Gas-electricity cogeneration system based on lng and solid oxide fuel cell and control method

Abstract

The application relates to a gas-electricity combined supply system and a control method based on LNG and a solid oxide fuel cell, the system comprising a cold energy primary utilization device and a solid oxide fuel cell, the cold energy primary utilization device being connected with an LNG storage device and a rewarming device, the rewarming device and an anode gas inlet of an electric pile of the solid oxide fuel cell being sequentially connected with a condensing heat exchanger, a reformer and a first heat exchanger, an anode exhaust port of the electric pile of the solid oxide fuel cell being sequentially connected with the condensing heat exchanger, a water removal device, an LNG-CO2 condensation device and a CO2 collection device, the LNG-CO2 condensation device being connected with the cold energy primary utilization device and the rewarming device, a cathode gas inlet of the electric pile of the solid oxide fuel cell being sequentially connected with a second heat exchanger and an air compressor, and a cathode exhaust port of the electric pile of the solid oxide fuel cell being sequentially connected with the first heat exchanger and a tail gas combustor, and the system has the advantages of simple structure, convenient control, safety and reliability; the control method has the advantages of simple flow and high working efficiency.

Description

Technical Field

[0001] This invention relates to an energy supply system, specifically to a combined gas and power system based on LNG and solid oxide fuel cells, and a control method for the system. Background Technology

[0002] Natural gas solid oxide fuel cells (SOCFCs) are a promising, environmentally friendly, and efficient energy supply device. They generate electricity through electrochemical reactions, and the flue gas produced after the reaction can be recovered as heat. Although SOCFCs reduce carbon dioxide emissions per unit of electricity generated by improving energy efficiency, the use of natural gas still produces a certain amount of carbon dioxide emissions. This necessitates the use of carbon capture methods to treat the exhaust gas and recover carbon dioxide. Currently, the main approach in this field is to add pure oxygen to the anode exhaust gas for mixing and combustion to increase the carbon dioxide concentration, followed by carbon dioxide capture. However, this method is costly because oxygen needs to be prepared or purchased separately. Another approach utilizes a combustion reforming heat exchanger and achieves a reforming reaction of methane and water through chemical looping combustion. This converts unreacted carbon monoxide and hydrogen in the anode exhaust gas of the fuel cell stack into carbon dioxide and water, increasing the carbon dioxide concentration in the anode exhaust gas, followed by carbon dioxide capture. The internal heat balance of a SOCFC is itself a complex control system, and the channel switching control within the combustion reforming heat exchanger further increases the complexity of the control system and the difficulty of actual operation. Summary of the Invention

[0003] The purpose of this invention is to provide a combined gas and power system and control method based on LNG and solid oxide fuel cells. The system has the advantages of simple structure, convenient operation, high energy utilization, and safety and reliability; the method has the advantages of simple process and high working efficiency.

[0004] To address the aforementioned problems in the prior art, this invention provides a combined gas and power system based on LNG and a solid oxide fuel cell, comprising a primary cold energy utilization unit and a solid oxide fuel cell. The input port of the primary cold energy utilization unit is connected to an LNG storage device. The output port of the primary cold energy utilization unit is connected to a reheating device via a preheating pipeline equipped with a first control valve. A condensing heat exchanger, a reformer, and a first heat exchanger are sequentially connected between the output port of the reheating device and the anode inlet of the solid oxide fuel cell stack via an anode gas supply pipeline. The anode gas supply pipeline between the reheating device and the condensing heat exchanger is connected to a gas pipeline leading to a natural gas user. The anode exhaust port of the solid oxide fuel cell stack is connected to a condensing heat exchanger via an anode exhaust pipeline, and then sequentially connected to a water removal device, an LNG-CO2 sublimation device, and a CO2 collection device. The heat exchanger is connected to the vaporizer via a condensate pipe. The vaporizer is connected to the reformer via a steam pipe. The LNG-CO2 sublimation unit is connected to the output port of the cold energy primary utilization unit and the input port of the reheating unit via sublimation inlet and outlet pipes, respectively. A second control valve is installed on the sublimation inlet pipe. The LNG-CO2 sublimation unit is connected to the tail gas burner via a tail gas pipe. The tail gas burner is connected to the vaporizer via a first high-temperature flue gas pipe. The cathode inlet of the solid oxide fuel cell stack is connected to a second heat exchanger and an air compressor in sequence via a cathode supply pipe. The second heat exchanger is connected to the tail gas burner via a second high-temperature flue gas pipe. The cathode exhaust port of the solid oxide fuel cell stack is connected to the first heat exchanger and the tail gas burner in sequence via a cathode exhaust pipe. The electrical energy generated by the solid oxide fuel cell is transmitted to the electricity user through the power supply line.

[0005] Furthermore, the present invention provides a combined gas and power system based on LNG and solid oxide fuel cells, which further includes a third heat exchanger. A first waste gas pipeline is provided between the third heat exchanger and the vaporizer. The first waste gas pipeline is connected to a first high-temperature flue gas pipeline through the heating channel of the vaporizer. The first waste gas pipeline is connected to a second heat exchanger through a second waste gas pipeline. The second waste gas pipeline is connected to a second high-temperature flue gas pipeline through the heat exchange channel of the second heat exchanger. A circulation loop is provided between the third heat exchanger and the reheating device, and a working medium is provided in the circulation loop.

