A tail gas treatment device and process for m-xylylene diisocyanate production

Abstract

This invention relates to the field of exhaust gas treatment technology and discloses an exhaust gas treatment device and process for the production of isophthalic diisocyanate. The device includes a base plate, an absorption tower mounted on the upper side of the base plate, and a control component connected to the upper side of the absorption tower via a pipe. Two adsorption towers are connected to the two ends of the control component, respectively. A condensation component is connected to the upper sides of both adsorption towers via pipes, and a vacuum pump unit is connected to the other end of the condensation component. The absorption tower includes an absorption tower body, a photocatalytic component, a first carrier plate, a demister, an inlet pipe, a spray mechanism, and a third carrier plate. This invention achieves thorough purification of industrial exhaust gas containing recalcitrant pollutants such as isocyanate, aniline, and phosgene through a multi-stage synergistic purification path of photocatalytic deep oxidation – alkaline absorption and neutralization – adsorbent fine treatment. This systematically solves the problem of insufficient efficiency of single treatment methods and ensures stable and compliant emissions of exhaust gas.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas treatment technology, specifically to an exhaust gas treatment device and process for the production of isophthalic diisocyanate. Background Technology

[0002] The traditional phosgene process for producing xylene diisocyanate (XDI) generates a complex and highly hazardous waste gas. This waste gas is a typical multi-pollutant complex system, mainly containing: highly toxic and reactive organic compounds such as unreacted isocyanate monomers, toxic aniline derivatives, and a wide variety of volatile organic compounds (VOCs); and highly corrosive and toxic inorganic compounds, primarily hydrogen chloride (HCl) and trace amounts of phosgene (COCl2). These pollutants collectively contribute to the multiple hazards of the waste gas: it is not only highly toxic, corrosive, and irritating, but some VOCs also exhibit photochemical activity, easily triggering secondary pollution. Improper emission control will cause serious and lasting damage to the atmospheric environment, the health of operators, and the surrounding ecosystem.

[0003] Currently, common technologies for treating such chemical waste gases include combinations of conventional technologies such as alkaline spray absorption, activated carbon adsorption, and thermal incineration. However, these traditional methods all have significant drawbacks when applied to XDI production waste gases: simple alkaline spraying has limited removal efficiency for organic components and generates large amounts of saline wastewater; activated carbon adsorption requires frequent regeneration or replacement, resulting in high operating costs and difficult waste carbon disposal; incineration consumes extremely high energy and may produce secondary pollutants such as nitrogen oxides (NOx). Furthermore, existing technologies often employ single or simple series-connected treatment units, resulting in complex equipment, long process flows, low automation, and problems such as incomplete treatment, unstable operation, inability to recover resources, and high energy and material consumption. Summary of the Invention

[0004] The purpose of this invention is to provide a tail gas treatment device and process for the production of isophthalic diisocyanate, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a tail gas treatment device for the production of isophthalic diisocyanate, comprising a base plate, an absorption tower fixedly installed on the upper side of the base plate, a control component connected to the upper side of the absorption tower via a pipe, an adsorption tower one and an adsorption tower two respectively connected to the two ends of the control component, a condensation component connected to the upper side of both the adsorption tower one and the adsorption tower two via pipes, and a vacuum pump unit connected to the other end of the condensation component; The absorption tower includes an absorption tower body, a photocatalytic component, a first carrier plate, a demister, an air inlet pipe, a spray mechanism, and a third carrier plate. The absorption tower body is fixedly installed on the upper side of the base plate. Multiple sets of photocatalytic components are fixedly connected to the lower part of the absorption tower body. Multiple sets of first carrier plates are fixedly installed on the inner side of the absorption tower body. An air inlet pipe is connected to the lower outer side of the absorption tower body. A spray mechanism is also provided on the absorption tower body. The first carrier plate corresponds to the spray mechanism. Multiple sets of third carrier plates are provided on the inner side of the absorption tower body. The third carrier plate corresponds to the photocatalytic component. The exhaust gas enters through the intake pipe and is purified efficiently from bottom to top by photocatalysis from the lower photocatalytic component and alkaline spraying from the upper spraying mechanism.

[0006] Furthermore, the photocatalytic component includes a mounting housing, a medium-pressure ultraviolet mercury lamp, and a quartz glass sleeve. Multiple sets of mounting housings are fixedly connected to the lower outer side of the absorption tower. Medium-pressure ultraviolet mercury lamps are evenly distributed and fixedly connected to the inner side of the mounting housing. A quartz glass sleeve is provided on the outer side of the medium-pressure ultraviolet mercury lamp. The quartz glass sleeve is fixedly connected to the mounting housing. The medium-pressure ultraviolet mercury lamp and the quartz glass sleeve penetrate the absorption tower.

