Solid oxide electrolytic cell hydrogen production system and operation method thereof

Abstract

The invention relates to a SOEC (Solid Oxide Electrolyte Cell) hydrogen production system and an operation method thereof. The SOEC hydrogen production system comprises an SOEC galvanic pile module, a deionized water pump, a deionized water preheater, a heat exchange type steam generator, an ejector, a feed gas preheater, a hydrogen preheater, a fan, an air preheater, a combustor, a stop valve, a heat tracing band, a power supply, a control system, a pipeline, a temperature sensor and the like. The system is provided with the combustor, the heat exchange type steam generator and the heat exchanger, heat generated by combustion of natural gas is used for providing heat for high-temperature raw material gas and high-temperature air required by the SOEC hydrogen production system in a heat exchange mode, meanwhile, heat of high-temperature gas at an outlet of an SOEC galvanic pile module is recycled, and the power consumption of the SOEC hydrogen production system is effectively reduced; in addition, the high-temperature raw material gas containing hydrogen is heated in a heat exchange mode instead of an electric heating mode, so that the safety of the hydrogen production system is effectively improved; the system is low in power consumption, stable, reliable and high in operability.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell systems, and in particular to a solid oxide electrolysis cell hydrogen production system and an operation method thereof. Background Art

[0002] Solid Oxide Electrolysis Cell (SOEC) hydrogen production technology is an efficient green hydrogen production technology. Under external voltage and high temperature, water vapor is electrolyzed to produce high-purity hydrogen and oxygen, realizing the conversion of electrical energy and thermal energy into chemical energy.

[0003] Compared with the more common alkaline water electrolysis hydrogen production technology and proton exchange membrane electrolysis hydrogen production technology, SOEC electrolysis hydrogen production has the highest working efficiency and the largest current density. SOEC is currently the most efficient water electrolysis technology. On the other hand, SOEC electrolysis hydrogen production technology has a wide adaptability to raw materials. The feed of the SOEC electrolyzer is water vapor. If carbon dioxide is added, syngas (Syngas, a mixture of hydrogen and carbon monoxide) can be generated, and then synthetic fuels (e-fuels, such as diesel and aviation fuel) can be further produced. Therefore, SOEC technology is expected to be widely used in carbon dioxide recovery, fuel production and chemical synthesis products, and has the advantages of carbon neutral cycle. In addition, SOEC technology has the characteristic of reversible operation mode. If the solid oxide electrolysis unit (SOEC) for water hydrogen production is combined with the (SOFC) for hydrogen power generation into a system, a set of efficient hydrogen or electricity chemical energy storage devices can be formed. When there is excess electricity, the surplus electricity of renewable energy can be used to produce hydrogen, and the electrical energy can be efficiently converted into chemical energy (hydrogen energy). When electricity is tight, the stored hydrogen can be used to generate electricity and obtain electrical energy through electrochemical reactions. From the perspective of material cost, the core components of SOEC are solid oxide ceramic materials and stainless steel materials, which have strong mechanical stability and environmental adaptability, and do not use precious metal catalysts, so the material cost is low.

[0004] The SOEC hydrogen production system mainly includes a high-temperature air supply system, a raw gas supply system, an exhaust gas treatment system, an electronic control system, etc. Among them, the air supply system usually adopts a combination of a fan and electric heating; the raw gas of SOEC refers to a mixture of high-temperature water vapor and hydrogen, the high-temperature water vapor comes from a steam generator and a high-temperature heat exchanger, and the hydrogen comes from external bottled gas or hydrogen generated by the SOEC hydrogen production system itself; the conventional SOEC hydrogen production system uses electric heating to heat the required air and water vapor, especially after a certain proportion of hydrogen is added to the raw gas, the electric heating of water vapor and hydrogen is more likely to cause safety accidents.

