Solid fuel cell-split transcritical carbon dioxide combined cycle system

Abstract

The invention provides a solid fuel cell-split transcritical carbon dioxide combined cycle system, which comprises a solid oxide fuel cell adopting ammonia-hydrogen mixed gas as fuel, and a cathode exhaust port of the solid oxide fuel cell is communicated with an inlet of the split transcritical carbon dioxide combined cycle system. The exhaust waste heat is used for heating carbon dioxide; an anode exhaust port of the solid oxide fuel cell is communicated with an inlet of the hydrogen circulating separation device; an outlet of the hydrogen circulating separation device is communicated with an anode layer of the solid oxide fuel cell; the ammonia-hydrogen mixed gas is used as the fuel of the solid oxide fuel cell, so that the cost is low, the safety is good, and the efficiency is higher; hydrogen exhausted from the anode is separated by the hydrogen circulating separation device and is used as fuel of the anode, so that higher energy utilization efficiency is achieved; the waste heat of the discharged gas is utilized by utilizing split-flow transcritical carbon dioxide circulation, so that efficient cyclic utilization of heat is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of energy generation, and in particular to a solid fuel cell-divided flow transcritical carbon dioxide combined cycle system. Background Art

[0002] As the third generation fuel cell, SOFC has the advantages of high power generation efficiency (its own power generation efficiency is close to 60%, and the efficiency can reach more than 80% when used in conjunction with a hot gas turbine), high cogeneration efficiency (cogeneration efficiency is more than 90%), water conservation, green environmental protection, easy modular assembly, wide range of fuel selection (natural gas, coal gas, biomass gas, methanol, etc. can be used), and no need for precious metal catalysts. At present, the fuels used by SOFC mainly include traditional fossil fuels such as natural gas and coal gas. These fuels will produce greenhouse gas emissions such as carbon dioxide during use, causing certain pollution to the environment. With the emphasis on environmental protection and sustainable development, the use of traditional fossil fuels as SOFC fuels has limited its environmental performance and market promotion to a certain extent. In order to further improve the environmental performance of SOFC, updating fuels has become an important research direction.

[0003] Furthermore, SOFC generates a large amount of waste heat during the power generation process, which has a high utilization value. At present, the utilization methods of SOFC waste heat mainly include the following:

[0004] 1. Combined heat and power: The electricity and heat generated by SOFC are supplied to users at the same time to improve energy efficiency. The waste heat of SOFC can be used in heating, hot water supply and other fields to achieve efficient use of combined heat and power.

[0005] 2. Waste heat recovery power generation: Use power cycles (such as transcritical carbon dioxide cycles) to recover SOFC exhaust waste heat and convert it into electrical energy or thermal energy for reuse. This method can further improve the overall efficiency of the system and reduce energy consumption.

[0006] 3. Hot air recycling: The air temperature out of the SOFC stack is very high, and this heat can also be used. For example, the hot air out of the stack can be recycled, which not only improves energy utilization efficiency but also eliminates unnecessary cooling treatment.

[0007] Although certain results have been achieved in the utilization of SOFC waste heat, further research and exploration are still needed to better integrate waste heat utilization technology with the SOFC system to optimize the overall efficiency.

[0008] In summary, as an efficient and clean energy conversion technology, SOFC still has great room for development and potential in fuel renewal and waste heat utilization. Summary of the invention

[0009] In order to solve the problems existing in the prior art, the present invention provides a solid fuel cell-divided flow transcritical carbon dioxide combined cycle system, which uses ammonia and hydrogen as fuels for the solid oxide fuel cell. Ammonia water has the characteristics of mature production process, relatively low toxicity, non-flammability, and easy liquefaction and transportation; hydrogen has the advantages of being pollution-free and having a high calorific value; a hydrogen circulation separation device is used to separate the hydrogen and nitrogen in the anode exhaust of the solid oxide fuel cell, and the hydrogen is reused to improve the system efficiency; the cathode exhaust of the solid fuel cell is introduced into the diverted flow transcritical carbon dioxide system for waste heat utilization, thereby efficiently recycling the heat of the solid fuel cell.

[0010] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a solid fuel cell-divided transcritical carbon dioxide combined cycle system, comprising a solid fuel cell system, a diverted transcritical carbon dioxide circulation system and a hydrogen circulation separation device, the solid fuel cell system comprising a solid oxide fuel cell using an ammonia-hydrogen mixed gas as fuel, the cathode exhaust port of the solid oxide fuel cell being connected to the inlet of the diverted transcritical carbon dioxide circulation system for heating carbon dioxide using waste heat from the exhaust gas; the anode exhaust port of the solid oxide fuel cell being connected to the inlet of the hydrogen circulation separation device, and the outlet of the hydrogen circulation separation device being connected to the anode layer of the solid oxide fuel cell.

