A solid oxide electrolysis hydrogen production system without auxiliary equipment and auxiliary coal-fired power deep adjustment method

Abstract

The present invention relates to the field of hydrogen energy technology, and discloses a non-auxiliary solid oxide electrolysis hydrogen production system and an auxiliary coal-fired power deep regulation method. The hydrogen production system includes a SOE hot box system for electrolytic hydrogen production, a hydrogen circulation subsystem, and a hydrogen storage subsystem; an ejector is driven by steam from an external heat source, and part of the hydrogen at the outlet of the SOE hot box system is injected through the hydrogen circulation subsystem to the low-pressure suction port of the ejector, forming a reducing mixture of steam and hydrogen that enters the cathode inlet of the SOE hot box system. The present invention adopts an external heat source drive and an internal stack heat release mode to reduce the power consumption of the electrolytic hydrogen production system; adopts an external material supply, cathode ejector material self-circulation, and a multi-stream heat exchange method to eliminate the complex cold and hot auxiliary equipment of the traditional solid oxide electrolysis hydrogen production system, simplify the structure, and greatly improve the compactness of the system; by establishing an electricity-steam-air-condensate process coupling with a coal-fired power plant, combined with multi-stage steam extraction adjustment, efficient and flexible deep peak regulation.

Description

Technical Field

[0001] The present invention relates to the field of hydrogen energy technology, and in particular to a solid oxide electrolysis hydrogen production system without auxiliary machinery and an auxiliary coal-fired power deep regulation method. Background Art

[0002] The maximum peak-shaving capacity of conventional coal-fired power plants is limited by the minimum technical output (about 30% of the rated load). As the proportion of wind and solar energy installed capacity continues to increase, in order to ensure the smooth and safe operation of the power grid, it is urgent to develop ultra-low load deep peak-shaving technology for thermal power plants and further explore the peak-shaving depth limit and operation mode of the units.

[0003] Deep peaking at ultra-low loads in coal-fired power plants faces numerous challenges. For example, boilers suffer from poor combustion stability when operating at low loads, making them prone to incomplete combustion and even flameout, limiting the plant's minimum technical output. Furthermore, injecting oil for stable combustion reduces the plant's peaking economics. Configuring electricity storage is expensive, and single-energy interaction alone cannot improve the plant's peaking capacity. Configuring heat storage for simple thermal-electrical decoupling can improve the unit's low-load heating capacity, but it struggles to improve its electrical peaking capacity. Deeply coupling heat storage with the power plant requires modifications to the plant's thermal system, impacting plant reliability and requiring significant investment. To further increase the depth of peaking, some units employ start-stop peaking, but this has drawbacks such as lengthy start-stop processes, insufficient flexibility, and poor economics. Therefore, there is an urgent need to develop new, efficient, and flexible technologies for deep peaking in coal-fired power plants.

[0004] In the existing literature, Sun Y, Wang L, Xu C, et al. Enhancing the operational flexibility of thermal power plants by coupling high-temperature power-to-gas[J]. Applied Energy, 2020, 263: 114608., a new energy power consumption model that coordinates coal-fired power plants with electrolysis energy storage is proposed. For the first time, the peak-shaving flexibility of coal-fired units is improved by combining the SOE hydrogen production system with the coal-fired power plant. However, it fails to provide a flexible coupling scheme and control method for time-sharing and segmented steam extraction based on the principle of "grade matching and cascade utilization". In addition, the SOE system adopted is based on an independent SOE system, which makes the equipment complicated, the investment cost high, and the application economy limited.

[0005] A Chinese patent, publication number CN212642819U, discloses a flexible peak-shaving system that couples high-temperature solid oxide water electrolysis with a power plant. This system, equipped with an independent SOE hydrogen production system as an additional plant load, can enhance the flexible peak-shaving capabilities of thermal power units. However, the power plant and SOE system are only electrically connected, failing to leverage the benefits of coupling their energy-to-mass conversion processes to improve the plant's low-load operating capacity. Furthermore, the use of electric heaters and other components to heat the SOE's inlet materials significantly reduces energy efficiency. Furthermore, the independent SOE system itself is complex, with numerous cooling and heating auxiliary units and startup units, resulting in high investment costs and limited reliability.

[0006] The existing Chinese patent with publication number CN116247727A discloses a power generation system coupled with a coal-fired unit and a SOEC and its operation method. The system includes a coal-fired power generation system and a SOE peak-shaving and frequency-regulating system. The invention adopts the method of extracting steam from the coal-fired power generation system by ejecting the extracted steam and electrolyzing the ejected steam. According to the requirements of the power grid, the current density of the SOE peak-shaving and frequency-regulating system is controlled, and then the coal-fired power generation system is peak-shaving and frequency-regulating is performed. The oxygen generated by electrolyzing water vapor assists the boiler to burn stably under low-load conditions, thereby improving the variable load capacity of the unit under low-load operation mode. However, in this invention, the necessary hydrogen is not introduced into the cathode side of the electrolytic stack to maintain a reducing atmosphere, and the electrolytic stack body lacks a thermal management medium for effective cooling. An electric heater is used to heat the material, which limits the stability of the stack electrode, the operating current density, and the hydrogen production efficiency of the SOE. It cannot solve the problem of high investment in SOE equipment and has limited application potential.

