Multistage process for the polymerization of olefins

The downstream vapour reactor and alkenyl the sequence upstream slurry reactor and method of the polymerization, polymer from the upstream to downstream exchange reaction comprises the following steps: a acclimation) and heating to grains polyolefin slurry, and a liquid medium; b) is at least one separating chamber and gas phase separation polyolefin, particlesc) is a a pair of parallel intermittent working's the bottom part to said polyolefin particle and downstream, reactor in the bottom part of the is derived from any one of claims a separating chamber of polymer, and is used from the reactor and a reaction mixture is a wherein the bottom part of the pressurize.