Hydrogen blending combustion method for fast load change of coal-fired power plant

Abstract

The present application belongs to the technical field of coal-fired power station coupling clean energy power generation, and discloses a hydrogen-doped combustion method for quick load change of a coal-fired power station, comprising: S1, for the coal-fired power station as a working target, a quick load change system including a flue gas condensate water recovery unit, an electrolytic water hydrogen production unit, a hydrogen storage unit and a solar heat collection unit is arranged for the coal-fired power station; S2, according to the comparison between different load change requirements and a plurality of preset threshold values, a plurality of corresponding working modes are determined to be executed, so as to jointly realize quick load change. Through the present application, the quick load change of the coal-fired power station can be realized only by introducing electrolytic water hydrogen production without the need for internal adjustment of boiler and steam turbine parameters, and the present application has the advantages of convenient operation, significantly improved load change rate, flexible adjustment, convenient quick peak regulation and the like, and is particularly suitable for application occasions of hydrogen-doped combustion of various large and medium-sized coal-fired power stations.

Description

Technical Field

[0001] This invention belongs to the technical field of coal-fired power plants coupled with clean energy power generation, and more specifically, relates to a hydrogen-blended combustion method for rapid load changes in coal-fired power plants. Background Technology

[0002] Currently, massive anthropogenic emissions of greenhouse gases are exacerbating global warming, causing not only a series of environmental problems such as glacial melting and rising sea levels, but also gradually threatening human health. Carbon dioxide, as the most significant greenhouse gas, has received widespread attention worldwide. Coal-fired power plants are one of the main sources of carbon dioxide emissions in China, and reducing carbon dioxide emissions from coal-fired power plants is of great significance for reducing China's total carbon emissions and greenhouse gas emissions.

[0003] Ammonia co-firing technology in coal-fired power plants is gaining increasing popularity as a cutting-edge energy utilization method. However, during load fluctuations in coal-fired power units, load control is achieved by adjusting the amount of fuel fed into the boiler and the opening of the main steam valve of the turbine to meet load response rate requirements. This adjustment method is prone to causing drastic fluctuations in main steam parameters, leading to a decrease in unit economic efficiency. Currently, the load fluctuation capacity of units is generally 1-2% of rated load / minute, and the world's largest peak-shaving capacity is only 3.5% of rated load / minute. With the increasing proportion of renewable energy sources, existing load rate adjustment methods are no longer sufficient to meet the requirements of rapid peak shaving.

[0004] To address the aforementioned issues, existing technologies primarily focus on the design and optimization of internal regulation methods. During traditional load changes, regulation typically relies solely on adjusting the opening of the turbine's main steam valve to control the amount of fuel entering the boiler. This method, relying solely on internal regulation, not only fails to achieve rapid load changes but also reduces the stability and economic efficiency of the power plant. For example, CN111564871B discloses an adaptive load change command generation method and apparatus based on the thermal inertia of a coal-fired power plant, and CN111564871A discloses an adaptive load change command generation method and apparatus based on the thermal inertia of a coal-fired power plant. However, these early patents still fail to fundamentally achieve rapid load changes and cannot resolve the issues of reduced power plant stability and economic efficiency during load changes. Accordingly, further research and improvement in this area are urgently needed to address these technical challenges. Summary of the Invention

[0005] To address one or more of the above-mentioned deficiencies or needs of existing technologies, this invention provides a hydrogen-blended combustion method for rapid load changes in coal-fired power plants. Based on existing coal-fired power plant equipment, the method improves the design of its specific operating conditions and response modes. Consequently, without the need for internal adjustments to boiler and turbine parameters, rapid load changes in coal-fired power plants can be achieved simply by introducing hydrogen produced through water electrolysis. This method also offers advantages such as ease of operation, significantly improved load change rate, flexible adjustment, and convenient rapid peak shaving. Therefore, it is particularly suitable for applications involving ammonia-blended combustion in various large and medium-sized coal-fired power plants.

