Use: Metal Casting - Copper
of primary copper production use energy. In general, mining uses about 20% of
the total energy requirement, mineral processing (grinding, concentration, floatation)
another 40%, and smelting, converting, and refining the remaining 40%.
will vary by type of production process (pyrometallurgical or hydrometallurgical).
However, for the more prevalent pyrometallurgical approach, the smelting, converting
and refining (electrolytic or fire) processes will collectively consume 30 to
40 million Btu per ton of copper produced. Flash smelters can reduce the overall
energy demand to about 20 million Btu per ton.
The table on
the following page illustrates the fuel and electrical energy portion of the overall
energy requirements for the differing pyrometallurgical processes. Then the total
million Btu / ton requirement is provided.
on pyrometallurgical energy use: Waste heat is generally recovered from both flash
and reverberatory furnaces and used to preheat combustion air and / or to generate
electrical power (cogeneration) in the acid plant. Waste heat can also be used
to dry the furnace charge before smelting, as moisture can carry off heat from
the furnace (and increase overall fuel requirements). Drying usually uses natural
gas and will typically consume between 1 to 3 Mcf per ton of cathode copper. Using
waste heat can reduce the overall drying requirement by up to 0.7 Mcf per ton.
Oxygen enrichment is utilized in reverberatory and reactor methods to attain greater
oxidation and lower energy use.
energy (primarily electricity) is consumed to produce copper in a hydrometallurgical
process. In the most common hydrometallurgical process, the ore is leached with
ammonia or sulfuric acid to extract the copper. After the copper is released into
solution, the copper is removed from the solution by electrowinning (a process
similar to electrolytic refining). Pumping is a major energy expense for these
processes. Electricity for pumps is estimated at around 13.5 million Btu / ton
of cathode copper produced (nearly 4,000 kW per ton) and represents a major expense
for copper producers. These costs could be addressed with Engine Drive pumps (see
ED module). The main variables in pumping costs are the concentration of copper
in the leachate (how much leachate is available) and the distance from the leachate
production area to the solvent extraction facility.