Auxiliary-machine-free solid oxide electrolytic hydrogen production system and auxiliary coal electricity deep adjustment method

Abstract

The invention relates to the technical field of hydrogen energy, and discloses an auxiliary-machine-free solid oxide electrolytic hydrogen production system and an auxiliary coal electricity deep adjustment method, the hydrogen production system comprises an SOE heat box system for electrolytic hydrogen production, a hydrogen circulation subsystem and a hydrogen storage subsystem; the ejector is driven by external heat source steam, part of hydrogen at an outlet of the SOE heat box system is ejected to a low-pressure suction inlet of the ejector through the hydrogen circulation subsystem, and formed reducing mixed gas of steam and hydrogen enters a cathode inlet of the SOE heat box system. The system is driven by an external heat source and operates in an internal stack heating mode, so that the power consumption of the electrolytic hydrogen production system is reduced; by adopting the modes of external material supply, cathode ejector material self-circulation and multi-stream heat exchange, a complex cold and hot auxiliary machine of a traditional solid oxide electrolytic hydrogen production system is omitted, the structure is simple, and the system compactness is greatly improved; electric power-steam-air-condensed water flow coupling is established with a coal-fired power plant, and efficient, flexible and deep peak shaving is adjusted in combination with steam extraction multi-stage adjustment.

Description

Technical Field

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

[0002] The maximum peak shaving capacity of a conventional coal-fired power station is limited by the minimum technical output (about 30% of the rated load). With the continuous increase in the installed capacity ratio of new energy sources such as wind and solar, in order to ensure the stable and safe operation of the power grid, it is urgent to develop ultra-low load deep peak shaving technology for thermal power, and further explore the peak shaving depth limit and operation mode of the unit.

[0003] Ultra-low load deep peak shaving of coal-fired power stations faces many challenges. For example, the combustion stability of the boiler is poor during low-load operation, and it is easy to have incomplete combustion or even flameout, which limits the minimum technical output of the power station. And the use of oil for stable combustion will reduce the peak shaving economy of the power station. The method of configuring electricity storage has high investment, and the single electric energy interaction cannot improve the peak shaving ability of the power station itself; the method of configuring heat storage for simple thermal electrolysis decoupling can improve the low-load heat supply ability of the unit, but it is difficult to improve the electric peak shaving ability; the method of deeply coupling heat storage with the power station requires the transformation of the power station's thermal system, which affects the reliability of the power station and has a large investment demand; in order to further increase the peak shaving depth, some units use start-stop peak shaving, but there are disadvantages such as long start-stop time, insufficient flexibility, and poor economy. Therefore, it is urgent to develop new and efficient flexible coal-fired power deep peak shaving technologies.

[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 mode of the coordination of a coal-fired power station and electrolysis energy storage was proposed. For the first time, the peak shaving flexibility of coal-fired units was improved by combining the SOE hydrogen production system with the coal-fired power station. However, it failed to give a flexible coupling scheme and control method for extracting steam in a time-sharing and segmented manner according to the principle of "matching grades and cascaded utilization", and the SOE system adopted was borrowed from an independent SOE system, resulting in complex equipment, high investment cost, and limited application economy.

[0005] The existing Chinese patent with the publication number CN212642819U discloses a flexible peak shaving system for coupling high-temperature solid oxide electrolysis of water with a power plant. By equipping an independent SOE hydrogen production system as an additional auxiliary power load of the plant, the flexible peak shaving capacity of the thermal power unit can be improved. However, in this system, there is only an electrical connection between the power station and the SOE system, and the advantage of improving the low-load operation capacity of the power station by coupling the energy and mass conversion processes of the two cannot be exerted. In addition, components such as electric heaters are used to raise the temperature of the inlet material of the SOE, which greatly reduces the power utilization efficiency. Moreover, the independent SOE system itself is complex, with a large number of cold and heat auxiliary machines and start-up units, resulting in high investment costs and limited reliability.

