Method for sink and float separation of fine grained mineral raw materials

A method for the sink-and-float separation according to density of a mineral raw material using a liquid, the method comprising:

• feeding a first portion of the liquid through a first liquid inlet into a rotatable drum of a separating vessel and discharging the liquid through a first liquid outlet disposed directly opposite of the first liquid inlet so as to form a first horizontal flow in a liquid bath in the drum, the first liquid inlet and the first liquid outlet being disposed at and just below the top level of the liquid bath, the drum having a plurality of sink-product pockets distributed over an inner circumference of the drum;
• feeding a second portion of the liquid through a second liquid inlet into the rotatable drum and discharging the liquid through a second liquid outlet disposed directly opposite the second liquid inlet so as to form a second horizontal flow in the liquid bath, the second liquid inlet and the second liquid outlet being disposed at a height just above a lowermost set of the plurality of sink-product pockets, the first and second horizontal flows being uniform, essentially laminar, and parallel to an axis of rotation of the drum;
• delivering the raw material in a direction substantially parallel to the liquid so that the raw material is plunged into the liquid bath at an inlet side of the drum;
• separating a float product of the raw material on a side of the drum opposite the inlet side using an overflow, a sink product of the raw material sinking through the liquid bath;
• and
• deflecting a first horizontal flow using a front barrier and a rear barrier, each disposed transversely to a direction of liquid flow, the front and rear barriers projecting into the liquid bath from above, the front barrier being disposed directly downstream of the first inlet and the rear barrier being disposed approximately centrally between the first inlet and the first outlet.