[0007] A Chinese patent, publication number CN117090647A, discloses a coal-fired power generation system coupled with a SOEC and a method for deep peak-shaving operation of the unit. The system comprises a thermal system for the coal-fired generator unit, a solid oxide electrolytic cell, and a molten salt heat storage coupling system. This invention utilizes heat extraction steam throttling to increase the flow of working fluid in the high- and intermediate-pressure cylinders during low-load operation of the power plant, improving turbine cylinder efficiency. By coupling the molten salt heat storage system with the SOE system, this improves the low-load combustion stability of the boiler, significantly enhancing the flexibility of the deep peak-shaving process for the coal-fired generator unit. However, in this technical solution, the temperature of molten salt heat storage is limited, which is 150-200℃ lower than the operating temperature of the electrolytic stack, making it difficult to meet the inlet material temperature requirements for efficient and safe operation of the electrolytic stack; the high and medium pressure cylinder extraction steam used does not match the SOE steam temperature and pressure requirements; the SOE system uses an independent SOE system configuration, and cooling auxiliary equipment such as pumps and fans cannot be cancelled. The heat exchange load of the heat exchanger is large, and the lava heat storage and SOE system are integrated at the same time. The energy storage system is complex, the investment cost is high, the implementation is difficult, and the economy and application potential are limited. Summary of the Invention

[0008] In order to overcome or alleviate one or more of the above technical problems, the purpose of the present invention is to provide a solid oxide electrolysis hydrogen production system without auxiliary equipment and an auxiliary coal-fired power deep adjustment method. Leveraging existing equipment from coal-fired power plants, the SOE hydrogen production system is supplied with low-pressure steam extraction from the steam turbine and high-temperature air from the boiler air preheater. A small amount of hydrogen product is directly injected using the extraction steam to maintain a reducing atmosphere at the SOE cathode. This eliminates all low-temperature auxiliary equipment, including fans, water pumps, steam generators, and hydrogen circulation pumps, that are essential in existing standalone SOE systems, significantly reducing operating equipment costs. The electrolytic stack operates in an exothermic mode, with the stack outlet stream entering a heat exchanger to heat the air and steam to the stack operating temperature, eliminating high-temperature components such as high-temperature electric heaters, which are prone to failure. Some unreacted steam is directly injected using the extraction steam, thereby increasing the steam conversion rate of the SOE system and reducing total extraction steam consumption. While maintaining a lower heat exchange load than a standalone SOE system, an optimized, more compact multi-flow plate heat exchanger is utilized to further improve heat exchange efficiency, reduce heat loss, reduce heat exchanger area, and increase the outlet oxygen-enriched air temperature. Excess heat from the hydrogen / steam outlet is used to heat the power plant feedwater. Multi-stage adjustment of the extraction steam position enables energy efficiency and flexible coordinated control of the ejector and the entire system under all operating conditions.

[0009] The present invention provides the following technical solutions:

[0010] A system for producing hydrogen from solid oxide electrolysis without auxiliary equipment, characterized in that it comprises a SOE hot box system for producing hydrogen by electrolysis, a hydrogen circulation subsystem and a hydrogen storage subsystem; steam introduced from an external heat source is input to the high-pressure inlet of an ejector (25), and then part of the hydrogen produced by the SOE hot box system is ejected to the low-pressure suction port of the ejector (25) through the hydrogen circulation subsystem, and a mixed gas of reducing steam and hydrogen is formed by the ejector (25) and enters the cathode inlet of the SOE hot box system after passing through the mixed outlet of the ejector (25), and the remaining hydrogen produced by the SOE hot box system is stored through the hydrogen storage subsystem; the SOE hot box system comprises a heat exchanger and a fuel cell (29), the fuel cell (29) operates in an exothermic mode, and the outlet logistics of the fuel cell (29) are all input to the heat exchanger again to heat the air and steam to the operating temperature of the fuel cell (29) respectively.

[0011] By eliminating the prone-to-failure cooling and heating auxiliary units, utilizing pressurized steam to inject hydrogen / unreacted steam, utilizing existing high-temperature air to reduce heat exchange loads, and optimizing multi-stream heat exchange, the above-described implementation significantly simplifies, compacts, and improves reliability of the SOE hydrogen production system, significantly reducing investment in the SOE hydrogen production system. In addition to coal-fired power plants, the external heat source can also include traditional fuel heat sources such as coal-fired boilers, new energy sources such as concentrated solar thermal power plants and geothermal energy, industrial waste heat from metallurgy and ironmaking, nuclear energy sources such as nuclear power plants, and other waste heat from urban areas.

[0012] According to some embodiments, the external heat source includes a coal-fired power plant, which includes a boiler subsystem and a steam turbine subsystem. The auxiliary-free solid oxide electrolysis hydrogen production system is coupled to the coal-fired power plant, and the coupling includes cathode reactant supply, anode reactant supply, power supply, anode product utilization and cathode waste heat utilization: the cathode reactant supply is to extract at least one steam from the steam turbine subsystem to the high-pressure inlet of the ejector (25), and then to inject part of the product produced by the SOE hot box system to the low-pressure suction port of the ejector (25) through the hydrogen circulation subsystem, and to form a reducing steam and hydrogen mixture through the ejector (25), and then enter the SOE after passing through the mixed outlet of the ejector (25). The cathode inlet of the SOE hot box system, the remaining products produced by the SOE hot box system are stored through the hydrogen storage subsystem after gas-water separation; the anode reactant supply is to input part of the hot air from the boiler subsystem into the SOE hot box system; the power supply is to input part of the electric energy generated by the steam turbine subsystem into the SOE hot box system; the anode product utilization is to input the high-temperature oxygen-rich air generated by the anode of the SOE hot box system into the boiler subsystem; the cathode waste heat utilization is to use the heat released by the cathode product in the gas-water separator (30) of the hydrogen storage subsystem to heat a stream of condensate from the condensate pump of the steam turbine subsystem, and the condensate is returned to the deaerator (10) after preheating.