[0006] The existing Chinese patent with the publication number CN116247727A discloses a power generation system coupling a coal-fired unit and an SOEC and its operation method. The system includes a coal-fired power generation system and an SOE peak shaving and frequency modulation system. This invention adopts the method of ejecting the extraction steam of the coal-fired power generation system and electrolyzing the ejected extraction steam. According to the requirements of the power grid, the current density of the SOE peak shaving and frequency modulation system is controlled, and then the coal-fired power generation system is peak shaved and frequency modulated. The oxygen generated by electrolyzing water vapor is used to assist the stable combustion of the boiler under low-load conditions, improving the variable load capacity of the unit under the low-load operation mode. However, in this invention, hydrogen, which is necessary to maintain a reducing atmosphere, is not introduced into the cathode side of the electrolyzer stack, and the electrolyzer stack itself lacks an effective cooling medium for thermal management. An electric heater is used for material heating, which limits the electrode stability, operating current density of the stack, and the SOE hydrogen production efficiency, and cannot solve the problem of high investment in SOE equipment, resulting in limited application potential.

[0007] The existing Chinese patent with the publication number CN117090647A discloses a coal-fired power generation system coupling an SOEC and a method for deep peak shaving operation of the unit. The system includes a thermal system of a coal-fired power generation unit, a solid oxide electrolytic cell, and a molten salt heat storage coupling system. This invention increases the working medium flow rate of the high- and medium-pressure cylinders during low-load operation of the power station by adopting regenerative extraction steam throttling, improving the cylinder efficiency of the steam turbine; by coupling the molten salt heat storage and the SOE system, the low-load combustion stability of the boiler is improved, and the flexibility of the deep peak shaving process of the coal-fired power generation unit is improved to a certain extent. However, in this technical solution, the temperature of the molten salt heat storage is limited, which is 150 - 200 °C lower than the operating temperature of the electrolyzer stack, making it difficult to meet the requirements of the inlet material temperature for the efficient and safe operation of the electrolyzer stack; the extraction steam of the high- and medium-pressure cylinders does not match the temperature and pressure requirements of the SOE steam; the SOE system follows the configuration of an independent SOE system, and cold auxiliary machines such as pumps and fans cannot be eliminated, the heat exchange load of the heat exchanger is large, and at the same time, the molten rock heat storage and the SOE system are integrated, the energy storage system is complex, the investment cost is high, the implementation difficulty is large, and the economy and application potential are limited. Summary of the Invention

[0008] To overcome or alleviate one or more of the above technical problems, the object of the present invention is to provide a main - auxiliary - free solid oxide electrolysis hydrogen production system and an auxiliary coal - fired power generation deep - regulation method. By using the existing equipment of a coal - fired power station, the low - pressure extraction steam of the steam turbine and the high - temperature air of the boiler air preheater are supplied to the SOE hydrogen production system. A small amount of hydrogen product is directly entrained by the extraction steam to maintain the reducing atmosphere at the cathode of the SOE, thus eliminating all low - temperature auxiliary machines such as fans, water pumps, steam generators, and hydrogen circulation pumps that are indispensable in the existing independent SOE system, greatly saving the operating equipment cost; the electrolytic stack operates in an exothermic mode, and the outlet stream of the stack enters the heat exchanger to heat air and steam to the operating temperature of the stack respectively, thus eliminating high - temperature components such as high - temperature electric heaters that are prone to failure; part of the unreacted steam is directly entrained by the extraction steam, thereby improving the steam conversion rate of the SOE system and reducing the total extraction steam consumption; on the basis that the heat transfer load is less than that of the independent SOE system, a more compact multi - stream plate heat exchanger with optimized design is used to further improve the heat transfer efficiency, reduce heat dissipation loss, reduce the heat exchanger area and increase the outlet temperature of the oxygen - rich air; the excess heat at the hydrogen / steam outlet is used to heat the feed water of the power station, and through multi - level adjustment of the extraction position, the full - working - condition energy efficiency and flexible coordinated control of the ejector and the whole system are realized.

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

[0010] A main - auxiliary - free solid oxide electrolysis hydrogen production system, characterized in that it includes an SOE thermal box subsystem for electrolytic hydrogen production, 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 thermal box subsystem is entrained by the hydrogen circulation subsystem to the low - pressure suction inlet of the ejector (25). A reducing mixture of steam and hydrogen is formed by the ejector (25) and enters the cathode inlet of the SOE thermal box subsystem after passing through the mixing outlet of the ejector (25). The remaining hydrogen produced by the SOE thermal box subsystem is stored through the hydrogen storage subsystem; the SOE thermal box subsystem includes a heat exchanger and an electrolytic stack (29), the electrolytic stack (29) operates in an exothermic mode, and the outlet streams of the electrolytic stack (29) are all input back to the heat exchanger to heat air and steam to the operating temperature of the electrolytic stack (29) respectively.