[0005] Therefore, developing a SOEC hydrogen production system with low power consumption, stability, reliability and strong operability plays an important role in the development of SOEC hydrogen production systems. Summary of the invention

[0006] A new type of solid oxide electrolysis cell hydrogen production system and its operation method are proposed. Different from the conventional SOEC hydrogen production system that uses electric heating to heat the hydrogen-containing raw gas and air, the SOEC hydrogen production system proposed in the present invention is equipped with a burner, a heat exchange steam generator, and a heat exchanger. The heat generated by the combustion of natural gas is used to provide heat for the high-temperature raw gas and high-temperature air required by the SOEC hydrogen production system through heat exchange, and the heat of the high-temperature gas at the outlet of the SOEC stack module is recovered, which effectively reduces the power consumption of the SOEC hydrogen production system and improves the system efficiency; in addition, the high-temperature raw gas containing hydrogen is heated by heat exchange instead of electric heating, which effectively improves the safety of the hydrogen production system; the system has low power consumption, is stable and reliable, and has strong operability. The present invention provides the following technical solutions:

[0007] The first object of the present invention is to provide a solid oxide electrolysis cell hydrogen production system, comprising a control system for controlling the entire system and a raw gas preheater, an ejector, a heat exchange steam generator, a deionized water preheater, a deionized water pump, an air heat exchanger, and a fan which are connected in sequence to the SOEC stack module; the SOEC stack module is also connected to a burner, which is respectively connected to the air preheater, the hydrogen preheater, and the raw gas preheater, and the air preheater, the hydrogen preheater, and the raw gas preheater are all connected to the SOEC stack module. A deionized water preheater is connected; a third stop valve and a second stop valve are respectively provided between the hydrogen preheater and the burner and the deionized water preheater; the SOEC stack module is also connected in sequence with the ejector, the hydrogen preheater connected to the bottled hydrogen, the heat exchange steam generator, and the deionized water preheater, the deionized water preheater is provided with a flue gas outlet and a hydrogen outlet, and a fourth stop valve and a fifth stop valve are respectively provided between the ejector and the hydrogen preheater and the SOEC stack module.

[0008] The burner uses pipeline natural gas or bottled compressed natural gas as fuel and high-temperature oxygen-rich air at the air electrode outlet of the SOEC stack module as a combustion aid, and the burner produces high-temperature flue gas; during the temperature rise and fall stage and the hot standby stage of the SOEC hydrogen production system, the high-temperature flue gas enters the air preheater, the hydrogen preheater, and the raw gas preheater respectively, and heats the room temperature air on the cold side of the air preheater, the room temperature bottled hydrogen used for startup, and the raw gas to the target temperature; during the hydrogen production process of the SOEC hydrogen production system, the high-temperature flue gas only enters the air preheater and the raw gas preheater to heat the air and the raw gas.

[0009] The hydrogen preheater is mainly used to provide hydrogen of suitable temperature for the SOEC stack module during the startup and temperature increase and decrease stages of the SOEC hydrogen production system, and to protect the electrode materials of the SOEC stack module; no hydrogen is produced during the startup and temperature increase and decrease stages of the SOEC hydrogen production system, but the SOEC stack module requires a raw gas with suitable temperature and a mixture of hydrogen and water vapor, so the bottled hydrogen and the first stop valve and the fourth stop valve on the pipeline are opened, and the hydrogen reaches a suitable temperature after heat exchange with the high-temperature flue gas at the burner outlet in the hydrogen preheater, enters the ejector and mixes with water vapor to form a raw gas, the volume ratio of water vapor to hydrogen in the raw gas is 20:1, and enters the SOEC stack module after being heated by the raw gas preheater.

[0010] The main function of the ejector is to use the large-flow, high-pressure water vapor generated by the heat exchange steam generator to eject the hydrogen at the outlet of the SOEC stack module under the rated working state, so that a certain amount of hydrogen and water vapor are fully mixed and then heated by the raw gas preheater to enter the SOEC stack module for electrolytic hydrogen production. The volume ratio of water vapor and hydrogen in the raw gas is 20:1. The existence of the ejector enables the SOEC hydrogen production system to use part of the hydrogen produced by the SOEC stack module during the rated hydrogen production process, without the need for external supply of bottled hydrogen, thereby reducing the system operating cost.

[0011] Deionized water is successively heat-exchanged in the deionized water preheater, the heat exchange steam generator, and the raw gas preheater, and is converted from liquid water into high-temperature steam for electrolysis and hydrogen production in the SOEC stack module; wherein, the heat source of the raw gas preheater comes from the high-temperature flue gas generated by the burner, and the heat source of the deionized water preheater comes from the flue gas at the outlet of the air preheater, the hydrogen preheater (only enabled outside the full-load working state of the SOEC hydrogen production system), and the waste heat of the flue gas at the outlet of the raw gas preheater, thereby realizing the cascade utilization of high-temperature flue gas, maximizing the utilization of the system's heat, and reducing the system's energy consumption.