[0011] Furthermore, the solid fuel cell system further comprises an air compressor, an air regenerator, a first self-heater, a second self-heater and an anode fuel mixer, wherein:

[0012] The outlet of the air compressor is connected to the air inlet of the air regenerator, the air outlet of the air regenerator is connected to the air inlet of the first self-heater, and the air outlet of the first self-heater is connected to the cathode layer of the solid oxide fuel cell;

[0013] The ammonia-hydrogen mixed gas outlet in the anode fuel mixer is communicated with the ammonia-hydrogen mixed gas inlet of the second autoheater, and the ammonia-hydrogen mixed gas outlet of the second autoheater is communicated with the anode layer of the solid oxide fuel cell;

[0014] The heat source inlet of the first self-heater is connected to the cathode exhaust port of the solid oxide fuel cell, and the heat source outlet of the first self-heater is connected to the heat source inlet of the split-flow transcritical carbon dioxide circulation system;

[0015] The heat source inlet of the second self-heater is connected to the anode exhaust port of the solid oxide fuel cell, the heat source outlet of the second self-heater is connected to the heat source inlet of the air regenerator, and the heat source outlet of the air regenerator is connected to the inlet of the hydrogen circulation separation device.

[0016] Furthermore, the inlet of the anode fuel mixer is connected to the outlet of the hydrogen storage tank, the outlet of the ammonia storage tank and the outlet of the hydrogen circulation separation device, and the hydrogen and ammonia are mixed in the anode fuel mixer at a volume ratio of 0.3 to 0.7.

[0017] Furthermore, the hydrogen circulation separation device includes a condenser, a feed compressor and a palladium membrane. The anode exhaust of the solid fuel cell system is passed into the inlet of the condenser after two heat exchanges. The gas outlet of the condenser is connected to the inlet of the feed compressor. The outlet of the feed compressor is connected to the inlet of the palladium membrane for separating and filtering out the hydrogen in the anode exhaust and passing the hydrogen into the solid fuel cell system.

[0018] Furthermore, the hydrogen circulation separation device includes a condenser, a feed compressor and a palladium membrane, the heat source outlet of the air regenerator is connected to the inlet of the condenser, the gas outlet of the condenser is connected to the inlet of the feed compressor, the outlet of the feed compressor is connected to the palladium membrane, and the outlet of the palladium membrane is connected to the inlet of the anode fuel mixer.

[0019] Furthermore, the split-flow transcritical carbon dioxide circulation system includes: a low-temperature heater, a high-temperature heater, a carbon dioxide turbine, a generator, a carbon dioxide regenerator, a carbon dioxide mixer, a carbon dioxide separator, a carbon dioxide pump, and a carbon dioxide condenser. The cathode exhaust of the solid fuel cell system is introduced into the heat source inlet of the high-temperature heater after a primary heat exchange, the heat source outlet of the high-temperature heater is connected to the heat source inlet of the low-temperature heater, and the heat source outlet of the low-temperature heater is connected to the atmosphere.

[0020] The outlet of the carbon dioxide turbine is connected to the heat source inlet of the carbon dioxide regenerator, the heat source outlet of the carbon dioxide regenerator is connected to the inlet of the carbon dioxide condenser, the outlet of the carbon dioxide condenser is connected to the inlet of the carbon dioxide pump, the outlet of the carbon dioxide pump is connected to the inlet of the carbon dioxide separator for separating the carbon dioxide into two streams, the first outlet of the carbon dioxide separator is connected to the material inlet of the low-temperature heater, the second outlet of the carbon dioxide separator is connected to the material inlet of the carbon dioxide regenerator, the material outlets of the low-temperature heater and the carbon dioxide regenerator are both connected to the inlet of the carbon dioxide mixer, the outlet of the carbon dioxide mixer is connected to the material inlet of the high-temperature heater, and the material outlet of the high-temperature heater is connected to the inlet of the carbon dioxide turbine.

[0021] Furthermore, the split-flow transcritical carbon dioxide circulation system comprises: a low-temperature heater, a high-temperature heater, a carbon dioxide turbine, a generator, a carbon dioxide regenerator, a carbon dioxide mixer, a carbon dioxide separator, a carbon dioxide pump, and a carbon dioxide condenser, wherein the heat source outlet of the first self-heater is connected to the heat source inlet of the high-temperature heater, the heat source outlet of the high-temperature heater is connected to the heat source inlet of the low-temperature heater, and the heat source outlet of the low-temperature heater is connected to the atmosphere;

[0022] The outlet of the carbon dioxide turbine is connected to the heat source inlet of the carbon dioxide regenerator, the heat source outlet of the carbon dioxide regenerator is connected to the inlet of the carbon dioxide condenser, the outlet of the carbon dioxide condenser is connected to the inlet of the carbon dioxide pump, the outlet of the carbon dioxide pump is connected to the inlet of the carbon dioxide separator for separating the carbon dioxide into two streams, the first outlet of the carbon dioxide separator is connected to the material inlet of the low-temperature heater, the second outlet of the carbon dioxide separator is connected to the material inlet of the carbon dioxide regenerator, the material outlets of the low-temperature heater and the carbon dioxide regenerator are both connected to the inlet of the carbon dioxide mixer, the outlet of the carbon dioxide mixer is connected to the material inlet of the high-temperature heater, and the material outlet of the high-temperature heater is connected to the inlet of the carbon dioxide turbine.

[0023] Furthermore, the carbon dioxide is divided into two streams according to a distribution ratio of 0.3 to 0.7 in the carbon dioxide separator.

[0024] Furthermore, the fuel utilization rate of the solid oxide fuel cell is 0.6-0.85, and the inlet temperature is 750°C.