[0007] The gas then enters the photocatalytic reaction zone. Here, multiple photocatalytic components are arranged along the tower body. Ultraviolet light is generated by a medium-pressure ultraviolet mercury lamp, and the emitted ultraviolet light shines through a quartz glass sleeve onto the three surfaces of a carrier plate coated with a nitrogen-fluorine co-doped titanium dioxide or palladium catalyst coating. Under ultraviolet light excitation, the catalyst produces highly oxidizing active species, which deeply oxidize recalcitrant pollutants such as isocyanates, aniline organic compounds, and trace amounts of phosgene in the exhaust gas, decomposing them into small molecules such as carbon dioxide, water, and hydrogen chloride. Furthermore, the spraying mechanism includes a housing, an injection pipe, a heat exchanger, a circulating pump, a liquid supply pipe, a main spray pipe, branch spray pipes, and a second carrier plate. The bottom of the absorption tower is connected to the housing, and the outside of the housing is connected to the injection pipe. A circulating pump is fixedly connected to the bottom plate. The inlet of the circulating pump is connected to the housing through a pipe, and the outlet of the circulating pump is connected to the liquid supply pipe through a pipe. The upper part of the liquid supply pipe is connected to multiple sets of main spray pipes, and the main spray pipes are connected to evenly distributed branch spray pipes. Both the main spray pipes and the branch spray pipes are connected to evenly distributed spray heads. A heat exchanger is installed at the bottom of the absorption tower and inside the housing, and a second carrier plate is installed on the lower inner side of the absorption tower.

[0008] The gas stream, having completed catalytic oxidation, continues to rise and enters the alkali absorption zone. The spray mechanism then begins operation: a circulating pump draws alkali from the tank and delivers it via a supply pipe to the main and branch spray pipes located at the top of the tower, forming a uniform liquid curtain downwards through the spray nozzles. The rising exhaust gas and the falling alkali directly contact each other counter-currently in the packing zone. HCl produced by photocatalysis and residual acidic components in the gas stream are efficiently absorbed and neutralized by the alkali. Simultaneously, the spray washes away particulate matter in the gas. The alkali, after absorption, falls back to the tank at the bottom of the tower, where a heat exchanger cools it to maintain optimal absorption efficiency, and a circulating pump drives continuous circulation of the alkali. The purified gas passes through a demister at the top to remove entrained droplets. Furthermore, the control component includes solenoid valve one, a three-way pipe, and solenoid valve two. The top of the absorption tower is connected to the three-way pipe, and solenoid valve one and solenoid valve two are respectively installed on the lower two sides of the three-way pipe.

[0009] Furthermore, both adsorption tower one and adsorption tower two are recovery towers. Each recovery tower includes a recovery tower body, a steam pipe, a main steam pipe, a branch steam pipe, and a carrier plate four. Both ports of solenoid valve one and solenoid valve two are connected to the recovery tower body. A steam pipe is provided on the outside of the recovery tower body. Multiple sets of main steam pipes are connected to the steam pipes. Evenly distributed branch steam pipes are connected to the main steam pipes. Evenly distributed steam nozzles are installed on the main steam pipes and branch steam pipes. The main steam pipes penetrate the recovery tower body and extend into the inside of the recovery tower body. The branch steam pipes are located inside the recovery tower body. Multiple sets of carrier plates four are fixedly installed on the inside of the recovery tower body. The carrier plates four correspond to the main steam pipes and steam pipes.

[0010] After preliminary purification in the absorption tower, the gas enters the three-way pipe of the control component through the top pipe. During the conventional adsorption stage, solenoid valve two is open and solenoid valve one is closed. The gas enters the adsorption tower and flows through the carrier plate four inside. The carrier plate four is filled with ZIF-8 based composite particulate adsorbent, which has a high selective adsorption capacity for trace amounts of VOCs remaining in the exhaust gas, thus achieving deep purification of the gas and subsequent emission in compliance with standards. Furthermore, the condensation assembly includes a condensation shell, a condensation tube assembly, baffles, a recovery port, an outlet, and an inlet. The top of the recovery tower is connected to the inlet via a pipe. The lower side of the inlet is connected to the condensation shell. A condensation tube assembly is installed on the inner side of the condensation shell. Multiple evenly distributed baffles are installed on the condensation tube assembly. The lower side of the condensation shell is connected to the recovery port. The upper side of the other end of the condensation shell is connected to the outlet. The outlet is connected to a vacuum pump assembly via a pipe. The outer side of the condensation shell is fixedly connected to the base plate via a mounting plate. A condensate inlet and a condensate outlet are respectively provided at both ends of the condensation shell.

[0011] When the adsorbent in adsorption tower one approaches saturation, the system automatically switches to regeneration mode. At this time, solenoid valve two closes, and solenoid valve one opens. The subsequent purified gas is then switched to another adsorption system, adsorption tower two, which is in standby mode.

[0012] At this time, low-pressure saturated steam is introduced into the steam pipes at the two solenoid valves. The steam is ejected through the main steam pipe and the steam branch pipes extending into the tower, as well as the steam nozzles on them, directly heating the adsorbent bed inside the tower. Simultaneously, the vacuum pump unit starts, creating negative pressure at the top of the tower. Under the synergistic effect of "hot steam heating" and "vacuum low pressure," VOCs on the adsorbent are rapidly desorbed. Furthermore, a gas distributor is installed on the lower inner side of both the absorption tower and the recovery tower. The gas distributor includes a gas dispersion plate, a flow channel dummy, and a conical air inlet. The lower side of the gas dispersion plate is connected to the conical air inlet, and the inner side of the gas dispersion plate has a passage corresponding to the flow channel dummy. The inner side of the gas dispersion plate is provided with honeycomb-shaped holes.

[0013] The exhaust gas first enters the absorption tower from the bottom through the inlet pipe. The exhaust gas then flows through a gas distributor installed at the bottom, whose conical inlet and honeycomb-patterned gas dispersion plate ensure even gas distribution and upward flow. Furthermore, the fourth carrier plate is filled with ZIF-8 based composite particle adsorbent, and the lower inner side of the carrier plate of the absorption tower is coated with a nitrogen-fluorine co-doped titanium dioxide or palladium catalyst coating on three sides. The inner carrier plates one and two of the absorption tower are filled with multi-faceted hollow sphere packing.

