Importance

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Abstract

A control system to prevent the accumulation of excessive cellular material in a fluidized-bed reactor wherein a waste liquid to be processed is conducted upwardly at a velocity conducive to fluidization through a bed of particles which function as a carrier for the growth of the material. The system includes a separator column whose low end section extends toward the fluidized bed and whose high end section extends above a head of liquid effluent which lies on the bed, or is sealed and located below the surface of liquid effluent, the diameter of the high end section being greater than that of the low end section. In the course of reactor operation, the cellular material on the particles continues to grow, causing the bed to expand until its level reaches a point indicative of excessive growth. This point is sensed to activate an agitator arrangement which effects shearing of the excess cellular material from the particles to produce in the separator column a mixture of sheared material and partially stripped carrier particles. The separator column is provided with a draw-off port somewhat below the surface of the effluent head, the exit flow rate at the draw-off port being adjusted so that the resultant upward flow velocity in the separator column is lower than the settling velocity of the carrier particles in the mixture but higher than that of the sheared material. As a consequence, the sheared material is washed away through the draw-off port, whereas the partially stripped carrier particles fall back into the fluidized bed.

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First Claim