (CO2) is transported to the location of DME production by means of transport.

15. A method according to claim 14, characterized in that tankers are used as the means of transport, in particular the same tankers are used as those used to transport DME.

16. Method according to one of the preceding claims, characterized in that oxygen (O2) is separated from the flue gas / gas mixture produced during the combustion of the fuel and the oxygen is returned to the combustion, wherein, in particular, carbon dioxide (CO2) which has also been separated from the flue gas / gas mixture is added to the oxygen.

17. A process according to any one of the preceding claims, characterized in that waste heat from the flue gas produced during combustion is used to preheat air and / or evaporate DME.

18. Method according to one of the preceding claims, characterized in that the combustion of the gaseous fuel takes place in a burner (2) / combustion chamber of a heat engine operating according to a non-closed cycle with supercritical CO2 as the working medium, in particular according to the Brayton, Matiant or Allem cycle or process variants derived therefrom, or the combustion of the gaseous fuel takes place in the burner / combustion chamber of a gas power plant and / or a gas and steam power plant and / or as part of the operation of a fuel cell.

19. Plant for carrying out the method according to one of the preceding claims, with a burner (2) for burning a gaseous fuel, characterized in that the burner (2) is designed to burn a gaseous fuel which contains more than 50 mol%, in particular more than 60 mol% DME (dimethyl ether), and in that an evaporation device (1) is provided upstream of the burner (2), which is designed to evaporate liquid DME and thus bring it into a gaseous state, wherein the evaporation device (1) is connected to the burner (2) directly, that is to say without the interposition of a device, in particular a reforming device, for converting the gaseous DME into a hydrogen carrier other than DME, in order to feed the gaseous DME directly to the burner (2).

20. Plant according to claim 19, characterized in that the burner (2) is designed to burn a gaseous fuel which contains more than 70 mol%, in particular more than 85 mol% and preferably more than 95 mol% DME, and / or that the burner (2) is designed to burn other fuels, in particular hydrogen and / or methane, in addition to DME.

21. Plant according to claim 19 or 20, characterized in that a CO2 separation device (3) is provided downstream of the burner (2) in order to separate carbon dioxide (CO2) from the flue gas / gas mixture produced during combustion.

22. Plant according to one of claims 19 to 21, characterized in that the outlet of the CO2 separation device (3) is connected to an inlet of the burner (2) in order to return carbon dioxide (CO2) to the burner (2).

23. Plant according to one of claims 19 to 22, characterized in that an O2 separation device (3) is provided downstream of the burner (2) in order to separate oxygen (O2) from the flue gas / gas mixture produced during combustion.

24. Plant according to one of claims 19 to 23, characterized in that the burner (2) is part of a heat engine operating according to a non-closed cycle with supercritical CO2 as the working medium, in particular according to the Brayton, Matiant or Allem cycle or process variants derived therefrom, or part of a gas power plant and / or a gas and steam power plant and / or a fuel cell plant, in particular a gas turbine.

25. Plant according to one of claims 19 to 24, characterized in that the burner (2) is designed to burn DME with supercritical CO2 as working medium with O2.

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