A method and system for treating exhaust gas from an ammoxidation reaction

Abstract

The application discloses an ammonia oxidation reaction waste gas treatment method and system, and the treatment system comprises a water absorption tower, a deamination tower, a direct combustion furnace, a waste heat steam boiler, a preheating heat exchanger, a denitration reactor and a tail gas heat exchanger. The treatment method comprises the following steps: absorbing ammonia gas in waste gas through the water absorption tower, reducing the ammonia concentration of waste gas entering the direct combustion furnace and reducing the dilution air consumption of the direct combustion furnace; absorbing liquid enters the deamination tower to desorb ammonia gas, and the ammonia gas is injected into the direct combustion furnace as fuel gas; high-temperature waste gas firstly passes through the waste heat steam boiler to produce by-product steam, and then enters the preheating heat exchanger to preheat the inlet waste gas of the direct combustion furnace; the waste gas after heat exchange enters the denitration reactor to carry out a denitration reaction; the treated waste gas passes through the tail gas heat exchanger and the circulating water heat exchanger, and then enters the water spray tower to remove a small amount of smoke dust and is discharged; the application effectively reduces the dilution combustion-supporting air supplement and the natural gas consumption, can reduce the treatment waste gas amount of the direct combustion furnace and the denitration reactor, and effectively reduces the equipment investment and the operation energy consumption.

Description

Technical Field

[0001] This invention relates to the field of waste gas treatment technology, and in particular to a method and system for treating waste gas from ammonia oxidation reaction. Background Technology

[0002] The ammoxidation of m-xylene is currently the mainstream industrial process for producing isophthalonitrile. In this process, m-xylene, ammonia, and air are mixed in precise molar ratios and then introduced into a fluidized bed reactor packed with a specialized catalyst. Under preset temperature, pressure, and other process conditions, the ammoxidation reaction occurs, ultimately producing the target product, isophthalonitrile, while simultaneously generating water, nitrogen, and various byproducts. Because a large excess of ammonia is required during the reaction to ensure the full conversion of m-xylene and improve the yield of the target product, the production system inevitably emits high-ammonia-containing industrial waste gas. Furthermore, the waste gas also contains other polluting gases such as carbon monoxide and hydrogen cyanide, as well as volatile organic compounds, primarily m-xylene and benzonitrile, making its treatment extremely difficult.

[0003] Currently, the mainstream industrial treatment technologies for high-ammonia-content waste gas generated by ammonia oxidation processes mainly include absorption, regenerative thermal combustion, and catalytic combustion. Absorption is affected by factors such as the diverse types of pollutants in the waste gas and the mutual interference between components. Even after treatment by absorption alone, the concentrations of pollutants such as ammonia and volatile organic compounds still cannot meet the relevant national emission standards, making direct discharge impossible. Further coupling the waste gas treated by absorption with advanced treatment processes such as regenerative thermal combustion or catalytic combustion not only significantly increases the system's energy consumption costs but also requires the purchase of additional make-up air equipment for pipeline modifications and the incurring costs of system commissioning, resulting in high waste gas treatment and maintenance costs. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method and system for treating ammonia oxidation reaction waste gas.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for treating ammonia oxidation reaction waste gas, comprising: The waste gas generated by the isophthalonitrile process is collected and passed into a water absorption tower to absorb ammonia. The absorbed waste gas then enters the mixing box after passing through the first flame arrester. The exhaust gas entering the mixing box is supplemented with dilution combustion air to reduce its concentration. The mixed exhaust gas is preheated by a booster fan and then sent into the direct-fired furnace. The absorbent generated by the water absorption tower enters the deammoniation tower and passes through the internal reflux condenser and forced circulation reboiler to desorb ammonia. The desorbed ammonia passes through the desorption gas blower and the second flame arrester and enters the direct-fired furnace for combustion and heat generation. The desorbed wastewater is returned to the water absorption tower to absorb ammonia. The waste gas mixed in the mixing box and the ammonia desorbed from the deammoniation tower are combusted in a direct-fired furnace. Natural gas is supplemented at the gas supply end through a third flame arrester. The combusted waste gas is sent to a waste heat steam boiler for heat exchange to generate by-product steam. The by-product steam generated by the waste heat steam boiler is incorporated into the external steam pipeline network. The waste gas after heat exchange enters the preheating heat exchanger to preheat the waste gas mixed in the mixing box. The cooled waste gas enters the denitrification reactor and mixes with the injected ammonia gas to carry out the denitrification reaction. The exhaust gas after the denitrification reactor reaction enters the tail gas heat exchanger to preheat the exhaust gas mixed in the mixing box. The cooled exhaust gas enters the circulating water heat exchanger. The exhaust gas after heat exchange enters the water spray tower through the induced draft fan to remove dust. The dust-removed exhaust gas is then discharged through the chimney.

[0006] In a second aspect, the present invention also provides an ammonia oxidation reaction waste gas treatment system for operating the ammonia oxidation reaction waste gas treatment method as described in the first aspect, the treatment system comprising: The water absorption tower, connected to the ammonia removal tower and the tail gas heat exchanger, is used to absorb waste gas; Ammonia removal tower, including a first ammonia removal tower and / or a second ammonia removal tower, is connected to a desorption gas blower and is used to desorb waste gas; A direct-fired furnace, connected to an ammonia removal tower, is used to burn waste gas; Waste heat steam boiler, connected to a direct-fired furnace, is used to produce waste heat steam; A preheating heat exchanger, connected to a waste heat steam boiler, is used to preheat waste gas; The denitrification reactor, connected to a preheating heat exchanger, is used for catalytic denitrification reaction; The exhaust gas heat exchanger is connected to the denitrification reactor and the water absorption tower to exchange heat with the exhaust gas.

[0007] In some embodiments, the ammonia removal tower is connected to a water absorption tower and a desorption gas blower; A mixing box is installed on the pipeline connecting the water absorption tower and the exhaust gas heat exchanger, and a first flame arrester is installed on the pipeline connecting the water absorption tower and the mixing box. The mixing box is connected to the fresh air fan. A second flame arrester is installed on the pipeline connecting the desorption gas fan and the direct-fired furnace. The direct-fired furnace is connected to the third flame arrester and the exhaust gas booster fan. The preheating heat exchanger is connected to the exhaust gas booster fan, and the tail gas heat exchanger is connected to the exhaust gas booster fan. The exhaust gas heat exchanger is connected to the circulating water heat exchanger, the circulating water heat exchanger is connected to the induced draft fan, the induced draft fan is connected to the water spray tower, and the water spray tower is connected to the chimney.

