Solid oxide fuel cell-gas turbine-organic Rankine cycle hybrid power generation system based on low-temperature ammonia reforming

Abstract

The invention relates to a solid oxide fuel cell-gas turbine-organic Rankine cycle hybrid power generation system based on low-temperature ammonia reforming. The system comprises a liquid ammonia tank, a flat plate type heat exchanger, a buffer tank, a three-way valve, a fuel compressor, an ammonia reformer, a heat exchanger, a purifier, a solid oxide fuel cell, an air compressor, a mixing chamber, a power electronic converter, a gas turbine, a combustion chamber, a generator, a water pump, a working medium pump, a water tank, a working medium storage tank, a cooler, a working medium evaporator and an expansion machine. The liquid ammonia is used as a raw material to realize on-site low-temperature ammonia reforming hydrogen production, the technical problems of hydrogen storage and hydrogen transportation are effectively solved, and the possibility that ammonia fuel is directly used for a fuel cell to generate nitrogen oxide is avoided. According to the system, heat of the system is fully recycled, the fuel consumption and emission of nitric oxide are effectively reduced, and the economical efficiency and the environmental protection property of the system are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of distributed energy, and particularly relates to a solid oxide fuel cell - gas turbine - organic Rankine cycle (SOFC - GT - ORC) hybrid power generation system based on low - temperature ammonia reforming technology. Background Technique

[0002] In recent years, with the transformation of the energy structure and the demand for low - carbonization, higher and higher requirements have been put forward for the energy system. Solid oxide fuel cells have become a research hotspot in the field of distributed energy due to their high efficiency and low - emission characteristics, and are often combined with GT to form a combined cycle system to improve the overall efficiency. Traditional SOFC - GT systems use hydrogen storage tanks to supply hydrogen, which has high requirements for the device and safety hazards. The flammable and explosive characteristics of hydrogen increase the costs of transportation and storage. Ammonia can be produced by green methods such as wind power and photovoltaic waste electricity, and can also be directly transported using the globally mature liquid ammonia storage and transportation network. Therefore, ammonia, with its core advantages such as high hydrogen storage density, low storage and transportation costs, and high safety, solves the pain points of "difficult storage and transportation, high cost, and high risk" faced by the commercialization of hydrogen energy. Existing SOFC - GT systems for ammonia reforming to produce hydrogen generally use ammonia direct combustion to heat ammonia decomposition (such as patent CN117307319A), and ammonia combustion will produce nitrogen oxides; in a direct ammonia - fuel SOFC power generation system (such as patent CN220106596U), ammonia may poison the anode catalyst (such as nickel - based), and the long - term operation stability is limited. Summary of the Invention

[0003] To solve the above problems, the present invention proposes an SOFC - GT - ORC hybrid power generation system based on low - temperature ammonia reforming technology. The hybrid power generation system uses indirect low - temperature ammonia reforming to produce hydrogen, reducing the requirement for the quality of waste heat. When the system operates stably, the gas turbine exhaust gas can provide sufficient heat for ammonia reforming, effectively avoiding the problem of nitrogen oxide emissions caused by ammonia direct combustion for heating. The gas turbine generates electricity by burning the SOFC exhaust gas (unreacted hydrogen), and the waste heat of its exhaust gas is utilized in multiple stages, such as ammonia reforming heating, ammonia and air preheating, water evaporation, and organic Rankine cycle working fluid heating, improving the comprehensive energy utilization efficiency and system economy.

[0004] Objective of the Invention: Aiming at the problems existing in the existing energy systems, such as too high ammonia decomposition temperature, insufficient waste heat utilization, and low multi - energy coupling efficiency, the present invention proposes an efficient power generation system that uses ammonia reforming as the front - end hydrogen supply and combines SOFC, GT, and ORC. The energy conversion of the hybrid system includes heat energy - chemical energy - electrical energy / heat energy - mechanical energy - electrical energy: the ammonia reforming reaction is driven by the waste heat of the gas turbine exhaust gas, and hydrogen production from ammonia is realized under low - temperature conditions (500 °C); the purified hydrogen and air undergo an electrochemical reaction in the SOFC to generate electricity directly; the unreacted hydrogen in the high - temperature exhaust gas of the SOFC is mixed with air and burned to produce high - temperature and high - pressure gas, which drives the gas turbine to do work and drive the first generator to output electrical energy; the heat of the gas turbine exhaust gas after passing through the ammonia reformer, the pre - heaters of ammonia and air is recovered and utilized by the ORC system, and is converted into electrical energy for output.