[0014] The mixture of high-concentration VOC vapors and water vapors desorbed is drawn into the condenser assembly through a pipe at the top of the recovery tower by a vacuum pump. The mixed gas enters the condenser shell through the inlet and flows through the shell side of the condenser tube assembly. Simultaneously, a low-temperature refrigerant (such as chilled water or ethylene glycol solution) enters the tube side of the condenser tube assembly from the condensate inlet, and the two exchange heat counter-currently. The VOC vapors and water vapors are condensed into a liquid state.

[0015] After the gas-liquid mixture is turbulently passed through the baffle in the condenser shell, the condensate (containing organic solvents and water) is discharged from the recovery port at the bottom and collected for resource utilization. Uncondensed gases (mainly air and trace amounts of VOCs) are extracted by the vacuum pump unit. When the adsorbent in adsorption tower two approaches saturation, the system automatically switches to regeneration mode, solenoid valve two opens, solenoid valve one closes, and the subsequent purified gas is switched to another adsorption system adsorption tower one, which is in standby status.

[0016] A tail gas treatment process for the production of isophthalic diisocyanate includes the following steps: S1, Air Inlet: Production exhaust gas is introduced from the bottom of the absorption tower and first dispersed evenly by a gas distributor; S2, Photocatalysis: Gas flows upward through the photocatalytic reaction zone and is excited by ultraviolet light to the nitrogen-fluorine co-doped titanium dioxide or palladium catalyst loaded on the three surfaces of the carrier plate to perform deep oxidation and decomposition of organic pollutants in the exhaust gas. S3, Alkali spray: The oxidized gas continues to rise to the alkali absorption zone and comes into countercurrent contact with the alkali sprayed downward by the spraying mechanism to neutralize the acidic components and wash the particulate matter. The sprayed alkali is cooled and then recycled. S4. Adsorption: After the gas is absorbed by the alkaline solution, it enters the adsorption stage after the liquid droplets are removed by the demister. In the conventional adsorption mode, the gas enters the adsorption tower one through the open solenoid valve two, flows through the carrier plate four containing ZIF-8 based composite particle adsorbent, and is discharged after deep adsorption and purification to meet the standards. S5. Mode switching: When the adsorbent is close to saturation, switch to regeneration mode, close solenoid valve 2, open solenoid valve 1, and switch the airflow to standby adsorption tower 2; at the same time, introduce low-pressure saturated steam into saturated adsorption tower 1 and start the vacuum pump group, so that the adsorbent is desorbed under the synergistic effect of hot steam heating and vacuum low pressure. S6. The mixture of high-concentration VOCs and vapor generated by desorption is drawn into the condensation unit. After condensation, the condensate is discharged from the recovery port for recovery, and the uncondensed gas is discharged by the vacuum pump unit.

[0017] Compared with the prior art, the present invention provides a tail gas treatment device and process for the production of isophthalic diisocyanate, which has the following beneficial effects: 1. This invention achieves thorough purification of industrial exhaust gas containing recalcitrant pollutants such as isocyanates, aniline, and phosgene through a multi-stage synergistic purification pathway of "photocatalytic deep oxidation - alkaline absorption and neutralization - adsorbent fine treatment." The photocatalytic stage efficiently decomposes large organic molecules, followed by alkaline spraying to neutralize the generated acidic gases and wash away particulate matter. Finally, a high-performance adsorbent ensures the deep removal of trace amounts of VOCs, thus systematically solving the problem of insufficient efficiency of single treatment methods and ensuring stable and compliant emissions of exhaust gas.

[0018] 2. This invention employs a combined "hot steam heating" and "vacuum low pressure" adsorbent regeneration technology, coupled with a condensation recovery unit. This design not only enables rapid and thorough desorption of VOCs, significantly restoring adsorbent capacity and extending its service life, but also condenses the desorbed high-concentration organic components into liquid for recovery, achieving resource utilization of pollutants. Simultaneously, the vacuum environment effectively prevents the leakage of harmful gases, resulting in both good environmental and economic benefits. Attached Figure Description

[0019] Figure 1This is a three-dimensional structural diagram of the present invention; Figure 2 This is a three-dimensional structural schematic diagram of the present invention from another angle; Figure 3 This is a partial three-dimensional structural schematic diagram of the present invention; Figure 4 This is a three-dimensional structural diagram of the absorption tower of the present invention; Figure 5 This is a three-dimensional structural diagram of the absorption tower of the present invention from another angle; Figure 6 This is a cross-sectional three-dimensional structural diagram of the absorption tower of the present invention; Figure 7 For the present invention Figure 6 Enlarged view of point A in the middle; Figure 8 This is a three-dimensional structural diagram of the absorption tower of the present invention cut from another angle; Figure 9 This is a partial three-dimensional structural diagram of the spraying mechanism of the present invention; Figure 10 This is a three-dimensional structural schematic diagram of the photocatalytic component of the present invention; Figure 11 This is a partial cross-sectional three-dimensional structural diagram of the photocatalytic component of the present invention; Figure 12 This is an exploded three-dimensional structural diagram of the gas distributor of the present invention; Figure 13 This is a three-dimensional exploded view of the gas distributor of the present invention from another angle; Figure 14 This is a three-dimensional structural diagram of the control component of the present invention; Figure 15 This is a three-dimensional structural diagram of the recovery tower of the present invention; Figure 16 For the present invention Figure 15 Enlarged view of point B in the middle; Figure 17 This is a cross-sectional three-dimensional structural diagram of the condensation component of the present invention.

