CN110545895A - Process for recovering dichloromethane in waste gas - Google Patents

Process for recovering dichloromethane in waste gas Download PDF

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Publication number
CN110545895A
CN110545895A CN201780089545.6A CN201780089545A CN110545895A CN 110545895 A CN110545895 A CN 110545895A CN 201780089545 A CN201780089545 A CN 201780089545A CN 110545895 A CN110545895 A CN 110545895A
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China
Prior art keywords
tower
white oil
dichloromethane
lean
desorption
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Pending
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CN201780089545.6A
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Chinese (zh)
Inventor
项威
来庆发
王庆云
宋兴豪
陈干英
姚红果
丁少峰
陈学青
张伟
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SHIJIAZHUANG GONGDA CHEMICAL EQUIPMENT CO Ltd
Shandong ICD High Performance Fibre Co Ltd
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SHIJIAZHUANG GONGDA CHEMICAL EQUIPMENT CO Ltd
Shandong ICD High Performance Fibre Co Ltd
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Publication of CN110545895A publication Critical patent/CN110545895A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1487—Removing organic compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1425—Regeneration of liquid absorbents
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C19/00—Acyclic saturated compounds containing halogen atoms
    • C07C19/01—Acyclic saturated compounds containing halogen atoms containing chlorine
    • C07C19/03—Chloromethanes

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Treating Waste Gases (AREA)
  • Gas Separation By Absorption (AREA)

Abstract

A process for recovering dichloromethane in waste gas comprises the following specific steps: introducing waste gas (1) containing dichloromethane into the bottom of a dichloromethane absorption tower (3), feeding lean white oil (12) into the top of the dichloromethane absorption tower (3), after the two phases are in countercurrent contact in the tower, directly discharging tower top tail gas (5) into the atmosphere, and feeding rich white oil (4) into a desorption tower (8); and secondly, introducing the rich white oil (4) in the first step into the middle upper part of the desorption tower (8), extracting steam at the tower top of the desorption tower (8) through a dry vacuum pump (9), condensing and refluxing the steam, extracting dichloromethane liquid (11), preheating the rich white oil (4) by using the desorbed lean white oil (12), and cooling the rich white oil to 20 ℃ to return to the dichloromethane absorption tower (3) for recycling.

