A circular power generation system and method coupling SOFC and working fluid recovery.

Abstract

This invention relates to the field of solid oxide fuel cell technology, and particularly to a cyclic power generation system and method coupling SOFC and working fluid recovery. The system includes: a solid oxide fuel cell, comprising a cathode and an anode; an anode gas supply unit for supplying fuel gas to the anode; a cathode gas supply unit for supplying air to the cathode; a waste heat recovery unit, comprising a first separator, a combustion chamber, a first mixer, a turbine, and a generator; the inlet of the first separator is connected to the outlet of the anode; the two outlets of the first separator are respectively connected to the anode gas supply unit and the inlet of the combustion chamber; the outlet of the combustion chamber is connected to the first inlet of the first mixer; the second inlet of the first mixer is connected to the working fluid recovery unit; the outlet of the first mixer is connected to the inlet of the turbine; and the turbine is connected to the generator; the working fluid recovery unit is connected to both the outlet and inlet of the turbine, for recovering exhaust gas from the turbine outlet and returning the recovered exhaust gas to the turbine inlet.

Description

Technical Field

[0001] This invention relates to the field of solid oxide fuel cell technology, and more particularly to a cyclic power generation system and method that couples SOFC and working fluid recycling. Background Technology

[0002] A fuel cell is a power generation device that directly converts chemical energy into electrical energy through an electrochemical reaction. Among them, solid oxide fuel cells (SOFCs) operate at temperatures of 600–1000℃, have high waste heat utilization value, and can be used for combined heat and power (CHP), improving energy utilization efficiency to over 90%. Summary of the Invention

[0003] This invention provides a circular power generation system and method that couples SOFC and working fluid recycling, which can effectively utilize the waste heat of high-temperature exhaust gas from solid oxide fuel cells.

[0004] In a first aspect, embodiments of the present invention provide a cyclic power generation system coupling SOFC and working fluid recycling, comprising:

[0005] Solid oxide fuel cells, including a cathode and an anode, are used for connection to an external inverter;

[0006] An anode gas supply unit, connected to the anode, is used to supply fuel gas to the anode;

[0007] A cathode gas supply unit, connected to the cathode, is used to supply air to the cathode;

[0008] The waste heat utilization unit includes a first separator, a combustion chamber, a first mixer, a turbine, and a generator. The outlet of the cathode is connected to the inlet of the combustion chamber. The inlet of the first separator is connected to the outlet of the anode. The two outlets of the first separator are respectively connected to the anode gas supply unit and the inlet of the combustion chamber. The outlet of the combustion chamber is connected to the first inlet of the first mixer. The second inlet of the first mixer is connected to the working fluid recovery unit. The outlet of the first mixer is connected to the inlet of the turbine. The turbine is connected to the generator.

[0009] The working fluid recovery unit is connected to the outlet and inlet of the turbine, respectively, and is used to recover the exhaust gas from the turbine outlet and return a portion of the recovered exhaust gas to the turbine inlet.

[0010] Secondly, embodiments of the present invention provide a circular power generation method coupling SOFC and working fluid recycling, applied to the circular power generation system described in any of the above embodiments, comprising:

[0011] The solid oxide fuel cell is used to generate electrical energy;

[0012] Fuel gas is supplied to the anode using the anode gas supply unit;

[0013] Air is supplied to the cathode using the cathode gas supply unit;

[0014] The waste heat recovery unit absorbs the exhaust heat from the solid oxide fuel cell.

[0015] The working fluid recovery unit recovers the exhaust gas from the turbine outlet and returns a portion of the recovered exhaust gas to the turbine inlet.

