Anti-blocking structure of mixer in denitration process

Abstract

This utility model relates to the field of denitrification technology, specifically to a mixer anti-clogging structure in a denitrification process. It reduces equipment investment and maintenance costs and prevents clogging that could affect the normal operation of the denitrification system. The structure includes an ammonia injection grid connected to an ammonia-air mixer, which is connected to a gaseous ammonia delivery pipe and a dilution air delivery pipe. The ammonia-air mixer is characterized by having two parallel ammonia-air mixers forming two mixing pipelines. Each ammonia-air mixer has a regulating valve at both ends. One end of the dilution powder delivery pipe is connected to a primary air fan, and the other end is connected to one end of each of the two mixing pipelines. The other ends of the two mixing pipelines are connected to the ammonia injection grid. A purge pipe is provided at the outlet of each of the two ammonia-air mixers.

Description

Technical Field

[0001] This utility model relates to the field of denitrification technology, specifically to a mixer anti-clogging structure in a denitrification process. Background Technology

[0002] In the SCR denitrification process, liquid ammonia serves as one of the reducing media. It is heated into ammonia gas in an evaporator, then mixed with dilution air to form a gas mixture with an ammonia volume content of 5%, which is then fed into the flue gas system. Conventional SCR denitrification processes using liquid ammonia as the reducing media involve using a room-temperature dilution fan to deliver air to an ammonia-air mixer, where it is mixed and diluted with gaseous ammonia. The mixture is then sent to an ammonia injection grid, where it is injected into the flue gas to fully mix with the nitrogen oxides in the flue gas. Under the action of a catalyst, NOx in the flue gas is converted into N2 and H2O.

[0003] Denitrification using ammonia or urea as the reducing medium requires additional equipment and operating costs. After ammonia or urea is converted into gaseous ammonia, the dilution air temperature is critical. For example, the dilution air temperature required for the hydrolysis of urea to produce gaseous ammonia is around 150°C. Therefore, drawing primary cold air (room temperature air) as the dilution air necessitates the addition of heat exchangers, temperature measuring instruments, and other equipment, thereby increasing equipment and operating / maintenance costs. Summary of the Invention

[0004] To address the aforementioned technical problems, this utility model provides a mixer anti-clogging structure for denitrification processes, which can reduce equipment investment and maintenance costs and prevent clogging problems from affecting the normal operation of the denitrification system.

[0005] The technical solution is as follows: a mixer anti-clogging structure in a denitrification process, comprising an ammonia injection grid, the ammonia injection grid being connected to an ammonia-air mixer, the ammonia-air mixer being connected to a gaseous ammonia delivery pipe and a dilution air delivery pipe, characterized in that two ammonia-air mixers are arranged in parallel to form two mixing pipelines, each ammonia-air mixer having a regulating valve at both ends, one end of the dilution powder delivery pipe being connected to a primary air fan and the other end being connected to one end of the two mixing pipelines, the other end of the two mixing pipelines being connected to the ammonia injection grid, and each of the two ammonia-air mixers having a purge pipe at its outlet end.

[0006] A further feature is that the purge pipe extends vertically into the mixing pipeline and its end is an elbow facing the outlet end of the ammonia-air mixer; the purge pipe is equipped with a ball valve and connected to a compressed air source.

[0007] The two ends of the ammonia-air mixer are connected to the mixing pipeline by flanges.

[0008] The dilution air delivery pipe is equipped with valves, flow meters, and pressure gauges.

[0009] By adopting this utility model, the dilution air delivery pipe is directly connected to the boiler primary air fan, drawing cold air from the primary cold air duct. This reduces the equipment cost and maintenance cost of the dilution fan, and eliminates the need to consider the size and location of the fan space. Furthermore, two ammonia-air mixers are installed, forming a main and auxiliary structure. If one is blocked, the system can be switched, and purging is performed using a purge pipe. This reduces the number of boiler start-ups and shutdowns, as well as the denitrification operation and maintenance costs, ensuring the normal and stable operation of the denitrification system. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the system of this utility model;

[0011] Figure 2 This is a schematic diagram of the ammonia-air mixer arrangement in this utility model. Detailed Implementation

