The above flowsheet shows a basic copper mine process, from
mine to metal. There are two distinct types of copper ore, the
sulfide ore and the oxide ore. The sulfide ores are beneficiated
in flotation cells, while the oxide ores are generally leached.
First the copper ore from a open pit mine is blasted, loaded and
transported to the primary crushers. Then the ore is crushed and
screened, with the fine sulfide ore (~-0.5 mm) going to froth
flotation cells for recovery of copper. The coarser ore goes to
the heap leach, where the copper is subjected to a dilute
sulfuric acid solution to dissolve the copper. Then the leach
solution containing the dissolved copper is subjected to a
process called solvent extraction (SX). The SX process
concentrates and purifies the copper leach solution so the copper
can be recovered at a high electrical current efficiency by the
electrowinning cells. It does this by adding a chemical reagent
to the SX tanks which selectively binds with and extracts the
copper, is easily separated from the copper (stripped),
recovering as much of the reagent as possible for re-use. The
concentrated copper solution is dissolved in sulfuric acid and
sent to the electrolytic cells for recovery as copper plates
(cathodes). From the copper cathodes, it is manufactured into
wire, appliances, etc. that are used in every day life. Below are
some photos of the process equipment at an Arizona Copper Mine.
being loaded into a 300 ton truck for transport to the crusher.
crusher at a copper mine. The truck dumps ore into the crusher
which crushes the ore. Screens size and distribute the classified
ore to a series of conveyors, like those above, for
transportation to the mill for further processing.
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trucks deposit coarse ore on a heap leach pad, which has a series
of pipes and hoses dispensing a diluted sulfuric acid solution to
the ore. Copper is dissolved and flows to a pond at the bottom of
the pad. This process can take several months. The leached
solution is pumped to the SX (Solvent Extraction) circuit, which
looks like a series of agitation tanks or cells. The fine sulfide
ore is sent to froth flotation cells like those below for
flotation cells recover the copper from sulfide ores by
chemically attaching the copper to a chemical bubble and
overflowing the froth (bubbles with copper).
The concentrates from the flotation cells are sent to the
smelter for processing to a copper plate. The copper plate is
then dissolved in sulfuric acid and sent to the electrowinning
cells for plating onto cathodes, along with the concentrated
copper from the SX circuits. The copper leach solution typically consists of
40 gm of copper and 200 gm sulfuric acid per liter.
Current densities on the electrowinning cells can be 20-25 amperes per square foot, or more.
electrowinning cells with cathodes. Copper on the annodes ranges from 99.0 to
99.5 percent pure. Power consumed in electroplating copper ranges from 0.08
to 0.20 KWH per pound of copper. Any gold or silver in the copper does not
plate out and drops to the bottom of the cell with the sludge to be recovered later.
transporting and handling the copper cathodes that were removed
from the electrowinning cells. That's it, the rest is
manufacturing products from the pure copper!
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