[0025] Furthermore, the power of the air compressor is 425kW to 484kW, the power of the feed compressor is 196kW to 35kW, and the power of the carbon dioxide pump is 67kW to 101kW.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] The present invention provides a solid fuel cell-split transcritical carbon dioxide combined cycle system. Solid oxide fuel cells usually use fossil fuels, which have potential environmental problems, while ammonia and hydrogen do not have environmental problems, but hydrogen is difficult to store and transport. Ammonia is a good carrier for hydrogen and is easy to transport and store. In the present invention, a mixed gas of ammonia and hydrogen is used as the fuel of the solid oxide fuel cell. Compared with pure hydrogen SOFC, it has low cost and good safety, and at the same time has higher efficiency than pure ammonia SOFC.

[0028] Furthermore, the present invention implements anode recycling technology through a hydrogen circulation separation device, uses the hydrogen circulation separation device to filter the anode exhaust, separates the hydrogen, and recycles it as anode fuel, thereby achieving higher energy utilization efficiency.

[0029] Furthermore, since the exhaust temperature of the solid oxide fuel cell is very high, the waste heat of the exhaust gas from the anode and cathode is utilized by a split-flow transcritical carbon dioxide cycle and an air recuperator, wherein the carbon dioxide separator in the split-flow transcritical carbon dioxide cycle separates the carbon dioxide into two streams, which respectively absorb the exhaust heat of the cathode of the solid oxide fuel cell and the carbon dioxide turbine, thereby achieving efficient heat recycling. Under the design conditions of the present invention, when the mixing ratio of ammonia and hydrogen in the fuel is 0.5, the working efficiency of the STCC (split-flow transcritical carbon dioxide cycle) is 18.2%, the working efficiency of the solid oxide fuel cell is 68.91%, and the efficiency of the entire system is 71.6%. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of a solid fuel cell-split-flow transcritical carbon dioxide combined cycle system.

[0031] In the attached figure: 1. air compressor; 2. air reheater; 3. first self-heater; 4. solid oxide fuel cell; 5. second self-heater; 6. anode fuel mixer; 7. condenser; 8. feed compressor; 9. palladium film; 10. low-temperature heater; 11. high-temperature heater; 12. carbon dioxide turbine; 13. generator; 14. carbon dioxide reheater; 15. carbon dioxide mixer; 16. carbon dioxide separator; 17. carbon dioxide pump; 18. carbon dioxide condenser. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0033] like Figure 1 As shown, a solid fuel cell-divided transcritical carbon dioxide combined cycle system of the present invention comprises: a solid fuel cell system, a diverted transcritical carbon dioxide circulation system, and a hydrogen circulation separation device. The cathode exhaust of the solid fuel cell system is introduced into the diverted transcritical carbon dioxide circulation system to utilize the exhaust waste heat, and the anode exhaust of the solid fuel cell system is introduced into the hydrogen circulation separation device to separate and filter out the hydrogen in the anode exhaust, and introduced into the anode of the solid fuel cell system as fuel to achieve recycling.

[0034] The solid fuel cell system comprises an air compressor 1, an air regenerator 2, a first self-heater 3, a solid oxide fuel cell 4, a second self-heater 5 and an anode fuel mixer 6;

[0035] The solid oxide fuel cell 4 comprises an anode layer, an electrolyte layer, a separator layer and a cathode layer, and its fuel utilization rate is 0.6 to 0.85 and its inlet temperature is 750°C;

[0036] The power of the air compressor 1 is 425kW to 484kW. The air compressor 1 compresses the air and then preheats it to 750°C in two stages through the air reheater 2 and the first self-heater 3, and then passes it into the cathode layer. The ammonia-hydrogen mixed gas in the anode fuel mixer 6 is preheated to 750°C through the second self-heater 5 and then passed into the anode layer. The anode exhaust gas is preheated by the second self-heater 5 for the ammonia-hydrogen mixed gas, and then preheated by the air reheater 2 for one stage before entering the hydrogen circulation separation device; the cathode exhaust gas is preheated by the first self-heater 3 for two stages before entering the split-flow transcritical carbon dioxide circulation system.

[0037] Specific:

[0038] The outlet of the air compressor 1 is connected to the air inlet of the air regenerator 2, the air outlet of the air regenerator 2 is connected to the air inlet of the first self-heater 3, and the air outlet of the first self-heater 3 is connected to the cathode layer of the solid oxide fuel cell 4;

[0039] The ammonia-hydrogen mixed gas outlet in the anode fuel mixer 6 is communicated with the ammonia-hydrogen mixed gas inlet of the second self-heater 5, and the ammonia-hydrogen mixed gas outlet of the second self-heater 5 is communicated with the anode layer of the solid oxide fuel cell 4;

[0040] The heat source inlet of the first self-heater 3 is connected to the cathode exhaust port of the solid oxide fuel cell 4, and the heat source outlet of the first self-heater 3 is connected to the heat source inlet of the high temperature heater 11;

[0041] The heat source inlet of the second self-heater 5 is connected to the anode exhaust port of the solid oxide fuel cell 4, the heat source outlet of the second self-heater 5 is connected to the heat source inlet of the air heat regenerator 2, and the heat source outlet of the air heat regenerator 2 is connected to the inlet of the condenser 7.

