A molten carbonate fuel cell power generation system and method

Abstract

The present invention provides a molten carbonate fuel cell power generation system and method, which belongs to the field of low-carbon and zero-carbon emission power generation and overcomes the high CO2 emissions problem of power generation systems in the prior art. The molten carbonate fuel cell power generation system of the present invention includes a hydrogen production device, a CO2 capture device, an MCFC power generation unit, and a catalytic combustor. The hydrogen production device includes a power generation device and an electrolytic cell, the electrolytic cell being provided with an H2 outlet and an O2 outlet. The anode inlet of the MCFC power generation unit is connected to the H2 outlet of the electrolytic cell, and the cathode inlet is connected to the O2 outlet of the electrolytic cell and the outlet of the CO2 capture device. The present invention achieves low-carbon emission power generation.

Description

Technical Field

[0001] The present invention belongs to the field of low-carbon and carbon-free power generation, and specifically relates to a molten carbonate fuel cell power generation system and method for coupling hydrogen production with flue gas from coal-fired power plants. Background Art

[0002] Molten carbonate fuel cell (MCFC) is a high-temperature fuel cell operating at around 650°C. It has the advantages of not requiring precious metals as catalysts, a wide fuel source, low noise, near-zero pollutant emissions, high power generation efficiency, a lifespan of more than 40,000 hours, and the ability to achieve combined heat and power. It is suitable for distributed power stations or fixed power stations in the hundreds of kilowatts to megawatts range, and has good development prospects.

[0003] Molten carbonate fuel cells operate at 650°C. The structure of MCFC can be divided into three parts: cathode, electrolyte and anode. The electrolyte is molten carbonate. When working, air and CO2 are introduced into the cathode, and a reaction occurs at the cathode electrode. Carbonate ions are produced; the carbonate ions pass through the electrolyte and reach the anode electrode; at the anode electrode, H2 reacts electrochemically with the carbonate ions The MCFC generates H2O and CO2. Meanwhile, electrons travel from the anode through an external circuit to the cathode, performing electrical work. The MCFC's power generation principle shows that when operating, CO2 is consumed at the cathode. The carbonate ions produced at the cathode migrate to the anode, undergoing an electrochemical reaction with the anode fuel to release CO2 and generate electricity. The migration and enrichment of CO2 in the MCFC has important environmental implications for reducing greenhouse gas (primarily CO2) emissions.

[0004] Chinese invention patent CN112864438A discloses a high-temperature fuel cell coupled power generation system and method capable of capturing carbon dioxide. Carbon-containing fuel reacts at the anodes of a solid oxide fuel cell (SOFC) and a molten carbonate fuel cell (MCFC). The anode product undergoes catalytic combustion and then enters the cathode of the MCFC for a reaction, enriching CO2 at the cathode outlet of the MCFC. Patent CN108417876A discloses a high-temperature fuel cell coupled power generation system and method. Like patent CN112864438A, this system also utilizes a solid oxide fuel cell (SOFC) and a molten carbonate fuel cell (MCFC) coupled power generation to generate electricity and enrich CO2. Both methods utilize carbon-containing fuels, consume fossil energy, and contribute to CO2 emissions.

[0005] Therefore, in the context of carbon neutrality, it is urgent to study how to reduce CO2 emissions and provide a low-carbon or even carbon-free power generation system. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the problem of high CO2 emissions in the power generation system in the prior art, thereby providing a molten carbonate fuel cell power generation system and method that couples renewable energy hydrogen production with coal-fired power plant flue gas.

[0007] The power generation principle of molten carbonate fuel cells (MCFCs) indicates their ability to absorb H2, O2, and CO2. Furthermore, the CO2 flow footprint indicates that CO2 can be enriched at the MCFC's anode through electrochemical reactions at the cathode, enabling CO2 capture. Therefore, it is possible to fully utilize the CO2 in the flue gas of existing coal-fired power plants, as well as the H2 and O2 generated by hydrogen production during periods of curtailed wind and solar power generation. These resources can be integrated with MCFC power generation systems to generate electricity while enriching and capturing CO2, achieving low-carbon CO2 emissions.

[0008] To this end, the present invention provides the following technical solutions.

[0009] On the one hand, the present invention discloses a molten carbonate fuel cell power generation system, including a hydrogen production device, a CO2 capture device, an MCFC power generation unit and a catalytic burner. The hydrogen production device includes a power generation device and an electrolytic cell. The electrolytic cell is provided with an H2 outlet and an O2 outlet. The CO2 capture device is used to capture CO2 in the flue gas. The anode inlet of the MCFC power generation unit is connected to the H2 outlet of the electrolytic cell, and the cathode inlet thereof is connected to the O2 outlet of the electrolytic cell and the gas outlet of the CO2 capture device.

[0010] Furthermore, the hydrogen production device is a renewable energy hydrogen production device; and / or the flue gas is flue gas generated by burning coal.

[0011] Furthermore, the CO2 capture device includes a fan, an absorption tower, a lean-rich heat exchanger and a desorption tower. The air inlet of the absorption tower is connected to the fan for conveying flue gas into the absorption tower, and the liquid inlet of the absorption tower is connected to the lean-rich heat exchanger for inputting a decarbonization solvent for absorbing CO2 in the flue gas into the absorption tower; the rich liquid outlet of the absorption tower is connected to the cold end inlet of the lean-rich heat exchanger through a rich liquid pump, the cold end outlet of the lean-rich heat exchanger is connected to the rich liquid inlet of the desorption tower, the lean liquid outlet of the desorption tower is connected to the hot end inlet of the lean-rich heat exchanger through a lean liquid pump, and the hot end outlet of the lean-rich heat exchanger is connected to the liquid inlet of the absorption tower.

