An ammonia injection system for a low-medium temperature SCR denitration process

Abstract

The utility model belongs to flue gas denitration technical field discloses a kind of ammonia injection system for middle-low temperature SCR denitration process, including blast heating system, ammonia-air mixed evaporator, ammonia water vaporization system and reduction system, and the air inlet end of blast heating system is connected with ammonia-air mixed evaporator, and the gas inlet end of ammonia water vaporization system is connected with ammonia-air mixed evaporator, and the export end of ammonia-air mixed evaporator is connected with reduction system;The utility model can evaporate ammonia water first, utilize the shearing action and rapid heat exchange to ammonia water droplet in the high-speed flow process of steam, to realize the rapid gasification of ammonia water, and then after the ammonia gas of primary gasification is passed into ammonia-air mixed evaporator and is carried out secondary gasification, make ammonia water droplet further fully gasification, and the ammonia gas after fully gasification is passed into flue gas pipeline, can effectively avoid the situation such as plugging nozzle and catalyst surface crystallization, ensure that middle-low temperature SCR denitration system operation is reliable and stable.

Description

Technical Field

[0001] This utility model relates to the field of flue gas denitrification technology, specifically to an ammonia injection system for medium- and low-temperature SCR denitrification processes. Background Technology

[0002] Denitrification systems are technologies for treating nitrogen oxide (NOx) emissions from industrial waste gas. Their application stems from the serious environmental hazards posed by NOx, such as acid rain, photochemical smog, and ozone layer depletion. Selective catalytic reduction (SCR) is a highly efficient denitrification technology that uses a catalyst to selectively reduce NOx in flue gas to harmless N2 and H2O at 290-400℃ using a reducing agent (such as ammonia or urea). SCR is widely used in thermal power plants, diesel vehicles, and industrial boilers.

[0003] In existing medium- and low-temperature SCR denitrification systems, ammonia water needs to be converted into a gaseous state outside the flue. Currently, there are two types of ammonia water evaporation systems: Process 1, where hot steam indirectly heats ammonia water through a shell-and-tube heat exchanger, converting the ammonia water into a mixture of ammonia gas and water vapor, and the hot steam is discharged as condensate or recycled; Process 2, where hot flue gas or electrically heated air is used, and the heated air is introduced into an evaporator, where the injected ammonia water droplets are vaporized. This is a direct heat exchange, and the resulting gas is a mixture of air, water vapor, and ammonia gas.

[0004] However, the above-mentioned ammonia evaporation process still has problems: For process 1, the heat exchange of ammonia in the shell-and-tube heat exchanger is slow, the adjustability is poor, the outlet ammonia pressure is low, and the ammonia vaporization capacity is poorly adjustable; For process 2, the heat exchange effect is poor, the heat exchange is slow, the ammonia vaporization rate is low, the heat utilization efficiency is low, the equipment is prone to corrosion, the system reliability is poor, the on-site environment is complex and harsh, and dust will be blown into the evaporator by the fan, causing the ammonia to be adsorbed into the dust and unable to be completely vaporized. Ammonia droplets and dust accumulate at the nozzle and crystallize, thus clogging the nozzle. When the ammonia droplets that are not completely evaporated in the heat exchanger are sprayed into the flue gas and flow through the catalyst, they will form ammonium sulfate, ammonium chloride and other ammonium salts on the catalyst surface, causing crystallization on the catalyst surface and reducing the denitrification efficiency.

[0005] Based on the technical problems in the above-mentioned process, there is an urgent need for a high-efficiency ammonia injection system that is suitable for medium and low temperature SCR denitrification process. Utility Model Content

[0006] The purpose of this invention is to provide an ammonia injection system for medium- and low-temperature SCR denitrification processes to overcome the problems existing in the prior art. This invention can first evaporate ammonia water, utilizing the shearing effect and rapid heat exchange of ammonia water droplets during the high-speed flow of steam to achieve rapid vaporization of ammonia water. Then, the ammonia gas after primary vaporization is passed into an ammonia-air mixed evaporator for secondary vaporization, further fully vaporizing the ammonia water droplets. The fully vaporized ammonia gas is then passed into the flue gas pipeline, which can effectively avoid nozzle blockage and catalyst surface crystallization, ensuring reliable and stable operation of the medium- and low-temperature SCR denitrification system and significantly improving denitrification efficiency.