[0012] A small portion of the high-temperature hydrogen-water vapor mixture at the outlet of the SOEC stack module returns to the inlet of the SOEC stack module through the ejector, and the rest passes through the heat exchange steam generator and the deionized water preheater for heat exchange, cooling and condensation, which not only realizes the condensation and purification of hydrogen, but also makes full use of the waste heat of the high-temperature mixture and reduces the energy consumption of the system.

[0013] The temperature sensors are arranged at the inlet and outlet of air and raw gas of the SOEC stack module, the air outlet of the air preheater, the hydrogen outlet of the hydrogen preheater, and the outlet of the raw gas preheater, and are used to monitor important temperature parameters during the operation of the SOEC hydrogen production system. The control system adjusts the natural gas flow rate, the water vapor flow rate, and the switch of the stop valve through the mass flow controller according to the working state of the SOEC stack module and the values ​​of these temperature sensors to effectively control the working state and the heating and cooling rate of the SOEC stack module, so as to maintain the safe, stable and efficient operation of the entire SOEC hydrogen production system.

[0014] The second object of the present invention is to provide an operating method for the above-mentioned solid oxide electrolysis cell hydrogen production system, comprising the following steps: ① In the first heating stage of the SOEC hydrogen production system, the fan and the natural gas shut-off valve are turned on, and the room temperature air passes through the fan, the air preheater, and the SOEC stack module and then merges with the natural gas in the burner for combustion. The high-temperature flue gas generated by the burner enters the air preheater, the deionized water preheater, and the raw gas preheater. The flow rates of natural gas and air are controlled by a mass flow controller to maintain the burner temperature at a suitable temperature. The heating tape from the heat exchange steam generator to the inlet and outlet of the SOEC stack module is turned on, and the SOEC stack module is heated at a certain temperature rise rate; ② In the second heating stage of the SOEC hydrogen production system, When the temperature of the pipeline between the heat exchange steam generator and the SOEC stack module reaches above 120°C, and the temperature of the SOEC stack module reaches above 120°C, open the deionized water pump, the bottled hydrogen, the first stop valve and the fourth stop valve of the bottled hydrogen to the ejector pipeline, the second stop valve and the third stop valve on the burner-hydrogen preheater-deionized water preheater pipeline, and close the fifth stop valve between the SOEC stack module and the ejector; after the deionized water passes through the deionized water pump, the deionized water preheater, and the heat exchange steam generator, it is mixed with the bottled hydrogen at the outlet of the hydrogen preheater in the ejector to form raw gas, and the raw gas passes through the raw material preheater, the SOEC stack module, the heat exchange steam generator, and the deionized water preheater. The remaining heat is recovered to the deionized water and water vapor at the inlet of the system; in this process, the control system adjusts the flow rate of natural gas and air according to the temperature sensors at the outlet of each heat exchanger, so that the SOEC stack module gradually heats up to the operating temperature at a certain temperature rise rate; in the feed gas, the volume ratio of water vapor and hydrogen is 20:1; ③ The SOEC hydrogen production system gradually increases the electrolysis current in the hydrogen production stage. When the temperature of the SOEC stack module reaches the target value, the electrolysis power supply is started and the electrolysis current is gradually increased to produce hydrogen. The control system adjusts the natural gas flow, bottled hydrogen flow, and deionized water flow according to the temperature of the inlet and outlet of the SOEC stack module, the rate of change of the electrolysis current and other parameters until the electrolysis current reaches the rated value; ④ In the stage of hydrogen production at rated load of SOEC hydrogen production system, the fifth stop valve between the ejector and the SOEC stack module is opened, and the flow rate of bottled hydrogen is gradually reduced. When the flow rate of bottled hydrogen is reduced to 0, the first stop valve and the fourth stop valve of the pipeline between the ejector and the bottled hydrogen are closed, and the second stop valve and the third stop valve of the pipeline between the burner and the deionized water preheater are closed; ⑤ In the stage of gradually reducing the electrolysis current of SOEC hydrogen production system, the control strategy of the system is opposite to that of hydrogen production stage of increasing the electrolysis current. The second stop valve and the third stop valve of the pipeline between the burner and the deionized water preheater are opened, and the bottled hydrogen pipeline is opened, and then the fifth stop valve between the ejector and the SOEC stack module is closed, and then the electrolysis current is gradually reduced;⑥ During the cooling stage of the SOEC stack module, the control strategy of the system is similar to that of the heating stage. When the temperature of the SOEC stack module and the temperature of the pipeline through which the raw gas passes are reduced to 120°C, or when the SOEC stack module no longer needs the raw gas, the deionized water pump and the bottled hydrogen pipeline are turned off. ;