[0016] As can be seen from the above solutions, the coupled SOFC and working fluid recovery and utilization cycle power generation system and method provided by the present invention can effectively utilize the exhaust heat of the solid oxide fuel cell to generate electricity by setting up a waste heat utilization unit; by connecting one outlet of the first separator to the anode gas supply unit, the fuel utilization rate of the solid oxide fuel cell can be improved; by setting up a working fluid recovery unit to recover the exhaust gas from the turbine outlet and return a portion of the recovered exhaust gas to the turbine inlet, the working fluid flow rate at the turbine inlet can be increased, thereby increasing the turbine's expansion work and improving the power generation efficiency of the cycle power generation system. Therefore, the above technical solution can effectively utilize the waste heat of the high-temperature exhaust gas from the solid oxide fuel cell. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of a circulating power generation system that couples SOFC and recycles working fluid, provided for an embodiment of the present invention.

[0019] Figure label:

[0020] 10-Inverter;

[0021] 1-Solid oxide fuel cell;

[0022] 2- Anode gas supply unit;

[0023] 21-First water pump;

[0024] 22-First heat exchanger;

[0025] 23-First compressor;

[0026] 24 - Second mixer;

[0027] 25 - Second heat exchanger;

[0028] 26-Pre-reformer;

[0029] 27-Third heat exchanger;

[0030] 28 - Second compressor;

[0031] 3-Cathode gas supply unit;

[0032] 31-Third compressor;

[0033] 32 - Fourth heat exchanger;

[0034] 4- Waste heat utilization unit;

[0035] 41 - First separator;

[0036] 42 - Combustion chamber;

[0037] 43 - First mixer;

[0038] 44-Turbine;

[0039] 45 - Generator;

[0040] 5-Working fluid recovery unit;

[0041] 51-Heat exchange assembly;

[0042] 511 - Fifth heat exchanger;

[0043] 512 - Sixth heat exchanger;

[0044] 513 - Seventh heat exchanger;

[0045] 52 - Condenser;

[0046] 53-Second water pump;

[0047] 54 - Second separator;

[0048] 55 - Water storage tank;

[0049] 56 - Gas-liquid separator;

[0050] 57 - Fourth compressor. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Please see Figure 1 One embodiment of the present invention provides a circular power generation system coupling SOFC and working fluid recycling, the system comprising:

[0053] A solid oxide fuel cell 1 includes a cathode and an anode for connection to an external inverter 10;

[0054] Anode gas supply unit 2, connected to the anode, is used to supply fuel gas to the anode;

[0055] Cathode gas supply unit 3, connected to the cathode, is used to supply air to the cathode;

[0056] Waste heat utilization unit 4 includes a first separator 41, a combustion chamber 42, a first mixer 43, a turbine 44, and a generator 45. The outlet of the cathode is connected to the inlet of the combustion chamber 42, the inlet of the first separator 41 is connected to the outlet of the anode, the two outlets of the first separator 41 are respectively connected to the anode gas supply unit 2 and the inlet of the combustion chamber 42, the outlet of the combustion chamber 42 is connected to the first inlet of the first mixer 43, the second inlet of the first mixer 43 is connected to the working fluid recovery unit 5, the outlet of the first mixer 43 is connected to the inlet of the turbine 44, and the turbine 44 is connected to the generator 45.

[0057] The working fluid recovery unit 5 is connected to the outlet and inlet of the turbine 44 respectively, and is used to recover the exhaust gas at the outlet of the turbine 44 and return a portion of the recovered exhaust gas to the inlet of the turbine 44.

[0058] In this embodiment, by setting up a waste heat utilization unit 4, the exhaust heat of the solid oxide fuel cell 1 can be effectively utilized to generate electricity; by connecting one outlet of the first separator 41 to the anode gas supply unit 2, the fuel utilization rate of the solid oxide fuel cell 1 can be improved; by setting up a working fluid recovery unit 5 to recover the exhaust gas from the turbine 44 outlet and return a portion of the recovered exhaust gas to the turbine 44 inlet, the working fluid flow rate at the turbine 44 inlet can be increased, thereby increasing the expansion work of the turbine 44 and improving the power generation efficiency of the cycle power generation system. Therefore, the above technical solution can effectively utilize the waste heat of the high-temperature exhaust gas from the solid oxide fuel cell.

