System and method for producing hydrogen by coupling electrolyzed water with hydrocarbon fuel

Abstract

The system comprises an electrolysis module, a water supply part and a hydrocarbon fuel supply part, and is characterized in that the electrolysis module comprises a cathode inlet, an anode inlet, a cathode outlet and an anode outlet; the water supply part is sequentially connected with a first water pump, a first steam generator, a first heat exchanger, a first heater and a cathode inlet; the cathode outlet is connected with the cathode inlet through the first ejector in sequence, the cathode outlet is connected with the first heat exchanger, the first condenser and the hydrogen storage part in sequence, and the hydrogen storage part is connected with the first heat exchanger through the first mass flow meter; and the hydrocarbon fuel supply part is sequentially connected with a second mass flow meter, a second heat exchanger, a second heater and an anode inlet. According to the invention, the strong endothermic reaction of hydrocarbon fuel oxidation is utilized to compensate the strong endothermic electrolyzed water reaction of the cathode in situ, so that the electric energy consumption of the electrolysis module is greatly reduced, meanwhile, the operating temperature of the electrolysis module is reduced, and the service life is greatly prolonged.

Description

Technical Field

[0001] The present invention relates to a hydrogen production system and method, and in particular to a water electrolysis coupled hydrocarbon fuel hydrogen production system and method. Background Art

[0002] The main sources of hydrogen required for current industrial production include fossil fuel reforming and water electrolysis. The former has a large amount of greenhouse gas emissions. Water electrolysis hydrogen production technologies include alkaline electrolysis (ALK), proton exchange membrane electrolysis (PEM) and solid oxide electrolysis (SOEC). SOEC is a high-temperature electrolysis method. Water vapor decomposes into hydrogen and oxygen at a temperature of 700-1000°C. Compared with low-temperature electrolysis such as ALK and PEM, it has higher electrolysis efficiency and lower energy consumption; the SOEC water electrolysis hydrogen production system includes two major parts: an electrolysis module and a thermal management system. The electrolysis module mainly produces water vapor electrolysis reaction. Since the water vapor electrolysis reaction is a strongly endothermic reaction, this part of the energy consumption accounts for more than 80% of the total energy consumption of the system. The thermal management system provides the necessary thermal environment and water vapor for the electrolysis module. This part of the energy consumption accounts for less than 20% of the total energy consumption of the system.

[0003] At present, the relevant industries in my country have just started, with high system energy consumption and low integration. Many scientific research institutions and R&D enterprises are constantly reducing the system energy consumption of SOEC. CN118345405A arranges heat exchange components in the thermal management system to recover the heat at the outlet of the system for evaporating water vapor and preheating the inlet gas, reducing the power consumption of the system; CN118547302A and CN118048642A are equipped with ejectors on the steam input side (hydrogen pipeline) in addition to arranging heat exchange components, reducing the system's demand for hydrogen accompanying carrier gas, thereby reducing the energy consumption for heating this part of hydrogen, and further reducing the power consumption of the system. However, these improvements all occur in the thermal management system. As mentioned above, the energy consumption of the thermal management system only accounts for less than 20% of the total energy consumption of the system, so the degree of reduction in the overall hydrogen production energy consumption of the system is limited. Therefore, reducing the energy consumption of the electrolysis module is the key to reducing the energy consumption of the SOEC hydrogen production system and helping the development of the SOEC industry. Summary of the invention

[0004] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a water electrolysis coupled hydrocarbon fuel hydrogen production system with high raw material utilization rate. Another purpose of the present invention is to provide an energy-saving water electrolysis coupled hydrocarbon fuel hydrogen production method.

[0005] Technical solution: The present invention discloses a system for producing hydrogen by electrolyzing water and coupling hydrocarbon fuels, which is characterized in that it comprises an electrolysis module, a water supply unit, and a hydrocarbon fuel supply unit. The electrolysis module comprises a cathode inlet, an anode inlet, a cathode outlet, and an anode outlet. The water supply unit is connected to a first water pump, a first steam generator, a first heat exchanger, a first heater, and a cathode inlet in sequence; the cathode outlet is connected to the cathode inlet in sequence through a first ejector, the cathode outlet is connected to a first heat exchanger, a first condenser, and a hydrogen storage unit in sequence, and the hydrogen storage unit is connected to the first heat exchanger through a first mass flow meter; the hydrocarbon fuel supply unit is connected to a second mass flow meter, a second heat exchanger, a second heater, and an anode inlet in sequence; the water supply unit is connected to a second water pump, a second steam generator, and a second heat exchanger in sequence; the anode outlet is connected to the anode inlet through a second ejector; the anode outlet is connected to an exhaust gas processor, a second heat exchanger, a second condenser, and a carbon dioxide storage unit in sequence.