[0042] The hydrogen circulation separation device includes a condenser 7, a feed compressor 8 and a palladium film 9, wherein: the anode exhaust (hydrogen, nitrogen, water mixed gas) is preheated as an ammonia hydrogen mixed gas by the second self-heater 5, and then preheated as air by the air reheater 2 before entering the condenser 7 for cooling and dehydration. The hydrogen and nitrogen in the anode exhaust are pressurized in the feed compressor 8 with a power of 196kW to 335kW and then passed into the palladium film 9. The palladium film 9 separates and filters out the hydrogen, and the hydrogen is passed into the anode fuel mixer 6. The anode fuel mixer 6 mixes the hydrogen from the palladium film 9 with the hydrogen and ammonia in the gas storage tank in a volume ratio of 0.3 to 0.7 for use as fuel circulation for SOFC.

[0043] The split-flow transcritical carbon dioxide circulation system includes: a low-temperature heater 10, a high-temperature heater 11, a carbon dioxide turbine 12, a generator 13, a carbon dioxide regenerator 14, a carbon dioxide mixer 15, a carbon dioxide separator 16, a carbon dioxide pump 17, and a carbon dioxide condenser 18;

[0044] The heat source inlet of the high temperature heater 11 is connected to the cathode exhaust port of the solid oxide fuel cell 4, the heat source outlet of the high temperature heater 11 is connected to the heat source inlet of the low temperature heater 10, and the heat source outlet of the low temperature heater 10 is connected to the atmosphere;

[0045] The outlet of the carbon dioxide turbine 12 is connected to the heat source inlet of the carbon dioxide regenerator 14, and the heat source outlet of the carbon dioxide regenerator 14 is connected to the inlet of the carbon dioxide condenser 18 to send the carbon dioxide after the turbine expansion work to the carbon dioxide condenser 18 for condensation. The outlet of the carbon dioxide condenser 18 is connected to the inlet of the carbon dioxide pump 17 with a power of 67kW to 101kW, and the outlet of the carbon dioxide pump 17 is connected to the inlet of the carbon dioxide separator 16 to pass the compressed carbon dioxide into the carbon dioxide separator 16. The first outlet of the carbon dioxide separator 16 is connected to the material inlet of the low-temperature heater 10, and the second outlet of the carbon dioxide separator 16 is connected to the carbon dioxide regenerator. The material inlet of the heat exchanger 14 is connected, the carbon dioxide separator 16 divides the carbon dioxide into two streams according to a distribution ratio of 0.3 to 0.7, and heats them respectively by the carbon dioxide regenerator 14 and the low-temperature heater 10; the material outlets of the low-temperature heater 10 and the carbon dioxide regenerator 14 are both connected to the inlet of the carbon dioxide mixer 15, the outlet of the carbon dioxide mixer 15 is connected to the material inlet of the high-temperature heater 11, the carbon dioxide mixer 15 mixes the two streams of carbon dioxide, and then passes them into the high-temperature heater 11 for heating, the material outlet of the high-temperature heater 11 is connected to the inlet of the carbon dioxide turbine 12, and the carbon dioxide does work in the carbon dioxide turbine 12 to drive the generator 13 to generate electricity.

[0046] It should be noted that the present invention recycles the heat released by the reaction of the solid oxide fuel cell 4 to achieve heat circulation, as follows:

[0047] The heat source inlet of the first self-heater 3 is connected to the cathode exhaust port of the SOFC for heating the air for the second time, the heat source inlet of the second self-heater 5 is connected to the anode exhaust port of the SOFC for heating the anode fuel gas for the first time, and the heat source outlet of the second self-heater 5 is connected to the heat source inlet of the air regenerator 2 for heating the air for the first time;

[0048] The heat source outlet of the second autoheater 5 is connected to the heat source inlet of the high temperature heater 11, so as to heat the carbon dioxide for the second time. The heat source outlet of the high temperature heater 11 is connected to the heat source inlet of the low temperature heater 10, so as to heat one of the separated carbon dioxide for the first time. The carbon dioxide regenerator 14 is connected to the outlet of the carbon dioxide turbine 12, so as to heat one of the separated carbon dioxide for the first time.

[0049] In order to make the purpose, technical effect and technical solution of the embodiment of the present invention clearer, the technical solution in the embodiment of the present invention is clearly and completely described below in conjunction with the drawings in the embodiment of the present invention; it is obvious that the described embodiment is a part of the embodiment of the present invention. Based on the embodiment disclosed in the present invention, other embodiments obtained by ordinary technicians in this field without making creative work should all fall within the scope of protection of the present invention.

[0050] Example

[0051] A solid fuel cell-split-flow transcritical carbon dioxide combined cycle system of the present invention comprises: a solid oxide fuel cell 4 and a split-flow transcritical carbon dioxide cycle; an ammonia-hydrogen mixed gas is introduced into the anode layer of the solid oxide fuel cell 4, and the ammonia-hydrogen mixing ratio of the mixed gas is 0 to 1.0.

