An apparatus and method for alkali destruction of phosgene tail gas

Abstract

The present application belongs to the technical field of phosgene reaction tail gas treatment, and particularly relates to a phosgene tail gas alkali destruction device and method, which comprises the following steps: an operator passes the tail gas into a falling film absorber, the falling film absorber absorbs hydrochloric acid in the tail gas to obtain treated gas one; the treated gas one is passed into a catalytic hydrolysis box, a catalytic hydrolysis method is used to destroy phosgene in the treated gas one to obtain treated gas two; the treated gas two is passed into a multi-stage alkali destruction tower, 1% to 10% of a dilute alkali solution is sent into the top of the alkali destruction tower through a delivery pump, inorganic salt solution and treated gas three are generated through an acid-base reaction; the inorganic salt solution is sent to a high-salt wastewater treatment device for treatment, the treated gas three is sent to a burning device for treatment to remove unreacted carbon monoxide, organic matter and other combustible gases to obtain final gas which is discharged to the outside. The scheme solves the problem of waste caused by a large amount of generated high-salt wastewater.

Description

Technical Field

[0001] This invention belongs to the field of phosgenation reaction tail gas treatment technology, specifically relating to a phosgenation tail gas alkaline destruction device and method. Background Technology

[0002] Phosgene is an important raw material for chemical production, with a domestic production capacity of 1.5 million tons (1.16 million tons in 2008). It is widely used in the production of pesticides, pharmaceuticals, fuels, polyurethanes, and other industries, but its high toxicity has drawn significant attention. In chemical production processes using phosgene as a raw material, phosgene-containing tail gas is generated. The content of phosgene in the tail gas varies depending on the process control requirements, generally ranging from 10% to 50% (v / v). Phosgene tail gas requires treatment before emission to minimize environmental pollution.

[0003] Currently, a method for treating phosgenation reaction tail gas with application number 201911412500.5 is available on the market. This method includes the following steps: passing the photoreaction tail gas into a spray absorption tower using solvent A as the absorbent, absorbing chlorine gas in the tail gas in the liquid phase; after solvent A is saturated, it is then desorbed to obtain separated chlorine gas; passing the remaining tail gas into a condensation tower to recover the organic solvent in the tail gas; passing the remaining tail gas into a spray absorption tower using solvent B as the absorbent, absorbing hydrogen chloride gas in the tail gas in the liquid phase; after solvent B is saturated, it is then desorbed to obtain separated hydrogen chloride gas; passing the remaining tail gas into a spray absorption tower using catalyst C as the absorbent, where it is hydrolyzed on the wetted catalyst surface into hydrogen chloride and carbon dioxide gas. This invention first absorbs and treats the chlorine gas in the tail gas, then treats the organic solvent in the tail gas to avoid affecting the use of the catalyst, then treats the hydrogen chloride in the tail gas, and finally treats the phosgene, resulting in good tail gas treatment effect.

[0004] However, there is also a problem: the solution generates a lot of high-salt wastewater, which leads to waste.

[0005] Currently, a phosgene exhaust gas treatment device with the market announcement number CN211799878U includes a hydrochloric acid absorption tower, a phosgene hydrolysis tower, a phosgene alkaline scrubbing tower, and an alkaline scrubbing tank. Each of these towers is equipped with a demister at its upper end. The hydrochloric acid absorption tower, phosgene hydrolysis tower, phosgene alkaline scrubbing tower, and alkaline scrubbing tank are connected by a packing support grid, with one and two packing beds connected. A first distributor is installed in the hydrochloric acid absorption tower below the demister. This phosgene exhaust gas treatment device absorbs hydrogen chloride from the exhaust gas through the hydrochloric acid absorption tower. Then, the phosgene in the exhaust gas is destroyed by the first and second stage hydrolysis towers, converting the absorbed hydrogen chloride gas into dilute hydrochloric acid. The dilute hydrochloric acid is cooled by a hydrochloric acid absorption cooler and enters the hydrochloric acid absorption tower for countercurrent spraying, ultimately producing qualified hydrochloric acid from the waste gas, reducing costs. After two stages of alkaline scrubbing in the alkaline scrubbing tower, the exhaust gas is discharged into a chimney by a fan, achieving pollution-free emissions.

