SOEC water electrolysis system and control method

Abstract

The invention relates to the technical field of hydrogen production through water electrolysis, in particular to an SOEC water electrolysis system and a control method, and the SOEC water electrolysis system comprises an SOEC electric pile, a water vapor input assembly, an air input assembly, a hydrogen input assembly, a protective gas input assembly and a hydrogen output assembly; wherein the water vapor input assembly comprises a water tank, a water pump, a water preheater, a water evaporator, a water vapor flowmeter and a residual water backflow branch; water introduced into the system serves as cooling water for cooling cathode tail gas in the water preheater and also serves as a water vapor source to be supplied to the SOEC galvanic pile for an electrolytic reaction, an independent condenser does not need to be additionally arranged, and the equipment cost is reduced. The residual water backflow branch is connected between the water preheater and the water evaporator, and excessive cooling water flows back to the water tank again before water is evaporated by the water evaporator and enters the water vapor flowmeter, so that the water is recycled, and the water utilization rate is improved. And moreover, the cooling water flow required by cathode tail gas cooling and the water vapor flow required by electrolysis are decoupled, so that the cooling water flow and the water vapor flow are conveniently and accurately regulated and controlled.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis for hydrogen production, specifically to an SOEC water electrolysis system and control method. Background Technology

[0002] Solid oxide electrolysis cells (SOECs) are a high-temperature (600–900°C) water electrolysis technology for hydrogen production. The basic principle is to use solid oxide electrolytes to decompose water into hydrogen and oxygen at high temperatures. This technology has significant advantages such as high energy conversion efficiency, the ability to couple with high-temperature industrial waste heat, and the direct electrolysis of water vapor, and is considered one of the important technological pathways for achieving large-scale green hydrogen production.

[0003] Because SOEC operates at high temperatures, the feed gas introduced into the SOEC stack needs to be preheated, while the product gas produced by electrolysis needs to be cooled. Therefore, thermal management and control of the SOEC water electrolysis system are crucial. It is necessary not only to ensure that the temperature and flow rate of the feed gas introduced into the SOEC stack meet the requirements, but also to ensure that the water vapor in the product gas can be fully condensed.

[0004] In existing technologies, external refrigeration equipment is usually used to cool the product gas. For example, CN120453411A and CN120443202A both use independent condensers to condense the water vapor in the product gas. Although this method can ensure that the water vapor in the product gas can be fully condensed, it greatly increases the equipment cost. Summary of the Invention

[0005] 1. The problem to be solved To address the problem that existing technologies involve condensing water vapor in product gas using a separate condenser, which significantly increases equipment costs, this invention provides a SOEC electrolysis water system and control method with lower equipment costs.

[0006] 2. Technical Solution To solve the above problems, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides an SOEC electrolysis water system, comprising: an SOEC stack, a water vapor input component for inputting water vapor into the SOEC stack cathode, an air input component for inputting air into the SOEC stack anode, a hydrogen input component for inputting hydrogen into the SOEC stack cathode, a protective gas input component for inputting protective gas into the SOEC stack cathode, and a hydrogen output component for collecting product hydrogen. The steam input assembly includes: A water tank, connected to an external water source, is used to store water; The water pump, with its inlet connected to the water tank, is used to deliver water to the SOEC stack cathode. The water preheater includes a hot side and a cold side. The cold side inlet is connected to the outlet of the water pump, and the hot side inlet is connected to the cathode outlet of the SOEC stack. The cathode exhaust gas flowing through the hot side exchanges heat with the water flowing through the cold side to preheat the water and condense the water vapor in the cathode exhaust gas. The hot side outlet is connected to the hydrogen output assembly, allowing hydrogen to flow to the hydrogen output assembly. The hot side outlet is also connected to the water tank through a condensate branch, allowing the condensate to flow back to the water tank. A fourth temperature sensor is installed at the hot side outlet. The water evaporator, with its inlet connected to the cold-side outlet of the water preheater, is used to completely evaporate water into water vapor. The water vapor flow meter, with its inlet connected to the outlet of the water evaporator, is used to measure the actual flow rate of water vapor delivered to the SOEC stack cathode. The steam check valve has its inlet connected to the outlet of the steam flow meter and its outlet connected to the cathode of the SOEC fuel cell stack. The mixing point of the input hydrogen and the input steam is located downstream of the check valve. The waste water return branch is used to return excess cooling water in the water preheater to the water tank. Its inlet is connected between the water preheater and the water evaporator, and its outlet is connected to the water tank. It is also equipped with a return water regulating valve for controlling the opening and closing of the waste water return branch. The return water regulating valve is communicatively connected to the steam flow meter.

[0007] As a preferred embodiment of the present invention, the steam input assembly further includes a steam heat exchanger disposed downstream of the steam check valve. The steam heat exchanger includes a hot side and a cold side. Its hot side inlet is connected to the cathode outlet of the SOEC stack, its hot side outlet is connected to the hot side inlet of the water preheater, its cold side inlet is connected to the outlet of the steam check valve, and its cold side outlet is connected to the cathode inlet of the SOEC stack, so as to reduce the cathode exhaust gas temperature and increase the steam temperature.

[0008] As a preferred embodiment of the present invention, a first heat tracing tape is wrapped around the steam pipe between the water evaporator and the water vapor heat exchanger to prevent water vapor condensation.

[0009] As a preferred embodiment of the present invention, the steam input assembly further includes a steam electric heater disposed downstream of the steam heat exchanger, and the outlet of the steam electric heater is connected to the cathode inlet of the SOEC stack. The SOEC stack is equipped with a second temperature sensor at both the cathode inlet and cathode outlet, and the second temperature sensor is communicatively connected to the steam electric heater.

[0010] As a preferred embodiment of the present invention, the air input assembly includes at least an air primary heat exchanger, which includes a cold side and a hot side. The hot side is connected to the waste water return branch, and the cold side is used to supply air to reduce the temperature of the cooling water and increase the temperature of the air.

[0011] As a preferred embodiment of the present invention, the air input assembly further includes an air filter, a blower, an air flow meter and a secondary air heat exchanger arranged sequentially along the air flow direction, the outlet of the secondary air heat exchanger is connected to the anode inlet of the SOEC stack, and the primary air heat exchanger is disposed between the air flow meter and the secondary air heat exchanger. The air secondary heat exchanger includes a cold side and a hot side. The cold side inlet is connected to the outlet of the air primary heat exchanger, the cold side outlet is connected to the anode inlet of the SOEC stack, and the hot side inlet is connected to the anode outlet of the SOEC stack, so that the anode exhaust gas can exchange heat with the air. An oxygen sensor is also installed at the anode outlet of the SOEC fuel cell stack, and the oxygen sensor is connected in communication with the blower.