[0006] To achieve the above objectives, according to the present invention, a hydrogen-blended combustion method for rapid load changes in coal-fired power plants is provided, wherein the method includes the following steps: S1. Arrangement of the rapid load change system For the coal-fired power plant that is the target of the work, a supporting rapid load change system is set up. The system includes a flue gas condensate recovery unit, an electrolysis hydrogen production unit, a hydrogen storage unit, and a solar thermal collection unit. The flue gas condensate recovery unit is used to condense and recover high-temperature water vapor in the flue gas generated by the coal-fired power plant, and divides the liquid water obtained from the condensation recovery into two parts, one part of which is sent to the water electrolysis hydrogen production unit and the other part is sent to the solar thermal collector unit. The water electrolysis hydrogen production unit is used to electrolyze the liquid water delivered here to produce hydrogen, and to deliver the purified hydrogen to the hydrogen storage unit for storage; the hydrogen storage unit has a built-in flow regulator and is used to controllably send hydrogen into the boiler furnace of the coal power plant for combustion according to different operating conditions; the solar thermal collector unit is used to heat and use the liquid water delivered here. S2, Implementation of rapid load change The rapid load change system executes the following different operating modes according to the load change requirements of the coal-fired power plant: First working mode: When the coal-fired power plant performs a rapid load increase and the load increase is less than or equal to a preset first threshold, the hydrogen storage unit directly introduces the stored hydrogen into the boiler furnace of the coal-fired power plant through a pipeline for combustion. Second working mode: When the coal-fired power plant performs a rapid load increase and the load increase value is greater than the first threshold, the electrolyzer of the water electrolysis hydrogen production unit starts to produce hydrogen, and mixes the newly produced hydrogen with the hydrogen stored in the hydrogen storage unit, and then sends it into the boiler furnace of the coal-fired power plant for combustion in conjunction with the secondary air. The third working mode: When the coal-fired power plant performs a rapid load reduction and the load reduction value is less than or equal to the preset second threshold, the flue gas condensate recovery unit opens the valve to introduce water vapor in the flue gas generated by the coal-fired power plant for condensation and recovery, and then sends a portion of the liquid water obtained from the condensation recovery to the electrolyzer of the water electrolysis hydrogen production unit to produce hydrogen for later use. Fourth working mode: When the coal-fired power plant performs a rapid load reduction and the load reduction magnitude is greater than the second threshold, the flue gas condensate recovery unit closes the valve and introduces the water vapor in the flue gas generated by the coal-fired power plant into the heat recovery device attached to the coal-fired power plant. After the heat recovery is completed, the water vapor is introduced into the flue gas condensate recovery unit again for condensation and recovery. Then, the liquid water obtained from the condensation and recovery is sent to the electrolyzer of the water electrolysis hydrogen production unit to produce hydrogen for later use.

[0007] As a further preferred embodiment of the present invention, the flue gas condensate recovery unit is preferably located at the tail end of the boiler in a coal-fired power plant.

[0008] As a further preferred embodiment of the present invention, the water electrolysis hydrogen production unit preferably utilizes off-peak electricity from a coal-fired power plant at night for the hydrogen production process.

[0009] As a further preferred embodiment of the present invention, the first threshold is preferably set to 1.5%.

[0010] As a further preferred embodiment of the present invention, the second threshold is preferably set to 1%.

[0011] As a further preferred embodiment of the present invention, the flue gas condensate recovery unit preferably has a built-in flow detector, which is used to monitor the flow rate of water vapor in real time and control the opening and closing of the valve.

[0012] As a further preferred embodiment of the present invention, the above-mentioned hydrogen-blended combustion process does not require adjustment of the internal parameters of the boiler and turbine of the coal-fired power plant.

[0013] As a further preferred embodiment of the present invention, the coal-fired power plant is preferably a large or medium-sized coal-fired power plant that uses ammonia-blended combustion.