[0006] Furthermore, the present invention provides a combined gas and power system based on LNG and solid oxide fuel cells, wherein the condenser heat exchanger is used to exchange heat between the incoming natural gas and the anode exhaust, and to deliver the generated condensate to the vaporizer; the LNG-CO2 sublimation device is used to exchange heat between the incoming natural gas and the anode exhaust, and to deliver the CO2 formed after the anode exhaust sublimation and the anode tail gas to the CO2 collection device and the tail gas burner respectively.

[0007] Furthermore, the present invention provides a combined gas and power system based on LNG and solid oxide fuel cells, wherein the reheating device is used to heat the flowing natural gas, the reformer is used to reform the incoming natural gas and water vapor, and the carbon monoxide and hydrogen generated by the reforming reaction are transported to the first heat exchanger through the anode gas supply pipeline.

[0008] Furthermore, the present invention provides a combined gas and power system based on LNG and solid oxide fuel cells, wherein the dehydration device is used to remove moisture from the anode exhaust, the CO2 collection device is used to collect CO2 obtained by condensing the anode exhaust through the LNG-CO2 sublimation device, and the air compressor is used to compress air.

[0009] Furthermore, the present invention provides a combined gas and power system based on LNG and solid oxide fuel cells, wherein the vaporizer is used to vaporize water and transport the generated water vapor to the reformer through a steam pipeline, and the exhaust gas burner is used to burn the incoming anode exhaust gas and cathode exhaust gas, and transport the generated high-temperature flue gas to the vaporizer and the second heat exchanger respectively through a first high-temperature flue gas pipeline and a second high-temperature flue gas pipeline.

[0010] Furthermore, the present invention provides a combined gas and power system based on LNG and solid oxide fuel cells, wherein the first heat exchanger is used to exchange heat between the introduced natural gas or reformed gas and the cathode exhaust gas, the second heat exchanger is used to exchange heat between the introduced air and the high-temperature flue gas, and the third heat exchanger is used to exchange heat between the introduced waste gas and the working medium.

[0011] Based on the same concept, the present invention also provides a control method for the above-mentioned combined gas and power system, comprising the following steps:

[0012] S1. Close the second control valve and open the first control valve. After being processed by the cold energy primary utilization unit, the LNG is converted into gaseous natural gas. The natural gas enters the reheating unit and is heated. It then flows sequentially through the condenser heat exchanger, reformer, first heat exchanger, solid oxide fuel cell stack anode, condenser heat exchanger, water removal device, and LNG-CO2 sublimation device before entering the tail gas burner. The air is compressed and flows sequentially through the second heat exchanger, solid oxide fuel cell stack cathode, and first heat exchanger before entering the tail gas burner.

[0013] S2. Natural gas and air are mixed and burned in the exhaust gas burner. The high-temperature flue gas produced by combustion is delivered to the vaporizer and the second heat exchanger respectively through the first high-temperature flue gas pipeline and the second high-temperature flue gas pipeline. Water in the vaporizer is heated into water vapor by the high-temperature flue gas. The water vapor enters the reformer and undergoes a reforming reaction with the flowing natural gas. The mixed gas generated after the reforming reaction is heated when it flows through the anode of the solid oxide fuel cell stack. The high-temperature flue gas in the second heat exchanger exchanges heat with the air. The heated air flows through the cathode of the solid oxide fuel cell stack and is heated.

[0014] S3. When the solid oxide fuel cell stack temperature reaches 600℃, the first control valve is closed and the second control valve is opened. LNG is processed by the cold energy primary utilization device and converted into gaseous natural gas. The natural gas flows through the LNG-CO2 sublimation device and then enters the reheating device. After being heated by the reheating device, part of the natural gas is transported to natural gas users through the gas pipeline, and part flows through the condensation heat exchanger and then enters the reformer to undergo a reforming reaction with water vapor from the vaporizer. The mixed gas generated by the reforming reaction flows through the first heat exchanger and then enters the anode of the solid oxide fuel cell stack. The air is compressed and flows through the second heat exchanger and then enters the cathode of the solid oxide fuel cell stack. The solid oxide fuel cell stack generates electricity through an electrochemical reaction and transmits the generated electricity to users through the power supply line. The anode exhaust generated by power generation flows through the condensation heat exchanger and the dehydration device and then enters the LNG-CO2 sublimation device. The cathode exhaust generated by power generation flows through the first heat exchanger and then enters the tail gas burner.

[0015] S4. The natural gas flowing through the condenser heat exchanger exchanges heat with the anode exhaust gas and delivers the generated condensate to the vaporizer. The dewatering device removes water from the flowing anode exhaust gas. The LNG-CO2 sublimation device exchanges heat with the flowing natural gas and the anode exhaust gas and delivers the CO2 formed after the anode exhaust gas sublimation and the anode tail gas to the CO2 collection device and the tail gas burner respectively.