[0011] The above-described embodiments achieve a significant simplification, high compactness, and reliability improvement of the SOE hydrogen production system by eliminating easily malfunctioning cold and hot auxiliary machines, using pressurized steam to eject hydrogen / unreacted steam, using existing high-temperature air to reduce the heat exchange load, and optimizing multi-stream heat exchange, which is conducive to significantly reducing the investment in the SOE hydrogen production system. The external heat source can be, in addition to a coal-fired power station, traditional fuel heat sources such as coal-fired boilers, new energy heat sources such as concentrating solar power plants and geothermal energy, industrial waste heat sources such as metallurgical ironmaking, nuclear energy heat sources such as nuclear power plants, and other heat sources such as urban waste heat.

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

[0013] The beneficial effects of the above-described embodiments are as follows: By coupling the SOE hydrogen production system with a coal-fired power station, when the power station is deeply peak-shaving, while using SOE hydrogen production as the auxiliary power load of the plant to consume excess coal power, the high-temperature oxygen-rich hot air at the outlet of the SOE system is mixed into the secondary air of the boiler, increasing the heat of the air entering the furnace at low load of the boiler and the stable combustion performance. Without almost any modification to the power station itself, the technical minimum output of the power station is reduced. Further, through the optimization and coordinated operation of the ratio of the coal-fired power station and the SOE system, the peak-shaving capacity and speed of the coal-fired power station are synchronously improved, and an ultra-deep peak-shaving mode lower than the minimum technical output of the coal-fired power station is achieved, providing a new technical solution for the coal-fired power station to participate in the deep peak-shaving of a new power system with a high proportion of renewable energy.

[0014] According to some embodiments, the mixed gas at the mixing outlet of the ejector (25) enters the cathode inlet of the fuel cell stack (29) after passing through the throttle valve (26) and the heat exchanger. After the hydrogen gas produced by the fuel cell stack (29) is output from the cathode outlet, it passes through the heat exchanger again, and part of the hydrogen gas 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 led 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. The high-temperature air output from the anode outlet of the fuel cell stack (29) passes through the heat exchanger again and then returns to the boiler of the coal-fired power station for combustion support.

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

[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 intermediate-pressure cylinder (4) of the steam turbine subsystem are symmetrically arranged, the low-pressure cylinder (5) is arranged on the other side of the intermediate-pressure cylinder (4), and is coaxial with the generator (6). The outlet of the generator (6) is connected to the step-up transformer (36), and the outlet of the low-pressure cylinder (5) is connected to the inlet of the condenser (7). 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 the feed water in the low-temperature regenerative subsystem (9) and the high-temperature regenerative subsystem (12). Among them, the first-stage extraction steam pipeline (13) and the second-stage extraction steam pipeline (14) are connected to the high-pressure cylinder (3), the third-stage extraction steam pipeline (15) and the fourth-stage extraction steam pipeline (16) are connected to the intermediate-pressure cylinder (4) and the deaerator (10). The first to third-stage extraction steam enters the high-temperature regenerative 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) and enter the low-temperature regenerative subsystem (9) to heat the condensate at the outlet of the condensate pump (8); a first branch (23) connecting the ejector (25) is provided on the fifth-stage extraction steam pipeline (17), and a second branch (24) connecting the ejector (25) is provided on the sixth-stage extraction steam pipeline (18). The first valve (21) and the second valve (22) are correspondingly arranged on the first branch (23) and the second branch (24), and both the first and second branches are connected to the high-pressure inlet of the ejector (25).

[0018] The beneficial effects of the above embodiments are that under the deep regulation condition of a coal-fired power station, 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 electric energy to supply the electrolytic stack of the SOE hydrogen production system for electrolytic hydrogen production, thereby constructing a specific deep regulation method for the coal-fired power station without shutting down and with the on-grid power lower than the technical minimum output of the power station.

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

[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 plate type or plate-fin type.