[0012] See Figure 1 , Figure 2 As shown, a mixer anti-clogging structure in a denitrification process includes an ammonia injection grid 1, which is connected to an ammonia-air mixer 2. The ammonia-air mixer 2 is connected to a gaseous ammonia delivery pipe 3 and a dilution air delivery pipe 4. Two ammonia-air mixers 2 are connected in parallel to form two mixing pipelines 5. Each ammonia-air mixer 2 has a regulating valve 6 at both ends, which can realize the opening or closing of a single mixing pipeline 5. One end of the dilution air delivery pipe 4 is connected to a primary air fan, and the other end is connected to one end of the two mixing pipelines 5. The other end of the two mixing pipelines 5 is connected to the ammonia injection grid 1. The outlet ends of the two ammonia-air mixers 2 are respectively provided with purge pipes 7. The purge pipes 7 extend vertically into the mixing pipelines 5 and the end is an elbow facing the outlet end of the ammonia-air mixer 2. The purge pipes 7 are provided with ball valves 8 and connected to a compressed air source.

[0013] The ammonia-air mixer 2 is connected to the mixing pipeline 5 at both ends by flange structure 9, which can be disassembled and replaced; the dilution air delivery pipe 4 is equipped with valve 10, flow meter 11 and pressure gauge 12. 13 in the figure is the control valve on the ammonia gas delivery pipe 3.

[0014] In this application, gaseous ammonia is used as the reducing medium. Primary air from the primary air blower is directly extracted as dilution air. The primary air pressure and volume are calculated to meet the requirements of the denitrification process, and the impact of extraction on the boiler's primary air is minimal and negligible. This dilution air is connected to an ammonia-air mixer 2 via a valve pipeline. Simultaneously, the airflow can be adjusted by controlling the opening of valve 10 according to flow meter 11 and pressure gauge 12 to meet the denitrification requirements under the corresponding boiler load. Compared to conventional processes, this reduces the equipment cost and maintenance costs of the dilution blower, and eliminates the need to consider the size and location of the blower. Because two ammonia-air mixers 2 are installed, if the mixing effect of the active ammonia-air mixer 2 is poor, or if blockage occurs, reducing the airflow and affecting the denitrification effect, the system can switch to the other ammonia-air mixer using a regulating valve without affecting the current denitrification operation. After switching, the clogged ammonia-air mixer 2 can be cleared. When the air volume is initially reduced and the blockage is not severe, the ball valve 8 can be opened to purge the inside of the ammonia-air mixer 2 with compressed air. After purging for a period of time, the regulating valve 6 at the inlet end of the ammonia-air mixer 2 can be disassembled and the valve can be cleaned. When the air volume is significantly reduced and the blockage is severe, the ammonia-air mixer 2 can be disassembled as a whole for deep cleaning or the internal mixing packing can be replaced before it can be reinstalled in the mixing pipeline 5 to restore normal operation. This solves the problem that in the past, when a single mixer was blocked, it was impossible to clean and purge it under normal denitrification operation conditions, thereby reducing the number of boiler start-ups and shutdowns and the denitrification operation and maintenance costs, and ensuring the normal and stable operation of the denitrification system.

Claims

1. A mixer anti-clogging structure in a denitrification process, comprising an ammonia injection grid, the ammonia injection grid being connected to an ammonia-air mixer, the ammonia-air mixer being connected to a gaseous ammonia delivery pipe and a dilution air delivery pipe, characterized in that, Two ammonia-air mixers are connected in parallel to form two mixing pipelines. Each ammonia-air mixer is equipped with a regulating valve at both ends. One end of the dilution air delivery pipe is connected to the primary air fan, and the other end is connected to one end of the two mixing pipelines. The other ends of the two mixing pipelines are connected to the ammonia injection grid. The outlet ends of the two ammonia-air mixers are respectively equipped with purge pipes.

2. The anti-clogging structure for a mixer in a denitrification process according to claim 1, characterized in that, The purge pipe extends vertically into the mixing pipeline and has an elbow at its end facing the outlet of the ammonia-air mixer. The purge pipe is equipped with a ball valve and connected to a compressed air source.

3. The anti-clogging structure for a mixer in a denitrification process according to claim 1, characterized in that, The ammonia-air mixer is connected to the mixing pipeline at both ends by flanges.

4. The anti-clogging structure for a mixer in a denitrification process according to claim 1, characterized in that, The dilution air delivery pipe is equipped with valves, flow meters, and pressure gauges.

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