With the potential to cause loss of revenue, and in worst-case scenarios shut a mine down completely, finding innovative ways to identify and mitigate the risks associated with colloidal silica is crucial if mines want to remain operational and optimise efficiencies, writes Daniel Verwey, Technology Manager at Protea Mining Chemicals.
The Democratic Republic of Congo produced approximately 1.4 million tonnes of copper (about 70% of global copper resources) in 2020. Along with that, the by-product of copper mining, Cobalt, yielded around 95 000 tonnes (about 60% of global cobalt resources) in the same period. Both copper and cobalt have a vast range of household and industrial uses. Due to their widespread applications in all sectors of the economy, such as power generation and transmission, construction, production of lithium-ion batteries and factory equipment and electronics, the price of these resources is set to continue to rise to meet the expectations of the global economy.
Copper–cobalt ores are characterised by high silica contents. These minerals partially dissolve during acidic sulphate leaching of the ores and significant amounts of silica report to the pregnant leach solution in various forms – one of them being colloidal silica. The presence of colloidal silica in the feed to the downstream solvent-extraction circuit creates extensive operating problems, including severe crud formation, difficulties in maintaining organic phase continuity, solid-liquid separation problems and poor cathode quality, amongst others.
As the leading producer of these commodities on the African continent, mining interruptions can cause massive economic and social crises within the DRC. In fact, challenges caused by process inefficiencies at major operations in the Copperbelt has seen the total shut down of some Solvent Extraction/Electrowinning (SX/EW) plants – a devastating blow to the economy. Innovative technologies are essential to mitigate the risk of ‘invisible’ and difficult to analyse colloidal silica, the root cause of many common inefficiencies.
Historically, removing the ultra-fine colloidal silica particles was a costly and time-consuming process with considerable downtime for the mine. These processes included maintaining a very high organic to the aqueous ratio in all the stages, at least a ratio above 2 to sustain organic phase continuity in all the SX stages, but sporadic instabilities were still observed and the SX could still not operate at its maximum capacity.
However, the innovation of a coagulant targeting silica molecules by Protea Mining Chemicals and Innospec, used to date in 4 mines across the DRC Copperbelt, is seeing a decrease in the concentration of colloidal silica and gels in a leach solution. At one site, a mine that was experiencing substantial loss saw 20% improved copper production and improved cathode quality production rates from less than 50% LME grade copper cathode on spec to more than to >99% on spec. By improving efficiencies, the mine showed a 9% improvement in revenue year on year from 2019 to 2020.
Developed over the past 7 years, primarily for use on copper ore, the product has improved operations to such an extent it is now being touted for use on any form of extraction operation that has a highly acidic leach with a solvent extraction process on it. This extends beyond the borders of DRC with plans to leach uranium and zinc operations across Zambia and Namibia in the pipeline.
With the global demand for sustainability and in turn an increased scrutiny on mines, another crucial benefit of the coagulant is the role it plays in green mining – the technologies, best practices and mine processes that are implemented as a means to reduce the environmental impacts associated with the extraction and processing of metals and minerals. In alignment with the UN’s Sustainable Development Goals (SDGs) the efficient extraction of both commodities contributes to Affordable and Clean Energy (SDG 7), Sustainable Cities and Communities (SDG 11) and Climate Action (SDG 13).
Mines have long lives. From copper to cobalt, nickel, uranium, zinc, and so forth, continuous innovation to develop the most effective processing solutions and increase efficiencies is a global challenge. The mining sector has traditionally been slow to adopt new technologies due to the scale and complexity of their operations. But if innovative technologies can exponentially increase operations and maximise yield, whilst saving costs and increasing bottom lines, the best course of action is to dig deep and embrace change.