High-temperature methanol reforming fuel cell system for realizing carbon cycle and operation process

Abstract

The invention belongs to the technical field of fuel cells, and particularly relates to a high-temperature methanol reforming fuel cell system for realizing carbon cycle and an operation process. The system comprises an electric pile, a methanol steam reforming hydrogen production reactor, a carbon dioxide hydrogenation methanol production reactor and an electrolyzed water module, hydrogen prepared by the methanol steam reforming hydrogen production reactor enters an anode of the galvanic pile through a pipeline, a cathode of the galvanic pile is supplied by an air pump, and the hydrogen and oxygen are subjected to electrochemical reaction in the galvanic pile to realize external power supply; liquid water recovered from the electric pile tail gas is introduced into the water electrolysis module, and water electrolysis is performed to generate hydrogen; carbon dioxide in the stack tail gas and hydrogen generated by the water electrolysis module enter the carbon dioxide hydrogenation methanol preparation reactor through the gas inlet pipeline to prepare methanol. According to the invention, the circulation of carbon in the high-temperature methanol fuel cell system is realized, the emission of carbon dioxide is reduced, the circulation of hydrogen and oxygen is realized, and the energy utilization efficiency of the system is jointly improved through the circulation of carbon, hydrogen and oxygen.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cells, and particularly relates to a high-temperature methanol reforming fuel cell system for realizing carbon cycle and an operation process thereof. Background Art

[0002] A fuel cell is a device that directly converts the chemical energy stored in a compound fuel into electrical energy through a chemical reaction, and has advantages such as high efficiency, long endurance, environmental friendliness, and low noise, and is widely used in various fields.

[0003] A high-temperature methanol reforming fuel cell (HTMFC) uses an aqueous methanol solution as fuel, converts the aqueous methanol solution into a mixture of H2 (hydrogen) and CO2 (carbon dioxide) through a reformer, and reacts in a high-temperature proton exchange membrane fuel cell stack to output electrical energy externally. The membrane electrode of the stack uses a high-temperature resistant polymer electrolyte membrane doped with phosphoric acid, and generally operates at a temperature of 150-180 °C, and has strong resistance to CO (carbon monoxide) poisoning performance, and has broad application prospects in fields such as vehicle power, marine power, combined heat and power supply, and replacement of oil engines.

[0004] However, since this fuel cell system uses a mixture of H2 (hydrogen) and CO2 (carbon dioxide) produced by methanol steam reforming for hydrogen production as the anode fuel of the stack, greenhouse gas CO2 (carbon dioxide) will be continuously emitted in the tail gas emission. Although the process of producing methanol from CO2 and H2 is relatively mature in China at present, it is difficult to capture CO2 from the atmosphere and a large amount of energy will be consumed during the process; at the same time, in the current methanol reforming hydrogen fuel cell system, the heat absorption of the reformer reaction generally uses the combustion of a part of the hydrogen-rich reformed gas after reforming to provide heat, and this part of hydrogen only provides heat and does not play a role as the fuel of the stack. The energy utilization efficiency of the system is generally between 40% and 50%, and there is still much room for improvement. Summary of the Invention

[0005] Aiming at the above problems, the purpose of the present invention is to provide a high-temperature methanol reforming fuel cell system for realizing carbon cycle and an operation process thereof, so as to solve the problem of low energy utilization efficiency of the existing fuel cell system.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: On the one hand, the present invention provides a high-temperature methanol reforming fuel cell system for realizing carbon cycle, including a stack, a methanol steam reforming for hydrogen production reactor, a carbon dioxide hydrogenation for methanol production reactor, and an electrolyzed water module; The hydrogen produced by the methanol steam reforming hydrogen production reactor enters the anode of the fuel cell stack through a pipeline. The cathode of the fuel cell stack is fed by an air pump. Hydrogen and oxygen undergo an electrochemical reaction in the fuel cell stack to generate external power supply. The liquid water recovered from the cathode exhaust gas of the fuel cell stack is introduced into the electrolyzed water module to electrolyze water to produce hydrogen. The carbon dioxide in the anode exhaust gas of the fuel cell stack and the hydrogen produced by the electrolyzed water module enter the carbon dioxide hydrogenation to methanol reactor through the inlet pipeline to produce methanol.