[0007] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0008] An ammonia injection system for medium- and low-temperature SCR denitrification process includes a blower heating system, an ammonia-air mixing evaporator, an ammonia-water vaporization system, and a reduction system;

[0009] The blower heating system is connected to the air inlet of the ammonia-air mixed evaporator, the ammonia-water vaporization system is connected to the air inlet of the ammonia-air mixed evaporator, and the outlet of the ammonia-air mixed evaporator is connected to the reduction system.

[0010] Furthermore, the ammonia vaporization system includes a steam unit, an ammonia unit, and an exhaust unit. The inlet of the steam unit is connected to the blower heating system, the outlet of the steam unit is connected to the first inlet of the exhaust unit, the liquid outlet of the ammonia unit is connected to the second inlet of the exhaust unit, and the outlet of the exhaust unit is connected to the inlet of the ammonia-air mixed evaporator.

[0011] Furthermore, the steam unit includes a steam inlet pipe, on which a steam manual valve, a steam desuperheating and pressure reducing valve, a steam flow regulating valve, a steam pressure gauge, a steam thermometer, and a steam flow meter are installed in sequence. The end of the steam inlet pipe near the steam flow meter is connected to the first inlet end of the outlet unit.

[0012] Furthermore, the ammonia water unit includes an ammonia water pipeline, on which an ammonia water manual valve, an ammonia water flow regulating valve, an ammonia water flow meter, and an ammonia water pressure gauge are installed in sequence. The end of the ammonia water pipeline near the ammonia water pressure gauge is connected to the second inlet end of the gas outlet unit.

[0013] Furthermore, the gas outlet unit includes a main gas outlet pipe, one end of which is a first inlet end, and a second inlet end is provided on the side of the main gas outlet pipe located at the bottom of the first inlet end. An ammonia vaporizer drain valve is installed at the other end of the main gas outlet pipe. An ammonia vaporizer outlet thermocouple and an ammonia vaporizer outlet pressure gauge are installed on the main gas outlet pipe in sequence from near to far from the second inlet end. Several gas outlet pipes are also connected to the side of the main gas outlet pipe. The gas outlet unit is connected to the inlet end of the ammonia-air mixed evaporator through the gas outlet pipes.

[0014] Furthermore, the blower heating system includes an air inlet duct, one end of which is connected to an air blower, and the other end of which is connected to the air inlet of an ammonia-air mixed evaporator. A steam heater and an air thermometer are installed sequentially on the air inlet duct from near to far from the air blower.

[0015] Furthermore, the reduction system includes an ammonia main pipe, one end of which is connected to the outlet end of the ammonia-air mixed evaporator. Several ammonia branch pipes are connected to the ammonia main pipe, and several nozzles are installed on each ammonia branch pipe.

[0016] Furthermore, a main pipe thermometer and a main pipe pressure gauge are installed sequentially on the ammonia main pipe from near to far from the ammonia-air mixing evaporator;

[0017] Furthermore, a branch manual valve and a branch flow meter are installed sequentially on the ammonia branch pipe from the nearest to the furthest point from the ammonia main pipe.

[0018] The above technical solution has the following advantages or beneficial effects:

