The start-up Still Bright intends to replace environmentally harmful copper smelters with a new chemical process.
The demand for copper is increasing rapidly – as is the environmental pollution caused by its dirty production processes. The founders of the start-up Still Bright claim to have found a better and cleaner method: the company uses water-based reactions based on battery chemistry technology to purify copper in a process that could be less harmful to the environment than conventional smelting. The hope is that this alternative will also help to reduce the growing burden on the copper supply chain, as the US journal MIT Technology Review from the Massachusetts Institute of Technology reports in a recent article. “We are really focussed on overcoming the looming copper supply crisis,” the magazine quotes Randy Allen, co-founder and CEO of Still Bright.
Today, copper is an important component of everything from electrical wiring to cookware. Renewable energies and electromobility, with their considerable copper requirements for photovoltaic systems and electric vehicles, are creating even greater demand. According to MIT, global demand for copper is expected to increase by 40 per cent by 2040.
As demand rises, so too does the impact of copper extraction – the process of refining ore into pure metal – on the climate and the environment, as Technology Review writes. There is also growing concern about the geographical concentration of the copper supply chain. Copper is mined and smelted all over the world. In the past, many of these mines had their own smelting plants for processing the extracted ore, mainly using smelting metallurgy (pyrometallurgy). In pyrometallurgical smelting in the copper smelter, copper is melted from ore or recycled scrap in a multi-stage process by heating it to its melting point. This process takes place in fuel or induction furnaces, where the molten metal is processed, alloyed if necessary, and then cast into finished products. Today, the smelting industry has consolidated, with many mines supplying copper concentrates to smelting plants in Asia, particularly in China.
This is partly due to the fact that smelting consumes a lot of energy and chemicals and can be the cause of sulphurous emissions that affect air quality. “They have moved the environmental and social problems elsewhere,” says Simon Jowitt, professor at the University of Nevada, Reno, and director of the Nevada Bureau of Mines and Geology. It is possible to remove pollutants from a smelter’s emissions, and smelters today are much cleaner than they used to be, says Jowitt. Overall, though, principal smelting locations are not exactly known for their environmental responsibility, writes author Casey Crownhart. Even countries such as the USA, which have abundant copper reserves and active mines, subsequently send copper concentrates containing up to around 30% copper, mostly for smelting, to China or other countries. There are currently only two operating ore smelters in the USA.
Abandoning the pyrometallurgical process
Still Bright has abandoned the pyrometallurgical process used by smelters in favour of a chemical approach inspired in part by vanadium liquid battery technology. In the Still Bright’s reactor, vanadium reacts with the copper compounds in copper concentrates. The copper metal remains solid, while many of the impurities remain in the liquid phase. The entire process takes between 30 and 90 minutes. The solid, which contains around 70% copper after this reaction, can then be fed into another process established in the mining industry, known as solvent extraction and electrowinning, to produce copper with a purity of over 99%. This is by no means the first attempt to process copper using a water-based chemical process. These days, for example, some copper ore is processed with acid, and Ceibo, a start-up company based in Chile, is trying to apply a variant of this process to the type of copper that is traditionally smelted. The difference here lies in the special chemistry, in particular the decision to use vanadium.
Jon Vardner, one of the founders of Still Bright, was researching copper reactions and vanadium flow batteries when he came up with the idea of combining a copper extraction reaction with an electrical charging step in which the vanadium can be recycled. After the vanadium has reacted with the copper, the liquid mixture can be fed into an electrolyser, which uses electricity to convert the vanadium back into a form that can react with copper again. This is basically the same process that vanadium flow batteries use for charging. While other chemical processes for copper plating require high temperatures or extremely acidic conditions to dissolve the copper, drive the reaction quickly and ensure that all the copper reacts, Still Bright’s process can be carried out at ambient temperatures.
One of the biggest advantages of this approach is the reduction in environmental pollution caused by copper plating. In traditional smelting, the target material is heated to over 1,200°C, which produces sulphurous gases that are released into the atmosphere. Instead, the Still Bright process produces hydrogen sulphide gas as a by-product. It’s still a toxic substance, but it can be effectively captured and converted into useful by-products, Allen says. Another potential source of pollution is the sulphide minerals remaining after the refining process, which can form sulphuric acid on contact with air and water. This is also known as acid mine drainage and it often occurs with mining waste. Acidic drains like these also arise during the Still Bright process, and the company plans to monitor these carefully to ensure that they do not get into the groundwater.
The company is currently testing its process in a laboratory in New Jersey and is planning to build a pilot plant in Colorado, which will have a capacity of around two tonnes of copper per year. The next step is to build a demonstration-scale reactor with an annual capacity of 500 tonnes, which is scheduled to go into operation in a mine in 2027 or 2028, says Allen. Still Bright recently completed a seed capital round totalling 18.7 million dollars to drive the scaling process forward. How it scales will be a crucial test of the technology and whether the typically conservative mining industry will follow suit, says UNR’s Jowitt: “We’re waiting to see what happens on an industrial scale. And I think until it’s a reality, people might be a little hesitant to get involved.”
Source: MIT Technology Review