[0014] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages: (1) This invention fully combines the specific needs of rapid load change. Based on the existing coal-fired power plant equipment, it introduces hydrogen production by electrolysis of water and combines different load change requirements to execute the corresponding working mode. Accordingly, during the period of load increase, hydrogen can be quickly and accurately transported into the boiler furnace to participate in the rapid load increase. During the period of load reduction, excess high-temperature water vapor can be quickly recovered, thereby achieving the purpose of helping coal-fired power plants to quickly reduce the load. (2) The multiple working modes designed in this invention work together to produce hydrogen by using off-peak electricity from coal-fired power plants at night to supply the electrolyzers of the water electrolysis hydrogen production unit and store the excess hydrogen in the hydrogen storage unit. When the load needs to be increased quickly, the hydrogen stored in the hydrogen storage unit and the newly produced hydrogen are used as high-calorific-value gaseous fuels to help the coal-fired power plants change load quickly, significantly improving the load change rate and meeting the needs of rapid peak shaving. (3) The process method of the present invention also solves a long-standing technical problem in the field: traditional coal-fired power plants usually control the load by adjusting the amount of fuel fed into the boiler or the opening of the main steam valve of the turbine. This method is complicated to operate, has limited load-changing capacity, and will lead to a decrease in the stability and economy of the power plant during load changes, thereby increasing the difficulty, cost and efficiency of coupling coal-fired power plants with new energy sources. The present invention can solve the above problems in a better and more comprehensive way, and has the advantages of easy operation, rapid load change and flexible adjustment. Therefore, it is particularly suitable for the application of ammonia combustion in various large and medium-sized coal-fired power plants. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of a hydrogen-blended combustion method for rapid load change in coal-fired power plants provided by the present invention. Figure 2 This is a schematic diagram illustrating the composition and layout of a rapid load-changing system for demonstrating the process method of the present invention; In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-Coal-fired power plant; 2-Boiler; 11-Flue gas condensate recovery unit; 12-Electrolysis water hydrogen production unit; 13-Hydrogen storage unit; 101-Condensate; 102-Electric power; 103-Hydrogen. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0017] It should be understood that expressions such as "comprising" and "may include" as used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0018] It should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0019] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0020] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] Figure 1 This is a process flow diagram of a hydrogen-blended combustion method for rapid load changes in coal-fired power plants provided by the present invention. Figure 2 This is a schematic diagram illustrating the composition and layout of a rapid load-changing system for demonstrating the process method of this invention. The following will be combined with... Figure 1 and Figure 2 To explain the invention in more detail.

[0022] like Figure 1 As shown, this invention provides a hydrogen-blended combustion method for rapid load changes in coal-fired power plants, which mainly includes the following steps: First, there is the arrangement of the rapid load change system.

[0023] In this step, a rapid load change system is set up for the coal-fired power plant that is the target of the work. The system includes a flue gas condensate recovery unit, an electrolysis hydrogen production unit, a hydrogen storage unit, and a solar thermal collection unit. The flue gas condensate recovery unit is used to condense and recover high-temperature water vapor in the flue gas generated by the coal-fired power plant, and divides the liquid water obtained from the condensation recovery into two parts, one part of which is sent to the water electrolysis hydrogen production unit and the other part is sent to the solar thermal collector unit. The water electrolysis hydrogen production unit is used to electrolyze the liquid water delivered here to produce hydrogen, and to deliver the purified hydrogen to the hydrogen storage unit for storage; the hydrogen storage unit has a built-in flow regulator and is used to controllably send hydrogen into the boiler furnace of the coal power plant for combustion according to different operating conditions; the solar thermal collector unit is used to heat and use the liquid water delivered here.

[0024] More specifically, the basic structure and composition of coal-fired power plants, such as large and medium-sized coal-fired power plants using ammonia-blended combustion, are well known to those skilled in the art and will not be described in detail here. Based on existing coal-fired power plant equipment, this invention creatively designs a matching rapid load-changing system.

[0025] like Figure 2 As illustrated in the example, the rapid load change system of this invention specifically includes a flue gas condensate recovery unit, an electrolysis hydrogen production unit, a hydrogen storage unit, and a solar thermal collection unit. Its core concept lies in using high-calorific-value hydrogen fuel to assist in load changes at coal-fired power plants. This hydrogen fuel is directly derived from the large amount of high-temperature steam contained in the flue gas produced by the coal-fired power plant itself. Simultaneously, the energy required for hydrogen production can also be directly provided by the coal-fired power plant (e.g., off-peak electricity at night). This method enables rapid load changes without adjusting the parameters of the boiler and turbine of the coal-fired power plant, significantly improving the load change rate and meeting the needs of rapid peak shaving. Furthermore, this rapid load change system can quickly and conveniently recover excess high-temperature steam according to specific needs, thereby helping the coal-fired power plant to rapidly reduce its load.

[0026] It should be noted that the specific structural components of the flue gas condensate recovery unit, water electrolysis hydrogen production unit, hydrogen storage unit, and solar thermal collector unit can all adopt conventional forms, and therefore will not be explained in detail here, as long as they can meet the basic functions indicated by this invention. Furthermore, the rapid load change system of this invention may also include an electrical control subsystem for controlling the pressure, temperature, and valve opening and closing of the entire system.