[0012] Furthermore, a condenser and a reflux tank are connected between the desorption tower and the MCFC power generation unit;

[0013] The gas outlet of the desorption tower is connected to the inlet of the reflux tank through a condenser, the liquid outlet of the reflux tank is connected to the reflux liquid inlet of the desorption tower, and the gas outlet of the reflux tank is connected to the MCFC power generation unit.

[0014] Furthermore, the CO2 capture device further comprises a reboiler, a gas-water separator and a desalted water tank, and the catalytic burner is further connected to a burner heat exchanger;

[0015] The liquid outlet of the gas-water separator, the desalted water tank, the cold end inlet of the burner heat exchanger, the cold end outlet of the burner heat exchanger, the hot end inlet of the reboiler, the hot end outlet of the reboiler, and the gas-water separator inlet are connected in sequence; preferably, the gas outlet of the gas-water separator is connected to the steam pipeline between the cold end outlet of the burner heat exchanger and the hot end inlet of the reboiler.

[0016] Furthermore, it also includes an anode heat exchanger and a cathode heat exchanger; the H2 outlet of the electrolytic cell is connected to the anode inlet through the cold end inlet of the anode heat exchanger and the cold end outlet of the anode heat exchanger in sequence, the O2 outlet of the electrolytic cell and the gas outlet of the CO2 capture device are both connected to the cold end inlet of the cathode heat exchanger, and the cold end outlet of the cathode heat exchanger is connected to the cathode inlet;

[0017] The anode outlet is connected to the catalytic burner inlet through the anode heat exchanger hot end inlet and the anode heat exchanger hot end outlet in sequence; the cathode outlet is connected to the catalytic burner inlet through the cathode heat exchanger hot end inlet and the cathode heat exchanger hot end outlet in sequence.

[0018] Furthermore, a DC-DC power converter is included between the power generation device and the electrolytic cell.

[0019] Furthermore, the catalytic burner outlet is also connected to a CO2 compression and liquefaction device. Preferably, the catalytic burner outlet is connected to the CO2 compression and liquefaction device through a burner heat exchanger.

[0020] On the other hand, the present invention also discloses a power generation method of a molten carbonate fuel cell power generation system, comprising:

[0021] Electrolysis of water produces H2 and O2;

[0022] The decarbonization solvent is used to absorb CO2 in the flue gas, and the CO2 is output after heat exchange and desorption;

[0023] H2 is input into the anode of the MCFC power generation unit, and O2 and CO2 are input into the cathode of the MCFC power generation unit to undergo electrochemical reaction to generate carbonate ions and cathode tail gas. The carbonate ions enter the anode and undergo electrochemical reaction with H2 to generate anode tail gas. The anode tail gas and cathode tail gas are catalytically burned.

[0024] Furthermore, H2 is heat exchanged with the anode tail gas before being input into the anode, and the temperature of H2 after heating is 400-500°C; and / or, the mixed gas of CO2 and O2 is heat exchanged with the cathode tail gas before being input into the cathode, and the temperature of the mixed gas of CO2 and O2 after heating is 400-500°C.

[0025] Furthermore, at least one of the following (1)-(9) is satisfied:

[0026] (1) The pressure of the water electrolysis process is 1.5-3 MPa and the temperature is 40-60°C;

[0027] (2) Adjust the H2 pressure to 0.1-0.3 MPa and input it into the anode after heat exchange; adjust the CO2 and O2 pressures to 0.1-0.3 MPa respectively, mix them evenly, and input them into the cathode after heat exchange;

[0028] (3) The molar ratio of H2, CO2, and O2 introduced into the anode inlet and cathode inlet is 2:2:1;

[0029] (4) The flue gas is flue gas from a coal-fired power plant, preferably desulfurized flue gas from a coal-fired power plant, and preferably, the flue gas temperature is 40 to 60° C.;

[0030] (5) The decarbonization solvent is an amine absorbent, preferably ethanolamine;

[0031] (6) The decarbonization solvent absorbs CO2 in the flue gas to obtain a rich liquid. The rich liquid is heated to 80-100°C by heat exchange to desorb part of the CO2. It is then heated to 105-120°C to continue desorbing CO2 to form a lean liquid. The lean liquid is cooled to 30-50°C by heat exchange and then absorbs CO2 in the flue gas.

[0032] (7) The anode tail gas temperature is 600-650°C, and the cathode tail gas temperature is 600-650°C;

[0033] (8) After the anode tail gas exchanges heat with H2, the temperature drops to 100-120°C; after the cathode tail gas exchanges heat with CO2 and O2, the temperature drops to 100-120°C;

[0034] (9) The exhaust gas temperature after catalytic combustion is 800-1000°C. After heat exchange, the temperature drops below 120°C and is compressed and liquefied.

[0035] The technical solution of the present invention has the following advantages:

[0036] 1. The molten carbonate fuel cell power generation system provided by the present invention includes a hydrogen production device, a CO2 capture device, an MCFC power generation unit and a catalytic burner. The hydrogen production device includes a power generation device and an electrolytic cell. The electrolytic cell is provided with an H2 outlet and an O2 outlet. The anode inlet of the MCFC power generation unit is connected to the H2 outlet of the electrolytic cell, and the cathode inlet thereof is connected to the O2 outlet of the electrolytic cell and the gas outlet of the CO2 capture device.

