Gas-electricity combined supply system based on LNG (Liquefied Natural Gas) and solid oxide fuel cell and control method

Abstract

The invention relates to a gas-electricity combined supply system based on LNG and a solid oxide fuel cell and a control method.The system comprises a cold energy primary utilization device and the solid oxide fuel cell, and the cold energy primary utilization device is connected with an LNG storage device and a rewarming device; a condensation heat exchanger, a reformer and a first heat exchanger are sequentially connected between the rewarming device and an electric pile anode gas inlet of the solid oxide fuel cell, and an electric pile anode gas outlet of the solid oxide fuel cell is sequentially connected with the condensation heat exchanger, a water removal device, an LNG-CO2 desublimation device and a CO2 collection device; the LNG-CO2 desublimation device is connected with the cold energy primary utilization device and the rewarming device, a stack cathode gas inlet of the solid oxide fuel cell is sequentially connected with a second heat exchanger and an air compressor, and a stack cathode gas outlet of the solid oxide fuel cell is sequentially connected with a first heat exchanger and a tail gas burner; the device has the advantages of being simple in structure, convenient to control, safe and reliable. The control method has the advantages of being simple in process and high in working efficiency.

Description

Technical Field

[0001] The present invention relates to an energy supply system, in particular to a gas-electricity cogeneration system based on LNG and solid oxide fuel cells and a control method of the system. Background Art

[0002] Natural gas solid oxide fuel cell is a highly potential, environmentally friendly and efficient energy supply equipment, which uses electrochemical reaction to generate electricity, and the flue gas after the reaction can provide heat through waste heat recovery. Although solid oxide fuel cells reduce the carbon dioxide emissions per unit of power generation by improving energy efficiency, the use of natural gas will still produce a certain amount of carbon dioxide emissions, which requires the use of carbon capture to treat the exhaust and recover carbon dioxide. At present, this field mainly increases the concentration of carbon dioxide by adding pure oxygen to the anode exhaust for mixed combustion, and then captures carbon dioxide. Because oxygen needs to be prepared or purchased separately, the cost of this method is relatively high. Another way is to use a combustion reforming heat exchanger and realize the reforming reaction of methane and water through chemical chain combustion, so that the unreacted carbon monoxide and hydrogen in the anode exhaust of the stack are converted into carbon dioxide and water to increase the concentration of carbon dioxide in the anode exhaust, and then capture carbon dioxide. Because the heat balance inside the solid oxide fuel cell itself is a complex control system, coupled with the channel switching control inside the combustion reforming heat exchanger, the complexity of the control system and the difficulty of actual operation are increased. Summary of the invention

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

[0004] In order to solve the above-mentioned problems existing in the prior art, the present invention provides a gas-electricity cogeneration system based on LNG and solid oxide fuel cells, comprising a primary cold energy utilization device and a solid oxide fuel cell, wherein the input port of the primary cold energy utilization device is connected to the LNG storage device, the output port of the primary cold energy utilization device is connected to a reheating device via a preheating pipeline provided with a first control valve, a condensing heat exchanger, a reformer and a first heat exchanger are connected in sequence between the output port of the reheating device and the anode air 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 the condensing heat exchanger via the anode exhaust pipeline, and then is connected to a dehydration device, an LNG-CO2 desublimation device and a CO2 collection device in sequence, the condensing heat exchanger The heat exchanger is connected to the vaporizer through a condensate pipeline, the vaporizer is connected to the reformer through a steam pipeline, the LNG-CO2 desublimation device is connected to the output port of the cold energy primary utilization device and the input port of the rewarming device through a desublimation air inlet pipeline and a desublimation air outlet pipeline respectively, a second control valve is arranged on the desublimation air inlet pipeline, the LNG-CO2 desublimation device is connected to the tail gas burner through the tail gas pipeline, the tail gas burner is connected to the vaporizer through a first high-temperature flue gas pipeline, the cathode air inlet of the solid oxide fuel cell stack is connected to the second heat exchanger and the air compressor in sequence through the cathode air supply pipeline, the second heat exchanger is connected to the tail gas burner through the second high-temperature flue gas pipeline, 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 through the cathode exhaust pipeline, and the electric energy generated by the solid oxide fuel cell is transmitted to the electric user through the power supply line.