[0015] Compared with the prior art, the advantages of the present invention are: the system is provided with a burner, a heat exchange steam generator, and a heat exchanger, and utilizes the heat generated by the combustion of natural gas to provide heat for the high-temperature raw gas and high-temperature air required by the SOEC hydrogen production system through heat exchange, and at the same time recovers the heat of the high-temperature gas at the outlet of the SOEC stack module, effectively reducing the power consumption of the SOEC hydrogen production system; in addition, the high-temperature raw gas containing hydrogen is heated by heat exchange rather than electric heating, which effectively improves the safety of the hydrogen production system; the system has low power consumption, is stable and reliable, and has strong operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a schematic diagram of the overall structure of a solid oxide electrolysis cell hydrogen production system;

[0018] Among them: 1. SOEC stack module; 2. Deionized water pump; 3. Deionized water preheater; 4. Heat exchange steam generator; 5. Ejector; 6. Raw gas preheater; 7. Hydrogen preheater; 8. Fan; 9. Air preheater; 10. Burner; 11. First stop valve; 12. Second stop valve; 13. Third stop valve; 14. Fourth stop valve; 15. Fifth stop valve; 16. Natural gas stop valve. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0020] The specific implementation of the present invention will be described below in conjunction with the accompanying drawings:

[0021] like Figure 1As shown, the first object of the present invention is to provide a solid oxide electrolysis cell hydrogen production system, including a control system for controlling the entire system and a raw gas preheater, an ejector 5, a heat exchange steam generator 4, a deionized water preheater 3, a deionized water pump 2, an air heat exchanger 9, and a fan 8, which are respectively connected to the SOEC stack module 1 in sequence; the SOEC stack module 1 is also connected to a burner 10, and the burner 10 is respectively connected to the air preheater 9, the hydrogen preheater 7, and the raw gas preheater 6, and the air preheater 9, the hydrogen preheater 7, and the raw gas preheater 6 are all connected to the SOEC stack module 1. The deionized water preheater 3 is connected; a third stop valve 13 and a second stop valve 12 are respectively provided between the hydrogen preheater 7 and the burner 10 and the deionized water preheater 3; the SOEC stack module 1 is also connected in sequence with the ejector 5, the hydrogen preheater 7 connected to the bottled hydrogen, the heat exchange steam generator 4, and the deionized water preheater 3, the deionized water preheater 3 is provided with a flue gas outlet and a hydrogen outlet, and a fourth stop valve 14 and a fifth stop valve 15 are respectively provided between the ejector 5 and the hydrogen preheater 7 and the SOEC stack module 1.

[0022] The burner 10 uses pipeline natural gas or bottled compressed natural gas as fuel and the high-temperature oxygen-rich air at the air electrode outlet of the SOEC stack module 1 as a combustion aid, and the burner 10 produces high-temperature flue gas; during the temperature rise and fall stage and the hot standby stage of the SOEC hydrogen production system, the high-temperature flue gas enters the air preheater 9, the hydrogen preheater 7, and the raw gas preheater 6 respectively, and the room temperature air on the cold side of the air preheater 9, the room temperature bottled hydrogen used for startup, and the raw gas are heated to the target temperature; during the hydrogen production process of the SOEC hydrogen production system, the high-temperature flue gas only enters the air preheater 9 and the raw gas preheater 6 to heat the air and the raw gas.