[0016] S5. The anode exhaust gas and cathode exhaust gas entering the exhaust gas burner are mixed and burned. The high-temperature flue gas generated by the combustion is delivered to the vaporizer and the second heat exchanger respectively through the first high-temperature flue gas pipeline and the second high-temperature flue gas pipeline. The high-temperature flue gas entering the vaporizer turns water into water vapor and is delivered to the reformer. The high-temperature flue gas entering the second heat exchanger exchanges heat with the air.

[0017] S6. The high-temperature flue gas entering the vaporizer vaporizes the water and becomes waste gas. It then enters the third heat exchanger through the first waste gas pipeline. The waste gas exchanges heat with the working medium in the third heat exchanger and is then discharged. The working medium absorbs heat and transfers the heat to the reheating device through the circulation loop to heat the natural gas. The high-temperature flue gas entering the second heat exchanger heats the air and also becomes waste gas. It then merges into the first waste gas pipeline through the second waste gas pipeline.

[0018] Compared with existing technologies, the present invention provides a combined gas and power system and control method based on LNG and solid oxide fuel cells, which has the following advantages: The present invention sets up a primary cold energy utilization device and a solid oxide fuel cell. The input port of the primary cold energy utilization device is connected to an LNG storage device. The output port of the primary cold energy utilization device is connected to a reheating device through a preheating pipeline equipped with a first control valve. A condensing heat exchanger, a reformer, and a first heat exchanger are sequentially connected between the output port of the reheating device and the anode inlet of the solid oxide fuel cell stack through an anode gas supply pipeline. The anode gas supply pipeline between the reheating device and the condensing heat exchanger is connected to a gas pipeline leading to a natural gas user. The anode exhaust port of the solid oxide fuel cell stack is connected to the condensing heat exchanger through an anode exhaust pipeline, and then sequentially connected to a water removal device, an LNG-CO2 sublimation device, and a CO2 collection device. The condenser heat exchanger is connected to the vaporizer via a condensate water pipe. The vaporizer is connected to the reformer via a steam pipe. The LNG-CO2 sublimation unit is connected to the output port of the primary cold energy utilization unit and the input port of the reheating unit via sublimation inlet and outlet pipes, respectively. A second control valve is installed on the sublimation inlet pipe. The LNG-CO2 sublimation unit is connected to the tail gas burner via a tail gas pipe. The tail gas burner is connected to the vaporizer via a first high-temperature flue gas pipe. The cathode inlet of the solid oxide fuel cell stack is connected to the second heat exchanger and the air compressor in sequence via the cathode gas supply pipe. The second heat exchanger is connected to the tail gas burner via the second high-temperature flue gas pipe. The cathode exhaust port of the solid oxide fuel cell stack is connected to the first heat exchanger and the tail gas burner in sequence via the cathode exhaust pipe. The electricity generated by the solid oxide fuel cell is transmitted to the electricity user through the power supply line.This constitutes a simple, easy-to-operate, energy-efficient, safe, and reliable combined gas-power system based on LNG and solid oxide fuel cells. In practical applications, because the solid oxide fuel cell stack temperature needs to reach above 600℃ to start generating electricity, the solid oxide fuel cell needs to be preheated before power generation: the second control valve is closed, the first control valve is opened, and LNG is processed into gaseous natural gas after being processed by the cold energy primary utilization device. The natural gas enters the reheating device and is heated, then flows sequentially through the condenser heat exchanger, reformer, first heat exchanger, solid oxide fuel cell stack anode, condenser heat exchanger, water removal device, and LNG-CO2 sublimation device before entering the exhaust gas burner. At the same time, air is compressed and flows sequentially through the second heat exchanger, The cathode of the solid oxide fuel cell stack and the first heat exchanger enter the exhaust gas burner. Natural gas and air are mixed and burned in the exhaust gas burner. The high-temperature flue gas generated by the combustion is delivered to the vaporizer and the second heat exchanger respectively through the first high-temperature flue gas pipeline and the second high-temperature flue gas pipeline. Water in the vaporizer is heated into water vapor by the high-temperature flue gas. The water vapor enters the reformer and undergoes a reforming reaction with the flowing natural gas. The mixed gas generated after the reforming reaction is heated when it flows through the anode of the solid oxide fuel cell stack. The high-temperature flue gas in the second heat exchanger exchanges heat with the air. The heated air flows through the cathode of the solid oxide fuel cell stack and is heated. Through the above steps, the solid oxide fuel cell can be cyclically heated and heated. When the solid oxide fuel cell stack temperature reaches above 600℃, it can generate electricity and supply gas normally: the first control valve is closed and the second control valve is opened. LNG is processed into gaseous natural gas by the cold energy primary utilization device. The natural gas flows through the LNG-CO2 sublimation device and then enters the reheating device. After being heated by the reheating device, part of the natural gas is transported to natural gas users through the gas pipeline, and part flows through the condensation heat exchanger and then enters the reformer to undergo a reforming reaction with water vapor from the vaporizer. The mixed gas generated by the reforming reaction flows through the first heat exchanger and then enters the anode of the solid oxide fuel cell stack. The air is compressed and flows through the second heat exchanger and then enters the cathode of the solid oxide fuel cell stack. The solid oxide fuel cell stack generates electricity through electrochemical reaction and transmits the generated electricity to users through the power supply line.This invention establishes a combined gas-power system based on LNG and a solid oxide fuel cell. It utilizes low-temperature natural gas (around -100°C) processed by a primary cold energy utilization device to capture and purify high-concentration carbon dioxide (over 50%) in the anode exhaust of the solid oxide fuel cell after condensation and dehydration. This not only achieves the tiered utilization of LNG cold energy, effectively improving cold energy utilization efficiency, but also realizes the capture and purification of carbon dioxide in the anode exhaust of the solid oxide fuel cell. Furthermore, this invention fully utilizes the still low temperature of the natural gas after gasification, exchanging heat between the low-temperature natural gas entering the solid oxide fuel cell and the anode exhaust (containing a large amount of carbon dioxide, water vapor, and small amounts of carbon monoxide and hydrogen) in a condenser heat exchanger. The invention recovers condensate from the anode exhaust gas by cooling the gas. On the one hand, the condensate is vaporized in the vaporizer and used for the reforming reaction, reducing the need for external water supply. On the other hand, the water in the anode exhaust gas increases the concentration of carbon dioxide after condensation and separation, which is beneficial to improving the capture and purification efficiency and reducing costs. The invention mixes and burns the anode tail gas (containing unreacted carbon monoxide and hydrogen) formed after carbon dioxide capture and separation of the anode exhaust gas with the cathode exhaust gas in the tail gas burner. The high-temperature flue gas generated by the combustion is supplied to the vaporizer and the second heat exchanger respectively. While maintaining the temperature required for the stack reaction of the solid oxide fuel cell, the invention achieves both the capture and separation of carbon dioxide and the combustion of non-condensable combustible gases, ensuring the safety of the exhaust gas.