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

[0006] Furthermore, the present invention provides a gas-electricity cogeneration system based on LNG and solid oxide fuel cells, wherein the condensing heat exchanger is used to perform heat exchange between the introduced natural gas and the anode exhaust, and the generated condensed water is delivered to the vaporizer, and the LNG-CO2 desublimation device is used to perform heat exchange between the introduced natural gas and the anode exhaust, and the CO2 formed after the anode exhaust is desublimated and the anode tail gas are delivered to the CO2 collection device and the tail gas burner respectively.

[0007] Furthermore, the present invention provides a gas-electricity cogeneration system based on LNG and solid oxide fuel cells, wherein the retemperature device is used to heat the flowing natural gas, and the reformer is used to reform the introduced natural gas and water vapor, and transport the carbon monoxide and hydrogen generated by the reforming reaction to the first heat exchanger through the anode gas supply pipeline.

[0008] Furthermore, the present invention provides a gas-electricity cogeneration system based on LNG and solid oxide fuel cells, wherein the water removal device is used to remove moisture from the anode exhaust, the CO2 collection device is used to collect CO2 obtained by desublimating the anode exhaust through the LNG-CO2 desublimation device, and the air compressor is used to compress the air.

[0009] Furthermore, the present invention provides a gas-electricity cogeneration 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 tail gas burner is used to burn the introduced anode tail gas and cathode exhaust gas, and transport the high-temperature flue gas generated by the combustion 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 gas-power cogeneration system based on LNG and solid oxide fuel cells, wherein the first heat exchanger is used for heat exchange between the introduced natural gas or reformed gas and the cathode exhaust, the second heat exchanger is used for heat exchange between the introduced air and the high-temperature flue gas, and the third heat exchanger is used for heat exchange between the introduced exhaust gas and the working medium.

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

[0012] S1. Close the second control valve and open the first control valve. LNG is converted into gaseous natural gas after being processed by the primary cold energy utilization device. The natural gas enters the reheating device and is heated up. Then, it flows through the condensing heat exchanger, the reformer, the first heat exchanger, the anode of the solid oxide fuel cell stack, the condensing heat exchanger, the water removal device and the LNG-CO2 desublimation device in sequence and enters the tail gas burner. After being compressed, the air flows through the second heat exchanger, the cathode of the solid oxide fuel cell stack and the first heat exchanger in sequence and enters the tail gas burner.

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

[0014] S3. When the temperature of the solid oxide fuel cell stack rises to 600°C, close the first control valve and open the second control valve. LNG is converted into gaseous natural gas after being processed by the primary cold energy utilization device. The natural gas flows through the LNG-CO2 condensation device and then enters the reheating device. Part of the natural gas heated by the reheating device is delivered to the natural gas user through the gas pipeline, and part of the natural gas flows through the condensation heat exchanger and then enters the reformer and undergoes a reforming reaction with the 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 reactions and transmits the generated electricity to the electricity user through the power supply line. The anode exhaust generated by power generation flows through the condensation heat exchanger and the water removal device and then enters the LNG-CO2 condensation 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 condensing heat exchanger and the anode exhaust gas are heat exchanged, and the generated condensed water is delivered to the vaporizer, the water removal device removes water from the anode exhaust gas flowing through, the LNG-CO2 desublimation device performs heat exchange on the natural gas flowing through and the anode exhaust gas, and the CO2 formed after the anode exhaust gas is desublimated and the anode tail gas are delivered to the CO2 collection device and the tail gas burner respectively;

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

[0017] S6. The high-temperature flue gas entering the vaporizer vaporizes water and becomes waste gas, and enters the third heat exchanger through the first waste gas pipeline. The waste gas is discharged after exchanging heat with the working medium in the third heat exchanger. After the working medium absorbs heat, it transfers the heat to the rewarming device through the circulation loop and heats the natural gas. The high-temperature flue gas entering the second heat exchanger also becomes waste gas after heating the air, and is merged into the first waste gas pipeline through the second waste gas pipeline.

