Fuel cell and gas turbine hybrid power generation system

Abstract

The invention discloses a fuel cell and gas turbine hybrid power generation system, and relates to the technical field of hybrid power generation, and the system comprises a fuel cell unit used for generating electric energy through an electrochemical oxidation reaction; and the waste heat recovery unit is connected with the waste gas discharge port of the fuel cell unit and is used for treating the discharged waste gas of the fuel cell unit and recovering heat energy. The working efficiency of the fuel cell is improved, the temperature gradient of the fuel cell is reduced and'carbon deposition 'is prevented by designing anode and cathode dual circulation, and waste heat at different temperatures generated by the fuel cell and a gas turbine system is recycled by combining Brayton power cycle power generation, so that gradient utilization of energy is realized. Meanwhile, high-concentration CO2 is separated and recycled, greenhouse gas emission is reduced, and the device has the advantages of being high in use operability, flexible in operation mode, remarkable in energy-saving and carbon-reducing effect and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of hybrid power generation, and in particular to a hybrid power generation system of a fuel cell and a gas turbine. Background Art

[0002] Syngas fuel cell power generation technology is a new low-carbon power generation model with great development potential. It has the advantages of high power generation efficiency, low pollution, easy capture of CO2 and strong flexibility. In previous research on solid oxide fuel cells, the fuel gas mainly includes natural gas, biogas and hydrogen.

[0003] Traditional fuel cell exhaust gas is directly discharged into the gas turbine. This process fails to fully utilize the waste heat in the exhaust gas, resulting in low energy utilization efficiency.

[0004] Therefore, there is an urgent need to propose a fuel cell and gas turbine hybrid power generation system. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above problems existing in the existing fuel cell and gas turbine hybrid power generation system, the present invention is proposed.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a fuel cell and gas turbine hybrid power generation system, comprising:

[0008] A fuel cell unit for generating electrical energy through an electrochemical oxidation reaction; and

[0009] A waste heat recovery unit is connected to the exhaust gas discharge port of the fuel cell unit and is used to process the exhaust gas discharged by the fuel cell unit and recover heat energy.

[0010] As a preferred embodiment of the fuel cell and gas turbine hybrid power generation system of the present invention, the waste heat recovery unit includes a first heat exchanger connected to the exhaust gas outlet of the fuel cell unit, and a SCO2 Brayton cycle module and a flue gas treatment module connected to the first heat exchanger.

[0011] As a preferred embodiment of the fuel cell and gas turbine hybrid power generation system of the present invention, the SCO2 Brayton cycle module includes a recompressor, a compression condensing unit, a low-temperature regenerator, a high-temperature regenerator, a CO2 turbine, a CO2 turbine, a second heat exchanger, and connecting pipes;

[0012] The input ends of the recompressor and the compression condensing unit are both connected to the output end of the low-temperature regenerator;

[0013] The output end of the compression condensing unit is connected to the first heat exchanger, and the output end of the recompressor is connected to the input end of the high-temperature regenerator;

[0014] The output end of the high temperature regenerator is connected to the input end of the CO2 turbine, and the output end of the CO2 turbine is connected to the input end of the low temperature regenerator;

[0015] The high temperature regenerator, the second heat exchanger and the CO2 turbine circulate the gas through the pipeline;

[0016] The output end of the first heat exchanger is connected to the input end of the high-temperature heat regenerator.

[0017] As a preferred embodiment of the fuel cell and gas turbine hybrid power generation system of the present invention, the SCO2 Brayton cycle module also includes a first pipeline connecting the compression condensing unit and the low-temperature regenerator, and the gas can flow back from the compression condensing unit to the low-temperature regenerator through the first pipeline.

[0018] As a preferred embodiment of the fuel cell and gas turbine hybrid power generation system of the present invention, wherein: the SCO2 Brayton cycle module further includes a second pipeline connecting the low-temperature regenerator and the high-temperature regenerator, and another second pipeline connecting the low-temperature regenerator and the high-temperature regenerator;

[0019] The gas enters the high temperature regenerator from the low temperature regenerator through the second pipeline;

[0020] The gas enters the low-temperature regenerator from the high-temperature regenerator through the third pipeline.