[0037] By capturing carbon dioxide in the flue gas, a higher concentration of carbon dioxide gas can be obtained. This gas can be directly input into the cathode of the MCFC power generation unit together with the oxygen obtained from the hydrogen production device to undergo an electrochemical reaction. This not only avoids the atmospheric pollution and greenhouse effect caused by direct emission of CO2 in the flue gas, but also realizes the utilization of carbon dioxide gas, thereby significantly reducing CO2 emissions, improving energy utilization and reducing energy consumption.

[0038] Prior art research has found that the CO2 concentration in the desulfurized flue gas from coal-fired power plants is very low, only 11-12%. If the desulfurized flue gas from coal-fired power plants is directly introduced into a molten carbonate fuel cell, not only will the concentration of the reaction gas inside the cathode be too low, affecting the formation of carbonate ions and thus affecting the efficiency of the battery, but the cathode tail gas generated will also contain a large amount of N2, wasting a large amount of heat energy, making it difficult to separate the CO2 in the tail gas and forcing it to be discharged. Therefore, the present invention captures and concentrates CO2 before the desulfurized flue gas from a coal-fired power plant enters the MCFC power generation unit, which can reduce the impact of N2 on subsequent battery and system performance, and achieve the purpose of reducing CO2 emissions. The present invention uses a CO2 capture device to capture the flue gas, and the carbon dioxide gas obtained has a high concentration. The cathode tail gas generated by the electrochemical reaction is mainly carbon dioxide gas and water. The carbon dioxide in the cathode tail gas is easy to separate, and a compression liquefaction device can be used to generate liquid CO2 for oil displacement or geological storage, thereby reducing CO2 emissions.

[0039] 2. The molten carbonate fuel cell power generation system provided by the present invention features a hydrogen production device that utilizes renewable energy sources, such as wind and photovoltaic power generation, to electrolyze hydrogen to produce H2 and O2. This system can convert natural renewable energy sources, such as sunlight and wind energy, into electricity. This system utilizes electricity generated during periods of curtailed wind and solar power generation to electrolyze water into H2 and O2, eliminating the carbon emissions associated with using carbon-containing fuels such as natural gas, coal gas, and biogas for power generation within the MCFC, while also enabling the storage and utilization of renewable energy.

[0040] The overall reaction in a molten carbonate fuel cell is:

[0041]

[0042] Where, CO 2，c CO2 at the cathode, CO 2，aCO2 is the anode. The anode reaction requires H2, while the cathode reaction requires O2 and CO2. The molar ratio of H2 to CO2 is 1:1, and the molar ratio of H2 to O2 is 2:1. The molar ratio of H2 to O2 produced by hydrogen electrolysis exactly matches the molar ratio of H2 at the anode and O2 at the cathode of the MCFC, eliminating the need for additional H2 and O2 sources.

[0043] The CO2 emitted from the flue gas generated by coal combustion is captured, concentrated and recovered, and ultimately the goal of near-zero CO2 emissions is achieved. On the one hand, the present invention achieves the purpose of hydrogen energy storage, and on the other hand, it concentrates and recovers CO2 to achieve the goal of carbon emission reduction.

[0044] 3. The molten carbonate fuel cell power generation system provided by the present invention, the CO2 capture device includes a fan, an absorption tower, a lean-rich heat exchanger and a desorption tower, the air inlet of the absorption tower is connected to the fan for conveying flue gas into the absorption tower, and the liquid inlet of the absorption tower is connected to the lean-rich heat exchanger for inputting a decarbonization solvent for absorbing CO2 in the flue gas into the absorption tower; the rich liquid outlet of the absorption tower is connected to the cold end inlet of the lean-rich heat exchanger through a rich liquid pump, the cold end outlet of the lean-rich heat exchanger is connected to the rich liquid inlet of the desorption tower, the lean liquid outlet of the desorption tower is connected to the hot end inlet of the lean-rich heat exchanger through a lean liquid pump, and the hot end outlet of the lean-rich heat exchanger is connected to the liquid inlet of the absorption tower.

[0045] The flue gas from coal-fired power plants and other chemical plants is transported into the absorption tower through a fan. In the absorption tower, a decarbonization solvent is used to absorb the carbon dioxide in the flue gas to obtain a rich liquid. After heat exchange in a lean-rich heat exchanger, the liquid enters the desorption tower, where the temperature is increased to desorb and release carbon dioxide, thereby achieving the capture of carbon dioxide.

[0046] A booster fan is preferably used to increase the pressure of the desulfurized flue gas from coal-fired power plants, ensuring sufficient contact between the desulfurized flue gas and the decarbonization solvent within the absorption tower. The absorption tower absorbs the CO2 in the desulfurized flue gas with the decarbonization solvent, creating a rich liquid. Unabsorbed gas components are discharged to the atmosphere through the gas outlet at the top of the absorption tower. A rich liquid pump transports the rich liquid to the rich liquid inlet at the top of the desorption tower. A lean-rich liquid heat exchanger heats the rich liquid from the absorption tower and reduces the lean liquid temperature from the desorption tower to the absorption tower inlet temperature.

[0047] 4. The molten carbonate fuel cell power generation system provided by the present invention is also connected with a condenser and a reflux tank between the desorption tower and the MCFC power generation unit; wherein, the top gas outlet of the desorption tower is connected to the reflux tank inlet through the condenser, the liquid outlet of the reflux tank is connected to the reflux liquid inlet on the upper part of the desorption tower in sequence, and the gas outlet of the reflux tank is connected to the MCFC power generation unit.

[0048] The condenser can condense the decarbonization solvent carried by the desorbed CO2 gas into liquid and flow it into the reflux tank; the reflux tank returns the condensed and recovered decarbonization solvent to the desorption tower; the decarbonization solvent circulates in the absorption tower and the desorption tower for continuous power generation, thereby improving energy utilization and system efficiency.