[0018] Compared with the prior art, the present invention provides a gas-electricity cogeneration system and control method based on LNG and solid oxide fuel cells, which has the following advantages: the present invention provides a primary cold energy utilization device and a solid oxide fuel cell, so that the input port of the primary cold energy utilization device is connected to the LNG storage device, and the output port of the primary cold energy utilization device is connected to the reheating device through a preheating pipeline provided with a first control valve, and the condensing heat exchanger, the reformer and the first heat exchanger are connected in sequence between the output port of the reheating device and the anode air inlet of the solid oxide fuel cell stack through the anode gas supply pipeline, and the anode gas supply pipeline between the reheating device and the condensing heat exchanger is connected to the gas pipeline leading to the natural gas user, and the anode exhaust port of the solid oxide fuel cell stack is connected to the condensing heat exchanger through the anode exhaust pipeline and then connected to the dewatering device, the LNG-CO2 desublimation device and the CO2 collection device in sequence, wherein, The condensing heat exchanger is connected to the vaporizer through a condensed water pipeline, the vaporizer is connected to the reformer through a steam pipeline, the LNG-CO2 condensing device is connected to the output port of the cold energy primary utilization device and the input port of the rewarming device through a condensing air inlet pipeline and a condensing air outlet pipeline respectively, a second control valve is arranged on the condensing air inlet pipeline, the LNG-CO2 condensing device is connected to the tail gas burner through the tail gas pipeline, the tail gas burner is connected to the vaporizer through a first high-temperature flue gas pipeline, the cathode air inlet of the solid oxide fuel cell stack is connected to the second heat exchanger and the air compressor in sequence through the cathode air supply pipeline, and the second heat exchanger is connected to the tail gas burner through the second high-temperature flue gas pipeline, 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 through the cathode exhaust pipeline, and the electric energy generated by the solid oxide fuel cell is transmitted to the electric user through the power supply line.The result is a gas-electricity cogeneration system based on LNG and solid oxide fuel cells with a simple structure, convenient operation, high energy utilization rate, safety and reliability. In practical applications, since the temperature of the solid oxide fuel cell stack needs to reach above 600°C before power generation, the solid oxide fuel cell needs to be preheated before power generation: close the second control valve, open the first control valve, and the LNG is converted into gaseous natural gas after being treated by the first-level cold energy utilization device. The natural gas enters the rewarming device and heats up before flowing through the condensing heat exchanger, the reformer, the first heat exchanger, the solid oxide fuel cell stack anode, the condensing heat exchanger, the water removal device and the LNG-CO2 desublimation device and enters the tail gas burner. At the same time, the air is compressed and flows 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, and the high-temperature flue gas generated by the combustion is respectively transported to the vaporizer and the second heat exchanger through the first high-temperature flue gas pipeline and the second high-temperature flue gas pipeline. The water in the vaporizer is heated by the high-temperature flue gas to become water vapor. The water vapor enters the reformer and undergoes a reforming reaction with the natural gas flowing through. The mixed gas generated after the reforming reaction heats the anode of the solid oxide fuel cell stack when it flows through the anode of the solid oxide fuel cell stack. The high-temperature flue gas entering the second heat exchanger exchanges heat with the air. The air with increased temperature heats the cathode of the solid oxide fuel cell stack when it flows through the cathode. The solid oxide fuel cell can be cyclically heated and heated through the above steps. When the temperature of the solid oxide fuel cell stack reaches above 600℃, normal power generation and gas supply can be carried out: close the first control valve, open the second control valve, LNG is converted into gaseous natural gas after being processed by the first-level cold energy utilization device, and the natural gas flows through the LNG-CO2 condensation device and then enters the rewarming device. Part of the natural gas heated by the rewarming device is transported to the natural gas users through the gas pipeline, and part of it flows through the condensing heat exchanger and then enters the reformer and undergoes a reforming reaction with the 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 reactions and transmits the generated electricity to electricity users through power supply lines.The present invention sets up a gas-electricity cogeneration system based on LNG and solid oxide fuel cells, and utilizes low-temperature natural gas (about -100°C) treated by a primary cold energy utilization device to capture and purify high-concentration carbon dioxide (more than 50%) in the anode exhaust of the solid oxide fuel cell after condensation and dehydration. This not only realizes the step-by-step utilization of LNG cold energy and effectively improves the cold energy utilization efficiency, but also realizes the capture and purification of carbon dioxide in the anode exhaust of the solid oxide fuel cell. The present invention fully utilizes the characteristic that the temperature of natural gas is still relatively low after gasification, and exchanges 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 a small amount of carbon monoxide and hydrogen) in a condensing heat exchanger, utilizing the low-temperature natural gas. The cold energy of the gas is used to recover the condensed water in the anode exhaust. On the one hand, the condensed water enters the vaporizer for vaporization and is used for the reforming reaction, thereby reducing the external additional water supply. On the other hand, the water in the anode exhaust will increase the concentration of carbon dioxide after condensation and separation, which is beneficial to improving the capture and purification efficiency and reducing the cost. The present invention makes the anode tail gas (containing unreacted carbon monoxide and hydrogen) formed after the carbon dioxide capture and separation of the anode exhaust and the cathode exhaust mixed and burned in the tail gas burner, and the high-temperature flue gas generated by the combustion is supplied to the vaporizer and the second heat exchanger respectively. On the basis of maintaining the temperature required for the stack reaction of the solid oxide fuel cell, it not only realizes the capture and separation of carbon dioxide, but also carries out combustion treatment of the non-condensable combustible gas, thereby ensuring the safety of the external exhaust.

