Olefin polymerization reactor, polyolefin production system and a method for producing a polyolefin

An olefin polymerization reactor, comprising: a cylindrical portion which extends in the vertical direction; reduced diameter portion, which is arranged in the cylindrical portion, the inner diameter decreases toward the downward, and the lower end having a hole penetrating vertically; cylindrical a lower baffle plate, disposed above the reduced diameter portion of the hole, the larger the outer diameter downward, and the lower end of the inner wall of the cylindrical portion of the separation, the upper end has a hole penetrating in the vertical direction ; upper baffle plate, which is disposed above the lower portion of the aperture of the baffle, the outer diameter of the larger downward, and the upper end is closed, and the lower end of the inner wall of the cylindrical portion was separated, the outer diameter of the lower end the inner diameter of the lower bore above the baffle.