[0007] The methanol steam reforming hydrogen production reactor and the carbon dioxide hydrogenation to methanol reactor are coupled into an integrated structure. A reactor bed electric heater is arranged between the methanol steam reforming hydrogen production reactor and the carbon dioxide hydrogenation to methanol reactor. During the startup phase of the system, the reactor bed electric heater provides heat sources for the methanol steam reforming hydrogen production reactor and the carbon dioxide hydrogenation to methanol reactor. During the stable operation phase of the system, the reactor bed electric heater is turned off. The carbon dioxide hydrogenation to methanol reactor undergoes a methanol production reaction, and the reaction is an exothermic reaction that can provide heat sources for the reforming hydrogen production, maintain the temperatures of the two beds, and reduce the external heating power consumption.

[0008] Both ends of the methanol steam reforming hydrogen production reactor are respectively provided with a methanol steam reforming hydrogen production reactor inlet and a methanol steam reforming hydrogen production reactor outlet. The methanol steam reforming hydrogen production reactor inlet is connected to a liquid pump and a methanol aqueous solution fuel tank through a pipeline. The methanol steam reforming hydrogen production reactor outlet is connected to the anode of the fuel cell stack through a pipeline. A coupling heat exchanger is arranged on the two pipelines connected to the methanol steam reforming hydrogen production reactor inlet and the methanol steam reforming hydrogen production reactor outlet.

[0009] The high-temperature methanol reforming fuel cell system for realizing carbon cycle further includes a heating circulation system. The heating circulation system includes a circulation oil pump, a circulation oil electric heater, and a circulation oil radiator connected in sequence through a circulation oil pipeline. The circulation oil pipeline passes through the coupling heat exchanger, and both ends of the circulation oil pipeline are respectively connected to both ends of the fuel cell stack.

[0010] Both ends of the carbon dioxide hydrogenation to methanol reactor are respectively provided with a carbon dioxide hydrogenation to methanol reactor inlet and a carbon dioxide hydrogenation to methanol reactor outlet. The carbon dioxide hydrogenation to methanol reactor inlet is connected to the inlet pipeline. The carbon dioxide hydrogenation to methanol reactor outlet is connected to a gas cooler and a methanol aqueous solution recovery tank in sequence through a pipeline.

[0011] The electrolyzed water module includes an electrolytic cell and a solar panel connected to the electrolytic cell. The solar panel converts solar energy into direct current electrical energy, inputs the generated direct current electrical energy into the electrolytic cell, electrolyzes the recycled water in the electrolytic cell, and an electrochemical reaction occurs. The hydrogen generated at the cathode of the electrolytic cell is mixed with the anode tail gas of the stack, pressurized by a compressor, and then input into the carbon dioxide hydrogenation to methanol reactor.

[0012] The electrolyzed water module can also be composed of an electrolytic cell and a wind turbine connected to the electrolytic cell. The wind turbine converts the wind energy of each radiator fan in the system and the external wind energy into direct current electrical energy, inputs the generated direct current electrical energy into the electrolytic cell, electrolyzes the recycled water in the electrolytic cell, and an electrochemical reaction occurs. The hydrogen generated at the cathode of the electrolytic cell is mixed with the anode tail gas of the stack, pressurized by a compressor, and then input into the carbon dioxide hydrogenation to methanol reactor.

[0013] The oxygen generated at the anode of the electrolytic cell is mixed with the cathode intake gas of the stack and reused as the cathode oxidant of the stack.

[0014] The cathode tail gas of the stack is sequentially connected to a cathode tail gas cooler, a gas-liquid separator, and a water tank through pipelines, and the water tank is connected to the electrolyzed water module through a pipeline.

[0015] On the other hand, the present invention provides an operating process for a high-temperature methanol reforming fuel cell system for realizing carbon cycling as described above. By utilizing the tail gas of the stack in the system to produce methanol, a thermal coupling design is carried out for the methanol steam reforming to hydrogen reactor and the carbon dioxide hydrogenation to methanol reactor, realizing the cycling of carbon and fuel and the efficient utilization of internal heat, and reducing the carbon emissions of the methanol fuel cell system; at the same time, combined with the electrolyzed water module, the water recycled from the stack tail gas in the system is electrolyzed to produce hydrogen, which is used as the raw material for carbon dioxide hydrogenation to methanol, and the oxygen produced by water electrolysis is reused as the oxidant of the cathode of the stack. Through the cycling of carbon, hydrogen, and oxygen, the energy utilization efficiency of the system is improved.