[0049] 5. The molten carbonate fuel cell power generation system provided by the present invention, the CO2 capture device also includes a reboiler, a gas-water separator and a desalted water tank, and the catalytic burner is also connected to a burner heat exchanger; the liquid outlet of the gas-water separator, the desalted water tank, the cold end inlet of the burner heat exchanger, the cold end outlet of the burner heat exchanger, the hot end inlet of the reboiler, the hot end outlet of the reboiler, and the gas-water separator inlet are connected in sequence; preferably, the gas outlet of the gas-water separator is connected to the steam pipeline between the cold end outlet of the burner heat exchanger and the hot end inlet of the reboiler.

[0050] The gas-water separator condenses the moisture in the steam after heat exchange into liquid, which flows into the desalted water tank, which also stores the desalted water. The steam generated is used to heat the reboiler, serving as the heat source for desorbing CO2 from the rich liquid in the CO2 capture process, reducing steam consumption and improving system efficiency. The burner heat exchanger recovers waste heat from the high-temperature gases generated by the catalytic combustion of the MCFC cathode and anode exhaust, reducing the temperature of the high-temperature gases to below 120°C.

[0051] 6. The molten carbonate fuel cell power generation system provided by the present invention includes an anode heat exchanger and a cathode heat exchanger. The H2 outlet of the electrolytic cell is connected to the anode inlet through the anode heat exchanger cold end inlet and the anode heat exchanger cold end outlet, respectively. The gas outlet of the gas mixer is connected to the cathode inlet through the cathode heat exchanger cold end inlet and the cathode heat exchanger cold end outlet, respectively. The anode outlet is connected to the catalytic combustor inlet through the anode heat exchanger hot end inlet and the anode heat exchanger hot end outlet, respectively. The cathode outlet is connected to the catalytic combustor inlet through the cathode heat exchanger hot end inlet and the cathode heat exchanger hot end outlet, respectively. This reduces energy consumption while improving system efficiency.

[0052] The anode heat exchanger heats the H2 flowing into the anode to the MCFC anode inlet temperature of 400-500°C, and reduces the temperature of the high-temperature exhaust gas at the MCFC anode outlet to 100-120°C. The cathode heat exchanger heats the O2 and CO2 flowing into the cathode to the MCFC cathode inlet temperature of 400-500°C, and reduces the temperature of the high-temperature exhaust gas at the cathode outlet to 100-120°C.

[0053] 7. The molten carbonate fuel cell power generation system provided by the present invention also includes a DC-DC power converter between the power generation device and the electrolytic cell. The DC-DC power converter can convert the DC power generated by the renewable energy power generation device into stable output DC power.

[0054] The molten carbonate fuel cell power generation system provided by the present invention also includes a DC power inverter, which can convert the DC power generated by the MCFC power generation unit into AC power and transmit it to the power grid or users.

[0055] 8. The power generation method of the molten carbonate fuel cell power generation system provided by the present invention includes electrolyzing water to generate H2 and O2; using a decarbonization solvent to absorb CO2 in the flue gas, and outputting CO2 after heat exchange and desorption; inputting H2 into the anode of the MCFC power generation unit, and inputting O2 and CO2 into the cathode of the MCFC power generation unit to undergo electrochemical reaction to generate carbonate ions and cathode tail gas, the carbonate ions enter the anode and undergo electrochemical reaction with H2 to generate anode tail gas, and the anode tail gas and the cathode tail gas are catalytically burned.

[0056] The method of producing hydrogen from abandoned wind and solar power solves the problem of renewable energy instability. The H2 and O2 produced by electrolysis are used in MCFCs to generate electricity and heat, achieving the storage and secondary application of renewable energy and reducing carbon emissions. CO2 from desulfurized flue gas from coal-fired power plants is used as the cathode reaction medium of the MCFC, avoiding direct atmospheric pollution from CO2 emissions from coal-fired power plants. The heat from the catalytic combustion of the MCFC anode and cathode exhaust is fully utilized to desorb CO2, greatly improving the environmental characteristics and economic efficiency of the system. Furthermore, the molar ratio of H2 and O2 produced by electrolysis, and the CO2 captured from the flue gas of coal-fired power plants, fully meets the electrochemical reaction requirements of the MCFC, without introducing other impurities, thereby improving the lifespan and efficiency of the MCFC. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0058] Figure 1 This is a process flow chart of a specific example of the molten carbonate fuel cell power generation system in Example 1 of the present invention.

[0059] Reference numerals:

[0060] 1-power generation device, 2-DC-DC power converter, 3-electrolytic cell, 4-H2 storage tank, 5-O2 storage tank, 61-H2 pressure reducing valve, 62-O2 pressure reducing valve, 63-CO2 pressure reducing valve, 7-blower, 8-absorption tower, 9-rich liquid pump, 10-lean and rich liquid heat exchanger, 11-lean liquid pump, 12-desorption tower, 13-condenser, 14-reflux tank, 15-reboiler, 16-gas-water separator, 17-desalt water tank, 18-desalt water pump, 19-gas mixer, 20-anode heat exchanger, 21-MCFC power generation unit, 22-DC power inverter, 23-cathode heat exchanger, 24-catalytic burner, 25-burner heat exchanger. DETAILED DESCRIPTION

[0061] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0062] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0063] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0064] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0065] Example 1

[0066] A molten carbonate fuel cell power generation system, such as Figure 1As shown, it includes a hydrogen production device, a CO2 capture device, an MCFC power generation unit 21 and a catalytic burner 24. The hydrogen production device includes a power generation device 1 and an electrolytic cell 3. The electrolytic cell 3 is provided with an H2 outlet and an O2 outlet. The CO2 capture device is used to capture CO2 in the flue gas. The anode inlet of the MCFC power generation unit 21 is connected to the H2 outlet of the electrolytic cell 3, and its cathode inlet is connected to the O2 outlet of the electrolytic cell 3 and the gas outlet of the CO2 capture device. The power generation device 1 provides electrical energy to the electrolytic cell 3, electrolyzes water in the electrolytic cell 3 to produce H2 and O2, and the H2 is passed into the anode of the MCFC power generation unit 21 to undergo an electrochemical reaction. The O2 and CO2 captured by the CO2 capture device are passed into the cathode of the MCFC power generation unit 21 to undergo an electrochemical reaction.

