Abstract: Separation of a mixture of plastic materials by separating the plastic mixture according to particle size, and introducing plastic of similar size particles into a vertical fluidized bed column having an upwardly flowing gaseous stream therein. The flow rate of the gaseous stream is controlled to provide a relatively low density fraction of the plastic mixture exiting at the upper end of the column, and a relatively high density fraction of the plastic mixture exiting at the lower end of the column. In one embodiment, electrostatic charges are induced on the particles of the plastic mixture prior to introducing the plastic of similar size particles into the column, and the column is charged to attract thereto the plastic particles having the highest electrostatic charge.

Abstract: A method for monitoring the feed of a catalyst, especially the feed of a catalyst employed in a gas-phase linear low density polyethylene process system through the intermediary of the electro-optical scanning of an intermittent flow of the catalyst. The invention also relates to an apparatus for monitoring the catalyst feed in a gas-phase linear low density polyethylene process for the implementing of the inventive monitoring method. An intermittent flow of the catalyst, which is generally opaque, is monitored through the utilization of fiber optics and a light source and light detector device, wherein light which is conducted through the fiber optics passes through a clear or transparent flow channel through which there is effected the catalyst flow, and is monitored through a suitable photocell. The catalyst particles will interrupt the light beam while traversing the transparent flow channel and allow this to be registered by the photocell on a suitable indicating instrument.