[0019] This invention provides an ammonia injection system for medium- and low-temperature SCR denitrification processes. An ammonia-water vaporization system is added before the ammonia-air mixed evaporator, pre-evaporating the ammonia water. Utilizing the shearing action and rapid heat exchange of the ammonia water droplets during high-speed steam flow, rapid vaporization of the ammonia water is achieved. The ammonia gas after primary vaporization is then fed into the ammonia-air mixed evaporator for secondary vaporization, further ensuring complete vaporization of the ammonia water droplets. The fully vaporized ammonia gas is then introduced into the flue gas duct, effectively preventing nozzle clogging and catalyst surface crystallization, ensuring reliable and stable operation of the medium- and low-temperature SCR denitrification system. During system operation adjustments, if it is necessary to increase or decrease the ammonia injection rate, the high vaporization efficiency and fast vaporization speed of the ammonia-water vaporization system allow for rapid adjustment of the ammonia supply capacity by adjusting the flow rates of ammonia water and steam entering the first-stage ammonia-water vaporization system. The downstream ammonia-air mixed evaporator ensures complete vaporization of any incompletely evaporated droplets in the incoming gas from the first-stage ammonia-water vaporization system, significantly improving denitrification efficiency.

[0020] Furthermore, by working in tandem with the steam unit and the ammonia water unit, the heat source provided by the blower heating system enables rapid vaporization of ammonia water, significantly improving vaporization efficiency and ensuring a stable ammonia supply for the denitrification reaction. The steam unit recovers and utilizes waste heat to reduce energy consumption. The ammonia water unit precisely controls the amount of ammonia injected, reducing ammonia escape and avoiding secondary pollution. The mixing evaporator achieves uniform distribution, adapting to fluctuations in medium and low temperature operating conditions and improving denitrification efficiency.

[0021] Furthermore, the ammonia water flow rate is adjusted according to the on-site denitrification requirements via an ammonia water flow regulating valve and displayed in real time via an ammonia water flow meter. The incoming steam is pressure reduced and stabilized to the working range via a steam pressure reducing and stabilizing valve, and the steam flow rate is adjusted according to the ammonia water flow rate and the outlet temperature and pressure of the ammonia water vaporizer.

[0022] Furthermore, the installation of a drain valve for the ammonia vaporizer facilitates the timely removal of impurities and ensures stable system operation. The installation of thermocouples and pressure gauges at the outlet of the ammonia vaporizer enables real-time and accurate monitoring of temperature and pressure, providing reliable data for process control. Multiple outlet pipes connect to the ammonia-air mixing evaporator, ensuring uniform gas delivery, improving mixing efficiency, and thus enhancing the denitrification effect of the medium- and low-temperature SCR denitrification process, reducing nitrogen oxide emissions, and achieving a balance between environmental protection and efficient production.

[0023] Furthermore, the air blower serves as the power source, continuously and stably supplying air to the system and ensuring the continuity of gas supply; the steam heater effectively heats the incoming air, meeting the specific temperature requirements of the medium- and low-temperature SCR denitrification process and improving reaction efficiency; the air temperature is accurately monitored in real time by an air thermometer, allowing operators to adjust the operating status of the steam heater in a timely manner based on the temperature data, ensuring that the air temperature is always within the optimal range; all components of the entire system work together to provide air of suitable temperature and flow rate to the ammonia-air mixed evaporator, which helps to improve the denitrification effect.

[0024] Furthermore, by installing a head pipe thermometer and a head pipe pressure gauge sequentially on the ammonia head pipe, the temperature and pressure data of the ammonia can be monitored accurately in real time. This helps operators to keep track of the ammonia status in a timely manner, flexibly adjust the system operating parameters based on the data, ensure that the denitrification reaction takes place under suitable conditions, and improve denitrification efficiency and system stability.

[0025] Furthermore, the branch pipe manual valve can flexibly control the on / off of ammonia and coarsely adjust the flow rate, facilitating inspection and maintenance; the branch pipe flow meter can accurately measure the flow rate, providing a basis for fine control. The combination of the two can ensure a stable supply of ammonia, optimize the denitrification reaction, and improve the system's operating efficiency.

[0026] Furthermore, by periodically opening the drain valve of the main pipe, the liquid that has not been fully vaporized and remains inside the ammonia main pipe can be discharged, preventing it from clogging the pipe or affecting the quality of ammonia delivery, ensuring stable system operation, extending equipment lifespan, and reducing maintenance costs. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of an ammonia injection system for medium- and low-temperature SCR denitrification process according to the present invention.