[0023] The hydrogen preheater 7 is mainly used to provide hydrogen of suitable temperature for the SOEC stack module 1 during the startup and temperature increase and decrease stages of the SOEC hydrogen production system, and to protect the electrode materials of the SOEC stack module 1. No hydrogen is produced during the startup and temperature increase and decrease stages of the SOEC hydrogen production system, but the SOEC stack module requires a raw gas with suitable temperature and a mixture of hydrogen and water vapor. Therefore, the bottled hydrogen and the first stop valve 11 and the fourth stop valve 14 on the pipeline are opened, and the hydrogen reaches a suitable temperature after heat exchange with the high-temperature flue gas at the outlet of the burner 10 in the hydrogen preheater 7, and enters the ejector 5 to mix with water vapor to form a raw gas. The volume ratio of water vapor to hydrogen in the raw gas is 20:1, and the raw gas enters the SOEC stack module 1 after being heated by the raw gas preheater 6.

[0024] The main function of the ejector 5 is to use the large-flow, high-pressure water vapor generated by the heat exchange steam generator 4 to eject the hydrogen at the outlet of the SOEC stack module 1 under the rated working state, so that a certain amount of hydrogen and water vapor are fully mixed and then heated by the raw gas preheater 6 to enter the SOEC stack module 1 for electrolytic hydrogen production. The volume ratio of water vapor and hydrogen in the raw gas is 20:1. The existence of the ejector 5 enables the SOEC hydrogen production system to utilize a part of the hydrogen produced by the SOEC stack module 1 during the rated hydrogen production process, without the need to supply bottled hydrogen from the outside, thereby reducing the system operating cost.

[0025] Deionized water is successively heat-exchanged in the deionized water preheater 3, the heat exchange steam generator 4, and the raw gas preheater 6, and is converted from liquid water into high-temperature steam for electrolysis and hydrogen production in the SOEC stack module 1; wherein, the heat source of the raw gas preheater 6 comes from the high-temperature flue gas generated by the burner 10, and the heat source of the deionized water preheater 3 comes from the flue gas at the outlet of the air preheater 9, the hydrogen preheater 7 (only enabled outside the full-load working state of the SOEC hydrogen production system), and the waste heat of the flue gas at the outlet of the raw gas preheater 6, thereby realizing the cascade utilization of high-temperature flue gas, maximizing the utilization of the system's heat, and reducing the system's energy consumption.

[0026] A small portion of the high-temperature hydrogen-water vapor mixture at the outlet of the SOEC stack module 1 returns to the inlet of the SOEC stack module 1 through the ejector 5, and the remaining portion passes through the heat exchange steam generator 4 and the deionized water preheater 3 for heat exchange, cooling, and condensation, thereby achieving condensation and purification of hydrogen, making full use of the waste heat of the high-temperature mixture, and reducing system energy consumption.

[0027] The temperature sensors are arranged at the inlet and outlet of air and raw gas of the SOEC stack module 1, the air outlet of the air preheater 9, the hydrogen outlet of the hydrogen preheater 7, and the outlet of the raw gas preheater 6, and are used to monitor important temperature parameters during the operation of the SOEC hydrogen production system. The control system adjusts the natural gas flow rate, the water vapor flow rate, the switching of the corresponding shut-off valves, etc. through the mass flow controller according to the working state of the SOEC stack module 1 and the values ​​of these temperature sensors to effectively control the working state and the heating and cooling rates of the SOEC stack module 1, so as to maintain the safe, stable and efficient operation of the entire SOEC hydrogen production system.

