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Method and system for removing solvents from isocyanates obtained from phosgenation reaction

An isocyanate and solvent removal technology, which is applied in the field of nitrogen stripping system to remove remaining solvent, can solve the problems of extremely high operating flexibility, the application of guide float valve trays has not been disclosed, and the product yield is decreased.

Active Publication Date: 2018-02-02
WANHUA CHEMICAL (NINGBO) CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] 1. Separation efficiency is limited: low separation efficiency will lead to a certain amount of isocyanate entrained in the circulating solvent, and the circulating solvent is recycled in the phosgenation reaction after condensation and removal of light components. The rapid production of urea when mixed with phosgene will lead to adverse consequences such as blockage of the mixer, increase in side reactions of phosgenation reaction, and decrease in product yield;
[0006] 2. Uneven distribution of trays: There is a stagnation zone in conventional tower equipment. If isocyanate stays in the stagnation zone of the tray for too long, it will generate coke and pollute the tray, resulting in a decrease in the gas-liquid distribution effect of the tray and a further increase in the area of ​​the stagnation zone. After a vicious circle, the tray will soon be severely polluted and the efficiency will drop sharply
[0007] 3. The operating flexibility is not large: Affected by market factors, the load of isocyanate production fluctuates greatly, which requires extremely high operating flexibility. The most stringent one is the desolventization tower. During the solvent removal process, the tower has a large gas volume and liquid volume. Little change with load
[0011] The solvent removal in the isocyanate industry described in the above documents and patents has defects such as high residual heavy components in the solvent and low solvent removal efficiency. The report has not yet disclosed the application of efficient guided valve trays in the field of solvent removal in the isocyanate industry

Method used

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  • Method and system for removing solvents from isocyanates obtained from phosgenation reaction
  • Method and system for removing solvents from isocyanates obtained from phosgenation reaction
  • Method and system for removing solvents from isocyanates obtained from phosgenation reaction

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Embodiment 1

[0086] The bottom discharge of the thermal reactor in this embodiment is 38t / h photochemical solution containing diphenylmethane polyisocyanate (crude MDI), phosgene and chlorobenzene, wherein the crude MDI content is 29.3%, and the chlorobenzene content is 65.5%. , the content of phosgene is 4.5%, and the content of HCl is 0.7%. , 80mm in length, 1.2mm in thickness, and a valve plate lift height of 12mm. The weight of the heavy valve is 33g, the width is 45mm, the length is 80mm, and the thickness is 1.6mm. , The porosity is 16%. The temperature at the bottom of the tower is 140°C, the pressure at the top of the tower is 130kpa, and the phosgene content in the discharge at the bottom of the tower is 150ppm. : The ratio of the number of new guide float valves to blisters is 0.18; the light valve accounts for 10%, the light valve has a mass of 24g, a width of 45mm, a length of 80mm, a thickness of 1.2mm, and a valve plate lifting height of 12mm. A guide hole, the width of th...

Embodiment 2

[0088] The bottom discharge of the thermal reactor in this embodiment is 80t / h photochemical liquid containing diphenylmethane polyisocyanate (crude MDI), phosgene and chlorobenzene, wherein the crude MDI content is 28.3%, and the chlorobenzene content is 66.5% , the content of phosgene is 4.5%, and the content of HCl is 0.7%. , 80mm in length, 1.2mm in thickness, and a valve plate lift height of 12mm. The weight of the heavy valve is 33g, the width is 45mm, the length is 80mm, and the thickness is 1.6mm. , The porosity is 16%. The temperature at the bottom of the tower is 140°C, the pressure at the top of the tower is 130kpa, and the phosgene content in the discharge at the bottom of the tower is 150ppm. : The ratio of the number of new guide float valves to blisters is 0.18; the light valve accounts for 10%, the light valve has a mass of 16g, a width of 40mm, a length of 60mm, a thickness of 1.2mm, and a valve plate with a lifting height of 12mm. A guide hole, the width o...

Embodiment 3

[0090] The bottom discharge of the thermal reactor of this embodiment is the photochemical liquid containing toluene diisocyanate (crude TDI), phosgene and dichlorobenzene of 30t / h, wherein the crude TDI content is 20.5%, and the dichlorobenzene content is 76.6%. The content of phosgene is 1.5%, and the content of tar is 1.4%. The photochemical liquid enters the dephosphorization tower. The internal parts of the dephosphorization tower adopt a combination of light and heavy bar float valves, of which light valves account for 20%. The light valves have a mass of 24g and a width of 45mm. The length is 80mm, the thickness is 1.2mm, and the raised height of the valve plate is 12mm. The weight of the heavy valve is 33g, the width is 45mm, the length is 80mm, and the thickness is 1.6mm. , The porosity is 15%. The temperature at the bottom of the tower is 205°C, the pressure at the top of the tower is 30kpa, and the phosgene content in the discharge at the bottom of the tower is 150...

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Abstract

The invention relates to a method and system for removing solvents from isocyanates obtained from phosgenation reaction with an aim to reduce content of heavy components in the solvents, improving purity of the solvents and increasing operation elasticity. Corresponding amine and the solvents are mixed through the phosgenation reaction and then mixed and reacted with phosgene in a mixer to obtainmixed liquor with materials including isocyanate, the solvents, the phosgene, HCI and the like, the phosgene and the solvents are removed from the mixture via a phosgene removing tower and a solvent removing tower respectively, and crude isocyanates free from the phosgene and the solvents and solvents containing the phosgene and HCl light components and trace isocyanate heavy components are obtained. With the method, content of the heavy components in the cyclic solvents can be effectively reduced, plugging frequency of the amine and the phosgene mixer is reduced, self-polymerization pollutionin a tray and scaling pollution in a reboiler are reduced, operation stability is improved, and meanwhile, energy consumption during solvent removal can be reduced; the method and system is simple inprocess, convenient in operation, energy saving, high in production efficiency and environment friendly.

Description

technical field [0001] The invention relates to a method and system for removing solvent from isocyanate products obtained by phosgenation reaction, in particular to entering the hot reaction liquid obtained by phosgenation reaction into a dephosgenation system to remove phosgene, and then entering a desolventization system to remove Remove a large amount of solvent, and finally remove the remaining solvent through a nitrogen stripping system. technical background [0002] Isocyanate is widely used in the synthesis and production of shoe sole liquid, polyurethane foam, thermal insulation materials, artificial leather and other products. Most of the refining methods of isocyanate products in existing industrialized production are prepared by removing light component solvents. Solvent, excess phosgene and hydrogen chloride end up with the corresponding product. [0003] Isocyanate is a substance that is extremely sensitive to temperature. When the temperature is too high, it...

Claims

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Application Information

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IPC IPC(8): C07C263/20C07C265/14
CPCC07C263/20C07C265/14Y02P20/10
Inventor 文放赵东科张宏科邓如雷曹官义董超徐丹牛桂英姚雨刘小高
Owner WANHUA CHEMICAL (NINGBO) CO LTD
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