[0022] The beneficial effects of the above embodiments are that the SOE hydrogen production system operates the electrolytic stack in a heat release mode, adopts an optimally designed multi-stream heat exchanger, realizes the cascade utilization of thermal energy in the SOE hydrogen production system while canceling the high-temperature electric heater necessary for the traditional SOE system; the multi-stream heat exchanger is integrally designed with the SOE electrolytic stack module, synchronously realizing the minimization of the volume and heat dissipation of the SOE hot box.

[0023] On the other hand, the present invention also provides an auxiliary coal power deep regulation method according to the above auxiliary-free solid oxide electrolytic 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 the sixth-stage extraction steam is used to supply steam to the auxiliary-free solid oxide electrolytic 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 the fifth-stage extraction steam is used to supply steam to the auxiliary-free solid oxide electrolytic hydrogen production system, so that the supplied steam matches the steam demand of the auxiliary-free solid oxide electrolytic hydrogen production system.

[0024] The beneficial effects of the above embodiments are as follows: The steam interacting between the SOE hydrogen production system and the coal-fired power station is guided by the principle of "grade matching and cascade utilization", and the extraction steam source is flexibly adjusted by comprehensively comparing the energy utilization efficiency of the coupled system, so that the steam supply level of the steam turbine subsystem matches the SOE demand, reducing the extraction steam throttling loss.

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

[0026] (1) An auxiliary-free solid oxide electrolysis hydrogen production system and an auxiliary coal power deep regulation method proposed by the present invention operate in an external heat source-driven and internal stack heat release mode, significantly reducing the power consumption of the electrolysis hydrogen production system; by using external supply of materials, self-circulation of materials by the cathode ejector, and multi-stream heat exchange method, the complex cold and heat auxiliary machines of the traditional solid oxide electrolysis hydrogen production system are cancelled, with a simple structure and a significant improvement in the system compactness.

[0027] (2) An auxiliary-free solid oxide electrolysis hydrogen production system and an auxiliary coal power deep regulation method proposed by the present invention share high-reliability auxiliary equipment such as pumps and fans in a coal-fired power station, use high-temperature air at the outlet of the boiler air preheater as the anode purge gas and heat management medium of the electrolysis stack, and extraction steam with pressure from the fifth / sixth stage of the steam turbine as the cathode inlet material flow of the electrolysis stack, place the electrolysis stack in a heat release mode of operation, and use an optimized multi-stream compact heat exchanger to realize the heat exchange of the material flow at the inlet and outlet of the electrolysis stack, thereby cancelling all cold auxiliary machines (fans, pumps, water treatment, etc.) and heat auxiliary machines (steam generators, gas preheaters, tail gas cooling, high-temperature electric heating, etc.) of the traditional SOE hydrogen production system, greatly simplifying the SOE hydrogen production system, and enabling the compact integration of the SOE hot box, which is beneficial to simultaneously reducing the power consumption, investment cost and failure rate of the SOE hydrogen production system.

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

[0029] (4) The present invention integrates a coal-fired unit and an SOE hydrogen production system into a coupled system. By comparing the efficiency and peak shaving capacity of the coupled system, the extraction steam position for supplying steam to the SOE system is adjusted under different working conditions to make the extraction steam parameters match the steam demand characteristics of the SOE hydrogen production system, thereby improving the energy efficiency and economy of the coupled 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 de-networking deep regulation technology scheme that does not shut down the unit and has a power grid connection of 0, improving the deep peak shaving flexibility and lifespan of coal-fired power plants and reducing the start-up and shutdown costs of the power plants; compared with the traditional SOE hydrogen production system, the present invention operates the SOE electrolyzer stack in a heat release mode, making the temperature of the high-temperature oxygen-rich air at the outlet of the SOE hot box higher, which can carry more heat into the furnace, improving the stable combustion effect at low loads and reducing the complexity of waste heat utilization on the purge gas side of the SOE.

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

[0032] Figure 1 is a schematic diagram of the auxiliary coal-fired power plant deep regulation non-fan solid oxide electrolysis hydrogen production system provided in Embodiment 1 of the present invention.

[0033] Figure 2 is a schematic diagram of another auxiliary coal-fired power plant deep regulation non-fan solid oxide electrolysis hydrogen production system provided in Embodiment 2 of the present invention.