[0028] The second object of the present invention is to provide an operating method for the above-mentioned solid oxide electrolytic cell hydrogen production system, comprising the following steps: ① In the first heating stage of the SOEC hydrogen production system, the fan 8 and the natural gas shut-off valve 16 are turned on, and the room temperature air passes through the fan 8, the air preheater 9, and the SOEC stack module 1 and then merges with the natural gas in the burner 10 for combustion. The high-temperature flue gas generated by the burner enters the air preheater 9, the deionized water preheater 3, and the raw gas preheater 6. The flow rates of natural gas and air are controlled by a mass flow controller to maintain the temperature of the burner 10 at a suitable temperature. The heating tape from the heat exchange steam generator 4 to the inlet and outlet of the SOEC stack module 1 is turned on, and the SOEC stack module 1 is pressed. The temperature is raised at a certain temperature rise rate; ② In the second stage of heating of the SOEC hydrogen production system, when the temperature of the pipeline between the heat exchange steam generator 4 and the SOEC stack module 1 reaches above 120°C and the SOEC stack module 1 reaches above 120°C, the deionized water pump 2 is turned on, the bottled hydrogen, the first stop valve 11 and the fourth stop valve 14 of the bottled hydrogen to the ejector 5 pipeline, the second stop valve 12 and the third stop valve 13 on the burner 10-hydrogen preheater 7-deionized water preheater 3 pipeline, and the fifth stop valve 15 between the SOEC stack module 1 and the ejector 5 is closed; the deionized water is discharged through the deionized water pump 2, the deionized water preheater 3, the heat exchange steam generator 4, and ... After that, it is mixed with the bottled hydrogen at the outlet of the hydrogen preheater 7 in the ejector 5 to form the raw gas. The raw gas passes through the raw material preheater 6, the SOEC stack module 1, the heat exchange steam generator 4, and the deionized water preheater 3, and the excess heat is recovered to the deionized water and water vapor at the system inlet; in this process, the control system adjusts the flow rate of natural gas and air flow according to the temperature sensors at the outlet of each heat exchanger, so that the SOEC stack module 1 gradually heats up to the operating temperature at a certain temperature rise rate; in the raw gas, the volume ratio of water vapor to hydrogen is 20:1; ③ The SOEC hydrogen production system gradually increases the electrolysis current hydrogen production stage. When the temperature of the SOEC stack module 1 reaches the target value, the electric current is started. The power supply is unlocked, and the electrolysis current is gradually increased to produce hydrogen. The control system adjusts the natural gas flow, the bottled hydrogen flow, and the deionized water flow according to the temperature of the inlet and outlet of the SOEC stack module 1, the electrolysis current change rate and other parameters until the electrolysis current reaches the rated value; ④ When the SOEC hydrogen production system produces hydrogen at rated load, the fifth stop valve 15 between the ejector 5 and the SOEC stack module 1 is opened, and the flow of the bottled hydrogen is gradually reduced. When the flow of the bottled hydrogen is reduced to 0, the first stop valve 11 and the fourth stop valve 14 of the pipeline between the ejector 5 and the bottled hydrogen are closed, and the second stop valve 12 and the third stop valve 13 of the pipeline between the burner 10 and the deionized water preheater 3 are closed;⑤ In the stage where the SOEC hydrogen production system gradually reduces the electrolysis current, the control strategy of the system is opposite to that of the stage where the electrolysis current is increased. The second stop valve 12 and the third stop valve 13 of the pipeline between the burner 10 and the deionized water preheater 3 are opened, and the bottled hydrogen pipeline is opened, and then the fifth stop valve 15 between the ejector 5 and the SOEC stack module 1 is closed, and then the electrolysis current is gradually reduced; ⑥ In the stage where the SOEC stack module 1 is cooled down, the control strategy of the system is similar to that of the heating stage. When the temperature of the SOEC stack module 1 and the temperature of the pipeline through which the raw gas passes are reduced to 120°C, or when the SOEC stack module 1 no longer needs the raw gas, the deionized water pump 2 is closed and the bottled hydrogen pipeline is closed. ;

[0029] Compared with the prior art, the advantages of the present invention are: the SOEC hydrogen production system does not adopt a conventional electric heating device. The system is provided with a burner 10, a heat exchange steam generator 4, and heat exchangers 3, 6, 7, and 9. The heat generated by the combustion of natural gas is used to provide heat for the high-temperature raw gas and high-temperature air required by the SOEC hydrogen production system through heat exchange, and the heat of the high-temperature gas at the outlet of the SOEC stack module 1 is recovered, thereby effectively reducing the power consumption of the SOEC hydrogen production system; in addition, the high-temperature raw gas containing hydrogen is heated by heat exchange rather than electric heating, thereby effectively improving the safety of the hydrogen production system; the system has low power consumption, is stable and reliable, and has strong operability.