[0012] As a preferred embodiment of the present invention, the air input assembly further includes an air electric heater disposed between the secondary air heat exchanger and the anode inlet. The anode inlet and anode outlet of the SOEC stack are both provided with a first temperature sensor, which is communicatively connected to the air electric heater.

[0013] As a preferred embodiment of the present invention, it further includes a gas flow controller, a gas check valve and a burner arranged sequentially along the gas delivery direction, wherein one port of the burner is connected to the anode outlet of the SOEC stack for providing oxygen for gas combustion; It also includes a multi-flow heat exchanger, which is provided with a first heat exchange chamber, a second heat exchange chamber and a third heat exchange chamber; the inlet of the first heat exchange chamber is connected to the exhaust gas outlet of the burner, and the outlet is connected to the hot side inlet of the air secondary heat exchanger; the inlet of the second heat exchange chamber is connected to the cold side outlet of the steam heat exchanger, and the outlet is connected to the cathode inlet of the SOEC stack; the inlet of the third heat exchange chamber is connected to the cold side outlet of the air secondary heat exchanger, and the outlet is connected to the anode inlet of the SOEC stack. The SOEC fuel cell stack is equipped with a first temperature sensor at both the anode inlet and anode outlet, a second temperature sensor at both the cathode inlet and cathode outlet, and a third temperature sensor at the exhaust outlet of the burner. The first, second, and third temperature sensors are interconnected.

[0014] As a preferred embodiment of the present invention, the hydrogen output assembly includes an output branch and a return branch connected to the hot side outlet of the water preheater. A first hydrogen check valve and a first hydrogen flow meter are sequentially installed along the hydrogen flow direction on the output branch. Along the hydrogen flow direction, a hydrogen circulation pump, a second hydrogen flow meter, and a second hydrogen check valve are sequentially installed on the return branch. The outlet of the second hydrogen check valve is connected to the outlet of the water vapor check valve. A second heat tracing cable is installed on the return branch to prevent residual water vapor in the return gas from condensing.

[0015] As a preferred embodiment of the present invention, the inlet of the hydrogen input component is connected to a hydrogen source, and the hydrogen input component includes a hydrogen control valve, a hydrogen flow controller and a third hydrogen check valve arranged sequentially along the hydrogen input direction, and the outlet of the third hydrogen check valve is connected to the outlet of the water vapor check valve.

[0016] As a preferred embodiment of the present invention, it further includes a protective gas input component, the inlet of which is connected to a protective gas source for inputting protective gas into the SOEC stack cathode. The protective gas input assembly includes a protective gas control valve, a protective gas flow controller, and a protective gas check valve arranged sequentially along the protective gas input direction. The outlet of the protective gas check valve is connected to the outlet of the steam check valve.

[0017] A second aspect of this invention provides a control method for an SOEC water electrolysis system; The water pump control method is as follows: The temperature of the hot side of the water preheater is measured and compared with the required temperature for water vapor condensation. This temperature difference is input into the PI controller to calculate the cooling water flow rate required for water vapor condensation in the cathode tail gas. Obtain the steam flow rate required for the electrolysis reaction, compare this flow rate with the cooling water flow rate, and take the larger of the two values ​​as the system's required water flow rate; The actual water flow rate input to the water pump is measured, and the water pump is adjusted through a PI controller to ensure that the water flow rate meets the system requirements. The adjustment method for the return water regulating valve is as follows: The required opening degree of the return water regulating valve is calculated based on the difference between the required cooling water flow rate and the required steam flow rate, and is used as feedforward for the PI controller. The actual flow rate of steam delivered to the SOEC stack cathode is measured and compared with the steam flow rate required for the electrolysis reaction. This deviation is input into the PI controller to calculate the opening control value of the return water regulating valve. When the actual steam flow rate is greater than the required steam flow rate, the opening of the return water regulating valve is increased, and vice versa.

[0018] The blower control method is as follows: The required air flow rate to be introduced into the SOEC fuel cell is calculated based on the product gas demand flow rate and the oxygen demand concentration at the anode outlet of the SOEC fuel cell, and this is used as feedforward for the PI controller. The oxygen concentration at the anode outlet of the SOEC fuel cell is measured and compared with the oxygen demand concentration. This deviation is input into the PI controller to calculate the required air flow rate of the SOEC fuel cell. During operation, to ensure that the air heater does not overheat, a minimum air flow rate needs to be set. The minimum air flow rate is compared with the air flow rate required by the SOEC stack, and the larger value is taken as the system's required air flow rate. The actual air flow rate of the system is measured, and the blower is adjusted through a PI controller to ensure that the air flow rate meets the system requirements.

[0019] The formula for calculating the feedforward of the PI controller is:

[0020] In the formula: B is the air flow rate required to enter the SOEC stack, in NL / min; A is the product gas flow rate, in NL / min; X is the oxygen concentration required, 25% to 35%.

[0021] The control method for the hydrogen circulation pump is as follows: The required flow rate of mixed hydrogen is calculated by the flow rate of water vapor required for the electrolysis reaction, and the flow rate of hydrogen produced by the electrolysis reaction is calculated by the current value. The smaller value of the two is taken as the required flow rate of circulating hydrogen. The actual flow rate of circulating hydrogen is measured, and the hydrogen circulation pump is adjusted by the PI controller. The hydrogen replenishment control method is as follows: The required flow rate of blended hydrogen is calculated by the required flow rate of water vapor, and the actual flow rate of circulating hydrogen is measured. The difference between the two is used as the required flow rate of supplementary hydrogen, and the hydrogen flow rate is adjusted by a hydrogen flow controller. The method for calculating the required flow rate of blended hydrogen is as follows:

[0022] Where: V1, required flow rate of blended hydrogen, in NL / min; Q, required flow rate of water vapor, in kg / h; K1, coefficient, 1.1; The method for calculating the flow rate of hydrogen produced by electrolysis is as follows:

[0023] Where: V2, hydrogen flow rate generated by electrolysis, in NL / min; I, single cell current; n, number of cells in the SOEC stack; Faraday efficiency, 95%–99%; K2 coefficient, 0.007.

