Patent ID: 7601303

Claim:
A gas-phase fluidized-bed reactor for polymerizing ethylenically unsaturated monomers, which comprises a reactor chamber in the form of a vertical tube, which has a region of transition in the lower section of the tube, followed by a reaction zone which is followed by a calming zone in the upper section of the tube; a circulation gas line, which is connected to the upper section and the lower section of the reactor chamber and is adapted to convey a reaction gas from the calming zone to the region of transition; a circulation gas compressor and a cooling device, the circulation gas compressor and the cooling device being sited in the circulation gas line; and a closable flap situated in the region of transition from the circulation gas line into the lower section of the reactor chamber which flap is adapted to prevent the penetration of polymer particles into the circulation gas line when the compressor is switched off, wherein the region of transition is adapted for transitioning the reaction gas from the circulation gas line into the reactor chamber, and wherein the region of transition is designed such that either no gas distributor plate is present, or such that only a gas distributor plate is present which has a total surface area and has gas orifices, and wherein said gas orifices occupy more than 20% of the total surface area of said gas distributor plate, and wherein the gas-phase fluidized-bed reactor has no internal heat exchanger in the reactor chamber.