FI761642

A process is claimed for sepg. solid material from a liquid suspension of which the density is only slightly more than that of the solid material. The liquid is fed continuously into a ring of liquid formed and maintained in the acceleration zone of the bowl of a decanter centrifuge; separation takes place in a retention time of 10 to 500 secs and at an acceleration of 2,000 to 10,000g to produce a solids-enrichd or conc. phase and a clarified liquid phase the conc. phase being conveyed at an average speed of 0.1 to 5.0 cm/s along te wall of the bowl in the direction opposite to that of the acceleration force so that the fluid mass of conc. phase builds up an annular dam to retain the ring of liquid. The retention time is pref. 50 to 150 secs. and the acceleration 3,000 to 5,000g. Used for mechanical sepn. of solid particles, e.g. of dia. 0.5 to 5.0 um, from a liquid suspension having a density only slightly higher than that of the particles; partic. the sepn. from aq. suspension of flocculated colouring agents, microorganisms such as yeasts, bacteria, Streptomyces, fungoid growths, culture media solns. etc. This process decants off liquid to give a conc. phase with a much higher solids % wt. than the 16% or so which is obtainable employing conventional centrifugal separation; examples quote culture solns. with initial solids concs. 1% to 8% being taken up to 20% to 35% solids % wt.