[0020] In the diagram: 1. Base plate; 2. Absorption tower; 21. Absorption tower body; 22. Photocatalytic module; 221. Mounting shell; 222. Medium-pressure ultraviolet mercury lamp; 223. Quartz glass sleeve; 23. Carrier plate one; 24. Demister; 25. Inlet pipe; 26. Spray mechanism; 261. Box body; 262. Injection pipe; 263. Heat exchanger; 264. Circulating pump; 265. Liquid supply pipe; 266. Main spray pipe; 267. Spray branch pipe; 268. Carrier plate two; 27. Carrier plate three; 3. Adsorption tower one; 4. Recovery tower; 41. Recovery tower body; 42. Steam pipe; 43. Steam main pipe; 44. Steam branch pipe; 45. Carrier plate four; 5. Vacuum pump set; 6. Condensation assembly; 61. Condensation shell; 62. Condensation tube assembly; 63. Baffle; 64. Recovery port; 65. Gas outlet; 66. Gas inlet; 7. Gas distributor; 71. Gas dispersion plate; 72. Flow channel dummy; 73. Conical gas inlet; 8. Control assembly; 81. Solenoid valve one; 82. T-pipe; 83. Solenoid valve two; 9. Adsorption tower two. Detailed Implementation

[0021] 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.

[0022] Example

[0023] Please see Figures 1-17 A tail gas treatment device for the production of isophthalic diisocyanate includes a base plate 1, an absorption tower 2 fixedly installed on the upper side of the base plate 1, a control component 8 connected to the upper side of the absorption tower 2 through a pipe, an adsorption tower 3 and an adsorption tower 9 connected to the two ends of the control component 8 respectively, a condensation component 6 connected to the upper side of the adsorption tower 3 and the adsorption tower 9 through a pipe, and a vacuum pump group 5 connected to the other end of the condensation component 6. The absorption tower 2 includes an absorption tower body 21, a photocatalytic component 22, a first carrier plate 23, a demister 24, an air inlet pipe 25, a spray mechanism 26, and a third carrier plate 27. The absorption tower body 21 is fixedly installed on the upper side of the bottom plate 1. Multiple sets of photocatalytic components 22 are fixedly connected to the lower part of the absorption tower body 21. Multiple sets of first carrier plates 23 are fixedly installed on the inner side of the absorption tower body 21. The air inlet pipe 25 is connected to the lower outer side of the absorption tower body 21. A spray mechanism 26 is also provided on the absorption tower body 21. The first carrier plate 23 corresponds to the spray mechanism 26. Multiple sets of third carrier plates 27 are provided on the inner side of the absorption tower body 21. The third carrier plate 27 corresponds to the photocatalytic component 22. The exhaust gas enters through the intake pipe 25 and is purified efficiently from bottom to top by photocatalysis through the lower photocatalytic component 22 and alkaline spraying through the upper spraying mechanism 26.

[0024] Furthermore, the photocatalytic component 22 includes a mounting housing 221, a medium-pressure ultraviolet mercury lamp 222, and a quartz glass sleeve 223. Multiple sets of mounting housings 221 are fixedly connected to the lower outer side of the absorption tower body 21. Medium-pressure ultraviolet mercury lamps 222 are evenly distributed and fixedly connected to the inner side of the mounting housings 221. Quartz glass sleeves 223 are provided on the outer side of the medium-pressure ultraviolet mercury lamps 222. The quartz glass sleeves 223 are fixedly connected to the mounting housings 221. The medium-pressure ultraviolet mercury lamps 222 and the quartz glass sleeves 223 penetrate the absorption tower body 21.

[0025] The gas then enters the photocatalytic reaction zone. Here, multiple photocatalytic components 22 are arranged along the tower body. Ultraviolet light is generated by a medium-pressure ultraviolet mercury lamp 222, and the emitted ultraviolet light passes through a quartz glass sleeve 223 to irradiate the surface of a carrier plate 27 coated with a nitrogen-fluorine co-doped titanium dioxide or palladium catalyst coating. Under ultraviolet light excitation, the catalyst produces highly oxidizing active species, which deeply oxidizes recalcitrant pollutants such as isocyanates, aniline organics, and trace amounts of phosgene in the exhaust gas, decomposing them into small molecules such as carbon dioxide, water, and hydrogen chloride. Furthermore, the spraying mechanism 26 includes a housing 261, an injection pipe 262, a heat exchanger 263, a circulating pump 264, a liquid supply pipe 265, a main spray pipe 266, a branch spray pipe 267, and a carrier plate 268. The bottom of the absorption tower 21 is connected to the housing 261, and the outside of the housing 261 is connected to the injection pipe 262. The circulating pump 264 is fixedly connected to the bottom plate 1, and the inlet of the circulating pump 264 is connected to the housing 261 through a pipe. The outlet of pump 264 is connected to supply pipe 265 through a pipeline. The upper part of supply pipe 265 is connected to multiple sets of spray main pipes 266. Spray branch pipes 267 are evenly distributed on the spray main pipes 266. Spray heads are evenly distributed on both the spray main pipes 266 and the spray branch pipes 267. Heat exchangers 263 are installed at the bottom of absorption tower body 21 and inside the box body 261. Carrier plate 268 is installed on the lower inner side of absorption tower body 21.