[0019] The following detailed description, in conjunction with the accompanying drawings, illustrates a combined gas-power system and control method based on LNG and solid oxide fuel cells according to the present invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a combined gas and power system based on LNG and solid oxide fuel cells according to the present invention. Detailed Implementation

[0021] First, it should be noted that the directional terms such as up, down, left, right, front, and back used in this invention are merely descriptions based on the accompanying drawings for ease of understanding, and are not intended to limit the technical solution or the scope of protection claimed in this invention.

[0022] like Figure 1The present invention illustrates a specific embodiment of a combined gas and power system based on LNG and a solid oxide fuel cell, comprising a primary cold energy utilization device 1 and a solid oxide fuel cell 2. The input port of the primary cold energy utilization device 1 is connected to an LNG storage device. The output port of the primary cold energy utilization device 1 is connected to a reheating device 3 via a preheating pipeline equipped with a first control valve. A condensing heat exchanger 4, a reformer 5, and a first heat exchanger 6 are sequentially connected between the output port of the reheating device 3 and the anode inlet of the solid oxide fuel cell 2 via an anode gas supply pipeline. The anode gas supply pipeline between the reheating device 3 and the condensing heat exchanger 4 is connected to a gas pipeline leading to a natural gas user. The anode exhaust port of the solid oxide fuel cell 2 is connected to the condenser heat exchanger 4 via the anode exhaust pipe, and then sequentially connected to the water removal device 7, the LNG-CO2 sublimation device 8, and the CO2 collection device 9. The condenser heat exchanger 4 is connected to the vaporizer 10 via the condensate pipe, and the vaporizer 10 is connected to the reformer 5 via the steam pipe. The LNG-CO2 sublimation device 8 is connected to the output port of the cold energy primary utilization device 1 and the input port of the reheating device 3 via the sublimation inlet pipe and the sublimation outlet pipe, respectively. A second control valve is provided on the sublimation inlet pipe. The LNG-CO2 sublimation device 8 is connected to the tail gas burner 11 via the tail gas pipe, and the tail gas burner 11 is connected to the vaporizer 10 via the first high-temperature flue gas pipe. The cathode inlet of the solid oxide fuel cell 2 is connected sequentially to the second heat exchanger 12 and the air compressor 13 via a cathode gas supply line. The second heat exchanger 12 is connected to the exhaust gas burner 11 via a second high-temperature flue gas line. The cathode exhaust outlet of the solid oxide fuel cell 2 is connected sequentially to the first heat exchanger 6 and the exhaust gas burner 11 via a cathode exhaust line. The electrical energy generated by the solid oxide fuel cell 2 is supplied to electricity users through power lines. In practical applications, to improve the energy efficiency ratio and reduce energy consumption, the present invention also provides a third heat exchanger 14 to achieve heat recovery. The third heat exchanger 14 is connected to the vaporizer 10 via a first waste gas pipeline. The first waste gas pipeline is connected to the first high-temperature flue gas pipeline through the heating channel of the vaporizer 10. The first waste gas pipeline is connected to the second heat exchanger 12 via a second waste gas pipeline. The second waste gas pipeline is connected to the second high-temperature flue gas pipeline through the heat exchange channel of the second heat exchanger 12. A circulation loop is provided between the third heat exchanger 14 and the reheating device 3. The circulation loop contains a working medium.