[0008] In some embodiments, the packing material in the water absorption tower is selected from one or more of corrugated packing, grid packing, wire mesh packing, Pall rings, conjugate rings, cross rings and θ mesh rings; preferably, the packing material in the water absorption tower is selected from one or more of corrugated packing, grid packing and wire mesh packing.

[0009] In some embodiments, the water absorption tower has 25 to 150 trays, a top temperature of 20 to 50°C, a bottom temperature of 30 to 60°C, and a top pressure of 2 to 10 kPaG; preferably, the water absorption tower has 40 to 100 trays, a top temperature of 20 to 35°C, a bottom temperature of 30 to 45°C, and a top pressure of 2 to 5 kPaG.

[0010] In some embodiments, the deammoniation tower includes a first deammoniation tower and / or a second deammoniation tower, wherein the first deammoniation tower is connected to the second deammoniation tower, and the second deammoniation tower is connected to a desorption gas blower and a water absorption tower.

[0011] In some embodiments, the first and second deammoniation towers are selected from any one of bubble cap trays, sieve trays, and solid valve trays; preferably, the first and second deammoniation towers are selected from solid valve trays. The first and second deammoniation towers are equipped with internal reflux condensers and forced circulation reboilers.

[0012] In some embodiments, the top pressure of the first ammonia removal tower is 1-20 kPaG, the top temperature of the first ammonia removal tower is 60-80°C, and the bottom temperature of the first ammonia removal tower is 100-106°C; preferably, the top pressure of the first ammonia removal tower is 1-10 kPaG, the top temperature of the first ammonia removal tower is 65-75°C, and the bottom temperature of the first ammonia removal tower is 100-103°C.

[0013] In some embodiments, the top pressure of the second ammonia removal tower is 1-20 kPaG, the top temperature of the second ammonia removal tower is 60-80°C, and the bottom temperature of the second ammonia removal tower is 70-90°C; preferably, the top pressure of the second ammonia removal tower is 1-10 kPaG, the top temperature of the second ammonia removal tower is 65-75°C, and the bottom temperature of the second ammonia removal tower is 70-80°C.

[0014] In some embodiments, the ratio of the amount of water absorbing waste gas entering the mixing box to the amount of diluted combustion-supporting fresh air is any one of 1:1, 1:0.9, 1:0.8, 1:0.7 and 1:0.6. Preferably, the ratio of the amount of water absorbing waste gas entering the mixing box to the amount of diluted combustion-supporting fresh air is any one of 1:0.8 and 1:0.7.

[0015] In some embodiments, the direct-fired furnace is equipped with an integrated burner, and the integrated burner is provided in 2-8 groups, preferably 4 groups; the residence time of the exhaust gas in the direct-fired furnace is any one of 4s, 5s and 6s, preferably 5s; each group of integrated burners includes a mixed air exhaust gas spray gun, a desorbed ammonia spray gun and a natural gas spray gun, and the combustion temperature inside the direct-fired furnace is 900-1100℃.

[0016] In some embodiments, the waste heat steam boiler is equipped with a deaerator, a boiler feed water pump, a steam boiler, and a periodic blowdown expansion tank; the denitrification reactor is equipped with an ammonia water storage tank and a metering pump for controlling the ammonia water flow rate; the denitrification catalyst inside the denitrification reactor consists of 2 to 4 layers; and the denitrification temperature of the denitrification reactor is 300 to 400°C.

[0017] The present invention has the following beneficial effects: 1. This invention uses a water absorption tower to absorb ammonia from waste gas, reducing the ammonia concentration in the waste gas entering the direct-fired furnace and reducing the amount of dilution air used in the furnace. The absorbent from the water absorption tower enters a deammoniation tower to desorb ammonia, which can be injected into the direct-fired furnace as fuel gas for treatment, thereby reducing natural gas consumption and overall energy consumption. The high-temperature waste gas after treatment in the direct-fired furnace first passes through a waste heat steam boiler to produce by-product steam, and then enters a preheating heat exchanger to preheat the waste gas at the inlet of the direct-fired furnace. The waste gas after heat exchange then enters a denitrification reactor for denitrification reaction. After treatment in the denitrification reactor, the waste gas passes through a tail gas heat exchanger and a circulating water heat exchanger for heat exchange before entering a water spray tower to remove a small amount of soot, and finally passes through a chimney to meet emission standards. 2. In this invention, the treatment system uses desorbed ammonia as fuel gas for the direct-fired furnace due to the small dilution air volume. This reduces the amount of dilution combustion air supplement and natural gas consumption. Under the same waste gas treatment volume, the equipment size in the treatment system can be significantly reduced, and the amount of waste gas treated by the direct-fired furnace and denitrification reactor can be reduced, effectively reducing equipment investment and operating energy consumption. Furthermore, using desorbed ammonia as fuel gas for the TO furnace can reduce natural gas consumption. At the same time, the operating conditions of this treatment system are easy to control, and the pollutant removal efficiency is high. Attached Figure Description

[0018] Figure 1 The flowchart shows the processing method and processing system proposed in this invention. Figure 2 This is a simplified process flow diagram of the processing method and system described in Embodiment 1 of the present invention; Legend: 1. Exhaust gas booster fan; 2. Direct-fired furnace; 3. Waste heat steam boiler; 4. Preheating heat exchanger; 5. Denitrification reactor; 6. Third flame arrester; 7. Second flame arrester; 8. Fresh air fan; 9. Mixing box; 10. Tail gas heat exchanger; 11. Desorption gas fan; 12. First flame arrester; 13. Second ammonia removal tower; 14. First ammonia removal tower; 15. Water absorption tower; 16. Exhaust fan; 17. Circulating water heat exchanger; 18. Water spray tower; 19. Chimney. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This application provides a method and system for treating ammonia oxidation reaction waste gas, solving the problems of existing technologies where absorption methods are affected by factors such as the diverse types of pollutants in the waste gas and the mutual interference between components. Even after treatment by absorption alone, the concentrations of pollutants such as ammonia and volatile organic compounds in the waste gas still fail to meet relevant national emission standards, making direct discharge impossible. Further coupling the waste gas treated by absorption with regenerative thermal combustion or catalytic combustion processes significantly increases the system's energy consumption costs, requires additional purchase of make-up air equipment and pipeline modifications, and incurs system commissioning costs, resulting in high waste gas treatment and maintenance costs. This application effectively reduces the amount of dilution combustion air and natural gas used, thereby reducing the amount of waste gas treated by the direct-fired furnace and denitrification reactor, effectively lowering equipment investment and operating energy consumption.

