Heat preservation anti-crystallization efficient reaction type alkali washing and catalytic combustion integrated waste gas treatment system

Abstract

The invention discloses a thermal-insulation anti-crystallization efficient reaction type alkali washing and catalytic combustion integrated waste gas treatment system, which relates to the technical field of hazardous waste treatment and comprises an alkali washing vertical spray tower, an efficient demister, a plate heat exchanger, a catalytic combustion furnace and a system fan which are sequentially connected in series through a gas path pipeline to form a closed-loop treatment system, the alkali washing vertical type spray tower is provided with double-layer spray assemblies, the double-layer spray assemblies are distributed in a staggered mode from top to bottom in the waste gas flowing direction, and the efficient demister is used for removing water mist and liquid drops carried in the waste gas purified by the alkali washing vertical type spray tower. Catalytic combustion waste heat is directionally recycled to a spray tower and demister system, the equipment operation environment temperature is increased, the acid-base reaction rate can be increased, the acid waste gas absorption efficiency is improved, the risk of crystallization precipitation at low temperature is reduced, equipment icing under the low-temperature working condition is avoided, stable operation of the system is guaranteed, external energy dependence is reduced, and the energy consumption is reduced. And resource circulation and overall processing efficiency improvement are realized.

Description

Technical Field

[0001] This invention relates to the field of hazardous waste treatment technology, specifically a high-efficiency reactive alkaline washing and catalytic combustion integrated waste gas treatment system with heat preservation and anti-crystallization properties. Background Technology

[0002] The acidic and organic waste gases generated during hazardous waste disposal are complex in composition and highly hazardous, making their efficient purification a core technical challenge in the industry. Currently, the mainstream treatment solutions mostly adopt a combination of "alkaline absorption + catalytic combustion" process. This involves removing acidic components through alkaline spraying and then using catalytic combustion to oxidize and decompose organic pollutants. This technical approach has become a consensus in the industry. However, in actual operation, especially under harsh low-temperature conditions, existing systems have exposed many technical bottlenecks, which seriously restrict treatment efficiency and operational stability. First, the chemical reaction rate between acidic waste gas and alkaline solution is significantly affected by temperature. Low temperatures drastically reduce the reactivity, leading to decreased absorption efficiency and insufficient purification depth in the spray tower, making it difficult to meet increasingly stringent environmental emission standards. Simultaneously, the solubility of alkaline solution decreases at low temperatures, making it prone to crystallization within the spray components and pipes, causing equipment blockage and increasing maintenance costs and system failure risks. Second, in severe cold conditions such as winter, accumulated water and residual liquid inside the spray tower and demister are prone to freezing, which not only damages the equipment structure but also forces the system to shut down, preventing continuous and stable operation and posing environmental compliance risks to enterprises. On the other hand, the oxidation and decomposition of organic waste gas during catalytic combustion releases a large amount of heat energy. In existing technologies, this heat energy can only be initially recovered through heat exchange and used to preheat the waste gas to be treated. Most of the rest is lost directly with the exhaust gas, resulting in low energy utilization efficiency. In order to solve the problem of low-temperature operation, some companies use additional electric heat tracing or steam heating devices to keep the equipment warm. This not only increases the system's dependence on external energy and increases operating costs, but also goes against the development trend of "energy conservation and emission reduction" in the environmental protection industry.

[0003] In summary, existing hazardous waste gas treatment systems suffer from the dual contradictions of "low waste heat utilization rate" and "low-temperature operation risks." How to convert the idle heat energy during catalytic combustion into energy that improves the equipment's operating environment, while simultaneously achieving multiple goals such as improving waste gas treatment efficiency, preventing low-temperature freezing, and reducing the risk of crystallization, has become a technological direction that urgently needs to be broken through in the industry. Based on this, developing an integrated waste gas treatment system with both waste heat recovery and insulation functions is of great practical significance for promoting the technological upgrading of the hazardous waste treatment industry. Summary of the Invention