[0006] Furthermore, the tail gas processor is connected to the oxygen generator, which supplies oxygen to the tail gas processor so that the hydrocarbon fuel can be completely oxidized after passing through the electrolysis module. An oxygen sensor is installed in the tail gas processor to monitor the oxygen content in the tail gas processor and feed it back to the oxygen generator to control the oxygen content in the tail gas processor to be lower than 100ppm. The gas that does not enter the cycle is mixed and reacted with the oxygen generated by the oxygen generator at the tail gas processor to react a small amount of H2 produced in the mixed gas (due to incomplete reaction), and the oxygen content of the mixed gas is monitored by the oxygen sensor until the H2 is completely reacted.

[0007] Furthermore, the condensed liquid water of the first condenser and the second condenser flows back to the water supply part.

[0008] Furthermore, the heating temperature of the first heater and the second heater is 400-1000°C, preferably 500-650°C. Furthermore, the temperature of the first steam generator and the second steam generator is set to 120-150°C.

[0009] Furthermore, the first ejector has an ejection coefficient of 0.1 to 0.2, which is used to eject a portion of the high-temperature hydrogen and water vapor at the hydrogen outlet for reflux. At this time, there is no need for the hydrogen storage unit to provide hydrogen to the cathode inlet, and all hydrogen is provided by ejection reflux.

[0010] Furthermore, the second ejector has an ejection coefficient of 3 to 4, which is used to eject the carbon dioxide and water vapor products at the carbon dioxide outlet. At this time, the water tank no longer provides water to the anode inlet, but all water is provided by the ejected reflux carbon dioxide and water vapor.

[0011] Furthermore, it also includes a hydrogen storage unit, which is connected to the first heat exchanger.

[0012] Furthermore, the first heat exchanger includes port A, port B, port C, and port D. The output end of the first mass flow meter and the output end of the first steam generator are connected to port A, the input end of the first heater is connected to port B, the cathode outlet is connected to port C, and the input end of the first condenser is connected to port D.

[0013] Furthermore, the second heat exchanger includes an E port, an F port, a G port, and an H port. The output end of the second steam generator and the output end of the second mass flow meter are both connected to the E port, the input end of the second heater is connected to the F port, the output end of the exhaust gas processor is connected to the G port, and the input end of the second condenser is connected to the H port.

[0014] The method for producing hydrogen by electrolyzing water and coupling hydrocarbon fuels according to the present invention comprises the following steps:

[0015] Step 1, startup phase: the water in the water supply unit turns into water vapor, mixes with the hydrogen output from the hydrogen storage unit, and undergoes heat exchange and temperature rise, and finally heats to a reaction temperature of 400-1000°C, and then enters the electrolysis module for cathode electrolysis reaction; the water in the water supply unit evaporates into water vapor, mixes with the hydrocarbon fuel output from the hydrocarbon fuel supply unit, and undergoes heat exchange and temperature rise, and finally heats to a reaction temperature of 400-1000°C, and then enters the electrolysis module for anode electrolysis reaction;

[0016] Step 2, steady-state operation stage: the tail gas discharged from the electrolysis module is circulated proportionally, and part of the tail gas is circulated to the cathode inlet and the anode inlet according to the corresponding ejection coefficient. At this time, the hydrogen storage unit stops supplying hydrogen to the cathode inlet, and the water supply unit stops supplying water vapor to the anode inlet.

[0017] The recovered carbon dioxide can be used as a supplementary gas to replace part of the water vapor as a carrier gas, which plays a role in saving energy. In the stable stage, the gas circulated back from the tail exhaust by the ejector supplements part of the H2 and water vapor required by the inlet. The anode does not need to obtain water vapor from the water supply part, but circulates part of the water vapor and CO2 generated by the anode back to the inlet through the ejector to provide the required energy and materials, which plays a role in saving energy.

[0018] Working principle: water vapor is introduced into the cathode and hydrogen is discharged, while hydrocarbon fuel is introduced into the anode and carbon dioxide and water vapor are discharged. In the electrolysis module reaction of the above system, if an example is needed, methane is used as an example of hydrocarbon fuel, and the following is similar and will not be repeated. In a stable electrolysis reaction, the cathode reaction equation is as follows:

[0019] 4H2O+8e - →4H2+4O 2-

[0020] The anode reaction equation is as follows:

[0021] CH4+4O 2- →CO2+2H2O+8e -

[0022] The overall reaction equation is as follows:

[0023] CH4(c)+4H2O(a)→2H2O(c)+CO2(c)+4H2(a).