[0034] In the figure:

[0035] 1 - Boiler body; 2 - Air preheater; 3 - High-pressure cylinder; 4 - Medium-pressure cylinder; 5 - Low-pressure cylinder; 6 - Generator; 7 - Condenser; 8 - Condensate pump; 9 - Low-temperature regenerative subsystem; 10 - Deaerator; 11 - Feed water pump; 12 - High-temperature regenerative subsystem; 13 - First extraction steam pipeline; 14 - Second extraction steam pipeline; 15 - Third extraction steam pipeline; 16 - Fourth extraction steam pipeline; 17 - Fifth extraction steam pipeline; 18 - Sixth extraction steam pipeline; 19 - Seventh extraction steam pipeline; 20 - Eighth extraction steam 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 - Stack; 30 - Gas-water separator; 31 - Dryer; 32 - Hydrogen compressor; 33 - Hydrogen storage tank; 34 - SOE hot box subsystem; 35 - AC / DC converter; 36 - Step-up transformer; 37 - Third valve; 38 - Third branch. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The present invention utilizes the existing equipment of a coal-fired power station to supply the low-pressure extraction steam of the steam turbine and the high-temperature air of the boiler air preheater to the SOE hydrogen production system (SOE generally refers to Solid Oxide Electrolysis). A small amount of hydrogen product is directly entrained by the pressurized extraction steam to maintain a reducing atmosphere at the cathode of the SOE. The stack operates in a heat-releasing mode. The stack outlet stream enters a multi-stream heat exchanger with an optimized design to heat the air and steam to the stack operating temperature respectively. The wet hydrogen is cooled by the power station feed water, and through multi-stage adjustment of the extraction steam position, the full-condition energy efficiency and flexible coordinated control of the entire system are achieved.

[0037] The present invention will be described in detail below in conjunction with embodiments and drawings. However, it should be understood that the embodiments and drawings are only used for exemplary description of the present invention and do not constitute any limitation to the protection scope of the present invention. All reasonable transformations and combinations within the scope of the inventive concept of the present invention fall within the protection scope of the present invention.

[0038] The present invention will be further described below in conjunction with the drawings.

[0039] Embodiment 1

[0040] As Figure 1 shown, Embodiment 1 of the present invention provides a non-booster solid oxide electrolysis hydrogen production system, hereinafter simply referred to as the SOE hydrogen production system. The SOE hydrogen production system includes an SOE hot box subsystem composed of a stack 29 and high-temperature heat exchanger and other units, a hydrogen circulation subsystem, and a hydrogen storage subsystem. The SOE hydrogen production system can assist the coal-fired power station in deep regulation.

[0041] In the figure, the SOE hydrogen production system is coupled with a coal-fired power plant. The coal-fired power plant, as one of the external heat sources, 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 for combustion to heat the feed water, forming high-temperature steam that enters the steam turbine subsystem. The air preheater 2 in 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 support, and part of the hot air at the outlet of the air preheater 2 is input into the SOE hot box subsystem 34; in the steam turbine subsystem, the high-temperature and high-pressure steam expands to do work and generate electricity, and part of the expanded steam is extracted in stages to heat the condensate water step by step, and part of the electric energy and a small part of the expanded steam are input into the SOE hot box subsystem; the stack 29 in the SOE hot box subsystem 34 uses the electric energy generated by the steam turbine subsystem to electrolyze a small amount of the extracted steam from the steam turbine subsystem into hydrogen and oxygen, and uses the high-temperature air input from the boiler subsystem to purge the oxygen; the stack 29 operates in the exothermic mode, and the outlet stream is input into the heat exchanger in the SOE hot box subsystem 34; the heat exchanger uses a multi-stream heat exchanger 28 for heat exchange between the cold and hot fluids, and uses the heat of the outlet stream of the stack 29 to further increase the temperature of the steam input from the steam turbine subsystem and the high-temperature air input from the boiler subsystem; the hydrogen circulation subsystem uses the extracted steam input from the steam turbine subsystem into the SOE hot box subsystem 34 to eject a small amount of the hydrogen / steam mixture at the outlet of the SOE hot box subsystem, forming a reducing steam / hydrogen mixture that is input into the SOE hot box subsystem 34 for temperature increase; the hydrogen storage subsystem cools, dries, and compresses the hydrogen for storage; the SOE hot box subsystem 34 is usually in the hydrogen production mode or the hot standby mode, and is put into use in the hydrogen production mode during deep peak shaving of the coal-fired power plant, and is put into the hot standby mode when the coal-fired power plant does not perform peak shaving.