[0016] The advantages and beneficial effects of the present invention are as follows: A high-temperature methanol reforming fuel cell system and an operating process for realizing carbon cycling provided by the present invention recycle and reuse the stack tail gas CO2 (carbon dioxide) and H2 (hydrogen) in the system to produce methanol, combine methanol reforming to hydrogen and its reverse reaction of carbon dioxide hydrogenation to methanol in the system, and combine with the internal thermal coupling design of the system to realize the cycling of carbon and fuel and the efficient utilization of internal heat, reducing the carbon emissions of the methanol fuel cell system; at the same time, combined with the electrolyzed water function of the solar power generation module, the water recycled from the stack tail gas in the system is electrolyzed to produce hydrogen, which is used as the raw material for carbon dioxide hydrogenation to methanol, and the oxygen produced by water electrolysis is reused as the oxidant of the cathode of the stack. The above cycling of C (carbon dioxide), H (hydrogen), and O (oxygen) reduces the carbon emissions of the high-temperature methanol reforming fuel cell system and improves the energy utilization efficiency of the system. Description of the Drawings

[0017] Figure 1 is a schematic structural diagram of a high-temperature methanol reforming fuel cell system for realizing carbon cycle in an embodiment of the present invention; Figure 2 is a schematic structural diagram of the coupling of a methanol steam reforming hydrogen production reactor and a carbon dioxide hydrogenation to methanol reactor in the present invention; Figure 3 is a schematic structural diagram of a solar power generation electrolyzed water module in the present invention; Figure 4 is a schematic structural diagram of a high-temperature methanol reforming fuel cell system for realizing carbon cycle in another embodiment of the present invention.

[0018] In the figure: 1 - fuel cell stack, 2 - methanol steam reforming hydrogen production reactor, 3 - carbon dioxide hydrogenation to methanol reactor, 4 - methanol aqueous solution fuel tank, 5 - gas-liquid separator, 6 - liquid pump, 7 - gas pump, 8 - circulating oil pump, 9 - circulating oil electric heater, 10 - coupling heat exchanger, 11 - circulating oil radiator, 12 - reactor bed electric heater, 13 - water tank, 14 - electrolyzer, 15 - solar panel, 16 - compressor, 17 - gas cooler, 18 - methanol aqueous solution recovery tank, 19 - fuel cell stack cathode tail gas cooler, 20 - wind turbine, A - inlet of methanol steam reforming hydrogen production reactor, B - outlet of methanol steam reforming hydrogen production reactor, C - inlet of carbon dioxide hydrogenation to methanol reactor, D - outlet of carbon dioxide hydrogenation to methanol reactor, E - hydrogen side outlet of electrolyzer, F - oxygen side outlet of electrolyzer. Detailed Embodiments

[0019] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] See Figures 1 to 3 As shown, an embodiment of the present invention provides a high-temperature methanol reforming fuel cell system for realizing carbon cycle, including a fuel cell stack 1, a methanol steam reforming hydrogen production reactor 2, a carbon dioxide hydrogenation to methanol reactor 3 and an electrolyzed water module; the methanol steam reforming hydrogen production reactor 2 produces hydrogen by methanol steam reforming, the hydrogen prepared by the methanol steam reforming hydrogen production reactor 2 enters the anode of the fuel cell stack 1 through a pipeline, the cathode of the fuel cell stack 1 is fed by a gas pump 7, and hydrogen and oxygen undergo an electrochemical reaction in the fuel cell stack 1 to realize external power supply; the liquid water recovered from the cathode tail gas of the fuel cell stack 1 is introduced into the electrolyzed water module to electrolyze water to produce hydrogen; the carbon dioxide in the anode tail gas of the fuel cell stack 1 and the hydrogen produced by the electrolyzed water module enter the carbon dioxide hydrogenation to methanol reactor 3 through an inlet pipeline, and the carbon dioxide hydrogenation to methanol reactor 3 produces methanol by carbon dioxide hydrogenation.

[0021] See Figure 1 As shown, in the embodiment of the present invention, the cathode exhaust gas of the stack 1 is sequentially connected to the stack cathode exhaust gas cooler 19, the gas-liquid separator 5, and the water tank 13 through pipelines, and the water tank 13 is connected to the electrolyzed water module through a pipeline.

[0022] See Figure 1 and Figure 2 As shown, in the embodiment of the present invention, the methanol steam reforming hydrogen production reactor 2 and the carbon dioxide hydrogenation to methanol reactor 3 are coupled into an integrated structure, and a reactor bed electric heater 12 is arranged between the methanol steam reforming hydrogen production reactor 2 and the carbon dioxide hydrogenation to methanol reactor 3. During the start-up stage of the system, the reactor bed electric heater 12 provides heat sources for the methanol steam reforming hydrogen production reactor 2 and the carbon dioxide hydrogenation to methanol reactor 3. During the stable operation stage of the system, the reactor bed electric heater 12 is turned off. The carbon dioxide hydrogenation to methanol reactor 3 undergoes a methanol production reaction, and the reaction is an exothermic reaction that can provide heat sources for reforming hydrogen production, maintain the temperatures of the two beds, and reduce the external heating power consumption. Methanol steam reforming hydrogen production reactor inlets A and outlets B are respectively arranged at both ends of the methanol steam reforming hydrogen production reactor 2. The methanol steam reforming hydrogen production reactor inlet A is connected to the liquid pump 6 and the methanol aqueous solution fuel tank 4 through pipelines; the methanol steam reforming hydrogen production reactor outlet B is connected to the anode of the stack 1 through a pipeline, and a coupling heat exchanger 10 is arranged on the two pipelines connecting the methanol steam reforming hydrogen production reactor inlet A and the methanol steam reforming hydrogen production reactor outlet B.

