Process for treating polyolefin particles obtained by gas-phase polymerization

摘要

Process for treating polyolefin particles obtained by gas-phase polymerization of one or more olefins in the presence of a polymerization catalyst system and a C3-C5 alkane as polymerization diluent in a gas-phase polymerization reactor, the process comprising the steps of
a) discharging the polyolefin particles continuously or discontinuously from the gas-phase polymerization reactor and transferring the particles to a first degassing vessel;b) contacting therein the polyolefin particles with a gaseous stream comprising at least 85 mol-% of C3-C5 alkane while the polyolefin particles have an average residence time in the first degassing vessel of from 5 minutes to 5 hours;c) transferring the polyolefin particles to a second degassing vessel;d) contacting therein the polyolefin particles with a stream comprising nitrogen and steam while the polyolefin particles have an average residence time in the second degassing vessel of from 5 minutes to 2 hours, wherein the contacting is carried out at conditions under which no condensation of water occurs;e) transferring the polyolefin particles to a third degassing vessel;f) contacting therein the polyolefin particles with a stream of nitrogen while the polyolefin particles have an average residence time in the third degassing vessel of from 5 minutes to 8 hours,

and processes for preparing polyolefin polymers by gas-phase polymerization of one or more olefins in the presence of a polymerization catalyst system and a C3-C5 alkane as polymerization diluent in a gas-phase polymerization reactor, wherein the obtained polyolefin particles are subjected to such a treating process.

主权项

1. A process for treating polyolefin particles produced by a gas-phase polymerization of one or more olefins in the presence of a polymerization catalyst system and a C3-C5 alkane as a polymerization diluent in a gas-phase polymerization reactor comprising:
a) discharging the polyolefin particles continuously or discontinuously from the gas-phase polymerization reactor and transferring the particles to a first degassing vessel; b) contacting therein the polyolefin particles with a gaseous stream comprising at least 85 mol-% of C3-C5 alkane while the polyolefin particles have an average residence time in the first degassing vessel of from 5 minutes to 5 hours; c) transferring the polyolefin particles to a second degassing vessel; d) contacting therein the polyolefin particles with a stream comprising nitrogen and steam while the polyolefin particles have an average residence time in the second degassing vessel of from 5 minutes to 2 hours, wherein the contacting is carried out using a stream comprising 2-20% by mol water vapor at conditions under which no condensation of water occurs; e) transferring the polyolefin particles to a third degassing vessel; f) contacting therein the polyolefin particles with a stream of nitrogen while the polyolefin particles have an average residence time in the third degassing vessel of from 5 minutes to 8 hours.