[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, a medium-pressure cylinder 4, a low-pressure cylinder 5, a generator 6, a condenser 7, a condensate pump 8, a low-temperature regenerative subsystem 9, a deaerator 10, a feed water pump 11, a high-temperature regenerative subsystem 12, a first extraction steam pipeline 13, a second extraction steam pipeline 14, a third extraction steam pipeline 15, a fourth extraction steam pipeline 16, a fifth extraction steam pipeline 17, a sixth extraction steam pipeline 18, a seventh extraction steam pipeline 19, an eighth extraction steam pipeline 20, a first valve 21, a second valve 22, a first branch 23, a second branch 24, and a step-up transformer 36, where the first branch 23 is a branch of the extraction steam pipeline controlled by the first valve 21, and the second branch 24 is a branch of the extraction steam pipeline controlled by the second valve 22. The steam turbine subsystem usually adopts a "three-high, four-low, and one-deaerator" configuration, and uses 8-stage extraction steam to heat the feed water in the low-temperature regenerative subsystem 9 and the high-temperature regenerative 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 steam extraction pipeline 13 and the second-stage steam extraction pipeline 14 are connected to the high-pressure cylinder 3, and the third-stage steam extraction pipeline 15 and the fourth-stage steam extraction pipeline 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 steam extraction pipeline 17, the sixth-stage steam extraction pipeline 18, the seventh-stage steam extraction pipeline 19, and the eighth-stage steam extraction pipeline 20, and is then coaxially connected to the generator 6, and the generator outlet is respectively 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, high-temperature heat recovery subsystem 12, which is connected to 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, namely, 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] The air preheater 2 uses the tail flue gas to heat the ambient air. After the coal powder is mixed with the air that has passed through the air preheater 2, it is burned in the combustion chamber of the boiler body 1. The heat generated by the combustion heats the feed water in the boiler body 1. After multi-stage heating, the feed water becomes high-temperature and high-pressure main steam. After the main steam expands and works in the high-pressure cylinder 3, it continues to enter the boiler body 1 to be heated and become reheated steam. After that, it expands and works in the medium-pressure cylinder 4 and the low-pressure cylinder 5 in turn, pushing the blades of the steam turbine to rotate, thereby driving the generator 6 to generate electricity. Part of the generated electricity is input into the stack 29 after passing through the AC / DC converter 35, and part of it is boosted by the step-up transformer 36 and then connected to the power grid. After passing through the steam turbine, the steam enters the condenser 7 to cool and condense into water. The condensed water is recovered, and a part 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, wherein 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, and then pressurized by the feed water pump 11 and heated by the high-temperature heat recovery subsystem 12, and 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, forming a closed loop; another 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 branch 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 supply level of 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 enters the multi-stream heat exchanger 28 after passing through the electrostatic precipitator 27 and is heated to the operating temperature of the stack 29, and then is input to the anode of the stack 29; the high-temperature steam output from the fifth-stage and sixth-stage extraction steam pipelines is mixed with a small amount of high-temperature hydrogen and steam through the ejector 25, and then is reduced to the SOE operating pressure through the throttle valve 26, and then enters the multi-stream heat exchanger 28 and is heated to the SOE stack operating temperature, and then is input to the cathode of the SOE 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 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. Among them, the multi-stream heat exchanger 28 and the stack 29 constitute the SOE thermal box subsystem 34. Among them, internal heat exchange in the system is carried out through the multi-stream heat exchanger 28. The form of the multi-stream heat exchanger 28 can be selected from plate type or plate-fin type. The outlet streams of the stack 29 heat their inlet streams respectively to achieve cascaded utilization of thermal energy and significantly reduce the power consumption of solid oxide electrolytic water hydrogen production. The ejector 25 is arranged at the cathode inlet stream of the SOE hydrogen production system, connected to the first branch 23 and the second branch 24 of the fifth-stage / sixth-stage extraction steam pipeline of the steam turbine upstream, and 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 stack 29. The cathode outlet of the stack 29 is connected to the multi-stream heat exchanger 28. The cathode outlet stream of the SOE hydrogen production system is branched after passing through the multi-stream heat exchanger 28 and is respectively connected to the ejector 25 and the gas-water separator 30, and is successively connected to the dryer 31, the hydrogen compressor 32 and the hydrogen storage tank 33 after the gas-water separator 30; the outlet of the electrostatic precipitator 27 is connected to the multi-stream heat exchanger 28, and then connected to the anode of the stack 29. The anode outlet of the 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 station, and the outlet is connected to the 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, then enters the multi-stream heat exchanger 28 after passing through the electrostatic precipitator 27 and is heated to the operating temperature of the SOE stack. After that, it is input to the anode of the SOE stack 29. The stack 29 operates in the exothermic mode. The high-temperature air at the anode outlet of the stack 29 enters the multi-stream heat exchanger 28 to be cooled and then is transported to the boiler body 1 to be used as a combustion aid. The high-temperature steam output from the fifth or sixth extraction pipeline of the low-pressure cylinder of the steam turbine unit is mixed with a small amount of the cathode outlet stream of the SOE hydrogen production unit 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 overall fuel utilization rate and energy utilization efficiency of the system. After that, the inlet stream containing a small amount of hydrogen is reduced to the SOE operating pressure through the throttle valve 26, enters the multi-stream heat exchanger 28 to be heated to the operating temperature of the stack 29, and then is input to the cathode of the stack 29. The outlet stream of the stack 29 enters the multi-stream heat exchanger 28 to be preliminarily cooled and then is split. Part of the hydrogen-containing steam enters the ejector 25, and most of the stream enters the gas-water separator 30 to exchange heat with the condensate from the coal-fired power station. After heat exchange, the heated condensate is fed into the deaerator 10. The hydrogen obtained through two-stage cooling and separation is dried through the dryer 31 in sequence, pressurized through the hydrogen compressor 32, and then enters the hydrogen storage tank 33 for storage. The alternating current generated after the coal-fired power station unit supplies steam is converted into direct current through the AC / DC converter 35 to provide electrical energy for the SOE stack 29.