[0024] The control method for the steam electric heater is as follows: The actual temperature of the SOEC stack cathode is measured and compared with the required temperature of the SOEC stack cathode. This deviation is input into the PI controller to calculate the required temperature of the steam electric heater outlet. This temperature is compared with the maximum set temperature of the steam electric heater, and the smaller value is taken as the input of the steam electric heater. The PI controller is used to adjust the steam electric heater to ensure that the temperature of the SOEC stack cathode meets the requirements. The control method for the air electric heater is as follows: The actual temperature of the SOEC fuel cell anode is measured and compared with the required temperature of the SOEC fuel cell anode. This deviation is input into the PI controller to calculate the required temperature of the air heater outlet. This temperature is then compared with the maximum set temperature of the air heater, and the smaller of the two values ​​is taken as the input of the air heater. The air heater is adjusted by the PI controller to ensure that the temperature of the SOEC fuel cell anode meets the requirements.

[0025] The gas flow control method is as follows: The actual temperature of the SOEC fuel cell stack is measured and compared with the required temperature of the SOEC fuel cell stack. This deviation is input into the PI controller to calculate the required temperature of the burner outlet. This temperature is then compared with the highest set temperature of the burner outlet, and the smaller of the two is taken as the required temperature of the burner outlet. The actual temperature of the burner outlet is measured, and the gas flow rate is calculated by the PI controller. The gas flow controller is then adjusted to ensure that the temperature of the SOEC fuel cell stack meets the requirements.

[0026] 3. Beneficial effects Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The water introduced into the system in this invention plays a dual role: it serves as cooling water in the water preheater to cool the cathode tail gas, and as a source of steam to supply the SOEC stack for electrolysis reaction. There is no need to set up a separate condenser, which reduces equipment costs.

[0027] (2) By connecting the excess water return branch between the water preheater and the water evaporator, the excess cooling water is returned to the water tank before the water is evaporated by the water evaporator and before it enters the water vapor flow meter. This not only allows the water to be reused, but also decouples the cooling water flow required for cathode tail gas cooling and the water vapor flow required for electrolysis, making it easier to accurately control the cooling water flow and water vapor flow. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of one embodiment of the SOEC water electrolysis system of the present invention; Figure 2 This is a schematic diagram of another embodiment of the SOEC water electrolysis system in this invention; Figure 3 This is a schematic diagram of the water pump control method in this invention; Figure 4 This is a schematic diagram of the backflow regulating valve control method in this invention; Figure 5 This is a schematic diagram of the blower control method in this invention; Figure 6 This is a schematic diagram of the hydrogen circulation pump control method in this invention; Figure 7 This is a schematic diagram of the hydrogen replenishment control method in this invention; Figure 8 This is a schematic diagram of the control method for the steam electric heater and the air electric heater in this invention; Figure 9 This is a schematic diagram of the gas flow control method in this invention.

[0029] Explanation of the labels in the diagram: 101. Water tank; 102. Water pump; 103. Water preheater; 104. Return water regulating valve; 105. Water evaporator; 106. Steam flow meter; 107. Steam check valve; 108. Mixer; 109. Steam heat exchanger; 110. Steam electric heater; 111. First heating tape; 201. Air filter element; 202. Blower; 203. Air flow meter; 204. Primary air heat exchanger; 205. Secondary air heat exchanger; 206. Electric air heater; 301. First hydrogen flow meter; 302. First hydrogen check valve; 303. Hydrogen circulation pump; 304. Second hydrogen flow meter; 305. Second hydrogen check valve; 306. Second heating tape; 401. Hydrogen source; 402. Hydrogen control valve; 403. Hydrogen flow controller; 404. Third hydrogen check valve; 501. Protective gas source; 502. Protective gas control valve; 503. Protective gas flow controller; 504. Protective gas check valve; 601, SOEC stack cathode; 602, SOEC stack anode; 701. First temperature sensor; 702. Second temperature sensor; 703. Third temperature sensor; 704. Fourth temperature sensor; 705. Oxygen sensor; 801. Gas flow controller; 802. Gas check valve; 803. Burner; 804. Multi-stream heat exchanger. Detailed Implementation

[0030] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings and embodiments.

[0031] The structures, proportions, and sizes illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and are not intended to limit the scope of the invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness or purpose of the invention, should still fall within the scope of the disclosed technical content. Similarly, terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and not intended to limit the scope of implementation. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention. In this invention, "connection" and "connection" refer to direct or indirect connections, as long as their functional purpose is achieved. For example, if the outlet of a hydrogen input component is connected to the cathode inlet, it is sufficient to allow hydrogen to be input to the cathode inlet.

[0032] Example 1 like Figure 1 As shown, this embodiment provides an SOEC water electrolysis system, including: An SOEC fuel cell stack consists of several SOEC stacks, each composed of several SOEC cells stacked in series. Each SOEC stack includes an SOEC anode 602 and an SOEC cathode 601. The SOEC anode 602 has an anode inlet and an anode outlet, while the cathode has a cathode inlet and a cathode outlet. An electrolysis reaction occurs at the SOEC cathode 601. Water vapor is introduced into the SOEC cathode 601 and generates hydrogen gas. The exhaust gas from the SOEC cathode 601 is a mixture of hydrogen and water vapor.

[0033] The water vapor input component has its inlet end connected to a water source and its outlet end connected to the cathode inlet. The water vapor input component is used to evaporate water and convert it into water vapor, and then input the water vapor into the SOEC stack cathode 601.

[0034] The air input component has its inlet end connected to the outside air and its outlet end connected to the anode inlet of the SOEC fuel cell stack. It can heat the incoming air from the outside and use it to input hot air into the SOEC fuel cell stack anode 602.

[0035] The hydrogen input component has its inlet end connected to the hydrogen source 401 and its outlet end connected to the cathode inlet, and is used to input hydrogen into the SOEC stack cathode 601.

[0036] The hydrogen output component has its inlet connected to the cathode outlet of the SOEC stack. It has two outlets: one outlet is connected to a hydrogen storage tank or hydrogen usage equipment, and the other outlet is connected to the cathode inlet, enabling the recycling of hydrogen.

[0037] The specific configuration of the aforementioned water vapor input component is as follows: It includes a water tank 101, a water pump 102, a water preheater 103, a water evaporator 105, a steam flow meter 106, and a steam check valve 107 connected in sequence.

[0038] Water tank 101 is connected to an external water source and is used to store water.

