Patent ID: 7902307
Filing Date: 2011-03-08
Classification: B01J,C08F

Abstract:
1. A method for the polymerization of an olefin monomer in a loop reactor system comprising: a) introducing an olefin monomer and a diluent carrier liquid into a reactor system comprising at least one loop reactor; b) supplying at least one polymerization catalyst system to said reactor system; c) circulating said diluent liquid and olefin monomer through said loop reactor while polymerizing said olefin monomer in the presence of said catalyst system to produce a slurry of polymer particles in said diluent carrier liquid; d) diverting a portion of the slurry through said loop reactor into a settling leg connected to said loop reactor and having a lower discharge valve which is repeatedly operated through a cycle or operation in which said discharge valve is opened to discharge settled polymer slurry from said settling leg and thereafter closed to allow polymer slurry to accumulate in said settling leg; and e) controlling the operation of said discharge valve to discharge a volume of slurry from said settling leg through a discharge aperture which volume is within the range of 20 volume percent of the volume of slurry settled in said settling leg since the discharge of slurry from said settling leg in a previous cycle of operation; and f) monitoring the volume of slurry in said settling leg since the discharge of slurry from said settling leg in the previous cycle of operation, generating a signal representative of the monitored volume and discharging a predetermined volume of the slurry from said settling leg in response to said monitoring signal.