[0021] As a preferred solution of the fuel cell and gas turbine hybrid power generation system of the present invention, the SCO2 Brayton cycle module further includes a fourth pipeline connecting the second heat exchanger and the first heat exchanger, which is used for the synthesis gas to participate in heat exchange.

[0022] As a preferred embodiment of the fuel cell and gas turbine hybrid power generation system of the present invention, the compression condensing unit includes three first condensers and three first compressors, the first compressors and the first condensers are spaced apart in sequence, the first condenser at the head end is connected to the output end of the low-temperature heat regenerator, and the output end of the first compressor at the tail end is divided into two pipelines, one of which is connected to the first heat exchanger, and the other is connected to the low-temperature heat regenerator.

[0023] As a preferred embodiment of the fuel cell and gas turbine hybrid power generation system of the present invention, the fuel cell unit comprises:

[0024] A fuel cell body including a cathode and an anode;

[0025] a post-combustion chamber in which the remaining fuel that has not been completely consumed by the fuel cell body is mixed with pure oxygen and combusted;

[0026] The first gas turbine performs work on the expansion of the high temperature gas produced by the post-combustion hot chamber;

[0027] a second gas turbine that performs work on the expansion of the high temperature gas produced at the cathode;

[0028] a second compressor for compressing air;

[0029] A third compressor is used to compress oxygen.

[0030] As a preferred solution of the fuel cell and gas turbine hybrid power generation system of the present invention, the anode exhaust outlet and cathode exhaust outlet of the fuel cell body are respectively provided with splitters to re-introduce part of the anode exhaust and cathode exhaust into the anode and cathode.

[0031] As a preferred solution of the fuel cell and gas turbine hybrid power generation system of the present invention, the system further comprises a flue gas treatment module, which comprises a second condenser connected to the output end of the first heat exchanger, a first gas-liquid separator connected to the second condenser, a fourth compressor connected to the first gas-liquid separator, a third condenser connected to the fourth compressor, a second gas-liquid separator connected to the third condenser, a pump connected to the second gas-liquid separator, and a connecting pipeline;

[0032] Anode exhaust gas enters the flue gas treatment module through a first heat exchanger;

[0033] The first gas-liquid separator is used to separate water;

[0034] The second gas-liquid separator is used to separate nitrogen.

[0035] Beneficial effects of the invention: The invention designs anode and cathode dual circulation to improve the working efficiency of fuel cells, reduce the temperature gradient of fuel cells and prevent "carbon deposition", and combines Brayton power cycle power generation to recover waste heat of different temperatures generated by fuel cells and gas turbine systems to achieve cascade utilization of energy. At the same time, high-concentration CO2 is separated for recycling to reduce greenhouse gas emissions, and has the characteristics of strong operability, flexible operation mode, and significant energy-saving and carbon-reducing effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0037] Figure 1 It is a schematic diagram of the waste heat recovery unit of the present invention.

[0038] Figure 2 Schematic diagram of a fuel cell unit of the present invention. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0040] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0041] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0042] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0043] Example 1

[0044] Reference Figures 1-2, which is the first embodiment of the present invention, provides a fuel cell and gas turbine hybrid power generation system, including a fuel cell unit 100, which uses synthesis gas as fuel and is used to generate electricity through an electrochemical oxidation reaction; and a waste heat recovery unit 200, which is connected to the exhaust gas exhaust port of the fuel cell unit 100 and is used to process the exhaust gas discharged by the fuel cell unit 100 and recover heat energy.

[0045] The waste heat recovery unit 200 includes a first heat exchanger 300 connected to the exhaust gas outlet of the fuel cell unit 100, and a SCO2 Brayton cycle module 400 and a flue gas treatment module 500 connected to the first heat exchanger 300, supercritical carbon dioxide (hereinafter referred to as "SCO2"), the SCO2 Brayton cycle module 400 is a closed supercritical carbon dioxide Brayton cycle, which can achieve higher energy utilization efficiency than the water vapor Rankine cycle.

