Deodorising of freshly cut polypropylene chips

摘要

Polypropylene chips are cut under water (1) and dried in a water separator (2) followed by a centrifugal drier (3). The chips are transferred at a temperature of 105-140 deg C through rotary locks (9.1, 9.2) and a pipe (10) into a column drier (4). Inert gas is fed to the pipe (10) at a rate appropriate to the rate of chip flow and the leakage rate through a separating cyclone (8). In the column drier (4) the chips are exposed to a contra-flow of steam and/or inert gas at 100-140 deg C for 3-15 hours to deodorise them and remove chlorinated hydrocarbons. The chips are removed from the drier through a steam-heated double walled pipe (11), using nitrogen to displace the steam entrained between the chips. The chips are then cooled (15) by means of air to 40-50 deg C.