SETTLING TANK PROVIDED WITH A SLUDGE REMOVAL MECHANISM

摘要

1451210 Settling tanks with sludge removal mechanism F M C CORP 31 Dec 1973 [25 May 1973] 60215/73 Heading BID [Also in Division F2] Sludge is withdrawn from the floor of a settling tank through either or both of conduits 44, 46, depending on the position of valve 60, thereby permitting a. wide variation in mass flow rate without the linear flow rate of sludge being so low that settling out occurs within the conduits. As shown, the sludge concentrates at the trailing apices defined by a zig-zag array of scrapers 20 rotating about a central column 16 in the circular tank, and the inclined lower ends of respective pair of conduits 44, 46 are located in the apices. Each pair of conduits 44, 46 opens into a respective tube 40 which delivers the sludge into a single trough 24, rotating with the scrapers, wherein a level is maintained below tank liquid level L. Valve 60 comprises a tube with slots at its lower end (Fig. 5, not shown), rotated to bring either or both conduits into communication with tube 40 and vertically movable to vary the flow rate further by adjusting the level of outlet 62 and possibly throttling it by partial depression below trough floor 26. With conduits 44 and 46 of four and eight inches diameter a continuous flow range of 40-500 gallons of sludge per minute may be lifted. The sludge could be raised by an air-lift pump, and the invention may be applied to a rectangular tank, using a double-side reciprocating scraper assembly or a scraper moving only in one direction along the tank floor.