Method of multistage gas phase polymerization, apparatus therefor and device for reducing entrainment of subcomponents in polymer powder in apparatus for multistage gas phase polymerization

Abstract

A method of multistage gas phase polymerization is provided comprising performing polymerization of a feed gas mixture at least containing ethylene gas, an &agr;-olefin gas and hydrogen gas in an upstream fluid bed reactor to thereby produce a polymer powder, recovering the thus-produced polymer powder and performing further polymerization of the polymer powder in a downstream fluid bed reactor, the downstream fluid bed reactor being continuously connected to the upstream fluid bed reactor so that the polymer powder recovered from the upstream fluid bed reactor is introduced into the downstream fluid bed reactor, which method comprises the steps of: recovering polymer powder from the upstream fluid bed reactor, treating the recovered polymer powder so as to lower the content of &agr;-olefin gas and hydrogen gas therein by contacting the polymer powder with a stream of gas comprising ethylene or an inert gas, and introducing the treated polymer powder into the downstream fluid bed reactor. By this method, &agr;-olefin gas and hydrogen gas which inhibit the polymerization reaction in the downstream fluid bed reactor and which render regulation of desired polymer product properties difficult are removed from the polymer product prior to the downstream fluid bed reactor.