[0019] The following is a further detailed description of a gas-electricity cogeneration system and control method based on LNG and solid oxide fuel cells according to the present invention in conjunction with the specific embodiments shown in the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of a gas-electricity cogeneration system based on LNG and solid oxide fuel cells according to the present invention. DETAILED DESCRIPTION

[0021] First of all, it should be explained that the directional words such as up, down, left, right, front and back described in the present invention are only described according to the drawings for the convenience of understanding, and are not intended to limit the technical solution and the scope of protection of the present invention.

[0022] like Figure 1The specific embodiment of the gas-electricity cogeneration system based on LNG and solid oxide fuel cells of the present invention is shown, 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 the LNG storage device, the output port of the primary cold energy utilization device 1 is connected to the reheating device 3 through a preheating pipeline provided with a first control valve, and the condensing heat exchanger 4, the reformer 5 and the first heat exchanger 6 are connected in sequence between the output port of the reheating device 3 and the anode gas inlet of the stack of the solid oxide fuel cell 2 through the anode gas supply pipeline, wherein 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 the anode exhaust pipeline and then connected to the dehydration device 7, the LNG-CO2 desublimation device 8 and the CO2 collection device 9 in sequence, wherein the condensing heat exchanger 4 is connected to the vaporizer 10 through the condensed water pipeline, the vaporizer 10 is connected to the reformer 5 through the steam pipeline, the LNG-CO2 desublimation device 8 is connected to the output port of the primary cold energy utilization device 1 and the input port of the rewarming device 3 through the desublimation air inlet pipeline and the desublimation air outlet pipeline, a second control valve is provided on the desublimation air inlet pipeline, the LNG-CO2 desublimation device 8 is connected to the exhaust gas burner 11 through the exhaust gas pipeline, and the exhaust gas burner 11 is connected to the vaporizer 10 through the first high-temperature flue gas pipeline. The cathode air 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 air supply pipeline, and the second heat exchanger 12 is connected to the tail gas burner 11 through the second high-temperature flue gas pipeline, and the 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 electric energy generated by the solid oxide fuel cell 2 is transmitted to the electric user through the power supply line. In practical applications, in order to improve energy efficiency and reduce energy consumption, the present invention further provides a third heat exchanger 14 to achieve heat recovery, wherein a first exhaust gas pipeline is provided between the third heat exchanger 14 and the vaporizer 10, the first exhaust gas pipeline is connected to the first high-temperature flue gas pipeline through the heating channel of the vaporizer 10, the first exhaust gas pipeline is connected to the second heat exchanger 12 through the second exhaust gas pipeline, the second exhaust 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 rewarming device 3, and a working medium is provided in the circulation loop.