[0046] The SCO2 Brayton cycle module 400 includes a recompressor 401, a compression condensing unit 402, a low-temperature regenerator 403, a high-temperature regenerator 404, a CO2 turbine 405, a CO2 turbine 406, a second heat exchanger 407, and connecting pipes; the input ends of the recompressor 401 and the compression condensing unit 402 are both connected to the output end of the low-temperature regenerator 403; the output end of the compression condensing unit 402 is connected to the first heat exchanger 300, and the output end of the recompressor 401 is connected to the input end of the high-temperature regenerator 404; the output end of the high-temperature regenerator 404 is connected to the input end of the CO2 turbine 406, and the output end of the CO2 turbine 406 is connected to the input end of the low-temperature regenerator 403; the high-temperature regenerator 404, the second heat exchanger 407 and the CO2 turbine 405 circulate the gas through the pipe; the output end of the first heat exchanger 300 is connected to the input end of the high-temperature regenerator 404.

[0047] The SCO2 Brayton cycle module 400 further includes a first pipeline 408 connecting the compression condensing unit 402 and the low-temperature regenerator 403 , and gas can flow back from the compression condensing unit 402 to the low-temperature regenerator 403 through the first pipeline 408 .

[0048] The SCO2 Brayton cycle module 400 also includes a second pipeline 409 connecting the low-temperature regenerator 403 and the high-temperature regenerator 404, and another second pipeline 409 connecting the low-temperature regenerator 403 and the high-temperature regenerator 404; the gas enters the high-temperature regenerator 404 from the low-temperature regenerator 403 through the second pipeline 409; the gas enters the low-temperature regenerator 403 from the high-temperature regenerator 404 through the third pipeline.

[0049] The SCO2 Brayton cycle module 400 further includes a fourth pipeline 412 connecting the second heat exchanger 407 and the first heat exchanger 300 , which is used for the synthesis gas to participate in heat exchange.

[0050] The compression condensing unit 402 includes three first condensers 402a and three first compressors 402b. The first compressors 402b and the first condensers 402a are spaced apart in sequence. The first condenser 402a at the head end is connected to the output end of the low-temperature heat regenerator 403. The output end of the first compressor 402b at the tail end is divided into two pipelines, one of which is connected to the first heat exchanger 300, and the other is connected to the low-temperature heat regenerator 403.

[0051] In summary, according to the energy level of waste heat at different locations in the system, low-grade heat is first used to preheat and reheat SCO2, and then SCO2 is diverted according to the amount of high-grade heat to achieve the cascade utilization of different grades of energy. The waste heat utilization scheme is as follows: one stream is compressed by the re-compressor 401, and the other stream is compressed three times and inter-cooled three times by the compression condensing unit 402, and then is divided into two streams, one stream enters the first heat exchanger 300 to absorb the waste heat of the anode exhaust gas, the cathode exhaust gas and the synthesis gas, and the other stream enters the low-temperature regenerator 403 to recover the waste heat of CO2 and merges with the recompressed CO2, and then is mixed with one stream of CO2 and enters the high-temperature regenerator 404 to recover the waste heat of CO2. At this time, the high-grade waste heat of the synthesis gas is not utilized. The temperature of the supercritical carbon dioxide that absorbs the high-grade heat of the synthesis gas is set to 760°C. A part of SCO2 is used to absorb the high-grade heat of the synthesis gas and enters the high-temperature regenerator 404 after doing work through the CO2 turbine 405, and the rest enters the CO2 turbine 406 to directly expand and do work. After the two streams of CO2 merge, they enter the low-temperature regenerator 403 for heat exchange.

[0052] Example 2

[0053] Reference Figure 2 , which is the second embodiment of the present invention, and this embodiment is different from the first embodiment in that: the fuel cell unit 100 includes a fuel cell body 101, which includes a cathode and an anode; a post-combustion chamber 102, in which the remaining fuel that has not been completely consumed by the fuel cell body 101 is mixed with pure oxygen and burned; a first gas turbine 103, which expands the high-temperature gas generated by the post-combustion hot chamber; a second gas turbine 104, which expands the high-temperature gas generated by the cathode; a second compressor 105, which is used to compress air; and a third compressor 106, which is used to compress oxygen.