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0025] 1. The hydrocarbon fuel oxidation reaction at the anode of the electrolysis module is a strongly endothermic reaction. The energy released by the reaction can in situ compensate for the strongly endothermic water electrolysis reaction at the cathode, greatly reducing the power consumption of the electrolysis module. The power consumption in the electrolysis module of the present invention can be reduced to 1 / 3 to 1 / 4 of the prior art;

[0026] 2. The operating temperature of the core electrolytic module of the system can be preferably set at 500-650°C. Compared with the prior art, the operating temperature of the electrolytic module is lowered, the thermal tolerance of the entire system can be improved, and the difficulty of heat utilization is effectively reduced; at the same time, the requirements for the core electrolytic module and system component materials are reduced, which greatly improves the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a connection diagram of the present invention. DETAILED DESCRIPTION

[0028] like Figure 1 The electrolytic water coupled hydrocarbon fuel hydrogen production system comprises an electrolytic module 1, a water supply unit 2, a hydrocarbon fuel supply unit 3, a hydrogen storage unit 21 and a carbon dioxide storage unit 22. The electrolytic module 1 comprises a cathode inlet 101, an anode inlet 102, a cathode outlet 103, and an anode outlet 104, and inlet and outlet pressure sensors and temperature sensors are provided on both sides to ensure that the inlet and outlet gas temperatures are within the required range (preferably 500-650°C), and the inlet and outlet pressure difference is within the range that the electrolytic module can withstand.

[0029] The water supply part provides the required water vapor in two ways. The first route is connected to the cathode inlet 101, and is connected to the water supply part 2, the first water pump 4, and the first steam generator 5 in sequence through pipelines. The water vapor output by the first steam generator 5 enters along the A port of the first heat exchanger 6, and is connected to the first heater 7 and the cathode inlet 101 in sequence through the B port; the second route is connected to the anode inlet 102, and is connected to the water supply part 2, the second water pump 14, and the second steam generator 15 in sequence through pipelines. The water vapor output by the second steam generator 15 enters along the E port of the second heat exchanger 12, and is connected to the second heater 13 and the anode inlet 102 in sequence through the F port.

[0030] The hydrocarbon fuel supplied by the hydrocarbon fuel supply unit 3 is mixed with the water vapor generated by the second steam generator 15 through the second mass flow meter 11, and then enters along the E port of the second heat exchanger 12, and is sequentially connected to the second heater 13 and the anode inlet 102 through the F port. The hydrogen output by the hydrogen storage unit 21 is mixed with the water vapor generated by the first steam generator 5 through the first mass flow meter 10, and then enters along the A port of the first heat exchanger 6, and is sequentially connected to the first heater 7 and the cathode inlet 101 through the B port.

[0031] Condensed water is recovered, and the liquid water after the reaction product hydrogen and carbon dioxide and water vapor mixture are condensed is returned to the water supply unit 2 for reuse. The cathode outlet 103 is connected to the first ejector 8 and the cathode inlet 101 in sequence through a pipeline, and the cathode outlet 103 is connected to the first heat exchanger 6, the first condenser 9, and the hydrogen storage unit 21 in sequence through a pipeline. The hydrogen output from the cathode outlet 103 enters along the C port of the first heat exchanger 6 and is output from the D port. The anode outlet 104 is connected to the second ejector 16 and the anode inlet 102 in sequence through a pipeline. The anode outlet 104 outputs carbon dioxide and water vapor through the exhaust gas processor 17, enters along the G port of the second heat exchanger 12, and is output from the H port, connected to the second condenser 18 and the carbon dioxide storage unit 22. The exhaust gas processor 17 is connected to the oxygen generator 19, and the oxygen generator 19 supplies oxygen to the exhaust gas processor 17 so that the hydrocarbon fuel can be completely oxidized after passing through the electrolysis module. An oxygen sensor 20 is installed in the exhaust gas processor 17 to monitor the oxygen content in the exhaust gas processor 17 and feed it back to the oxygen generator 19, so as to control the oxygen content in the exhaust gas processor 17 to be lower than 100ppm.