[0021] Please refer to the following examples for details: Reference Figure 1 An embodiment of the ammonia oxidation reaction waste gas treatment method provided by the present invention includes: The waste gas from the isophthalonitrile process is collected and fed into the water absorption tower 15 to absorb ammonia. The absorbed waste gas then enters the mixing box 9 after passing through the first flame arrester 12. The absorbed wastewater is then collected. The exhaust gas entering the mixing box 9 is diluted with combustion air by the fresh air fan 8 to reduce its concentration. The mixed exhaust gas is preheated by the booster fan and then sent to the direct-fired furnace 2. The absorbent generated by the water absorption tower 15 enters the ammonia removal tower and passes through the internal reflux condenser and forced circulation reboiler to desorb ammonia. The desorbed ammonia passes through the desorption gas blower 11 and the second flame arrester 7 and enters the direct-fired furnace 2 for combustion and heat generation. The desorbed wastewater is returned to the water absorption tower 15 to absorb ammonia. The waste gas mixed in the mixing box 9 and the ammonia gas desorbed from the deammoniation tower are burned in the direct-fired furnace 2. Natural gas is supplied to the gas supply end through the third flame arrester 6. The waste gas after combustion is sent to the waste heat steam boiler to exchange heat and generate by-product steam. The by-product steam generated by the waste heat steam boiler is incorporated into the external steam pipeline network. The waste gas after heat exchange enters the preheating heat exchanger 4 to preheat the waste gas mixed in the mixing box 9. The cooled waste gas enters the denitrification reactor 5 and mixes with the injected ammonia gas to carry out the denitrification reaction. The exhaust gas after the reaction in the denitrification reactor 5 enters the tail gas heat exchanger 10 to preheat the exhaust gas mixed in the mixing box 9. The cooled exhaust gas enters the circulating water heat exchanger 17. The exhaust gas after heat exchange enters the water spray tower 18 through the induced draft fan 16 to remove dust. The dust-removed exhaust gas is discharged through the chimney 19.

[0022] For example, high-ammonia-containing waste gas generated from the process of ammonitrile oxidation to isophthalonitrile is collected and passed into a water absorption tower 15. Most of the ammonia in the waste gas is efficiently removed through aqueous absorption. After ammonia absorption, the waste gas is sent to the mixing box 9 for subsequent treatment after being protected against backfire by the first flame arrester 12. Simultaneously, the ammonia-containing wastewater formed after ammonia absorption is collected from the bottom of the water absorption tower 15. The waste gas introduced into the mixing box 9 is supplemented with dilution and combustion air by the fresh air fan 8. On the one hand, the concentration of organic components in the waste gas is controlled within the safe limit, and on the other hand, the oxygen content of the gas meets the process requirements for subsequent full combustion. The waste gas, after being uniformly mixed in the mixing box 9, is pressurized by the booster fan and then enters the preheating stage to complete the temperature rise. It is then sent to the TO direct-fired furnace 2 for combustion treatment. The ammonia-containing absorbent liquid collected from the bottom of the water absorption tower 15 is fed into the deammoniation tower. The deammoniation tower utilizes the synergistic effect of its internal reflux condenser and forced circulation reboiler to achieve efficient desorption and separation of ammonia from the absorbent liquid. The desorbed ammonia gas is pressurized by a desorption gas booster fan and, after passing through a second flame arrester 7 for safety protection, is sent as fuel gas to the TO direct-fired furnace 2. Combustion releases heat to provide a heat source for the furnace. Most of the low-ammonia wastewater from the bottom of the deammoniation tower is returned to the water absorption tower 15 for recycling, continuing to absorb ammonia from process waste gas. A small amount of wastewater that does not meet the recycling requirements is sent to a wastewater treatment plant for specialized treatment.

[0023] The mixed waste gas prepared by the mixing box 9 and the ammonia gas desorbed by the deammoniation tower are sent together into the combustion chamber of the TO direct-fired furnace 2 for mixed combustion. In order to maintain the stable temperature of the combustion chamber of the direct-fired furnace 2 and ensure the continuous and efficient combustion reaction, a third flame arrester 6 is installed at the natural gas supply end. A small amount of natural gas is added to the direct-fired furnace 2 as auxiliary fuel through the flame arrester. The high-temperature waste gas generated after the combustion reaction of the direct-fired furnace 2 is sent to the waste heat steam boiler to exchange heat using the waste heat of the high-temperature waste gas to produce by-product steam.

[0024] The by-product steam generated by the waste heat steam boiler is directly incorporated into the 0.6MPaG steam pipeline network outside the plant area to realize the resource recovery and utilization of process waste heat. The exhaust gas after being cooled by the waste heat steam boiler enters the preheating heat exchanger 4 as a heat source to preheat the mixed exhaust gas after being regulated by the mixing box 9, thus completing the secondary heat recovery. The exhaust gas that is further cooled after being heated by the preheating heat exchanger 4 is sent to the SCR denitrification reactor 5, where the exhaust gas is fully mixed with the injected ammonia gas to carry out the denitrification reaction.

[0025] The exhaust gas after the denitrification reaction in the SCR denitrification reactor 5 continues to enter the tail gas heat exchanger 10, where it is preheated again by the mixed exhaust gas after being adjusted by the mixing box 9, maximizing the recovery of residual heat in the exhaust gas. The exhaust gas cooled by the tail gas heat exchanger 10 enters the circulating water heat exchanger 17, where it is further cooled by circulating water heat exchange. After being pressurized by the TO induced draft fan 16, the cooled exhaust gas is sent to the water spray tower 18 to remove any remaining dust and impurities. The final exhaust gas purified by the water spray tower 18 meets all national emission standards and is discharged through the chimney 19 in compliance with regulations.