[0023] The above setup constitutes a simple, easy-to-operate, energy-efficient, safe, and reliable combined gas-power system based on LNG and solid oxide fuel cells. In practical applications, because the solid oxide fuel cell 2's stack temperature needs to reach above 600℃ to start generating electricity, preheating of the solid oxide fuel cell 2 is required before power generation: the second control valve is closed, the first control valve is opened, and LNG, after being processed by the cold energy primary utilization device 1, becomes gaseous natural gas (around -100℃). The natural gas enters the reheating device 3 for heating and then flows sequentially through the condenser heat exchanger 4, reformer 5, first heat exchanger 6, the solid oxide fuel cell 2's stack anode, condenser heat exchanger 4, water removal device 7, and LNG-CO2 sublimation device 8 before entering the exhaust gas burner 11. Simultaneously, air, after compression, flows sequentially through the second heat exchanger 12, the solid oxide fuel cell 2's stack cathode, and the first heat exchanger 6 before entering the exhaust gas burner 11; natural gas... The gas is mixed with air and burned in the exhaust gas burner 11. The high-temperature flue gas produced by the combustion is delivered to the vaporizer 10 and the second heat exchanger 12 through the first high-temperature flue gas pipeline and the second high-temperature flue gas pipeline, respectively. The water in the vaporizer is heated by the high-temperature flue gas and turns into water vapor. The water vapor enters the reformer 5 and undergoes a reforming reaction with the flowing natural gas. The mixed gas generated after the reforming reaction (carbon monoxide and hydrogen formed by the reaction, as well as unreacted natural gas and water vapor) is heated when it flows through the anode of the solid oxide fuel cell 2. The high-temperature flue gas entering the second heat exchanger 12 exchanges heat with the air. The heated air flows through the cathode of the solid oxide fuel cell 2 and is heated. Through the above steps, the solid oxide fuel cell 2 can be cyclically heated and heated. When the stack temperature of the solid oxide fuel cell 2 reaches above 600℃, it can generate electricity and supply gas normally: the first control valve is closed and the second control valve is opened. After the LNG is processed by the cold energy primary utilization device 1, it becomes gaseous natural gas (around -100℃). The natural gas flows through the LNG-CO2 sublimation device 8 and then enters the reheating device 3. After being heated by the reheating device 3, part of the natural gas is transported to natural gas users through the gas pipeline, and part flows through the condensation heat exchanger 4 and then enters the reformer 5 to undergo a reforming reaction with the water vapor from the vaporizer 10. The mixed gas generated by the reforming reaction (carbon monoxide and hydrogen formed by the reaction, as well as unreacted natural gas and water vapor) flows through the first heat exchanger 6 and then enters the anode of the solid oxide fuel cell 2 stack. The air is compressed and flows through the second heat exchanger 12 and then enters the cathode of the solid oxide fuel cell 2 stack. The solid oxide fuel cell 2 stack generates electricity through electrochemical reaction and transmits the generated electricity to users through the power supply line.This invention establishes a combined gas-power system based on LNG and a solid oxide fuel cell. It utilizes cryogenic natural gas (around -100°C) processed by a primary cold energy utilization device 1 to capture and purify high-concentration carbon dioxide (over 50%) from the anode exhaust of the solid oxide fuel cell 2 after condensation and dehydration. This not only achieves the tiered utilization of LNG cold energy, effectively improving cold energy utilization efficiency, but also realizes the capture and purification of carbon dioxide from the anode exhaust of the solid oxide fuel cell 2. Furthermore, this invention fully utilizes the relatively low temperature of the natural gas after gasification. The cryogenic natural gas entering the solid oxide fuel cell 2 exchanges heat with the anode exhaust (containing a large amount of carbon dioxide, water vapor, and small amounts of carbon monoxide and hydrogen) in a condenser heat exchanger 4. The cold energy of the cryogenic natural gas is used to recover the condensate from the anode exhaust. This condensate then enters the vaporizer 10 for vaporization and is used in the reforming reaction, reducing external emissions. External water supply; on the other hand, the water in the anode exhaust, after condensation and separation, will increase the concentration of carbon dioxide, which is beneficial to improving the capture and purification efficiency and reducing costs; this invention mixes and burns the anode tail gas (containing unreacted carbon monoxide and hydrogen) formed after the anode exhaust is captured and separated by carbon dioxide with the cathode exhaust in the tail gas burner 11, and supplies the high-temperature flue gas generated by combustion to the vaporizer 10 and the second heat exchanger 12 respectively. While maintaining the temperature required for the stack reaction of the solid oxide fuel cell 2, this invention achieves both the capture and separation of carbon dioxide and the combustion treatment of non-condensable combustible gases, ensuring the safety of external exhaust; this invention also sets up a third heat exchanger 14, and the exhaust gas formed after the high-temperature flue gas exchanges heat with water and air respectively exchanges heat with the working medium in the third heat exchanger 14. The working medium flows in the circulation loop and transfers heat to the reheating device 3, reducing the energy consumption of the reheating device 3. It should be noted that the aforementioned cold energy primary utilization device 1, solid oxide fuel cell 2, reheating device 3, condensing heat exchanger 4, reformer 5, water removal device 7, LNG-CO2 sublimation device 8, CO2 collection device 9, vaporizer 10, and exhaust gas burner 11 are all existing devices in the art, and their structures, principles, and connection methods are well known to those skilled in the art, and will not be described in detail here. Furthermore, it should be pointed out that the electrical energy generated by the solid oxide fuel cell 2 is not limited to being transmitted to electricity users through power lines, but can also be connected to the power grid.