[0028] Figure 2 This is a schematic diagram of the ammonia vaporization system of this utility model;

[0029] In the diagram, 1. Air blower; 2. Steam heater; 3. Ammonia vaporization system; 4. Ammonia-air mixing evaporator; 5. Ammonia main pipe; 6. Ammonia branch pipe; 7. Nozzle; 8. Steam inlet pipe; 9. Ammonia pipe; 10. Outlet pipe; 11. Air thermometer; 12. Steam desuperheating and pressure reducing valve; 13. Steam flow regulating valve; 14. Steam manual valve; 15. Ammonia flow meter; 16. Ammonia manual valve; 17. 18. Ammonia water flow regulating valve; 19. Ammonia water vaporizer outlet thermocouple; 20. Ammonia water vaporizer outlet pressure gauge; 21. Ammonia water vaporizer drain valve; 22. Main pipe thermometer; 23. Main pipe pressure gauge; 24. Branch pipe flow meter; 25. Branch pipe manual valve; 26. Main pipe drain valve; 27. Steam flow meter; 28. Steam thermometer; 29. ​​Steam pressure gauge; 30. Ammonia water pressure gauge; 31. Outlet main pipe; 32. Inlet air pipe. Detailed Implementation

[0030] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this invention. Therefore, the drawings and description are considered exemplary in nature and not restrictive.

[0031] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0032] 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 utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0033] In this utility model, unless otherwise explicitly 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 part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0034] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0035] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0036] This utility model provides an ammonia injection system for medium- and low-temperature SCR denitrification processes, including a blower heating system, an ammonia-air mixing evaporator 4, an ammonia-water vaporization system 3, and a reduction system; the blower heating system includes an air inlet pipe 31, an air blower 1, a steam heater 2, and an air thermometer 11; the ammonia-water vaporization system 3 includes a steam unit, an ammonia-water unit, and an exhaust unit; the steam unit includes a steam inlet pipe 8, a steam manual valve 14, a steam desuperheating and pressure reducing valve 12, a steam flow regulating valve 13, a steam pressure gauge 28, and a steam temperature gauge 29. The ammonia unit includes an ammonia water pipe 9, an ammonia water manual valve 16, an ammonia water flow regulating valve 17, an ammonia water flow meter 15, and an ammonia water pressure gauge 29; the gas outlet unit includes a gas outlet main pipe 30, an ammonia water vaporizer drain valve 20, an ammonia water vaporizer gas outlet thermocouple 18, an ammonia water vaporizer gas outlet pressure gauge 19, and a gas outlet pipe 10; the reduction system includes an ammonia gas main pipe 5, an ammonia gas branch pipe 6, a nozzle 7, a main pipe thermometer 21, a main pipe pressure gauge 22, a branch pipe manual valve 24, a branch pipe flow meter 23, and a main pipe drain valve 25;

[0037] See Figure 1 The blower heating system is connected to the air inlet of the ammonia-air mixed evaporator 4, the ammonia vaporization system 3 is connected to the air inlet of the ammonia-air mixed evaporator 4, and the outlet of the ammonia-air mixed evaporator 4 is connected to the reduction system. The ammonia vaporization system 3 includes a steam unit, an ammonia unit, and an outlet unit. The air inlet of the steam unit is connected to the blower heating system, the outlet of the steam unit is connected to the first inlet of the outlet unit, the liquid outlet of the ammonia unit is connected to the second inlet of the outlet unit, and the outlet of the outlet unit is connected to the air inlet of the ammonia-air mixed evaporator 4. The ammonia water is first vaporized in the ammonia water vaporizer 3 using high-temperature steam. Specifically, a high-speed steam flow is formed in the middle of the pipeline of the ammonia water vaporizer 3. The high-temperature and high-speed steam is used to shear the ammonia water into droplets, thereby achieving rapid vaporization of the ammonia water. Then, it is introduced into the ammonia-air mixed evaporator 4 for secondary vaporization using heated air, so that the ammonia water droplets are further fully vaporized. The fully vaporized ammonia gas is introduced into the flue gas pipeline.

