Method for realizing low NOx emission by using water vapor to regulate coal ammonia blending combustion process

Abstract

This invention belongs to the technical field of ammonia energy power generation and discloses a method for achieving low NOx emissions by regulating the coal-ammonia blending combustion process using steam. The method includes: S1, arranging a liquid water delivery module on one side of the furnace; this module includes a liquid water storage station, a vacuum pump, an expansion nozzle, and a water supply pipeline, thereby continuously injecting liquid water into the furnace combustion zone in a controllable and reliable manner; S2, the liquid water rapidly vaporizes into steam at high temperature and reacts with coke in a water-gas reaction, directly generating CO and H2, while some ammonia decomposes at high temperature to generate CO; through this reaction mechanism, the CO generation rate is higher than the NOx generation rate, and H / OH radicals are preferentially used for CO generation. This invention not only solves the problems of high cost and difficult retrofitting in existing low-NOx emission technologies, but also eliminates the need for additional energy during the entire regulation process, making it easy to control and allowing for flexible adjustment according to different operating conditions.

Description

Technical Field

[0001] This invention belongs to the technical field of ammonia energy power generation, and more specifically, relates to a method for achieving low NOx emissions by using steam to regulate the coal-ammonia blending combustion process. Background Technology

[0002] The extensive use of fossil fuels has exacerbated the global greenhouse effect, causing a series of environmental problems that threaten human survival. Furthermore, the production of electricity from fossil fuels generates substantial carbon emissions. To address this issue, it is essential to replace some of the electricity generated from fossil fuels with low-carbon energy sources. This has led to the development of ammonia-blended combustion in coal-fired power plants. Ammonia, as a low-carbon energy source, does not produce carbon emissions during combustion. However, because ammonia is composed of NH3, incomplete combustion during combustion can lead to NO (NOx). x The dramatic increase in the generation of these pollutants has caused photochemical pollution, threatening life and health.

[0003] Among existing technologies, the more mature low-NOx technology is currently... x Combustion methods mainly fall into three categories: burner modification; air distribution adjustment; and staged air and fuel combustion. For example, a patent search revealed that CN119535965A discloses a method for controlling NO in the SCR inlet flue gas of a coal-fired unit co-fired with green ammonia. x CN115930220B discloses a method and system for controlling NO concentration using plasma-assisted ammonia-infused combustion in a coal-fired boiler. x The research on ultra-low emission systems and methods discloses burner modification and fuel staged combustion modification schemes. With the increasing prevalence of ammonia-blended power plants, it is necessary to continue making technological improvements based on these studies. Summary of the Invention

[0004] To address one or more of the above-mentioned deficiencies or needs of existing technologies, this invention provides a method for achieving low NOx emissions by regulating the coal-fired ammonia-blended combustion process using steam. Based on existing ammonia-blended combustion equipment in coal-fired power plants, a cleverly designed reaction route utilizes steam to increase the CO concentration in the main combustion zone, thereby effectively suppressing NOx formation. This not only solves the pain points of high cost and difficult retrofitting in existing technologies for low NOx emissions, but also eliminates the need for additional energy during the entire regulation process, making it easy to control and flexibly adjustable according to different operating conditions. Therefore, it is particularly suitable for ammonia-blended combustion applications in various large and medium-sized coal-fired power plants.

[0005] To achieve the above objectives, according to the present invention, a method for achieving low NOx emissions by controlling the coal-ammonia blending combustion process using steam is provided, wherein the method includes the following steps: S1, Arrangement of the liquid water delivery module A liquid water delivery module is installed on one side of the furnace in a coal-fired power plant where ammonia is added for combustion. The liquid water delivery module includes a liquid water storage station, a vacuum pump, an expansion nozzle, and a water supply pipeline. The vacuum pump is used to controllably extract liquid water from the liquid water storage station and deliver it to the expansion nozzle via the water supply pipeline. The first end face of the expansion nozzle, which has a relatively small cross-section, is connected to the vacuum pump, and its second end face, which has a relatively large cross-section, is connected to the secondary air inlet of the furnace, for continuously injecting liquid water into the combustion zone of the furnace. S2, Achieving Low NOx Emissions The injected liquid water rapidly vaporizes into water vapor at high temperature and reacts with coke in a water-gas reaction: C + H2O = CO + H2. This reaction is endothermic and spontaneously intensifies in the region above 800℃, directly generating CO and H2. At the same time, some ammonia undergoes a decomposition reaction at high temperature: 2NH3 = N2 + 3H2, which further increases the generation of CO. In this way, the reaction rate of CO formation is higher than that of NOx formation, and H / OH radicals are preferentially used for CO formation, thereby achieving low NOx emissions throughout the entire coal-ammonia combustion process.