[0067] In order to further reduce carbon emissions, the hydrogen production device is an existing renewable energy hydrogen production device, and the flue gas is the flue gas generated by coal combustion. Specifically, the power generation device 1 is a renewable energy power generation device, and optionally, the renewable energy power generation device is an existing photovoltaic power generation device or a wind power generation device.

[0068] Specifically, the CO2 capture device includes a fan 7, an absorption tower 8, a lean-rich heat exchanger 10, and a desorption tower 12. The air inlet of the absorption tower 8 is connected to the fan 7 for conveying flue gas into the absorption tower 8, and the liquid inlet of the absorption tower 8 is connected to the lean-rich heat exchanger 10 for inputting a decarbonization solvent into the absorption tower 8 to absorb CO2 in the flue gas. The rich liquid outlet of the absorption tower 8 is connected to the cold end inlet of the lean-rich heat exchanger 10 via a rich liquid pump 9, and the cold end outlet of the lean-rich heat exchanger 10 is connected to the rich liquid inlet of the desorption tower 12. The lean liquid outlet of the desorption tower 12 is connected to the hot end inlet of the lean-rich heat exchanger 10 via a lean liquid pump 11, and the hot end outlet of the lean-rich heat exchanger 10 is connected to the liquid inlet of the absorption tower 8. Specifically, the air inlet of the absorption tower 8 is located at the bottom of the absorption tower 8, the liquid inlet is located at the top of the absorption tower 8, the rich liquid outlet is located at the bottom of the absorption tower 8, and the top of the absorption tower 8 is also provided with an outlet for discharging gas from which CO2 has been removed by the decarbonization solvent. The rich liquid inlet of the desorption tower 12 is arranged at the upper part of the desorption tower 12 , and the lean liquid outlet is arranged at the bottom of the desorption tower 12 .

[0069] The fan 7 transports the flue gas into the absorption tower 8, where the decarbonization solvent is used to absorb the carbon dioxide in the flue gas to obtain a rich liquid. The rich liquid enters the desorption tower 12 after heat exchange through the lean-rich heat exchanger 10. The heated rich liquid is desorbed in the desorption tower 12 to release carbon dioxide, thereby capturing carbon dioxide and obtaining a higher concentration of carbon dioxide gas. This gas can be directly input into the cathode of the MCFC power generation unit 21 together with the oxygen obtained from the hydrogen production device to undergo an electrochemical reaction, which not only avoids the atmospheric pollution and greenhouse effect caused by the direct emission of CO2 in the flue gas, but also realizes the utilization of carbon dioxide gas, thereby significantly reducing CO2 emissions, improving energy utilization, and reducing energy consumption.

[0070] Preferably, the fan 7 is a booster fan, which can increase the pressure of the desulfurized flue gas from the coal-fired power plant to ensure that the desulfurized flue gas is fully in contact with the decarbonization solvent in the absorption tower 8 .

[0071] To remove unreacted H2 and O2 from the cathode and anode tail gases of the MCFC power generation unit 21, both the cathode and anode outlets of the MCFC power generation unit 21 are connected to a catalytic combustor 24. The O2 and CO2 mixture that did not react in the cathode enters the catalytic combustor 24 for catalytic combustion along with the H2, H2O, and CO2 mixture from the anode outlet. The molar ratio of unreacted H2 in the anode outlet tail gas to unreacted O2 in the cathode outlet tail gas is 2:1. All H2 and O2 react to form H2O, eliminating the need for additional H2 or O2.

[0072] In order to remove the decarbonization solvent carried by the desorbed CO2 gas and improve the purity of the CO2 introduced into the cathode of the MCFC power generation unit 21, a condenser 13 and a reflux tank 14 are further connected between the desorption tower 12 and the MCFC power generation unit 21. The gas outlet of the desorption tower 12 is connected to the inlet of the reflux tank 14 through the condenser 13, the liquid outlet of the reflux tank 14 is connected to the reflux liquid inlet of the desorption tower 12, and the gas outlet of the reflux tank 14 is connected to the MCFC power generation unit 21, specifically to the cathode inlet of the MCFC power generation unit 21. Specifically, the gas outlet of the desorption tower 12 is arranged at the top of the desorption tower 12, and the reflux liquid inlet is arranged at the upper part of the desorption tower 12. The condenser 13 can condense the decarbonization solvent carried by the desorbed CO2 gas into liquid and flow into the reflux tank 14; the reflux tank 14 returns the condensed and recovered decarbonization solvent to the desorption tower 12; the decarbonization solvent circulates in the absorption tower 8 and the desorption tower 12 for continuous power generation, thereby improving energy utilization and improving system efficiency.