[0006] However, some problems exist: 1. The alkaline washing tower uses spraying for gas-liquid mixing, which is inefficient and has a slow output. 2. If a distillation tower-type gas-liquid mixing method is used, although the efficiency is high, flooding is prone to occur. The existing method solves this problem by controlling the size of the filter holes in the tower plates. 3. Many inorganic salt particles are easily generated inside the alkaline washing tower, which can easily clog the pipes. While filter screens are commonly used, they need to be replaced periodically, and the alkaline washing tower is not easily disassembled. Summary of the Invention

[0007] This invention provides a device and method for alkaline destruction of phosgenation tail gas, which solves the problem of short service life of filter screens in alkaline destruction towers.

[0008] This solution provides a phosgenation tail gas alkaline destruction device, including a catalytic hydrolysis tank, an alkaline destruction tower, a pH meter, and a falling film absorber, wherein the falling film absorber, the catalytic hydrolysis tank, the alkaline destruction tower, and the pH meter are connected in sequence.

[0009] The alkali destruction tower includes a cleaning mechanism. The tower body is equipped with a tower plate. The cleaning mechanism includes an air inlet plate, a filter plate, and a cleaning brush. The air inlet plate and the filter plate are fixedly connected at a certain angle. The air inlet plate cooperates with the air inlet. The filter plate cooperates with the liquid outlet. The connection between the air inlet plate and the filter plate is rotatably connected to the tower body through a torque spring. The filter plate cooperates with the cleaning brush. The cleaning brush is fixedly connected to the tower body.

[0010] The principle of this scheme is as follows: The operator first passes the exhaust gas into a falling film absorber to remove hydrochloric acid from the exhaust gas. Then, the subsequent gas is passed into a catalytic hydrolysis tank, where catalytic hydrolysis destroys the phosgene. The remaining gas is then passed into an alkali destruction tower. The gas enters through the inlet, pushing open the inlet plate and causing the filter plate to rotate until it contacts and covers the liquid outlet, effectively filtering particles. Simultaneously, liquid enters through the inlet at the top of the tower, creating a counter-current flow that increases the contact area and maximizes the reaction. The tower plates slow down the liquid's descent, increasing the gas-liquid contact time. When the exhaust gas is completely treated, the device stops, and the inlet plate returns to its original position under the action of a torque spring. This causes the filter plate to tilt, bringing it into contact with the cleaning brush needles. The brush needles penetrate the filter plate's pores, cleaning away the adhering particles. This eliminates the need for the operator to disassemble the alkali destruction tower to replace the filter screen.

[0011] In the alkali destruction tower, the carbon dioxide and hydrogen chloride in the gas react with sodium hydroxide to produce inorganic salt solutions such as sodium carbonate, sodium chloride, and sodium bicarbonate. The pH value of the inorganic salt solution is measured by a pH meter. It can only be discharged if it reaches the set value. If it does not reach the set value, the staff needs to continue to send the liquid into the alkali destruction tower to react and convert all the harmful gases and carbon dioxide into gases that can be discharged.

[0012] The beneficial effects of this solution are: 1. The device achieves full contact between gas and liquid through countercurrent flow, resulting in a more thorough reaction and higher efficiency compared to spray reactions. 2. The device extends the service life of the filter screen through its cleaning mechanism.

[0013] Furthermore, it also includes an anti-flooding mechanism, which includes a connecting rod, a sliding plate, a baffle, and an insertion plate. The tower plate is provided with a groove, the insertion plate is slidably connected to the groove, the insertion plate is fixedly connected to the sliding plate, the baffle is fixedly connected to the tower body, and the baffle is slidably connected to the sliding plate. One end of the connecting rod is hinged to the sliding plate, and the other end is hinged to the filter plate.