[0005] Technical Solution: The present invention constructs a SOFC - GT - ORC power generation system based on low - temperature ammonia reforming.

[0006] The connection path of the ammonia fuel supply system: The liquid ammonia tank is connected to the plate - type heat exchanger, the plate - type heat exchanger is connected to the buffer tank, and the buffer tank is respectively connected to the combustion chamber of the fuel compressor and the ammonia reformer through the first three - way valve. The fuel compressor is connected to the second mixing chamber and the first heat exchanger through the second three - way valve, and the first heat exchanger is connected to the reforming reaction chamber of the reformer.

[0007] The connection path between the solid oxide fuel cell system and the gas turbine system is as follows: The purifier is connected to the first mixing chamber in the SOFC, the first mixing chamber is connected to the water evaporator and the solid oxide SOFC in the ORC system, the SOFC is connected to the power electronic converter, and the SOFC exhaust gas is connected to the two mixing chambers through the third three - way valve. The second mixing chamber in the GT system is connected to the combustion chamber, the combustion chamber is connected to the gas turbine, and the gas turbine is connected to the first generator.

[0008] The ORC connection path is as follows: The first water tank is connected to the first water pump, the first water pump is connected to the water evaporator, the water evaporator is connected to the working fluid evaporator and the first mixing chamber in the SOFC, the working fluid evaporator is connected to the working fluid compressor, the working fluid compressor is connected to the third heat exchanger and the second generator in the ORC, the third heat exchanger is connected to the cooler and the working fluid storage tank, the working fluid storage tank is connected to the working fluid evaporator through the working fluid pump, and the cooler is connected to the third heat exchanger through the second water tank and the second water pump, forming a complete ORC cycle.

[0009] When the system operates stably, the reformer uses vaporized ammonia as the raw material, and fully utilizes the exhaust gas of the gas turbine to supply heat to decompose ammonia into hydrogen and nitrogen. After purification, it is mixed with water vapor and the exhaust gas of the SOFC anode part in the first mixing chamber and then enters the SOFC. In this process, the reformer uses the heat of the exhaust gas to provide the necessary energy for the reaction, greatly improving the comprehensive utilization rate of energy.

[0010] The SOFC realizes efficient power generation through an integrated catalytic reforming-electrochemical conversion mechanism. On the anode side, high-purity hydrogen decomposed by the ammonia reformer reacts electrochemically with preheated air (preheated by the exhaust gas of the gas turbine), while releasing electrical energy.

[0011] Utilization of primary exhaust gas: The anode exhaust gas of the SOFC is transported to the GT combustion chamber through a high-temperature-resistant pipeline, and mixed and burned with the oxygen-rich cathode exhaust gas of the SOFC to drive the turbine to generate electricity;

[0012] Secondary waste heat recovery: The high-temperature GT exhaust gas provides the heat required for ammonia reforming for the ammonia reformer. After preheating ammonia and air, it enters the ORC system for heat supply;

[0013] The ORC system effectively improves the energy utilization efficiency of the overall system by recovering and utilizing the waste heat of the SOFC-GT system.

[0014] Furthermore, the hybrid power generation system uses pure liquid ammonia as the raw material. The liquid ammonia is vaporized through the plate heat exchanger and stored in the buffer tank, and then is transported to the ammonia reformer and the combustion chamber according to the demand by the first three-way valve in proportion.

[0015] Furthermore, the ammonia reformer conducts a reforming reaction with the help of the preheating of the gas turbine exhaust gas. The ammonia entering the reformer is decomposed into hydrogen and nitrogen, and after being purified by the purifier, it is mixed with the water vapor generated by the water evaporator and the exhaust gas of the SOFC anode part in the second mixing chamber.

