separator efficiency calculations

By Dr Y C Naidu

Types of classsificationBasis of Volume ie geometric dimension-

screeningBasis of Mass ie materila properties

Cyclone SeparatorsAir Separators

Principles of SeparationA particle is subjected to three sets of

forces Fd-Force exerted by airFc- Centrifugal forceFg- Force of gravityIf Fd> Fc and Fg, particle air borneFg prevails particle sinkFc prevails particle flung outward of

separator

Particle Size DistributionCumulative distribution curve

On different sieves/micron sizes, the cumulative passing % is plotted.

Independent particle size distribution curve

Size Distribution Curve

Particle Size Distribution

Classification A= F+GA- Classifier feed rate, tphF-Fines output, tphG- Tailing outputa,f,g- proportion of undersize in A,F,and G in

%∆a, ∆f, ∆g – Proportion of particular size

fraction of A,F, G in %

Equations- SeparatorsA.a = F.f+G.gA. ∆a = F. ∆f+G. ∆gVf- % of output finesVg- % of output tailingsP- Precipitation efficiencyµ- recycle ratio

Fines OutputVf =F/Ax100

Vg=G/Ax100

Vf+Vg =100

Calculated from particle size

Vf= a-g x 100 f-g Vg = f-a x 100 f-g

Recycle ratio = A/F = (f-g)/(a-g)

Precipitation Efficiency = (Fxf)/(Axa)x100= Vfxf/ax100

SelectivityIt is characterized by what % of given

particle size in classifier feed is discharged in tailings

T – (Gxdg)/(A.da) x100 = Vg x dg/da

Cut SizeParticle size dt of which half the particles are

discharged in fines and half in tailings.If sharpness of separation poor, more than

50% of even finest particles may end up in tailings, so no definite cut size exists