[0014] When flooding occurs in the alkali destruction tower, the gas at the bottom cannot pass through the liquid above, causing an increase in pressure at the bottom. This reduces the gas flow rate into the inlet, causing the inlet plate to slowly move back due to the torque spring. Simultaneously, the filter plate also begins to move. The filter plate moves the connecting rod, which in turn moves the slide plate. The slide plate pulls out the insertion plate, a thin plate with filter holes. Pulling out the insertion plate lengthens the tower plate and increases the number of filter holes, making it easier for the liquid to fall. At the same time, it increases the gap between the downcomer and the slide plate, allowing more space for the liquid to pass through the gas, thus resolving the flooding problem. Once the gas pressure inside the tower returns to normal, the airflow velocity at the inlet returns to normal, the inlet plate is pushed back to its limit position, and the filter plate covers the outlet, filtering out impurities.

[0015] Furthermore, it also includes a high-salinity wastewater treatment device, with the outlet connected to the high-salinity wastewater treatment device. The high-salinity wastewater treatment device can effectively utilize the high-salinity wastewater, preventing waste.

[0016] Furthermore, it also includes an incineration device, with the gas outlet connected to the incineration device. Some carbon monoxide and organic gases remain in the gas, which can be removed through incineration.

[0017] Furthermore, the catalytic hydrolysis tank includes a tank body, a nozzle, and a permeable membrane. The tank body is provided with a water inlet, an air outlet, and an exhaust outlet. The nozzle is connected to the water inlet. Multiple permeable membranes are provided, and the nozzle cooperates with the permeable membranes. The air outlet is aligned with the permeable membrane, and a catalyst is placed inside the permeable membrane. Water begins to enter through the water inlet, and the nozzle is positioned between two permeable membranes. The nozzle sprays water, sprinkling it onto the catalyst inside the permeable membrane. When gas enters from the air outlet, the gas impacts the permeable membrane, passes through the permeable membrane, and comes into contact with the catalyst, causing a reaction. This mechanism makes the catalytic reaction more complete.

[0018] Furthermore, it also includes a phosgene detection device, one end of which is connected to the exhaust port and the other end of which is connected to the air inlet. The phosgene detection device is provided with a return end, which is connected to the air outlet.

[0019] The phosgene detection device can check whether the gas coming out of the catalytic hydrolysis tank contains phosgene, to prevent phosgene from being not completely treated. If it contains phosgene, it will return to the gas flow port from the reflux end for catalytic hydrolysis again. If it does not contain phosgene, it will go to the alkali destruction tower from the other end.

[0020] Furthermore, the alkali destruction tower is provided with three sections. The first gas outlet of the first alkali destruction tower is connected to the gas inlet of the second alkali destruction tower, the second gas outlet of the second alkali destruction tower is connected to the third gas inlet of the third alkali destruction tower, the first liquid outlet of the first alkali destruction tower is connected to the liquid inlet of the second alkali destruction tower, the second liquid outlet of the second alkali destruction tower is connected to the third liquid inlet of the third alkali destruction tower, the third liquid outlet is connected to a high-salt wastewater treatment device, and the third gas outlet is connected to an incineration device. The three alkali destruction towers carry out the reaction layer by layer, making the reaction more thorough.

[0021] This solution provides a method for alkaline destruction of phosgenation tail gas, including the following steps:

[0022] Step S10: Pass the exhaust gas into the falling film absorber, which absorbs the hydrochloric acid in the exhaust gas to obtain treated gas one.

[0023] Step S20: Then, process gas one is introduced into the catalytic hydrolysis tank, and phosgene in it is destroyed by catalytic hydrolysis to obtain process gas two;

[0024] Step S30: The second treatment gas is introduced into the multi-stage alkali destruction tower. A 1%-10% dilute alkali solution is sent to the top of the alkali destruction tower through a transfer pump. After the pH value of the alkali solution drops to 7.5-10, it is automatically introduced into the alkali wastewater tank and then transported to the high-salt wastewater treatment device to generate inorganic salt solution and the third treatment gas through acid-base reaction.

[0025] Step S40: The inorganic salt solution is sent to the high-salt wastewater treatment device for treatment, and the treated gas is sent to the incineration device for treatment to remove unreacted carbon monoxide and organic matter and other combustible gases, so as to obtain the final gas and discharge it to the outside.