[0004] The purpose of this invention is to provide a high-efficiency, reactive, alkaline washing, catalytic combustion integrated waste gas treatment system with heat preservation and anti-crystallization properties, in order to solve the problems raised in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a heat-insulating, anti-crystallization, high-efficiency reactive alkaline washing and catalytic combustion integrated waste gas treatment system, comprising an alkaline washing vertical spray tower, a high-efficiency demister, a plate heat exchanger, a catalytic combustion furnace, and a system fan, which are connected in series through gas pipelines to form a closed-loop treatment system. The alkaline washing vertical spray tower is equipped with a double-layer spray assembly, which is staggered from top to bottom along the waste gas flow direction. The high-efficiency demister is used to remove water mist and droplets entrained in the waste gas after purification by the alkaline washing vertical spray tower. The plate heat exchanger is provided with a low-temperature side channel and a high-temperature side channel. The low-temperature side channel is used to introduce the exhaust gas to be treated after demisting, and the high-temperature side channel is used to introduce the high-temperature purified exhaust gas after catalytic combustion. The catalytic combustion furnace is equipped with a reaction zone and a catalyst. The outlet of the high-temperature side channel of the plate heat exchanger is also connected to a diversion pipeline. The diversion pipeline includes an exhaust branch pipe and a waste heat recovery branch. The exhaust branch pipe is connected to a high-altitude exhaust stack. The waste heat recovery branch is connected to the alkaline scrubbing vertical spray tower and the high-efficiency demister, respectively, and is used to introduce part of the purified exhaust gas after heat exchange and cooling as a preheated airflow into the alkaline scrubbing vertical spray tower and the high-efficiency demister.

[0006] As a preferred technical solution, the double-layer spray assembly configured in the alkaline washing vertical spray tower includes an upper spray unit and a lower spray unit. The spray coverage area of ​​the upper spray unit partially overlaps with that of the lower spray unit, and the overlapping area accounts for 30%-50% of the coverage area of ​​a single spray unit.

[0007] As a preferred technical solution, the high-efficiency demister has at least two-stage separation structures inside. The first-stage separation structure is a baffle plate demister assembly, and the second-stage separation structure is a wire mesh demister assembly. The baffle plate demister assembly and the wire mesh demister assembly are arranged sequentially along the exhaust gas flow direction.

[0008] As a preferred technical solution, the low-temperature side channel and the high-temperature side channel inside the plate heat exchanger are arranged in countercurrent, and the heat exchange temperature difference between the waste gas to be treated and the high-temperature purified waste gas inside the low-temperature side channel and the high-temperature side channel is not less than 80°C.

[0009] As a preferred technical solution, the high-efficiency demister has a two-stage demister structure, with the first stage being a metal wire mesh demister and the second stage being a high-efficiency fiber filter.

[0010] As a preferred technical solution, the waste heat recovery branch includes a first branch pipe and a second branch pipe. The first branch pipe is connected to the shell interlayer of the alkaline washing vertical spray tower, and the second branch pipe is connected to the air inlet of the high-efficiency demister. Both the first and second branch pipes are equipped with flow regulating valves.

[0011] As a preferred technical solution, a temperature sensor is installed in the shell jacket of the alkaline washing vertical spray tower. The temperature sensor is electrically connected to the flow regulating valve on the first branch pipe. When the temperature in the shell jacket is lower than 15°C, the flow regulating valve automatically increases its opening; when the temperature is higher than 30°C, the flow regulating valve automatically decreases its opening.

[0012] As a preferred technical solution, the ratio of the amount of purified exhaust gas discharged from the discharge branch pipe fittings to the amount of purified exhaust gas recovered by the waste heat recovery branch is in the range of 1:1 to 3:1, and the ratio is controlled by the proportional regulating valve on the diversion pipeline.

[0013] As a preferred technical solution, the absorbent in the alkaline washing vertical spray tower is a NaOH solution with a mass concentration ranging from 15% to 30%, the pH value of the spray liquid is ranging from 9 to 12, and the liquid-to-gas ratio of the spray volume of the absorbent to the volume of waste gas entering the spray tower is ranging from 2 to 5 L / m³.

[0014] As a preferred technical solution, the reaction temperature control range of the catalytic combustion furnace is 280℃-350℃, and the residence time of the exhaust gas in the reaction zone is 1.5-3s.