[0026] Reference Figure 2 The present invention also provides an embodiment of an ammonia oxidation reaction waste gas treatment system for operating the ammonia oxidation reaction waste gas treatment method in the above embodiment. The treatment system includes a water absorption tower 15, an ammonia removal tower, a direct-fired furnace 2, a waste heat steam boiler, a preheating heat exchanger 4, a denitrification reactor 5, and a tail gas heat exchanger 10. The water absorption tower 15 is connected to the deammoniation tower and the tail gas heat exchanger 10 for absorbing waste gas; the deammoniation tower includes a first deammoniation tower 14 and / or a second deammoniation tower 13, which is connected to the desorption blower 11 for desorbing waste gas; the direct-fired furnace 2 is connected to the deammoniation tower for burning waste gas; the waste heat steam boiler is connected to the direct-fired furnace 2 for producing waste heat steam; the preheating heat exchanger 4 is connected to the waste heat steam boiler for preheating waste gas; the denitrification reactor 5 is connected to the preheating heat exchanger 4 for catalytic denitrification reaction; and the tail gas heat exchanger 10 is connected to the denitrification reactor 5 and the water absorption tower 15 for exchanging heat with the tail gas.

[0027] For example, the ammonia removal tower is bidirectionally connected to the water absorption tower 15 and the desorption gas blower 11, receiving ammonia-containing wastewater from the water absorption tower 15 and sending the desorbed ammonia gas to the desorption gas blower 11; a mixing box 9 is connected in series on the connecting pipe between the water absorption tower 15 and the tail gas heat exchanger 10, and a first flame arrester 12 is installed on the pipe between the water absorption tower 15 and the mixing box 9. The mixing box 9 is also connected to the fresh air blower 8 to supplement and dilute the combustion air; a second flame arrester 7 is installed on the connecting pipe between the desorption gas blower 11 and the direct-fired furnace 2, and the direct-fired furnace 2 is simultaneously connected to the third flame arrester 6 and the exhaust gas... The booster fan 1 is connected to the third flame arrester 6, which is a safety protection device for the natural gas feeding end. The exhaust gas booster fan 1 is responsible for pressurizing and transporting the exhaust gas to be combusted. The preheating heat exchanger 4 and the tail gas heat exchanger 10 are both connected to the exhaust gas booster fan 1, and the two work together to provide a preheating heat source for the pressurized mixed exhaust gas. The rear end of the tail gas heat exchanger 10 is connected to the circulating water heat exchanger 17 and the induced draft fan 16 in sequence. The induced draft fan 16 is then connected to the water spray tower 18. The end of the water spray tower 18 is connected to the chimney 19. The exhaust gas after multi-stage purification is finally discharged through the chimney 19 in compliance with standards.

[0028] Understandably, due to the small dilution air volume, the treatment system can effectively reduce the amount of dilution combustion air replenishment by reusing the high-purity ammonia desorbed from the deammoniation tower as fuel gas for the direct-fired furnace 2. Simultaneously, it can replace some natural gas as a heat source for the direct-fired furnace 2, significantly reducing natural gas consumption. Under the same waste gas treatment capacity, the reduction in dilution air consumption can significantly reduce the design size of each piece of equipment within the treatment system, while effectively reducing the actual waste gas treatment capacity of the direct-fired furnace 2 and the denitrification reactor 5, thereby significantly reducing the initial investment cost and daily operating energy consumption. Furthermore, the treatment system has a high degree of parameter matching in each process stage, mild operating conditions, and is easy to precisely control, effectively improving the overall removal efficiency of various pollutants such as ammonia, volatile organic compounds, and nitrogen oxides in the waste gas.

[0029] As a preferred embodiment, the packing material in the water absorption tower 15 of this application is selected from one or more of corrugated packing, grid packing, wire mesh packing, Pall rings, conjugate rings, cross rings, and θ mesh rings. All of the above packing materials are suitable for the mass transfer requirements of the gas-liquid two phases in the water absorption tower 15. Considering the absorption characteristics of high ammonia content waste gas in the isophthalonitrile process, preferably, the packing material in the water absorption tower 15 is selected from one or more of corrugated packing, grid packing, and wire mesh packing. This type of packing material has the characteristics of large specific surface area, high mass transfer efficiency, low fluid resistance, and is not easy to clog, which can significantly improve the absorption efficiency of ammonia.

[0030] As a preferred embodiment, the water absorption tower 15 has 25 to 150 trays, a top temperature of 20 to 50°C, a bottom temperature of 30 to 60°C, and a top pressure of 2 to 10 kPaG. Based on improving absorption efficiency and controlling energy consumption, preferably, the water absorption tower 15 has 40 to 100 trays, a top temperature of 20 to 35°C, a bottom temperature of 30 to 45°C, and a top pressure of 2 to 5 kPaG. This preferred parameter range enables efficient ammonia removal while avoiding increased energy consumption and excessive equipment load due to excessively high parameters. The isophthalonitrile process waste gas received by the treatment system of this application before entering the water absorption tower 15 has a complex composition and contains a variety of polluting gases, mainly including ammonia, carbon monoxide, hydrogen cyanide, m-xylene, benzonitrile, as well as oxygen, nitrogen, carbon dioxide and other inert gases; the specific volume percentage of each component is as follows: ammonia accounts for 4-12% vol, carbon monoxide accounts for 0.2-1% vol, hydrogen cyanide accounts for 0.2-1% vol, m-xylene accounts for 0.01-0.05% vol, oxygen accounts for 6-14% vol, nitrogen accounts for 65-80% vol, carbon dioxide accounts for 1-3% vol, benzonitrile accounts for 0.01-0.05% vol, and inert gases account for 0.5-1% vol. Correspondingly, after the ammonia absorption pretreatment is completed in the water absorption tower 15, the composition of the waste gas entering the subsequent process is adjusted compared to that before entering the water absorption tower 15. It mainly includes ammonia, carbon monoxide, hydrogen cyanide, m-xylene, benzonitrile, oxygen, nitrogen, carbon dioxide and other inert gases; the specific contents are as follows: ammonia accounts for 1-4% vol, carbon monoxide accounts for 0.2-1% vol, hydrogen cyanide accounts for 0.1-0.5% vol, m-xylene accounts for 0.01-0.05% vol, oxygen accounts for 6-15% vol, nitrogen accounts for 68-85% vol, carbon dioxide accounts for 1-3% vol, benzonitrile accounts for 0.01-0.05% vol, and inert gases account for 0.5-1% vol.

[0031] In a preferred embodiment, the configuration of the ammonia removal tower can be flexibly adjusted, specifically including two configurations: a first ammonia removal tower 14 and / or a second ammonia removal tower 13. For example, depending on the waste gas treatment volume and ammonia desorption requirements, only the first ammonia removal tower 14 can be set up, or the first ammonia removal tower 14 and the second ammonia removal tower 13 can be set up in combination. To further improve the ammonia desorption efficiency and the purity of the desorbed ammonia, preferably, the ammonia removal tower adopts a configuration in which the first ammonia removal tower 14 and the second ammonia removal tower 13 are connected in series, and the second ammonia removal tower 13 is connected to the desorption gas fan 11 and the water absorption tower 15 respectively, so that the high-purity ammonia gas after desorption is sent to the desorption gas fan 11, and the low-ammonia wastewater after desorption is returned to the water absorption tower 15 for recycling.