[0073] In order to further improve the desorption of CO2 in the desorption tower 12, reduce energy consumption, and improve the efficiency of the system, the CO2 capture device also includes a reboiler 15, a gas-water separator 16, and a desalted water tank 17. The catalytic burner 24 is also connected to a burner heat exchanger 25. The decarbonization solvent outlet at the bottom of the desorption tower 12, the cold end inlet of the reboiler 15, the cold end outlet of the reboiler 15, and the decarbonization solvent inlet of the desorption tower 12 are connected in sequence. The liquid outlet of the gas-water separator 16, the desalted water tank 17, the cold end inlet of the burner heat exchanger 25, the cold end outlet of the burner heat exchanger 25, the hot end inlet of the reboiler 15, the hot end outlet of the reboiler 15, and the inlet of the gas-water separator 16 are connected in sequence. Preferably, the gas outlet of the gas-water separator 16 is connected to the steam pipeline between the cold end outlet of the burner heat exchanger 25 and the hot end inlet of the reboiler 15. The steam separator 16 condenses the moisture in the steam after heat exchange into liquid, which flows into the desalted water tank 17. The desalted water tank 17 also stores the desalted water. The desalted water is then transported to the burner heat exchanger 25 for heat exchange and temperature increase. The steam generated heats the reboiler 15, serving as the heat source for further desorption of CO2 from the rich liquid during the CO2 capture process. The rich liquid partially desorbs CO2 through stripping in the desorption tower 12, and then enters the reboiler 15 for heating and further desorption of the CO2. The burner heat exchanger 25 recovers waste heat from the high-temperature gases generated by the catalytic combustion of the MCFC cathode and anode exhaust, reducing the temperature of the high-temperature gases to below 120°C.

[0074] In order to ensure that the pressure of the desalted water meets the application requirements of various distances or height differences between the desalted water tank 17 and the cold end inlet of the burner heat exchanger 25, a desalted water pump 18 is further provided between the desalted water tank 17 and the cold end inlet of the burner heat exchanger 25.

[0075] To reduce energy consumption and improve system efficiency, the system also includes an anode heat exchanger 20 and a cathode heat exchanger 23. The H2 outlet of the electrolytic cell 3 is connected to the anode inlet via the cold inlet and outlet of the anode heat exchanger 20, respectively. The O2 outlet of the electrolytic cell 3 and the gas outlet of the CO2 capture device are both connected to the cold inlet of the cathode heat exchanger 23, and the cold outlet of the cathode heat exchanger 23 is connected to the cathode inlet. The anode outlet is connected to the inlet of the catalytic combustor 24 via the hot inlet and outlet of the anode heat exchanger 20, respectively. The cathode outlet is connected to the inlet of the catalytic combustor 24 via the hot inlet and outlet of the cathode heat exchanger 23, respectively. The heat of the anode tail gas is used to heat the H2 to be introduced into the anode. The anode heat exchanger 20 can heat the H2 to the MCFC anode inlet temperature of 400-500°C, reducing the temperature of the high-temperature tail gas at the MCFC anode outlet to 100-120°C. The heat of the cathode exhaust gas is used to heat the O2 and CO2 to be passed into the cathode. The cathode heat exchanger 23 can heat the O2 and CO2 to be passed into the cathode to the MCFC cathode inlet temperature of 400-500°C, and reduce the temperature of the high-temperature exhaust gas at the cathode outlet to 100-120°C.

[0076] To evenly mix O2 and CO2 before passing them into the cathode, a gas mixer 19 is also included. The O2 outlet of the electrolytic cell 3 and the gas outlet of the CO2 capture device are both connected to the gas mixer 19. The outlet of the gas mixer 19 is connected to the cathode inlet of the MCFC power generation unit 21. O2 and CO2 are evenly mixed in the gas mixer 19 before being passed into the cathode of the MCFC power generation unit 21. The gas mixer 19 evenly mixes the CO2 and O2 to achieve a molar ratio of 2:1.

[0077] Furthermore, a DC-DC power converter 2 is provided between the power generation device 1 and the electrolytic cell 3. The DC-DC power converter 2 can convert the DC power generated by the power generation device 1 into DC power with stable output.

[0078] Furthermore, it also includes a DC power inverter 22, which is electrically connected to the MCFC power generation unit 21 and can convert the DC power generated by the MCFC power generation unit 21 into AC power and transmit it to the power grid or users.

[0079] Furthermore, the outlet of the catalytic burner 24 is connected to a CO2 compression and liquefaction device, which compresses and liquefies the CO2 and then drives oil or seals it. To facilitate the compression and liquefaction of the CO2, the exhaust gas at the outlet of the catalytic burner 24 is cooled. Specifically, the outlet of the catalytic burner 24 is connected to the CO2 compression and liquefaction device via a burner heat exchanger 25. After the exhaust gas temperature is reduced, it is easier to remove water from the exhaust gas, improve the purity of the CO2, and reduce system energy consumption and waste.

[0080] In one embodiment of the present invention, the hydrogen production apparatus further includes an H2 storage tank 4 and an O2 storage tank 5. The H2 outlet and the O2 outlet are connected to the H2 storage tank 4 and the O2 storage tank 5, respectively. The outlet of the H2 storage tank 4 is provided with an H2 pressure reducing valve 61, and the outlet of the O2 storage tank 5 is provided with an O2 pressure reducing valve 62. Water is electrolyzed into H2 and O2, which enter the H2 storage tank 4 and the O2 storage tank 5. The H2 and O2 pressure reducing valves 61 and 62 adjust the H2 and O2 to the operating pressure of the MCFC power generation unit 21.

[0081] In one embodiment of the present invention, a CO2 pressure reducing valve 63 is provided at the gas outlet of the reflux tank 14, which can adjust the pressure of CO2 to the operating pressure of MCFC.