[0026] This method greatly improves the efficiency of exhaust gas treatment while reducing the production of high-salinity wastewater.

[0027] Furthermore, the dilute alkaline solution in step S30 is a 3.5%-4% sodium hydroxide solution. This concentration of sodium hydroxide solution allows for a more complete reaction with the exhaust gas.

[0028] Furthermore, in step S30, the alkaline solution is directly discharged after online monitoring confirms the pH is between 7.5 and 7.8. The company's total wastewater discharge per ton of product has been reduced from approximately 1 ton before implementation to approximately 0.38 tons, demonstrating significant effectiveness. Attached Figure Description

[0029] Figure 1 This is a structural diagram of a phosgenation tail gas alkaline destruction device during operation.

[0030] Figure 2 This is a structural diagram of a phosgenation tail gas alkali destruction device with the alkali destruction tower not in operation.

[0031] Figure 3 This is a structural diagram of the operation of the alkali destruction tower in a phosgenation tail gas alkali destruction device.

[0032] The reference numerals in the accompanying drawings include: 1. Catalytic hydrolysis tank; 101. Nozzle; 102. Catalyst; 103. Permeable membrane; 104. Water outlet; 2. Reflux end; 3. Through end; 4. First alkali destruction tower; 401. First gas outlet; 402. First liquid inlet; 403. Tray; 404. Baffle; 405. Slide plate; 406. Insertion plate; 407. Gas inlet plate; 408. Cleaning brush; 409. Connecting rod; 410. Filter plate; 411. ... 412. Air inlet; 413. Liquid outlet; 5. Second alkali destruction tower; 501. Second air outlet; 502. Second liquid inlet; 503. Second air inlet; 504. Second liquid outlet; 6. Third alkali destruction tower; 601. Third air outlet; 602. Third liquid inlet; 603. Third air inlet; 604. Third liquid outlet; 7. Falling film absorber; 8. Phosgene detection device; 9. Waste gas incineration device; 10. Alkali wastewater tank. Detailed Implementation

[0033] The basics are as follows: Figure 1 , Figure 2 As shown:

[0034] This solution provides a phosgenation tail gas alkaline destruction device, including a catalytic hydrolysis tank 1, a phosgene detection device 8, an alkaline destruction tower, a pH meter, and a falling film absorber 7. The falling film absorber 7, the catalytic hydrolysis tank 1, the phosgene detection device 8, the first alkaline destruction tower 4, the second alkaline destruction tower 5, the third alkaline destruction tower 6, and the pH meter are connected in sequence.

[0035] The alkali degradation tower includes a cleaning mechanism, a tower body, a tower plate 403, and a downcomer 412. The tower plate 403 is fixedly connected to the tower body, and the downcomer 412 is also fixedly connected. The tower body has an outlet, a liquid inlet, an air inlet, and a liquid outlet. The cleaning mechanism includes an inlet plate 407, a filter plate 410, and a cleaning brush 408. The inlet plate 407 and the filter plate 410 are fixedly connected at a certain angle. The connection between the inlet plate 407 and the filter plate 410 is rotatably connected to the tower body via a torque spring. When no gas enters from the inlet, the inlet plate 407 covers the inlet under the action of the torque spring, closing the inlet. The filter plate 410 passes through the brush needles of the cleaning brush 408. When gas is introduced, the gas causes the inlet plate 407 to rotate, simultaneously rotating the filter plate 410, causing the filter plate 410 to cover the liquid outlet, forming a filter screen effect. The cleaning brush 408 is fixedly connected to the tower body. It also includes a high-salinity wastewater treatment device, with the liquid outlet connected to the high-salinity wastewater treatment device. It also includes a waste gas incineration device 9, with the gas outlet connected to the waste gas incineration device 9.