[0052] Since solid oxide fuel cells 4 often use carbon-containing fuels, they may cause environmental problems, and using pure hydrogen as fuel will lead to cost and transportation problems. With the maturity of the technology of direct ammonia solid oxide fuel cells, ammonia is a good raw material for producing hydrogen, which has the advantages of easy storage and transportation and low production cost. Therefore, ammonia-hydrogen can be used as a mixed fuel.

[0053] Air is introduced into the cathode of the solid oxide fuel cell 4. The air will first be compressed by the air compressor 1, and then preheated by the air reheater 2 and the first self-heater 3 before entering the SOFC cathode; an ammonia-hydrogen mixed gas is introduced into the anode of the SOFC, and the mixed gas needs to be preheated by the second self-heater 5 before entering the anode.

[0054] In the solid oxide fuel cell 4, ammonia in the ammonia-hydrogen mixed gas heated to above 700°C is decomposed into nitrogen and hydrogen at the anode, and a portion of the hydrogen reacts with oxygen ions generated at the anode to generate water and electrons. Oxygen in the air obtains electrons from the anode to generate oxygen ions at the cathode. After the reaction, a mixed gas of hydrogen, nitrogen and water is discharged from the anode, and the air after the reaction is discharged from the cathode.

[0055] The anode outlet of the solid oxide fuel cell 4 is connected to the heat source inlet of the second self-heater 5, which is used as the heat source for heating the anode ammonia-hydrogen mixed gas. The heat source outlet of the second self-heater 5 is connected to the heat source inlet of the air regenerator 2, which is used as the heat source for the first heating of the cathode air. The heat source outlet of the air regenerator 2 is connected to the inlet of the condenser 7. The cathode outlet of the solid oxide fuel cell 4 is connected to the heat source inlet of the high temperature heater 11, which is used as the heat source of the high temperature heater 11 of the transcritical carbon dioxide cycle to heat the carbon dioxide for the second time. The heat source outlet of the high temperature heater 11 is connected to the heat source inlet of the low temperature heater 10, which is used to heat a part of the carbon dioxide in the transcritical carbon dioxide cycle for the first time.

[0056] The products of the anode reaction, hydrogen, nitrogen and water, pass through the above-mentioned second autoheater 5 and air reheater 2, and are condensed by the condenser 7 to remove the water. The remaining hydrogen and nitrogen are passed into the palladium film 9 through the feed compressor 8. The palladium film 9 separates the nitrogen and hydrogen. The hydrogen therein will be recycled and mixed with the hydrogen and ammonia gas in the storage tank through the anode fuel mixer 6 to be used as the anode fuel again.

[0057] The carbon dioxide in the transcritical carbon dioxide cycle will first be cooled by the carbon dioxide condenser 18, and then passed into the carbon dioxide separator 16 through the carbon dioxide pump 17. The carbon dioxide separator 16 divides the carbon dioxide into two streams for heating respectively, one stream is heated in the low-temperature heater 10, and the other stream is heated in the carbon dioxide regenerator 14. The heated carbon dioxide is mixed and sent to the high-temperature heater 11 for heating. The material outlet of the high-temperature heater 11 is connected to the carbon dioxide turbine 12 for power generation. The carbon dioxide turbine 12 is connected to the heat source inlet of the carbon dioxide regenerator 14 and is used as the heat source of the carbon dioxide regenerator 14 to heat the separated carbon dioxide for the first time. The heat source outlet of the carbon dioxide regenerator 14 is connected to the carbon dioxide condenser 18, forming a carbon dioxide cycle.

[0058] In the process embodiment of the present invention, the working process includes:

[0059] Air enters the cathode of SOFC: air passes through the air compressor 1 with a power of 484kW from the ambient state (101kPa, 25°C). After passing through the air compressor 1, the air rises to 339°C. In the process of passing through the air regenerator 2, the air absorbs heat from the anode exhaust and is heated to 436°C. In the process of passing through the first self-heater 3, the air absorbs heat from the cathode exhaust and is heated to 750°C, and then enters the cathode of SOFC;

[0060] The fuel gas enters the anode of the SOFC: the fuel gas ammonia is mixed with the hydrogen from the palladium film 9 from the gas tank (exemplarily, the temperature is 25°C, the gas flow rate is 0.5373, and the pressure is 151.9 kPa), and is heated by the second self-heater 5 using the exhaust gas from the anode, and the temperature rises to 750°C (exemplarily, the gas flow rate is 0.6005, and the pressure is 151.9 kPa), and then enters the anode of the SOFC.

[0061] The electrochemical reaction process of the solid oxide fuel cell 4 generates heat, part of which is used to decompose ammonia, and the other part of which is used to heat the generated gas and unreacted gas, so the temperature at the SOFC outlet will be higher than that at the inlet.

[0062] In the present invention, the working process of SOFC is divided into two parts, the first part is the decomposition of ammonia, and the second part is the electrochemical reaction of ammonia and hydrogen:

[0063]

[0064] The exemplary SOFC operating temperature is 750°C, and ammonia is completely decomposed under the catalytic action of the anode material Ni-YSZ (nickel-yttria doped zirconia). The fuel utilization factor is assumed to be 0.6.

[0065] In the exemplary embodiment of the present invention, the anode layer material of SOFC is Ni-Y 2 O 3 Doped ZrO 2 (Ni-YSZ), the cathode layer material is LSCF-CGO, and the electrolyte layer material is YSZ.

