Patent ID: 7781544

Claim:
An apparatus for the polymerization of olefins comprising a gas-phase fluidized-bed reactor ( 1 ), a recycle gas line ( 2 ) connected to the reactor for discharging and recirculating recycle gas comprising solid particles and unpolymerized olefins, and a cyclone ( 3 ) located in the recycle gas line for the reduction and precipitation of the solid particles entrained in the recycle gas from the reactor, with the cyclone comprising: an upper section ( 3 a ) comprising interior walls which has an essentially vertical central axis, whose wall extends along a rotationally symmetric body and which is provided with a cyclone inlet ( 4 ) arranged eccentrically relative to the central axis; a middle section ( 3 b ) comprising interior walls which adjoins the upper section ( 3 a ) and whose wall extends along a rotationally symmetric body which tapers in a downward direction; a lower section ( 3 c ) for discharging the solid particles precipitated from the recycle gas, which adjoins the middle section ( 3 b ) and whose wall extends along a rotationally symmetric body; and a tube ( 5 ) comprising a diameter d i extending essentially axially symmetrically down into the upper section ( 3 a ) and optionally the middle section ( 3 b ) for discharging the recycle gas which has been freed of the solid particles, wherein a ratio H i , equal to h i /d i , has a value from 4.5 to 6.5, h i being the distance from the lower end of the tube ( 5 ) extending downward into the cyclone to an intersection ( 6 ) of an imaginary extension of the wall of the downward-extending tube ( 5 ) with the wall of the middle section ( 3 b ), and d i being the diameter of the downward-extending tube ( 5 ).