CENTRIFUGAL SEPARATION PROCESSES

•Centrifugation is commonly used for particles that will not settle readily or not settle at all in any gravity settlers. •This is due to the closeness of the densities of the particles and the fluid or due to the association of forces holding the components together.

(a) Initial feed entering, (b) settling of solids from a liquid, (c) separation of two liquid fractions.

•For a centrifuge which is used for sedimentation, a sufficient residence time is required for a particle in a bowl to reach the wall.

•Feed enter at the bottom and move upward at uniform velocity carrying solid particles. •Particle removal from the liquid is achieved if sufficient residence time is available for the particle to reach the bowl wall. •If rB<r2, particle leaves the bowl with the fluid. •If rB=r2, it will deposit on the wall and effectively removed from the liquid.

Scale-up of Centrifuges

Exercise

Answer: 8.76 x 10-5 m3/s