[0023] Furthermore, a high-temperature methanol reforming fuel cell system for realizing carbon cycle provided by the present invention further includes a heating circulation system; the heating circulation system includes a circulation oil pump 8, a circulation oil electric heater 9, and a circulation oil radiator 11 that are sequentially connected through a circulation oil pipeline. The circulation oil pipeline passes through the coupling heat exchanger 10, and both ends of the circulation oil pipeline are respectively connected to both ends of the stack 1.

[0024] See Figure 1 and Figure 2 As shown, in the embodiment of the present invention, carbon dioxide hydrogenation to methanol reactor inlets C and outlets D are respectively arranged at both ends of the carbon dioxide hydrogenation to methanol reactor 3. The carbon dioxide hydrogenation to methanol reactor inlet C is connected to an intake pipeline; the carbon dioxide hydrogenation to methanol reactor outlet D is sequentially connected to a gas cooler 17 and a methanol aqueous solution recovery tank 18 through pipelines.

[0025] See Figure 3As shown, in the embodiment of the present invention, the electrolyzed water module includes an electrolytic cell 14 and a solar panel 15 connected to the electrolytic cell 14. The solar panel 15 converts solar energy into direct current electrical energy and inputs the generated direct current electrical energy into the electrolytic cell 14 to electrolyze the recycled water in the electrolytic cell 14, and an electrochemical reaction occurs. An electrolytic cell hydrogen side outlet E and an electrolytic cell oxygen side outlet F are respectively provided on both sides of the electrolytic cell 14. The hydrogen generated at the cathode of the electrolytic cell 14 is discharged from the electrolytic cell hydrogen side outlet E, mixed with the anode tail gas of the fuel cell stack 1, pressurized by a compressor 16, and then introduced into the carbon dioxide hydrogenation to methanol reactor 3. The oxygen generated at the anode of the electrolytic cell 14 is discharged through the electrolytic cell oxygen side outlet F, mixed with the cathode intake gas of the fuel cell stack 1, and reused as the cathode oxidant of the fuel cell stack.

[0026] See Figure 4 As shown, in the embodiment of the present invention, the electrolyzed water module can also be composed of an electrolytic cell 14 and a wind turbine 20 connected to the electrolytic cell 14. The wind turbine 20 converts the wind energy of each cooling fan in the system's circulating oil radiator 11, gas cooler 17, and fuel cell stack cathode tail gas cooler and the external wind energy into direct current electrical energy, inputs the generated direct current electrical energy into the electrolytic cell 14, electrolyzes the recycled water in the electrolytic cell 14, and an electrochemical reaction occurs.

[0027] A high-temperature methanol reforming fuel cell system for realizing carbon cycle provided by an embodiment of the present invention has the following working principle: In the startup stage of the fuel cell system, a lithium battery is used to drive a heater to heat the fuel cell stack 1, the methanol steam reforming hydrogen production reactor 2, and the carbon dioxide hydrogenation to methanol reactor 3 to the operating temperature. Then, the fuel methanol aqueous solution is pumped into the coupled heat exchanger 10, evaporated by using the heat of the circulating heat transfer oil, and then introduced into the methanol steam reforming hydrogen production reactor 2 to carry out the methanol reforming hydrogen production reaction. The hydrogen-rich gas after the reaction is introduced into the anode of the fuel cell stack, and the cathode of the fuel cell stack is fed by an air pump. Hydrogen and oxygen undergo an electrochemical reaction in the fuel cell stack to generate external power supply.

[0028] In the stable operation stage of the fuel cell system, the anode tail gas of the fuel cell stack is introduced into the compressor 16, pressurized to ~3 MPa, and then introduced into the carbon dioxide hydrogenation to methanol reactor 3 to carry out the methanol production reaction. The reaction is an exothermic reaction, which can provide heat source for the reforming hydrogen production, maintain the temperature of the two beds, and reduce the external heating power consumption.