[0023] The above arrangement constitutes a gas-electricity cogeneration system based on LNG and solid oxide fuel cells with a simple structure, convenient operation, high energy utilization rate, safety and reliability. In practical applications, since the temperature of the solid oxide fuel cell 2 stack needs to reach above 600°C before power generation, the solid oxide fuel cell 2 needs to be preheated before power generation: close the second control valve, open the first control valve, and the LNG is converted into gaseous natural gas (about -100°C) after being treated by the primary cold energy utilization device 1. The natural gas enters the reheating device 3 and heats up, and then flows through the condensing heat exchanger 4, the reformer 5, the first heat exchanger 6, the anode of the stack of the solid oxide fuel cell 2, the condensing heat exchanger 4, the water removal device 7 and the LNG-CO2 desublimation device 8 and enters the tail gas burner 11. At the same time, the air is compressed and flows through the second heat exchanger 12, the cathode of the stack of the solid oxide fuel cell 2 and the first heat exchanger 6 and enters the tail gas burner 11; the natural gas The mixture is burned with air in the tail gas burner 11, and 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 water in the vaporizer 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 natural gas flowing through. The mixed gas generated after the reforming reaction (carbon monoxide and hydrogen formed by the reaction and 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 air with increased temperature is heated when it flows through the cathode of the solid oxide fuel cell 2. The solid oxide fuel cell 2 can be cyclically heated and heated through the above steps. When the temperature of the solid oxide fuel cell stack 2 reaches above 600°C, normal power generation and gas supply can be carried out: close the first control valve, open the second control valve, LNG is converted into gaseous natural gas (about -100°C) after being processed by the first-level cold energy utilization device 1, and the natural gas flows through the LNG-CO2 condensation device 8 and then enters the rewarming device 3. Part of the natural gas heated by the rewarming device 3 is transported to the natural gas user through the gas pipeline, and part of it flows through the condensing heat exchanger 4 and then enters the reformer 5 and undergoes 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 and unreacted natural gas and water vapor) flows through the first heat exchanger 6 and then enters the anode of the solid oxide fuel cell stack 2. The air is compressed and flows through the second heat exchanger 12 and then enters the cathode of the solid oxide fuel cell stack 2. The solid oxide fuel cell stack 2 generates electricity through electrochemical reactions and transmits the generated electricity to electricity users through power supply lines.The present invention sets up a gas-electricity cogeneration system based on LNG and solid oxide fuel cells, and utilizes low-temperature natural gas (about -100°C) treated by a primary cold energy utilization device 1 to capture and purify high-concentration carbon dioxide (more than 50%) in the anode exhaust of the solid oxide fuel cell 2 after condensation and dehydration, thereby not only realizing the step-by-step utilization of LNG cold energy and effectively improving the cold energy utilization efficiency, but also realizing the capture and purification of carbon dioxide in the anode exhaust of the solid oxide fuel cell 2; the present invention fully utilizes the characteristic that the temperature of natural gas is still relatively low after gasification, and exchanges heat between the low-temperature natural gas entering the solid oxide fuel cell 2 and the anode exhaust (containing a large amount of carbon dioxide, water vapor, and a small amount of carbon monoxide and hydrogen) in a condensing heat exchanger 4, and utilizes the cold energy of the low-temperature natural gas to recover condensed water in the anode exhaust, so that the condensed water enters the vaporizer 10 for vaporization and is used for reforming reaction, thereby reducing external additional External water supply, on the other hand, the water in the anode exhaust will increase the concentration of carbon dioxide after condensation and separation, which is beneficial to improving the capture and purification efficiency and reducing the cost; the present invention makes the anode tail gas (containing unreacted carbon monoxide and hydrogen) formed after the carbon dioxide capture and separation of the anode exhaust and the cathode exhaust mixed and burned in the tail gas burner 11, and the high-temperature flue gas generated by the combustion is supplied to the vaporizer 10 and the second heat exchanger 12 respectively. On the basis of maintaining the temperature required for the stack reaction of the solid oxide fuel cell 2, it not only realizes the capture and separation of carbon dioxide, but also burns the non-condensable combustible gas to ensure the safety of external exhaust; the present invention sets a third heat exchanger 14, and makes the waste gas formed after the high-temperature flue gas is heat-exchanged with water and air respectively, and exchanges heat with the working medium in the third heat exchanger 14, and the working medium flows in the circulation loop and transfers the heat to the rewarming device 3, thereby reducing the energy consumption of the rewarming device 3. It should be noted that the above-mentioned cold energy primary utilization device 1, solid oxide fuel cell 2, rewarming device 3, condensing heat exchanger 4, reformer 5, water removal device 7, LNG-CO2 desublimation device 8, CO2 collection device 9, vaporizer 10 and tail gas burner 11 are all existing equipment in the field, and their structures, principles and connection methods are well known to technicians and will not be repeated here. It should also be pointed out that the electric energy generated by the solid oxide fuel cell 2 is not limited to being transmitted to electric users through power supply lines, but can also be incorporated into the power grid.