[0050] The SOE hydrogen production system shares the auxiliary equipment of the coal-fired power station, uses the extracted steam from the steam turbine and the high-temperature air at the outlet of the boiler air preheater as the electrolyzer stack materials, operates the electrolyzer stack in the exothermic mode, and cancels the key cold components (fans, pumps, water treatment, recirculation fans, etc.) and key hot components (steam generators, gas preheaters, tail gas coolers, high-temperature electric heating, etc.) of the traditional SOE hydrogen production system, realizing 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 electrolyzer stack, the compactness of the SOE hot box is further improved, and the heat dissipation loss of the high-temperature system is reduced. Finally, 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 exported by the SOE hydrogen production system in the present invention has a higher temperature and carries more heat, and has a better effect on stabilizing combustion at low loads after being fed into the boiler furnace. The SOE hydrogen production system switches between the hydrogen production mode and the hot standby mode daily, operates in the hydrogen production mode during the deep peak shaving period of the coal-fired power station, and operates in the hot standby mode during the non-peak shaving period. Through the rapid switching from the hot standby mode to the hydrogen production mode, the peak shaving response speed of the coupled power station is improved.

[0051] The regulation method of the auxiliary - free solid oxide electrolysis hydrogen production system provided by this embodiment specifically compares the comprehensive efficiency and peak - shaving ability of the coupled system, selects different extraction ports according to the power generation load rate of the coal - fired power station to provide high - temperature steam for the SOE hydrogen production system, so as to achieve the purpose of flexible extraction at different times and improve the energy utilization efficiency of the system;

[0052] By comparing the differences in the comprehensive energy utilization efficiency of the coupled system under different working conditions and different extractions, determine the flexible extraction strategy of the steam turbine subsystem at different times, and obtain an optimized extraction regulation plan for the system. The specific operation can be achieved by opening and closing the first valve 21 and the second valve 22 of the steam turbine unit in different time periods. When the power generation load rate of the coal - fired power station is greater than the critical load ζ, close the first valve 21 and open the second valve 22 to supply steam to the SOE hydrogen production system using the sixth - stage extraction; when the power generation load rate of the coal - fired power station is less than or equal to the critical load ζ, open the first valve 21 and close the second valve 22 to supply steam to the SOE hydrogen production system using the fifth - stage extraction, so that the supplied steam parameters are always matched with the steam characteristics required by the SOE, thereby improving the energy efficiency of the coupled system and the economic operation of the coupled system.