Description

Process for recovering dichloromethane in waste gas Technical Field
The invention relates to a recovery process of dichloromethane in discharged waste gas.
Background
In conventional chemical extraction processes, methylene chloride is a commonly used organic extractant. Methylene chloride has a very low boiling point of 39.8 deg.C, is highly volatile, has a certain toxicity, is harmful to the central nervous system and respiratory system of humans, and its solution is corrosive. The direct discharge of dichloromethane waste gas causes great pollution to the atmosphere, damages the bodies of operators and influences the environment of surrounding living residents.
Disclosure of Invention
The invention aims to provide a process for recovering dichloromethane in waste gas. The recovery process comprises the steps of absorbing dichloromethane in waste gas by using lean white oil through a dichloromethane absorption tower, obtaining tail gas which can be directly discharged to the atmosphere at the tower top, enabling absorbed rich white oil to enter a desorption tower for desorption after heat exchange through a heat exchanger, condensing a gas phase at the tower top to obtain dichloromethane liquid with higher purity, preheating the rich white oil by using the lean white oil desorbed at a tower kettle through the heat exchanger, and enabling the lean white oil to return to the absorption tower through a cooler for reuse.
In order to realize the aim of recovering the dichloromethane, the invention provides
A process for recovering dichloromethane in waste gas comprises the following specific steps:
introducing waste gas containing dichloromethane into the bottom of a dichloromethane absorption tower, feeding lean white oil into the top of the dichloromethane absorption tower, after the two phases are in countercurrent contact in the tower, directly discharging tail gas at the top of the tower into the atmosphere, and feeding rich white oil into a desorption tower;
secondly, introducing the rich white oil in the first step into the middle upper part of the desorption tower, pumping steam at the top of the desorption tower by a dry vacuum pump, condensing the steam, refluxing the steam, extracting dichloromethane liquid, extracting the resolved lean white oil from the bottom of the resolution tower, and returning the resolved lean white oil to the dichloromethane absorption tower for recycling; the liquid feeding position of the desorption tower is the middle upper position of the desorption tower.
Preferably, the dichloromethane absorption column has 3 to 7 theoretical plates; preferably 5 theoretical plates.
Preferably, the temperature of the lean white oil is 15-25 ℃, preferably 20 ℃; the inlet temperature of the exhaust gas is 15-25 ℃, preferably 20 ℃; the temperature of the rich white oil is about 20-30 ℃, and preferably 24 ℃.
Preferably, the operating pressure of the absorption tower is normal pressure.
Preferably, the dichloromethane resolution tower has 3 to 7 theoretical plates; preferably 5 theoretical plates.
Preferably, the temperature of the bottom of the desorption tower is 170-175 ℃.
Preferably, the operating pressure of the desorption tower is 10 kPa.
Preferably, the lean white oil extracted from the desorption tower exchanges heat with the rich white oil before returning to the absorption tower, and the temperature of the lean white oil after heat exchange is 15-25 ℃, preferably 20 ℃.
Drawings
FIG. 1 is a flow chart of a process for recovering methylene chloride from an unorganized waste gas in the present invention.
In the figure, 1-waste gas, 2-absorption tower gas phase cooler, 3-absorption tower, 4-rich white oil, 5-tail gas, 6-primary heat exchanger, 7-secondary heat exchanger, 8-desorption tower, 9-dry vacuum pump, 10-dichloromethane condenser, 11-dichloromethane liquid, 12-lean white oil, 13-desorption tower kettle cooler and 14-absorption tower liquid phase cooler.
Detailed Description
The invention is further described below with reference to examples and figures thereof. It should be understood that these examples are only for illustrating the present invention and are not intended to limit the scope of the present invention. It should also be understood that various changes or modifications can be made by those skilled in the art after reading the disclosure of the present invention, and such equivalents also fall within the scope of the invention as defined by the claims of the present application.
The recovery process of dichloromethane in the waste gas (referred to as recovery process for short, see figure 1) comprises the following specific steps:
firstly, introducing waste gas containing dichloromethane into the bottom of a dichloromethane absorption tower through a Roots blower, feeding lean white oil with high purity into the top of the dichloromethane absorption tower, absorbing dichloromethane in the waste gas by the white oil after the two phases are in countercurrent contact in the tower, directly discharging tail gas into the atmosphere, feeding rich white oil in a tower kettle into a desorption tower, and ensuring that the dichloromethane absorption efficiency of the step is about 90%. The dichloromethane absorption tower has 5 theoretical plates, normal pressure operation pressure, white oil absorbent temperature of about 20 deg.c, waste gas temperature of about 20 deg.c and absorption liquid temperature in the tower kettle of about 24 deg.c.
And secondly, after introducing the rich white oil into the middle upper part of the desorption tower, extracting dichloromethane liquid after steam at the top of the desorption tower is pumped out and condensed by a dry vacuum pump, preheating the dichloromethane absorption tower bottom liquid (rich white oil) by the (lean white oil) at the tower bottom, and then cooling to 20 ℃ to return to the dichloromethane absorption tower for recycling. The desorption tower comprises 5 theoretical plates, the operating pressure is about 10kPa, the liquid feeding position of the desorption tower is the middle upper part of the whole desorption tower, and the kettle temperature is 170-175 ℃.
The specific flow of the process for recovering dichloromethane in the waste gas (see figure 1) of the invention is as follows:
waste gas 1 from a workshop is cooled by an absorption tower gas phase cooler 2 and then enters the bottom of an absorption tower 3, lean white oil 12 desorbed by a desorption tower 8 enters the top of the absorption tower 3, after two-phase material flow is in countercurrent contact in the absorption tower 3, dichloromethane is absorbed by absorption liquid white oil to form rich white oil 4, and the absorbed tail gas 5 can be directly discharged into the atmosphere. The rich white oil 4 enters the middle upper part of a desorption tower 8 after exchanging heat through a primary heat exchanger 6 and a secondary heat exchanger 7, gas phase at the top of the desorption tower 8 is pumped out through a dry vacuum pump 9 and then condensed through a dichloromethane condenser 10, and the obtained condensate 11 is the recycled dichloromethane solution; and a part of the tower bottom liquid of the desorption tower 8 enters a reboiler to be heated and vaporized and then returns to the tower bottom of the desorption tower 8, and the other part of the high-temperature lean white oil 12 exchanges heat with the tower bottom liquid rich white oil 4 of the absorption tower 3 through the secondary heat exchanger 7 and the primary heat exchanger 6, is cooled by the desorption tower bottom cooler 13 and the absorption tower liquid phase cooler 14, and then enters the absorption tower 3 as absorption liquid to be absorbed again. The absorption liquid of the whole system forms circulation, and the consumption of the absorption liquid is reduced to the maximum extent.
The main substances in the waste gas in the invention are dichloromethane, air, trace water vapor and the like. The equipment used in the recovery process adopts an advanced thermal coupling process, so that the energy consumption is low, the recovery rate is high, the pollution is small, the absorbent can be recycled, and the economic cost is reduced.
Example 1
In this example
The process for recovering the dichloromethane in the waste gas comprises the following specific steps:
step one, the concentration of dichloromethane in the waste gas 1 is 0.35mg/ml, and the rest is air; the mass percent of the white oil in the absorbent lean white oil 12 is 99.9 percent, and the percentage content of the methylene dichloride is 0.1 percent. The waste gas 1 is sent to the bottom of the absorption tower 3, the lean white oil 12 is sent to the top of the absorption tower 3, and the two phases are in countercurrent contact absorption in the tower. Obtaining tail gas 5 with dichloromethane concentration lower than 0.035mg/ml at the top of the tower, obtaining tower bottom liquid rich white oil 4 with dichloromethane mass percent of 2.2 percent at the bottom of the tower, and sending the rich white oil 4 to a desorption tower 8.
And secondly, the rich white oil 4 is sent to the middle upper part of a desorption tower 8 after being subjected to heat exchange by a primary heat exchanger 6 and a secondary heat exchanger 7, is sucked by a dry vacuum pump 9 at the top of the desorption tower 8 and then enters a dichloromethane condenser 10, and is condensed to obtain dichloromethane 11 with the mass percentage of 99.9%. The bottom of the desorption tower 8 is provided with 99.9 percent of absorbent lean white oil 12 by mass percentage. The lean white oil 12 exchanges heat with the rich white oil 4 and then enters the bottom of the absorption tower 3 again to form circulation.
In the embodiment, the diameter of an absorption tower 3 is 600mm, 5 theoretical plates are used totally, the normal pressure operation is carried out, the feeding position of absorption liquid lean white oil 12 is on the 1 st theoretical plate, the feeding temperature is 20 ℃, the feeding position of waste gas 1 is in a tower kettle, and the inlet gas temperature is about 20 ℃. The temperature at the top of the tower is 20 ℃, and the temperature at the bottom of the tower is about 23 ℃. The absorption efficiency of the absorption column 3 was 90%.
The diameter of the desorption tower 8 is 400mm, 5 theoretical plates are totally used, the pressure is reduced, the operation pressure is-0.09 Mpa, the liquid feeding position is at the 1 st theoretical plate, the liquid feeding temperature is 120 ℃, the tower top temperature is 50 ℃, and the tower bottom temperature is 170 ℃. The mass percent of the dichloromethane at the top of the tower is 99.9 percent, and the mass percent of the lean white oil at the bottom of the tower is 99.9 percent.
Nothing in this specification is said to apply to the prior art.

