Phosgene recovery system in production process of triphenyl isocyanate thiophosphate

Abstract

The utility model relates to the technical field of phosgene recovery, in particular to a phosgene recovery system in the production process of triphenyl isocyanate thiophosphate, which comprises a phosgene absorption tower and a phosgene desorption tower, a feeding hole of the phosgene absorption tower is connected with a gas distribution plate, the gas distribution plate is a cavity container with uniform micropores in the upper surface, and the gas distribution plate is arranged in the solvent tank; the action principles and structures of the phosgene absorption tower and the phosgene desorption tower are improved, so that excessive phosgene can be fully recovered, the resource utilization rate is increased, and the application prospect is wide.

Description

Technical Field

[0001] This utility model relates to the field of phosgene recovery technology, specifically to a phosgene recovery system in the production process of triphenyl isocyanate thiophosphate. Background Technology

[0002] Triphenyl isocyanate thiophosphate (TPTI), CAS: 4151-51-3, cures upon contact with water and air, and is therefore used as a curing agent for shoes, especially light-colored and white shoes. The final step in the synthesis of TPTI is the carbonylation reaction between triphenylamine thiophosphate (TPTA) and phosgene. This reaction typically occurs in a photochemical reactor and involves two steps: first, amidation of the amine, and second, dehydrochlorination to obtain the isocyanate. To ensure a high yield of TPTI and a low rate of byproduct formation, excess phosgene is usually added. Unreacted phosgene needs to be recovered for reuse.

[0003] Patent CN201420821402.3 discloses an apparatus for continuously recovering high-content phosgene from isocyanate production tail gas, comprising: an absorption tower, the top of which is connected to an induced draft fan to discharge residual gas to a tail gas treatment system; the top of the tower is also connected to a solvent storage tank to which solvent is supplied; the bottom of the tower is connected to a tail gas buffer tank; and the bottom of the tower is also connected to the top of a stripping tower to which a solvent solution after phosgene absorption is supplied. The internal structure of the absorption tower is not described; it can only be assumed that its basic principle is that the phosgene at the bottom of the tower and the eluent at the top move relative to each other, causing the phosgene to dissolve in the eluent. However, such absorption efficiency is relatively low, and it is impossible to determine whether the phosgene is completely absorbed. Excess phosgene that is not absorbed is directly discharged to the tail gas treatment system, resulting in poor recovery efficiency and resource waste. The stripping tower is only described as being heated before being fed to the top of the tower, suggesting that phosgene separation is achieved through distillation. Direct distillation is difficult to achieve complete separation, resulting in a reduced phosgene recovery rate. Furthermore, the solvent contains phosgene, which is not conducive to secondary utilization and poses safety risks.

[0004] Therefore, it is necessary to develop a phosgene recovery system for the production process of triphenyl isocyanate thiophosphate (TPTI) in order to fully recover excess phosgene, while recycling solvents to improve economic value and reduce safety risks. Utility Model Content

[0005] To address the aforementioned problems, this invention provides a phosgene recovery system for the production process of triphenyl isocyanate thiophosphate. By improving the working principle and structure of the phosgene absorption tower and phosgene desorption tower, it can fully recover excess phosgene, improve resource utilization, and has broad application prospects.

[0006] This invention provides a phosgene recovery system in the production process of triphenyl isocyanate thiophosphate, including a phosgene absorption tower and a phosgene desorption tower. The bottom of the phosgene absorption tower is provided with a solvent tank for storing inert solvent. The inlet of the phosgene absorption tower is connected to a gas distribution plate. The gas distribution plate is a cavity container with uniform micropores on its upper surface and is disposed inside the solvent tank.

[0007] Furthermore, the solvent tank is provided with a solution outlet, the height of which is lower than the height of the gas distribution plate inside the solvent tank. The solution outlet is connected to the sprayer and the phosgene desorption tower via pipelines, and a three-way flow meter is installed in the pipelines.

[0008] Furthermore, the sprayer is positioned above the solvent tank and is also connected to an inert solvent feed pipe.

[0009] Furthermore, the phosgene absorption tower is equipped with a first condenser and a second condenser, both of which are sieve plates filled with refrigerant.