[0006] As a further preferred embodiment of the present invention, the liquid water continuously injected by the expansion nozzle preferably accounts for 0.1% to 0.5% of the total flue gas volume in the combustion zone of the furnace.

[0007] As a further preferred embodiment of the present invention, the expansion nozzle is preferably designed to continuously inject liquid water into a location where the temperature in the combustion zone of the furnace exceeds 800°C.

[0008] As a further preferred embodiment of the present invention, the liquid water delivery module preferably further includes a control unit, which is used to sense and adjust the flow rate, pressure, specific volume and other fluid parameters of the liquid water injected into the combustion zone of the furnace in real time.

[0009] As a further preferred embodiment of the present invention, the liquid water delivery module preferably further includes a detection unit and a control unit, wherein the detection unit is used to measure parameters such as real-time temperature and flue gas volume in the furnace combustion zone in real time and send them to the control unit; the control unit provides different control feedback based on the received relevant parameters in the furnace combustion zone and in combination with the relevant parameters of liquid water sensed by the control unit.

[0010] As a further preferred embodiment of the present invention, the above process does not require modification of the burner and / or adjustment of air distribution, air grading and fuel grading combustion.

[0011] In summary, the technical solutions conceived by this invention have the following main technical advantages compared with the prior art: (1) In terms of the design of the reaction mechanism, this invention introduces water vapor to increase the CO concentration in the main combustion zone, which in turn makes the CO generation reaction rate higher than the NOx generation reaction rate. On this basis, combined with some CO generated by the partial decomposition of ammonia, the CO concentration in the main combustion zone increases dramatically, and H / OH free radicals are preferentially used for CO generation. This reaction mechanism, which makes full use of the competition between CO and NO to effectively inhibit NOx generation, can achieve low NOx in the entire coal-ammonia combustion process without making much equipment modification to existing coal-ammonia power plants, in a low-cost and significantly reduced modification difficulty manner. x emission; (2) Regarding the targeted design of the liquid water delivery module, the present invention uses an expanding nozzle to continuously inject liquid water into the combustion zone of the furnace. This effectively avoids the loss caused by direct injection of liquid water into the secondary air duct, and is more conducive to the subsequent generation of steam and the full progress of water-gas reaction. In addition, by further limiting the specific volume fraction of the injected liquid water, many actual tests have shown that it can provide sufficient CO concentration while ensuring that the overall combustion characteristics of the main combustion zone do not deteriorate. At the same time, the continuous injection of liquid water at a position in the combustion zone of the furnace where the temperature exceeds 800°C will help to rapidly increase the CO concentration and production. (3) In terms of the design of the supporting detection and control unit, the present invention uses a control unit to sense and adjust the flow rate, pressure, specific volume and other fluid parameters of liquid water in real time, uses a detection unit to measure the real-time temperature, flue gas volume and other parameters in the combustion zone of the furnace in real time, and uses a control unit to provide different control feedback, so that flexible and quick adjustment can be achieved according to different working conditions. In this way, the above reaction mechanism can be better utilized to achieve low NO in the entire coal-ammonia combustion process. x emission; (4) The process method according to the present invention not only solves the problems of high cost and difficulty of transformation of low NOx emission in the prior art, but also does not require additional energy to control the entire control process, and can be flexibly adjusted according to different working conditions. Therefore, it is especially suitable for the application of ammonia combustion in various large and medium-sized coal-fired power plants. Attached Figure Description

[0012] Figure 1 This is a process flow diagram of a method for achieving low NOx emissions by using steam to regulate the coal-ammonia blending combustion process according to the present invention; Figure 2 This is a schematic diagram of the liquid water transport module arrangement for implementing the process method of the present invention; Figure 3It is a schematic diagram illustrating the structure of the primary air duct, secondary air duct, and ammonia pipe inside a coal-fired ammonia combustion furnace. In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 11-Liquid water storage station; 12-Vacuum pump; 13-Expansion nozzle; 14-Water supply pipeline; 21-Primary air duct; 22-Primary air inlet; 31-Secondary air duct; 32-Secondary air inlet; 41-Ammonia pipe. Detailed Implementation

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] Figure 1 This is a process flow diagram of a method for achieving low NOx emissions by using steam to regulate the coal-ammonia blending combustion process according to the present invention. The following will be combined with... Figure 1 To explain the invention in more detail.