[0013] The beneficial effects of the above-mentioned implementation method are as follows: by coupling the SOE hydrogen production system with the coal-fired power plant, when the power plant is deeply peak-shaving, while using the SOE hydrogen production as the plant power load to consume excess coal-fired power, the high-temperature oxygen-rich hot air at the outlet of the SOE system is mixed into the boiler secondary air, thereby increasing the heat and stable combustion performance of the air entering the boiler at low load. With almost no modification to the power plant itself, the technical minimum output of the power plant is reduced, and further, through the optimization of the ratio and coordinated operation of the coal-fired power plant and the SOE system, the peak-shaving capacity and speed of the coal-fired power plant are simultaneously improved, and an ultra-deep regulation method is achieved in which the coupled system is lower than the minimum technical output of the coal-fired power plant, providing a new technical solution for coal-fired power plants to participate in the deep peak-shaving of new power systems with a high proportion of renewable energy.

[0014] According to some embodiments, the mixed gas at the mixed outlet of the ejector (25) passes through the throttle valve (26) and the heat exchanger, and then enters the cathode inlet of the fuel cell stack (29). The hydrogen produced by the fuel cell stack (29) is output from the cathode outlet and passes through the heat exchanger again, and part of the hydrogen is input into the low-pressure inlet of the ejector (25), and the other part is input into the hydrogen storage subsystem.

[0015] According to some embodiments, the high-temperature air drawn out from the boiler of the boiler subsystem enters the heat exchanger and the anode inlet of the fuel cell stack (29) in sequence after dust removal, and the high-temperature air output from the anode outlet of the fuel cell stack (29) passes through the heat exchanger again and returns to the boiler of the coal-fired power plant for combustion assistance.

[0016] According to some embodiments, the hydrogen storage subsystem includes the gas-water separator (30), the dryer (31), the hydrogen compressor (32) and the hydrogen storage tank (33) in sequence.

[0017] According to some embodiments, the boiler subsystem includes a boiler body (1) and an air preheater (2), and the air preheater (2) is arranged in the tail flue of the boiler body (1); the high-pressure cylinder (3) and the medium-pressure cylinder (4) of the steam turbine subsystem are arranged symmetrically, the low-pressure cylinder (5) is arranged on the other side of the medium-pressure cylinder (4), and is coaxially connected to the generator (6), the outlet of the generator (6) is connected to the step-up transformer (36), the outlet of the low-pressure cylinder (5) is connected to the inlet of the condenser (7), and the condensate pump (8) is arranged at the outlet position of the condenser (7); the steam turbine subsystem uses 8-stage extraction steam to heat feed water in the low-temperature heat recovery subsystem (9) and the high-temperature heat recovery subsystem (12), wherein the first-stage extraction steam pipeline (13) and the second-stage extraction steam pipeline (14) are connected to the high-pressure cylinder (3), and the third-stage extraction steam pipeline (15) and the fourth-stage extraction steam pipeline (16) are connected to the high-pressure cylinder (3). ) is connected to the medium-pressure cylinder (4) and the deaerator (10), the first to third stage extraction steam enters the high-temperature heat recovery subsystem (12) to heat the feed water at the outlet of the feed water pump (11), the fifth stage extraction steam pipeline (17), the sixth stage extraction steam pipeline (18), the seventh stage extraction steam pipeline (19), and the eighth stage extraction steam pipeline (20) are connected to the low-pressure cylinder (5), enter the low-temperature heat recovery subsystem (9) to heat the condensate at the outlet of the condensate pump (8); the fifth stage extraction steam pipeline (17) is provided with a first branch (23) connected to the ejector (25), and the sixth stage extraction steam pipeline (18) is provided with a second branch (24) connected to the ejector (25), and the first valve (21) and the second valve (22) are correspondingly arranged on the first branch (23) and the second branch (24), and the first and second branches are both connected to the high-pressure inlet of the ejector (25).

[0018] The beneficial effect of the above-mentioned embodiment is that under the deep regulation of the coal-fired power plant, the boiler subsystem provides high-temperature air to the SOE hydrogen production system, the steam turbine subsystem provides high-temperature steam to the SOE hydrogen production, and the generator of the steam turbine subsystem outputs electrical energy to supply the electrolytic stack of the SOE hydrogen production system for electrolytic hydrogen production, thereby constructing a specific deep regulation method in which the coal-fired power plant does not shut down and the online power consumption is lower than the technical minimum output of the power plant.

[0019] According to some embodiments, the outlet of the low-pressure cylinder (5) is connected to the inlet of the condenser (7), and the steam enters the condenser (7) to be cooled and condensed into water. The condensed water is recovered, and a portion of it is pressurized by the condensate pump (8) and heated by the low-temperature heat recovery subsystem (9), and then reaches the deaerator (10) for deoxygenation; the other portion of the condensate is passed to the gas-water separator (30), and the gas-water separator (30) is used to cool the hydrogen-containing water vapor after heat exchange in the heat exchanger, and then passes into the deaerator (10) after absorbing heat and heating.

[0020] According to some embodiments, the heat exchanger is selected from a multi-stream heat exchanger (28).

[0021] According to some embodiments, the multi-stream heat exchanger (28) is selected from a plate type or a plate-fin type.

[0022] The beneficial effect of the above-mentioned embodiment is that the SOE hydrogen production system operates the electrolytic stack in the heat release mode and adopts an optimized multi-stream heat exchanger. While realizing the cascade utilization of thermal energy in the SOE hydrogen production system, it eliminates the high-temperature electric heater required by the traditional SOE system. The multi-stream heat exchanger and the SOE electrolytic stack module are designed as an integrated whole to simultaneously minimize the volume and heat dissipation of the SOE hot box.

[0023] On the other hand, the present invention also provides an auxiliary coal-fired power deep adjustment method based on the above-mentioned auxiliary machine-free solid oxide electrolysis hydrogen production system. When the power generation load rate of the coal-fired power station is greater than the critical load ζ, the first valve (21) is closed and the second valve (22) is opened, and six-stage steam extraction is used to supply steam to the auxiliary machine-free solid oxide electrolysis hydrogen production system; when the power generation load rate of the coal-fired power station unit is less than or equal to the critical load ζ, the first valve (21) is opened and the second valve (22) is closed, and five-stage steam extraction is used to supply steam to the auxiliary machine-free solid oxide electrolysis hydrogen production system, so that the supplied steam matches the steam demand of the auxiliary machine-free solid oxide electrolysis hydrogen production system.