[0039] The inlet of the water pump 102 is connected to the water tank 101 and is used to transport water in the water tank 101 to the SOEC stack cathode 601.

[0040] The water preheater 103 includes a hot side and a cold side. Its cold side inlet is connected to the outlet of the water pump 102, and its hot side inlet is connected to the cathode outlet of the SOEC stack. This allows the cathode exhaust gas flowing through the hot side to exchange heat with the water flowing through the cold side. The water on the cold side acts as cooling water, which can cool down the cathode exhaust gas on the hot side and condense the water vapor in the cathode exhaust gas, separating it from the product hydrogen in the cathode exhaust gas. The hot side outlet is connected to the hydrogen output component, allowing the hydrogen separated from the cathode exhaust gas to flow to the hydrogen output component. The hot side outlet is also connected to the water tank 101 through a condensate branch, allowing the condensate after the water vapor is condensed to flow back to the water tank 101 and be used again as a cooling water and steam source.

[0041] The inlet of the water evaporator 105 is connected to the cold-side outlet of the water preheater 103, and is used to completely evaporate water into water vapor. Preferably, it is an electrically heated evaporator. Since the main purpose of the water preheater 103 is to completely cool the cathode exhaust gas, a large flow rate and a fast flow velocity of water need to be injected into the cold side of the water evaporator 105 to ensure the cooling effect. At the same time, since the heat of the cathode exhaust gas is limited, and the heat required to completely evaporate the water is too large, relying on the cooling water to exchange heat with the cathode exhaust gas in the water evaporator 105 is insufficient to completely evaporate the cooling water into water vapor, and can only increase the temperature of the cooling water to a certain extent. Therefore, a separate water evaporator 105 needs to be set downstream of the water preheater 103 to ensure that the incoming cooling water is completely evaporated into water vapor. This allows the downstream water vapor flow meter 106 to accurately count the water vapor flow rate entering the SOEC stack cathode 601, which facilitates the control of water vapor and ensures that the actual water vapor flow rate is consistent with the water vapor flow rate required for electrolysis. A fourth temperature sensor 704 is installed at the hot side outlet to measure the temperature of the hot side of the water preheater 103.

[0042] The inlet of the water vapor flow meter 106 is connected to the outlet of the water evaporator 105 and is used to measure the actual flow rate of water vapor delivered to the SOEC stack cathode 601.

[0043] The inlet of the steam check valve 107 is connected to the outlet of the steam flow meter 106, and the outlet is connected to the SOEC stack cathode 601. The mixing point of the input hydrogen and the input steam is located downstream of the check valve. Specifically, after the steam passes through the steam check valve 107, it mixes with the hydrogen in the mixer 108 and then flows together to the cathode inlet of the SOEC stack.

[0044] In the waste water return branch, to ensure sufficient cooling of the cathode exhaust gas, the flow rate of cooling water entering the water preheater 103 is typically greater than the steam flow rate required for electrolysis. In this case, the excess cooling water can be returned to the water tank 101 via the waste water return branch. Specifically, the inlet of the waste water return branch is connected between the water preheater 103 and the water evaporator 105, and the outlet is connected to the water tank 101. A return water regulating valve 104 is also installed on it to control the on / off state of the waste water return branch, allowing excess cooling water to return to the water tank 101 before evaporation, preventing excessive evaporation of cooling water in the water evaporator 105 and reducing energy consumption. The return water regulating valve 104 of the waste water return branch is communicatively connected to the steam flow meter 106, establishing a feedback regulation mechanism. This feedback regulation mechanism includes the control method of the water pump 102 and the regulation method of the return water regulating valve 104.

[0045] like Figure 3 As shown, the control method for water pump 102 is as follows: The temperature of the hot side of the water preheater 103 is measured by the fourth temperature sensor 704 and compared with the temperature required for water vapor condensation in the cathode tail gas. The cooling temperature required for the cathode tail gas is usually room temperature. This temperature difference deviation is input into the PI controller to calculate the cooling water flow rate required for water vapor condensation in the cathode tail gas.

[0046] Since the cooling water also serves as a source of water vapor, it is necessary to obtain the water vapor flow rate required for the electrolysis reaction, compare this flow rate with the required cooling water flow rate, and take the larger of the two as the system's required water flow rate. This ensures that the water vapor in the cathode tail gas is sufficiently cooled while also meeting the water vapor flow rate required for the electrolysis reaction.

[0047] The actual water flow rate input to the water pump 102 is measured, and the water pump 102 is adjusted through the PI controller to ensure that the water flow rate meets the system requirements; that is, when the actual water flow rate is less than the system's required water flow rate, the water supply of the water pump 102 per unit time is increased, and vice versa.

[0048] like Figure 4 As shown, the adjustment method for the return water regulating valve 104 is as follows: The opening requirement of the return water regulating valve 104 is calculated based on the difference between the required cooling water flow rate and the required steam flow rate, and is used as feedforward for the PI controller. The actual flow rate of steam delivered to the SOEC stack cathode 601 is measured by steam flow meter 106 and compared with the steam flow rate required for the electrolysis reaction. This deviation is input into the PI controller to calculate the opening control value of the return water regulating valve 104. When the actual steam flow rate is greater than the required steam flow rate, the opening of the return water regulating valve 104 is increased, and vice versa.

[0049] In summary, the water introduced into the system in this embodiment serves a dual purpose: it acts as cooling water for cooling the cathode exhaust gas in the water preheater 103, and as a source of steam for the SOEC stack to perform the electrolysis reaction. This eliminates the need for a separate condenser, reducing equipment costs. Furthermore, by connecting a waste water return branch between the water preheater 103 and the water evaporator 105, excess cooling water is returned to the water tank 101 before evaporation in the water evaporator 105 and before entering the steam flow meter 106. This not only allows for water reuse but also decouples the cooling water flow rate required for cathode exhaust gas cooling from the steam flow rate required for electrolysis, facilitating precise control of both flow rates.

[0050] In one embodiment, the steam input assembly further includes a steam heat exchanger 109 disposed downstream of the steam check valve 107. The steam heat exchanger 109 includes a hot side and a cold side. Its hot side inlet is connected to the cathode outlet of the SOEC stack, its hot side outlet is connected to the hot side inlet of the water preheater 103, its cold side inlet is connected to the outlet of the steam check valve 107, and its cold side outlet is connected to the cathode inlet of the SOEC stack. The steam and cathode exhaust gas can undergo preliminary heat exchange in the steam heat exchanger 109. On the one hand, this can increase the temperature of the steam, making it closer to the reaction temperature of the SOEC stack. On the other hand, it can initially reduce the temperature of the cathode exhaust gas, thereby reducing the cooling water flow rate required to cool the cathode exhaust gas.

