Patent DE-19915735-A1 (DE)
Title: Flotation assembly to separate suspension into fractions which are rich and poor with separated matter comprises flotation column with center inflow and blades to divert low fraction into collection zone
Inventor: HEINZ ROBERT
IPC: C02F1/00
Filed: 1999-04-08
Abstract: The flotation system (10a), to separate a suspension into fractions which are rich and poor has a suspension inflow (22) into the separation tank column (28) which gives a central and vertical main flow (30). Blades (32) are arranged radially outside the main flow. To give a fraction with a low matter content, a flow is directed outwards and at a downwards angle to a collection zone (18), into a ring collection channel (34) for the fraction which has a low material content. The separation tank has a circular or polygonal cross section. Or it has a general funnel shape, with an upwards expanding cross section. A further assembly of blades, stacked over each other, forms a cascade structure radially outside the collection channel. The collection channel is between the downstream edges of the initial blades and the upstream edges of the second set of blades. Inflow openings are at the lower end of the collection channel, for the introduction of chemicals and/or bubble fluid mixtures. A filtration zone (40) is radially outside the collection channel, to hold filtration particles of active carbon. The system has a filtrate outlet and a filter material outlet, where the filtration particles move in a counter flow to the filtrate flow in the filtration zone to the regeneration unit (44) at the opposite end, and are recirculated as regenerated particles. A number of blade flotation units and/or filtration units are assembled in an array outwards and in succession. Separate outlets are between them, to take off different fractions. Two or three blade flotation units are deployed as shells, radially outwards, with two or three filtration units outside a flotation unit. The blades have the shape of a closed conical ring, at a pitch angle of 10-40 deg  to the horizontal, and preferably 20-30 deg . In the direction of the flow of the low-content fraction, the blades have a length which is 1-4 times the width of the main flow channel defined by the inner edges of the blades. The gap between the blades increases upwards from below. At least part of the blades is corrugated. At least part of the blades is a multilayer honeycomb structure, with two outer layers and linking structures between them, preferably forming passage flow channels between the outer layers. At least part of the blades is a micro-porous membrane, and at least a part of the blades forms a curvature. The suspension inflow has a channel for the incoming suspension into the flotation assembly, with a radial outlet system to give an outflow in a radial direction, covered by a central passage preferably covered by a conical dome, so that the suspension flows centrally into the flotation tank. The radial unit has a horizontal beating plate (26), to deflect the suspension flow radially, The radial unit has a number of radial outflows (24) in a discrete array round the circumference. A take-off unit (16) for the fraction with a high content of matter is over the separation tank, with a passage aligned with the main flow. It has at least one impeller system to pass the rich fraction through a reject outlet, using a rotating conveyor screw or spatial paddles (56) in a horizontal channel (52). The flotation action is non-selective, using a pressure relief flotation with a bubble flow at the suspension inlet. Or the flotation is selective, with a feed of chemical additives at the suspension flow inlet.