[0024] The beneficial effects of the above-mentioned implementation method are as follows: the steam generated by the interaction between the SOE hydrogen production system and the coal-fired power plant is guided by the principle of "grade matching and cascade utilization". By comprehensively comparing the energy utilization efficiency of the coupled system, the steam extraction source is flexibly adjusted to match the steam supply level of the steam turbine subsystem with the SOE demand, thereby reducing the steam extraction throttling loss.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention proposes a solid oxide electrolysis hydrogen production system without auxiliary equipment and an auxiliary coal-fired power deep adjustment method, which is driven by an external heat source and operates in an internal stack heat release mode, greatly reducing the power consumption of the electrolysis hydrogen production system; adopting external material supply, cathode ejector material self-circulation, and multi-stream heat exchange methods, eliminating the complex cold and hot auxiliary equipment of the traditional solid oxide electrolysis hydrogen production system, and having a simple structure and greatly improving the compactness of the system.

[0027] (2) The present invention proposes a solid oxide electrolysis hydrogen production system without auxiliary equipment and an auxiliary coal-fired power deep adjustment method. By sharing the high-reliability pumps and fans of the coal-fired power station and other auxiliary equipment, the high-temperature air at the outlet of the boiler air preheater is used as the anode purge gas and thermal management medium of the electrolysis stack, and the pressurized water vapor extracted from the fifth / sixth stage of the steam turbine is used as the cathode inlet logistics of the electrolysis stack. The electrolysis stack is operated in the heat release mode, and the optimized multi-stream compact heat exchanger is used to realize the heat exchange of the inlet and outlet logistics of the electrolysis stack, thereby eliminating all the cold auxiliary equipment (fans, pumps, water treatment, etc.) and hot auxiliary equipment (steam generators, gas preheaters, exhaust gas cooling, high-temperature electric heating, etc.) of the traditional SOE hydrogen production system, greatly simplifying the SOE hydrogen production system, and realizing the compact integration of the SOE hot box, which is conducive to the simultaneous reduction of the power consumption, investment cost and failure rate of the SOE hydrogen production system.

[0028] (3) The SOE hydrogen production system proposed in the present invention adopts a hydrogen / steam logistics recycling design at the outlet of the SOE hot box, uses the fifth / sixth stage extraction steam of the steam turbine as the driving steam source, and uses an ejector to inject a small amount of hydrogen / steam at the outlet of the SOE hot box into the mixer to form a reducing steam / hydrogen mixture (the hydrogen gas volume fraction is less than 10%) and enter the SOE hot box. Compared with the high-pressure gas cylinder throttling hydrogen premixing scheme or the circulating fan scheme in the conventional SOE hydrogen production system, the total steam conversion rate and the energy conversion efficiency of the entire process of the SOE hydrogen production system are improved.

[0029] (4) The present invention integrates the coal-fired unit and the SOE hydrogen production system into a coupling system. By comparing the efficiency and peak-shaving capacity of the coupling system, the steam extraction position for supplying steam to the SOE system is adjusted under different operating conditions so that the steam extraction parameters match the steam demand characteristics of the SOE hydrogen production system, thereby improving the energy efficiency and economy of the coupling system.

[0030] (5) The present invention provides a deep regulation scheme for coal-fired power plants below the technical minimum output, as well as a deep regulation technical scheme for off-grid operation without shutting down and with zero online power, thereby improving the deep peak regulation flexibility and life of coal-fired power plants and reducing the start-up and shutdown costs of power plants. Compared with the traditional SOE hydrogen production system, the present invention operates the SOE electrolysis stack in a heat release mode, so that the temperature of the high-temperature oxygen-rich air at the outlet of the SOE hot box is higher, which can carry more heat into the furnace, thereby improving the low-load stable combustion effect and reducing the complexity of waste heat utilization on the SOE purge gas side.

[0031] (6) The SOE hydrogen production system in the present invention switches between hydrogen production mode and hot standby mode on a daily basis. It operates in hydrogen production mode during the deep peak-shaving period of the coal-fired power plant and in hot standby mode during the non-peak-shaving period. By quickly switching from hot standby mode to hydrogen production mode, the peak-shaving response speed of the coupled power plant is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of a solid oxide electrolysis hydrogen production system without auxiliary equipment for deep regulation of an auxiliary coal-fired power plant provided in Example 1 of the present invention.

[0033] Figure 2 This is a schematic diagram of another auxiliary machine-free solid oxide electrolysis hydrogen production system for assisting deep regulation of a coal-fired power plant provided in Example 2 of the present invention.

[0034] In the picture:

[0035] 1-Boiler body; 2-Air preheater; 3-High-pressure cylinder; 4-Intermediate-pressure cylinder; 5-Low-pressure cylinder; 6-Generator; 7-Condenser; 8-Condensate pump; 9-Low-temperature regenerative subsystem; 10-Deaerator; 11-Feedwater pump; 12-High-temperature regenerative subsystem; 13-First-stage extraction steam pipeline; 14-Second-stage extraction steam pipeline; 15-Third-stage extraction steam pipeline; 16-Fourth-stage extraction steam pipeline; 17-Five-stage extraction steam pipeline; 18-Sixth-stage extraction steam pipeline; 19-Seventh-stage extraction steam pipeline; 20- Eight-stage steam extraction pipeline; 21-first valve; 22-second valve; 23-first branch; 24-second branch; 25-ejector; 26-throttle valve; 27-electrostatic precipitator; 28-multi-stream heat exchanger; 29-fuel cell stack; 30-gas-water separator; 31-dryer; 32-hydrogen compressor; 33-hydrogen storage tank; 34-SOE hot box system; 35-AC / DC converter; 36-step-up transformer; 37-third valve; 38-third branch. DETAILED DESCRIPTION

[0036] The present invention utilizes existing equipment in coal-fired power plants to supply low-pressure steam extraction from the steam turbine and high-temperature air from the boiler air preheater to the SOE hydrogen production system (SOE usually refers to Solid Oxide Electrolysis). A small amount of hydrogen product is directly injected using pressurized steam extraction to maintain a reducing atmosphere at the SOE cathode. The fuel cell stack operates in an exothermic mode, and the stack outlet logistics enter an optimized multi-stream heat exchanger to heat the air and steam to the stack operating temperature respectively. The power station feed water is used to cool the wet hydrogen, and the steam extraction position is adjusted at multiple levels to achieve full-condition energy efficiency and flexible coordinated regulation of the entire system.

