The polymer powder is discharged from the reactor(s) and separated from the gas in a discharge cyclone at atmospheric pressure. Any unreacted monomer separated from the powder is compressed and either recycled or returned to the upstream olefins unit for recovery. The final degassing of the polymer is done in a purge silo by flushing with nitrogen. The purge offgas is sent to a recovery system. Finally, the powder is converted into pellets that incorporate a full range of well-dispersed additives.