[0032] The tray types of the first ammonia removal tower 14 and the second ammonia removal tower 13 can be selected according to process requirements. Specifically, any one of bubble cap trays, sieve trays, and solid valve trays can be selected. All types of trays can meet the gas-liquid mass transfer requirements in the desorption process of ammonia-containing wastewater. Preferably, both the first ammonia removal tower 14 and the second ammonia removal tower 13 are selected using SVG solid valve trays. This type of tray has the characteristics of large operating flexibility, sufficient gas-liquid contact, high mass transfer efficiency, and strong anti-clogging ability. It is suitable for the continuous desorption process of ammonia-containing wastewater and can effectively ensure the stability of ammonia desorption efficiency. To ensure the stable operation and purity of ammonia desorption, both the first ammonia removal tower 14 and the second ammonia removal tower 13 are equipped with internal reflux condensers and forced circulation reboilers. The forced circulation reboiler provides continuous and stable heat for the desorption of ammonia-containing wastewater in the tower, ensuring efficient desorption of ammonia from the wastewater. The internal reflux condenser partially condenses and refluxes the gas phase desorbed from the top of the tower, achieving the separation of ammonia from trace amounts of water vapor and impurities, effectively improving the purity of the desorbed ammonia, and ensuring the stable operation of the ammonia removal tower and the ammonia desorption effect. The first ammonia removal tower 14, as a primary ammonia desorption unit, mainly achieves the preliminary desorption of most of the ammonia gas in the ammonia-containing wastewater. The top pressure of the first ammonia removal tower 14 is 1-20 kPaG, the top temperature of the first ammonia removal tower 14 is 60-80℃, and the bottom temperature of the first ammonia removal tower 14 is 100-106℃. Preferably, the top pressure of the first ammonia removal tower 14 is 1-10 kPaG, the top temperature of the first ammonia removal tower 14 is 65-75℃, and the bottom temperature of the first ammonia removal tower 14 is 100-103℃. The second ammonia removal tower 13 serves as a secondary ammonia desorption unit, used to desorb the wastewater after desorption by the first ammonia removal tower 14, thereby achieving secondary desorption of the remaining ammonia. The top pressure of the second ammonia removal tower 13 is 1–20 kPaG, the top temperature of the second ammonia removal tower 13 is 60–80°C, and the bottom temperature of the second ammonia removal tower 13 is 70–90°C. Preferably, the top pressure of the second ammonia removal tower 13 is 1–10 kPaG, the top temperature of the second ammonia removal tower 13 is 65–75°C, and the bottom temperature of the second ammonia removal tower 13 is 70–80°C.

[0033] As a preferred option, the ratio of the amount of waste gas absorbed by water entering the mixing box 9 to the amount of fresh air diluted for combustion is any one of 1:1, 1:0.9, 1:0.8, 1:0.7, and 1:0.6. This ratio range can control the concentration of organic components in the waste gas within the safe combustion limit and ensure that the oxygen content of the gas meets the requirements for full combustion in the subsequent direct-fired furnace 2. Based on the consideration of reducing the amount of fresh air supplement and reducing the system processing load, the preferred ratio of the amount of waste gas absorbed by water entering the mixing box 9 to the amount of fresh air diluted for combustion is any one of 1:0.8 and 1:0.7.

[0034] As a preferred option, the direct-fired furnace 2 adopts the TO direct-fired furnace 2, which can achieve a purification efficiency of over 99.9% for pollutants in the exhaust gas; while the purification efficiency of the traditional regenerative RTO combustion furnace can only reach a maximum of 99%. In comparison, the purification efficiency of the TO direct-fired furnace 2 for isophthalonitrile process exhaust gas is significantly higher than that of the regenerative RTO combustion furnace. To ensure a balanced and stable internal temperature and achieve full mixing and combustion of multiple gas sources, the TO direct-fired furnace 2 is equipped with an integrated burner, with 2-8 sets of integrated burners; preferably, 4 sets of integrated burners are provided, which can achieve a uniform distribution of furnace temperature and ensure the stability of the combustion reaction. Meanwhile, the residence time of the exhaust gas in the TO direct-fired furnace 2 is set to any one of 4s, 5s, and 6s, with 5s being the preferred residence time, which ensures the complete combustion and decomposition of pollutants. Each integrated burner has a multi-spray gun structure, including one mixed exhaust gas spray gun, one ammonia desorption spray gun, and one natural gas spray gun, which can achieve precise addition and uniform mixing of mixed exhaust gas, ammonia desorption, and auxiliary natural gas. The combustion temperature inside the TO direct-fired furnace 2 is 900-1100℃, providing sufficient activation energy for the oxidative decomposition of pollutants. To reduce heat loss within the furnace chamber of the TO direct-fired furnace 2, maintain stable combustion temperature, and minimize heat loss from the outer wall of the furnace, the TO direct-fired furnace 2 is insulated with aluminosilicate ceramic fiber. The insulation material is aluminosilicate ceramic fiber with a bulk density ≥220kg / m3 and a thickness of 300mm. It features high temperature resistance, low thermal conductivity, and long-lasting insulation effect, effectively ensuring stable furnace temperature and further saving system operating energy consumption.

[0035] Understandably, the direct-fired furnace 2 has a higher purification efficiency for high ammonia-containing waste gas. By first absorbing with water and then heating and desorbing, most of the ammonia in the high-concentration ammonia-containing waste gas is converted into an independent NH3 gas stream and used as fuel gas for the direct-fired furnace 2. This method can effectively reduce the amount of dilution combustion air supplement and natural gas consumption, thereby reducing the amount of waste gas treated by the direct-fired furnace 2 and the denitrification reactor 5, and effectively reducing equipment investment and operating energy consumption.

[0036] As a preferred solution, the waste heat steam boiler is equipped with a deaerator, boiler feed water pump, steam boiler and periodic blowdown expansion tank to ensure the stability and safety of waste heat recovery and steam production, and realize the efficient resource utilization of high-temperature waste heat.

