Method for controlling gas-velocity in gas-phase polymerization vessel and process for gas-phase polymerization

摘要

In a gas-phase polymerization apparatus for olefins having a polymerization equipment for olefins using a gas-phase polymerization vessel of fluid layer type in which gas-phase polymerization is carried out with a solid catalyst component, a circulation line in which a polymerization component-containing gas taken out from a velocity-reduction region positioned in an upper portion of the gas-phase polymerization vessel of fluid layer type is turned back to the gas-phase polymerization vessel of fluid layer type to be circulated so as to be a circulating-gas, and a feeding line for feeding fresh olefins to the gas-phase polymerization vessel of fluid layer type, a supersonic wave flow meter is provided on the circulation line; the circulating-gas flow volume of the polymerization component-containing gas is determined by means of the supersonic wave flow meter; and the gas-velocity of the gas flow forming the fluid layer region in the gas-phase polymerization vessel of fluid layer type is controlled based on the determination result, thereby the linear gas-velocity can be controlled stably for a long time without a flow meter of differential pressure type and the circulating-gas volume can be determined stably for a long time with high good accuracy. <IMAGE>