[0016] Furthermore, the mixed gas and the air compressed by the air compressor are jointly introduced into the SOFC for an electrochemical reaction, and electricity is generated through the power electronic converter. Part of the anode exhaust gas and the oxygen-rich cathode exhaust gas discharged from the SOFC are introduced into the combustion chamber of the GT.

[0017] Furthermore, the exhaust gas mixture burns in the combustion chamber to generate high-temperature and high-pressure gas, which enters the turbine. The turbine rotates coaxially with the first generator to drive the motor to generate electricity. The exhaust gas of the gas turbine enters the reformer, provides the heat required for decomposition, and preheats the compressed ammonia and the air at the SOFC inlet, and then sequentially enters the water evaporator and the working fluid evaporator of the ORC system.

[0018] The ORC system recovers the waste heat in the exhaust gas of the gas turbine, causing the R123 working fluid to evaporate into high-temperature and high-pressure steam. This steam drives an expander to generate electricity. After power generation, the steam is cooled into a liquid through the third heat exchanger and then re-enters the working fluid storage tank to form a cycle. Making full use of the heat in the exhaust gas of the gas turbine can effectively improve the overall energy efficiency of the system.

[0019] Advantages of the present invention:

[0020] A SOFC-GT-ORC hybrid power generation system based on low-temperature ammonia reforming technology is proposed. This system uses liquid ammonia as a raw material and can realize on-site hydrogen production, effectively avoiding the technical problems of hydrogen storage and transportation and improving safety. The reaction temperature for decomposing ammonia into nitrogen and hydrogen through the reformer is 500 °C. During stable operation, the system can achieve heat self-balance, and the ammonia reformer no longer requires ammonia combustion for heating, effectively avoiding nitrogen oxide emissions.

[0021] During stable operation of the system, the waste heat of the gas turbine exhaust gas can meet the heating requirements of the low-temperature ammonia reforming reaction, achieving heat self-balance of the system. The ORC is used to further recover the waste heat of the gas turbine exhaust gas, effectively improving the energy utilization rate of the hybrid power generation system and improving economic benefits. During stable operation of the system, the anode exhaust gas of the SOFC is introduced into the gas turbine to provide fuel for it. The ammonia reformer does not require ammonia combustion for heating, and the system can effectively avoid the problem of nitrogen oxides generated by ammonia combustion, with higher environmental friendliness. Description of the Drawings

[0022] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0023] Figure 1 As indicated by the reference numerals: 1. Liquid ammonia storage tank, 2. Plate heat exchanger, 3. Buffer tank, 4. First three-way valve, 5. Fuel compressor, 6. Second three-way valve, 7. First heat exchanger, 8. Ammonia reformer, 9. Purifier, 10. First mixing chamber, 11. Solid oxide fuel cell, 12. Power electronic converter, 13. Third three-way valve, 14. Second mixing chamber, 15. Combustion chamber, 16. Gas turbine, 17. First generator, 18. Air compressor, 19. Second heat exchanger, 20. First water tank, 21. First water pump, 22. Water evaporator, 23. Working fluid evaporator, 24. Working fluid pump, 25. Working fluid storage tank, 26. Third heat exchanger, 27. Second water pump, 28. Second water tank, 29. Cooler, 30. Second generator, 31. Expander. Detailed Embodiments