[0053] By coupling the SOE hydrogen production system with the coal - fired power station, enhance the deep peak - shaving ability of the coal - fired power station, provide a deep peak - shaving technical solution for the coal - fired power station to operate below the technical minimum output, or even operate without shutting down and with the grid - connected power being 0, reduce the number of unit starts and stops, and improve the peak - shaving depth and operation flexibility of the coal - fired power station.

[0054] Embodiment 2

[0055] As Figure 2 shown, this embodiment provides another auxiliary - free solid oxide electrolysis hydrogen production system, which assists the coal - fired power station in deep peak - shaving. As can be seen from the figure, the difference from Embodiment 1 is that the third valve 37 is arranged on a newly added extraction pipeline branch on the fourth - stage extraction pipeline 16, that is, the third branch 28. In this embodiment, the high - temperature steam output from the fourth - stage extraction pipeline 16 of the low - pressure cylinder of the steam turbine unit is mixed with a small amount of the cathode outlet flow of the SOE hydrogen production system through the ejector 25, replacing the hydrogen premixing process in the conventional SOE electrolysis.

[0056] The auxiliary coal - power deep - peak - shaving method of the auxiliary - free solid oxide electrolysis hydrogen production system provided by this embodiment specifically selects the fourth - stage extraction port to provide high - temperature steam for the SOE hydrogen production system in combination with the actual situation of the coal - fired power station project. The fourth - stage extraction pipeline has been used in the original thermal system (deaerator) of the power plant, and reusing the existing pipeline can reduce the new investment. This Embodiment 2 can be used as an alternative to Embodiment 1.

[0057] The above embodiments are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, improvements and refinements made without departing from the principle of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A system for producing hydrogen by solid oxide electrolysis without auxiliary machinery, characterized in that: The invention comprises an 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) is operated 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.

2. The system for producing hydrogen by solid oxide electrolysis without auxiliary machinery according to claim 1, characterized in that: The external heat source comprises a coal-fired power plant, which comprises a boiler subsystem and a steam turbine subsystem. The auxiliary-free solid oxide electrolysis hydrogen production system is coupled with the coal-fired power plant, and the coupling comprises 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 eject 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 mixed gas through the ejector (25), and then enter the cathode inlet of the SOE hot box system after passing through the mixed outlet of the ejector (25), and the remaining product produced by the SOE hot box system is 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.

3. The system for producing hydrogen by electrolysis of solid oxide without auxiliary machinery according to claim 2, characterized in that: 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.

4. The system for producing hydrogen by electrolysis of solid oxide without auxiliary machinery according to claim 3, characterized in that: 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 turn after dust removal. 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.

5. The system for producing hydrogen by electrolysis of solid oxide without auxiliary machinery according to claim 2, characterized in that: The hydrogen storage subsystem comprises the gas-water separator (30), a dryer (31), a hydrogen compressor (32) and a hydrogen storage tank (33) in sequence.

6. The system for producing hydrogen by solid oxide electrolysis without auxiliary machinery according to claim 2, characterized in that: The boiler subsystem comprises a boiler body (1) and an air preheater (2), wherein 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). The cylinder (4) is connected to the deaerator (10), 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 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); the first valve (21) and the second valve (22) are arranged on the first branch (23) and the second branch (24) respectively, and the first and second branches are both connected to the high-pressure inlet of the ejector (25).

7. The system for producing hydrogen by solid oxide electrolysis without auxiliary machinery according to claim 6, 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 is 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). The gas-water separator (30) is used to cool the hydrogen-containing water vapor after heat exchange in the heat exchanger and is passed into the deaerator (10) after absorbing heat and heating.

8. The system for producing hydrogen by solid oxide electrolysis without auxiliary machinery according to claim 7, characterized in that: The heat exchanger is selected from a multi-stream heat exchanger (28).

9. The system for producing hydrogen by solid oxide electrolysis without auxiliary machinery according to claim 8, characterized in that: The multi-stream heat exchanger (28) is selected from a plate type or a plate-fin type.

10. An auxiliary coal-to-electricity deep regulation method for a solid oxide electrolysis hydrogen production system without auxiliary machinery according to any one of claims 6 to 9, 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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