[0037] The present invention is described in detail below with reference to the embodiments and accompanying drawings. However, it should be understood that the embodiments and accompanying drawings are merely exemplary descriptions of the present invention and do not constitute any limitation on the scope of protection of the present invention. All reasonable variations and combinations within the scope of the inventive concept of the present invention fall within the scope of protection of the present invention.

[0038] The present invention will be further described below with reference to the accompanying drawings.

[0039] Example 1

[0040] like Figure 1 As shown, this embodiment 1 provides an auxiliary-free solid oxide electrolysis hydrogen production system, hereinafter referred to as the SOE hydrogen production system. The SOE hydrogen production system includes an SOE hot box system consisting of a fuel cell stack 29 and a high-temperature heat exchanger, a hydrogen circulation subsystem, and a hydrogen storage subsystem. The SOE hydrogen production system can assist in deep regulation of coal-fired power plants.

[0041] In the figure, the SOE hydrogen production system is coupled with a coal-fired power plant. The coal-fired power plant serves as one of the external heat sources and includes a boiler subsystem and a steam turbine subsystem. The pulverized coal in the boiler body 1 of the boiler subsystem is mixed with high-temperature air and burned to heat the feed water, forming high-temperature steam that enters the steam turbine subsystem. The air preheater 2 of the boiler subsystem uses the waste heat of the flue gas to heat the cold air and send it into the boiler body 1 for combustion assistance. Part of the hot air at the outlet of the air preheater 2 is input into the SOE hot box system 34; the high-temperature and high-pressure steam in the steam turbine subsystem expands to generate power, and part of the expanded steam is extracted in stages to heat the condensed water step by step, and part of the electrical energy and a small amount of the expanded steam are input into the SOE hot box system; the fuel cell 29 of the SOE hot box system 34 uses the power generated by the steam turbine subsystem to electrolyze a small amount of steam extracted from the steam turbine subsystem into hydrogen and oxygen, and uses the high-temperature air input from the boiler subsystem to blow Sweep oxygen; the fuel cell stack 29 operates in the exothermic mode, and inputs the outlet logistics into the heat exchanger of the SOE hot box system 34; the heat exchanger adopts a multi-stream heat exchanger 28 to exchange heat between cold and hot fluids, and uses the heat of the outlet logistics of the fuel cell stack 29 to further heat the steam input from the steam turbine subsystem and the high-temperature air input from the boiler subsystem; the hydrogen circulation subsystem uses the extraction steam input from the steam turbine subsystem to the SOE hot box system 34 to inject a small amount of hydrogen / steam mixture at the outlet of the SOE hot box system to form a reducing steam / hydrogen mixture that is input to the SOE hot box system 34 for heating; the hydrogen storage subsystem cools and dries the hydrogen and then compresses it for storage; the SOE hot box system 34 is usually in hydrogen production mode or hot standby mode, and is put into hydrogen production mode when the coal-fired power plant is performing deep peak regulation, and is put into hot standby mode when the coal-fired power plant is not performing peak regulation.

[0042] More specifically, the boiler subsystem includes a boiler body 1 and an air preheater 2, and the steam turbine subsystem includes a high-pressure cylinder 3, an intermediate-pressure cylinder 4, a low-pressure cylinder 5, a generator 6, a condenser 7, a condensate pump 8, a low-temperature heat recovery subsystem 9, a deaerator 10, a feedwater pump 11, a high-temperature heat recovery subsystem 12, a first-stage steam extraction pipeline 13, a second-stage steam extraction pipeline 14, a third-stage steam extraction pipeline 15, a fourth-stage steam extraction pipeline 16, a fifth-stage steam extraction pipeline 17, a sixth-stage steam extraction pipeline 18, a seventh-stage steam extraction pipeline 19, an eighth-stage steam extraction pipeline 20, a first valve 21, a second valve 22, a first branch 23, a second branch 24 and a step-up transformer 36, wherein the first branch 23 is a steam extraction pipeline branch controlled by the first valve 21, and the second branch 24 is a steam extraction pipeline branch controlled by the second valve 22. The steam turbine subsystem usually adopts a "three highs, four lows and one deaeration" configuration, using 8-stage extraction steam to heat the feed water in the low-temperature heat recovery subsystem 9 and the high-temperature heat recovery subsystem 12.

[0043] An air preheater 2 is arranged at the tail flue of the boiler body 1; the high-pressure cylinder 3 and the intermediate-pressure cylinder 4 of the steam turbine are arranged symmetrically, the first-stage extraction pipe 13 and the second-stage extraction pipe 14 are connected to the high-pressure cylinder 3, and the third-stage extraction pipe 15 and the fourth-stage extraction pipe 16 are connected to the intermediate-pressure cylinder 4; the low-pressure cylinder 5 is arranged on the other side of the intermediate-pressure cylinder 4, and is connected to the fifth-stage extraction pipe 17, the sixth-stage extraction pipe 18, the seventh-stage extraction pipe 19, and the eighth-stage extraction pipe 20, and is then coaxially connected to the generator 6. The generator outlet is connected to the AC / DC converter 35 is connected to step-up transformer 36; at the same time, the outlet of low-pressure cylinder 5 is connected to the inlet of condenser 7, and condensate pump 8 is arranged at the outlet of condenser 7, followed by low-temperature heat recovery subsystem 9, deaerator 10, feed water pump 11, and high-temperature heat recovery subsystem 12. The high-temperature heat recovery subsystem 12 is connected to the boiler body 1 for further heating; the first valve 21 and the second valve 22 are respectively arranged on the newly added steam extraction pipeline branches on the fifth and sixth stage steam extraction pipelines, that is, on the first branch 23 and the second branch 24 respectively.