[0015] The specific waste gas treatment and waste heat utilization process of this system is as follows: 1. Pretreatment stage: The acidic and organic mixed waste gas generated from hazardous waste disposal first enters the alkaline vertical spray tower. Under the action of the double-layer staggered spray components, the waste gas and NaOH absorbent are fully in counter-current contact, and the acidic components are neutralized and removed efficiently by the alkaline solution. At this time, if the temperature sensor detects that the temperature of the spray tower shell jacket is lower than the set value, the first branch pipe of the waste heat recovery branch automatically increases the gas supply, and raises the temperature of the tower and the surrounding environment through the preheated airflow, accelerates the acid-base reaction rate, and inhibits the crystallization of alkaline solution.

[0016] 2. Demisting stage: The exhaust gas treated by the spray tower enters the high-efficiency demister and passes through the baffle plate demister assembly and the wire mesh demister assembly in sequence to remove water mist and droplets entrained in the exhaust gas; at the same time, the second branch pipe introduces preheated airflow into the air inlet of the demister to increase the internal temperature of the equipment and prevent water accumulation and freezing and residual liquid crystallization.

[0017] 3. Preheating and Catalytic Combustion Stage: After demisting, the exhaust gas enters the low-temperature side channel of the heat exchanger and exchanges heat with the high-temperature purified exhaust gas from the catalytic combustion furnace in the high-temperature side channel. The exhaust gas temperature is preheated to 220℃-260℃, and then enters the reaction zone of the catalytic combustion furnace. Under the action of the Pt-Pd alloy catalyst, the organic waste gas components undergo a full oxidation reaction at a reaction temperature of 280℃-350℃ to generate H2O and CO2, while releasing heat energy to raise the exhaust gas temperature.

[0018] 4. Waste Heat Recovery and Emission Stage: The high-temperature purified waste gas after catalytic combustion enters the high-temperature side channel of the heat exchanger. After heat exchange with the waste gas to be treated on the low-temperature side, the temperature drops to 120℃-180℃. Then, it is divided by the diversion pipeline. Part of it is discharged through the emission branch and discharged in compliance with standards through the high-altitude exhaust stack. The other part is introduced into the shell jacket of the alkaline vertical spray tower and the high-efficiency demister through the first and second branch pipes of the waste heat recovery branch, respectively, as a preheating airflow to realize the recycling of waste heat, forming a virtuous cycle of "catalytic combustion heat generation - waste heat recovery - equipment insulation - improved treatment efficiency".

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention achieves a dual improvement in waste gas treatment efficiency and purification depth by using catalytic combustion waste heat directional recovery technology. At the spray tower and demister ends, the recovered waste heat effectively increases the operating temperature of the equipment, promoting a 20%-30% increase in the chemical reaction rate between acidic waste gas and alkaline solution. The absorption efficiency of the spray tower for acidic components remains stable at over 95%, significantly enhancing the purification effect of acidic waste gas. At the same time, the preheated waste gas enters the catalytic combustion furnace, significantly reducing energy consumption during the reaction start-up stage and ensuring that the degradation rate of organic waste gas remains stable at over 99%, thereby improving the overall efficiency and reliability of waste gas treatment from multiple dimensions.

[0020] 2. This invention overcomes the operational limitations under extremely cold conditions by relying on a waste heat recycling mechanism, enabling the spray tower and demister to maintain a stable operating temperature of 15℃-30℃ in low-temperature environments such as winter. This design fundamentally eliminates the phenomenon of water accumulation and freezing inside the equipment, while significantly reducing the risk of alkali crystallization and precipitation. It effectively avoids problems such as equipment blockage and structural damage caused by freezing and crystallization, ensuring continuous and stable operation of the system throughout the year, completely eliminating potential environmental compliance hazards, and meeting the continuous operation requirements under harsh conditions. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the equipment layout of the present invention; Figure 2 This is a top view of the device of the present invention; Figure 3 This is a side view of the device of the present invention; Figure 4 This is a schematic diagram of the process flow of the present invention; Figure 5 This is a schematic diagram of the waste gas treatment process of the present invention.

[0022] The components include: 1. Alkali washing vertical spray tower; 2. High-efficiency demister; 3. Plate heat exchanger; 4. Catalytic combustion furnace; 5. System fan; 6. Exhaust stack; 7. Flow regulating valve; 8. Proportional regulating valve; 9. Waste heat recovery branch; 10. Discharge branch pipe fittings. Detailed Implementation

[0023] 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.