[0037] As a preferred option, the SCR denitrification reactor 5 is equipped with an ammonia water storage tank and a metering pump to control the ammonia water flow rate. At the same time, the denitrification reactor 5 is equipped with 2 to 4 layers of denitrification catalyst, which can effectively extend the contact time between the exhaust gas and the catalyst and improve the catalytic reaction efficiency. The denitrification reaction temperature of the denitrification reactor 5 is controlled at 300 to 400°C. This temperature range is the optimal activity temperature of the denitrification catalyst, which can ensure the efficient catalytic reduction of NOx.

[0038] Example 1 In this embodiment, the packing material of the water absorption tower 15 is selected from corrugated packing, the number of trays of the water absorption tower 15 is 60, the temperature at the top of the water absorption tower 15 is 25°C, the temperature at the bottom of the water absorption tower 15 is 40°C, and the pressure at the top of the water absorption tower 15 is 5 kPaG. In this embodiment, the ammonia removal towers consist of a first ammonia removal tower 14 and a second ammonia removal tower 13 connected in series, and both towers use SVG solid valve trays. The pressure at the top of the first ammonia removal tower 14 is 10 kPaG, the temperature at the top of the first ammonia removal tower 14 is 65°C, and the temperature at the bottom of the first ammonia removal tower 14 is 102°C. The pressure at the top of the second ammonia removal tower 13 is 10 kPaG, the temperature at the top of the second ammonia removal tower 13 is 80°C, and the temperature at the bottom of the second ammonia removal tower 13 is 104°C. In this embodiment, the ratio of the amount of water absorbing the exhaust gas entering the mixing box 9 to the amount of diluted combustion-supporting fresh air is 1:0.7; In this embodiment, the TO direct-fired furnace 2 is equipped with 4 sets of integrated burners. Each set of integrated burners includes 1 mixed air exhaust gas spray gun, 1 ammonia desorption spray gun and 1 natural gas spray gun. The residence time of the exhaust gas in the TO direct-fired furnace 2 is 5s. The internal combustion temperature of the TO direct-fired furnace 2 is 1000℃. In this embodiment, the SCR denitrification reactor 5 has two layers of denitrification catalyst inside, and the denitrification reaction temperature is 350℃; In this embodiment, the flow rate of the high-ammonia-content waste gas generated by the ammonia oxidation reaction is 16000 Nm3 / h. The composition of the waste gas before entering the water absorption tower 15 is as follows: ammonia accounts for 8% vol, carbon monoxide accounts for 0.3% vol, hydrogen cyanide accounts for 0.5% vol, m-xylene accounts for 0.05% vol, oxygen accounts for 10% vol, nitrogen accounts for 77.5% vol, carbon dioxide accounts for 2% vol, benzonitrile accounts for 0.05% vol, inert gas accounts for 0.6% vol, and water accounts for 1% vol. In this embodiment, the exhaust gas flow rate after the water inlet absorption tower 15 is 14800 Nm3 / h, and the composition of the exhaust gas after the water inlet absorption tower 15 is as follows: ammonia accounts for 2% vol, carbon monoxide accounts for 0.3% vol, hydrogen cyanide accounts for 0.3% vol, m-xylene accounts for 0.04% vol, oxygen accounts for 11% vol, nitrogen accounts for 83.7% vol, carbon dioxide accounts for 1% vol, benzonitrile accounts for 0.04% vol, inert gas accounts for 0.1% vol, and water accounts for 0.6% vol. In this embodiment, the fresh air supply volume of the mixing box 9 is 10360 Nm3 / h, the total exhaust gas flow rate after mixing is 25160 Nm3 / h, and the total ammonia desorption flow rate is 1200 Nm3 / h.

[0039] Example 2 In this embodiment, the packing material of the water absorption tower 15 is selected from corrugated packing, the number of trays of the water absorption tower 15 is 80, the temperature at the top of the water absorption tower 15 is 30°C, the temperature at the bottom of the water absorption tower 15 is 45°C, and the pressure at the top of the water absorption tower 15 is 8 kPaG. In this embodiment, the ammonia removal tower is a first ammonia removal tower 14, and the first ammonia removal tower 14 adopts an SVG solid valve tray; the pressure at the top of the first ammonia removal tower 14 is 10 kPaG, the temperature at the top of the first ammonia removal tower 14 is 70°C, and the temperature at the bottom of the first ammonia removal tower 14 is 104°C. In this embodiment, the ratio of the amount of waste gas absorbed by water entering the mixing box 9 to the amount of fresh air diluted for combustion is 1:0.6; In this embodiment, the TO direct-fired furnace 2 is equipped with 4 sets of integrated burners. Each set of integrated burners includes 1 mixed air exhaust gas spray gun, 1 ammonia desorption spray gun and 1 natural gas spray gun. The residence time of the exhaust gas in the TO direct-fired furnace 2 is 4s. The internal combustion temperature of the TO direct-fired furnace 2 is 1050℃. In this embodiment, the SCR denitrification reactor 5 has two layers of denitrification catalyst inside, and the denitrification reaction temperature is 300℃; In this embodiment, the flow rate of the high-ammonia-content waste gas generated by the ammonia oxidation reaction is 16000 Nm3 / h. The composition of the waste gas before entering the water absorption tower 15 is as follows: ammonia accounts for 8% vol, carbon monoxide accounts for 0.3% vol, hydrogen cyanide accounts for 0.5% vol, m-xylene accounts for 0.05% vol, oxygen accounts for 10% vol, nitrogen accounts for 77.5% vol, carbon dioxide accounts for 2% vol, benzonitrile accounts for 0.05% vol, inert gas accounts for 0.6% vol, and water accounts for 1% vol. In this embodiment, the exhaust gas flow rate after the water inlet absorption tower 15 is 14800 Nm3 / h, and the composition of the exhaust gas after the water inlet absorption tower 15 is as follows: ammonia accounts for 2% vol, carbon monoxide accounts for 0.3% vol, hydrogen cyanide accounts for 0.3% vol, m-xylene accounts for 0.04% vol, oxygen accounts for 11% vol, nitrogen accounts for 83.7% vol, carbon dioxide accounts for 1% vol, benzonitrile accounts for 0.04% vol, inert gas accounts for 1% vol, and water accounts for 0.6% vol. In this embodiment, the fresh air supply volume of the mixing box 9 is 8880 Nm3 / h, the total exhaust gas flow rate after mixing is 23480 Nm3 / h, and the total ammonia desorption flow rate is 1200 Nm3 / h.