[0026] The gas stream, having completed catalytic oxidation, continues to rise and enters the alkali absorption zone. The spray mechanism 26 begins operation: the circulating pump 264 draws alkali from the tank 261 and delivers it via the supply pipe 265 to the main spray pipe 266 and branch spray pipes 267 located at the top of the tower, forming a uniform liquid curtain downwards through the spray nozzles. The rising exhaust gas and the falling alkali directly contact each other counter-currently in the packing zone. HCl produced by photocatalysis and residual acidic components in the gas stream are efficiently absorbed and neutralized by the alkali. Simultaneously, the spray liquid washes away particulate matter in the gas. The alkali after absorption falls back to the tank 261 at the bottom of the tower, where the heat exchanger 263 cools it to maintain optimal absorption efficiency, and the circulating pump 264 drives continuous circulation of the alkali. The purified gas passes through the demister 24 at the top to remove entrained droplets. Furthermore, the control component 8 includes a first solenoid valve 81, a three-way pipe 82, and a second solenoid valve 83. The top of the absorption tower body 21 is connected to the three-way pipe 82, and the first solenoid valve 81 and the second solenoid valve 83 are respectively installed on the lower two sides of the three-way pipe 82.

[0027] Furthermore, both adsorption tower 1 (3) and adsorption tower 2 (9) are recovery towers 4. The recovery tower 4 includes a recovery tower body 41, a steam pipe 42, a main steam pipe 43, a steam branch pipe 44, and a carrier plate 45. The two ports of solenoid valve 1 (81) and solenoid valve 2 (83) are connected to the recovery tower body 41. A steam pipe 42 is provided on the outside of the recovery tower body 41. Multiple sets of main steam pipes 43 are connected to the steam pipe 42. Evenly distributed steam branch pipes 44 are connected to the main steam pipes 43. Evenly distributed steam nozzles are installed on the main steam pipes 43 and the steam branch pipes 44. The main steam pipes 43 penetrate the recovery tower body 41 and extend into the inside of the recovery tower body 41. The steam branch pipes 44 are located inside the recovery tower body 41. Multiple sets of carrier plates 45 are fixedly installed on the inside of the recovery tower body 41. The carrier plates 45 correspond to the main steam pipes 43 and the steam pipes 42.

[0028] After preliminary purification by absorption tower 2, the gas enters the three-way pipe 82 of control component 8 through the top pipe. During the normal adsorption stage, solenoid valve 2 83 is open and solenoid valve 1 81 is closed. The gas enters adsorption tower 3 and flows through the carrier plate 45 inside. The carrier plate 45 is filled with ZIF-8 based composite particulate adsorbent, which has a high selective adsorption capacity for trace amounts of VOCs remaining in the exhaust gas, thus deeply purifying the gas and allowing it to be discharged in compliance with standards. Furthermore, the condensation assembly 6 includes a condensation shell 61, a condensation tube assembly 62, a baffle plate 63, a recovery port 64, an outlet 65, and an inlet 66. The top of the recovery tower body 41 is connected to the inlet 66 via a pipe. The condensation shell 61 is connected to the lower side of the inlet 66. The condensation tube assembly 62 is installed inside the condensation shell 61. Multiple baffle plates 63 are evenly distributed on the condensation tube assembly 62. The recovery port 64 is connected to the lower side of the condensation shell 61. The outlet 65 is connected to the upper side of the other end of the condensation shell 61. The outlet 65 is connected to the vacuum pump assembly 5 via a pipe. The outer side of the condensation shell 61 is fixedly connected to the base plate 1 via an mounting plate. A condensate inlet and a condensate outlet are respectively provided at both ends of the condensation shell 61.

[0029] When the adsorbent in adsorption tower 3 approaches saturation, the system automatically switches to regeneration mode. At this time, solenoid valve 83 closes and solenoid valve 81 opens. The subsequent purified gas is switched to another adsorption system, adsorption tower 9, which is in standby mode.

[0030] At this time, low-pressure saturated steam is introduced into the steam pipe 42 at solenoid valve 283. The steam is ejected through the main steam pipe 43 and the steam branch pipe 44 extending into the tower and the steam nozzles on them, directly heating the adsorbent bed in the tower. Simultaneously, the vacuum pump group 5 starts, creating a negative pressure at the top of the tower. Under the synergistic effect of "hot steam heating" and "vacuum low pressure", VOCs on the adsorbent are rapidly desorbed; Furthermore, a gas distributor 7 is installed on the lower inner side of both the absorption tower body 21 and the recovery tower body 41. The gas distributor 7 includes a gas dispersion plate 71, a flow channel dummy 72, and a conical air inlet 73. The lower side of the gas dispersion plate 71 is connected to the conical air inlet 73. The inner side of the gas dispersion plate 71 is provided with a passage corresponding to the flow channel dummy 72, and the inner side of the gas dispersion plate 71 is provided with honeycomb-shaped holes.

[0031] The exhaust gas first enters from the lower part of the absorption tower body 21 through the inlet pipe 25. The exhaust gas first flows through the gas distributor 7 installed at the lower part, and the conical inlet 73 and the gas dispersion plate 71 with honeycomb holes of the gas distributor 7 make the gas evenly distributed and flow upward. Furthermore, the fourth carrier plate 45 is filled with ZIF-8 based composite particle adsorbent, the third carrier plate 27 on the lower inner side of the absorption tower body 21 is coated with a nitrogen-fluorine co-doped titanium dioxide or palladium catalyst coating, and the first carrier plate 23 and the second carrier plate 268 on the inner side of the absorption tower body 21 are filled with multi-faceted hollow sphere packing.