[0036] It also includes an anti-flooding mechanism, which includes a connecting rod 409, a sliding plate 405, a baffle 404, and an insertion plate 406. The tower plate 403 is provided with a groove, the insertion plate 406 is slidably connected to the groove, the insertion plate 406 is fixedly connected to the sliding plate 405, the baffle 404 is fixedly connected to the tower body, and the baffle 404 is slidably connected to the sliding plate 405. One end of the connecting rod 409 is hingedly connected to the sliding plate 405, and the other end is hingedly connected to the filter plate 410.

[0037] The catalytic hydrolysis tank 1 includes a tank body, a nozzle 101, and a permeable membrane 103. The tank body is provided with a water inlet 104, an air outlet, and an exhaust outlet. The nozzle 101 is connected to the water inlet 104. There are 5 permeable membranes 103 and 3 nozzles 101. The permeable membranes 103 are fixed on the tank body from top to bottom to form a barrier-like structure. The nozzles 101 are located between two permeable membranes 103. The inner layer of the permeable membrane 103 is filled with catalyst 102. The air outlet is aligned with the permeable membrane 103.

[0038] It also includes a phosgene detection device, one end of which is connected to the exhaust port and the other end is connected to the air inlet. The phosgene detection device 8 is provided with a return end 2, which is connected to the air outlet.

[0039] The alkali destruction tower is provided with three outlets. The first outlet 401 of the first alkali destruction tower 4 is connected to the inlet of the second alkali destruction tower 5. The second outlet 501 of the second alkali destruction tower 5 is connected to the third inlet 603 of the third alkali destruction tower 6. The first liquid outlet 413 of the first alkali destruction tower 4 is connected to the liquid inlet of the second alkali destruction tower 5. The second liquid outlet 504 of the second alkali destruction tower 5 is connected to the third liquid inlet 602 of the third alkali destruction tower 6. The third liquid outlet 604 is connected to the high-salt wastewater treatment device. The third outlet 601 is connected to the waste gas incineration device 9.

[0040] In specific operation, the operator first passes the exhaust gas into the falling film absorber 7 to remove the hydrochloric acid in the exhaust gas, and then passes the gas into the catalytic hydrolysis tank 1. Water is introduced into the water outlet 104. The nozzle 101 is located between the two permeable membranes 103. The nozzle 101 sprays water onto the catalyst 102 inside the permeable membrane 103. When the gas is introduced from the gas outlet, the gas will impact the permeable membrane 103 and pass through the permeable membrane 103 to contact the catalyst 102 and react. The catalytic hydrolysis method destroys the phosgene in it. This mechanism makes the catalytic reaction more complete.

[0041] The gas then enters the phosgene detection device 8, which can check whether the gas coming out of the catalytic hydrolysis tank 1 contains phosgene to prevent phosgene from being not cleaned. If it contains phosgene, the phosgene returns to the gas flow port from the reflux end 2 for catalytic hydrolysis again. If it does not contain phosgene, it goes to the first alkali destruction tower 4 from the through end 3.

[0042] The gas is then introduced into the first alkali destruction tower 4. The gas enters through the first inlet 411, pushing open the inlet plate 407 and causing the filter plate 410 to rotate until it contacts and covers the liquid outlet, effectively filtering particles. Simultaneously, liquid enters through the first liquid inlet 402 at the top of the tower, creating a counter-current flow that increases the contact area and maximizes the reaction. The tower plate 403 slows the liquid's descent, further increasing the gas-liquid contact time. When the tail gas is completely treated, the device stops. The inlet plate 407 returns to its original position under the action of the torque spring, simultaneously causing the filter plate 410 to tilt upwards, contacting the brush needles of the cleaning brush 408. The brush needles penetrate the filter holes of the filter plate 410, cleaning away any adhering particles. This eliminates the need for personnel to disassemble the alkali destruction tower to replace the filter screen.

