Patent ID: 8030420

Claim:
A polyolefin production process which comprises carrying out olefin polymerization using an olefin polymerization reaction unit comprising: a multistage gas phase polymerization reactor which is divided into two or more polymerization stages, in which polyolefin particles move from an initial stage to a final stage, and in which an olefin monomer-containing gas is fed from the final stage toward the initial stage; first circulating means for feeding to the final stage a gas, wherein the gas is discharged from the initial stage and then cooled with a first heat exchanger; and second circulating means for feeding to one of the polymerization stages a condensate, wherein the condensate is formed by condensing, with a second heat exchanger different from the first heat exchanger, a gas removed from one of the polymerization stages, wherein the second circulating means feeds the condensate to the polymerization stage immediately before the polymerization stage from which gas is removed.