[0032] The mixture of high-concentration VOC vapors and water vapors desorbed is drawn into the condenser assembly 6 from the top of the recovery tower body 41 by the vacuum pump unit 5. The mixed gas enters the condenser shell 61 through the inlet 66 and flows through the shell side of the condenser tube assembly 62. At the same time, a low-temperature refrigerant (such as chilled water or ethylene glycol solution) enters the tube side of the condenser tube assembly 62 from the condensate inlet, and the two undergo countercurrent heat exchange. The VOC vapors and water vapors are condensed into liquid.

[0033] After the gas-liquid mixture is turbulently passed through the baffle 63 in the condenser shell 61, the condensate (containing organic solvents and water) is discharged from the recovery port 64 at the bottom and collected for resource utilization. The uncondensed gas (mainly air and trace amounts of VOCs) is extracted by the vacuum pump group 5. When the adsorbent in the second adsorption tower 9 approaches saturation, the system automatically switches to regeneration mode, the second solenoid valve 83 opens, the first solenoid valve 81 closes, and the subsequent purified gas is switched to another adsorption system adsorption tower 3, which is in standby status.

[0034] A tail gas treatment process for the production of isophthalic diisocyanate includes the following steps: S1, Air Inlet: Production exhaust gas enters from the bottom of the absorption tower 21 and is first evenly dispersed by the gas distributor 7; S2, Photocatalysis: Gas flows upward through the photocatalytic reaction zone and is excited by ultraviolet light to the nitrogen-fluorine co-doped titanium dioxide or palladium catalyst loaded on the surface of the three-27 carrier plate to deeply oxidize and decompose organic pollutants in the exhaust gas. S3, Alkali spraying: The oxidized gas continues to rise to the alkali absorption zone and comes into countercurrent contact with the alkali sprayed downward by the spraying mechanism 26 to neutralize the acidic components and wash the particulate matter. The sprayed alkali is cooled and then recycled. S4. Adsorption: After the gas is absorbed by the alkaline solution, it enters the adsorption stage after the liquid droplets are removed by the demister 24. In the conventional adsorption mode, the gas enters the adsorption tower 3 through the open solenoid valve 283, flows through the carrier plate 45 containing ZIF-8 based composite particle adsorbent, and is discharged after deep adsorption and purification to meet the standards. S5. Mode switching: When the adsorbent is close to saturation, switch to regeneration mode, close solenoid valve 2 83, open solenoid valve 1 81, and switch the airflow to standby adsorption tower 2 9; at the same time, introduce low-pressure saturated steam into saturated adsorption tower 1 3 and start vacuum pump group 5, so that the adsorbent is desorbed under the combined action of hot steam heating and vacuum low pressure. S6. The mixture of high-concentration VOCs and vapor generated by desorption is drawn into the condensation component 6. After condensation, the condensate is discharged and recovered from the recovery port 64, and the uncondensed gas is discharged by the vacuum pump group 5.

[0035] The specific usage and function of this embodiment are as follows: The exhaust gas first enters from the lower part of the absorption tower body 21 through the inlet pipe 25. The exhaust gas first flows through the gas distributor 7 installed at the lower part, and the conical inlet 73 and the gas dispersion plate 71 with honeycomb holes in the gas distributor 7 make the gas evenly distributed and flow upward.

[0036] The gas then enters the photocatalytic reaction zone. Here, multiple photocatalytic components 22 are arranged along the tower body. Ultraviolet light is generated by a medium-pressure ultraviolet mercury lamp 222, and the emitted ultraviolet light passes through a quartz glass sleeve 223 to irradiate the surface of a carrier plate 27 coated with a nitrogen-fluorine co-doped titanium dioxide or palladium catalyst coating. Under ultraviolet light excitation, the catalyst produces highly oxidizing active species, which deeply oxidize recalcitrant pollutants such as isocyanates, aniline organic compounds, and trace amounts of phosgene in the exhaust gas, decomposing them into small molecules such as carbon dioxide, water, and hydrogen chloride.

[0037] The gas stream, having completed catalytic oxidation, continues to rise and enters the alkali absorption zone. The spray mechanism 26 begins operation: the circulating pump 264 draws alkali from the tank 261 and delivers it via the supply pipe 265 to the main spray pipe 266 and branch spray pipes 267 located at the top of the tower, forming a uniform liquid curtain downwards through the spray nozzles. The rising exhaust gas and the falling alkali directly contact each other counter-currently in the packing zone. HCl produced by photocatalysis and residual acidic components in the gas stream are efficiently absorbed and neutralized by the alkali. Simultaneously, the spray liquid washes away particulate matter in the gas. The alkali after absorption falls back to the tank 261 at the bottom of the tower, where the heat exchanger 263 cools it to maintain optimal absorption efficiency, and the circulating pump 264 drives continuous circulation of the alkali. The purified gas passes through the demister 24 at the top to remove entrained droplets.

[0038] After preliminary purification by absorption tower 2, the gas enters the three-way pipe 82 of control component 8 through the top pipe. During the normal adsorption stage, solenoid valve 2 83 is open and solenoid valve 1 81 is closed. The gas enters adsorption tower 3 and flows through the carrier plate 45 inside. The carrier plate 45 is filled with ZIF-8 based composite particulate adsorbent, which has a high selective adsorption capacity for trace amounts of VOCs remaining in the exhaust gas, thus achieving deep purification of the gas and subsequent emission in compliance with standards.