[0024] In a specific implementation, the functions and roles of each component in the combined gas and power system are as follows: The condenser heat exchanger 4 is used to exchange heat between the incoming natural gas and the anode exhaust, and to deliver the generated condensate to the vaporizer 10; the LNG-CO2 sublimation device 8 is used to exchange heat between the incoming natural gas and the anode exhaust, and to deliver the CO2 formed after the anode exhaust sublimation and the anode tail gas to the CO2 collection device 9 and the tail gas burner 11 respectively; the reheating device 3 is used to heat the flowing natural gas; the reformer 5 is used to reform the incoming natural gas and steam, and to deliver the carbon monoxide and hydrogen generated by the reforming reaction to the first heat exchanger 6 through the anode gas supply pipeline; the dewatering device 7 is used to remove moisture from the anode exhaust; and the CO2 collection device 9 is used to collect the CO2. Device 9 is used to collect CO2 obtained by condensing the anode exhaust gas in the LNG-CO2 sublimation unit; air compressor 13 is used to compress air; vaporizer 10 is used to vaporize water and transport the generated water vapor to reformer 5 through a steam pipeline; tail gas burner 11 is used to burn the incoming anode tail gas and cathode exhaust gas, and the generated high-temperature flue gas is transported to vaporizer 10 and second heat exchanger 12 respectively through the first high-temperature flue gas pipeline and the second high-temperature flue gas pipeline; the first heat exchanger 6 is used to exchange heat between the incoming natural gas or reformed gas and the cathode exhaust gas, the second heat exchanger 12 is used to exchange heat between the incoming air and the high-temperature flue gas, and the third heat exchanger 14 is used to exchange heat between the incoming waste gas and the working medium. Reformed gas refers to the mixed gas generated after the reforming reaction of natural gas and water vapor in reformer 5.

[0025] Based on the same concept, the present invention also provides a control method for the above-mentioned combined gas and power system, comprising the following steps:

[0026] S1. Close the second control valve and open the first control valve. After being processed by the cold energy primary utilization device 1, the LNG becomes gaseous natural gas. The natural gas enters the reheating device 3 and is heated. It then flows sequentially through the condenser heat exchanger 4, reformer 5, first heat exchanger 6, the anode of the solid oxide fuel cell 2, the condenser heat exchanger 4, the water removal device 7, and the LNG-CO2 sublimation device 8 before entering the tail gas burner 11. The air is compressed and flows sequentially through the second heat exchanger 12, the cathode of the solid oxide fuel cell 2, and the first heat exchanger 6 before entering the tail gas burner 11.

[0027] S2, natural gas, and air are mixed and burned in the exhaust gas burner 11. The high-temperature flue gas produced by combustion is delivered to the vaporizer 10 and the second heat exchanger 12 respectively through the first and second high-temperature flue gas pipelines. Water in the vaporizer 10 is heated by the high-temperature flue gas and turns into water vapor. The water vapor enters the reformer 5 and undergoes a reforming reaction with the flowing natural gas. The mixed gas generated after the reforming reaction is heated when it flows through the anode of the solid oxide fuel cell 2. The high-temperature flue gas entering the second heat exchanger 12 exchanges heat with the air. The heated air flows through the cathode of the solid oxide fuel cell 2 and is heated. Through the above operation steps, the solid oxide fuel cell 2 can be preheated.

[0028] S3. When the stack temperature of the solid oxide fuel cell 2 reaches 600℃, the first control valve is closed and the second control valve is opened. LNG is processed by the cold energy primary utilization unit 1 and converted into gaseous natural gas. The natural gas flows through the LNG-CO2 sublimation unit 8 and then enters the reheating unit 3. After being heated by the reheating unit 3, part of the natural gas is transported to natural gas users through the gas pipeline, and part flows through the condensing heat exchanger 4 and then enters the reformer to undergo a reforming reaction with water vapor from the vaporizer 10. The mixed gas generated by the reforming reaction flows through the first heat exchanger 6 and then enters the anode of the solid oxide fuel cell 2 stack. The air is compressed and flows through the second heat exchanger 12 and then enters the cathode of the solid oxide fuel cell 2 stack. The solid oxide fuel cell 2 stack generates electricity through an electrochemical reaction and transmits the generated electricity to users through the power supply line. The anode exhaust generated by power generation flows through the condensing heat exchanger 4 and the dehydration unit 7 and then enters the LNG-CO2 sublimation unit 8. The cathode exhaust generated by power generation flows through the first heat exchanger 6 and then enters the tail gas burner 11. Through the above operating steps, gas-electric cogeneration can be carried out under normal operating conditions.

[0029] In the process of combined gas and electricity generation, the heat exchange process between the related components is as follows:

[0030] S4. The natural gas flowing through the condenser heat exchanger 4 exchanges heat with the anode exhaust gas and delivers the generated condensate to the vaporizer 10. The dewatering device 7 removes water from the flowing anode exhaust gas. The LNG-CO2 sublimation device 8 exchanges heat with the flowing natural gas and the anode exhaust gas and delivers the CO2 formed after the anode exhaust gas sublimation and the anode tail gas to the CO2 collection device 9 and the tail gas burner 11 respectively.

