Patent ID: 8445606

Claim:
A method of de-bottlenecking and/or reducing the power consumption of an existing plant for continuously polymerizing olefins using free radical initiators, which plant includes: (i) a compressor, with a primary and a secondary compressor, for compressing monomer to a pressure of from 1500 to 3500 bar (150-350 MPa); (ii) a tube having a heating zone at the upstream end for providing an internal heating surface for monomer supplied from the compressor and a plurality of lengthwise spaced reaction zones for polymerizing the compressed feed using free radical initiator(s) under single phase conditions and a cooling heat exchanger associated with the reaction zones surrounding the tube for providing an internal cooling surface for removing heat from the polymerization reaction mixture under single phase conditions; and (iii) a pressure let-down valve to produce two-phase conditions, a separator for separating effluent from the tube into polymer and unreacted monomer and recycle line for recycling unreacted monomer to the compressor, characterized in that said de-bottlenecking method involves modifying the downstream part of the tube to include the pressure let down valve within said tube so as to provide a reduced pressure cooling zone for providing two-phase conditions upstream of the downstream end of the tube and an internal cooling surface to cool the effluent inside the tube subsequent to pressure reduction.