Effect of Operating Variables on Metallurgical Process Parameters

Effect of Operating Variables on Metallurgical Process Parameters

Metallurgists Need Statistics

VARIABLE

RANGE

EFFECT ON PROCESS

Crushing

Jaw Crusher Close side setting

3″ plus

– Material too large for cone crusher.

N – 3″

L – Reduction in capacity. Excess power draw.

Cone Crusher Close side setting

3/8″ – 1″

H – Increased circulating load of screen and cone.

N – 1/2″

L – Increased power consumption, decrease capacity.

Dust Collector recirculating % solids

7 – 10%

H– Excessive nozzle and impeller wear.

N – 8%

L – No effect.

Grinding

 Mill Feed Conveyor Speed (feed rate)               0-33 mtph  H– May overload mill with increase in circulating load.
 N – 22 mtph
 L – Decrease in plant
throughput.
 Mill Percent solids  50-70%  H-Increase in circulating load. Poor grinding efficiency.
 N – 60%
 L – Increase throughput but decreases grinding efficiency
 Cyclone Feed Density  45 – 60%  H– Coarse particles in
cyclone overflow.
 N – 52% solids.
 L – Fine particles in cyclone overflow, less product.
 Cyclone 0/F density  25 – 35% H– Coarse particle in cyclone overflow, potential to sand gravity line to thickener.
 N – 30%
 L – Fine particles in cyclone overflow.
 Cyclone Apex opening  2 “-4” – Decrease cyclone underflow density.
 N – As required.
 L – Increase cyclone underflow density and potential ‘roping’ condition.
 Cyclone 0/F pH  10-11  – Waste of lime.
 N – 10.5
 L – Danger of HCN generation.
 Cyclone U/F density  60-75%  – Coarse particles in cyclone overflow and increase in circulating load.
 N – 69%
 L – Fine particles in cyclone underflow, less product.
 Thickening
 Thickener Overflow clarity  15-100 ppm  – Increase load on clarifier
 N – 50 ppm.
 L – Good.
 Thickener Underflow solids  50-70%  – Potential for sanding lines.
 N – 60%
 L – Excess pregnant solution in leach feed.
 Thickener Flocculant addition  25-100 gm/t – Waste of flocculant and underflow could become jelly-like.
 N – 50 gm/tonne.
 L – Solids increase in thickener overflow.
 Leaching
 Leaching Cyanide concentration 5-9 kg/tonne  – Waste of cyanide, may dissolve undesirable metals.
N – 7 kg/tonne
 L – Incomplete precious metals dissolution.
Leaching Air addition  2-3 kg/tonne  – Wasting lime.
N – 2.55 kg/tonne
 L – HCN generation, incomplete precious metals dissolution.
 Leaching Pulp density  40-50%  – Excess power required to keep slurry in suspension, solids may scale.
 N – 45%
L – Decrease in retention time, hence recovery.
 Filtration
 Filtration Filter feed pH  11.5-12.5  – Waste of lime.
 N – 12.0
 L – Poor filtration, slimly cake and reduced throughput.
 Filtration Vacuum 18-25″ Hg  – Wasting energy.
 N – 22″ Hg
 L – Increase in cake moisture, poor pregnant solution recovery, slimly cake.
 Filtration Flocculant addition  50-100 gm/tonne  – Waste of flocculant.
 N – 75 gm/tonne
 L – Blinding of filter cloth.
 Flotation
 Flotation Air  – Will float waste (gange) material.
 N – 100/30 S C F M rougher/cleaner cells.
 L – Poor froth generation and recovery.
 Merrill-Crowe
 Deaeration Vacuum  18-25″ Hg  – Waste of energy.
  N – 22″ Hg
 L – Poor removal of oxygen from solution, gold/silver will redissolve.