[0044] The operation process of a coal-fired power plant is described as follows:

[0045] Air preheater 2 uses tail flue gas to heat ambient air. Pulverized coal mixes with the air after passing through air preheater 2 and then burns in the combustion chamber of boiler body 1. The heat generated by combustion heats the feedwater in boiler body 1. After undergoing multiple heating stages, the feedwater becomes high-temperature, high-pressure main steam. The main steam expands and performs work in high-pressure cylinder 3, then continues to flow into boiler body 1 to be heated and become reheated steam. The main steam then expands and performs work in intermediate-pressure cylinder 4 and low-pressure cylinder 5, driving the turbine blades to rotate, thereby driving generator 6 to generate electricity. Part of the generated electricity passes through AC / DC converter 35 and is input into the fuel cell stack 29, while part is boosted by step-up transformer 36 and fed into the power grid. After passing through the turbine, the steam enters condenser 7, where it is cooled and condensed into water. The condensed water is recovered, pressurized by the condensate pump 8, and then a part of it is heated by the low-temperature heat recovery subsystem 9, and then reaches the deaerator 10 for deoxygenation. The fifth / sixth / seventh / eighth stage extraction steam is used as the heating heat source of the low-pressure heat recovery subsystem, and the fourth stage extraction steam is used as the heating heat source of the deaerator 13. It is then pressurized by the water supply pump 11 and then heated by the high-temperature heat recovery subsystem 12. The first / secondary / third stage extraction steam is used as the heating heat source of the high-temperature heat recovery subsystem 12, and then enters the boiler body 1 for further heating to form a closed loop; the other part of the condensate is passed to the gas-water separator 30 in the electrolytic hydrogen production system, which is used to cool the hydrogen-containing water vapor after heat exchange in the multi-stream heat exchanger 28, and is passed into the deaerator 10 after absorbing heat and heating. The first valve 21 and the second valve 21 are respectively arranged on the newly added steam extraction pipeline branches on the fifth / sixth stage steam extraction main pipeline of the steam turbine unit, and are used to adjust the steam source from the steam turbine unit to supply the SOE hydrogen production system, so that the steam level supplied by the steam turbine unit matches the required steam level of the SOE hydrogen production system.

[0046] The ambient air is heated by the air preheater 2 to become high-temperature air, and then passes through the electrostatic precipitator 27 and enters the multi-stream heat exchanger 28 to be heated to the operating temperature of the fuel cell stack 29, and then input to the anode of the fuel cell stack 29; the high-temperature water vapor output from the fifth and sixth stage steam extraction pipelines is mixed with a small amount of high-temperature hydrogen and water vapor through the ejector 25, and then reduced to the SOE working pressure through the throttle valve 26, and then enters the multi-stream heat exchanger 28 to be heated to the SOE fuel cell stack working temperature, and then input to the cathode of the SOE fuel cell stack 29.

[0047] The SOE hydrogen production system includes an ejector 25, a throttle valve 26, an electrostatic precipitator 27, a multi-stream heat exchanger 28, a fuel cell stack 29, a gas-water separator 30, a dryer 31, a hydrogen compressor 32, a hydrogen storage tank 33, and an AC / DC converter 35. The multi-stream heat exchanger 28 and the fuel cell stack 29 constitute an SOE hot box system 34. Heat exchange within the system is performed through the multi-stream heat exchanger 28, which can be either a plate or plate-fin type. The outlet stream of the fuel cell stack 29 heats the inlet stream, achieving cascaded utilization of thermal energy and significantly reducing the power consumption of hydrogen production by solid oxide water electrolysis. The ejector 25 is arranged at the cathode inlet logistics of the SOE hydrogen production system, and is connected to the first branch 23 and the second branch 24 of the fifth / sixth stage steam extraction pipeline of the steam turbine upstream, and is connected to the throttle valve 26 downstream; the outlet of the throttle valve 26 is connected to the multi-stream heat exchanger 28, and then connected to the cathode of the fuel cell stack 29, and the cathode outlet of the fuel cell stack 29 is connected to the multi-stream heat exchanger 28. The cathode outlet logistics of the SOE hydrogen production system are split after passing through the multi-stream heat exchanger 28, and are respectively connected to the ejector 25 and the gas-water separator 30, and after the gas-water separator 30, are connected to the dryer 31, the hydrogen compressor 32, and the hydrogen storage tank 33 in sequence; the outlet of the electrostatic precipitator 27 is connected to the multi-stream heat exchanger 28, and then connected to the anode of the fuel cell stack 29, and the anode outlet of the fuel cell stack 29 is connected to the multi-stream heat exchanger 28, and then enters the boiler body 1; the inlet of the AC / DC converter 35 is connected to the coal-fired power plant, and the outlet is connected to the fuel cell stack 29.