[0024] according to Figures 1-5 As shown, a high-efficiency reactive alkaline washing and catalytic combustion integrated waste gas treatment system with heat preservation and anti-crystallization properties includes an alkaline washing vertical spray tower 1, a high-efficiency demister 2, a plate heat exchanger 3, a catalytic combustion furnace 4, and a system fan 5, which are connected in series through gas pipelines to form a closed-loop treatment system. The alkaline washing vertical spray tower 1 is equipped with a double-layer spray assembly, which is staggered from top to bottom along the waste gas flow direction. The high-efficiency demister 2 is used to remove water mist and droplets entrained in the waste gas purified by the alkaline washing vertical spray tower 1. The plate heat exchanger 3 is provided with a low-temperature side channel and a high-temperature side channel. The low-temperature side channel is used for... The exhaust gas to be treated, which has undergone demisting treatment, is introduced into the high-temperature side channel. The high-temperature purified exhaust gas after catalytic combustion is introduced into the high-temperature side channel. The catalytic combustion furnace 4 is equipped with a reaction zone and a catalyst. The outlet of the high-temperature side channel of the plate heat exchanger 3 is also connected to a diversion pipeline. The diversion pipeline includes an exhaust branch pipe 10 and a waste heat recovery branch 9. The exhaust branch pipe 10 is connected to the high-altitude exhaust stack 6. The waste heat recovery branch 9 is connected to the alkaline scrubbing vertical spray tower 1 and the high-efficiency demister 2, respectively, and is used to introduce part of the purified exhaust gas after heat exchange and cooling as a preheated airflow into the alkaline scrubbing vertical spray tower 1 and the high-efficiency demister 2.

[0025] The alkaline scrubbing vertical spray tower 1 is equipped with a double-layer spray assembly, which includes an upper spray unit and a lower spray unit. The spray coverage of the upper spray unit partially overlaps with that of the lower spray unit, with the overlapping area accounting for 30%-50% of the coverage of a single spray unit. The high-efficiency demister 2 is equipped with at least two-stage separation structures. The first-stage separation structure is a baffle plate demister assembly, and the second-stage separation structure is a wire mesh demister assembly. The baffle plate demister assembly and the wire mesh demister assembly are arranged sequentially along the direction of exhaust gas flow.

[0026] The plate heat exchanger 3 has a low-temperature side channel and a high-temperature side channel arranged in countercurrent flow. The heat exchange temperature difference between the waste gas to be treated and the high-temperature purified waste gas inside the low-temperature side channel and the high-temperature side channel is not less than 80°C. The high-efficiency demister 2 has a two-stage demister structure. The first stage is a metal wire mesh demister and the second stage is a high-efficiency fiber filter. The waste heat recovery branch 9 includes a first branch pipe and a second branch pipe. The first branch pipe is connected to the shell interlayer of the alkaline washing vertical spray tower 1, and the second branch pipe is connected to the air inlet of the high-efficiency demister 2. Both the first branch pipe and the second branch pipe are equipped with flow regulating valves 7.

[0027] A temperature sensor is installed in the shell jacket of the alkaline washing vertical spray tower 1. The temperature sensor is electrically connected to the flow regulating valve 7 on the first branch pipe. When the temperature in the shell jacket is lower than 15℃, the flow regulating valve 7 automatically increases its opening; when the temperature is higher than 30℃, the flow regulating valve 7 automatically decreases its opening. The ratio of the amount of purified waste gas discharged from the discharge branch pipe fitting 10 to the amount of purified waste gas recovered by the waste heat recovery branch pipe 9 is in the range of 1:1-3:1. The ratio is controlled by the proportional regulating valve 8 on the diversion pipe. The absorbent in the alkaline washing vertical spray tower 1 is a NaOH solution with a mass concentration range of 15%-30%, the pH value of the spray liquid is in the range of 9-12, and the liquid-to-gas ratio of the amount of absorbent sprayed to the amount of waste gas entering the spray tower is in the range of 2-5 L / m³. The reaction temperature control range of the catalytic combustion furnace 4 is 280℃-350℃, and the residence time of the waste gas in the reaction zone is in the range of 1.5-3s.