[0029] For the fuel cell system, the reaction gas discharged from the carbon dioxide hydrogenation to methanol reactor 3 can obtain a methanol aqueous solution after cooling and vapor-liquid separation; after distillation, impurity removal, liquid addition and other treatments, the concentration of the methanol aqueous solution is adjusted to be the same as the concentration of the imported fuel, and it is reused as fuel, realizing the carbon (carbon dioxide) cycle, reducing carbon dioxide emissions, and at the same time realizing the hydrogen (hydrogen) cycle. Through the carbon and hydrogen cycles, the energy utilization efficiency of the system is improved.

[0030] The fuel cell system is equipped with an electrolyzed water module. The liquid water recovered from the cathode exhaust gas of the fuel cell stack is introduced into the electrolytic cell 14. Externally, solar power is used to electrolyze the recovered water in the electrolytic cell 14. Hydrogen generated at the cathode of the electrolytic cell is mixed with the anode exhaust gas of the fuel cell stack and then introduced into the carbon dioxide hydrogenation to methanol reactor 3 through a compressor 16 to carry out the methanol synthesis reaction, thus making up for the disadvantage of insufficient hydrogen when only using the anode exhaust gas of the fuel cell stack to produce methanol, and converting most of the carbon dioxide back into methanol. In the fuel cell system, the oxygen generated at the anode of the electrolytic cell is mixed with the cathode intake gas of the fuel cell stack and reused as the cathode oxidant of the fuel cell stack, realizing the circulation of oxygen (oxygen), reducing the air pump supply flow rate, that is, reducing the power consumption of the air pump.

[0031] Another embodiment of the present invention provides an operation process of a high-temperature methanol reforming fuel cell system for realizing carbon cycle. By utilizing the exhaust gas of the fuel cell stack 1 in the system to produce methanol, the methanol steam reforming to hydrogen reactor 2 and the carbon dioxide hydrogenation to methanol reactor 3 are thermally coupled designed to realize the circulation of carbon and fuel and the efficient utilization of internal heat, reducing the carbon emissions of the methanol fuel cell system; at the same time, combined with the electrolyzed water module, the water recovered from the exhaust gas of the fuel cell stack in the system is electrolyzed to produce hydrogen as the raw material for carbon dioxide hydrogenation to methanol, and the oxygen electrolyzed from the water is reused as the oxidant of the cathode of the fuel cell stack 1. Through the circulation of carbon, hydrogen, and oxygen, the energy utilization efficiency of the system is improved. Embodiment

[0032] See Figure 1 As shown, for a high-temperature methanol reforming fuel cell system for realizing carbon cycle provided by the present invention, in the startup stage, a lithium battery is used to drive the circulating oil electrothermal heater 9 to heat the circulating heat transfer oil of the fuel cell stack, thereby heating the fuel cell stack 1 to the operating temperature of 160 °C. At the same time, the reactor bed electrothermal heater 12 heats the methanol steam reforming to hydrogen reactor 2 and the carbon dioxide hydrogenation to methanol reactor 3 to their bed temperature of 300 °C. See Figure 2As shown, the beds of the methanol steam reforming hydrogen production reactor 2 and the carbon dioxide hydrogenation to methanol reactor 3 are coupled and integrally connected, enabling heat transfer between them. There is an electric heater 12 in the reactor bed in the middle, mainly used for startup heating. After reaching the temperature condition, 60 vol% methanol aqueous solution fuel 6 in the methanol aqueous solution fuel tank 4 is pumped into the coupling heat exchanger 10 by the liquid pump 6. After being evaporated using the heat of the circulating heat transfer oil, it is introduced into the methanol steam reforming hydrogen production reactor 2 from the inlet A of the methanol steam reforming hydrogen production reactor, and the methanol reforming hydrogen production reaction occurs, as shown in formula (1). This reaction is an endothermic reaction. After the reaction, the hydrogen-rich gas (~65% hydrogen, ~21% carbon dioxide, ~13% water vapor, ~1% carbon monoxide, etc.) is discharged from the outlet B of the methanol steam reforming hydrogen production reactor, cooled to ~160 °C in the coupling heat exchanger 10, and then introduced into the anode of the fuel cell stack 1. The cathode of the fuel cell stack 1 is supplied with materials by the air pump 7, and the electrochemical reaction (2) occurs between hydrogen and oxygen in the fuel cell stack 1 to achieve external power supply; The chemical reaction equations for the above methanol steam reforming hydrogen production method are as follows: CH3OH + H2O → CO2 + 3H2 ∆H 298 = 49.5 kJ·mol - 1 (1) The chemical reaction equations in the above fuel cell stack are as follows: 2H2 + O2 → 2H2O (2) See Figure 1 As shown, during the stable operation stage of the system, since the anode of the fuel cell stack 1 is supplied with hydrogen-rich gas instead of pure hydrogen, to ensure the power generation performance of the fuel cell stack 1, usually hydrogen-rich gas with a stoichiometric ratio of 1.15 - 1.4 times that of hydrogen is used at the anode. For example, after introducing hydrogen-rich gas with a stoichiometric ratio of 1.3 times that of hydrogen into the anode of the fuel cell stack 1, the anode tail gas composition of the fuel cell stack 1 is ~30% hydrogen, ~42% carbon dioxide, ~26% water vapor, ~2% carbon monoxide. The anode tail gas of the fuel cell stack 1 is introduced into the compressor 16, pressurized to 3 MPa, and then introduced into the carbon dioxide hydrogenation to methanol reactor 3 from the inlet C of the carbon dioxide hydrogenation to methanol reactor, and the methanol synthesis reaction occurs, as shown in formula (3). The carbon dioxide hydrogenation to methanol reaction is an exothermic reaction, which can provide heat source for the reforming hydrogen production and maintain the reaction temperature of the two beds at the same time. See Figure 2As shown in the figure. During stable operation, the external bed heating can be stopped or intermittently turned on, significantly reducing the heating power consumption of the external reactor bed electric heater 12. The reaction gas is discharged from the outlet D of the carbon dioxide hydrogenation to methanol reactor, cooled by the gas cooler 17, separated by the gas-liquid separator, and then enters the methanol aqueous solution recovery tank 18 to obtain the methanol aqueous solution. After distillation, impurity removal, liquid addition and other treatments, the concentration is adjusted to 60vof% methanol aqueous solution consistent with the inlet fuel concentration and reused as fuel, realizing the carbon (carbon dioxide) cycle, reducing carbon dioxide emissions, and at the same time realizing the hydrogen (hydrogen) cycle. Through the carbon and hydrogen cycles, the energy utilization efficiency of the system is improved.

