Separation method of polymer powder and carrier gas

In method for separating polymer powder from a carrier gas by introducing a stream of a mixture of the polymer powder and the carrier gas into a cyclone separator, drawing the polymer powder, which has been separated from the carrier gas, through a bottom part of the cyclone separator into a hopper, drawing the carrier gas from an upper part of the cyclone separator and feeding out the polymer by a rotary feeder from the bottom part of the hopper, the improvements wherein:

• (a) the revolution speed of the rotary feeder is controlled in accordance with variations in the powder level in the hopper so as to control the amount of the polymer powder to be discharged out from the hopper, and
• (b) the volume of a purge gas which is introduced into a polymer powder guide extending between the cyclone separator and the hopper for the prevention of plugging thereof is controlled in accordance with variations in the revolution speed of the rotary feeder,
• whereby the plugging of the guide between the cyclone separator and the hopper are prevented and the powder level in the hopper is maintained at a predetermined constant level.