[0032] The hydrogen production method of the water electrolysis coupled hydrocarbon fuel hydrogen production system of this embodiment includes the following steps:

[0033] 1. Start-up phase of water electrolysis coupled with hydrocarbon fuel hydrogen production system:

[0034] The cathode inlet 101 is ventilated. The electrolysis module 1 is heated to a preset temperature of 600°C, and hydrogen begins to be introduced. The first mass flowmeter 10 adjusts the air intake to 500L / h, and hydrogen enters the system. The first water pump 4 is continuously started, and the ratio of water vapor to hydrogen introduced into the cathode inlet 101 is 4:1, driving liquid water with a flow rate of 1607g / h to enter the first steam generator 5, and evaporate the liquid water into water vapor at 120-150°C. The mixed water vapor and hydrogen pass through the first heat exchanger 6, and exchange heat with the exhaust gas discharged from the cathode outlet 103. After absorbing the waste heat of the tail gas, it is heated to 600°C by the first heater 7 and enters the electrolysis module 1 for electrolysis reaction.

[0035] The tail gas is discharged from the cathode outlet 103. The gas generated at the cathode outlet 103 mainly includes a mixture of hydrogen and water vapor, of which about 25% is circulated to the cathode inlet 101 through the first ejector 8 to prevent oxidation of the cathode catalyst of the electrolysis module, and the remaining 75% is provided with heat exchange with the incoming hydrogen and water vapor mixture through the first heat exchanger 6, and then condensed and separated into liquid water and hydrogen through the first condenser 9, and the liquid water is returned to the water tank for continued use, and the hydrogen enters the hydrogen storage unit 21.

[0036] The anode inlet 102 is ventilated. After the electrolysis module 1 reaches the preset temperature of 600°C, methane is introduced into the system, and the second mass flowmeter 11 adjusts the air intake to 500L / h. The second water pump 14 is continuously started, and the ratio of water vapor to methane introduced into the anode inlet 102 is 2.5:1, driving liquid water with a flow rate of 952g / h to enter the second steam generator 15, and evaporate the liquid water into water vapor at 120-150°C. The mixed mixed gas (water vapor and methane) passes through the second heat exchanger 12, exchanges heat with the exhaust gas discharged from the anode outlet 104, absorbs the waste heat of the tail gas, and is then heated to 600°C by the second heater 13, and enters the electrolysis module 1 for oxidation reaction.

[0037] The tail gas is discharged from the anode outlet 104. The gas generated at the anode outlet 104 includes carbon dioxide, water vapor and a small amount of hydrogen. Through the second ejector 16, about 45% of the mixed gas is circulated back to the anode inlet 102 to provide an appropriate amount of carrier gas for the anode inlet 102. The remaining gas that has not entered the cycle is mixed and reacted with the oxygen generated by the oxygen generator 19 at the tail gas processor 17 to react the hydrogen in the mixed gas, and the oxygen content of the mixed gas is monitored by the oxygen sensor 20 until the hydrogen is completely reacted. The gas treated by the tail gas processor 17 provides heat exchange for the anode inlet 102 intake through the second heat exchanger 12, and then condenses and separates through the second condenser 18. The separated water flows back into the water supply part 2 for use, and the separated carbon dioxide enters the carbon dioxide storage part 22.

[0038] 2. The stable stage of water electrolysis coupled with hydrocarbon fuel hydrogen production system:

[0039] When the gases at the cathode inlet 101 and the anode inlet 102 are introduced into the electrolysis module 1 according to the design requirements and react normally, the system enters a stable reaction state.

[0040] The cathode inlet 101 reacts. At this time, the first water pump 4 continues to be turned on, and enters the first heat exchanger 6 and the first heater 7 through the first evaporator 5 for heating. The hydrogen storage unit 21 stops supplying hydrogen to the cathode inlet 101, but the hydrogen of the circulated tail gas from the first ejector 8 is provided back to the cathode inlet 101. The circulation rate is 25%. The hydrogen and water vapor mixture passes through the first heater 7 and the first ejector 8 and enters the cathode inlet 101 of the electrolysis module 1 for electrolysis reaction. The ejection coefficient of the first ejector 8 is 0.1-0.2. The hydrogen and water vapor mixture that has not entered the cycle passes through the first heat exchanger 6, and then passes through the first condenser 9 for gas-liquid separation. The cooling water circulates back to the water supply unit 2, and the hydrogen enters the hydrogen storage unit 21.

[0041] The anode inlet 102 reacts. The second water pump 14 is turned off, and the water vapor at the anode inlet 102 is provided by the carbon dioxide and water vapor mixed gas discharged from the second ejector 16 circulating tail gas, with a circulation rate of 45%, and the ejection coefficient of the second ejector 16 is 3-4. The hydrocarbon fuel supply unit 3 continues to provide methane at 500L / h, and the two are mixed and enter the anode inlet 102 for oxidation reaction. The remaining anode outlet tail gas that has not entered the circulation enters the carbon dioxide storage unit 22.

