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A variation of this flowsheet would have the first five cells producing the finished concentrate (Figure 5b). On relatively high grade ores, this may be entirely satisfactory if a selective collector is employed.
In one mill that treats a complex copper-iron ore, a small amount of potassium amyl xanthate (0.005 ib/ton) was added to the head of the middling flotation to improve the recovery of the Cu-Fe middlings. This practice of using a small quantity of xanthate as a “kicker” toward the end of rougher flotation is practiced in many copper and zinc flotation plants.
Many copper ores contain finely disseminated copper minerals which require fine grinding to liberate then from the iron and gangue minerals. Treatment of such ores usually involves the flotation of a low-grade rougher concentrate containing the locked middling particles. All or part of this rougher concentrate must then be reground prior to the cleaner flotation. This type of operation is illustrated by the Figure 6 flowsheet.
Such a procedure does not require fine grinding of all the ore, and it therefore reduces grinding costs. Further, it frequently produces better copper recovery
than would be possible if a finer primary grind were used because less slime is formed. Lime is generally copper recovery, and for pyrite depression. In some instances, soda ash or caustic may be employed, but cyanide or other depressants are then required to minimize iron flotations. |