[0033] CO2 + 3H2 → CH3OH + H2O ∆H 298 = -49.5 kJ·mol - 1 (3) See Figure 1 As shown in the figure, since the fuel cell stack 1 consumes most of the hydrogen and generates water, the hydrogen in the anode tail gas of the fuel cell stack 1 for carbon dioxide hydrogenation to methanol is not enough to convert most of the carbon dioxide into methanol. Therefore, the system of the present invention recovers water from the cathode tail gas of the fuel cell stack 1, and at the same time assembles the electrolytic cell 14 for electrolyzing water to produce hydrogen. The recovered liquid water is introduced into the electrolytic cell 14. Externally, the solar energy is converted into direct current by the solar panel 15 through the photovoltaic effect, or the wind energy of each radiator fan in the system and the external wind energy are converted into direct current by the wind turbine 20. The generated direct current is input into the electrolytic cell 14 to electrolyze the recovered water in the electrolytic cell 14, and an electrochemical reaction occurs, formula (4), see Figure 3 and Figure 4 As shown in the figure; the hydrogen generated at the cathode of the electrolytic cell 14 is discharged from the hydrogen side outlet E of the electrolytic cell and mixed with the anode tail gas of the fuel cell stack 1, then pressurized to ~3MPa and introduced into the carbon dioxide hydrogenation to methanol reactor 3 to carry out the methanol production reaction, thus making up for the disadvantage of insufficient hydrogen when only using the anode tail gas of the fuel cell stack 1 to produce methanol, and converting most of the carbon dioxide back into methanol. When a little water is added under the allowable external conditions, all the carbon dioxide can be converted into methanol, realizing zero carbon dioxide emissions; at the same time, the oxygen generated at the anode of the electrolytic cell 14 is discharged from the oxygen side outlet F of the electrolytic cell and mixed with the cathode intake air of the fuel cell stack 1, and reused as the cathode oxidant of the fuel cell stack 1, realizing the oxygen (oxygen) cycle and reducing the cathode air supply flow rate, that is, reducing the power consumption of the air pump 7. The above system and operation process not only realize the carbon (carbon dioxide) cycle in the high-temperature methanol fuel cell system, reduce carbon dioxide emissions, but also realize the hydrogen (hydrogen) and oxygen (oxygen) cycles. Through the carbon, hydrogen and oxygen cycles, the energy utilization efficiency of the system is jointly improved.