[0043] When flooding occurs in the alkali destruction tower, the gas at the bottom cannot pass through the liquid above, causing the pressure at the bottom to increase. This reduces the gas flow rate into the inlet, causing the inlet plate 407 to slowly move back due to the torque spring. Simultaneously, the filter plate 410 also begins to move. The filter plate 410 moves the connecting rod 409, which in turn moves the sliding plate 405. The sliding plate 405 pulls out the insertion plate 406. The insertion plate 406 is a thin plate with filter holes. Pulling out the insertion plate 406 makes the tower plate 403 longer and increases the number of filter holes, allowing the liquid to fall more easily. It also increases the gap between the downcomer 412 and the sliding plate 405, giving the liquid more space to pass through the gas, thus resolving the flooding problem. Once the gas pressure inside the tower returns to normal, the airflow velocity at the inlet returns to normal, and the inlet plate 407 is pushed back to its limit position. At the same time, the filter plate 410 covers the outlet, filtering out impurities.

[0044] The gas from the first alkali crushing tower 4 flows to the second inlet 503 of the second alkali crushing tower 5, while the liquid from the first alkali crushing tower 4 flows to the second liquid inlet 502 of the second alkali crushing tower 5, undergoing a secondary reaction. The gas from the second alkali crushing tower 5 flows to the third inlet 603 of the third alkali crushing tower 5, and the liquid from the second alkali crushing tower 5 flows to the third liquid inlet 602 of the third alkali crushing tower 6, undergoing a tertiary reaction. The three alkali crushing towers perform a layer-by-layer reaction, making the reaction more thorough. The gas exiting the third alkali crushing tower 6 still contains some residual carbon monoxide and organic matter, which can be removed by incineration in the waste gas incineration device 9. The high-salinity wastewater exiting the third alkali crushing tower 6 can be effectively utilized by a high-salinity wastewater treatment device, preventing waste.

[0045] This solution also provides a method for alkaline destruction of phosgenation tail gas, including the following steps:

[0046] Step S10: Pass the exhaust gas into the falling film absorber 7. The falling film absorber 7 absorbs the hydrochloric acid in the exhaust gas to obtain treated gas one.

[0047] Step S20: Then, process gas one is introduced into catalytic hydrolysis tank 1, and phosgene in it is destroyed by catalytic hydrolysis to obtain process gas two;

[0048] Step S30: The second treatment gas is introduced into the multi-stage alkali destruction tower. A 3.5%-4% dilute alkali solution is sent to the top of the alkali destruction tower through a transfer pump. After the pH value of the alkali solution drops to 7.5-7.8, it is automatically introduced into the alkali wastewater tank 10. It is then transported to the high-salt wastewater treatment device, where an inorganic salt solution and the third treatment gas are generated through an acid-base reaction.

[0049] Step S40: The inorganic salt solution is sent to the high-salt wastewater treatment device for treatment, and the treated gas is sent to the waste gas incineration device 9 for treatment to remove unreacted carbon monoxide and organic matter and other combustible gases, so as to obtain the final gas and discharge it to the outside.

[0050] This method significantly improves exhaust gas treatment efficiency and reduces the generation of high-salinity wastewater. Simultaneously, the reaction between the sodium hydroxide solution and the exhaust gas is more thorough at this concentration. Statistics show that the company's wastewater discharge per ton of product has decreased from approximately 1 ton before implementation to approximately 0.38 tons, demonstrating remarkable effectiveness.

[0051] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A device for alkaline destruction of phosgenation tail gas, comprising a catalytic hydrolysis tank (1), characterized in that, It also includes an alkali destruction tower, a pH meter and a falling film absorber, wherein the falling film absorber, the catalytic hydrolysis tank (1), the alkali destruction tower and the pH meter are connected in sequence; The alkali destruction tower includes a cleaning mechanism. The alkali destruction tower is equipped with a tower plate (403). The cleaning mechanism includes an air inlet plate (407), a filter plate (410), and a cleaning brush (408). The air inlet plate (407) is fixedly connected to the filter plate (410). The air inlet plate (407) is matched with the air inlet. The filter plate (410) is matched with the liquid outlet. The connection between the air inlet plate (407) and the filter plate (410) is rotatably connected to the tower body through a torque spring. The filter plate (410) is matched with the cleaning brush (408). The cleaning brush (408) is fixedly connected to the tower body.