[0059] Anode gas supply unit 2 compresses and heats the fuel and feedwater introduced into the system, mixes them with the recirculated anode exhaust gas, and pre-reforms the mixture. The pre-reformed fuel gas is then fed into the anode of the solid oxide fuel cell 1. Cathode gas supply unit 3 pressurizes and heats the air introduced into the system and feeds it into the cathode of the solid oxide fuel cell 1. The solid oxide fuel cell 1 utilizes the electrochemical reaction between the introduced fuel gas and air to convert chemical energy into electrical energy, which is then output. A portion of the exhaust gas from the anode of the solid oxide fuel cell 1 is sent into the combustion chamber 42 for further combustion, while the remaining exhaust gas is fed into anode gas supply unit 2.

[0060] It should be noted that recirculating part of the exhaust gas from the anode (i.e., feeding it into the anode gas supply unit 2) can also adjust the water-to-carbon molar flow ratio at the SOFC inlet (water refers to the water vapor content in the hydrocarbon fuel gas, and carbon refers to the carbon content in the hydrocarbon fuel). In some embodiments, the water-to-carbon molar flow ratio at the SOFC inlet can be in the range of 2 to 3, which can effectively avoid the occurrence of carbon deposition problems in the SOFC.

[0061] In the solid oxide fuel cell 1, oxygen in the cathode gains electrons and is converted into oxygen ions, which are then transported to the anode by the electrolyte. Thereafter, they react with the fuel in the anode to form H2O and CO2. The current is generated by the movement of electrons in the external circuit of the battery, and then the inverter 10 converts the direct current into alternating current to generate electricity.

[0062] In one embodiment of the present invention, the anode gas supply unit 2 includes a first water pump 21, a first heat exchanger 22, a first compressor 23, a second mixer 24, a second heat exchanger 25, a pre-reformer 26, a third heat exchanger 27, and a second compressor 28. The first water pump 21, the first heat exchanger 22, the first inlet of the second mixer 24, the second heat exchanger 25, the pre-reformer 26, the third heat exchanger 27, and the anode are connected in sequence. The first compressor 23 is connected to the second inlet of the second mixer 24, and the outlet of the second compressor 28 is connected to the third inlet of the second mixer 24. An outlet of the first separator 41, the third heat exchanger 27, and the inlet of the second compressor 28 are connected in sequence.

[0063] The outlet of turbine 44, the first heat exchanger 22, the second heat exchanger 25, the working fluid recovery unit 5, and the inlet of turbine 44 are connected in sequence.

[0064] In this embodiment, by sequentially connecting the outlet of turbine 44, the first heat exchanger 22, the second heat exchanger 25, the working fluid recovery unit 5, and the inlet of turbine 44, the exhaust heat of turbine 44 can be effectively utilized, such as for heating the feed water of the anode gas supply unit 2 (to form steam, so the exhaust heat is used to heat the feed water first) and the fuel gas.

[0065] In one embodiment of the present invention, the cathode gas supply unit 3 includes a third compressor 31 and a fourth heat exchanger 32, wherein the outlet of the third compressor 31, the fourth heat exchanger 32 and the cathode are connected in sequence.

[0066] The outlet of turbine 44, the fourth heat exchanger 32, the first heat exchanger 22, the second heat exchanger 25, the working fluid recovery unit 5, and the inlet of turbine 44 are connected in sequence.

[0067] In this embodiment, by sequentially connecting the outlet of turbine 44, the fourth heat exchanger 32, the first heat exchanger 22, the second heat exchanger 25, the working fluid recovery unit 5, and the inlet of turbine 44, the exhaust heat of turbine 44 can be further effectively utilized, such as for heating the gas supplied by cathode gas supply unit 3 before supplying anode gas supply unit 2, in order to improve the activity of oxygen.