[0019] According to the present invention, a method for achieving low NOx emissions by controlling the coal-ammonia blending combustion process using steam is provided, which mainly includes the following steps: First, a liquid water delivery module needs to be installed.

[0020] During this process, a liquid water delivery module is installed on one side of the furnace where ammonia is added for combustion in a coal-fired power plant; see also... Figure 2 and Figure 3 The liquid water delivery module includes a liquid water storage station 11, a vacuum pump 12, an expansion nozzle 13, and a water supply pipeline 14. The vacuum pump 12 is used to controllably extract liquid water from the liquid water storage station 11 and deliver it to the expansion nozzle 13 via the water supply pipeline 14. The first end face of the expansion nozzle 13, which has a relatively small cross-section, is connected to the vacuum pump 12, and its second end face, which has a relatively large cross-section, is connected to the secondary air inlet 32 ​​of the furnace, for continuously injecting liquid water into the combustion zone of the furnace. Next is the process of achieving low NOx emissions.

[0021] During this process, the sufficient amount of liquid water injected by the expansion nozzle 13 rapidly vaporizes into water vapor at high temperature and reacts with coke in a water-gas reaction: C + H2O = CO + H2. This reaction is endothermic and spontaneously intensifies in the region exceeding 800℃, directly generating CO and H2. At the same time, some ammonia undergoes a decomposition reaction at high temperature: 2NH3 = N2 + 3H2, which further increases the generation of CO. In this way, CO concentration increases while NO formation is suppressed. The main reason is that CO formation depends on H / OH radicals, as does NO formation. Furthermore, in the reaction process described in this invention, the reaction rate of CO formation (ROP) is higher than that of NO, while NO's dependence on H / OH radicals is greater than that of CO. Therefore, under the same combustion conditions, H / OH radicals will preferentially be used for CO formation, resulting in a higher CO formation rate than the NOx (e.g., NO) formation rate. This, in turn, allows H / OH radicals to preferentially be used for CO formation, thereby achieving low NOx emissions throughout the coal-ammonia blending combustion process.

[0022] The design principles of this invention will be explained in more detail and clarity below.

[0023] First, a large amount of NOx is generated during the combustion of coal with ammonia. Through the specific analysis of the above reaction mechanism, it is easy to find that CO and NO compete for H / OH free radicals, and CO is more competitive than NOx. Therefore, this invention aims to fully increase the CO concentration in the main combustion zone to suppress the generation of NOx. The presence of water vapor will cause the CO concentration in the main combustion zone to increase dramatically, thereby achieving low NOx emission from coal with ammonia combustion at a low cost and greatly reducing the difficulty of modification. Secondly, the main reason for choosing liquid water in this invention is that the secondary air temperature is approximately 200°C, which is sufficient to vaporize this liquid water into water vapor without requiring additional energy. Furthermore, this raw material is low in cost and readily available. In addition, this invention specifically chooses secondary air input because primary air carries pulverized coal. If water vapor enters the primary air system, it easily wets the pulverized coal, leading to poor combustion characteristics. The wetted pulverized coal is also prone to accumulating in the pipes, causing blockages. Secondary air input avoids these problems and ensures the smooth progress of the above reaction process. Third, considering that liquid water needs to enter the medium- and high-temperature pipeline, in order to avoid the liquid water directly spraying onto the secondary air duct wall and causing damage, this system adopts a specially designed expansion nozzle: the end of this nozzle with a larger cross-sectional area is connected to the secondary air inlet, and the end with a smaller cross-sectional area is connected to the vacuum pump, thereby reducing the flow rate of liquid water entering the secondary air duct. This not only prevents the liquid water from directly contacting the secondary air duct, which would cause the secondary air duct to corrode and become embrittled, but also facilitates the subsequent generation of water vapor and the full progress of the water-gas reaction. Fourth, in this invention, the injected liquid water accounts for 0.1% to 0.5% of the total flue gas volume in the combustion zone of the furnace. Numerous practical tests have shown that if the water vapor content is too high, the overall combustion characteristics will deteriorate; if it is too low, the CO concentration will be insufficient, failing to effectively suppress NOx formation. Furthermore, the liquid water is introduced via a vacuum pump, the flow rate of which is calculated based on the total gas volume under actual operating conditions. Preferably, the liquid water is injected at a location within the burner where the combustion zone temperature exceeds 800°C.

