Process for removing and recovering of aperfeicoado monomer of vinyl chloride from a stream of gas discharge in a polyvinyl chloride extraction

摘要

In polyvinyl chloride production plants air enters the process during production operations and must be vented to the atmosphere. The air becomes mixed with gaseous vinyl chloride monomer during the process and not all of the vinyl chloride monomer can be condensed therefrom as liquid in the normal monomer recovery operation. Consequently the vent gas stream contains appreciable proportions of vinyl chloride monomer along with air, and in many cases is saturated with watervapor. In order to remove and recover the vinyl chloride monomer from the vent gas before it is released to the atmosphere, the vent gas stream is treated counter-currently with a stream of liquid solvent which absorbs the vinyl chloride monomer and the vinyl chloride monomer is then stripped from the solvent by application of heat and condensed as liquid vinyl chloride while recycling the lean solvent to the absorption step. The solvent used as the absorbent is a branched chain saturated aliphatic hydrocarbon containing 8 carbon atoms and composed predominantely of 2,2,4-trimethyl pentane. This solvent enables the vinyl chloride content of the gases vented to the atmosphere to be reduced to less than 5 and even less than 1 part per million by volume. Its use assures that any solvent vapors emitted with the vent gas are controllable so as to be not harmful to the environment. Its use also assures that the normal steam supply at the plant will provide the heat necessary to strip the absorbed vinyl chloride monomer from the solvent.