Process for the Production of Ethylene

摘要

1,165,668. Ethylene; acetylene. STONE & WEBSTER ENG. CORP. 21 June, 1968 [22 June, 1967], No. 29777/68. Heading C5E. Ethylene (major product) and acetylene (byproduct) are produced by a process comprising the following steps:- (a) cracking a hydrocarbon, e.g. ethane, propane, butane, pentane, naphtha or gas oil, suitably by steam cracking; (b) compressing the cracked gases in at least two, preferably at least four, stages, with increasing pressure in each succeeding stage; (c) fractionating the compressed gases to separate a fraction comprising a major portion of ethylene and a minor portion of acetylene; (d) treating said fraction under elevated pressure with a selective solvent for acetylene (preferably dimethyl formamide, but others mentioned) to give substantially acetylene-free ethylene and an acetylene solution containing a minor amount of ethylene; (e) removing ethylene impurity from the acetylene solution by flash evaporation in at least two stages, with reducing pressure in each succeeding stage, to a final pressure which is not less than the inlet pressure to the first compression stage in step (b); the ethylene thus released being recycled to one of the compression stages; and (f) stripping acetylene from the ethylene-free acetylene solution, e.g. by heat, the solvent being optionally recycled to step (d). The process sequence may also include the following optional steps:- (i) between (a) and (b) the cracked product may be treated with a countercurrent waterreflux to condense heavy hydrocarbons; (ii) the ethylene product from step (d) may be selectively hydrogenated to remove acetylene traces; (iii) between (e) and (f) residual ethylene impurity in the acetylene solution may be removed by stripping, e.g. with heat or acetylene; (iv) the ethylene streams from (e) and (iii) may be water-washed to remove entrained solvent before recycle to the compression step; (v) the solvent in step (d) may be saturated with gaseous ethylene.