[0028] Implementation Case: This example uses the treatment of acidic and organic mixed waste gas generated by a hazardous waste disposal center in northern China as an application scenario. Winter temperatures are low, and the waste gas contains acidic components such as HCl and H2S, with a total concentration of approximately 500 mg / m³, as well as organic components such as benzene, toluene, xylene, and alcohols, with a VOCs concentration of approximately 1500 mg / m³. The treatment capacity is 9000 m³ / h, and the lowest winter temperature can reach -15℃. Key issues to address include equipment insulation at low temperatures, alkali crystallization, and waste gas treatment efficiency.

[0029] The core equipment and connection relationships of the integrated waste gas treatment system for heat preservation, anti-crystallization, high-efficiency reactive alkaline washing and catalytic combustion in this embodiment are as follows: The specific dimensions of the alkaline washing vertical spray tower 1 are 1.7m in diameter and 5.8m in height. It uses a high-efficiency demister 2 to treat an air volume of 9000m³ / h with a pressure drop ≤500Pa. The air then passes through a plate heat exchanger 3 with a heat exchange area of ​​90m² and a design pressure of 1.6MPa. It also uses a catalytic combustion furnace 4 with an effective catalyst volume of 600L and a design temperature of 450℃. All equipment is connected in series through stainless steel gas pipelines. The pipelines are wrapped with 50mm thick aluminum silicate insulation cotton and 0.5mm thick aluminum sheet to reduce heat loss along the way. The discharge branch pipe fittings 10 and the waste heat recovery branch 9 in the diversion pipeline are respectively equipped with air volume proportional regulating valves 8 to achieve precise control of the waste gas diversion ratio. When the system starts up, the spray pump of the alkaline washing vertical spray tower 1 is started first to form a uniform and stable spray layer of NaOH absorbent with a mass concentration of 15%-30% in the tower. At the same time, the pH value of the absorbent is precisely adjusted to 10.5 by the automatic dosing device to ensure the neutralization efficiency of the acidic waste gas. Then, the electric heating device of the catalytic combustion furnace 4 is started to gradually raise the temperature of the reaction zone in the furnace to 300℃. Simultaneously, the air valve 11 of the circulation pipeline of the plate heat exchanger 3 and the system fan 5 are opened to drive the airflow in the system to establish initial circulation, complete the equipment preheating and airflow conduction. After the temperature in the catalytic combustion furnace 4 is stabilized above 300℃, the waste gas to be treated is introduced and the waste gas inlet flow rate is controlled at 9000 m³ / h. The start-up phase lasts for about 20 minutes until the operating parameters of each device reach the preset standards to ensure that the system enters a stable treatment state. The mixed waste gas generated during the hazardous waste disposal process is driven by the system fan 5 and first enters the alkaline washing vertical spray tower 1. The waste gas flows from bottom to top, forming a full counter-current contact with the NaOH absorption liquid sprayed from the double-layer staggered overlapping spray components inside the tower. The acidic components such as HCl and H2S in the waste gas undergo a rapid neutralization reaction with the alkaline solution, and the removal rate of acidic components is stably above 95%. During operation, the temperature sensor in the shell jacket of the alkaline washing vertical spray tower 1 monitors the temperature in real time. If the monitored value is below 15℃, the automatic temperature control system immediately increases the opening of the flow regulating valve 7 on the first branch pipe, introducing a preheated airflow of 120℃-180℃ into the jacket, so that the internal temperature of the alkaline washing vertical spray tower 1 quickly rises to the range of 15℃-30℃, which not only accelerates the acid-base reaction rate, but also effectively avoids the crystallization and blockage of the alkaline solution in the nozzles and pipes. If the jacket temperature is above 30℃, the flow regulating valve 7 automatically reduces the opening, reducing the input of preheated airflow, preventing the absorption liquid from evaporating too quickly due to excessive temperature, and ensuring the stable operation of the spray system. The exhaust gas treated by the alkaline scrubbing vertical spray tower 1 enters the high-efficiency demister 2. The baffle plate demister structure removes entrained droplets from the exhaust gas, reducing the moisture content to 0.01%, fully meeting the requirements for catalytic combustion intake conditions. Simultaneously, a metered preheated airflow is introduced into the intake end of the high-efficiency demister 2 through a second branch pipe, precisely maintaining the internal temperature of the demister above 15℃. This completely prevents residual liquid in the accumulation tank from freezing and ice buildup on the wire mesh components, ensuring long-term stable demisting efficiency. The demisting-treated exhaust gas then enters the low-temperature side channel of the plate heat exchanger 3, where it meets the 390℃ high-temperature purified exhaust gas from the catalytic combustion furnace 4 in the high-temperature side channel. The exhaust gas undergoes efficient heat exchange, rapidly increasing its temperature from 20℃ to approximately 240℃ before entering the catalytic combustion furnace's reaction zone 4. Under the action of a specialized catalyst, organic components in the exhaust gas, such as benzene, toluene, xylene, and alcohols, undergo complete oxidative decomposition reactions, achieving an organic waste gas degradation rate of over 99.5%. The reaction process releases a large amount of heat energy, raising the tail gas temperature to 380℃-400℃. After system startup, when the concentration of inlet organic waste gas stabilizes above 1500mg / m³, the heat energy released by the catalytic combustion reaction is sufficient to meet the temperature requirements of the reaction itself. At this point, the electric heating device is automatically shut off, enabling the system to operate self-sufficiently. The 380℃-400℃ high-temperature purified exhaust gas after catalytic combustion enters the high-temperature side channel of plate heat exchanger 3. After heat exchange with the low-temperature side exhaust gas, the temperature drops to 120℃-180℃, and then enters the diversion pipeline. Under the precise control of proportional regulating valve 8, about 2 / 3 of the purified exhaust gas is introduced into the 15m high exhaust stack 6 through the discharge branch pipe fitting 10 for high-altitude emission in compliance with standards. The concentration of acidic components and VOCs in the exhaust gas is ≤20mg / m³ and ≤20mg / m³, which strictly meets the relevant national and local emission standards. The remaining 1 / 3 of the purified exhaust gas is diverted through the waste heat recovery branch 9 and introduced into the shell jacket of the alkaline washing vertical spray tower 1 and the air inlet of the high-efficiency demister 2 through the first branch pipe and the second branch pipe, respectively, to achieve the directional recovery and recycling of waste heat. Before shutting down the system, gradually reduce the intake of exhaust gas while maintaining the normal operation of the spray system, demister system, and waste heat recovery system. When the VOCs concentration in the catalytic combustion furnace 4 drops below 50 mg / m³, stop the exhaust gas intake and shut down the catalytic combustion furnace 4. Keep the system fan 5 blowing the furnace body through the circulation pipeline for 30 minutes to prevent carbon buildup on the catalyst surface from affecting subsequent performance. After purging, close the plate heat exchanger 3 and the relevant valves of the waste heat recovery branch. Finally, stop the spray pump and discharge the remaining absorbent liquid in the alkaline washing vertical spray tower 1 and the accumulated liquid in the high-efficiency demister 2 into a dedicated waste liquid storage tank to complete the entire shutdown process.