[0042] The above is the process of the system from startup to stable electrolysis hydrogen production reaction.

Claims

1. A water electrolysis coupled hydrocarbon fuel hydrogen production system, characterized in that: The hydrogen production system comprises an electrolysis module (1), a water supply unit (2), a hydrocarbon fuel supply unit (3), a hydrogen storage unit (21) and a carbon dioxide storage unit (22); the electrolysis module (1) comprises a cathode inlet (101), an anode inlet (102), a cathode outlet (103) and an anode outlet (104); the water supply unit (2) is sequentially connected to a first water pump (4), a first steam generator (5), a first heat exchanger (6), a first heater (7) and a cathode inlet (101); the cathode outlet (103) is sequentially connected to the cathode inlet (101) via a first ejector (8); the cathode outlet (103) is sequentially connected to the first heat exchanger (6), a first condenser (9), a hydrogen storage unit (21) and a carbon dioxide storage unit (22). The anode outlet (104) is connected to the anode inlet (102) through a second ejector (16); the anode outlet (104) is connected to the exhaust gas processor (17), the second heat exchanger (12), the second condenser (18), and the carbon dioxide storage unit (22) in sequence.

2. A water electrolysis coupled hydrocarbon fuel hydrogen production system according to claim 1, characterized in that: The exhaust gas processor (17) is connected to an oxygen generator (19), and the oxygen generator (19) supplies oxygen to the exhaust gas processor (17) so that the hydrocarbon fuel can be completely oxidized after passing through the electrolysis module. An oxygen sensor (20) is installed in the exhaust gas processor (17) to monitor the oxygen content in the exhaust gas processor (17) and feed back to the oxygen generator (19), so as to control the oxygen content in the exhaust gas processor (17) to be lower than 100 ppm.

3. A water electrolysis coupled hydrocarbon fuel hydrogen production system according to claim 1, characterized in that: The condensed liquid water in the first condenser (9) and the second condenser (18) flows back to the water supply part (2).

4. A water electrolysis coupled hydrocarbon fuel hydrogen production system according to claim 1, characterized in that: The heating temperature of the first heater (7) and the second heater (13) is 400-1000°C.

5. The water electrolysis coupled hydrocarbon fuel hydrogen production system according to claim 1, characterized in that: The temperature of the first steam generator (5) and the second steam generator (15) is set to 120-150°C.

6. A water electrolysis coupled hydrocarbon fuel hydrogen production system according to claim 1, characterized in that: The ejection coefficient of the first ejector (8) is 0.1-0.

2.

7. The water electrolysis coupled hydrocarbon fuel hydrogen production system according to claim 1, characterized in that: The ejection coefficient of the second ejector (16) is 3-4.

8. The water electrolysis coupled hydrocarbon fuel hydrogen production system according to claim 1, characterized in that: The first heat exchanger (6) includes an A port, a B port, a C port, and a D port. The output end of the first mass flow meter (10) and the output end of the first steam generator (5) are connected to the A port. The input end of the first heater (7) is connected to the B port. The cathode outlet (103) is connected to the C port. The input end of the first condenser (9) is connected to the D port.

9. The water electrolysis coupled hydrocarbon fuel hydrogen production system according to claim 1, characterized in that: The second heat exchanger (12) comprises an E port, an F port, a G port, and an H port. The output end of the second steam generator (15) and the output end of the second mass flow meter (11) are both connected to the E port. The input end of the second heater (13) is connected to the F port. The output end of the exhaust gas processor (17) is connected to the G port. The input end of the second condenser (18) is connected to the H port.

10. A hydrogen production method according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1, start-up phase: the water in the water supply part (2) is converted into water vapor, mixed with the hydrogen output from the hydrogen storage part (21) and subjected to heat exchange and temperature rise, and finally heated to a reaction temperature of 400 to 1000° C., and then enters the electrolysis module (1) for cathode electrolysis reaction; the water in the water supply part (2) is evaporated into water vapor, mixed with the hydrocarbon fuel output from the hydrocarbon fuel supply part (3) and subjected to heat exchange and temperature rise, and finally heated to a reaction temperature of 400 to 1000° C., and then enters the electrolysis module (1) for anode electrolysis reaction; Step 2, steady-state operation stage: the tail gas discharged from the electrolysis module (1) is proportionally circulated, and part of the tail gas is circulated to the cathode inlet (101) and the anode inlet (102) according to the corresponding ejection coefficient. At this time, the hydrogen storage unit (21) stops supplying hydrogen to the cathode inlet (101), and the water supply unit (2) stops supplying water vapor to the anode inlet (102).

Images