Abstract: A fluidized bed polymerization process in which a central mixing element sweeps the interior of the bed. The mixing element contains agitator arm which pass adjacent to the reactor walls and a have a perforated surface. Gas is directed to the central mixing shaft and distributed to the agitator arms.

Abstract: The invention relates to a method for homo- or copolymerizing ethene in the presence of a Ziegler-Natta or other catalyst and a possible comonomer and hydrogen for preparing a homo- or copolymer of ethene in particle form in propane. In accordance with the invention, the polymerization is performed in a loop reactor under such supercritical conditions where the temperature is higher than the critical temperature of the mixture formed by ethene, propane and a possible hydrogen and a comonomer, but lower than the melting temperature of the ethene polymer forming in the polymerization, and the pressure is higher than the critical pressure of said mixture.

Abstract: The invention concerns a multi-stage process for producing polyethylene having a bimodal and/or broad molecular weight distribution in the presence of an ethylene polymerizing catalyst system in a multistep reaction sequence, in which the first reaction step is a liquid phase polymerization step and the second reaction step is formed by one or more gas-phase polymerization steps. According to the process of the invention in the first reaction step ethylene is polymerized in a loop reactor (10) in an inert low-boiling hydrocarbon medium the residence time being at least 10 minutes, reaction mixture is discharged from the loop reactor (10) and at least a substantial part of the inert hydrocarbon mixture is separated and the polymer is transferred into one or more gas-phase reactors (30), where the polymerization is completed in the presence of ethylene and optionally hydrogen and a comonomer.

Abstract: The invention relates to a method and device for feeding a mud-like catalyst mixture into a polymerization reactor. The catalyst mixture is fed from a container into a batching space of a feeder connected thereto, from which channel the catalyst mixture is further fed by batches into the polymerization reactor by the use of the pressure of a medium fed into the feeder. In accordance with the invention, after each catalyst batch fed into the polymerization reactor, the medium is substantially removed from the batching space of the feeder by leading the medium via an outlet channel into a space between two on/off valves before filling the batching space with a new catalyst batch.