## ABSTRACT

The circuit is sampled and analysed for −200mesh material and percent solids. The results are given in Table 18.1.1.

(i) Carryout a material balance and calculate the tons/hr of dilution water added to the sump

(ii) Calculate the flowrates of slurry, solids and water of all streams and specific gravities of all streams and illustrate the material balance of the whole circuit

Solution: Let F = Flow rate of feed solids to hydrocyclone

P = Flow rate of overflow solids from hydrocyclone = Flow rate of solids fed to rod mill

U = Flow rate of underflow solids from hydrocyclone

F=P +U ⇒ F= 100+U −200mesh material balance over hydrocyclone

Ff =Pp+Uu ⇒ (100+U)20= 100× 30+U × 15 ⇒ U= 200 tons/hr; F= 300 tons/hr

Slurry balance over hydrocyclone

Flow rate of slurry fed to hydrocyclone =Flow rate of hydrocylone overflow slurry

+Flowrate of hydrocyclone underflowslurry

⇒ 300 Fraction of solids in feed slurry

= 100 Fraction of solids in overflow slurry

+ 200 Fraction of solids in underflow slurry

= 100 0.40

+ 200 0.80

= 250+ 250= 500

⇒ Fraction of solids in feed slurry to hydrocyclone= 300 500

= 0.60 Flow rate of slurry fed to ball mill

=Flow rate of slurry discharged from rod mill +Flow rate of hydrocyclone underflow slurry

= 100 Fraction of solids in rod mill slurry

+ 200 Fraction of solids in underflow slurry

= 100 0.7518

+ 200 0.80

= 133+ 250= 383 tons/hr =Flow rate of slurry discharged from ball mill

Dilution water to be added to the sump =Flow rate of slurry fed to hydrocyclone

−Flow rate of slurry discharged from ball mill = 500− 383= 117 tons/hr

Flow rate of solids in ball mill feed slurry =Flow rate of solids in rod mill discharge slurry

+Flow rate of solids in hydrocyclone underflow slurry = 100+ 200= 300 tons/hr

=% solids in ball mill discharge slurry = 78.33%

Let the densities of slurries of rodmill feed and/(or) discharge, ball mill feed and/(or) discharge, hydrocyclone feed, overflow and underflow be ρslr, ρslb, ρslh, ρslo and ρslu.