[0051] In one embodiment, a first heating tape 111 is wrapped around the steam pipe between the water evaporator 105 and the steam heat exchanger 109. The first heating tape 111 can be an electric heating tape sleeved outside the pipe to prevent water vapor condensation. The power of the first heating tape 111 is adjusted according to the water vapor temperature in the pipe to ensure that the cold side inlet temperature of the steam heat exchanger 109 is not lower than 200°C.

[0052] In one embodiment, the steam input assembly further includes a steam electric heater 110 disposed downstream of the steam heat exchanger 109. The outlet of the steam electric heater 110 is connected to the cathode inlet of the SOEC stack to provide a final temperature boost before the steam enters the cathode inlet, so that the steam temperature meets the temperature required for the reaction.

[0053] The SOEC stack is equipped with a second temperature sensor 702 at both the cathode inlet and cathode outlet to measure the temperature of the SOEC stack cathode 601. The second temperature sensor 702 is communicatively connected to the steam electric heater 110, thus establishing a feedback regulation mechanism between the temperature of the SOEC stack cathode 601 and the steam electric heater 110.

[0054] like Figure 8 As shown, the control method of the steam electric heater 110 is as follows: the actual temperature of the SOEC stack cathode 601 is measured by the second temperature sensor 702 and compared with the required temperature of the SOEC stack cathode 601. This deviation is input into the PI controller to calculate the required temperature of the steam electric heater 110 outlet. This temperature is compared with the highest set temperature of the steam electric heater 110, and the smaller value between the two is taken as the input of the steam electric heater 110. The PI controller adjusts the steam electric heater 110 to ensure that the temperature of the SOEC stack cathode 601 meets the requirements.

[0055] Example 2 Based on the above embodiments, this embodiment provides several preferred implementations of the air input component.

[0056] In one embodiment, the air input assembly includes at least an air primary heat exchanger 204, which includes a cold side and a hot side. The hot side is connected to the waste water return branch, and the cold side is used to supply air, so that excess cooling water can exchange heat with the air. On the one hand, this increases the air temperature, bringing it closer to the reaction temperature of the SOEC stack. On the other hand, it reduces the temperature of the cooling water returning to the water tank 101, thereby improving the cooling effect on the cathode exhaust gas and further reducing the cooling water flow rate required for cooling the cathode exhaust gas.

[0057] In one embodiment, the air input assembly further includes an air filter 201, a blower 202, an air flow meter 203, and a secondary air heat exchanger 205 arranged sequentially along the airflow direction. The outlet of the secondary air heat exchanger 205 is connected to the anode inlet of the SOEC fuel cell stack. A primary air heat exchanger 204 is disposed between the air flow meter 203 and the secondary air heat exchanger 205. The secondary air heat exchanger 205 includes a cold side and a hot side. The cold side inlet is connected to the outlet of the primary air heat exchanger 204, and the cold side outlet is connected to the anode inlet of the SOEC fuel cell stack. The hot side inlet is connected to the anode outlet of the SOEC fuel cell stack, so that the anode exhaust gas exchanges heat with the air. The air input process is as follows: the blower 202 delivers outside air to the anode inlet of the SOEC fuel cell stack. The outside air is filtered by the air filter 201 and then heated by the primary air heat exchanger 204 and the secondary air heat exchanger 205.

[0058] Furthermore, an oxygen sensor 705 is also installed at the anode outlet of the SOEC stack. The oxygen sensor 705 is communicatively connected to the blower 202, that is, a feedback regulation mechanism is established between the oxygen sensor 705 and the blower 202.

[0059] like Figure 5 As shown, the control method for blower 202 is as follows: The required airflow rate to the SOEC fuel cell stack is calculated based on the product gas demand flow rate and the required oxygen concentration at the anode outlet of the SOEC stack, serving as feedforward for the PI controller. The oxygen concentration at the anode outlet of the SOEC stack is measured using an oxygen sensor 705 and compared with the required oxygen concentration. This deviation is input into the PI controller to calculate the required airflow rate for the SOEC stack. The actual airflow rate of the system is measured using an airflow meter 203, and the blower 202 is adjusted by the PI controller to ensure that the airflow rate meets the system requirements. That is, when the required airflow rate is greater than the actual airflow rate, the airflow rate of the blower 202 is increased; conversely, the airflow rate of the blower 202 is decreased.

[0060] The formula for calculating the feedforward of the PI controller is:

[0061] In the formula: B is the air flow rate required to enter the SOEC stack, in NL / min; A is the product gas flow rate, in NL / min; X is the oxygen concentration required, 25% to 35%.

[0062] In one embodiment, the air input component further includes an air electric heater 206 disposed between the secondary air heat exchanger 205 and the anode inlet. Both the anode inlet and anode outlet of the SOEC stack are provided with a first temperature sensor 701, which is communicatively connected to the air electric heater 206, that is, a feedback regulation mechanism is established between the first temperature sensor 701 and the air electric heater 206.

[0063] like Figure 8 As shown, the control method of the air electric heater 206 is as follows: The actual temperature of SOEC fuel cell anode 602 is measured and compared with the required temperature of SOEC fuel cell anode 602. This deviation is input into the PI controller to calculate the required temperature of the air heater 206 outlet. This temperature is compared with the maximum set temperature of air heater 206, and the smaller value is taken as the input of air heater 206. The PI controller is used to adjust air heater 206 to ensure that the temperature of SOEC fuel cell anode 602 meets the requirements.

[0064] like Figure 5 As shown, when an air heater 206 is installed, to ensure that the air heater 206 does not overheat, the aforementioned blower 202 control method requires setting a minimum airflow rate. This minimum airflow rate is compared with the airflow rate required by the SOEC fuel cell stack, and the larger of the two values ​​is taken as the system's required airflow rate. The actual airflow rate of the system is measured, and the blower 202 is adjusted via a PI controller to ensure that the airflow rate meets the system requirements. That is, when the required airflow rate is greater than the actual airflow rate, the blower 202's airflow rate is increased; conversely, when the required airflow rate is less than the actual airflow rate, the blower 202's airflow rate is decreased, but it must not fall below the minimum airflow rate.