[0027] Next, the process of implementing rapid load changes.

[0028] During this process, the rapid load change system executes the following different operating modes according to the load change requirements of the coal-fired power plant: First working mode: When the coal-fired power plant performs a rapid load increase and the load increase is less than or equal to a preset first threshold, the hydrogen storage unit directly introduces the stored hydrogen into the boiler furnace of the coal-fired power plant through a pipeline for combustion. Second working mode: When the coal-fired power plant performs a rapid load increase and the load increase value is greater than the first threshold, the electrolyzer of the water electrolysis hydrogen production unit starts to produce hydrogen, and mixes the newly produced hydrogen with the hydrogen stored in the hydrogen storage unit, and then sends it into the boiler furnace of the coal-fired power plant for combustion in conjunction with the secondary air. The third working mode: When the coal-fired power plant performs a rapid load reduction and the load reduction value is less than or equal to the preset second threshold, the flue gas condensate recovery unit opens the valve to introduce water vapor in the flue gas generated by the coal-fired power plant for condensation and recovery, and then sends a portion of the liquid water obtained from the condensation recovery to the electrolyzer of the water electrolysis hydrogen production unit to produce hydrogen for later use. Fourth working mode: When the coal-fired power plant performs a rapid load reduction and the load reduction magnitude is greater than the second threshold, the flue gas condensate recovery unit closes the valve and introduces the water vapor in the flue gas generated by the coal-fired power plant into the heat recovery device attached to the coal-fired power plant. After the heat recovery is completed, the water vapor is introduced into the flue gas condensate recovery unit again for condensation and recovery. Then, the liquid water obtained from the condensation and recovery is sent to the electrolyzer of the water electrolysis hydrogen production unit to produce hydrogen for later use.

[0029] More specifically, since the flue gas produced in the coal-fired power plant 1 (e.g., an ammonia-blended coal-fired power plant) contains a large amount of water vapor, in this invention, a flue gas condensate recovery unit 11 can be installed at the tail end of the boiler 2 to collect the large amount of water vapor. The flue gas condensate recovery unit 11 sends this water vapor into the electrolyzer of the water electrolysis hydrogen production unit 12. Preferably, off-peak electricity at night can be used for water electrolysis hydrogen production. After purification, the hydrogen enters the hydrogen storage unit 13. The hydrogen storage unit 13 preferably has a built-in automatically controlled flow regulator. This flow regulator adjusts the hydrogen flow rate according to the load increase to achieve small load increase operation. Once the required hydrogen flow rate exceeds the set critical value, the regulator transmits a signal to the electrolyzer, and the electrolyzer starts the hydrogen production operation to replenish the required amount of hydrogen.

[0030] For example, when the load increase is lower than or equal to a preset first threshold (e.g., 1.5%), hydrogen 103 is directly fed from the hydrogen storage unit 13 into the furnace of the co-firing system for combustion. When the load increase is higher than the first threshold, the amount of stored hydrogen is insufficient to supplement the required heat. At this time, the electrolyzer of the water electrolysis hydrogen production unit 12 starts working. The hydrogen produced by the electrolyzer is mixed with the hydrogen in the hydrogen storage unit 13 and then sent into the furnace of the boiler 2 for combustion in conjunction with the secondary air to complete the load regulation.

[0031] For example, when the load reduction is lower than a preset second threshold (e.g., 1%), the flue gas condensate recovery unit 11 opens the valve to directly introduce high-temperature main steam into the condenser; the condensed water is sent to the electrolyzer of the water electrolysis hydrogen production unit 12 to produce hydrogen for use in the next load increase operation; when the load reduction is higher than the second threshold, the flue gas condensate recovery unit 11 closes the valve to introduce high-temperature main steam into the power plant's auxiliary heat recovery device, and after the heat recovery is completed, the steam is introduced back into the flue gas condensate recovery unit 11 for condensation, and the condensed liquid water is sent back to the electrolyzer of the water electrolysis hydrogen production unit 12 to produce hydrogen, and then stored in the hydrogen storage unit 13 for use in the next load increase operation.