[0068] In one embodiment of the present invention, the working fluid recovery unit 5 includes a heat exchange assembly 51, a condenser 52 and a gas-liquid separator 56 connected in sequence. The heat exchange assembly 51 is connected to the second heat exchanger 25, and the water outlet of the gas-liquid separator 56 is connected to the second inlet of the first mixer 43 through a pipeline via the heat exchange assembly 51.

[0069] In this embodiment, the water vapor in the exhaust gas of the turbine 44 can be condensed and separated into condensate by the condenser 52 and the gas-liquid separator 56 to obtain condensate. By setting the heat exchange component 51, the residual heat after the turbine 44 heats the anode gas supply unit 2 can be used to heat the water discharged from the gas-liquid separator 56 to form superheated steam. This steam is then connected to the second inlet of the first mixer 43 through a pipeline to increase the inlet working fluid flow of the turbine 44, thereby increasing the expansion work of the turbine 44 and improving the power generation efficiency of the circulating power generation system.

[0070] In one embodiment of the present invention, the working fluid recovery unit 5 further includes a second water pump 53, a second separator 54 and a water storage tank 55 connected in sequence. The inlet of the second water pump 53 is connected to the water outlet of the gas-liquid separator 56. One outlet of the second separator 54 is connected to the second inlet of the first mixer 43 via a pipeline through a heat exchange assembly 51. The other outlet of the second separator 54 is connected to the inlet of the first water pump 21.

[0071] In this embodiment, by setting a second water pump 53, the condensed water can be pressurized; by setting a second separator 54, part of the condensed water can be stored in a water storage tank 55, and another part of the condensed water can be converted into superheated steam through a heat exchange component 51.

[0072] In one embodiment of the present invention, the heat exchange assembly 51 includes a fifth heat exchanger 511, a sixth heat exchanger 512 and a seventh heat exchanger 513 connected in sequence. The fifth heat exchanger 511 is connected to the second heat exchanger 25, the seventh heat exchanger 513 is connected to the condenser 52, and one outlet of the second separator 54 is connected to the second inlet of the first mixer 43 via a pipeline passing through the seventh heat exchanger 513, the sixth heat exchanger 512 and the fifth heat exchanger 511 in sequence.

[0073] The seventh heat exchanger 513 is used to preheat the condensate discharged from the second separator 54 to the saturation temperature. The sixth heat exchanger 512 is used to heat the water discharged from the seventh heat exchanger 513 to form saturated steam. The fifth heat exchanger 511 is used to further heat the saturated steam discharged from the sixth heat exchanger 512 to form superheated steam.

[0074] In this embodiment, after passing through the second separator 54, a portion of the condensate enters the seventh heat exchanger 513, where it is preheated to near saturation temperature. The hot water from the outlet of the seventh heat exchanger 513 enters the sixth heat exchanger 512, where it is converted into saturated steam. The saturated steam from the outlet of the sixth heat exchanger 512 then enters the fifth heat exchanger 511 for further heating to obtain superheated steam at 110°C. The steam generation process is divided into preheating, evaporation, and superheating, which fully utilizes the exhaust waste heat of the turbine 44, thereby reducing the working fluid temperature at the inlet of the condenser 52 and decreasing the cooling water consumption during the condensation process.

[0075] It should be noted that if the heat exchange component 51 is only a single heat exchanger, compared with the heat exchanger combination of "the fifth heat exchanger 511, the sixth heat exchanger 512 and the seventh heat exchanger 513" mentioned above, the former does not have obvious preheating, evaporation and superheating processes, so the former cannot make full use of the exhaust waste heat of the turbine 44.

[0076] In one embodiment of the present invention, the working fluid recovery unit 5 further includes a fourth compressor 57, the gas outlet of the gas-liquid separator 56 is connected to the inlet of the fourth compressor 57, and the outlet of the fourth compressor 57 is connected to the third inlet of the first mixer 43.