[0065] Example 3 like Figure 2As shown, based on the above embodiments, the SOEC water electrolysis system further includes a gas input component. The gas includes a gas flow controller 801, a gas check valve 802, and a burner 803 arranged sequentially along the gas delivery direction. One port of the burner 803 is connected to the anode outlet of the SOEC stack. The anode exhaust gas contains a large amount of oxygen, providing conditions for gas combustion. In this case, the air electric heater 206 and the steam electric heater 110 in the above embodiments can be replaced with a multi-flow heat exchanger 804. The multi-flow heat exchanger 804 is provided with a first heat exchange chamber, a second heat exchange chamber, and a third heat exchange chamber. The inlet of the first heat exchange chamber is connected to the exhaust gas outlet of the burner 803, and the outlet is connected to the hot side inlet of the air secondary heat exchanger 205. The inlet of the second heat exchange chamber is connected to the cold side outlet of the steam heat exchanger 109, and the outlet is connected to the cathode inlet of the SOEC stack. The inlet of the third heat exchange chamber is connected to the cold side outlet of the air secondary heat exchanger 205, and the outlet is connected to the anode inlet of the SOEC stack. The exhaust gas generated by the combustion of gas heats water vapor and air. After heat exchange, the exhaust gas enters the secondary air heat exchanger 205 to continue exchanging heat with the upstream air.

[0066] In this embodiment, a first temperature sensor 701 is installed at both the anode inlet and anode outlet of the SOEC fuel cell stack, a second temperature sensor 702 is installed at both the cathode inlet and cathode outlet of the SOEC fuel cell stack, and a third temperature sensor 703 is installed at the exhaust gas outlet of the burner 803. The first temperature sensor 701, the second temperature sensor 702 and the third temperature sensor 703 are connected in communication to establish a feedback regulation mechanism between the gas flow rate and the SOEC fuel cell stack temperature.

[0067] like Figure 9 As shown, the gas flow control method is as follows: The actual temperature of the SOEC fuel cell stack is measured by the first temperature sensor 701 and the second temperature sensor 702, and compared with the required temperature of the SOEC fuel cell stack. This deviation is input into the PI controller to calculate the required temperature of the burner 803 outlet. This temperature is compared with the highest set temperature of the burner 803 outlet, and the smaller value is taken as the required outlet temperature of the burner 803. The actual temperature of the burner 803 outlet is measured by the third temperature sensor 703, and the gas flow rate is calculated by the PI controller. The gas flow controller 801 is adjusted to make the actual temperature consistent with the required temperature, so as to ensure that the SOEC fuel cell stack temperature meets the requirements.

[0068] Example 4 Based on the above embodiments, the hydrogen output component in this embodiment includes an output branch and a return branch connected to the hot-side outlet of the water preheater 103. The outlet of the output branch is connected to a hydrogen storage tank or other hydrogen-using device, and a first hydrogen check valve 302 and a first hydrogen flow meter 301 are sequentially arranged along the hydrogen flow direction on the output branch. The outlet of the return branch is connected to the outlet of the steam check valve 107, which is used to re-input some of the product hydrogen into the SOEC stack cathode 601 after the system stabilizes, saving the external hydrogen source 401; specifically, a hydrogen circulation pump 303, a second hydrogen flow meter 304, and a second hydrogen check valve 305 are sequentially arranged along the hydrogen flow direction on the return branch, and the hydrogen flowing out of the second hydrogen check valve 305 is mixed with the steam flowing out of the steam check valve 107 in the mixer 108.

[0069] like Figure 6 As shown, the control method for the hydrogen circulation pump 303 is as follows: The required flow rate of mixed hydrogen is calculated by the steam flow rate required for the electrolysis reaction, and the flow rate of hydrogen produced by the electrolysis reaction is calculated by the current value. The smaller of the two values ​​is taken as the required flow rate of circulating hydrogen. The actual flow rate of circulating hydrogen is measured, and the hydrogen circulation pump 303 is adjusted by a PI controller. That is, when the required flow rate of circulating hydrogen is less than the actual flow rate of circulating hydrogen, the speed of hydrogen circulation pump 303 is reduced, and vice versa.

[0070] The method for calculating the required flow rate of blended hydrogen is as follows:

[0071] Where: V1, required flow rate of blended hydrogen, in NL / min; Q, required flow rate of water vapor, in kg / h; K1, coefficient, 1.1.

[0072] The method for calculating the flow rate of hydrogen produced by electrolysis is as follows:

[0073] Where: V2, hydrogen flow rate generated by electrolysis, in NL / min; I, single cell current; n, number of cells in the SOEC stack; Faraday efficiency, 95%–99%; K2 coefficient, 0.007.

[0074] Furthermore, a second heating tape 306 is installed on the return branch. Since there is still a certain amount of water vapor remaining in the returned hydrogen, in order to prevent water vapor from condensing in the pipeline, valve or the second hydrogen flow meter 304, affecting the measurement accuracy and the operation of the hydrogen circulation pump 303, the second heating tape 306 is used to heat the pipeline, with the pipe wall heating temperature at 30-60℃.

[0075] Example 5 Based on the above embodiments, in this embodiment, the inlet of the hydrogen input component is connected to the hydrogen source 401 to provide hydrogen to the SOEC stack initially, and can also supplement hydrogen when the circulating hydrogen flow is insufficient during the reaction process; the hydrogen source 401 can be set as a hydrogen cylinder. Specifically, the hydrogen input component includes a hydrogen control valve 402, a hydrogen flow controller 403, and a third hydrogen check valve 404 arranged sequentially along the hydrogen input direction, and the outlet of the third hydrogen check valve 404 is connected to the outlet of the water vapor check valve 107.

[0076] like Figure 7 As shown, the hydrogen replenishment control method is as follows: the required flow rate of mixed hydrogen is calculated based on the required flow rate of water vapor, the actual flow rate of circulating hydrogen is measured, and the difference between the two is used as the required flow rate of replenished hydrogen. The hydrogen flow rate is adjusted by the hydrogen flow controller 403.

[0077] Example 6 Based on the above embodiments, the SOEC water electrolysis system in this embodiment further includes a protective gas input component, the inlet of which is connected to a protective gas source 501 for inputting protective gas into the SOEC stack cathode 601; the protective gas source 501 can be configured as a protective gas cylinder, and the protective gas can be nitrogen. Specifically, the protective gas input component includes a protective gas control valve 502, a protective gas flow controller 503, and a protective gas check valve 504 arranged sequentially along the protective gas input direction, and the outlet of the protective gas check valve 504 is connected to the outlet of the water vapor check valve 107.