[0039] When the adsorbent in adsorption tower 3 approaches saturation, the system automatically switches to regeneration mode. At this time, solenoid valve 83 closes and solenoid valve 81 opens. The subsequent purified gas is switched to another adsorption system, adsorption tower 9, which is in standby mode.

[0040] At this time, low-pressure saturated steam is introduced into the steam pipe 42 at solenoid valve 2 (83). The steam is ejected through the main steam pipe 43 and the steam branch pipe 44 extending into the tower, as well as the steam nozzles on them, directly heating the adsorbent bed inside the tower. Simultaneously, the vacuum pump group 5 is started, creating a negative pressure at the top of the tower. Under the synergistic effect of "hot steam heating" and "vacuum low pressure," VOCs on the adsorbent are rapidly desorbed.

[0041] The mixture of high-concentration VOC vapors and water vapors desorbed is drawn into the condenser assembly 6 from the top of the recovery tower body 41 by the vacuum pump unit 5. The mixed gas enters the condenser shell 61 through the inlet 66 and flows through the shell side of the condenser tube assembly 62. At the same time, a low-temperature refrigerant (such as chilled water or ethylene glycol solution) enters the tube side of the condenser tube assembly 62 from the condensate inlet, and the two undergo countercurrent heat exchange. The VOC vapors and water vapors are condensed into liquid.

[0042] After the gas-liquid mixture is turbulently passed through the baffle 63 in the condenser shell 61, the condensate (containing organic solvents and water) is discharged from the recovery port 64 at the bottom and collected for resource utilization. The uncondensed gas (mainly air and trace amounts of VOCs) is extracted by the vacuum pump group 5. When the adsorbent in the second adsorption tower 9 approaches saturation, the system automatically switches to regeneration mode, the second solenoid valve 83 opens, the first solenoid valve 81 closes, and the subsequent purified gas is switched to another adsorption system adsorption tower 3 that is in standby mode, and so on in a continuous cycle.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A tail gas treatment device for the production of isophthalic diisocyanate, comprising a base plate (1), characterized in that: An absorption tower (2) is fixedly installed on the upper side of the base plate (1). A control component (8) is connected to the upper side of the absorption tower (2) through a pipe. Adsorption tower one (3) and adsorption tower two (9) are connected to the two ends of the control component (8) respectively. A condensation component (6) is connected to the upper side of both adsorption tower one (3) and adsorption tower two (9) through a pipe. A vacuum pump group (5) is connected to the other end of the condensation component (6). The absorption tower (2) includes an absorption tower body (21), a photocatalytic component (22), a first carrier plate (23), a demister (24), an air inlet pipe (25), a spray mechanism (26), and a third carrier plate (27). The absorption tower body (21) is fixedly installed on the upper side of the bottom plate (1). Multiple sets of photocatalytic components (22) are fixedly connected to the lower part of the absorption tower body (21). Multiple sets of first carrier plates (23) are fixedly installed on the inner side of the absorption tower body (21). The air inlet pipe (25) is connected to the lower outer side of the absorption tower body (21). A spray mechanism (26) is also provided on the absorption tower body (21). The first carrier plate (23) corresponds to the spray mechanism (26). Multiple sets of third carrier plates (27) are provided on the inner side of the absorption tower body (21). The third carrier plate (27) corresponds to the photocatalytic component (22). The exhaust gas enters through the intake pipe (25) and is purified efficiently from bottom to top by photocatalysis of the lower photocatalytic component (22) and alkaline spraying of the upper spraying mechanism (26).

2. The tail gas treatment device for the production of isophthalic diisocyanate according to claim 1, characterized in that: The photocatalytic component (22) includes a mounting housing (221), a medium-pressure ultraviolet mercury lamp (222), and a quartz glass sleeve (223). Multiple sets of mounting housings (221) are fixedly connected to the lower outer side of the absorption tower body (21). Medium-pressure ultraviolet mercury lamps (222) are fixedly connected to the inner side of the mounting housing (221). A quartz glass sleeve (223) is provided on the outer side of the medium-pressure ultraviolet mercury lamp (222). The quartz glass sleeve (223) is fixedly connected to the mounting housing (221). The medium-pressure ultraviolet mercury lamp (222) and the quartz glass sleeve (223) penetrate the absorption tower body (21).

3. The tail gas treatment device for the production of isophthalic diisocyanate according to claim 2, characterized in that: The spraying mechanism (26) includes a housing (261), an injection pipe (262), a heat exchanger (263), a circulating pump (264), a liquid supply pipe (265), a main spray pipe (266), a branch spray pipe (267), and a second carrier plate (268). The bottom of the absorption tower (21) is connected to the housing (261), and the outside of the housing (261) is connected to the injection pipe (262). The circulating pump (264) is fixedly connected to the bottom plate (1), and the inlet of the circulating pump (264) is connected to the housing (261) through a pipe. The outlet of the circulating pump (264) is connected to the supply pipe (265) through a pipe. The upper part of the supply pipe (265) is connected to multiple sets of spray main pipes (266). The spray main pipes (266) are connected to evenly distributed spray branch pipes (267). The spray main pipes (266) and the spray branch pipes (267) are all connected to evenly distributed spray heads. The bottom of the absorption tower body (21) and the inner side of the box body (261) are equipped with heat exchangers (263). The lower inner side of the absorption tower body (21) is equipped with a carrier plate (268).

