SU716574A1 - Off-gas purification method - Google Patents

Description

one

The invention relates to methods for purifying gases, it can be used to reduce freon emissions at chemical-metallurgical enterprises.

The pollution of the atmosphere with chlorofluorocarbons, i.e. freons, contributes to the destruction of ozone in the stratosphere and thereby affects the change in the intensity of ultraviolet radiation at the Earth's surface. In this connection, it became necessary to conclude an international agreement to limit the use and production of freons and reduce their emissions into the atmosphere.

The known method of purification of waste gas and their gases from the production of halogenated hydrocarbons, based on their combustion at temperatures above 600 ° C. 1. However, this method cannot be used to clean gases from freon, as they relate to non-combustible gases.

A method is also known for removing halohydrocarbons from gases that can be used for fully chlorinated or fluorinated hydrocarbons, i.e. for freons 2. In this method, the mercury gases of chemical plants containing chlorine and fluorocarbons and their mixtures are purified by their chemical decomposition at 750-1100 ° C in the presence of oxygen-containing gas when in contact with a layer of metal oxides,

for example CaO, AUOa, BaO, MgO, RegOz, NiO. This forms the halides of metals and carbon dioxide.

The process is carried out in a special reactor with platinum nets. The peculiarity of this method is the complexity of the technological operations associated with the need for the consumption of precious metals (platinum), the additional consumption of electricity for heating the reactor, the difficulty and multiplicity of works for

grinding and preparation of oxides, renewing the layer of metal oxides and removing the metal halides from the reactor, etc.

The aim of the invention is to simplify

the process of purification of waste gases from the methane freon series, reduction of material, energy and labor costs.

The goal is achieved by the fact that the decomposition process is carried out at 1700-2800 ° C

in the flame of a combustible hydrogen-containing gas with the subsequent capture of the reaction products ..

Example The waste gas containing freons-12 is purified by the hydrolytic decomposition of a combustible hydrogen-containing gas in the flame in the presence of atmospheric oxygen. Exhaust gas contains, vol. O: o Freon-12 (CCUFz) 8, NgH5; air is 67.5, while freon-12 comes from a cylinder, hydrogen is produced in the Kipp apparatus, oxygen is supplied along with compressed air.

Air is supplied, based on a 10% excess of oxygen from the stoichiometric reaction of the decomposition of freons, described by the equation

CCUFi + -f 2HF + 2HC1

The mixture of gases is ignited in the nozzle. At 1700-2800 ° C in the presence of water vapor, which is formed as a result of the combustion of volodsodrrzhaschogo combustible gas in the acidic air, there is a decomposition, iMO frooi with the formation of CO and a mixture of HF and HC1.

The results of IR spectrometry analysis showed that the exhaust gases after decomposition of freons contain a mixture, vol. %: hydrogen halides 29.1, carbon dioxide 7.2, water vapor 2.9 and trace freon.

The mixture of the resulting halides is absorbed by aqueous solutions, the purified gases are emitted into the atmosphere, and the solutions of the acids are returned to production.

Claims (2)

1. US patent No. 4018879, CL. 423--471, published. 1974.  2. US patent No. 3845191, cl. 423-240, publ. 1977.