[0082] As an alternative embodiment, the flue gas is flue gas from a coal-fired power plant, preferably desulfurized flue gas from a coal-fired power plant, specifically, flue gas from a supercritical power plant, an ultra-supercritical power plant, or a natural gas combined cycle power plant.

[0083] Example 2

[0084] This embodiment provides a method for generating electricity using a molten carbonate fuel cell power generation system, which uses the molten carbonate fuel cell power generation system provided in embodiment 1 to generate electricity, specifically comprising:

[0085] The DC power from the photovoltaic hydrogen production unit is converted to stable DC power by a DC-DC converter 2 and fed to an electrolytic cell 3. Within the electrolytic cell 3, water is electrolyzed into H2 and O2 at a pressure of 3 MPa and a temperature of 40°C. These are stored in H2 and O2 storage tanks 4 and 5, respectively. Desulfurized flue gas from the coal-fired power plant, at a temperature of 40°C, is boosted to 0.5 MPa by a booster fan 7 and fed into an absorption tower. The flue gas flows upward, where the CO2 is absorbed by the decarbonization solvent, ethanolamine solution. Unabsorbed gas is discharged into the atmosphere from the top of absorption tower 8. The rich liquid, after absorbing the CO2, is pumped from the bottom of absorption tower 8 via a rich liquid pump 9 to a lean-rich liquid heat exchanger 10. After absorbing heat and raising its temperature, it is fed to a desorption tower 12. The desorbed CO2, at 97.5°C, along with water vapor, is cooled in a condenser 13. The decarbonization solvent is then separated and removed in a reflux tank 14, resulting in product CO2 gas with a purity of at least 99.5% (dry basis) at 40°C. The decarbonization solvent separated by condensation is sent to the desorption tower 12, and the rich liquid at 96°C enters from the rich liquid inlet at the upper part of the desorption tower 12, desorbs part of the CO2 through steam stripping, and then enters the reboiler 15 with a temperature of 110°C to further desorb the CO2 therein. The lean liquid after desorption of CO2 flows out from the bottom of the desorption tower 12 at 110°C, and after heat exchange in the lean and rich liquid heat exchanger 10, the temperature drops to 40°C, and is sent to the absorption tower 8 by the lean liquid pump 11. The decarbonization solvent circulates back and forth to constitute a process of continuous absorption and desorption of CO2.

[0086] H2 from H2 storage tank 4 is reduced in pressure to 0.2 MPa by H2 pressure reducing valve 61 and fed into anode heat exchanger 20. After being heated to 400°C, it enters the anode of MCFC power generation unit 21. CO2 from the CO2 capture device and O2 from O2 storage tank 5 are both reduced in pressure to 0.2 MPa. The CO2 flow rate is adjusted to the same as the H2 flow rate, and the molar ratio of CO2 to O2 is adjusted to 2:1. The CO2 and O2 are then passed into gas mixer 19 for uniform mixing. The mixture is then fed into cathode heat exchanger 23, where it is preheated to 400°C before entering the cathode of MCFC power generation unit 21. The H2 entering the anode of MCFC power generation unit 21 and the CO2 and O2 entering the cathode undergo electrochemical reactions within MCFC power generation unit 21 to generate electricity and heat. The resulting DC power is converted into AC power by DC power inverter 22 and fed to the grid or users.

[0087] The exhaust gas temperature at the anode and cathode outlets is 650°C, and after heat exchange through the anode heat exchanger 20 and cathode heat exchanger 23, the temperature drops to 120°C. At the cathode of the MCFC power generation unit 21, approximately 70% of the CO2 reacts with O2 to form carbonate ions. The carbonate ions move through the electrolyte layer to the anode and react with approximately 70% of the H2 at the anode to form H2O and CO2. The anode exhaust gas contains 30% of the unreacted H2 and 70% of the CO2 from the cathode. The cathode exhaust gas of the MCFC power generation unit 21 contains 30% of the unreacted CO2 and O2. The unreacted H2, O2, and CO2 in the cathode exhaust gas and anode exhaust gas of the MCFC power generation unit 21 enter the catalytic burner 24 to recover the energy of the remaining small amount of H2. The catalytic combustion products only contain H2O and CO2. The catalytic combustion exhaust gas is at a temperature of 1000°C and enters the burner heat exchanger 25. The room temperature desalted water is pressurized to 0.9 MPa by the desalted water pump 18 and sent to the burner heat exchanger 25 to recover heat and generate low-pressure steam of 0.8 MPa and 179°C. After the catalytic combustion exhaust gas is cooled to room temperature, it is sent to the CO2 compression liquefaction device to generate liquid CO2 for oil recovery or geological storage.

[0088] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A molten carbonate fuel cell power generation system, characterized in that: It includes a hydrogen production device, a CO2 capture device, an MCFC power generation unit, a catalytic burner, an anode heat exchanger and a cathode heat exchanger; the catalytic burner is also connected to a burner heat exchanger; The hydrogen production device includes a power generation device and an electrolytic cell, wherein the electrolytic cell is provided with an H2 outlet and an O2 outlet; the CO2 capture device is used to capture CO2 in the flue gas; the anode inlet of the MCFC power generation unit is connected to the H2 outlet of the electrolytic cell, and the cathode inlet thereof is connected to the O2 outlet of the electrolytic cell and the gas outlet of the CO2 capture device; The H2 outlet of the electrolytic cell is connected to the anode inlet through the cold end inlet of the anode heat exchanger and the cold end outlet of the anode heat exchanger in sequence, the O2 outlet of the electrolytic cell and the gas outlet of the CO2 capture device are both connected to the cold end inlet of the cathode heat exchanger, and the cold end outlet of the cathode heat exchanger is connected to the cathode inlet; The anode outlet is connected to the catalytic burner inlet through the hot end inlet of the anode heat exchanger and the hot end outlet of the anode heat exchanger in sequence; the cathode outlet is connected to the catalytic burner inlet through the hot end inlet of the cathode heat exchanger and the hot end outlet of the cathode heat exchanger in sequence; The CO2 capture device also includes a reboiler, a gas-water separator and a desalted water tank; The liquid outlet of the gas-water separator, the desalted water tank, the cold end inlet of the burner heat exchanger, the cold end outlet of the burner heat exchanger, the hot end inlet of the reboiler, the hot end outlet of the reboiler, and the gas-water separator inlet are connected in sequence.