4. The tail gas treatment device for the production of isophthalic diisocyanate according to claim 3, characterized in that: The control component (8) includes a solenoid valve one (81), a three-way pipe (82), and a solenoid valve two (83). The top of the absorption tower body (21) is connected to the three-way pipe (82), and the solenoid valve one (81) and the solenoid valve two (83) are respectively installed on the lower two sides of the three-way pipe (82).

5. The tail gas treatment device for the production of isophthalic diisocyanate according to claim 4, characterized in that: Both adsorption tower 1 (3) and adsorption tower 2 (9) are recovery towers (4). The recovery tower (4) includes a recovery tower body (41), a steam pipe (42), a main steam pipe (43), a steam branch pipe (44), and a carrier plate (45). The two ports of the solenoid valve 1 (81) and the solenoid valve 2 (83) are connected to the recovery tower body (41). A steam pipe (42) is provided on the outside of the recovery tower body (41). Multiple sets of main steam pipes (43) are connected to the steam pipes (42). 3) The upper part is connected to a uniformly distributed steam branch pipe (44). The steam main pipe (43) and the steam branch pipe (44) are both equipped with uniformly distributed steam nozzles. The steam main pipe (43) passes through the recovery tower body (41) and extends into the inner side of the recovery tower body (41). The steam branch pipe (44) is located inside the recovery tower body (41). Multiple sets of carrier plates (45) are fixedly installed on the inner side of the recovery tower body (41). The carrier plates (45) correspond to the steam main pipe (43) and the steam pipe (42).

6. The tail gas treatment device for the production of isophthalic diisocyanate according to claim 5, characterized in that: The condensation assembly (6) includes a condensation shell (61), a condensation tube assembly (62), a baffle (63), a recovery port (64), an outlet (65), and an inlet (66). The top of the recovery tower body (41) is connected to the inlet (66) through a pipe. The lower side of the inlet (66) is connected to the condensation shell (61). The inner side of the condensation shell (61) is equipped with a condensation tube assembly (62). Multiple baffles (63) are evenly distributed on the condensation tube assembly (62). The lower side of the condensation shell (61) is connected to the recovery port (64). The upper side of the other end of the condensation shell (61) is connected to the outlet (65). The outlet (65) is connected to the vacuum pump assembly (5) through a pipe. The outer side of the condensation shell (61) is fixedly connected to the base plate (1) through an mounting plate. The two ends of the condensation shell (61) are respectively provided with a condensate inlet and a condensate outlet.

7. The tail gas treatment device for the production of isophthalic diisocyanate according to claim 5, characterized in that: Gas distributors (7) are installed on the lower inner side of the absorption tower body (21) and the recovery tower body (41). The gas distributor (7) includes a gas dispersion plate (71), a flow channel dummy (72), and a conical air inlet (73). The lower side of the gas dispersion plate (71) is connected to the conical air inlet (73). The inner side of the gas dispersion plate (71) is provided with a passage corresponding to the flow channel dummy (72). The inner side of the gas dispersion plate (71) is provided with honeycomb-shaped holes.

8. The tail gas treatment device for the production of isophthalic diisocyanate according to claim 5, characterized in that: The fourth carrier plate (45) is filled with ZIF-8 based composite particle adsorbent. The third carrier plate (27) on the lower inner side of the absorption tower body (21) is coated with a nitrogen-fluorine co-doped titanium dioxide or palladium catalyst coating. The first carrier plate (23) and the second carrier plate (268) on the inner side of the absorption tower body (21) are filled with multi-faceted hollow sphere packing.

9. A tail gas treatment process for the production of isophthalic diisocyanate, applied to the tail gas treatment device for the production of isophthalic diisocyanate as described in any one of claims 1-8, characterized in that: Includes the following steps: S1, Air intake: Production tail gas is introduced from the bottom of the absorption tower (21) and first passes through the gas distributor (7) to be evenly dispersed; S2, Photocatalysis: Gas flows upward through the photocatalytic reaction zone and is excited by ultraviolet light to the nitrogen-fluorine co-doped titanium dioxide or palladium catalyst loaded on the surface of the three (27) carrier plate to perform deep oxidation and decomposition of organic pollutants in the exhaust gas. S3, Alkali spraying: The oxidized gas continues to rise to the alkaline absorption zone and comes into countercurrent contact with the alkaline sprayed downward by the spraying mechanism (26) to neutralize the acidic components and wash the particulate matter. The alkaline solution after spraying is cooled and then recycled. S4. Adsorption: After the gas is absorbed by the alkaline solution, it enters the adsorption stage after the liquid droplets are removed by the demister (24). In the conventional adsorption mode, the gas enters the adsorption tower (3) through the open solenoid valve (83), flows through the carrier plate (45) containing ZIF-8 based composite particle adsorbent, and is discharged after deep adsorption and purification. S5, Mode switching: When the adsorbent is close to saturation, switch to regeneration mode, close solenoid valve 2 (83), open solenoid valve 1 (81), and switch the airflow to standby adsorption tower 2 (9); at the same time, introduce low-pressure saturated steam into saturated adsorption tower 1 (3) and start vacuum pump group (5), so that the adsorbent is desorbed under the combined action of hot steam heating and vacuum low pressure. S6. The mixture of high-concentration VOCs and vapor generated by desorption is drawn into the condensation component (6). After condensation, the condensate is discharged from the recovery port (64) for recovery, and the uncondensed gas is discharged by the vacuum pump group (5).

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