Patent GB-1275776-A (GB)
Title: Apparatus for separation and fractionation of material suspended in a liquid
Inventor: OLGARD GUNNAR
IPC: B01D21/26
Filed: 1969-10-07
Abstract: 1275776 Separating solid material REDERIAKTIEBOLAGET NORDSTJERNAN 7 Oct 1969 [7 Oct 1968] 49165/69 Heading B2H An apparatus for separating into fractions material suspended in a liquid comprises a rotatable unit 30 including one or more spiral or helical passageway A-F, Figs. 3 and 4, having circumferentially spaced inlet and discharge ends. Rotation of the unit about its axis causes introduction through the inlet end of the or each passageway of plugs of liquid spaced by plugs of another fluid phase, e.g. air. The friction between the walls of the or each passageway and the liquid plugs causes concentration of particles of greater size in the front portions of the liquid plugs, considered with respect to the direction of movement of the liquid plugs, and concentration of particles of lesser size toward the rear of the plugs, the cross-sectional area of the or each passageway being of continuously varying size at least along a substantial portion of its length to influence the concentrating effect. Means 17a-17c, Fig. 2, are provided for separately collecting fractions of liquid containing concentrations of particles of progressively smaller size as the liquid plugs are discharged from the or each passageway of the or each rotating unit. As shown in Fig. 1, an assembly 20 of identical flat units 30 secured side by side between plates 22 and 24 is rotat-. ably mounted in a casing 10. A hydraulic or other motor 15 is disposed in one end 12a of the casing for driving the assembly and a pipe 16 opens into the other end 14a of the casing to admit the liquid containing the material to be fractionated in suspension. Pockets 17a-17c are provided in the lower part of the casing to receive different fractions of separated material, which are discharged through outlets 18. Each unit 30, Figs. 3 and 4, comprises an annular flat disc having mounted edgewise on one face a number of continuous concentric spiral walls 32a to 32f defining between them and two adjacent discs concentric spiral passageways A to F, the cross-sectional area of each of which decreases from the centre to the periphery of the disc. The central opening through each unit combine to form a central tube 31f in which the liquid introduced through the pipe 16, is maintained at a constant level. As the assembly 20 is rotated (clockwise as seen in Fig. 3) the inner end of a passageway dips into the liquid in the central tube 31f. This continues until that inner end rises above the surface of the liquid in the tube. The plug of liquid thus picked up moves along that passageway as the assembly rotates, until the inner end of the passageway again reaches the surface of the liquid in the tube. The process is then repeated providing in the passageway a series of plugs of liquid separated by plugs of air. During one revolution of the assembly one liquid plug is discharged from each passageway of each unit from just above the pocket 17a until just past the pocket 17c, the forward end of the plug containing the largest particles discharging in the pocket 17a and the rear portion containing the smallest particles discharging in the pocket 17c. In a modification, Fig. 6 (not shown), a spiral partition wall (46) is inserted in individual passageways between the walls of each passageway along a predetermined distance along its length so as to reduce the flow area by providing two smaller parallel passageways. In another modification for separating short and long fibres Fig. 5 (not shown) two adjacent passageways (42, 44) may merge into a single passageway (43) of larger cross-sectional area. In a further modification, converging passageways may be in. the form of helices running lengthwise of the axis of rotation. Specification 1,144,243 is referred to.