[0010] Furthermore, the phosgene absorption tower also includes a first vacuum pump, which is used to deliver the gas between the first condenser and the second condenser to the gas distribution plate.

[0011] Furthermore, the phosgene desorption tower is provided with a first packing material, a second packing material, and a third packing material arranged from bottom to top, with a solution inlet provided between the first packing material and the second packing material; the solution inlet is connected to the solution outlet.

[0012] Furthermore, a secondary feed inlet is provided between the first packing and the second packing. The phosgene desorption tower also includes a bottom outlet and a heater. The heater heats the solution at the bottom outlet into steam and delivers it to the secondary feed inlet.

[0013] Furthermore, the phosgene desorption tower also includes a third vacuum pump, which is used to deliver the liquid between the second and third packing materials to the solution inlet.

[0014] The beneficial technical effects of this utility model are:

[0015] 1. This utility model provides a phosgene recovery system in the production process of triphenyl isocyanate thiophosphate. By improving the working principle and structure of the phosgene absorption tower and phosgene desorption tower, it can fully recover excess phosgene, improve resource utilization, and has broad application prospects.

[0016] 2. The use of gas distribution plates, condensers, and other devices specially designed for the phosgene recovery system in the production process of triphenyl isocyanate thiophosphate significantly improves the phosgene dissolution ratio and the stratified solvent recovery, ensuring the stability of the phosgene recovery process. The use of gas reflux and liquid spray phosgene absorption methods, as well as liquid reflux and gas lift phosgene desorption methods, simultaneously improves the efficiency of phosgene absorption and desorption, enabling continuous phosgene recovery. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the phosgene recovery system in the production process of triphenyl isocyanate thiophosphate according to this utility model.

[0018] Figure 2 This is a schematic diagram of the phosgene absorption tower of this utility model;

[0019] Figure 3 This is a schematic diagram of the phosgene desorption tower of this utility model;

[0020] Figure 4 This is a schematic diagram of the gas distribution plate of this utility model;

[0021] Reference numerals: 1-phosgene absorption tower, 111-first inlet, 112-gas distribution plate, 113-solvent tank, 114-solution outlet, 120-flow meter, 121-first conveying pipe, 122-second conveying pipe, 123-sprayer, 131-first vacuum pump, 132-third conveying pipe, 141-first condenser, 142-second condenser, 15-second vacuum pump, 2-phosgene desorption tower, 211-first packing, 212-second packing, 213-third packing, 221-bottom outlet, 222-fourth conveying pipe, 223-heater, 224-secondary inlet, 231-third vacuum pump, 232-fifth conveying pipe, 24-fourth vacuum pump; F1-reaction gas, F2-inert solvent, F3-hydrogen chloride, F4-phosgene. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Identical components are indicated by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "upper," and "lower" used in the following description refer to directions in the accompanying drawings, and the terms "bottom surface," "top surface," "inner," and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0023] Figure 1This is a schematic diagram of the phosgene recovery system in the production process of triphenyl isocyanate thiophosphate according to this invention. It includes a phosgene absorption tower 1 and a phosgene desorption tower 2. The material stream includes reaction gas F1, inert solvent F2, hydrogen chloride F3, and phosgene F4. Reaction gas F1 is the gaseous phase obtained after the TPTI synthesis reaction, which includes phosgene, hydrogen chloride, and inert solvent vapor. Inert solvent F2 is the solvent used for rinsing and adsorbing phosgene. The same solvent as that used in TPTI synthesis is selected. Hydrogen chloride F3 is a relatively pure hydrogen chloride gas obtained after separation, which can be collected and used for other purposes. Phosgene F4 is the product recovered by the phosgene recovery system of this invention, which can be collected and used for further reaction, etc.

