Patent attributes
A process for the gas-phase polymerization of α-olefins carried out in two interconnected polymerization zones, wherein the growing polymer particles flow through the first of said polymerization zones (riser) under fast fluidization conditions, leave said riser and enter the second of said polymerization zones (downcomer) through which they flow downward in a densified form, the process being characterized in that: (a) the gas mixture present in the riser is totally or partially prevented from entering the downcomer by introducing into the upper part of said downcomer a liquid stream LB having a composition different from the gaseous mixture present in the riser; (b) the ratio R between the flow rate Fp of polymer circulated between said downcomer and said riser and the flow rate LB of said liquid being adjusted in a range from 10 to 50.
