Patent GB-795944-A (GB)
Title: Improvements in or relating to the purification of liquids containing suspended particles
IPC: D21F1/66
Filed: 1956-05-14
Abstract: 795,944. Separating solids from liquids by flotation. KROFTA, M. May 14, 1956, No. 14981/56. Class 46. [Also in Group VIII] A process for purifying liquids containing suspended particles, by flotation of the particles, comprises introducing the liquid into the lower central portion of a body thereof while releasing in the body a gas in the form of small bubbles to entrain the particles, causing, by means of a deflector, the gas-entrained particles in the lower central portion to flow laterally in all directions towards the periphery of the body of the liquid and thence causing the entrained particles to flow upwardly in inclined directions toward a common point of withdrawal. A concrete base 4 having a sump 5 supports a cylinder 1 surmounted by a cone or inverted funnel 2. White liquid, e.g., liquid in which fibrous particles of paper, cellulose, wood pulp or textile plants are carried in suspension is introduced through a pipe 10, near the bottom of the cylinder 1, into an upwardly diverging tubular baffle 9 in a direction tangential to a circle midway between the baffle 9 and a central tube 7. This tube is solid with a funnelshaped baffle 8 extending almost to the top edge of the cylinder 1 and extends downwards almost to the concrete base 4 where an adjustable sleeve 15 in its end controls the flow of liquid from the cylinder 1 into the tube. A similarly equipped but wider tube 12 is arranged above the tube 7 in the funnel or baffle 8 and extends to the top of the cone 2 where it enters a collar or stack 3. The white liquid, charged with air, rises in the baffle 9 as the air is liberated and the solid particles are carried by the air over the lower face of the baffle 8 to its circumference then upwards over the lower surface of the cone 2 to the collar 3 where inclined arcuate baffles 22 direct the solids over adjustable weirs 30 to an outlet 26. Clear water descends in the cylinder 1 and funnel 8 to rise up the tubes 7, 12 to the top of the latter which is cut away at one side 19 to form a weir over which the water spills to an outlet 25, partitions 20 separating the space adjoining the outlet from the solids outlet 27 and the baffles 22 providing by their upper faces guides from the weir to the outlet. Perforated plates 13, 14 ensure an even flow to the mouths of the tubes 7, 12. In a modification, the tubes 7, 12 are disposed outside the cylinder and cone, a second cone and baffle 7 are arranged above the existing baffle 8, or three baffles 8 each with its own tubular baffle 9 and meet pipe 10 beneath it are superposed below the cone 2. Fig. 5 shows an apparatus working under reduced pressure. A cylinder 60 mounted on an upper floor of a building is surmounted by a cone 2 and houses a funnel 64 whose tube 62 dips into a discharge chamber 77 for clear liquid as does a tube 61 from the bottom of the cylinder 60. White liquid enters through a tube 69 intermediate the tubes 61, 62 and solids flow from the top of the cone through a pipe 63 to a recovery tank 66. The top of the collar or stack 65 is closed and a float controlled valve 73 opens the interior of the collar to a suction pipe 74.