2. The molten carbonate fuel cell power generation system according to claim 1, characterized in that: The hydrogen production device is a renewable energy hydrogen production device; and / or the flue gas is flue gas generated by burning coal.

3. The molten carbonate fuel cell power generation system according to claim 1 or 2, characterized in that: The CO2 capture device includes a fan, an absorption tower, a lean-rich heat exchanger and a desorption tower. The air inlet of the absorption tower is connected to the fan for conveying flue gas into the absorption tower, and the liquid inlet of the absorption tower is connected to the lean-rich heat exchanger for inputting a decarbonization solvent for absorbing CO2 in the flue gas into the absorption tower; the rich liquid outlet of the absorption tower is connected to the cold end inlet of the lean-rich heat exchanger through a rich liquid pump, the cold end outlet of the lean-rich heat exchanger is connected to the rich liquid inlet of the desorption tower, the lean liquid outlet of the desorption tower is connected to the hot end inlet of the lean-rich heat exchanger through a lean liquid pump, and the hot end outlet of the lean-rich heat exchanger is connected to the liquid inlet of the absorption tower.

4. The molten carbonate fuel cell power generation system according to claim 3, characterized in that: A condenser and a reflux tank are also connected between the desorption tower and the MCFC power generation unit; The gas outlet of the desorption tower is connected to the inlet of the reflux tank through a condenser, the liquid outlet of the reflux tank is connected to the reflux liquid inlet of the desorption tower, and the gas outlet of the reflux tank is connected to the MCFC power generation unit.

5. The molten carbonate fuel cell power generation system according to claim 4, characterized in that: The gas outlet of the gas-water separator is connected to the steam pipeline between the cold end outlet of the burner heat exchanger and the hot end inlet of the reboiler.

6. The molten carbonate fuel cell power generation system according to claim 1 or 2, characterized in that: A DC-DC power converter is also included between the power generation device and the electrolytic cell.

7. A method for generating electricity using the molten carbonate fuel cell power generation system according to any one of claims 1 to 6, characterized in that: include, Electrolysis of water produces H2 and O2; The decarbonization solvent is used to absorb CO2 in the flue gas, and the CO2 is output after heat exchange and desorption; H2 is input into the anode of the MCFC power generation unit, and O2 and CO2 are input into the cathode of the MCFC power generation unit to undergo electrochemical reaction to generate carbonate ions and cathode tail gas. The carbonate ions enter the anode and undergo electrochemical reaction with H2 to generate anode tail gas. The anode tail gas and cathode tail gas are catalytically burned. Before being input into the anode, H2 is heat exchanged with the anode tail gas, and the temperature of H2 after heating is 400-500°C; before being input into the cathode, the mixed gas of CO2 and O2 is heat exchanged with the cathode tail gas, and the temperature of the mixed gas of CO2 and O2 after heating is 400-500°C.

8. The power generation method of the molten carbonate fuel cell power generation system according to claim 7, characterized in that: Also satisfies at least one of the following (1)-(9): (1) The pressure of the water electrolysis process is 1.5-3 MPa and the temperature is 40-60°C; (2) Adjust the H2 pressure to 0.1-0.3 MPa and input it into the anode after heat exchange; adjust the CO2 and O2 pressures to 0.1-0.3 MPa respectively, mix them evenly, and input them into the cathode after heat exchange; (3) The molar ratio of H2, CO2, and O2 introduced into the anode inlet and cathode inlet is 2:2:1; (4) The flue gas is from a coal-fired power plant; (5) The decarbonization solvent is an amine absorbent; (6) The decarbonization solvent absorbs CO2 in the flue gas to obtain a rich liquid. The rich liquid is heated to 80-100°C by heat exchange to desorb part of the CO2. It is then heated to 105-120°C to continue desorbing CO2 to form a lean liquid. The lean liquid is cooled to 30-50°C by heat exchange and then sent to the absorption tower to absorb the CO2 in the flue gas. (7) The anode tail gas temperature is 600-650°C, and the cathode tail gas temperature is 600-650°C; (8) After the anode tail gas exchanges heat with H2, the temperature drops to 100-120°C; after the cathode tail gas exchanges heat with CO2 and O2, the temperature drops to 100-120°C; (9) The exhaust gas temperature after catalytic combustion is 800-1000°C. After heat exchange, the temperature drops below 120°C and is compressed and liquefied.

9. The power generation method of the molten carbonate fuel cell power generation system according to claim 8, characterized in that: The flue gas is desulfurized flue gas from a coal-fired power plant.

10. The power generation method of the molten carbonate fuel cell power generation system according to claim 8, characterized in that: The flue gas temperature is 40-60℃.

11. The power generation method of the molten carbonate fuel cell power generation system according to claim 8, characterized in that: The decarbonization solvent is ethanolamine solution.

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