Market Survey on Copper - Indian Bureau of Mines

The use of zinc sulphate reduces the consumption of cyanide and therefore
many copper beneficiation plants use cyanide - ZnSO4 combination as zinc
depressant. Sometimes organic reagents, such as, starch, tannin, dyes,
quebracho and dextrine are also used as depressants. These are used in small
quantity to depress talc, graphite and calcite. Starch is used to depress
molybdenite in copper-molybdenum separation.
vi) pH Modifiers : pH plays an important role in flotation of sulphides as
well as non-sulphide. Lime, sodium hydroxide, sodium carbonate, sulphuric
acid, etc. are used as pH modifiers.
Copper flotation is usually carried out in alkaline medium. Lime, being
very cheap, is widely used to regulate/raise pulp alkalinity. It prevents the
adverse effect of soluble salts on flotation by precipitating them as metal
hydroxides. It is also used as depressant for pyrite and arsenopyrite in copper
flotation. It has no depressing effect on copper minerals but does depress
galena. Sulphuric acid is used to bring down pH below 7 which is required for
flotation of pyrites.
As already stated, the beneficiation process may differ in the presence of
a group of gangue as well as other metallic ores; therefore, use of collectors,
frothers, activators, depressants, pH modifiers may differ from simple ores to
complex ores.
C) Dewatering
Many of the mineral separation techniques involve use of substantial
quantity of water. Final test product need to be dewatered to produce dry
product required for shipment. Dewatering process can be broadly classified
into three groups:
a) Sedimentation/thickening
b) Filtration
c) Drying
Dewatering in mineral processing is normally a combination of the above
groups. The bulk of water (up to 80%) is removed by thickening which result in a
thickened pulp up to 60% solid by weight. Filtration of the thickened pulp yields a
moist cake containing 10 to 20% moisture which may require thermal drying to
produce a dry product containing up to 5% moisture.
The filtration units in copper processing plants employ drum and disc filters
with disc having slight edge. Filter capacity also varies considerably and ranges
between 0.4 to 1.0 tpd per sq. ft. filter area. A large number of mills use driers to dry
the copper concentrates. Dryers are used for many reasons - usually because the filter
cake is too wet to strip or because the smelter requires a product with less moisture.
Spray, rotary drum and multiple hearth dryers are used in copper mill. Rotary dryers
are most common.
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