[0077] In this embodiment, the working fluid condensed by the condenser 52 is separated by the gas-liquid separator 56, and the water outlet is connected to the inlet of the second water pump 53 to achieve the inlet pressure condition of the first mixer 43. Part of the condensate is converted into superheated steam by the heat exchange component 51, while the other part can be returned to the inlet of the first water pump 21 for recycling or stored in the water storage tank 55. The mixture of carbon dioxide and nitrogen in the gas outlet is pressurized by the fourth compressor 57 and output to the third inlet of the first mixer 43. The fourth compressor 57 increases the expansion ratio required for turbine 44 to expand, allowing turbine 44 to expand and perform work at atmospheric pressure. Furthermore, since the gas-liquid separator 56 removes all water, the inlet working fluid flow rate of the fourth compressor 57 is reduced, thereby reducing the compression power consumption of the fourth compressor 57 and contributing to improved power generation performance of the circulating power generation system.

[0078] It should be noted that when the superheated steam generated by the working fluid recovery unit 5 and the mixture of carbon dioxide and nitrogen are output to the inlet of the turbine 44, part of the mixture needs to be output, not all of it. Otherwise, the exhaust waste heat generated by the turbine 44 will not be able to meet the heat exchange requirements of the system.

[0079] In one embodiment of the present invention, the fuel gas includes at least one of the following: natural gas, liquefied petroleum gas, syngas, carbon monoxide, coal gas, biomass gas, and methanol.

[0080] In summary, the circulating power generation system provided by the embodiments of the present invention effectively reduces the pollution of the environment caused by the exhaust gas emissions of the power generation system, achieves the effect of energy conservation and emission reduction, and improves the power generation efficiency of the battery. Moreover, the recycling of anode exhaust gas and the full utilization of the combustion chamber improve the fuel utilization rate of the integrated system, adapt to the development trend of solid oxide fuel cell power generation systems, and have broad application prospects.

[0081] Furthermore, one embodiment of the present invention also provides a circular power generation method coupling SOFC and working fluid recycling, based on the circular power generation system mentioned in any of the above embodiments, comprising:

[0082] Electricity is generated using a solid oxide fuel cell 1;

[0083] Fuel gas is supplied to the anode using anode gas supply unit 2;

[0084] Air is supplied to the cathode using cathode gas supply unit 3;

[0085] Waste heat recovery unit 4 is used to absorb the exhaust heat from solid oxide fuel cell 1;

[0086] The working fluid recovery unit 5 is used to recover the exhaust gas from the turbine 44 outlet and return a portion of the recovered exhaust gas to the turbine 44 inlet.

[0087] It should be noted that the method embodiments provided by the present invention and the system embodiments described above belong to the same inventive concept and have the same beneficial effects. The effects of the method embodiments will not be elaborated here.