[0024] Figure 2 This is a schematic diagram of the phosgene absorption tower 1 in a phosgene recovery system. The bottom of the phosgene absorption tower 1 is a solvent tank 113 for holding inert solvent. A gas distribution plate 112 is installed in the middle of the solvent tank 113, connected to the first inlet 111. The reaction gas F1 and the third conveying pipe 132 are both connected to the first inlet 111. The gas in the reaction gas F1 and the third conveying pipe 132 bubbles up from the gas distribution plate 112 and comes into contact with the inert solvent in the solvent tank 113. The gas distribution plate 112 is a specially designed device with features such as… Figure 4The structure shown has two arc surfaces and two straight surfaces on its sides. The arc surfaces are used to connect and fix with the tower wall of the phosgene absorption tower 1, and the straight surfaces allow space on its outer side for the inert solvent to move freely up and down in the solvent tank 113. Its upper surface is provided with dense and uniform micropores, and its interior is hollow. Under pressure, the gas inside the cavity can rise uniformly from the micropores on the upper surface, generating tiny bubbles to increase contact with the inert solvent and improve the phosgene absorption rate. The solution outlet 114 is located on the tower wall below the gas distribution plate 112. The solution outlet 114 is connected to one end of the first delivery pipe 121, and the other end of the first delivery pipe 121 is connected to a flow meter 120. The flow meter 120 is a special three-way valve that controls the flow rate and proportion to the second delivery pipe 122 and the sprayer 123. The sprayer 123 is also connected to a stream of inert solvent F2. The sprayer 123 is equipped with... Below the first condenser 141 and above the inert solvent in the solvent tank 113, a spray is used to spray the solution downwards in a spray-like manner. The first condenser 141 is located in the lower middle part of the phosgene absorption tower 1, and the second condenser 142 is located in the upper middle part of the phosgene absorption tower 1. The first condenser 141 and the second condenser 142 have the same structure, which is a sieve plate filled with refrigerant, and the refrigerant circulates with the external cold trap. One end of the third delivery pipe 132 is located on the tower wall between the first condenser 141 and the second condenser 142. A first vacuum pump 131 is installed in the pipeline of the third delivery pipe 132. The first vacuum pump 131 can control the flow rate and velocity of the gas flowing back from the first condenser 141 and the second condenser 142 to the first feed port 111. A second vacuum pump 15 is installed at the top of the phosgene absorption tower 1 to remove hydrogen chloride F3 from the top of the phosgene absorption tower 1.

[0025] Figure 3 This is a schematic diagram of the phosgene desorption tower 2 in a phosgene recovery system. Inside the phosgene desorption tower 2, from bottom to top, are arranged first packing 211, second packing 212, and third packing 213. All three types of packing are conjugate ring packings. The liquid inlet of the phosgene desorption tower 2 is located on the tower wall between the first packing 211 and the second packing 212, and is connected to both the second conveying pipe 122 and the fifth conveying pipe 232. The other end of the fifth conveying pipe 232 is located on the tower wall between the second packing 212 and the third packing 213. A third vacuum pump 231 is installed in the pipeline of the delivery pipe 232; the secondary feed port 224 is also located in the tower wall between the first packing 211 and the second packing 212. The bottom outlet 221 and the secondary feed port 224 are connected by a fourth delivery pipe 222. A heater 223 is installed in the pipeline of the fourth delivery pipe 222 to heat the liquid phase at the bottom of the phosgene desorption tower 2 to the gas phase and deliver it to the secondary feed port 224; a fourth vacuum pump 24 is installed at the top of the phosgene desorption tower 2 to extract phosgene F4 from the top of the tower.

[0026] The following describes the working principle of the phosgene recovery system in the production process of triphenyl isocyanate thiophosphate according to this invention:

[0027] Reactant gas F1 emits bubbles uniformly from gas distribution plate 112, where phosgene is dissolved by inert solvent. The inert solvent at the bottom has a relatively low phosgene concentration in the early stage and is pumped into sprayer 123 to wash downwards, which is used to adsorb phosgene in the gas phase in the tower. When the gas phase located below the second condenser 142 rises to the second condenser 142, the inert solvent vapor condenses. The gas phase between the first condenser 141 and the second condenser 142 contains only a low concentration of inert solvent vapor, hydrogen chloride and incompletely adsorbed phosgene. Then, a certain amount of gas is pumped back to gas distribution plate 112 by the first vacuum pump 131 in a certain proportion to increase the dissolution of phosgene. After a certain period of circulation, almost all the phosgene in the tower is dissolved by inert solvent. The second vacuum pump 15 removes the gas condensed by the first condenser 141. At this time, the inert solvent is also removed, leaving only high-purity hydrogen chloride F3.