[0024] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0025] As Figure 1 shown, a SOFC-GT-ORC hybrid power generation system based on low-temperature ammonia reforming technology constructed by the present invention, the hybrid power generation system includes: an ammonia fuel supply system, a solid oxide fuel cell system, a gas turbine system, and an organic Rankine cycle system. The ammonia fuel supply system includes: a liquid ammonia tank 1, a plate heat exchanger 2, a buffer tank 3, a first three-way valve 4, a fuel compressor 5, an ammonia reformer 8, a first heat exchanger 7, a purifier 9, a second three-way valve 6; the solid oxide fuel cell system includes: a solid oxide fuel cell 11, an air compressor 18, a second heat exchanger 19, a first mixing chamber 10, a power electronic converter 12, a third three-way valve 13, a first water tank 20, a first water pump 21, a water evaporator 22; the gas turbine system includes: a gas turbine 16, a combustion chamber 15, a first generator 17, a second mixing chamber 14; the organic Rankine cycle system includes: a third heat exchanger 26, a second water pump 27, a working fluid pump 24, a second water tank 28, a working fluid storage tank 25, a cooler 29, a working fluid evaporator 23, a water evaporator 22, an expander 31, a second generator 30;

[0026] The specific working process of the present invention is as follows:

[0027] When the system is in the stable operation power generation stage, liquid ammonia flows out from the storage tank 1, is vaporized by the plate heat exchanger 2 and temporarily stored in the buffer tank 3, enters the fuel compressor 5 through the first three-way valve 4, and the pressurized ammonia gas enters the reformer 8 to undergo a cracking reaction by the tail gas heat supply of the gas turbine 16, cracking to generate hydrogen and nitrogen. After passing through the purifier 9, it is mixed with the water vapor from the water evaporator 22 and the anode part tail gas of the solid oxide fuel cell 11 in the first mixing chamber 10, and then sent into the solid oxide fuel cell 11 for power conversion. The anode tail gas of the solid oxide fuel cell 11 and the cathode tail gas of the solid oxide fuel cell 11 enter the second mixing chamber 14 through the third three-way valve 13, and further enter the combustion chamber 15 to burn, generating high-temperature and high-pressure gas, which is used for power generation by the gas turbine 16. The tail gas of the gas turbine 16 is introduced into the reformer 8 to provide the heat required for ammonia cracking and preheat the ammonia gas to be decomposed and the air at the inlet of the solid oxide fuel cell 11, and finally enters the water evaporator 22 and the working fluid evaporator 23 in sequence, thus realizing the energy cycle and comprehensive utilization of the entire system.

[0028] The material utilization path of the hybrid power generation system device based on low-temperature ammonia reforming for hydrogen production:

[0029] Fuel cycle: During the startup phase of the hybrid power generation system, ammonia serves as the fuel source for the system devices and functions through two different branches. In the first branch, liquid ammonia is vaporized by the flat-plate heat exchanger 2 and then transported to the buffer tank 3. It is then proportionally transported into the reformer 8 through the first three-way valve 4, where a combustion reaction occurs, providing the initial heat source for ammonia reforming. In the second branch, ammonia gas enters the fuel compressor 5 for pressurization. The pressurized ammonia gas is distributed through the second three-way valve 6. A part of the ammonia gas enters the reformer 8 through the first heat exchanger 7 to undergo an ammonia cracking reaction, and another part of the ammonia gas is distributed to the gas turbine system 16 as the initial fuel source for the gas turbine 16. During the stable operation phase of the hybrid power generation system, liquid ammonia is vaporized by the flat-plate heat exchanger 2 and then transported to the buffer tank 3. After being pressurized by the fuel compressor 5 and heated by the first heat exchanger 7, it directly enters the ammonia reformer 8, where a cracking reaction occurs by the heat provided by the gas turbine exhaust gas, generating reformed syngas rich in hydrogen. These syngases are purified and then mixed with water vapor and the exhaust gas of the solid oxide fuel cell 11 and enter the solid oxide fuel cell 11, providing fuel guarantee for the continuous operation of the stack and ensuring that the solid oxide fuel cell 11 can work stably and efficiently.

[0030] Air cycle: In this system, air is the key gas for the reaction entering the solid oxide fuel cell 11 and the combustion chamber 15, and its process is as follows: Ambient air is introduced into the air compressor 18 for compression to obtain a gas with higher temperature and pressure. Then, it is further heated by the exhaust gas of the gas turbine 16 in the second heat exchanger 19 to form a high-temperature gas. The heated gas is mixed with vaporized ammonia and enters the cathode of the solid oxide fuel cell 11, providing the necessary conditions for the normal operation of the solid oxide fuel cell 11.