[0088] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0089] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A circular power generation system coupling SOFC and working fluid recovery, characterized in that, include: A solid oxide fuel cell (1) includes a cathode and an anode for connection to an external inverter (10); An anode gas supply unit (2) is connected to the anode and is used to supply fuel gas to the anode; A cathode gas supply unit (3) is connected to the cathode and is used to supply air to the cathode; The waste heat utilization unit (4) includes a first separator (41), a combustion chamber (42), a first mixer (43), a turbine (44), and a generator (45). The outlet of the cathode is connected to the inlet of the combustion chamber (42), the inlet of the first separator (41) is connected to the outlet of the anode, the two outlets of the first separator (41) are respectively connected to the anode gas supply unit (2) and the inlet of the combustion chamber (42), the outlet of the combustion chamber (42) is connected to the first inlet of the first mixer (43), the second inlet of the first mixer (43) is connected to the working fluid recovery unit (5), the outlet of the first mixer (43) is connected to the inlet of the turbine (44), and the turbine (44) is connected to the generator (45). The working fluid recovery unit (5) is connected to the outlet and inlet of the turbine (44) respectively, and is used to recover the exhaust gas from the outlet of the turbine (44) and return a portion of the recovered exhaust gas to the inlet of the turbine (44); The anode gas supply unit (2) includes a first water pump (21), a first heat exchanger (22), a first compressor (23), a second mixer (24), a second heat exchanger (25), a pre-reformer (26), a third heat exchanger (27), and a second compressor (28). The first water pump (21), the first heat exchanger (22), the first inlet of the second mixer (24), the second heat exchanger (25), the pre-reformer (26), the third heat exchanger (27), and the anode are connected in sequence. The first compressor (23) is connected to the second inlet of the second mixer (24), and the outlet of the second compressor (28) is connected to the third inlet of the second mixer (24). The outlet of the first separator (41), the third heat exchanger (27), and the inlet of the second compressor (28) are connected in sequence. The outlet of the turbine (44), the first heat exchanger (22), the second heat exchanger (25), the working fluid recovery unit (5) and the inlet of the turbine (44) are connected in sequence; The working fluid recovery unit (5) includes a heat exchange assembly (51), a condenser (52) and a gas-liquid separator (56) connected in sequence. The heat exchange assembly (51) is connected to the second heat exchanger (25). The water outlet of the gas-liquid separator (56) is connected to the second inlet of the first mixer (43) through the heat exchange assembly (51) via a pipeline. The working fluid recovery unit (5) further includes a second water pump (53), a second separator (54) and a water storage tank (55) connected in sequence. The inlet of the second water pump (53) is connected to the water outlet of the gas-liquid separator (56). One outlet of the second separator (54) is connected to the second inlet of the first mixer (43) through the heat exchange component (51) via a pipeline. The other outlet of the second separator (54) is connected to the inlet of the first water pump (21).

2. The circulating power generation system according to claim 1, characterized in that, The cathode gas supply unit (3) includes a third compressor (31) and a fourth heat exchanger (32), with the outlet of the third compressor (31), the fourth heat exchanger (32) and the cathode connected in sequence. The outlet of the turbine (44), the fourth heat exchanger (32), the first heat exchanger (22), the second heat exchanger (25), the working fluid recovery unit (5), and the inlet of the turbine (44) are connected in sequence.

3. The circulating power generation system according to claim 2, characterized in that, The heat exchange assembly (51) includes a fifth heat exchanger (511), a sixth heat exchanger (512), and a seventh heat exchanger (513) connected in sequence. The fifth heat exchanger (511) is connected to the second heat exchanger (25), and the seventh heat exchanger (513) is connected to the condenser (52). One outlet of the second separator (54) is connected to the second inlet of the first mixer (43) via a pipeline through the seventh heat exchanger (513), the sixth heat exchanger (512), and the fifth heat exchanger (511). The seventh heat exchanger (513) is used to preheat the condensate discharged from the second separator (54) to the saturation temperature. The sixth heat exchanger (512) is used to heat the water discharged from the seventh heat exchanger (513) to form saturated steam. The fifth heat exchanger (511) is used to further heat the saturated steam discharged from the sixth heat exchanger (512) to form superheated steam.

4. The circulating power generation system according to claim 2, characterized in that, The working fluid recovery unit (5) further includes a fourth compressor (57), the gas outlet of the gas-liquid separator (56) is connected to the inlet of the fourth compressor (57), and the outlet of the fourth compressor (57) is connected to the third inlet of the first mixer (43).

5. The circulating power generation system according to any one of claims 1-4, characterized in that, The fuel gas includes at least one of the following: natural gas, liquefied petroleum gas, syngas, carbon monoxide, coal gas, biomass gas, and methanol.

6. A cyclic power generation method coupling SOFC and working fluid recovery, characterized in that, The cyclic power generation system based on any one of claims 1-5 includes: Electricity is generated using the solid oxide fuel cell (1); Fuel gas is supplied to the anode using the anode gas supply unit (2); Air is supplied to the cathode using the cathode gas supply unit (3); The waste heat utilization unit (4) absorbs the exhaust heat of the solid oxide fuel cell (1); The working fluid recovery unit (5) is used to recover the exhaust gas from the turbine (44) outlet and return a portion of the recovered exhaust gas to the turbine (44) inlet.

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