[0030] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A heat-insulating, anti-crystallization, high-efficiency reactive alkaline washing and catalytic combustion integrated waste gas treatment system, comprising an alkaline washing vertical spray tower (1), a high-efficiency demister (2), a plate heat exchanger (3), a catalytic combustion furnace (4), and a system fan (5) connected in series through gas pipelines to form a closed-loop treatment system, characterized in that: The alkaline scrubbing vertical spray tower (1) is equipped with a double-layer spray assembly, which is staggered from top to bottom along the direction of exhaust gas flow; the high-efficiency demister (2) is used to remove water mist and droplets entrained in the exhaust gas after purification by the alkaline scrubbing vertical spray tower (1); the plate heat exchanger (3) is provided with a low-temperature side channel and a high-temperature side channel, the low-temperature side channel is used to introduce the exhaust gas to be treated after demister treatment, and the high-temperature side channel is used to introduce the high-temperature purified exhaust gas after catalytic combustion; the catalytic combustion furnace (4) is internal The plate heat exchanger (3) is equipped with a reaction zone and a catalyst. The high-temperature side channel outlet of the plate heat exchanger (3) is also connected to a diversion pipeline. The diversion pipeline includes an exhaust branch pipe fitting (10) and a waste heat recovery branch pipe (9). The exhaust branch pipe fitting (10) is connected to a high-altitude exhaust stack (6). The waste heat recovery branch pipe (9) is connected to the alkaline washing vertical spray tower (1) and the high-efficiency demister (2) respectively. It is used to introduce part of the purified waste gas after heat exchange and cooling as a preheated airflow into the alkaline washing vertical spray tower (1) and the high-efficiency demister (2).

