Polyethylene plants, recovery

IFP Process for 1-Butene from Ethylene. 1-Butene is widely used as a comonomer in the production of polyethylene, accounting for over 107,000 t in 1992 and 40% of the total comonomer used. About 60% of the 1-butene produced comes from steam cracking and fluid catalytic cracker effluents (10). This 1-butene is typically produced from by-product raffinate from methyl tert-huty ether production. The recovery of 1-butene from these streams is typically expensive and requires the use of large plants to be economical. Institut Francais du Petrole (IFP) has developed and patented the Alphabutol process which produces 1-butene by selectively dimerizing ethylene. 

Air Products and Chemicals, Inc. has been selected to supply a hydrocarbon and nitrogen recovery system for a new polyethylene manufacturing plant in Baytown, TX. The plant will be owned by Chevron Phillips Chemical Company and Solvay Polymers, Inc. The recovery system uses partial condensation in conjunction with Air Products pressure swing adsorption technology to recover hydrocarbons in the polyolefin plants, and recycle nitrogen with a purity of greater than 99%55. 

The recovery of hydrocarbon monomers from ethylene in polyethylene and polypropylene plants is actually the largest application of vapor separation membranes. After the production of the polyolefin resin, there are unreacted monomer and hydrocarbon solvents dissolved in the resin powder that must be separated in order to reuse the polymer. The traditional application involves stripping with hot nitrogen in a column known as a degassing bin. The values of nitrogen and monomer are both high therefore, the recovery and reuse of these components are of great interest. For this purpose, a membrane operation is profitably used. It consists of two membrane units in series where the off-gas... 

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