[0066] The air regenerator 2 part of the embodiment of the present invention: the cathode exothermic reaction of the solid oxide fuel cell 4 produces a mixture of nitrogen and oxygen (the exemplary temperature is 825.29°C, the gas flow rate is 8.5433, and the pressure is 131.9kPa). After the air is preheated for the second time by the first self-heater 3, the temperature of the mixed gas is 177.51°C (the exemplary gas flow rate is 8.5433 and the pressure is 121.9kPa). After the carbon dioxide is heated for the second time by the high-temperature heater 11, the temperature of the mixed gas is 109.23°C (the exemplary gas flow rate is 8.5433 and the pressure is 111.9kPa). After the part of the carbon dioxide is heated for the first time by the low-temperature heater 10, the temperature of the mixed gas is 70.15°C (the exemplary gas flow rate is 8.5433 and the pressure is 101.9kPa). Finally, the mixed gas is discharged into the atmosphere. The solid oxide fuel cell 4 generates a mixture of hydrogen, nitrogen and water vapor after the anode reaction (exemplary temperature is 825.29°C, gas flow rate is 1.3649, and pressure is 131.9 kPa). The mixed gas is preheated for the first time in the second self-heater 5 to the fuel gas introduced, and the temperature is 350.00°C (exemplary gas flow rate is 1.3649, and pressure is 121.9 kPa). The air is then preheated for the first time in the air regenerator 2, and the temperature is then 118.75°C (exemplary gas flow rate is 1.3649, and pressure is 111.9 kPa). The mixed gas passes through the condenser After cooling in 7, it is cooled to 20.00℃ (exemplary gas flow rate is 0.0632, pressure is 101.9kPa), in which water is separated, and then the mixed gas passes through the feed compressor 8, is compressed into compressed gas (exemplary temperature is 263.06℃, gas flow rate is 0.0632, pressure is 607.4kPa), and then the compressed gas is passed into the palladium membrane 9 for separation, and nitrogen is separated. The outlet of the palladium membrane 9 is hydrogen mixed with the fuel gas from the gas tank (exemplary temperature is 122.66℃, gas flow rate is 0.6005, pressure is 151.9kPa), and then passed into the anode again.

[0067] Separation type carbon dioxide circulation part of the embodiment of the present invention: After the carbon dioxide (exemplary temperature is 20.00°C, gas flow rate is 3.6875, and pressure is 572.9kPa) is compressed by the carbon dioxide pump 17, the compressed carbon dioxide gas (exemplary temperature is 34.39°C, gas flow rate is 3.6875, and pressure is 1519.9kPa) enters the carbon dioxide separator 16, and the exemplary separation ratio is 0.5. After that, a part of the separated carbon dioxide is heated to 98.01°C (exemplary gas flow rate is 1.8438, and pressure is 1518.9kPa) by the low temperature heater 10, and the other part is heated to 96.01°C (exemplary gas flow rate is 1.8438, and pressure is 1518.9kPa) by the carbon dioxide regenerator 14, and then the two parts of carbon dioxide are mixed in the carbon dioxide mixer 15 (exemplary temperature is 20.00°C, gas flow rate is 3.6875, and pressure is 572.9kPa). 97.18℃, gas flow rate is 3.6875, pressure is 1518.9kPa), after mixing, it is passed into the high temperature heater 11 to be heated to 202.58℃ (exemplary gas flow rate is 3.6875, pressure is 1517.9kPa), and then enters the carbon dioxide turbine 12 to power the generator 13. The temperature of carbon dioxide discharged from the carbon dioxide turbine 12 is 119.36℃ (exemplary gas flow rate is 3.6875, pressure is 574.91kPa), and then the carbon dioxide discharged from the carbon dioxide turbine 12 passes through the carbon dioxide regenerator 14 to heat a part of the separated carbon dioxide, and the temperature of the discharged carbon dioxide is reduced to 47.20℃ (exemplary gas flow rate is 3.6875, pressure is 573.91kPa) after passing through the carbon dioxide regenerator 14, and is cooled by the carbon dioxide condenser 18 and then passed into the carbon dioxide pump 17 for circulation again.

[0068] In summary, the embodiment of the present invention discloses a solid fuel cell-divided flow transcritical carbon dioxide combined cycle system, including a SOFC fuel cell part and a transcritical carbon dioxide cycle part. After being preheated, the ammonia hydrogen mixed fuel enters the anode of the SOFC to react electrochemically with the heated and compressed air from the cathode and discharge. The discharge process also generates heat, which is passed through the air regenerator 2 and two self-heaters to heat the ammonia hydrogen fuel and air. The gas after the anode reaction can be separated from the hydrogen in the fuel again after cooling by the condenser 7 and separation by the palladium film 9 and recycled as the anode fuel of the solid oxide fuel cell 4. At the same time, the gas after the cathode reaction can heat part of the carbon dioxide in the transcritical carbon dioxide cycle, thereby improving the utilization rate of heat. Since the circulation system uses ammonia and hydrogen as fuel, the combined cycle system meets the requirements of high power density and environmental protection. Under the design conditions, when the system is fed with a mixed fuel of 50% ammonia / 50% hydrogen, the current density is 2000A / m 2The system was able to achieve a power output of 7163 kW and a system efficiency of 71.6%, while the output power of the solid oxide fuel cell 4 was 6891 kW and the efficiency was 68.9%, and the output power of the split-flow transcritical carbon dioxide cycle was 273 kW and the efficiency was 18.2%.