[0024] According to a preferred embodiment of the present invention, the liquid water delivery module preferably further includes a control unit, which is used to sense and adjust the flow rate, pressure, specific volume and other fluid parameters of the liquid water injected into the combustion zone of the furnace in real time.

[0025] According to another preferred embodiment of the present invention, the liquid water delivery module preferably further includes a detection unit and a control unit, wherein the detection unit is used to measure parameters such as real-time temperature and flue gas volume in the furnace combustion zone in real time and send them to the control unit; the control unit provides different control feedback based on the received relevant parameters in the furnace combustion zone and in combination with the relevant parameters of liquid water sensed by the control unit.

[0026] In summary, the process method described above, based on existing ammonia-blended combustion equipment in coal-fired power plants, ingeniously designs a reaction route that utilizes steam to increase the CO concentration in the main combustion zone, thereby effectively suppressing NOx generation. Compared with existing technologies that focus on modifying burners, adjusting air distribution, air staging, and fuel staging combustion, this method not only solves the pain points of high cost and difficult modification for low NOx emissions in existing technologies, but also eliminates the need for additional energy during the entire control process, making it easy to operate. Furthermore, it can be flexibly adjusted according to different operating conditions, making it particularly suitable for ammonia-blended combustion applications in various large and medium-sized coal-fired power plants, and possessing good practical value and application prospects.

[0027] 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 method for regulating coal ammonia blending combustion process by using water vapor to achieve low NOx emission, characterized in that, The method includes the following steps: S1, Arrangement of the liquid water delivery module A liquid water delivery module is installed on one side of the furnace in a coal-fired power plant where ammonia is added for combustion. The liquid water delivery module includes a liquid water storage station (11), a vacuum pump (12), an expansion nozzle (13), and a water supply pipeline (14). The vacuum pump (12) is used to controllably extract liquid water from the liquid water storage station (11) and deliver it to the expansion nozzle (13) via the water supply pipeline (14). The first end face of the expansion nozzle (13), which has a relatively small cross-section, is connected to the vacuum pump (12), and its second end face, which has a relatively large cross-section, is connected to the secondary air inlet (32) of the furnace, for continuously injecting liquid water into the combustion zone of the furnace. S2, Achieving Low NOx Emissions The injected liquid water rapidly vaporizes into water vapor at high temperature and reacts with coke in a water-gas reaction: C + H2O = CO + H2. This reaction is endothermic and spontaneously intensifies in the region above 800℃, directly generating CO and H2. At the same time, some ammonia undergoes a decomposition reaction at high temperature: 2NH3 = N2 + 3H2, which further increases the generation of CO. In this way, the reaction rate of CO formation is higher than that of NOx formation, and H / OH radicals are preferentially used for CO formation, thereby achieving low NOx emissions throughout the entire coal-ammonia combustion process.

2. The method of claim 1, wherein, The liquid water continuously injected by the expansion nozzle (13) preferably accounts for 0.1% to 0.5% of the total flue gas volume in the combustion zone of the furnace.

3. The method of claim 1 or 2, wherein, The expansion nozzle (13) is preferably designed to continuously inject liquid water into a location where the temperature in the combustion zone of the furnace exceeds 800°C.

4. The method according to any one of claims 1 to 3, characterized in that, The liquid water delivery module preferably also includes a control unit, which is used to sense and adjust the flow rate, pressure, specific volume and other fluid parameters of the liquid water injected into the combustion zone of the furnace in real time.

5. The method as described in claim 4, characterized in that, The liquid water delivery module preferably further includes a detection unit and a control unit. The detection unit is used to measure parameters such as real-time temperature and flue gas volume in the furnace combustion zone in real time and send them to the control unit. The control unit provides different control feedback based on the received relevant parameters in the furnace combustion zone and the relevant parameters of liquid water sensed by the control unit.

6. The method according to any one of claims 1-5, characterized in that, The above process does not require modification of the burner, and / or adjustment of air distribution, air grading, and fuel grading combustion.

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