[0031] S5. The anode exhaust gas and cathode exhaust gas entering the exhaust gas burner 11 are mixed and burned. The high-temperature flue gas generated by the combustion is delivered to the vaporizer 10 and the second heat exchanger 12 respectively through the first high-temperature flue gas pipeline and the second high-temperature flue gas pipeline. The high-temperature flue gas entering the vaporizer 10 turns water into water vapor and delivers it to the reformer 5. The high-temperature flue gas entering the second heat exchanger 12 exchanges heat with the air.

[0032] S6. The high-temperature flue gas entering the vaporizer 10 vaporizes the water and becomes waste gas. It then enters the third heat exchanger 14 through the first waste gas pipeline. The waste gas is discharged after exchanging heat with the working medium in the third heat exchanger 14. After absorbing heat, the working medium transfers the heat to the reheating device 3 through the circulation loop and heats the natural gas. The high-temperature flue gas entering the second heat exchanger 12 heats the air and also becomes waste gas. It then merges into the first waste gas pipeline through the second waste gas pipeline.

[0033] The control method for the combined gas and electricity system provided by the present invention has the advantages of simple process and high working efficiency.

[0034] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Various modifications made by those skilled in the art based on the technical solutions of the present invention without departing from the design concept of the present invention should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A combined gas and power system based on LNG and solid oxide fuel cells, characterized in that, The system includes a cold energy primary utilization device (1) and a solid oxide fuel cell (2). The input port of the cold energy primary utilization device (1) is connected to an LNG storage device. The output port of the cold energy primary utilization device (1) is connected to a reheating device (3) through a preheating pipeline equipped with a first control valve. The output port of the reheating device (3) and the anode inlet of the solid oxide fuel cell (2) are connected in sequence to a condensing heat exchanger (4), a reformer (5), and a first heat exchanger (6) through an anode gas supply pipeline. The anode gas supply pipeline between the reheating device (3) and the condensing heat exchanger (4) is connected to a gas pipeline leading to a natural gas user. The anode exhaust port of the solid oxide fuel cell (2) is connected to the condensing heat exchanger (4) through an anode exhaust pipeline and then connected in sequence to a water removal device (7), an LNG-CO2 sublimation device (8), and a CO2 collection device (9). The condensing heat exchanger (4) is connected to a vaporizer (10) through a condensate pipeline. The vaporizer (10) is connected to a steam generator (10) through a condensate pipeline. The gas pipeline is connected to the reformer (5). The LNG-CO2 sublimation device (8) is connected to the output port of the cold energy primary utilization device (1) and the input port of the reheating device (3) through the sublimation inlet pipeline and the sublimation outlet pipeline respectively. A second control valve is provided on the sublimation inlet pipeline. The LNG-CO2 sublimation device (8) is connected to the tail gas burner (11) through the tail gas pipeline. The tail gas burner (11) is connected to the vaporizer (10) through the first high temperature flue gas pipeline. The stack cathode inlet of the solid oxide fuel cell (2) is connected to the second heat exchanger (12) and the air compressor (13) in sequence through the cathode gas supply pipeline. The second heat exchanger (12) is connected to the tail gas burner (11) through the second high temperature flue gas pipeline. The stack cathode exhaust port of the solid oxide fuel cell (2) is connected to the first heat exchanger (6) and the tail gas burner (11) in sequence through the cathode exhaust pipeline. The electrical energy generated by the solid oxide fuel cell (2) is transmitted to the electricity user through the power supply line.

2. The combined gas and electricity system according to claim 1, characterized in that, It also includes a third heat exchanger (14), a first waste gas pipeline is provided between the third heat exchanger (14) and the vaporizer (10), the first waste gas pipeline is connected to the first high temperature flue gas pipeline through the heating channel of the vaporizer (10), the first waste gas pipeline is connected to the second heat exchanger (12) through the second waste gas pipeline, the second waste gas pipeline is connected to the second high temperature flue gas pipeline through the heat exchange channel of the second heat exchanger (12), and a circulation loop is provided between the third heat exchanger (14) and the reheating device (3), and a working medium is provided in the circulation loop.

3. The combined gas and electricity system according to claim 2, characterized in that, The condenser heat exchanger (4) is used to exchange heat between the incoming natural gas and the anode exhaust, and to deliver the generated condensate to the vaporizer (10). The LNG-CO2 sublimation device (8) is used to exchange heat between the incoming natural gas and the anode exhaust, and to deliver the CO2 formed after the anode exhaust sublimation and the anode tail gas to the CO2 collection device (9) and the tail gas burner (11).

4. The combined gas and electricity system according to claim 2, characterized in that, The reheating device (3) is used to heat the flowing natural gas, and the reformer (5) is used to reform the incoming natural gas and water vapor, and to transport the carbon monoxide and hydrogen generated by the reforming reaction to the first heat exchanger (6) through the anode gas supply pipeline.

