SOLIDS RECOVERY USING CROSS-FLOW MICROFILTER AND AUTOMATIC PISTON DISCHARGE CENTRIFUGE

摘要

In a system for combined centrifugation and microfiltration, retentate from a cross-flow microfilter (201) is fed to an automatic piston discharge (APD) centrifuge (210) for solids removal, thereby enhancing the efficiency of both processes. A solids-containing suspension (207) is fed into a tank (202) and then pumped (203) to a microporous membrane filter to decide whether to return the retentate (236) to the microfilter (201) or to divert the retentate by means of a valve (235) as feed (230) to the APD centrifuge (210). A turbidity or density meter (220) also can be installed on the centrate output of the APD centrifuge (210) to indicate when the APD bowl is full of solids, or to control a centrate pump (222) and to decide whether to return (224) the centrate to the retentate tank (202) by means of a valve (223) or to discharge (228) the centrate from the system. The APD centrifuge (210) includes a cylindrical bowl having a conical lower end with an opening through which feed liquid is injected. Solids separate from the feed liquid and accumulate along the inner surface of the bowl as the bowl rotates at high speed. A microfiltration membrane can be added to improve solids retention in the bowl and provide a filtered centrate. During solids discharge, a piston is urged downward along a vertical axis.. The downward movement of the piston forces accumulated solids from the bowl via the opening in the conical lower end thereof.