Claims (8)

  1. A process for recovering dichloromethane in waste gas comprises the following specific steps:
    introducing waste gas containing dichloromethane into the bottom of a dichloromethane absorption tower, feeding lean white oil into the top of the dichloromethane absorption tower, after the two phases are in countercurrent contact in the tower, directly discharging tail gas at the top of the tower into the atmosphere, and feeding rich white oil into a desorption tower;
    secondly, introducing the rich white oil in the first step into the middle upper part of the desorption tower, pumping steam at the top of the desorption tower by a dry vacuum pump, condensing the steam, refluxing the steam, extracting dichloromethane liquid, extracting the resolved lean white oil from the bottom of the resolution tower, and returning the resolved lean white oil to the dichloromethane absorption tower for recycling; the liquid feeding position of the desorption tower is the middle upper position of the desorption tower.
  2. The process of claim 1, wherein the methylene dichloride absorption column has 3 to 7 theoretical plates; preferably 5 theoretical plates.
  3. A process according to claim 1 or 2, wherein the lean white oil is at a temperature of 15 to 25 ℃, preferably 20 ℃; the inlet temperature of the exhaust gas is 15-25 ℃, preferably 20 ℃; the temperature of the rich white oil is about 20-30 ℃, and preferably 24 ℃.
  4. The process of claim 1 wherein the absorber column is operated at atmospheric pressure.
  5. The process of claim 1, wherein the methylene dichloride resolution column has 3 to 7 theoretical plates; preferably 5 theoretical plates.
  6. The process as claimed in claim 1, wherein the temperature of the bottom of the desorption tower is 170-175 ℃.
  7. The process of claim 1, wherein the stripper column is operated at a pressure of 10 kPa.
  8. The process of claim 1, wherein the lean white oil withdrawn from the stripper is heat exchanged with the rich white oil before returning to the absorption tower, and the temperature of the heat exchanged lean white oil is 15-25 ℃, preferably 20 ℃.
CN201780089545.6A 2017-04-14 2017-12-22 Process for recovering dichloromethane in waste gas Pending CN110545895A (en)

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CN2017102471883 2017-04-14
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PCT/CN2017/118042 WO2018188375A1 (en) 2017-04-14 2017-12-22 Process for recovering dichloromethane in waste gas

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CN201780089545.6A Pending CN110545895A (en) 2017-04-14 2017-12-22 Process for recovering dichloromethane in waste gas

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CN117507293A (en) * 2023-11-08 2024-02-06 浙江信汇新材料股份有限公司 Process method for drying, devolatilizing and treating tail gas of halogenated butyl rubber based on microwave drying

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CN111689834A (en) * 2020-07-06 2020-09-22 中材锂膜有限公司 Wet process lithium cell diaphragm extraction liquid separation economizer
CN115382352A (en) * 2021-05-25 2022-11-25 浙江毅聚新材料有限公司 Dichloromethane recovery process and system for dichloromethane-containing waste gas
CN114225651A (en) * 2021-11-23 2022-03-25 安徽金禾实业股份有限公司 Device and method for recovering sucralose esterification solvent cyclohexane
CN114225652B (en) * 2021-12-08 2022-10-25 华南理工大学 Petroleum absorption stabilizing process without supplementary absorbent and petroleum refining equipment
CN115501723B (en) * 2022-09-29 2023-11-03 山东海科创新研究院有限公司 Method for recycling methane chloride waste gas
CN116392931A (en) * 2023-05-15 2023-07-07 盐城优和博新材料有限公司 System and method for treating tail gas generated in production of ultra-high-strength polyethylene fibers

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