[0030] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A solid oxide electrolysis cell hydrogen production system, characterized in that: The invention comprises a control system for controlling the whole system and a raw gas preheater, an ejector, a heat exchange steam generator, a deionized water preheater, a deionized water pump, an air heat exchanger and a fan which are respectively connected with the SOEC stack module in sequence; the SOEC stack module is also connected with a burner, which is respectively connected with the air preheater, the hydrogen preheater and the raw gas preheater, and the air preheater, the hydrogen preheater and the raw gas preheater are all connected with the deionized water preheater; a third stop valve and a second stop valve are respectively arranged between the hydrogen preheater and the burner and the deionized water preheater; the SOEC stack module is also respectively connected with the ejector, the hydrogen preheater connected with bottled hydrogen, the heat exchange steam generator and the deionized water preheater in sequence, the deionized water preheater is provided with a flue gas outlet and a hydrogen outlet, and a fourth stop valve and a fifth stop valve are respectively arranged between the ejector and the hydrogen preheater and the SOEC stack module.

2. The solid oxide electrolysis cell hydrogen production system according to claim 1, characterized in that: The burner uses pipeline natural gas or bottled compressed natural gas as fuel and high-temperature oxygen-rich air at the air electrode outlet of the SOEC stack module as a combustion aid, and the burner produces high-temperature flue gas; during the temperature rise and fall stage and the hot standby stage of the SOEC hydrogen production system, the high-temperature flue gas enters the air preheater, the hydrogen preheater, and the raw gas preheater respectively, and heats the room temperature air on the cold side of the air preheater, the room temperature bottled hydrogen used for startup, and the raw gas to the target temperature; during the hydrogen production process of the SOEC hydrogen production system, the high-temperature flue gas only enters the air preheater and the raw gas preheater to heat the air and the raw gas.

3. The solid oxide electrolysis cell hydrogen production system according to claim 1, characterized in that: The hydrogen preheater is mainly used to provide hydrogen of suitable temperature for the SOEC stack module during the startup and temperature increase and decrease stages of the SOEC hydrogen production system, and to protect the electrode materials of the SOEC stack module; during the startup and temperature increase and decrease stages of the SOEC hydrogen production system, the bottled hydrogen and the first stop valve on its pipeline are opened, and the hydrogen reaches a suitable temperature after heat exchange with the high-temperature flue gas at the burner outlet in the hydrogen preheater, enters the ejector and mixes with water vapor to form a raw gas, the volume ratio of water vapor to hydrogen in the raw gas is 20:1, and enters the SOEC stack module after being heated by the raw gas preheater.

4. The solid oxide electrolysis cell hydrogen production system according to claim 1, characterized in that: The main function of the ejector is to use the large-flow, high-pressure water vapor generated by the heat exchange steam generator to eject the hydrogen at the outlet of the SOEC stack module under the rated working state, so that a certain amount of hydrogen and water vapor are fully mixed and then heated by the raw gas preheater to enter the SOEC stack module for electrolytic hydrogen production. The volume ratio of water vapor and hydrogen in the raw gas is 20:

1. The existence of the ejector enables the SOEC hydrogen production system to use part of the hydrogen produced by the SOEC stack module during the rated hydrogen production process, without the need for external supply of bottled hydrogen, thereby reducing the system operating cost.

5. The solid oxide electrolysis cell hydrogen production system according to claim 1, characterized in that: Deionized water is successively heat-exchanged in the deionized water preheater, the heat exchange steam generator, and the raw gas preheater, and is converted from liquid water into high-temperature steam for electrolysis and hydrogen production in the SOEC stack module; wherein, the heat source of the raw gas preheater comes from the high-temperature flue gas generated by the burner, and the heat source of the deionized water preheater comes from the flue gas at the outlet of the air preheater, the hydrogen preheater, and the waste heat of the flue gas at the outlet of the raw gas preheater, thereby realizing the cascade utilization of high-temperature flue gas, maximizing the utilization of the system's heat, and reducing the system's energy consumption.

6. The solid oxide electrolysis cell hydrogen production system according to claim 1, characterized in that: Under the rated operating conditions of the system, a small portion of the high-temperature hydrogen-water vapor mixture at the outlet of the SOEC stack module returns to the inlet of the SOEC stack module through the ejector, and the rest passes through the heat exchange steam generator and the deionized water preheater for heat exchange, cooling and condensation, which not only realizes the condensation and purification of hydrogen, but also makes full use of the waste heat of the high-temperature mixture and reduces the energy consumption of the system.