[0054] The fuel cell and gas turbine hybrid power generation system using synthesis gas as fuel generates electricity from solid oxide fuel cells and gas turbines. The air is first compressed by the second compressor 105 and then enters the cathode of the fuel cell body 101. The synthesis gas and water are mixed. This ensures that the operating temperature of the fuel cell body 101 is always between 800°C and 1000°C when the operating conditions are changed, preventing the electrode material from being damaged by excessive operating temperature. The mixed gas then enters the anode of the fuel cell body 101 and undergoes an electrochemical oxidation reaction with oxygen in the air to generate direct current.

[0055] The fuel cell body 101 cannot fully utilize the syngas, and the remaining syngas enters the post-combustion chamber 102 for mixed combustion with pure oxygen. The high-temperature gas generated by the post-combustion chamber 102 and the cathode enters the first gas turbine 103 and the second gas turbine 104 for expansion and work. Since pure oxygen is introduced into the post-combustion chamber 102, the products are mainly carbon dioxide and water vapor. This flue gas is cooled and separated by a series of heat exchanges to achieve CO2.

[0056] In summary, the anode exhaust outlet and cathode exhaust outlet of the fuel cell body 101 are respectively provided with diverters, which re-introduce a portion of the anode exhaust and cathode exhaust into the anode and cathode to increase the inlet temperature of the anode and cathode. This is an innovation compared to the traditional fuel cell exhaust process. The traditional fuel cell exhaust directly enters the gas turbine. The present system recirculates the anode exhaust and cathode exhaust of the gas turbine, which is beneficial to reducing the temperature gradient of the fuel cell and preventing carbon deposition, while improving the efficiency of the fuel cell.

[0057] The remaining structures are the same as those of Example 1.

[0058] Example 3

[0059] Reference Figure 1 , which is the third embodiment of the present invention. This embodiment is different from the second embodiment in that: the system also includes a flue gas treatment module 500, which includes a second condenser 501 connected to the output end of the first heat exchanger 300, a first gas-liquid separator 502 connected to the second condenser 501, a fourth compressor 506 connected to the first gas-liquid separator 502, a third condenser 503 connected to the fourth compressor 506, a second gas-liquid separator 504 connected to the third condenser 503, a pump 505 connected to the second gas-liquid separator 504, and connecting pipes.

[0060] The anode exhaust gas enters the flue gas treatment module 500 through the first heat exchanger 300 ; the first gas-liquid separator 502 is used to separate water, the second gas-liquid separator 504 is used to separate nitrogen, and the remaining liquid is discharged through the pump 505 .

[0061] The remaining structure is the same as that of Example 2.

[0062] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, and parameter values ​​(e.g., temperature, pressure, etc.), installation arrangement, use of materials, color, directional changes, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present invention. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure of performing the function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to several modifications still falling within the scope of the appended claims.

[0063] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0064] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0065] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A fuel cell and gas turbine hybrid power generation system, characterized in that: include, A fuel cell unit (100) for generating electrical energy through an electrochemical oxidation reaction; and A waste heat recovery unit (200) is connected to the waste gas discharge port of the fuel cell unit (100) and is used to process the waste gas discharged by the fuel cell unit (100) and recover heat energy.

2. The fuel cell and gas turbine hybrid power generation system according to claim 1, characterized in that: The waste heat recovery unit (200) comprises a first heat exchanger (300) connected to the exhaust gas discharge port of the fuel cell unit (100), and a SCO2 Brayton cycle module (400) and a flue gas treatment module (500) connected to the first heat exchanger (300).