[0024] As a specific implementation method, the functions and effects of each component in the gas-electricity cogeneration system are as follows: the condensing heat exchanger 4 is used to perform heat exchange between the introduced natural gas and the anode exhaust, and to deliver the generated condensed water to the vaporizer 10; the LNG-CO2 desublimation device 8 is used to perform heat exchange between the introduced natural gas and the anode exhaust, and to deliver the CO2 and anode tail gas formed after the anode exhaust is desublimated to the CO2 collection device 9 and the tail gas burner 11 respectively; the reheating device 3 is used to heat the natural gas flowing through; the reformer 5 is used to perform a reforming reaction on the introduced natural gas and water vapor, 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 dehydration device 7 is used to remove moisture from the anode exhaust; the CO2 collection device 9 is used to heat the anode exhaust gas and the anode tail gas. The device 9 is used to collect CO2 obtained by desublimating the anode exhaust gas through the LNG-CO2 desublimation device; the air compressor 13 is used to compress the air; the vaporizer 10 is used to vaporize water and transport the generated water vapor to the reformer 5 through the steam pipeline; the tail gas burner 11 is used to burn the anode tail gas and cathode exhaust gas introduced, and 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 first heat exchanger 6 is used to heat exchange the introduced natural gas or reformed gas and the cathode exhaust gas, the second heat exchanger 12 is used to heat exchange the introduced air and the high-temperature flue gas, and the third heat exchanger 14 is used to heat exchange the introduced exhaust gas and the working medium. Reformed gas refers to the mixed gas generated by the reforming reaction of natural gas and water vapor in the reformer 5.

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

[0026] S1. Close the second control valve and open the first control valve. LNG is converted into gaseous natural gas after being processed by the first-level cold energy utilization device 1. The natural gas enters the rewarming device 3 to be heated and then flows through the condensing heat exchanger 4, the reformer 5, the first heat exchanger 6, the anode of the solid oxide fuel cell 2, the condensing heat exchanger 4, the water removal device 7 and the LNG-CO2 desublimation device 8 in sequence and enters the tail gas burner 11; the air is compressed and then flows through the second heat exchanger 12, the cathode of the solid oxide fuel cell 2 and the first heat exchanger 6 in sequence and enters the tail gas burner 11.

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

[0028] S3. When the temperature of the stack of the solid oxide fuel cell 2 rises to 600°C, the first control valve is closed and the second control valve is opened. The LNG is treated by the cold energy primary utilization device 1 and becomes gaseous natural gas. The natural gas flows through the LNG-CO2 condensation device 8 and enters the reheating device 3. A part of the natural gas heated by the reheating device 3 is delivered to the natural gas user through the gas pipeline, and a part of the natural gas flows through the condensation heat exchanger 4 and enters the reformer and undergoes a reforming reaction with the water vapor from the vaporizer 10. The mixed gas generated by the reforming reaction flows through the first heat exchanger 6 and enters the anode of the stack of the solid oxide fuel cell 2. The air is compressed and flows through the second heat exchanger 12 and then enters the cathode of the stack of the solid oxide fuel cell 2. The stack of the solid oxide fuel cell 2 generates electricity through electrochemical reactions and transmits the generated electricity to the electricity user through the power supply line. The anode exhaust generated by power generation flows through the condensation heat exchanger 4 and the water removal device 7 and then enters the LNG-CO2 condensation device 8. The cathode exhaust generated by power generation flows through the first heat exchanger 6 and then enters the tail gas burner 11. The above operation steps can be used to perform gas-electricity cogeneration under normal working conditions.