[0040] Example 3 In this embodiment, the packing material of the water absorption tower 15 is selected from corrugated packing, the number of trays of the water absorption tower 15 is 50, the temperature at the top of the water absorption tower 15 is 30°C, the temperature at the bottom of the water absorption tower 15 is 45°C, and the pressure at the top of the water absorption tower 15 is 8 kPaG. In this embodiment, the ammonia removal towers consist of a first ammonia removal tower 14 and a second ammonia removal tower 13 connected in series, and both towers use SVG solid valve trays. The pressure at the top of the first ammonia removal tower 14 is 8 kPaG, the temperature at the top of the first ammonia removal tower 14 is 70°C, and the temperature at the bottom of the first ammonia removal tower 14 is 103°C. The pressure at the top of the second ammonia removal tower 13 is 8 kPaG, the temperature at the top of the second ammonia removal tower 13 is 80°C, and the temperature at the bottom of the second ammonia removal tower 13 is 105°C. In this embodiment, the ratio of the amount of waste gas absorbed by water entering the mixing box 9 to the amount of fresh air diluted for combustion is 1:0.6; In this embodiment, the TO direct-fired furnace 2 is equipped with 6 sets of integrated burners. Each set of integrated burners includes 1 mixed air exhaust gas spray gun, 1 ammonia desorption spray gun and 1 natural gas spray gun. The residence time of the exhaust gas in the TO direct-fired furnace 2 is 6s. The internal combustion temperature of the TO direct-fired furnace 2 is 950℃. In this embodiment, the SCR denitrification reactor 5 has 3 layers of denitrification catalyst inside, and the denitrification reaction temperature is 300℃; In this embodiment, the flow rate of the high-ammonia-content waste gas generated by the ammonia oxidation reaction is 16000 Nm3 / h. The composition of the waste gas before entering the water absorption tower 15 is as follows: ammonia accounts for 8% vol, carbon monoxide accounts for 0.3% vol, hydrogen cyanide accounts for 0.5% vol, m-xylene accounts for 0.05% vol, oxygen accounts for 10% vol, nitrogen accounts for 77.5% vol, carbon dioxide accounts for 2% vol, benzonitrile accounts for 0.05% vol, inert gas accounts for 0.6% vol, and water accounts for 1% vol. In this embodiment, the exhaust gas flow rate after the water inlet absorption tower 15 is 14800 Nm3 / h, and the composition of the exhaust gas after the water inlet absorption tower 15 is as follows: ammonia accounts for 2% vol, carbon monoxide accounts for 0.3% vol, hydrogen cyanide accounts for 0.3% vol, m-xylene accounts for 0.04% vol, oxygen accounts for 11% vol, nitrogen accounts for 83.7% vol, carbon dioxide accounts for 1% vol, benzonitrile accounts for 0.04% vol, inert gas accounts for 1% vol, and water accounts for 0.6% vol. In this embodiment, the fresh air supply volume of the mixing box 9 is 8880 Nm3 / h, the total exhaust gas flow rate after mixing is 23480 Nm3 / h, and the total ammonia desorption flow rate is 1200 Nm3 / h.

[0041] Comparative Example 1 In this embodiment, the waste gas treatment system does not include the water absorption tower 15 and the ammonia removal tower system; In this embodiment, the TO direct-fired furnace 2 is equipped with 4 sets of integrated burners. Each set of integrated burners in the TO direct-fired furnace 2 contains only one mixed air exhaust gas spray gun and one natural gas spray gun. The residence time of the exhaust gas in the TO direct-fired furnace 2 is 5s, and the internal combustion temperature of the TO direct-fired furnace 2 is 1000℃. In this embodiment, the SCR denitrification reactor 5 has two layers of denitrification catalyst inside, and the denitrification reaction temperature is 300℃; In this embodiment, the flow rate of the high-ammonia-content waste gas generated by the ammonia oxidation reaction is 16000 Nm3 / h. The composition of the waste gas before entering the water absorption tower 15 is as follows: ammonia accounts for 8% vol, carbon monoxide accounts for 0.3% vol, hydrogen cyanide accounts for 0.5% vol, m-xylene accounts for 0.05% vol, oxygen accounts for 10% vol, nitrogen accounts for 77.5% vol, carbon dioxide accounts for 2% vol, benzonitrile accounts for 0.05% vol, inert gas accounts for 0.6% vol, and water accounts for 1% vol. In this embodiment, the high ammonia content waste gas enters the mixing box 9 directly after passing through the first flame arrester 12. The fresh air supply volume of the mixing box 9 is 30,000 Nm3 / h, and the total flow rate of the waste gas after mixing is 46,000 Nm3 / h.

[0042] The pollutant emission concentrations and natural gas consumption of the treatment systems in Examples 1-3 and Comparative Example 1 were measured, and the results are shown in Table 1.

[0043] Table 1 Comparison of Pollutant Emission Concentration and Natural Gas Consumption of the Treatment System

[0044] As shown in Table 1, the pollutant emission concentration of the treatment system fully meets the emission standard reference standard "Emission Standard of Air Pollutants for Pesticide Manufacturing Industry" (GB39727-2020). As can be seen from the above embodiments and comparative examples, this application converts most of the ammonia in high-concentration ammonia-containing waste gas into an independent NH3 gas stream by first absorbing with water and then heating and desorbing, and uses it as fuel gas for the TO direct-fired furnace 2. This method effectively reduces the amount of dilution combustion air supplement and natural gas consumption, significantly reducing the natural gas energy consumption of the equipment operation. Moreover, due to the small total mixed air volume and low dilution ratio, the overall system treatment load of this application is low, the pollutant treatment efficiency is high, and the generation of nitrogen oxides is low, so that all pollutants can achieve compliant emissions.

[0045] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for treating ammonia oxidation reaction waste gas, applied to an ammonia oxidation reaction waste gas treatment system, characterized in that, include: The waste gas generated by the isophthalonitrile process is collected and passed into a water absorption tower to absorb ammonia. The absorbed waste gas then enters the mixing box after passing through the first flame arrester. The exhaust gas entering the mixing box is supplemented with dilution combustion air to reduce its concentration. The mixed exhaust gas is preheated by a booster fan and then sent into the direct-fired furnace. The absorbent generated by the water absorption tower enters the deammoniation tower and passes through the internal reflux condenser and forced circulation reboiler to desorb ammonia. The desorbed ammonia passes through the desorption gas blower and the second flame arrester and enters the direct-fired furnace for combustion and heat generation. The desorbed wastewater is returned to the water absorption tower to absorb ammonia. The waste gas mixed in the mixing box and the ammonia desorbed from the deammoniation tower are combusted in a direct-fired furnace. Natural gas is supplemented at the gas supply end through a third flame arrester. The combusted waste gas is sent to a waste heat steam boiler for heat exchange to generate by-product steam. The by-product steam generated by the waste heat steam boiler is incorporated into the external steam pipeline network. The waste gas after heat exchange enters the preheating heat exchanger to preheat the waste gas mixed in the mixing box. The cooled waste gas enters the denitrification reactor and mixes with the injected ammonia gas to carry out the denitrification reaction. The exhaust gas after the denitrification reactor reaction enters the tail gas heat exchanger to preheat the exhaust gas mixed in the mixing box. The cooled exhaust gas enters the circulating water heat exchanger. The exhaust gas after heat exchange enters the water spray tower through the induced draft fan to remove dust. The dust-removed exhaust gas is then discharged through the chimney.

