Apparatus And Process For The Withdrawal Of Polymer From A Gas-Phase Polymerization Reactor

Equipment for the gas-phase polymerization of olefin(s), including a reactor with a fluidized or mechanically stirred bed and with a vertical side wall, provided at its base with a fluidization grid, the vertical side wall of the reactor extending a height H above the fluidization grid, a conduit for external circulation of a reaction gas mixture, connecting the top of the reactor to the base of the reactor under the fluidization grid and including a compressor and at least one piece of equipment for heat removal, a bed level controller, and at least one withdrawal conduit for withdrawing polymer, at least one uplift conduit, at least one recovery gas lock hopper equipped with a discharge valve, and at least one degassing chamber, the equipment being characterized in that

• (i) the at least one withdrawal conduit connects the reactor to the at least one recovery gas lock hopper, the at least one withdrawal conduit has an isolation valve prior to the recovery gas lock hopper and the at least one withdrawal conduit leaves the side wall of the reactor at a height of the reactor wall above the fluidization grid ranging from 0H to 0.15H, whilst being directed in a downwards fashion at an angle A with the horizontal plane ranging from 20 to 75 degrees below the horizontal plane, and said withdrawal conduit having an internal diameter of between 5.0 and 20.5 cm,
• (ii) the recovery gas lock hopper has a volume of at least 200 litres,
• (iii) the at least one uplift conduit is connected between the recovery gas lock hopper and an inlet of the degassing chamber and has a vertical height of at least 20 m and an internal diameter of between 5.0 and 20.5 cm, and provides transport in an upwards direction in the direction of flow between the reactor and the inlet of the degassing chamber, and
• (iv) the inlet of the at least one degassing chamber is disposed at a vertical height above the vertical height at which the withdrawal conduit leaves the side wall of the reactor.

Process for the polymerisation of olefins, which process comprises

• a) polymerising one or more olefin monomers in a reactor in the presence of a polymerization catalyst in a fluidized or mechanically stirred bed, said reactor having a vertical side wall, and being provided at its base with a fluidization grid, the vertical side wall of the reactor extending a height H above the fluidization grid, said polymerization also comprising removing a reaction gas mixture from the top of the reactor, compressing and removing heat therefrom and recycling the mixture to the base of the reactor under the fluidization grid, and controlling the level of the fluidised or mechanically stirred bed by a bed level controller,
• b) withdrawing polymer through at least one withdrawal conduit, which withdrawal conduit leaves the side wall of the reactor at a height of the reactor wall above the fluidization grid ranging from 0H to 0.15H, is directed in a downwards fashion at an angle A with the horizontal plane ranging from 20 to 75 degrees below the horizontal plane and has an internal diameter of between 5.0 and 20.5 cm, and passing the polymer to at least one recovery gas lock hopper equipped with a discharge valve and which has a volume of at least 200 litres, and
• c) subsequently passing the polymer via at least one uplift conduit which has a vertical height of at least 20 m and an internal diameter of between 5.0 and 20.5 cm, to the inlet of at least one degassing chamber which inlet is disposed at a vertical height above the vertical height at which the withdrawal conduit leaves the side wall of the reactor.