[0048] The operation process of the SOE hydrogen production system is described as follows:

[0049] The ambient air is heated by the air preheater 2 to become high-temperature air, and then passes through the electrostatic precipitator 27 and enters the multi-stream heat exchanger 28 to be heated to the operating temperature of the SOE stack, and then input to the anode of the SOE stack 29. The stack 29 operates in the heat release mode. The high-temperature air at the anode outlet of the stack 29 enters the multi-stream heat exchanger 28 for cooling and is then transported to the boiler body 1 to be used as a combustion aid; the high-temperature water vapor output from the fifth or sixth stage steam extraction pipeline of the low-pressure cylinder of the steam turbine unit is mixed with a small amount of SOE hydrogen production unit cathode outlet flow through the ejector 25, replacing the hydrogen premixing process in the conventional SOE electrolysis, reducing components such as the recirculation fan, and further improving the total fuel utilization rate and energy utilization efficiency of the system. After that, the inlet flow containing a small amount of hydrogen is passed through After the throttle valve 26 drops to the SOE working pressure, it enters the multi-stream heat exchanger 28 and is heated to the working temperature of the fuel cell stack 29, and then is input to the cathode of the fuel cell stack 29. The outlet logistics of the fuel cell stack 29 enters the multi-stream heat exchanger 28 and is initially cooled and then diverted. Part of the hydrogen-containing water vapor enters the ejector 25, and most of the logistics enters the gas-water separator 30 to exchange heat with the condensate from the coal-fired power plant. After the heat exchange, the heated condensate is passed into the deaerator 10. The hydrogen obtained through two-stage cooling and separation is dried in turn through the dryer 31, pressurized by the hydrogen compressor 32, and then enters the hydrogen storage tank 33 for storage; the alternating current generated after the coal-fired power plant unit supplies steam is converted into direct current through the AC / DC converter 35 to provide power for the SOE fuel cell stack 29.

[0050] The SOE hydrogen production system uses steam turbine extraction and high-temperature air from the boiler air preheater outlet as electrolytic stack materials through the use of shared coal-fired power plant auxiliary equipment, and places the electrolytic stack in heat release mode. It cancels key cold components (fans, pumps, water treatment, recirculation fans, etc.) and key hot components (steam generators, gas preheaters, tail gas cooling, high-temperature electric heating, etc.) of the traditional SOE hydrogen production system, thereby achieving a significant simplification and reliability improvement of the SOE system. At the same time, through the optimized design of the multi-stream heat exchanger and its integrated design with the electrolytic stack, the compactness of the SOE hot box is further improved, the heat loss of the high-temperature system is reduced, and the investment cost and power consumption of the SOE hydrogen production system are reduced, and the reliability and variable load capacity are improved. Compared with the traditional SOE hydrogen production system, the high-temperature oxygen-rich air at the outlet of the SOE hydrogen production system in the present invention is higher in temperature, carries more heat, and has a better effect on low-load stable combustion after being introduced into the boiler furnace. The SOE hydrogen production system switches between hydrogen production mode and hot standby mode on a daily basis. It operates in hydrogen production mode during the deep peak-shaving period of the coal-fired power plant and in hot standby mode during the non-peak-shaving period. By quickly switching from hot standby mode to hydrogen production mode, the peak-shaving response speed of the coupled power plant is improved.

[0051] The control method of the auxiliary-free solid oxide electrolysis hydrogen production system provided in this embodiment specifically compares the overall efficiency and peak-shaving capacity of the coupled system, selects different steam extraction ports according to the power generation load rate of the coal-fired power plant to provide high-temperature steam for the SOE hydrogen production system, and achieves flexible time-sharing steam extraction and improves the energy utilization efficiency of the system.

[0052] By comparing the differences in the combined energy efficiency of the coupled system under different operating conditions and steam extraction conditions, a flexible time-sharing steam extraction strategy for the steam turbine subsystem is determined, resulting in an optimized steam extraction control scheme for the system. This can be achieved by opening the first valve 21 and second valve 22 of the steam turbine unit in different time periods. When the power generation load rate of the coal-fired power plant exceeds the critical load ζ, the first valve 21 is closed, the second valve 22 is opened, and six-stage steam extraction is used to supply steam to the SOE hydrogen production system. When the power generation load rate of the coal-fired power plant is less than or equal to the critical load ζ, the first valve 21 is opened, the second valve 22 is closed, and five-stage steam extraction is used to supply steam to the SOE hydrogen production system. This ensures that the supplied steam parameters consistently match the steam characteristics of the SOE demand, thereby improving the energy efficiency and operational economy of the coupled system.

[0053] By coupling coal-fired power plants with SOE hydrogen production systems, the deep peak-shaving capability of coal-fired power plants can be enhanced, providing off-grid deep regulation technical solutions where the coal-fired power plants can operate below the technical minimum output, or even without shutting down and with zero online power. This reduces the number of unit starts and stops, and improves the peak-shaving depth and operational flexibility of coal-fired power plants.

[0054] Example 2

[0055] like Figure 2 As shown, this embodiment provides another auxiliary-free solid oxide electrolysis hydrogen production system, which assists coal-fired power plants in deep regulation. As can be seen in the figure, the difference from Example 1 lies in the placement of a third valve 37 on a newly added steam extraction branch line, namely, third branch line 28, on the fourth-stage steam extraction line 16. In this embodiment, high-temperature steam output from the fourth-stage steam extraction line 16 of the turbine unit's low-pressure cylinder is mixed with a small amount of cathode outlet stream from the SOE hydrogen production system via an ejector 25, replacing the hydrogen premixing process used in conventional SOE electrolysis.

[0056] This embodiment provides an auxiliary coal-fired power deep regulation method for a non-auxiliary solid oxide electrolysis hydrogen production system. Specifically, based on the actual coal-fired power plant project, a four-stage steam extraction port is selected to provide high-temperature steam for the SOE hydrogen production system. The four-stage steam extraction pipeline is already used in the power plant's existing thermal system (deaerator). Reusing the existing pipeline can reduce additional investment. This embodiment 2 can serve as an alternative to embodiment 1.

[0057] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of protection of the present invention are within the scope of protection of the present invention. It should be noted that improvements and modifications that can be made by a person skilled in the art without departing from the principles of the present invention are also considered to be within the scope of protection of the present invention.

