SU1754182A1 - Method of cleaning effluent gases from alkyl chloride vapors - Google Patents

Abstract

Use: production of dimethyl phosphite, chloral in the chemical industry. SUMMARY OF THE INVENTION: Exhaust gases containing chloride alkyl pairs with a boiling point below 50 ° C are fed to the condensation stage under Pressure. Residual pairs of chloride alkyls are caught by chilled alcohol under the same pressure in two stages. In the first degree under isothermal conditions. Alcohol with a dissolved alkyl chloride is sent to the main process as a starting reagent. The degree of trapping chloride alkyls is 98.2-98.5%. 1 il.

Description

The invention relates to the chemical industry, in particular to the process of purification of the technological gas puffs from alkyl chloride vapors with a boiling point below 50 ° C. -H

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A known method for isolating products of the direct synthesis of methylchlorosilanes4, in which methyl chloride and volatile methylchlorosilanes from the reaction products are absorbed by chlorine derivatives of methane, ethane, benzene or turpentine and kerosene at 20-10 ° C and pressure of 0-5 atm. The main disadvantage of this method is the need for the regeneration of the absorbent, which leads to a significant energy expenditure on the cleaning process. The use of a regenerated absorbent containing chloromethyl residues makes it difficult to achieve a high degree of purification of gas scrubs. Selected during regeneration

Chloromethyl absorbent is contaminated with absorbent.

A condensation-absorption method for gas purification from vapors of halogen-containing hydrocarbons with a heterogeneous aerosol (2) is described. 0.5-6.5 kg / m3 of water vapor and up to 0.1 kg / m3 of high-boiling organic matter vapor are introduced into the purified gas containing not more than 0.01 kg / m of vapors of halogen-containing hydrocarbons. Surface-active properties and low solubility in water. The vapor-gas mixture is cooled; a heterogeneous aerosol absorbing the halogen-containing hydrocarbon is obtained. Aerosol is collected from the organic layer; a halogen-containing hydrocarbon is removed by known methods.

The disadvantages of this method are the very high energy costs of obtaining a vapor stream of the absorbent material,

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the capture of hydrocarbon organic absorbent, water and hydrolysis products.

A known method of purification of gas blows from chloromethyl, according to which the main part of chloromethyl from the gas mixture is separated by condensation under pressure, and the remaining part is captured by absorption on activated carbon, and the regeneration of the sorbent is carried out with hot nitrogen (3).

This method requires the creation of a sorbent regeneration system.

Its disadvantages include significant energy costs for the regeneration of the sorbent and the release of chloromethyl from the desorbent (heating the nitrogen, cooling the desorbent, compressing, condensing chloromethyl), as well as a high fire hazard due to the rapid heating of the sorbent during the chloromethyl slip.

The aim of the invention is to eliminate the need for regeneration of the sorbent.

This goal is achieved by the fact that after condensation trapping of chloride alkyls under pressure is subjected to absorption two-stage purification under the same pressure laid down by the initial chemical process reagent, which is the source of the release of chloride alkyls. in the first stage, absorption is carried out with heat removal of the process, i.e., isothermal conditions.

The installation diagram on which this method is implemented is shown in the drawing.

The gas-vapor mixture C with halogen-containing hydrocarbons (flow I) in compressor 1 is compressed to a pressure that ensures condensation of the halogen-containing hydrocarbon at 0-50 ° C. In the cooler-condenser 2, the mixture is cooled, the bulk of the halogen-containing hydrocarbon is condensed. The condensate is collected in the collector 3, and the uncondensed gases are passed through the tail condenser 4, cooled, as a rule, by a low-temperature heat carrier.

Gases after condensation trapping (stream II) are fed to the bubbler of a capacitive absorbent cooler 5 filled with 30-50% absorbent. At least 50% of the vapor absorbed by the absorption is absorbed under isothermal conditions. Next, the gases pass through column 6, which is irrigated by the source absorbent (stream IV) cooled in the refrigerator 7 (feed IV) by the feed pump 8

Absorbent with dissolved chlorinated organochlorine carbon is fed to the chemical process (stream V)

The specific consumption of the absorbent is determined by the ratio

1 (1.5-3.5) НрХ / Р. (1)

where I is the specific mass consumption of the absorbent, kg / kg inert in gases;

HrH - Henry coefficient, MPa; 0 Р - absolute process pressure, MPa

at lower costs, the efficiency of the process is reduced due to a decrease in the driving force. Lr & The higher costs of 5 absorbent increase in costs from its cooling and pumping.

PRI me R 1. Purification of gases from methyl chloride vapors in the production of dimethyl phosphite was carried out with methanol at the above described installation with the following process characteristics: Absolute pressure in the system 0.5 MPa

Temperature by gas

5 absorbentaminus 10 ° С

The height of the nozzle in the column (6) 1600 mm

Specific consumption of methanol4 kg / kg of gas 0 Chloromethyl content in relative mass fractions In gases after condensation (stream II) 0.296 V purified gas

5 (stream III) 0.004

In methanol (stream V), 0.074 The degree of chloromethyl-98.5% trapping was carried out. Example 2 was carried out without cooling the absorbent in the absorber (1) of step 5. The temperature of methanol at the outlet from the absorbent (flow V) increased to + 20 ° С, and the efficiency of chloromethyl trapping decreased by 5 to 96.7%.

PRI me R 3. Purification of gases from the vapor

ethyl chloride in the production of chloral

produced ethanol on the above

installation with the following process characteristics:

Absolute pressure 0.3 MPa Temperature of gases and ethanol 10 ° С

Specific consumption of 5 ethanol1 kg / kg gas

Chloroethyl content in relative mass fractions

flow II -0,353

flow III -0,007

flow V -0,346

The degree of trapping chloroethyl982%

From the examples it is clear that the proposed method allows to achieve a high degree of purification with less energy consumption due to the absence of a sorbent regeneration stage.

Claims (1)

DETAILED DESCRIPTION OF THE INVENTION A method for cleaning exhaust gases from alkyl chloride vapors with a boiling point below 50 ° C, comprising 0 condensation of vapor under pressure and subsequent trapping of residual vapors when contacted with a sorbent, characterized in that, in order to eliminate the need for regeneration of the sorbent, cooled alcohol is used as a sorbent in two stages, in the first stage under isothermal conditions, after which the alcohol containing dissolved alkyl chloride. sent to the main process as a starting reagent. 3