Methods and apparatus for removing residual monomers

A method for removing residual monomers from a slurry containing a polyvinyl chloride and residual monomers after polymerization, with an apparatus comprising a cylindrical tower which has plural perforated plates provided in a vertical direction in the tower, plural chambers formed respectively on the perforated plates serving as the bottom surface of the chambers, slurry introducing devices provided at at least two of said chambers, flow-down sections provided between the perforated plates so as to allow the slurry to sequentially flow down from the perforated plate of an upper chamber to the perforated plate of a lower chamber, a steam introducing port provided at a bottom portion of the tower, a deaerating port provided at a top portion of the tower, a slurry discharging port provided at a chamber positioned lower than the chambers having said slurry introducing devices, and a hot water ejecting means provided directly under said perforated plates and directed toward at least the lower surface of said perforated plates, said slurry introducing devices comprising slurry introducing ports provided at said tower and slurry introducing pipes connected to the slurry introducing ports, the inside diameter of the slurry introducing pipes being enlarged at least 1.2 times toward the slurry introducing ports, which method comprises introducing the slurry into the tower in an amount of 0.1 to 300 m3/h per 1 m2 of the area of the perforated plates forming the bottom surface of said chambers, the linear velocity of the slurry at the slurry introducing port of the chamber being 6 m/sec or lower when the slurry is introduced from said slurry introducing devices, flowing the slurry down from at least one perforated plate, and discharging the slurry outside the tower.