3. The fuel cell and gas turbine hybrid power generation system according to claim 2, characterized in that: The SCO2 Brayton cycle module (400) includes a recompressor (401), a compression condensing unit (402), a low-temperature regenerator (403), a high-temperature regenerator (404), a CO2 turbine (405), a CO2 turbine (406), a second heat exchanger (407), and connecting pipes; The input ends of the recompressor (401) and the compression condensing unit (402) are both connected to the output end of the low-temperature regenerator (403); The output end of the compression condensing unit (402) is connected to the first heat exchanger (300), and the output end of the recompressor (401) is connected to the input end of the high-temperature regenerator (404); The output end of the high temperature regenerator (404) is connected to the input end of the CO2 turbine (406), and the output end of the CO2 turbine (406) is connected to the input end of the low temperature regenerator (403); The high temperature regenerator (404), the second heat exchanger (407) and the CO2 turbine (405) circulate the gas through the pipeline; The output end of the first heat exchanger (300) is connected to the input end of the high-temperature regenerator (404).

4. The fuel cell and gas turbine hybrid power generation system according to claim 3, characterized in that: The SCO2 Brayton cycle module (400) further includes a first pipeline (408) connecting the compression condensing unit (402) and the low-temperature regenerator (403), and the gas can flow back from the compression condensing unit (402) to the low-temperature regenerator (403) through the first pipeline (408).

5. The fuel cell and gas turbine hybrid power generation system according to claim 4, characterized in that: The SCO2 Brayton cycle module (400) further includes a second pipeline (409) connecting the low-temperature regenerator (403) and the high-temperature regenerator (404), and another second pipeline (409) connecting the low-temperature regenerator (403) and the high-temperature regenerator (404); The gas enters the high-temperature regenerator (404) from the low-temperature regenerator (403) through the second pipeline (409); The gas enters the low-temperature regenerator (403) from the high-temperature regenerator (404) through the third pipeline.

6. The fuel cell and gas turbine hybrid power generation system according to claim 5, characterized in that: The SCO2 Brayton cycle module (400) further comprises a fourth pipeline (412) connecting the second heat exchanger (407) and the first heat exchanger (300), which is used for the synthesis gas to participate in heat exchange.

7. The fuel cell and gas turbine hybrid power generation system according to claim 6, characterized in that: The compression condensing unit (402) includes three first condensers (402a) and three first compressors (402b), wherein the first compressors (402b) and the first condensers (402a) are spaced apart in sequence, wherein the first condenser (402a) at the head end is connected to the output end of the low-temperature heat regenerator (403), and the output end of the first compressor (402b) at the tail end is divided into two pipelines, wherein one pipeline is connected to the first heat exchanger (300), and the other pipeline is connected to the low-temperature heat regenerator (403).

8. The fuel cell and gas turbine hybrid power generation system according to claim 7, characterized in that: The fuel cell unit (100) comprises: A fuel cell body (101) comprising a cathode and an anode; A post-combustion chamber (102), in which the remaining fuel that has not been completely consumed by the fuel cell body (101) is mixed with pure oxygen and combusted; A first gas turbine (103) performs work on the expansion of high-temperature gas generated by the post-combustion hot chamber; A second gas turbine (104) performs work on the expansion of the high temperature gas generated by the cathode; a second compressor (105) for compressing air; A third compressor (106) is used to compress oxygen.

9. The fuel cell and gas turbine hybrid power generation system according to claim 8, characterized in that: The anode exhaust outlet and cathode exhaust outlet of the fuel cell body (101) are respectively provided with flow dividers to redirect a portion of the anode exhaust and cathode exhaust into the anode and cathode.

10. The fuel cell and gas turbine hybrid power generation system according to claim 2 or 9, characterized in that: The system further comprises a flue gas treatment module (500), which comprises a second condenser (501) connected to the output end of the first heat exchanger (300), a first gas-liquid separator (502) connected to the second condenser (501), a fourth compressor (506) connected to the first gas-liquid separator (502), a third condenser (503) connected to the fourth compressor (506), a second gas-liquid separator (504) connected to the third condenser (503), a pump (505) connected to the second gas-liquid separator (504), and a connecting pipeline; Anode exhaust gas enters the flue gas treatment module (500) through a first heat exchanger (300); The first gas-liquid separator (502) is used to separate water; The second gas-liquid separator (504) is used to separate nitrogen.

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