7. The solid oxide electrolysis cell hydrogen production system according to claim 1, characterized in that: Temperature sensors are arranged at the inlet and outlet of air and raw gas of the SOEC stack module, the air outlet of the air preheater, the hydrogen outlet of the hydrogen preheater, and the outlet of the raw gas preheater, and are used to monitor important temperature parameters during the operation of the SOEC hydrogen production system. The control system adjusts the natural gas flow rate, the water vapor flow rate, and the switch of the shut-off valve according to the working state of the SOEC stack module and the values ​​of these temperature sensors to effectively control the working state and the heating and cooling rates of the SOEC stack module, so as to maintain the safe, stable and efficient operation of the entire SOEC hydrogen production system.

8. The method for operating a solid oxide electrolytic cell hydrogen production system according to any one of claims 1 to 7, comprising the following steps: ① In the first heating stage of the SOEC hydrogen production system, the fan and the natural gas shut-off valve are turned on, and the room temperature air passes through the fan, the air preheater, and the SOEC stack module and then merges with the natural gas in the burner for combustion. The high-temperature flue gas generated by the burner enters the air preheater, the deionized water preheater, and the raw gas preheater. The flow rates of the natural gas and the air are controlled by a mass flow controller to maintain the burner temperature at a suitable temperature. The heating tape from the heat exchange steam generator to the inlet and outlet of the SOEC stack module is turned on, and the SOEC stack module is heated at a certain temperature rise rate; ② In the heating stage of the SOEC hydrogen production system 2. When the temperature of the pipeline between the heat exchange steam generator and the SOEC stack module reaches above 120°C and the temperature of the SOEC stack module reaches above 120°C, open the deionized water pump, the bottled hydrogen, the first stop valve and the fourth stop valve of the pipeline from the bottled hydrogen to the ejector, the second stop valve and the third stop valve on the burner-hydrogen preheater-deionized water preheater pipeline, and close the fifth stop valve between the SOEC stack module and the ejector; after the deionized water passes through the deionized water pump, the deionized water preheater, and the heat exchange steam generator, it is mixed with the bottled hydrogen at the outlet of the hydrogen preheater in the ejector to form the raw gas. After the raw gas passes through the raw material preheater, the SOEC stack module, the heat exchange steam generator, and the deionized water preheater, The excess heat is recovered to the deionized water and water vapor at the inlet of the system; in this process, the control system adjusts the flow rate of natural gas and air according to the temperature sensors at the outlet of each heat exchanger, so that the SOEC stack module gradually heats up to the operating temperature at a certain temperature rise rate; in the feed gas, the volume ratio of water vapor and hydrogen is 20:1; ③ The SOEC hydrogen production system gradually increases the electrolysis current in the hydrogen production stage. When the temperature of the SOEC stack module reaches the target value, the electrolysis power supply is started and the electrolysis current is gradually increased to produce hydrogen. The control system adjusts the natural gas flow rate, bottled hydrogen flow rate, and deionized water flow rate according to the temperature of the inlet and outlet of the SOEC stack module, the electrolysis current change rate and other parameters until the electrolysis current reaches the rated value; ④When the SOEC hydrogen production system produces hydrogen at rated load, the fifth stop valve between the ejector and the SOEC stack module is opened, and the flow rate of bottled hydrogen is gradually reduced. When the flow rate of bottled hydrogen is reduced to 0, the first stop valve and the fourth stop valve of the pipeline between the ejector and the bottled hydrogen are closed, and the second stop valve and the third stop valve of the pipeline between the burner and the deionized water preheater are closed; ⑤When the SOEC hydrogen production system gradually reduces the electrolysis current, the control strategy of the system is opposite to that of the hydrogen production stage of increasing the electrolysis current. The second stop valve and the third stop valve of the pipeline between the burner and the deionized water preheater are opened, and the bottled hydrogen pipeline is opened, and then the fifth stop valve between the ejector and the SOEC stack module is closed, and then the electrolysis current is gradually reduced;⑥ During the cooling stage of the SOEC stack module, the control strategy of the system is similar to that of the heating stage. When the temperature of the SOEC stack module and the temperature of the pipeline through which the raw gas passes are reduced to 120°C, or when the SOEC stack module no longer needs the raw gas, the deionized water pump and the bottled hydrogen pipeline are turned off. ;

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