[0038] See Figure 2A steam manual valve 14, a steam desuperheating and pressure reducing valve 12, a steam flow regulating valve 13, a steam pressure gauge 28, a steam thermometer 27, and a steam flow meter 26 are sequentially installed on the steam inlet pipe 8 of the steam unit. The steam desuperheating and pressure reducing valve 12 is located before the steam flow regulating valve 13 and is used to stabilize the incoming steam pressure within the working range. The steam flow regulating valve 13 can adjust the ratio of steam flow to ammonia flow entering the ammonia vaporization system 3 according to the outlet temperature of the ammonia vaporization system 3. The ratio range of steam flow to ammonia flow is (2~20):1. The steam manual valve 14 is used to manually close the steam inlet pipe 8 to block the steam inflow when the steam flow regulating valve 13 fails. The steam inlet pipe 8 is located near... One end of the steam flow meter 26 is connected to the first inlet end of the gas outlet unit; an ammonia water manual valve 16, an ammonia water flow regulating valve 17, an ammonia water flow meter 15, and an ammonia water pressure gauge 29 are sequentially installed on the ammonia water pipeline 9 of the ammonia water unit. The ammonia water flow meter 15 is used to measure the ammonia water flow in real time. When the ammonia water flow regulating valve 17 fails, the ammonia water pipeline 9 can be manually closed through the ammonia water manual valve 16 to block the ammonia water inflow; the end of the ammonia water pipeline 9 near the ammonia water pressure gauge 29 is connected to the second inlet end of the gas outlet unit; one end of the gas outlet main pipe 30 of the gas outlet unit is the first inlet end, and the second inlet end is set on the side of the gas outlet main pipe 30 located at the bottom of the first inlet end. The other end of the gas outlet main pipe 30 is equipped with an ammonia water vaporizer drain valve 20. A thermocouple 18 for the ammonia vaporizer outlet and a pressure gauge 19 for the ammonia vaporizer outlet are installed sequentially from the closest to the second inlet end on the main gas pipe 30. These thermocouples and pressure gauges are used to monitor the vaporization effect of the ammonia vaporizer in real time. Several outlet pipes 10 are also connected to the side of the main gas pipe 30. The outlet unit is connected to the inlet end of the ammonia-air mixed evaporator 4 through the outlet pipes 10. The air inlet pipe 31 of the blower heating system has an air blower 1 connected to one end and the other end connected to the inlet end of the ammonia-air mixed evaporator 4. A steam heater 2 and an air thermometer are installed sequentially from the closest to the air blower 1 on the air inlet pipe 31. 11. Air thermometer 11 can measure the air temperature blown into ammonia-air mixed evaporator 4 in real time; one end of the ammonia main pipe 5 of the reduction system is connected to the outlet end of ammonia-air mixed evaporator 4, and the other end of the ammonia main pipe 5 is equipped with a main pipe drain valve 25, which is opened periodically to discharge the liquid that is not completely vaporized inside the ammonia water vaporization system 3 and remains inside the ammonia main pipe 5; several ammonia branch pipes 6 are connected to the ammonia main pipe 5, and several nozzles 7 are installed on each ammonia branch pipe 6; a main pipe thermometer 21 and a main pipe pressure gauge 22 are installed on the ammonia main pipe 5 from near to far from ammonia-air mixed evaporator 4, and the main pipe pressure gauge 22 can measure the pressure of the ammonia-air mixed gas blown into the ammonia main pipe 5 in real time;A manual valve 24 and a flow meter 23 are installed sequentially on the ammonia branch pipe 6 from the closest to the ammonia main pipe 5 to the furthest away from the branch pipe. The ammonia flow rate in each branch pipe is adjusted to achieve full mixing of ammonia and flue gas.

[0039] Specifically, the ammonia-air mixing evaporator 4 is used to mix ammonia gas with hot air to perform secondary evaporation of ammonia droplets in the incoming gas of the ammonia-water vaporization system 3, ensuring that the ammonia water can be fully vaporized. The ammonia-air mixing evaporator 4 includes an ammonia-air mixing tank, which is provided with an air inlet end, an air outlet end, and an outlet end. The outlet end is located at the top of the ammonia-air mixing tank, and a manual valve is also installed at the bottom of the ammonia-air mixing tank.