2. The integrated waste gas treatment system for heat preservation, anti-crystallization, high-efficiency reactive alkaline washing and catalytic combustion according to claim 1, characterized in that: The alkaline washing vertical spray tower (1) is equipped with a double-layer spray assembly including an upper spray unit and a lower spray unit. The spray coverage of the upper spray unit partially overlaps with that of the lower spray unit, and the overlapping area accounts for 30%-50% of the coverage of a single spray unit.

3. The integrated waste gas treatment system for heat preservation, anti-crystallization, high-efficiency reactive alkaline washing and catalytic combustion according to claim 1, characterized in that: The high-efficiency demister (2) has at least two separation structures inside. The first separation structure is a baffle plate demister assembly, and the second separation structure is a wire mesh demister assembly. The baffle plate demister assembly and the wire mesh demister assembly are arranged sequentially along the direction of exhaust gas flow.

4. The integrated waste gas treatment system for heat preservation, anti-crystallization, high-efficiency reactive alkaline washing and catalytic combustion according to claim 1, characterized in that: The plate heat exchanger (3) has a low-temperature side channel and a high-temperature side channel arranged in countercurrent flow. The heat exchange temperature difference between the waste gas to be treated and the high-temperature purified waste gas inside the low-temperature side channel and the high-temperature side channel is not less than 80°C.

5. The integrated waste gas treatment system for heat preservation, anti-crystallization, high-efficiency reactive alkaline washing and catalytic combustion according to claim 2, characterized in that: The high-efficiency demister (2) has a two-stage demister structure. The first stage is a metal wire mesh demister, and the second stage is a high-efficiency fiber filter.

6. The integrated waste gas treatment system for heat preservation, anti-crystallization, high-efficiency reactive alkaline washing and catalytic combustion according to claim 1, characterized in that: The waste heat recovery branch (9) includes a first branch pipe and a second branch pipe. The first branch pipe is connected to the shell interlayer of the alkaline washing vertical spray tower (1), and the second branch pipe is connected to the air inlet of the high-efficiency demister (2). Both the first branch pipe and the second branch pipe are equipped with flow regulating valves (7).

7. The integrated waste gas treatment system for heat preservation, anti-crystallization, high-efficiency reactive alkaline washing and catalytic combustion according to claim 6, characterized in that: The shell jacket of the alkaline washing vertical spray tower (1) is equipped with a temperature sensor. The temperature sensor is electrically connected to the flow regulating valve (7) on the first branch pipe. When the temperature inside the shell jacket is lower than 15°C, the flow regulating valve (7) automatically increases its opening. When the temperature is higher than 30°C, the flow regulating valve (7) automatically decreases its opening.

8. The integrated waste gas treatment system for heat preservation, anti-crystallization, high-efficiency reactive alkaline washing and catalytic combustion according to claim 1, characterized in that: The ratio of the amount of purified exhaust gas discharged by the discharge branch pipe fitting (10) to the amount of purified exhaust gas recovered by the waste heat recovery branch (9) is in the range of 1:1 to 3:1, and the ratio is controlled by the proportional regulating valve (8) on the diversion pipe.

9. The integrated waste gas treatment system for heat preservation, anti-crystallization, high-efficiency reactive alkaline washing and catalytic combustion according to claim 1, characterized in that: The absorbent in the alkaline washing vertical spray tower (1) is a NaOH solution with a mass concentration range of 15%-30%, the pH value of the spray liquid is in the range of 9-12, and the liquid-to-gas ratio of the amount of absorbent sprayed to the amount of waste gas entering the spray tower is in the range of 2-5 L / m³.

10. The integrated waste gas treatment system for heat preservation, anti-crystallization, high-efficiency reactive alkaline washing and catalytic combustion according to claim 1, characterized in that: The reaction temperature control range of the catalytic combustion furnace (4) is 280℃-350℃, and the residence time of the exhaust gas in the reaction zone is 1.5-3s.

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