[0069] The present invention discloses a solid fuel cell-divided flow transcritical carbon dioxide combined cycle system, which adopts ammonia hydrogen mixed gas as fuel of solid oxide fuel cell 4, wherein ammonia hydrogen mixed gas at 750°C heated by a second self-heater 5 is introduced into the anode, and air at 750°C heated by an air regenerator 2 and a self-heater is introduced into the cathode; waste gas generated by the anode of solid oxide fuel cell 4 can be obtained after water cooling by a condenser 7 and separation by a palladium film 9, and hydrogen can be recycled and reused as fuel of solid oxide fuel cell 4; waste gas generated by the cathode of solid oxide fuel cell 4 is heated by air by a first self-heater 3, and is heated by a low-temperature heater 10 and a high-temperature heater 11 for carbon dioxide working medium in a separated transcritical carbon dioxide cycle; waste gas generated by the anode is heated by ammonia hydrogen mixed fuel gas by a second self-heater 5, thereby realizing a thermal cycle. Carbon dioxide circulation technology is currently considered as a means to improve the efficiency of SOFC. It utilizes a split-flow transcritical carbon dioxide cycle, which divides the carbon dioxide working fluid into two streams. One stream absorbs the heat of the SOFC cathode exhaust for heating, and the other stream absorbs the outlet heat of the carbon dioxide turbine 12. The two streams of carbon dioxide are combined through a mixer and absorb the heat of the SOFC cathode exhaust again. Subsequently, the carbon dioxide is used to generate electricity through the carbon dioxide turbine 12, thereby realizing further utilization of the heat of the SOFC exhaust.

[0070] In terms of SOFC fuel, although fossil fuels are currently widely used in SOFC, ammonia and hydrogen as new fuels have the advantages of being green and environmentally friendly. In the present invention, considering the storage and transportation of hydrogen, ammonia and hydrogen are used as mixed fuels, and the mixing ratio of ammonia and hydrogen can be adjusted arbitrarily, which has the advantages of flexibility and safety.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art can still modify or make equivalent substitutions to the specific implementations of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A solid fuel cell-split-flow transcritical carbon dioxide combined cycle system, characterized in that: The invention comprises a solid fuel cell system, a split-flow transcritical carbon dioxide circulation system and a hydrogen circulation separation device. The solid fuel cell system comprises a solid oxide fuel cell (4) using ammonia-hydrogen mixed gas as fuel. The cathode exhaust port of the solid oxide fuel cell (4) is connected to the inlet of the split-flow transcritical carbon dioxide circulation system to heat the carbon dioxide using the waste heat of the exhaust gas. The anode exhaust port of the solid oxide fuel cell (4) is connected to the inlet of the hydrogen circulation separation device, and the outlet of the hydrogen circulation separation device is connected to the anode layer of the solid oxide fuel cell (4).

2. A solid fuel cell-split-flow transcritical carbon dioxide combined cycle system according to claim 1, characterized in that: The solid fuel cell system further comprises an air compressor (1), an air regenerator (2), a first self-heater (3), a second self-heater (5) and an anode fuel mixer (6), wherein: The outlet of the air compressor (1) is connected to the air inlet of the air regenerator (2), the air outlet of the air regenerator (2) is connected to the air inlet of the first self-heater (3), and the air outlet of the first self-heater (3) is connected to the cathode layer of the solid oxide fuel cell (4); The ammonia-hydrogen mixed gas outlet in the anode fuel mixer (6) is connected to the ammonia-hydrogen mixed gas inlet of the second autoheater (5), and the ammonia-hydrogen mixed gas outlet of the second autoheater (5) is connected to the anode layer of the solid oxide fuel cell (4); The heat source inlet of the first self-heater (3) is connected to the cathode exhaust port of the solid oxide fuel cell (4), and the heat source outlet of the first self-heater (3) is connected to the heat source inlet of the split-flow transcritical carbon dioxide circulation system; The heat source inlet of the second self-heater (5) is connected to the anode exhaust port of the solid oxide fuel cell (4), the heat source outlet of the second self-heater (5) is connected to the heat source inlet of the air heat regenerator (2), and the heat source outlet of the air heat regenerator (2) is connected to the inlet of the hydrogen circulation separation device.

3. A solid fuel cell-split-flow transcritical carbon dioxide combined cycle system according to claim 2, characterized in that: The inlet of the anode fuel mixer (6) is connected to the outlet of the hydrogen storage tank, the outlet of the ammonia storage tank and the outlet of the hydrogen circulation separation device. The hydrogen and ammonia are mixed in the anode fuel mixer (6) at a volume ratio of 0.3 to 0.

7.