2. The phosgenation tail gas alkaline destruction device according to claim 1, characterized in that, It also includes an anti-flooding mechanism, which includes a connecting rod (409), a sliding plate (405), a baffle (404), and an insertion plate (406). The tower plate (403) is provided with a groove, the insertion plate (406) is slidably connected to the groove, the insertion plate (406) is fixedly connected to the sliding plate (405), the baffle (404) is fixedly connected to the tower body, and the baffle (404) is slidably connected to the sliding plate (405). One end of the connecting rod (409) is hinged to the sliding plate (405), and the other end is hinged to the filter plate (410).

3. The phosgenation tail gas alkaline destruction device according to claim 1, characterized in that, It also includes a high-salinity wastewater treatment device, and the outlet is connected to the high-salinity wastewater treatment device.

4. The phosgenation tail gas alkaline destruction device according to claim 1, characterized in that, It also includes an incineration unit (9) and a high-salt wastewater treatment unit (10). The alkali destruction tower is provided with three towers: the first alkali destruction tower (4), the second alkali destruction tower (5), and the third alkali destruction tower (6). The first alkali destruction tower (4) is equipped with a first gas outlet (401) and a first liquid outlet (413). The second alkali destruction tower (5) is equipped with a second gas outlet (501) and a second liquid outlet (504). The third alkali destruction tower (6) is equipped with a third gas outlet (601) and a third liquid outlet (604). The first gas outlet (401) is connected to the gas inlet of the second alkali destruction tower (5). The second gas outlet (501) is connected to the gas inlet of the third alkali destruction tower (6). The third gas outlet (601) is connected to the incineration device (9); The first liquid outlet (413) is connected to the liquid inlet of the second alkali destruction tower (5). The second outlet (504) is connected to the inlet of the third alkali destruction tower (6). The third outlet (604) is connected to the high-salt wastewater treatment device.

5. The phosgenation tail gas alkaline destruction device according to claim 1, characterized in that, The catalytic hydrolysis tank (1) includes a tank body, a nozzle (101) and a permeable membrane (103). The tank body is provided with a water outlet (104), an air outlet and an exhaust outlet. The nozzle (101) is connected to the water outlet (104). Multiple permeable membranes (103) are provided. The nozzle (101) cooperates with the permeable membrane (103). The air outlet is aligned with the permeable membrane (103). A catalyst (102) is provided inside the permeable membrane (103).

6. The phosgenation tail gas alkaline destruction device according to claim 1, characterized in that, It also includes a phosgene detection device, one end of which is connected to the exhaust port and the other end of which is connected to the air inlet. The phosgene detection device is provided with a return end (2), which is connected to the air outlet.

7. A method for destroying the alkali in phosgenation tail gas, using the alkali destruction device for phosgenation tail gas according to any one of claims 1-6, characterized in that, Includes the following steps: step S10: Pass the exhaust gas into the falling film absorber. The falling film absorber absorbs the hydrochloric acid in the exhaust gas to obtain treated gas one. Step S20: Then, process gas one is introduced into the catalytic hydrolysis tank (1) and phosgene in it is destroyed by catalytic hydrolysis to obtain process gas two; Step S30: The second treatment gas is introduced into the multi-stage alkali destruction tower. A 1%-10% dilute alkali solution is sent to the top of the alkali destruction tower through a transfer pump. After the pH value of the alkali solution drops to 7.5-10, it is automatically introduced into the alkali wastewater tank and then transported to the high-salt wastewater treatment device to generate inorganic salt solution and the third treatment gas through acid-base reaction. Step S40: The inorganic salt solution is sent to the high-salt wastewater treatment device for treatment, and the treated gas is sent to the incineration device for treatment to remove unreacted carbon monoxide and organic combustible gases, and the final gas is obtained and discharged to the outside.

8. The method for alkaline destruction of phosgenation tail gas according to claim 7, characterized in that, The dilute alkaline solution in step S30 is a 3.5%-4% sodium hydroxide solution.

9. The method for alkaline destruction of phosgenation tail gas according to claim 7, characterized in that, In step S30, the alkaline solution is directly discharged after online monitoring shows the pH to be between 7.5 and 7.8.

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