MULTISTAGE PROCESS FOR THE POLYMERIZATION OF OLEFINS

摘要

Process for transferring polyolefin particles from a first gas-phase polymerization reactor to a second gas-phase polymerization reactor in a multistage polymerization of olefins carried out in at least two serially connected gas-phase polymerization reactors,
wherein the first gas-phase reactor is a fluidized-bed reactor comprising a gas distribution grid and a settling pipe, which is integrated with its upper opening into the distribution grid and contains a bed of polyolefin particles which moves from top to bottom of the settling pipe,
the process comprising the steps of
introducing a fluid into the settling pipe in an amount that an upward stream of the fluid is induced in the bed of polyolefin particles above the fluid introduction point;
withdrawing polyolefin particles from the lower end of the settling pipe; and
transferring the withdrawn polyolefin particles into the second gas-phase polymerization reactor,
process for polymerizing olefins comprising such a process for transferring polyolefin particles, reactor suitable as first gas-phase polymerization reactor in the process for polymerizing olefins and process for discharging polyolefin particles from a fluidized-bed reactor.