[0032] The above-described process method of this invention effectively solves a long-standing technical problem in this field: traditional coal-fired power plants typically control load by adjusting the amount of fuel fed into the boiler or the opening of the turbine's main steam valve. This method is complex to operate, has limited load-changing capacity, and leads to a decrease in the stability and economy of the power plant during load changes, thereby increasing the difficulty, cost, and efficiency of coupling coal-fired power plants with new energy sources. This invention not only comprehensively solves the above problems but also has advantages such as easy operation, rapid load changing, and flexible adjustment. Therefore, it is particularly suitable for ammonia-blended combustion applications in various large and medium-sized coal-fired power plants and has good practical value and application prospects.

[0033] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A hydrogen-blended combustion method for rapid load change in coal-fired power plants, characterized in that, The method includes the following steps: S1. Arrangement of the rapid load change system For the coal-fired power plant that is the target of the work, a supporting rapid load change system is set up. The system includes a flue gas condensate recovery unit, an electrolysis hydrogen production unit, a hydrogen storage unit, and a solar thermal collection unit. The flue gas condensate recovery unit is used to condense and recover high-temperature water vapor in the flue gas generated by the coal-fired power plant, and divides the liquid water obtained from the condensation recovery into two parts, one part of which is sent to the water electrolysis hydrogen production unit and the other part is sent to the solar thermal collector unit. The water electrolysis hydrogen production unit is used to electrolyze the liquid water delivered here to produce hydrogen, and to deliver the purified hydrogen to the hydrogen storage unit for storage; the hydrogen storage unit has a built-in flow regulator and is used to controllably send hydrogen into the boiler furnace of the coal power plant for combustion according to different operating conditions; the solar thermal collector unit is used to heat and use the liquid water delivered here. S2, Implementation of rapid load change The rapid load change system executes the following different operating modes according to the load change requirements of the coal-fired power plant: First working mode: When the coal-fired power plant performs a rapid load increase and the load increase is less than or equal to a preset first threshold, the hydrogen storage unit directly introduces the stored hydrogen into the boiler furnace of the coal-fired power plant through a pipeline for combustion. Second working mode: When the coal-fired power plant performs a rapid load increase and the load increase value is greater than the first threshold, the electrolyzer of the water electrolysis hydrogen production unit starts to produce hydrogen, and mixes the newly produced hydrogen with the hydrogen stored in the hydrogen storage unit, and then sends it into the boiler furnace of the coal-fired power plant for combustion in conjunction with the secondary air. The third working mode: When the coal-fired power plant performs a rapid load reduction and the load reduction value is less than or equal to the preset second threshold, the flue gas condensate recovery unit opens the valve to introduce water vapor in the flue gas generated by the coal-fired power plant for condensation and recovery, and then sends a portion of the liquid water obtained from the condensation recovery to the electrolyzer of the water electrolysis hydrogen production unit to produce hydrogen for later use. Fourth working mode: When the coal-fired power plant performs a rapid load reduction and the load reduction magnitude is greater than the second threshold, the flue gas condensate recovery unit closes the valve and introduces the water vapor in the flue gas generated by the coal-fired power plant into the heat recovery device attached to the coal-fired power plant. After the heat recovery is completed, the water vapor is introduced into the flue gas condensate recovery unit again for condensation and recovery. Then, the liquid water obtained from the condensation and recovery is sent to the electrolyzer of the water electrolysis hydrogen production unit to produce hydrogen for later use.

2. The method as described in claim 1, characterized in that, The flue gas condensate recovery unit is preferably located at the tail end of the boiler in a coal-fired power plant.

3. The method as described in claim 1 or 2, characterized in that, The water electrolysis hydrogen production unit preferably utilizes off-peak electricity from a coal-fired power plant at night for the hydrogen production process.

4. The method according to any one of claims 1-3, characterized in that, The first threshold is preferably set to 1.5%.

5. The method as described in claim 4, characterized in that, The second threshold is preferably set to 1%.

6. The method according to any one of claims 1-5, characterized in that, The flue gas condensate recovery unit preferably has a built-in flow detector, which is used to monitor the flow rate of water vapor in real time and control the opening and closing of the valve.

7. The method according to any one of claims 1-6, characterized in that, The above-mentioned hydrogen-blended combustion process does not require adjustment of the boiler and turbine parameters of the coal-fired power plant.

8. The method according to any one of claims 1-7, characterized in that, The preferred coal-fired power plant is a large or medium-sized coal-fired power plant that uses ammonia-blended combustion.

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