GB659978A - Liquid clarification - Google Patents

Abstract

659,978. Gravity-separation apparatus. TRIGGS, W. W. (Gibbs, Inc., F. S.). Oct. 17, 1949, No. 26618. [Classes 46 and 111] [Also in Groups VI and XII] Matter suspended in a liquid, such as industrial waste waters, coagulated impurities in raw sugar juice or fats in glycerine, is removed from the liquid by introducing the liquid containing the suspended matter into a zone in which a generally downwardly flowing body of the liquid having an essentially quiescent surface is confined, the point of introduction of the introduced liquid being below the quiescent surface and substantially centrally thereof, passing minute gas bubbles into the downwardly flowing liquid, now including the introduced liquid, at a point below the introduction of the introduced liquid and recovering the suspended matter floated to the surface of the liquid by attachment of the bubbles thereto. As shown, the suspension is introduced through a pipe 17, (see Fig. 1), to flow upwards through a riser pipe 16 to a distributor 18 of inverted cone shape to spread the liquid radially and prevent disturbance of the surface of the body of liquid forming the quiescent zone in the upper part of tank 10. The liquid flows downwards and under the bottom edge of an annular baffle 14 and upwards through the space between the baffle 14 and the tank wall 11 to overflow into trough 37. The edge of the tank wall 11 is provided with an adjustable weir 39. Liquid is continuously drawn from the bottom of the chamber through a header member comprising apertured rings 28 and charged with air or other gas (see Groups VI and XII) and the gas-charged liquid is returned into the header comprising apertured rings 27. The floating matter is removed from the quiescent surface by two flexible skimmer blades 23, e.g. of rubber, rotated by motor 20, the blades sweeping the surfaced sludge over a radially extending riser plate 40 into a collection trough 24 which discharges through pipe 25. The lower edges of blades 23 lie below the leading edge 57 (see Fig. 4) of the plate 40, the leading and trailing edges of which are radial with respect to the centre of rotation of the blades 23, but the discharge edge 59 of trough 24 is parallel to the trailing edge 58 of the plate 40 and, like the edge 58, the edge 59 stands above liquid level. In a modification the lower header 28 is omitted, the liquid to be charged with gas bubbles being drawn from a suction box depending from the trough 37, then charged with the gas and returned to a header 27.