[0078] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A SOEC water electrolysis system, comprising: SOEC fuel cell stack, a steam input component for inputting water vapor into SOEC fuel cell stack cathode (601), an air input component for inputting air into SOEC fuel cell stack anode (602), a hydrogen input component for inputting hydrogen into SOEC fuel cell stack cathode (601), a protective gas input component for inputting protective gas into SOEC fuel cell stack cathode (601), and a hydrogen output component for collecting product hydrogen. The water vapor input component is characterized by comprising: Water tank (101), connected to an external water source, is used to store water; A water pump (102) with its inlet connected to a water tank (101) is used to deliver water to the SOEC stack cathode (601); The water preheater (103) includes a hot side and a cold side. The cold side inlet is connected to the outlet of the water pump (102), and the hot side inlet is connected to the cathode outlet of the SOEC stack. The cathode exhaust gas flowing through the hot side exchanges heat with the water flowing through the cold side to preheat the water and condense the water vapor in the cathode exhaust gas. The hot side outlet is connected to the hydrogen output assembly, so that the hydrogen flows to the hydrogen output assembly. The hot side outlet is also connected to the water tank (101) through a condensate branch, so that the condensate flows back to the water tank (101). A fourth temperature sensor (704) is provided at the hot side outlet. The water evaporator (105) has its inlet connected to the cold-side outlet of the water preheater (103) for completely evaporating water into water vapor; A water vapor flow meter (106) is connected at its inlet to the outlet of a water evaporator (105) and is used to measure the actual flow rate of water vapor delivered to the SOEC stack cathode (601). The steam check valve (107) has its inlet connected to the outlet of the steam flow meter (106) and its outlet connected to the SOEC stack cathode (601). The mixing point of the input hydrogen and the input steam is located downstream of the check valve. The excess water return branch is used to return the excess cooling water in the water preheater (103) to the water tank (101); its inlet is connected between the water preheater (103) and the water evaporator (105), and its outlet is connected to the water tank (101). It is also equipped with a return water regulating valve (104) for controlling the opening and closing of the excess water return branch. The return water regulating valve (104) is communicatively connected to the water vapor flow meter (106).

2. The SOEC water electrolysis system according to claim 1, characterized in that: The steam input assembly also includes a steam heat exchanger (109) located downstream of the steam check valve (107). The steam heat exchanger (109) includes a hot side and a cold side. Its hot side inlet is connected to the cathode outlet of the SOEC stack, its hot side outlet is connected to the hot side inlet of the water preheater (103), its cold side inlet is connected to the outlet of the steam check valve (107), and its cold side outlet is connected to the cathode inlet of the SOEC stack to reduce the cathode exhaust gas temperature and increase the steam temperature.

3. The SOEC water electrolysis system according to claim 2, characterized in that: The steam pipe between the water evaporator (105) and the water steam heat exchanger (109) is wrapped with a first heat tracing tape (111) to prevent water steam from condensing. Preferably, the steam input assembly further includes a steam electric heater (110) disposed downstream of the steam heat exchanger (109), the outlet of which is connected to the cathode inlet of the SOEC stack; The SOEC stack is equipped with a second temperature sensor (702) at both the cathode inlet and cathode outlet. The second temperature sensor (702) is communicatively connected to the steam electric heater (110).

4. The SOEC water electrolysis system according to claim 2, characterized in that: The air input assembly includes at least an air primary heat exchanger (204), which includes a cold side and a hot side. The hot side inlet is connected to a return water regulating valve (104), the hot side outlet is connected to a water tank (101), the cold side inlet is connected to the inlet end of the air input assembly, and the cold side outlet is connected to the inlet of the SOEC stack anode (602).

5. The SOEC water electrolysis system according to claim 4, characterized in that: The air input assembly also includes an air filter (201), a blower (202), an air flow meter (203), and a secondary air heat exchanger (205) arranged sequentially along the air flow direction. The outlet of the secondary air heat exchanger (205) is connected to the anode inlet of the SOEC stack. The primary air heat exchanger (204) is located between the air flow meter (203) and the secondary air heat exchanger (205). The air secondary heat exchanger (205) includes a cold side and a hot side. The cold side inlet is connected to the cold side outlet of the air primary heat exchanger (204), the cold side outlet is connected to the anode inlet of the SOEC stack, and the hot side inlet is connected to the anode outlet of the SOEC stack, so that the anode exhaust gas can exchange heat with the air. Preferably, the anode outlet of the SOEC stack is also equipped with an oxygen sensor (705), which is communicatively connected to the blower (202).

6. The SOEC water electrolysis system according to claim 5, characterized in that: The air input assembly also includes an air electric heater (206) disposed between the secondary air heat exchanger (205) and the anode inlet. The anode inlet and anode outlet of the SOEC stack are both equipped with a first temperature sensor (701), which is communicatively connected to the air electric heater (206).

7. The SOEC water electrolysis system according to claim 5, characterized in that: It also includes a gas input component, The gas input assembly includes a gas flow controller (801), a gas check valve (802), and a burner (803) arranged sequentially along the gas delivery direction. One port of the burner (803) is connected to the anode outlet of the SOEC stack to provide oxygen for gas combustion. Preferably, the gas input assembly further includes a multi-flow heat exchanger (804), which is provided with a first heat exchange chamber, a second heat exchange chamber, and a third heat exchange chamber; the inlet of the first heat exchange chamber is connected to the exhaust gas outlet of the burner (803), and the outlet is connected to the hot side inlet of the air secondary heat exchanger (205); the inlet of the second heat exchange chamber is connected to the cold side outlet of the steam heat exchanger (109), and the outlet is connected to the cathode inlet of the SOEC stack; the inlet of the third heat exchange chamber is connected to the cold side outlet of the air secondary heat exchanger (205), and the outlet is connected to the anode inlet of the SOEC stack. Preferably, a first temperature sensor (701) is provided at both the anode inlet and anode outlet of the SOEC fuel cell stack, a second temperature sensor (702) is provided at both the cathode inlet and cathode outlet of the SOEC fuel cell stack, and a third temperature sensor (703) is installed at the exhaust gas outlet of the burner (803). The first temperature sensor (701), the second temperature sensor (702) and the third temperature sensor (703) are connected in communication.