[0040] Preferably, the number of air inlet and air outlet pipes 10 can be 2, 3, 4, 5, 6, 7 and 8, or other feasible numbers;

[0041] Preferably, the number of ammonia branch pipes 6 can be 2, 3, 4, 5, 6, 7, or 8, or other feasible numbers;

[0042] Preferably, the area from the outlet of the steam heater 2 to the ammonia branch pipe 6 is covered with an insulation layer to reduce the heat loss of the ammonia.

[0043] Preferably, the air blower 1 is a variable frequency blower, which can adjust the frequency to control the air flow according to the actual needs on site. When the working conditions change and the ammonia flow needs to be adjusted quickly, the blower frequency can be quickly changed to change the blown air flow, thereby stabilizing the pressure and temperature of the mixed gas at the outlet of the ammonia-air mixed evaporator 4.

[0044] Preferably, the heating temperature of the blower heating system is 120℃~180℃;

[0045] Preferably, the heating temperature of the blower heating system can be 120℃, 130℃, 140℃, 150℃, 160℃, 170℃ and 180℃, or any temperature between 120℃ and 180℃.

[0046] Preferably, electric heating or steam heating methods can be selected according to the actual needs on site;

[0047] Preferably, the angle between the steam inlet pipe 8 and the ammonia water pipe 9 and the main outlet pipe 30 is 90°.

[0048] This utility model provides an ammonia injection system for medium- and low-temperature SCR denitrification processes. The ammonia flow rate is adjusted according to the on-site denitrification requirements via an ammonia flow regulating valve 17 and displayed in real time via an ammonia flow meter 15. The incoming steam is pressure-reduced and stabilized to the working range via a steam pressure-reducing and stabilizing valve 12. The steam flow rate is adjusted based on the ammonia flow rate and the outlet temperature and pressure of the ammonia vaporization system 3. Within the ammonia vaporization system 3, the ammonia is rapidly vaporized by the shearing effect and rapid heat exchange of the ammonia droplets during high-speed steam flow, and then introduced into an ammonia-air mixed evaporator. Secondary evaporation is carried out within 4. Air blower 1 blows air into steam heater 2, and the heated air is then introduced into the lower end of ammonia-air mixed evaporator 4 to further mix with the ammonia gas after primary vaporization and perform secondary vaporization, increasing the heat exchange time and ensuring that the ammonia water can be fully vaporized. Then, the mixed gas is introduced into ammonia main pipe 5. Multiple ammonia branch pipes 6 are branched from ammonia main pipe 5. The manual valves 24 on the branch pipes 6 are adjusted according to the flue gas flow field on site to control the ammonia flow rate of each ammonia branch pipe 6, so as to achieve full and uniform mixing of ammonia gas and nitrogen oxides in flue gas.

[0049] The structure and working principle of this utility model will be further explained below:

[0050] The purpose of this utility model is to provide an ammonia injection system for medium and low temperature SCR denitrification process. When using the device, the air blower 1 blows air into the steam heater 2, and then the heated air is introduced into the air inlet below the ammonia-air mixed evaporator 4, where it mixes with the ammonia gas flowing from the ammonia water vaporizer 3. The ammonia gas is connected to the ammonia gas main pipe 5 at the upper end of the ammonia-air mixed evaporator 4, and after being split at the ammonia gas main pipe 5, it enters each branch pipe 6. It is then sprayed into the flue gas through the nozzles 7 on the branch pipes 6. In the ammonia water vaporization system 3, ammonia water is introduced from the upper end of the ammonia water vaporization system 3, and high temperature steam is introduced in the middle of the ammonia water vaporization system 3. The high temperature steam is used to perform primary vaporization of the ammonia water. The mixed gas after the initial vaporization is introduced into the ammonia-air mixed evaporator 4 through the gas outlet pipe 10 at the lower end of the ammonia water vaporization system 3 for further vaporization, and then the mixed gas is led to the next stage through the mixed evaporator 4.