[0031] Water cycle: During the operation of the entire system, the water pump plays the role of transporting key materials. There are two water transportation paths in this system: The first one is that the water in the first water tank 20 becomes water vapor through the water evaporator 21 and is introduced into the first mixing chamber 10 to be fully mixed with the hydrogen from the purifier 9, and then enters the solid oxide fuel cell to react. The second one is that the water in the second water tank 28 is pumped through the second water pump 27 to the third heat exchanger 26 to cool the high-temperature working medium R123. After absorbing the heat, the water is cooled by the cooler 29 and then re-enters the water tank 28 to complete the cooling cycle.

[0032] ORC Cycle: The working fluid R123 in the working fluid storage tank 25 is pressurized by the working fluid pump 24 and enters the working fluid evaporator 23. The working fluid evaporator 23 uses the waste heat of the exhaust gas of the gas turbine 16 to evaporate the working fluid R123, forming high-temperature and high-pressure steam. This steam does work and generates electricity through the expander 31. The reacted working fluid R123 steam enters the third heat exchanger 26 through a pipeline for water cooling circulation, and the cooled working fluid R123 re-enters the working fluid storage tank 25 to complete the organic Rankine cycle.

[0033] Furthermore, the heat recovery of the system is mainly reflected in two aspects: First, the unreacted gas in the exhaust gas of the solid oxide fuel cell 11 enters the gas turbine combustion chamber 15 and the cathode of the solid oxide fuel cell respectively through the third three-way valve 13, enabling full utilization of the fuel and greatly improving the energy utilization rate; Second, the exhaust gas of the gas turbine is introduced into the reformer to provide the heat required for decomposition. The remaining heat preheats the ammonia to be decomposed after pressurization and the air at the inlet of the solid oxide fuel cell 11, and finally enters the water evaporator 22 and the working fluid evaporator 23 of the organic Rankine cycle system in sequence, realizing the heat recovery of the SOFC-GT system.

[0034] The working process of the SOFC-GT-ORC system is as follows: Liquid ammonia is vaporized through the plate heat exchanger and stored in the buffer tank, and is delivered to the ammonia reformer and the combustion chamber as needed through the first three-way valve. A part of the ammonia enters the reformer for combustion to provide the initial heat for ammonia reforming; a part of the ammonia is pressurized by the fuel compressor, and one stream of ammonia enters the ammonia reformer through the first heat exchanger to react, generating hydrogen and nitrogen. After purification, it is mixed with the water vapor from the water evaporator and a part of the exhaust gas from the SOFC anode in the first mixing chamber. The mixed gas enters the SOFC stack for a chemical reaction and outputs electrical energy through the power electronic converter; another stream of ammonia is mixed with the exhaust gas discharged from the SOFC in the second mixing chamber and enters the combustion chamber, and the combustion produces high-temperature and high-pressure gas, which outputs electrical energy through the gas turbine and the first generator. The exhaust gas of the gas turbine enters the ammonia reformer to provide heat for ammonia reforming; then it preheats the ammonia to be reformed after pressurization and the air entering the SOFC; finally, it enters the water evaporator and the ORC working fluid evaporator in sequence to heat the water and the working fluid. The evaporated working fluid enters the expander to do work and drive the second generator to generate electricity.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this invention belongs. The terms used in the description of this invention herein are only for the purpose of describing specific embodiments and are not intended to limit the invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0036] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0037] The above-described embodiments merely represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed. However, it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A solid oxide fuel cell-gas turbine-organic Rankine cycle hybrid power generation system based on low temperature ammonia reforming, characterized in that: include: Ammonia fuel supply system, solid oxide fuel cell system, gas turbine system, organic Rankine cycle system; the ammonia fuel supply system includes: liquid ammonia tank, flat plate heat exchanger, buffer tank, first three-way valve, second three-way valve, fuel compressor, ammonia reformer, first heat exchanger, purifier; solid oxide fuel cell system includes: solid oxide fuel cell, air compressor, second heat exchanger, first mixing chamber, power electronic converter, third three-way valve, first water tank, first water pump, water evaporator; gas turbine system includes: gas turbine, combustion chamber, first generator, second mixing chamber; organic Rankine cycle system includes: third heat exchanger, second water pump, working fluid pump, second water tank, working fluid storage tank, cooler, working fluid evaporator, expander, second generator.