[0034] The chemical reaction equations in the above electrolytic cell are as follows: 2H2O → 2H2 + O2 (4) The fuel cell system of the present invention carries 100 L of methanol aqueous solution (60% by volume concentration), maintains the bed temperature of the methanol steam reforming hydrogen production reactor at 220 - 300 °C, the bed temperature of the carbon dioxide hydrogenation to methanol reactor at 270 - 350 °C, the stack temperature at 160 - 165 °C, and the circulating oil temperature at 150 - 155 °C. At a fuel flow rate of 170 mL / min of methanol aqueous solution and a stack of 400 mA / cm 2 At the operating point, the rated output power is 11 kW, the stable operating time is ~10 h, and the CO2 (carbon dioxide) emission is ~34.6 m 3 , and the system energy utilization efficiency can reach ~40%; when the water recovery, electrolyzer and other modules are not turned on in the system, the CO2 recovery amount is 5 - 7 m 3 , the CO2 recovery rate is 15 - 20%, 15 - 20 L of methanol aqueous solution (60% by volume concentration) can be recycled and modulated, the stable operating time is extended to 11.5 - 12 h, and the system energy utilization efficiency can reach 47 - 50%; when the water recovery, electrolyzer and other modules are turned on in the system, the CO2 recovery amount is 19 - 30 m 3 , the CO2 recovery rate is 55 - 90%, 55 - 90 L of methanol aqueous solution (60% by volume concentration) can be recycled and modulated, the stable operating time is extended to 15.5 - 19 h, and the system energy utilization efficiency can reach over 90%.

[0035] A high-temperature methanol reforming fuel cell system and operation process for realizing carbon cycle provided by the present invention is a high-temperature proton exchange membrane fuel cell (HT-PEMFC) system that uses hydrogen-rich gas produced by methanol steam reforming to produce hydrogen as the fuel for the stack; by recycling and reusing the CO2 (carbon dioxide) and H2 (hydrogen) in the stack tail gas of the system to produce methanol, combining methanol reforming to produce hydrogen with its reverse reaction of carbon dioxide hydrogenation to methanol in the system, and combining the internal heat coupling design of the system, the cycle of carbon and fuel and the efficient utilization of internal heat are realized, reducing the carbon emission of the methanol fuel cell system; at the same time, combining the electrolysis function of solar power generation module to electrolyze the water recovered from the stack tail gas of the system to produce hydrogen, which is used as the raw material for carbon dioxide hydrogenation to methanol, and the oxygen produced by water electrolysis is used as the oxidant for the cathode of the stack again. The above cycles of C (carbon dioxide), H (hydrogen), and O (oxygen) reduce the carbon emission of the high-temperature methanol reforming fuel cell system and improve the system energy utilization efficiency at the same time.

[0036] The above is only the implementation mode of the present invention, and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, expansion, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A high-temperature methanol reforming fuel cell system for realizing carbon cycle, characterized in that, It includes a fuel cell stack (1), a methanol steam reforming hydrogen production reactor (2), a carbon dioxide hydrogenation to methanol reactor (3), and an electrolyzed water module; The hydrogen produced by the methanol steam reforming hydrogen production reactor (2) enters the anode of the fuel cell stack (1) through a pipeline. The cathode of the fuel cell stack (1) is fed by an air pump (7). Hydrogen and oxygen undergo an electrochemical reaction in the fuel cell stack (1) to achieve external power supply; The liquid water recovered from the cathode tail gas of the fuel cell stack (1) is introduced into the electrolyzed water module to electrolyze water to produce hydrogen; The carbon dioxide in the anode tail gas of the fuel cell stack (1) and the hydrogen produced by the electrolyzed water module enter the carbon dioxide hydrogenation to methanol reactor (3) through an inlet pipeline to produce methanol.

2. The high-temperature methanol reforming fuel cell system for realizing carbon cycle according to claim 1, wherein The methanol steam reforming hydrogen production reactor (2) and the carbon dioxide hydrogenation to methanol reactor (3) are coupled into an integrated structure, and a reactor bed electric heater (12) is arranged between the methanol steam reforming hydrogen production reactor (2) and the carbon dioxide hydrogenation to methanol reactor (3). During the start-up stage of the system, the reactor bed electric heater (12) provides heat sources for the methanol steam reforming hydrogen production reactor (2) and the carbon dioxide hydrogenation to methanol reactor (3); during the stable operation stage of the system, the reactor bed electric heater (12) is turned off. The carbon dioxide hydrogenation to methanol reactor (3) undergoes a methanol production reaction, and the reaction is an exothermic reaction that provides a heat source for reforming hydrogen production, maintaining the temperatures of the two beds and reducing the external heating power consumption.