[0051] Specifically, the ammonia water flow rate is adjusted according to the denitrification requirements via the ammonia water flow regulating valve 17 and displayed in real time via the ammonia water flow meter 15. The steam pressure reducing and stabilizing valve 12 regulates the incoming steam pressure to stabilize it within the working range. The steam flow rate is adjusted according to the ammonia water flow rate. The ammonia water is evaporated using steam in the ammonia water vaporizer 3. Then, the ammonia gas after the first evaporation is introduced into the ammonia-air mixing evaporator 4. In the ammonia-air mixing evaporator 4, it is mixed with hot air for secondary vaporization to ensure that the ammonia water is fully evaporated. Then, it is injected into the flue gas upstream of the SCR denitrification reaction tower through the ammonia injection grid.

[0052] When starting the system, the air blower 1 and steam heater 2 should be turned on first to preheat the ammonia-air mixed evaporator 4. When the gas temperature at the outlet ammonia header 5 of the ammonia-air mixed evaporator 4 reaches 200℃, steam is then introduced into the ammonia vaporization system 3. When the gas temperature at the outlet pipe 10 of the ammonia vaporization system 3 reaches 150℃, ammonia water is then introduced. The ammonia water flow rate is adjusted through the ammonia water flow regulating valve 17 according to the denitrification requirements. The steam flow rate is also adjusted through the steam flow regulating valve 13 according to the outlet temperature and pressure of the ammonia vaporization system 3 to ensure that the ammonia water evaporates as completely as possible in the ammonia water vaporizer 3.

[0053] After primary vaporization via the ammonia-water vaporization system 3, the ammonia gas is introduced into the ammonia-air mixed evaporator 4 for secondary vaporization. The fully vaporized ammonia gas is then introduced from the upper end of the ammonia-air mixed evaporator 4 into the ammonia main pipe 5, and then further distributed through four branch pipes 6. The manual regulating valves 24 on each branch pipe 6 adjust their opening according to the flue gas velocity at the ammonia injection grid section and the distribution of nitrogen oxide concentration in the flue gas, to ensure that the injected ammonia gas is fully mixed with the nitrogen oxides in the flue gas.

[0054] When the ammonia injection rate needs to be adjusted according to the denitrification requirements, the ammonia water flow rate needs to be adjusted. For example, if the ammonia water flow rate is increased from 10L / h to 20L / h, the adjustment process is as follows: Adjust the ammonia water flow rate regulating valve 17 to adjust the ammonia water flow rate to reach 20L / h. Adjust the steam flow rate regulating valve 13 according to the outlet temperature and pressure of the ammonia water vaporization system 3. Adjust the air blower 1 according to the gas temperature and pressure at the outlet of the ammonia-air mixed evaporator 4 to stabilize the ammonia gas temperature and pressure entering the ammonia gas header 5 within the working range.

[0055] If the ammonia flow rate is reduced from 10L / h to 5L / h, the adjustment process is as follows: Adjust the ammonia flow rate by adjusting the ammonia flow rate regulating valve 17 to reduce the ammonia flow rate to 5L / h; adjust the steam flow rate by adjusting the steam flow rate regulating valve 13 according to the outlet temperature and pressure of the ammonia vaporizer 3; and adjust the air blower 1 according to the gas temperature and pressure at the outlet of the ammonia-air mixed evaporator 4 to stabilize the ammonia temperature and pressure entering the ammonia main pipe 5 within the working range.

[0056] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. It will be apparent to those skilled in the art that this utility model is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or basic characteristics of this utility model. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this utility model is defined by the appended claims rather than the foregoing description, and thus all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this utility model. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0057] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of this utility model and should not be used to limit the scope of protection of this utility model. Any modifications made to the technical solutions based on the technical concept proposed by this utility model shall fall within the scope of protection of the claims of this utility model.