8. The SOEC water electrolysis system according to claim 1, characterized in that: The hydrogen output assembly includes an output branch and a return branch connected to the hot side outlet of the water preheater (103); A first hydrogen check valve (302) and a first hydrogen flow meter (301) are sequentially installed along the hydrogen flow direction on the output branch. A hydrogen circulation pump (303), a second hydrogen flow meter (304), and a second hydrogen check valve (305) are sequentially installed along the hydrogen flow direction on the return branch. The second hydrogen check valve (305) is connected to the outlet of the water vapor check valve (107). A second heat tracing cable (306) is installed on the return branch to prevent residual water vapor in the return gas from condensing. Preferably, the inlet of the hydrogen input component is connected to the hydrogen source (401), and the hydrogen input component includes a hydrogen control valve (402), a hydrogen flow controller (403) and a third hydrogen check valve (404) arranged sequentially along the hydrogen input direction, and the outlet of the third hydrogen check valve (404) is connected to the outlet of the water vapor check valve (107). Preferably, it also includes a protective gas input component, the inlet of which is connected to a protective gas source (501) for inputting protective gas into the SOEC stack cathode (601); The protective gas input assembly includes a protective gas control valve (502), a protective gas flow controller (503), and a protective gas check valve (504) arranged sequentially along the protective gas input direction. The outlet of the protective gas check valve (504) is connected to the outlet of the steam check valve (107).

9. A control method for an SOEC water electrolysis system according to any one of claims 1-8, characterized in that: The control method for water pump (102) is as follows: The temperature of the hot side of the water preheater (103) is measured and compared with the required temperature for water vapor condensation. This temperature difference is input into the PI controller to calculate the cooling water flow rate required for water vapor condensation in the cathode tail gas. Obtain the steam flow rate required for the electrolysis reaction, compare this flow rate with the cooling water flow rate, and take the larger of the two values ​​as the system's required water flow rate; The actual water flow rate input to the water pump (102) is measured, and the water pump (102) is adjusted through the PI controller to ensure that the water flow rate meets the system requirements; Preferably, the adjustment method of the return water regulating valve (104) is as follows: The opening requirement of the return water regulating valve (104) is calculated based on the difference between the required cooling water flow rate and the required steam flow rate, and is used as feedforward for the PI controller. The actual flow rate of water vapor delivered to the SOEC stack cathode (601) is measured and compared with the water vapor flow rate required for the electrolysis reaction. This deviation is input into the PI controller to calculate the opening control quantity of the return water regulating valve (104). When the actual flow rate of water vapor is greater than the required flow rate of water vapor, the opening of the return water regulating valve (104) is increased, and vice versa.

10. The control method according to claim 9, characterized in that: The control method for the blower (202) is as follows: The required air flow rate to be introduced into the SOEC fuel cell is calculated based on the product gas demand flow rate and the oxygen demand concentration at the anode outlet of the SOEC fuel cell, and is used as feedforward for the PI controller; the actual oxygen concentration at the anode outlet of the SOEC fuel cell is measured and compared with the oxygen demand concentration, and this deviation is input into the PI controller to calculate the required air flow rate of the SOEC fuel cell. Preferably, in the operating state, in order to ensure that the air electric heater (206) does not overheat, a minimum air flow rate needs to be set. The minimum air flow rate is compared with the air flow rate required by the SOEC stack, and the larger value of the two is taken as the air flow rate required by the system. The actual air flow rate of the system is measured, and the blower (202) is adjusted by the PI controller to ensure that the air flow rate meets the system requirements. The formula for calculating the feedforward of the PI controller is: In the formula: B, the air flow rate required to enter the SOEC stack, in NL / min; A, the product gas flow rate, in NL / min; X, the required oxygen concentration, 25%–35%; Preferably, the control method for the hydrogen circulation pump (303) is as follows: The required flow rate of mixed hydrogen is calculated by the water vapor flow rate required for the electrolysis reaction, and the flow rate of hydrogen produced by the electrolysis reaction is calculated by the current value. The smaller of the two values ​​is taken as the required flow rate of circulating hydrogen. The actual flow rate of circulating hydrogen is measured, and the hydrogen circulation pump (303) is adjusted by the PI controller. Preferably, the hydrogen replenishment control method is as follows: The required flow rate of mixed hydrogen is calculated by the required flow rate of water vapor, the actual flow rate of circulating hydrogen is measured, and the difference between the two is used as the required flow rate of supplementary hydrogen. The hydrogen flow rate is adjusted by the hydrogen flow controller (403). The method for calculating the required flow rate of blended hydrogen is as follows: Where: V1, required flow rate of blended hydrogen, in NL / min; Q, required flow rate of water vapor, in kg / h; K1, coefficient, 1.1; The method for calculating the flow rate of hydrogen produced by electrolysis is as follows: Where: V2 is the flow rate of hydrogen produced by electrolysis, in NL / min; I. Single cell current; n. Number of cells in the SOEC stack; Faraday efficiency, 95%–99%; K² coefficient, 0.007; Preferably, the control method for the steam electric heater (110) is as follows: The actual temperature of the SOEC stack cathode (601) is measured and compared with the required temperature of the SOEC stack cathode (601). This deviation is input into the PI controller to calculate the required temperature of the steam electric heater (110) outlet. This temperature is compared with the maximum set temperature of the steam electric heater (110), and the smaller value is taken as the input of the steam electric heater (110). The steam electric heater (110) is adjusted by the PI controller to ensure that the temperature of the SOEC stack cathode (601) meets the requirements. Preferably, the control method for the air electric heater (206) is as follows: The actual temperature of the SOEC fuel cell anode (602) is measured and compared with the required temperature of the SOEC fuel cell anode (602). This deviation is input into the PI controller to calculate the required temperature of the air heater (206) outlet. This temperature is compared with the maximum set temperature of the air heater (206), and the smaller value is taken as the input of the air heater (206). The air heater (206) is adjusted by the PI controller to ensure that the temperature of the SOEC fuel cell anode (602) meets the requirements. Preferably, the gas flow control method is as follows: The actual temperature of the SOEC fuel cell stack is measured and compared with the required temperature of the SOEC fuel cell stack. This deviation is input into the PI controller to calculate the required temperature of the burner (803) outlet. This temperature is compared with the highest set temperature of the burner (803) outlet, and the smaller value is taken as the required outlet temperature of the burner (803). The actual temperature of the burner (803) outlet is measured, and the gas flow rate is calculated by the PI controller. The gas flow controller (801) is adjusted to ensure that the SOEC fuel cell stack temperature meets the requirements.

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