4. A solid fuel cell-split-flow transcritical carbon dioxide combined cycle system according to claim 1, characterized in that: The hydrogen circulation separation device comprises a condenser (7), a feed compressor (8) and a palladium film (9); the anode exhaust gas of the solid fuel cell system is introduced into the inlet of the condenser (7) after two heat exchanges; the gas outlet of the condenser (7) is connected to the inlet of the feed compressor (8); the outlet of the feed compressor (8) is connected to the inlet of the palladium film (9) for separating and filtering out hydrogen in the anode exhaust gas and introducing the hydrogen into the solid fuel cell system.

5. A solid fuel cell-split-flow transcritical carbon dioxide combined cycle system according to claim 2, characterized in that: The hydrogen circulation separation device comprises a condenser (7), a feed compressor (8) and a palladium film (9); the heat source outlet of the air regenerator (2) is connected to the inlet of the condenser (7); the gas outlet of the condenser (7) is connected to the inlet of the feed compressor (8); the outlet of the feed compressor (8) is connected to the palladium film (9); and the outlet of the palladium film (9) is connected to the inlet of the anode fuel mixer (6).

6. A solid fuel cell-split-flow transcritical carbon dioxide combined cycle system according to claim 1, characterized in that: The split-flow transcritical carbon dioxide circulation system comprises: a low-temperature heater (10), a high-temperature heater (11), a carbon dioxide turbine (12), a generator (13), a carbon dioxide regenerator (14), a carbon dioxide mixer (15), a carbon dioxide separator (16), a carbon dioxide pump (17), and a carbon dioxide condenser (18); the cathode exhaust of the solid fuel cell system is introduced into the heat source inlet of the high-temperature heater (11) after primary heat exchange; the heat source outlet of the high-temperature heater (11) is connected to the heat source inlet of the low-temperature heater (10); and the heat source outlet of the low-temperature heater (10) is connected to the atmosphere; The outlet of the carbon dioxide turbine (12) is connected to the heat source inlet of the carbon dioxide regenerator (14), the heat source outlet of the carbon dioxide regenerator (14) is connected to the inlet of the carbon dioxide condenser (18), the outlet of the carbon dioxide condenser (18) is connected to the inlet of the carbon dioxide pump (17), the outlet of the carbon dioxide pump (17) is connected to the inlet of the carbon dioxide separator (16) for separating the carbon dioxide into two streams, the first outlet of the carbon dioxide separator (16) is connected to the material inlet of the low-temperature heater (10), the second outlet of the carbon dioxide separator (16) is connected to the material inlet of the carbon dioxide regenerator (14), the material outlets of the low-temperature heater (10) and the carbon dioxide regenerator (14) are both connected to the inlet of the carbon dioxide mixer (15), the outlet of the carbon dioxide mixer (15) is connected to the material inlet of the high-temperature heater (11), and the material outlet of the high-temperature heater (11) is connected to the inlet of the carbon dioxide turbine (12).

7. A solid fuel cell-split-flow transcritical carbon dioxide combined cycle system according to claim 5, characterized in that: The split-flow transcritical carbon dioxide circulation system comprises: a low-temperature heater (10), a high-temperature heater (11), a carbon dioxide turbine (12), a generator (13), a carbon dioxide regenerator (14), a carbon dioxide mixer (15), a carbon dioxide separator (16), a carbon dioxide pump (17), and a carbon dioxide condenser (18); a heat source outlet of the first self-heater (3) is connected to a heat source inlet of the high-temperature heater (11), a heat source outlet of the high-temperature heater (11) is connected to a heat source inlet of the low-temperature heater (10), and a heat source outlet of the low-temperature heater (10) is connected to the atmosphere; The outlet of the carbon dioxide turbine (12) is connected to the heat source inlet of the carbon dioxide regenerator (14), the heat source outlet of the carbon dioxide regenerator (14) is connected to the inlet of the carbon dioxide condenser (18), the outlet of the carbon dioxide condenser (18) is connected to the inlet of the carbon dioxide pump (17), the outlet of the carbon dioxide pump (17) is connected to the inlet of the carbon dioxide separator (16) for separating the carbon dioxide into two streams, the first outlet of the carbon dioxide separator (16) is connected to the material inlet of the low-temperature heater (10), the second outlet of the carbon dioxide separator (16) is connected to the material inlet of the carbon dioxide regenerator (14), the material outlets of the low-temperature heater (10) and the carbon dioxide regenerator (14) are both connected to the inlet of the carbon dioxide mixer (15), the outlet of the carbon dioxide mixer (15) is connected to the material inlet of the high-temperature heater (11), and the material outlet of the high-temperature heater (11) is connected to the inlet of the carbon dioxide turbine (12).

8. A solid fuel cell-split-flow transcritical carbon dioxide combined cycle system according to claim 6 or 7, characterized in that: In the carbon dioxide separator (16), carbon dioxide is divided into two streams according to a distribution ratio of 0.3 to 0.

7.

9. The solid fuel cell-split-flow transcritical carbon dioxide combined cycle system according to claim 1, characterized in that: The fuel utilization rate of the solid oxide fuel cell (4) is 0.6-0.85, and the inlet temperature is 750°C.

10. The solid fuel cell-split-flow transcritical carbon dioxide combined cycle system according to claim 7, characterized in that: The power of the air compressor (1) is 425 kW to 484 kW, the power of the feed compressor (8) is 196 kW to 335 kW, and the power of the carbon dioxide pump (17) is 67 kW to 101 kW.

Images