Mining in focus
Copper mining and processing: a trip down memory lane
It is almost impossible to imagine a world without copper, writes Dineo Phoshoko.
The World Copper Factbook 2017, compiled by the International Copper Study Group( ICSG) in 2017, defines copper as a“ malleable and ductile metallic element”. Copper is also considered to be a good source for conducting heat and electricity.
The metal has various uses, some of which are unique to copper. Transport, appliances, electronics, and power generation are among the end uses of the final product.
In an article for the Copper Development Association, Vin Calcutt highlights the fact that copper minerals and ores are located in igneous and sedimentary rocks. As such, copper can be mined using both underground and opencast mining methods. In the article, titled“ Introduction to Copper: Mining & Extraction”, Calcutt explains that copper mined underground usually has higher quality compared to copper mined using opencast mining methods.
Conventional copper processing
The copper mining industry has seen many innovations in the extraction process throughout the years. Before today’ s technology, copper was extracted using conventional methods of leach, solvent extraction and electrowinning( L / SX / EW).
In a paper written for the Journal of the South African Institute of Mining and Metallurgy, GA Kordosky outlines the three methods used in the extraction of copper before the emergence of technological innovations.
The paper titled“ Copper recovery using leach / solvent extraction / electrowinning technology: Forty years of innovation, 2.2 million tonnes of copper annually”,
Kordosky mentions that in 1968, there were only two practices for copper leaching. The first process was the vat leaching of high-grade copper oxide ore. The process was followed by electrowinning of copper from the leach solution— which produces low-quality copper cathode at a high cost. A decrease in the tonnage of high-grade oxide ores in 1968 resulted in a decline in the vat-leaching process.
The second copper leaching process is the heap and dump leaching method. In his paper, Kordosky explains that the“ heap and dump leaching of low-grade oxide and / or sulphide ore was followed by precipitation of low-quality copper from the leach solution on scrap iron”. This process was practiced on oxide ore that was either too low-grade for vat leaching, or low-grade sulphide ore that needed to be mined to expose the underlying high-grade sulphide ore. In those days, recovering copper from leaching low-grade copper ores was very beneficial because understanding the leaching process required minimal effort. Kordosky explained that both these processes— vat and copper leaching— used diluted sulphuric acid.
Improvement in copper mining processes
In that same year, Rancher’ s Bluebird copper solvent extraction plant was built for copper operation in Arizona, US. With the plant came technological innovation that raised the bar on improving copper extraction methods. The plant illustrated that L / SX / EW technology had the ability to produce large quantities of good quality cathode copper consistently on a daily basis.
[ 38 ] MINING MIRROR SEPTEMBER 2018