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A method for recovering hydrogen chloride gas in the tail gas of isocyanate production by gas-phase phosgenation

A technology of hydrogen chloride gas and isocyanate, which is applied in the direction of chlorine/hydrogen chloride, chemical instruments and methods, chlorine/hydrogen chloride purification, etc., can solve problems such as low customer satisfaction, suffocation, and poor quality of takeaway hydrochloric acid, so as to reduce hidden dangers of safety accidents, Stable performance and improved permeation/separation performance

Active Publication Date: 2020-11-24
WANHUA CHEM GRP CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The tail gas containing a large amount of hydrogen chloride and nitrogen is subjected to lye destruction treatment process, in order to neutralize hydrochloric acid, the amount of caustic soda added is very large, and the economic index is poor
However, in the process of by-product hydrochloric acid, it is easily affected by the unstable control of the previous process, and the inert solvent is often not sufficiently removed, resulting in excessive organic content in the by-product hydrochloric acid, poor quality of take-out hydrochloric acid, and low customer satisfaction. Low, ultimately operating the hydrochloric acid absorption system at a loss
In more serious cases, due to the high production load, the poor quality of the by-product hydrochloric acid, and the control measures for the transportation of hazardous chemicals, the hydrochloric acid cannot be sold by road, which will cause a large amount of by-product hydrochloric acid to swell and fill the tanks, and eventually shut down the entire industrial park. very significant impact
[0008] In the preparation process of hexamethylene diisocyanate cited and described above, mainly by absorbing the production tail gas rich in nitrogen and hydrogen chloride with water to prepare hydrochloric acid or neutralizing and destroying it with lye, the added value of hydrogen chloride cannot be improved, nor can it be solved. Production bottleneck caused by hydrochloric acid expansion

Method used

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  • A method for recovering hydrogen chloride gas in the tail gas of isocyanate production by gas-phase phosgenation
  • A method for recovering hydrogen chloride gas in the tail gas of isocyanate production by gas-phase phosgenation
  • A method for recovering hydrogen chloride gas in the tail gas of isocyanate production by gas-phase phosgenation

Examples

Experimental program
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preparation example Construction

[0038] Preparation of composite membrane:

[0039] (1) Add 0.164g of azobisisobutyronitrile and 11.1g of N-vinylpyrrolidone into a three-necked flask reactor with a stirrer and a condenser, add 164g of deionized water, introduce nitrogen for 15min, and stir in a water bath at 60°C for 1 hour Afterwards, 1.21 g of benzamide was added, and the copolymer was polymerized for 7 hours to obtain a copolymer, which was dried in an oven at 60° C. for 24 hours.

[0040] (2) the copolymer after drying is purified through acetone, then heated and refluxed for 12 hours in 2.3% mass concentration of sodium hydroxide aqueous solution, and the hydrolyzate is N-vinyl-γ-aminobutyric acid sodium-sodium benzoate copolymer, The molecular weight is 60000. After cooling, filter out a small amount of suspended matter, purify with acetone, use deionized water to make an aqueous solution, and use ion exchange resin to remove residual small molecule impurities such as sodium hydroxide, and obtain 2.5% ...

Embodiment 1

[0046] The reaction process is as figure 1 As shown in the process flow diagram, the phosgene material (mass concentration is 99%) is mixed with the hexamethylenediamine material (mass concentration is 99.9% industrial hexamethylenediamine), and the molar ratio of the two is 4:1, nitrogen and hexamethylenediamine The molar ratio of diamine is 1.33:1, and hexamethylene diisocyanate is formed by reaction at 300°C. The generated gas phase is captured by a cold solvent, and the liquid phase is sent to the downstream for refining; the tail gas generated by the reaction is condensed to remove solvent and phosgene After absorption, a mixed gas 1 containing hydrogen chloride gas and nitrogen gas is obtained, and the flow rate is 32Nm 3 / h, then the above-mentioned mixed gas 1 is filtered through a candle filter to remove solid impurities in the middle to obtain a mixed gas 2 after removal of impurities, and the solid content in the mixed gas 2 is 0.8 μg / Nm 3 . The mixed gas 2 passes...

Embodiment 2

[0048] The reaction process is as figure 1 As shown in the process flow diagram of Example 1, the same mixed gas 1 containing hydrogen chloride gas and nitrogen as in Example 1 is filtered through a candle filter to remove solid impurities in the middle to obtain mixed gas 2 after impurity removal, and the solid content in mixed gas 2 Concentration 0.8μg / Nm 3 . The mixed gas 2 passes through the Freon cryogenic heat exchanger, cools to -30°C, enters the gas-liquid separation tank 3, condenses and recovers a small amount of organic solvent, and the liquid phase organic solvent 5 is transported to the recovery system 6 through a centrifugal pump, and the gas-liquid separation The mixed gas 4 is heated, and the heated gas 7 enters the coalescing filter at 12°C to remove trace solid impurities and small liquid droplets in the gas, and then mixes the liquid and solid impurities in the non-condensable gas after being filtered by the coalescing filter Further removed to 0.08μg / Nm ...

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Abstract

The invention discloses a method for recovering hydrogen chloride gas in the tail gas of isocyanate production by gas-phase phosgenation, comprising: condensing the tail gas to recover the solvent and absorbing phosgene to obtain a Mixed gas of solid impurities; filter to remove most solid impurities; cool, enter the gas-liquid separator for separation; enter the coalescing filter; transport to the hollow fiber membrane separator, the permeate side gets enriched hydrogen chloride gas, and the non-permeate side gets enriched nitrogen. The separation membrane of the hollow fiber membrane separator is a composite membrane with N-vinyl-gamma aminobutyrate-sodium benzoate copolymer modified coating. This process does not use conventional water absorption or lye destruction process, does not produce a large amount of hydrochloric acid solution with low added value, does not need to consume a large amount of water resources or expensive lye resources; can effectively reuse almost all nitrogen, and has high by-products Value-added, low-corrosivity dry HCl gas.

Description

technical field [0001] The invention relates to the field of isocyanate prepared by gas-phase phosgenation, in particular to a method for recovering hydrogen chloride gas in the tail gas of isocyanate prepared by gas-phase phosgenation. Background technique [0002] Hexamethylene diisocyanate (HDI for short) is a colorless liquid with a pungent odor, and is an important raw material for the synthesis of high-grade polyurethane (PU). In addition to oil resistance and abrasion resistance, polyurethane coatings made from HDI have It also has the characteristics of weather resistance, good light stability, and no yellowing, which is inferior to aromatic polyurethane coatings. It is widely used in automobile manufacturing, aircraft industry, and light industrial products. At present, the main process routes for producing HDI in the world include phosgene method and non-phosgene method. Phosgenation is a commonly used production method in industry, and 85% to 90% of aliphatic dii...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B7/07B01D53/22B01D53/00B01D46/00C08J7/04C08J5/18C08L81/06C08L79/08
CPCC01B7/0706C08J5/18B01D53/228B01D53/002C08J2381/06C08J2379/08C08J2477/00B01D2053/221B01D46/62C08J7/0427
Inventor 杨径靖赵东科周也张宏科王文博刘榕榕徐丹牛桂英
Owner WANHUA CHEM GRP CO LTD
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