[0029] In the process of gas-power cogeneration, the heat exchange process between the related components is as follows:

[0030] S4. The natural gas flowing through the condensing heat exchanger 4 and the anode exhaust gas are heat exchanged, and the generated condensed water is delivered to the vaporizer 10. The dehydration device 7 removes water from the anode exhaust gas flowing through. The LNG-CO2 desublimation device 8 exchanges heat between the natural gas flowing through and the anode exhaust gas, and the CO2 formed after the anode exhaust gas is desublimated and the anode tail gas are delivered 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 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 converts 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.

[0032] S6. The high-temperature flue gas entering the vaporizer 10 vaporizes water and becomes waste gas, and 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 the working medium absorbs heat, it transfers the heat to the rewarming device 3 through the circulation loop and heats the natural gas. The high-temperature flue gas entering the second heat exchanger 12 also becomes waste gas after heating the air, and is merged into the first waste gas pipeline through the second waste gas pipeline.

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

[0034] The above embodiments are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the protection scope of the present invention. Without departing from the design concept of the present invention, various modifications made by those skilled in the art based on the technical solution of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. A gas-electricity cogeneration system based on LNG and solid oxide fuel cells, characterized in that: The invention comprises a primary cold energy utilization device (1) and a solid oxide fuel cell (2), wherein 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 provided with a first control valve, a condensing heat exchanger (4), a reformer (5) and a first heat exchanger (6) are connected in sequence between the output port of the reheating device (3) and an anode gas inlet port of a stack 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 gas outlet of the stack of the solid oxide fuel cell (2) is connected to the condensing heat exchanger (4) via an anode gas exhaust pipeline, and then is connected to a dewatering device (7), an LNG-CO2 desublimation device (8) and a CO2 collection device (9) in sequence, the condensing heat exchanger (4) is connected to a vaporizer (10) via a condensed water pipeline, and the vaporizer (10) is connected to a gas pipeline leading to a natural gas user via a vaporizer (10). The steam pipeline is connected to the reformer (5); the LNG-CO2 desublimation 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 desublimation air inlet pipeline and the desublimation air outlet pipeline; a second control valve is provided on the desublimation air inlet pipeline; the LNG-CO2 desublimation 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 cathode air inlet of the stack 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 air supply pipeline; the second heat exchanger (12) is connected to the tail gas burner (11) through the second high-temperature flue gas pipeline; the cathode exhaust port of the stack 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 electric energy generated by the solid oxide fuel cell (2) is transmitted to the electric user through the power supply line.

2. The gas-electricity cogeneration system according to claim 1, characterized in that: The invention also comprises a third heat exchanger (14), wherein a first exhaust gas pipeline is provided between the third heat exchanger (14) and the vaporizer (10), wherein the first exhaust gas pipeline is connected to the first high-temperature flue gas pipeline via a heating channel of the vaporizer (10), wherein the first exhaust gas pipeline is connected to the second heat exchanger (12) via a second exhaust gas pipeline, wherein the second exhaust gas pipeline is connected to the second high-temperature flue gas pipeline via a heat exchange channel of the second heat exchanger (12), and wherein a circulation loop is provided between the third heat exchanger (14) and the rewarming device (3), wherein a working medium is provided in the circulation loop.

3. The gas-electricity cogeneration system according to claim 2, characterized in that: The condensing heat exchanger (4) is used to perform heat exchange between the introduced natural gas and the anode exhaust, and to deliver the generated condensed water to the vaporizer (10); the LNG-CO2 desublimation device (8) is used to perform heat exchange between the introduced natural gas and the anode exhaust, and to deliver the CO2 and anode tail gas formed after the anode exhaust is desublimated to the CO2 collection device (9) and the tail gas burner (11) respectively.