3. The high-temperature methanol reforming fuel cell system for realizing carbon cycle according to claim 1, wherein Both ends of the methanol steam reforming hydrogen production reactor (2) are respectively provided with a methanol steam reforming hydrogen production reactor inlet (A) and a methanol steam reforming hydrogen production reactor outlet (B). The methanol steam reforming hydrogen production reactor inlet (A) is connected to a liquid pump (6) and a methanol aqueous solution fuel tank (4) through a pipeline. The methanol steam reforming hydrogen production reactor outlet (B) is connected to the anode of the fuel cell stack (1) through a pipeline. A coupling heat exchanger (10) is arranged on the two pipelines connected to the methanol steam reforming hydrogen production reactor inlet (A) and the methanol steam reforming hydrogen production reactor outlet (B).

4. The high-temperature methanol reforming fuel cell system for realizing carbon cycle according to claim 3, characterized in that It also includes a heating circulation system; the heating circulation system includes a circulation oil pump (8), a circulation oil electric heater (9), and a circulation oil radiator (11) that are sequentially connected through a circulation oil pipeline. The circulation oil pipeline passes through the coupling heat exchanger (10), and both ends of the circulation oil pipeline are respectively connected to both ends of the fuel cell stack (1).

5. The high-temperature methanol reforming fuel cell system for realizing carbon cycle according to claim 1, characterized in that, Both ends of the carbon dioxide hydrogenation to methanol reactor (3) are respectively provided with a carbon dioxide hydrogenation to methanol reactor inlet (C) and a carbon dioxide hydrogenation to methanol reactor outlet (D). The carbon dioxide hydrogenation to methanol reactor inlet (C) is connected to the inlet pipeline; the carbon dioxide hydrogenation to methanol reactor outlet (D) is sequentially connected to a gas cooler (17) and a methanol aqueous solution recovery tank (18) through a pipeline.

6. The high-temperature methanol reforming fuel cell system for realizing carbon cycle according to claim 1, wherein, The electrolyzed water module includes an electrolytic cell (14) and a solar power panel (15) connected to the electrolytic cell (14). The solar power panel (15) converts solar energy into direct current electrical energy, and inputs the generated direct current electrical energy into the electrolytic cell (14) to electrolyze the recycled water in the electrolytic cell (14) to cause an electrochemical reaction. The hydrogen generated at the cathode of the electrolytic cell (14) is mixed with the anode tail gas of the fuel cell stack (1), pressurized by a compressor (16), and then input into the carbon dioxide hydrogenation to methanol reactor (3).

7. The high-temperature methanol reforming fuel cell system for realizing carbon cycle according to claim 1, characterized in that The electrolyzed water module includes an electrolytic cell (14) and a wind turbine (20) connected to the electrolytic cell (14). The wind turbine (20) converts the wind energy of each radiator fan in the system and the external wind energy into direct current electrical energy, and inputs the generated direct current electrical energy into the electrolytic cell (14) to electrolyze the recycled water in the electrolytic cell (14) to cause an electrochemical reaction. The hydrogen generated at the cathode of the electrolytic cell (14) is mixed with the anode tail gas of the fuel cell stack (1), pressurized by a compressor (16), and then input into the carbon dioxide hydrogenation to methanol reactor (3).

8. The high-temperature methanol reforming fuel cell system for realizing carbon cycle according to claim 6 or 7, characterized in that, The oxygen generated at the anode of the electrolytic cell (14) is mixed with the cathode intake gas of the fuel cell stack (1) and reused as the cathode oxidant of the fuel cell stack.

9. The high-temperature methanol reforming fuel cell system for realizing carbon cycle according to claim 1, characterized in that The cathode tail gas of the fuel cell stack (1) is sequentially connected to a cathode tail gas cooler (19), a gas-liquid separator (5), and a water tank (13) through pipelines. The water tank (13) is connected to the electrolyzed water module through pipelines.

10. An operating process of a high-temperature methanol reforming fuel cell system for realizing carbon cycle as described in any one of claims 1-9, characterized in that, By utilizing the tail gas of the fuel cell stack (1) in the system to produce methanol, a thermal coupling design is carried out for the methanol steam reforming to hydrogen reactor (2) and the carbon dioxide hydrogenation to methanol reactor (3) to realize the cycle of carbon and fuel and the efficient utilization of internal heat, reducing the carbon emission of the methanol fuel cell system; at the same time, combined with the electrolyzed water module, the recycled water in the tail gas of the system fuel cell stack is electrolyzed to produce hydrogen as the raw material for carbon dioxide hydrogenation to methanol, and the oxygen electrolyzed from water is reused as the oxidant of the cathode of the fuel cell stack (1). Through the cycle of carbon, hydrogen, and oxygen, the energy utilization efficiency of the system is improved.

Images