[0028] At this time, the flow meter 120 can be adjusted so that the inert solvent containing phosgene dissolved in the solvent tank 113 is diverted to the phosgene desorption tower 2 in a certain proportion. The phosgene desorption tower 2 is equipped with three layers of packing to divide the space inside the tower into four sections, in which the distribution of phosgene and inert solvent is different. Through the liquid phase reflux of the third vacuum pump 231 and the gas phase lift of the heater 223, heat exchange occurs in the space between the first packing 211 and the second packing 212, which allows more phosgene to be evaporated and more inert solvent to be condensed. The phosgene F4 extracted by the fourth vacuum pump 24 has extremely high purity and contains almost no inert solvent vapor. After a batch of phosgene is recovered, the inert solvent at the bottom can be collected and reused in the inert solvent F2 stream.

[0029] It is worth noting that the phosgene recovery system of this utility model can operate continuously. It only needs to be connected to the inert solvent F2 stream at the bottom outlet 221 of the phosgene desorption tower 2 through a three-way flow meter, that is, to supply inert solvent to the sprayer 123. For example, by controlling the parameters of the four vacuum pumps, condenser, flow meter and heater within a suitable range, continuous and stable operation can be achieved.

[0030] The above description is merely a preferred embodiment of this utility model. The protection scope of this utility model is not limited to the above embodiments. All technical solutions falling within the scope of this utility model's concept are protected. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of this utility model should also be considered within the protection scope of this utility model.

Claims

1. A phosgene recovery system for the production process of triphenyl isocyanate thiophosphate, characterized in that, The invention includes a phosgene absorption tower and a phosgene desorption tower. The bottom of the phosgene absorption tower is provided with a solvent tank for storing inert solvents. The feed inlet of the phosgene absorption tower is connected to a gas distribution plate. The gas distribution plate is a cavity container with uniform micropores on its upper surface and is disposed inside the solvent tank.

2. The phosgene recovery system in the production process of triphenyl isocyanate thiophosphate as described in claim 1, characterized in that, The solvent tank is provided with a solution outlet, the height of which is lower than the height of the gas distribution plate inside the solvent tank. The solution outlet is connected to the sprayer and the phosgene desorption tower through pipelines, and a three-way flow meter is installed in the pipelines.

3. The phosgene recovery system in the production process of triphenyl isocyanate thiophosphate as described in claim 2, characterized in that, The sprayer is positioned above the solvent tank and is also connected to an inert solvent feed pipe.

4. The phosgene recovery system in the production process of triphenyl isocyanate thiophosphate as described in claim 3, characterized in that, The phosgene absorption tower is equipped with a first condenser and a second condenser, both of which are sieve plates filled with refrigerant.

5. The phosgene recovery system in the production process of triphenyl isocyanate thiophosphate as described in claim 4, characterized in that, The phosgene absorption tower also includes a first vacuum pump, which is used to deliver the gas between the first condenser and the second condenser to the gas distribution plate.

6. The phosgene recovery system in the production process of triphenyl isocyanate thiophosphate as described in any one of claims 2-5, characterized in that, The phosgene desorption tower is provided with a first packing material, a second packing material, and a third packing material arranged from bottom to top. A solution inlet is provided between the first packing material and the second packing material. The solution inlet is connected to the solution outlet.

7. The phosgene recovery system in the production process of triphenyl isocyanate thiophosphate as described in claim 6, characterized in that, A secondary feed inlet is provided between the first packing and the second packing. The phosgene desorption tower also includes a bottom outlet and a heater. The heater heats the solution at the bottom outlet into steam and delivers it to the secondary feed inlet.

8. The phosgene recovery system in the production process of triphenyl isocyanate thiophosphate as described in claim 6, characterized in that, The phosgene desorption tower also includes a third vacuum pump, which is used to deliver the liquid between the second and third packing materials to the solution inlet.

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