2. A system for treating ammonia oxidation reaction waste gas, characterized in that, The treatment system is used to operate the ammonia oxidation reaction waste gas treatment method as described in claim 1, and the treatment system includes: The water absorption tower, connected to the ammonia removal tower and the tail gas heat exchanger, is used to absorb waste gas; Ammonia removal tower, including a first ammonia removal tower and / or a second ammonia removal tower, is connected to a desorption gas blower and is used to desorb waste gas; A direct-fired furnace, connected to an ammonia removal tower, is used to burn waste gas; Waste heat steam boiler, connected to a direct-fired furnace, is used to produce waste heat steam; A preheating heat exchanger, connected to a waste heat steam boiler, is used to preheat waste gas; The denitrification reactor, connected to a preheating heat exchanger, is used for catalytic denitrification reaction; The exhaust gas heat exchanger is connected to the denitrification reactor and the water absorption tower to exchange heat with the exhaust gas.

3. The ammonia oxidation reaction waste gas treatment system according to claim 2, characterized in that, The ammonia removal tower is connected to the water absorption tower and the desorption gas blower; A mixing box is installed on the pipeline connecting the water absorption tower and the exhaust gas heat exchanger, and a first flame arrester is installed on the pipeline connecting the water absorption tower and the mixing box. The mixing box is connected to the fresh air fan. A second flame arrester is installed on the pipeline connecting the desorption gas fan and the direct-fired furnace. The direct-fired furnace is connected to the third flame arrester and the exhaust gas booster fan. The preheating heat exchanger is connected to the exhaust gas booster fan, and the tail gas heat exchanger is connected to the exhaust gas booster fan. The exhaust gas heat exchanger is connected to the circulating water heat exchanger, the circulating water heat exchanger is connected to the induced draft fan, the induced draft fan is connected to the water spray tower, and the water spray tower is connected to the chimney.

4. The ammonia oxidation reaction waste gas treatment system according to claim 2, characterized in that, The packing material in the water absorption tower is selected from one or more of corrugated packing, grid packing, wire mesh packing, Pall rings, conjugate rings, cross rings and θ mesh rings; preferably, the packing material in the water absorption tower is selected from one or more of corrugated packing, grid packing and wire mesh packing.

5. The ammonia oxidation reaction waste gas treatment system according to claim 2, characterized in that, The water absorption tower has 25 to 150 trays, a top temperature of 20 to 50°C, a bottom temperature of 30 to 60°C, and a top pressure of 2 to 10 kPaG; preferably, the water absorption tower has 40 to 100 trays, a top temperature of 20 to 35°C, a bottom temperature of 30 to 45°C, and a top pressure of 2 to 5 kPaG.

6. The ammonia oxidation reaction waste gas treatment system according to claim 2, characterized in that, The ammonia removal tower includes a first ammonia removal tower and / or a second ammonia removal tower, wherein the first ammonia removal tower is connected to the second ammonia removal tower, and the second ammonia removal tower is connected to the desorption gas blower and the water absorption tower. The first and second ammonia removal towers are selected from any one of bubble cap trays, sieve trays, and solid valve trays; preferably, the first and second ammonia removal towers are selected from solid valve trays. The first and second ammonia removal towers are equipped with internal reflux condensers and forced circulation reboilers. The pressure at the top of the first ammonia removal tower is 1–20 kPaG, the temperature at the top of the first ammonia removal tower is 60–80°C, and the temperature at the bottom of the first ammonia removal tower is 100–106°C; preferably, the pressure at the top of the first ammonia removal tower is 1–10 kPaG, the temperature at the top of the first ammonia removal tower is 65–75°C, and the temperature at the bottom of the first ammonia removal tower is 100–103°C.

7. The ammonia oxidation reaction waste gas treatment system according to claim 2, characterized in that, The top pressure of the second ammonia removal tower is 1-20 kPaG, the top temperature of the second ammonia removal tower is 60-80℃, and the bottom temperature of the second ammonia removal tower is 70-90℃; preferably, the top pressure of the second ammonia removal tower is 1-10 kPaG, the top temperature of the second ammonia removal tower is 65-75℃, and the bottom temperature of the second ammonia removal tower is 70-80℃.

8. The ammonia oxidation reaction waste gas treatment system according to claim 3, characterized in that, The ratio of the amount of waste gas absorbed by water entering the mixing box to the amount of fresh air diluted for combustion is any one of 1:1, 1:0.9, 1:0.8, 1:0.7 and 1:0.

6. Preferably, the ratio of the amount of waste gas absorbed by water entering the mixing box to the amount of fresh air diluted for combustion is any one of 1:0.8 and 1:0.

7.

9. The ammonia oxidation reaction waste gas treatment system according to claim 2, characterized in that, The direct-fired furnace is equipped with an integrated burner, which consists of 2-8 groups, preferably 4 groups. The residence time of the exhaust gas in the direct-fired furnace is any one of 4s, 5s, and 6s, preferably 5s. Each group of integrated burners includes a mixed-air exhaust gas spray gun, a desorbed ammonia spray gun, and a natural gas spray gun. The combustion temperature inside the direct-fired furnace is 900-1100℃.

10. The ammonia oxidation reaction waste gas treatment system according to claim 2, characterized in that, The waste heat steam boiler is equipped with a deaerator, a boiler feed water pump, a steam boiler, and a periodic blowdown expansion tank. The denitrification reactor is equipped with an ammonia water storage tank and a metering pump to control the ammonia water flow rate. The denitrification catalyst inside the denitrification reactor consists of 2 to 4 layers, and the denitrification temperature of the denitrification reactor is 300 to 400°C.

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