Claims

1. An ammonia injection system for medium- and low-temperature SCR denitrification processes, characterized in that, It includes a blower heating system, an ammonia-air mixed evaporator (4), an ammonia-water vaporization system (3), and a reduction system; The blower heating system is connected to the air inlet of the ammonia-air mixed evaporator (4), the ammonia-water vaporization system (3) is connected to the air inlet of the ammonia-air mixed evaporator (4), and the outlet of the ammonia-air mixed evaporator (4) is connected to the reduction system.

2. The ammonia injection system for medium- and low-temperature SCR denitrification process according to claim 1, characterized in that, The ammonia vaporization system (3) includes a steam unit, an ammonia unit and an exhaust unit. The inlet of the steam unit is connected to the blower heating system, the outlet of the steam unit is connected to the first inlet of the exhaust unit, the outlet of the ammonia unit is connected to the second inlet of the exhaust unit, and the outlet of the exhaust unit is connected to the inlet of the ammonia-air mixed evaporator (4).

3. An ammonia injection system for medium- and low-temperature SCR denitrification process according to claim 2, characterized in that, The steam unit includes a steam inlet pipe (8), on which a steam manual valve (14), a steam desuperheating and pressure reducing valve (12), a steam flow regulating valve (13), a steam pressure gauge (28), a steam thermometer (27), and a steam flow meter (26) are installed in sequence. The end of the steam inlet pipe (8) near the steam flow meter (26) is connected to the first inlet end of the outlet unit.

4. An ammonia injection system for medium- and low-temperature SCR denitrification process according to claim 2, characterized in that, The ammonia water unit includes an ammonia water pipeline (9), on which an ammonia water manual valve (16), an ammonia water flow regulating valve (17), an ammonia water flow meter (15), and an ammonia water pressure gauge (29) are installed in sequence. The end of the ammonia water pipeline (9) near the ammonia water pressure gauge (29) is connected to the second inlet end of the gas outlet unit.

5. An ammonia injection system for medium- and low-temperature SCR denitrification process according to claim 2, characterized in that, The gas outlet unit includes a gas outlet main pipe (30), one end of which is a first inlet end. A second inlet end is provided on the side of the gas outlet main pipe (30) located at the bottom of the first inlet end. An ammonia vaporizer drain valve (20) is installed on the other end of the gas outlet main pipe (30). An ammonia vaporizer outlet thermocouple (18) and an ammonia vaporizer outlet pressure gauge (19) are installed on the gas outlet main pipe (30) from near to far from the second inlet end. Several gas outlet pipes (10) are also connected to the side of the gas outlet main pipe (30). The gas outlet unit is connected to the inlet end of the ammonia-air mixed evaporator (4) through the gas outlet pipes (10).

6. An ammonia injection system for medium- and low-temperature SCR denitrification process according to claim 1, characterized in that, The blower heating system includes an air inlet pipe (31), one end of which is connected to an air blower (1), and the other end of which is connected to the air inlet of an ammonia-air mixed evaporator (4). A steam heater (2) and an air thermometer (11) are installed on the air inlet pipe (31) from near to far from the air blower (1).

7. An ammonia injection system for medium- and low-temperature SCR denitrification process according to claim 1, characterized in that, The reduction system includes an ammonia main pipe (5), one end of which is connected to the outlet end of an ammonia-air mixed evaporator (4). Several ammonia branch pipes (6) are connected to the ammonia main pipe (5), and several nozzles (7) are installed on each ammonia branch pipe (6).

8. An ammonia injection system for medium- and low-temperature SCR denitrification process according to claim 7, characterized in that, A main pipe thermometer (21) and a main pipe pressure gauge (22) are installed sequentially from the nearest to the ammonia-air mixing evaporator (4) on the ammonia main pipe (5).

9. An ammonia injection system for medium- and low-temperature SCR denitrification process according to claim 7, characterized in that, The ammonia branch pipe (6) is equipped with a branch pipe manual valve (24) and a branch pipe flow meter (23) in sequence from the nearest to the furthest from the ammonia main pipe (5).

10. An ammonia injection system for medium- and low-temperature SCR denitrification process according to claim 7, characterized in that, The other end of the ammonia main pipe (5) is equipped with a main pipe drain valve (25).

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