Claims

1. A system for producing hydrogen by solid oxide electrolysis without auxiliary equipment, characterized in that: The invention comprises a SOE hot box system for electrolytic hydrogen production, a hydrogen circulation subsystem and a hydrogen storage subsystem, which are respectively coupled with a coal-fired power plant; the coal-fired power plant comprises a boiler subsystem and a steam turbine subsystem, and the SOE hot box system comprises a heat exchanger and a stack (29); the coupling comprises cathode reactant supply, anode reactant supply, power supply, anode product utilization and cathode waste heat utilization: The cathode reactant is supplied by extracting at least one steam from the steam turbine subsystem to the high-pressure inlet of the ejector (25), and then ejecting part of the product produced by the SOE hot box system to the low-pressure suction port of the ejector (25) through the hydrogen circulation subsystem. A mixed gas of reducing steam and hydrogen is formed through the ejector (25), and then enters the cathode inlet of the fuel cell stack (29) after passing through the mixed outlet of the ejector (25), the throttle valve (26) and the heat exchanger. The hydrogen produced by the fuel cell stack (29) is output from the cathode outlet and passes through the heat exchanger again. Part of the hydrogen is input to the low-pressure inlet of the ejector (25), and the other part is input to the hydrogen storage subsystem. The anode reactant is supplied by removing dust from the high-temperature air of the boiler subsystem and then entering the heat exchanger and the anode inlet of the stack (29) in sequence; The power supply is to input part of the electric energy generated by the steam turbine subsystem into the SOE hot box system; The anode product is utilized by returning the high-temperature air output from the anode outlet of the stack (29) through the heat exchanger again to the boiler of the coal-fired power station for combustion support; The cathode waste heat utilization is to utilize the heat released by the cathode product in the gas-water separator (30) of the hydrogen storage subsystem to heat a stream of condensate from the condensate pump of the steam turbine subsystem, and the condensate is preheated and then returned to the deaerator (10); The heat exchanger is selected from a multi-stream heat exchanger (28).

2. The auxiliary-free solid oxide electrolysis hydrogen production system according to claim 1, characterized in that: The hydrogen storage subsystem comprises the gas-water separator (30), the dryer (31), the hydrogen compressor (32) and the hydrogen storage tank (33) in sequence.

3. The auxiliary-free solid oxide electrolysis hydrogen production system according to claim 1, characterized in that: The boiler subsystem includes a boiler body (1) and an air preheater (2), and the air preheater (2) is arranged in the tail flue of the boiler body (1); the high-pressure cylinder (3) and the medium-pressure cylinder (4) of the steam turbine subsystem are arranged symmetrically, the low-pressure cylinder (5) is arranged on the other side of the medium-pressure cylinder (4), and is coaxially connected to the generator (6), the outlet of the generator (6) is connected to the step-up transformer (36), the outlet of the low-pressure cylinder (5) is connected to the inlet of the condenser (7), and the condensate pump (8) is arranged at the outlet position of the condenser (7); the steam turbine subsystem uses 8-stage extraction steam to heat feed water in the low-temperature heat recovery subsystem (9) and the high-temperature heat recovery subsystem (12), wherein the first-stage extraction steam pipeline (13) and the second-stage extraction steam pipeline (14) are connected to the high-pressure cylinder (3), and the third-stage extraction steam pipeline (15) and the fourth-stage extraction steam pipeline (16) are connected to the medium-pressure cylinder (4) and the deaerator. The first to third stage extraction steam enters the high-temperature heat recovery subsystem (12) to heat the outlet feed water of the feed water pump (11); the fifth stage extraction steam pipeline (17), the sixth stage extraction steam pipeline (18), the seventh stage extraction steam pipeline (19), and the eighth stage extraction steam pipeline (20) are connected to the low-pressure cylinder (5) and enter the low-temperature heat recovery subsystem (9) to heat the outlet condensate of the condensate pump (8); the fifth stage extraction steam pipeline (17) is provided with a first branch (23) connected to the ejector (25); the sixth stage extraction steam pipeline (18) is provided with a second branch (24) connected to the ejector (25); the first valve (21) and the second valve (22) are correspondingly arranged on the first branch (23) and the second branch (24); the first branch (23) and the second branch (24) are both connected to the high-pressure inlet of the ejector (25).

4. The auxiliary-free solid oxide electrolysis hydrogen production system according to claim 3, characterized in that: The outlet of the low-pressure cylinder (5) is connected to the inlet of the condenser (7). The steam enters the condenser (7) to be cooled and condensed into water. The condensed water is recovered and pressurized by the condensate pump (8). A portion of the water passes through the low-temperature heat recovery subsystem (9) for heating and then reaches the deaerator (10) for deoxidation. The other portion of the condensed water flows to the gas-water separator (30). The gas-water separator (30) is used to cool the hydrogen-containing water vapor after heat exchange in the heat exchanger, and then flows into the deaerator (10) after absorbing heat and heating.

5. The auxiliary-free solid oxide electrolysis hydrogen production system according to claim 4, characterized in that: The multi-stream heat exchanger (28) is selected from a plate type or a plate-fin type.

6. An auxiliary coal-fired power deep regulation method for a solid oxide electrolysis hydrogen production system without auxiliary equipment according to any one of claims 3 to 5, characterized in that: When the power generation load rate of the coal-fired power station is greater than the critical load ζ, the first valve (21) is closed and the second valve (22) is opened, and six-stage steam extraction is used to supply steam to the auxiliary-free solid oxide electrolysis hydrogen production system; when the power generation load rate of the coal-fired power station unit is less than or equal to the critical load ζ, the first valve (21) is opened and the second valve (22) is closed, and five-stage steam extraction is used to supply steam to the auxiliary-free solid oxide electrolysis hydrogen production system, so that the supplied steam matches the steam demand of the auxiliary-free solid oxide electrolysis hydrogen production system.

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