4. The gas-electricity cogeneration system according to claim 2, characterized in that: The reheating device (3) is used to heat the natural gas flowing therethrough, and the reformer (5) is used to carry out a reforming reaction on the natural gas and water vapor introduced therein, 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 gas-electricity cogeneration system according to claim 2, characterized in that: The dehydration device (7) is used to remove moisture from the anode exhaust gas, the CO2 collection device (9) is used to collect CO2 obtained by desublimating the anode exhaust gas through the LNG-CO2 desublimation device, and the air compressor (13) is used to compress the air.

6. The gas-electricity cogeneration 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, and the tail gas burner (11) is used to burn the anode tail gas and cathode exhaust gas introduced, and transport the high-temperature flue gas generated by the combustion to the vaporizer (10) and the second heat exchanger (12) respectively through a first high-temperature flue gas pipeline and a second high-temperature flue gas pipeline.

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

8. A control method for the gas-electricity cogeneration system according to claim 2, characterized in that: The following steps are involved: 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. After entering the reheating device (3) and being heated, the natural gas sequentially flows through the condensing heat exchanger (4), the reformer (5), the first heat exchanger (6), the anode of the stack of the solid oxide fuel cell (2), the condensing heat exchanger (4), the water removal device (7) and the LNG-CO2 desublimation device (8) and enters the tail gas burner (11); after being compressed, the air sequentially flows through the second heat exchanger (12), the cathode of the stack 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), and 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 water in the vaporizer (10) is heated by the high-temperature flue gas to become water vapor. The water vapor enters the reformer (5) and undergoes a reforming reaction with the natural gas flowing therethrough. The mixed gas generated after the reforming reaction is heated when it flows through the anode of the stack of the solid oxide fuel cell (2). The high-temperature flue gas entering the second heat exchanger (12) is heat-exchanged with the air. The air with the increased temperature is heated when it flows through the cathode of the stack of the solid oxide fuel cell (2); S3. When the temperature of the stack of the solid oxide fuel cell (2) rises to 600°C, the first control valve is closed and the second control valve is opened. The LNG is converted into gaseous natural gas after being processed by the cold energy primary utilization device (1). The natural gas flows through the LNG-CO2 condensation device (8) and then enters the reheating device (3). A portion of the natural gas heated by the reheating device (3) is delivered to the natural gas user through the gas pipeline, and a portion of the natural gas flows through the condensing heat exchanger (4) and then enters the reformer and undergoes a reforming reaction with the water vapor from the vaporizer (10). The mixed gas generated by the reforming reaction flows through the second control valve. The air enters the anode of the solid oxide fuel cell (2) after passing through a heat exchanger (6), and enters the cathode of the solid oxide fuel cell (2) after being compressed and passing through a second heat exchanger (12); the solid oxide fuel cell (2) generates electricity through an electrochemical reaction, and transmits the generated electric energy to an electricity user through a power supply line; the anode exhaust gas generated by power generation flows through a condensing heat exchanger (4) and a water removal device (7) and enters an LNG-CO2 desublimation device (8); the cathode exhaust gas generated by power generation flows through the first heat exchanger (6) and enters an exhaust gas burner (11); S4, the natural gas flowing through the condensing heat exchanger (4) and the anode exhaust gas are heat exchanged, and the generated condensed water is delivered to the vaporizer (10), the water removal device (7) removes water from the anode exhaust gas flowing through, the LNG-CO2 desublimation device (8) performs heat exchange on the natural gas flowing through and the anode exhaust gas, and the CO2 and the anode tail gas formed after the anode exhaust gas is desublimated are delivered to the CO2 collection device (9) and the tail gas burner (11) respectively; S5, the anode exhaust gas and the cathode exhaust gas entering the exhaust burner (11) are mixed and burned, and 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) converts 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 air; S6. The high-temperature flue gas entering the vaporizer (10) vaporizes water and becomes waste gas, and enters the third heat exchanger (14) through the first waste gas pipeline. The waste gas exchanges heat with the working medium in the third heat exchanger (14) and is discharged. The working medium absorbs heat and transfers the heat to the reheating device (3) through a circulation loop to heat the natural gas. The high-temperature flue gas entering the second heat exchanger (12) heats the air and also becomes waste gas, and is merged into the first waste gas pipeline through the second waste gas pipeline.

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