5. The combined gas and electricity system according to claim 2, characterized in that, The dewatering device (7) is used to remove moisture from the anode exhaust gas, the CO2 collection device (9) is used to collect CO2 obtained by condensing the anode exhaust gas through the LNG-CO2 condensation device, and the air compressor (13) is used to compress air.

6. The combined gas and electricity system according to claim 2, characterized in that, The vaporizer (10) is used to vaporize water and transport the generated water vapor to the reformer (5) through a steam pipeline. The tail gas burner (11) is used to burn the incoming anode tail gas and cathode exhaust gas, and transport the high-temperature flue gas generated by combustion to the vaporizer (10) and the second heat exchanger (12) respectively through the first high-temperature flue gas pipeline and the second high-temperature flue gas pipeline.

7. The combined gas and electricity system according to claim 2, characterized in that, The first heat exchanger (6) is used to exchange heat between the incoming natural gas or reformed gas and the cathode exhaust gas, the second heat exchanger (12) is used to exchange heat between the incoming air and the high-temperature flue gas, and the third heat exchanger (14) is used to exchange heat between the incoming waste gas and the working medium.

8. A control method for the combined gas and electricity system as described in claim 2, characterized in that, Includes the following steps: S1. Close the second control valve and open the first control valve. After being processed by the cold energy primary utilization device (1), the LNG becomes gaseous natural gas. The natural gas enters the reheating device (3) and is heated. It then flows sequentially through the condenser heat exchanger (4), reformer (5), first heat exchanger (6), the stack anode of the solid oxide fuel cell (2), condenser heat exchanger (4), water removal device (7), and LNG-CO2 sublimation device (8) and enters the tail gas burner (11). The air is compressed and flows sequentially through the second heat exchanger (12), the stack cathode of the solid oxide fuel cell (2), and the first heat exchanger (6) and enters the tail gas burner (11). S2, natural gas and air are mixed and burned in the tail gas burner (11). The high-temperature flue gas generated by the combustion is delivered to the vaporizer (10) and the second heat exchanger (12) respectively through the first high-temperature flue gas pipeline and the second high-temperature flue gas pipeline. The water in the vaporizer (10) is heated by the high-temperature flue gas and becomes water vapor. The water vapor enters the reformer (5) and undergoes a reforming reaction with the flowing natural gas. The mixed gas generated after the reforming reaction is heated when it flows through the anode of the solid oxide fuel cell (2). The high-temperature flue gas in the second heat exchanger (12) exchanges heat with the air. The air with increased temperature is heated when it flows through the cathode of the solid oxide fuel cell (2). S3. When the stack temperature of the solid oxide fuel cell (2) rises to 600°C, the first control valve is closed and the second control valve is opened. After being processed by the cold energy primary utilization device (1), the LNG becomes gaseous natural gas. The natural gas flows through the LNG-CO2 sublimation device (8) and then enters the reheating device (3). After being heated by the reheating device (3), part of the natural gas is transported to natural gas users through the gas pipeline, and part flows through the condensation heat exchanger (4) and then enters the reformer to undergo a reforming reaction with the water vapor from the vaporizer (10). The mixed gas generated by the reforming reaction flows through the first After passing through a heat exchanger (6), the air enters the anode of the solid oxide fuel cell (2). After being compressed and flowing through a second heat exchanger (12), the air enters the cathode of the solid oxide fuel cell (2). The solid oxide fuel cell (2) generates electricity through an electrochemical reaction and transmits the generated electricity to the electricity user through the power supply line. The anode exhaust generated by the power generation flows through a condenser heat exchanger (4) and a dehydration device (7) before entering the LNG-CO2 sublimation device (8). The cathode exhaust generated by the power generation flows through a first heat exchanger (6) before entering the tail gas burner (11). S4. The natural gas flowing through the condenser heat exchanger (4) and the anode exhaust exchange heat, and the generated condensate is delivered to the vaporizer (10). The dewatering device (7) removes water from the flowing anode exhaust. The LNG-CO2 sublimation device (8) exchanges heat with the flowing natural gas and the anode exhaust, and delivers the CO2 formed after the anode exhaust sublimation and the anode tail gas to the CO2 collection device (9) and the tail gas burner (11) respectively. S5. The anode exhaust gas and cathode exhaust gas entering the exhaust gas burner (11) are mixed and burned. The high-temperature flue gas generated by the combustion is respectively transported to the vaporizer (10) and the second heat exchanger (12) through the first high-temperature flue gas pipeline and the second high-temperature flue gas pipeline. The high-temperature flue gas entering the vaporizer (10) turns water into water vapor and is transported to the reformer (5). The high-temperature flue gas entering the second heat exchanger (12) exchanges heat with the air. S6. The high-temperature flue gas entering the vaporizer (10) vaporizes the water and becomes waste gas. It enters the third heat exchanger (14) through the first waste gas pipeline. The waste gas is discharged after exchanging heat with the working medium in the third heat exchanger (14). After absorbing heat, the working medium transfers the heat to the reheating device (3) through the circulation loop and heats the natural gas. The high-temperature flue gas entering the second heat exchanger (12) heats the air and also becomes waste gas. It is then connected to the first waste gas pipeline through the second waste gas pipeline.

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