2. The system according to claim 1, characterized in that: The connection path of the ammonia fuel supply system: the liquid ammonia tank is connected to the flat plate heat exchanger, the flat plate heat exchanger is connected to the buffer tank, the buffer tank is connected to the combustion chamber of the fuel compressor and the ammonia reformer through the first three-way valve, the fuel compressor is connected to the second mixing chamber and the first heat exchanger through the second three-way valve, and the first heat exchanger is connected to the reforming reaction chamber of the reformer.

3. The system according to claim 1, characterized in that: The connection path between the solid oxide fuel cell system and the gas turbine system is as follows: the purifier is connected to the first mixing chamber in the SOFC, the first mixing chamber is connected to the water evaporator and the solid oxide SOFC in the ORC system, the SOFC is connected to the power electronic converter, and the SOFC exhaust gas is connected to the two mixing chambers through the third three-way valve, the second mixing chamber in the GT system is connected to the combustion chamber, the combustion chamber is connected to the gas turbine, and the gas turbine is connected to the first generator.

4. The system according to claim 1, characterized in that: The ORC connection path is as follows: the first water tank is connected to the first water pump, the first water pump is connected to the water evaporator, the water evaporator is connected to the working fluid evaporator and the first mixing chamber in the SOFC, the working fluid evaporator is connected to the working fluid compressor, the working fluid compressor is connected to the third heat exchanger and the second generator in the ORC, the third heat exchanger is connected to the cooler and the working fluid storage tank, the working fluid storage tank is connected to the working fluid evaporator through the working fluid pump, and the cooler is connected to the third heat exchanger through the second water tank and the second water pump, forming a complete ORC cycle.

5. The system according to claim 1, characterized in that: The system uses liquid ammonia as raw material and can realize on-site hydrogen production; the reaction temperature of decomposing ammonia into nitrogen and hydrogen by the reformer is 500°C.

6. The system according to claim 1, characterized in that: The ammonia reformer comprises a combustion chamber and a reaction chamber; the combustion chamber is outside the reformer and can completely wrap the reaction chamber, and an ammonia combustion reaction occurs in the combustion chamber; and the reaction chamber is inside the reformer, and an ammonia catalytic decomposition reaction occurs.

7. The system according to claim 1, characterized in that: When the hybrid power generation system starts to operate, the ammonia reformer uses the heat provided by the combustion chamber to perform a catalytic decomposition reaction; when the system operates stably, the ammonia reformer uses the waste heat of the gas turbine exhaust introduced into the combustion chamber to perform a catalytic decomposition reaction.

8. The system according to claim 1, characterized in that: The organic Rankine cycle system uses the heat of the gas turbine exhaust gas to heat the working fluid R123 in the working fluid evaporator. The high-temperature and high-pressure R123 steam drives the expander to generate electricity. The R123 steam after power generation is condensed into liquid through the heat exchanger and returned to the working fluid storage tank. The R123 in the working fluid storage tank is pressurized and sent to the working fluid evaporator through the working fluid pump to form a closed cycle.

9. The system according to claim 1, characterized in that: The heat of the gas turbine exhaust gas is utilized to provide heat for the catalytic decomposition reaction of ammonia, preheating of ammonia and air, and heating of water and R123 working fluid, thereby fully utilizing the heat of the gas turbine exhaust gas.

10. The system according to any one of claims 1 to 9, characterized in that include: A hybrid power generation system based on low-temperature ammonia reforming technology has been constructed to reduce the requirements of the waste heat utilization system on the quality of waste heat. It can utilize the waste heat of gas turbine exhaust in a cascade manner, improve system efficiency, improve economic benefits, and promote environmental protection.

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