Abstract: The present invention relates to a process and a device for introducing a catalytically active powder into a reactor (20) for gas phase alpha-olefin polymerization. The device comprises a storage vessel (3) containing the powder, a metering valve (4) delivering metered quantities of the powder into an intermediate chamber (5) comprising at least one obstacle (6) separating an upper part (5a) of the chamber (5) comprising an auxiliary gas inlet (2a) from a lower part (5b) terminated by an outlet orifice (5c). A connecting pipe (18) connects the outlet orifice (5c) to a mixing device (8) situated on a conveying pipework (15) communicating with the reactor (20). The powder is introduced into the reactor in a dilute suspension form and in a more uniform rate.

Abstract: A fluidized bed apparatus (1) having a fluidization grid (2) below which is positioned a tuyere (5) for guiding fluidization gas to the fluidization grid (2). The tuyere (5) comprises a widening pipe the wider end (6) of which is positioned towards the fluidization grid (2) and has an area which is substantially the same as the cross-sectional area of the fluidized bed apparatus (1) and is 2 to 30 times that of the area of the narrower end (7) of the widening pipe. The process for feeding fluidization gas to a fluidized bed using such apparatus enables a good gas distribution across the bed to be achieved with a modest additional pressure drop. The invention is particularly useful for apparatus e.g. greater than 3 m in diameter.