Gold
Feature Articles
Technological Developments in Gold Mining
September 2021
While the global demand for gold is expected to grow over the long term, the global mined supply is expected to peak in 2022 before steadily decreasing as ore grades decline and large mining projects reach the end of their lives. The price of gold is not expected to rise at the same rate as demand, so miners will be incentivised to find more efficient and cost-effective ways of extracting gold from this lower-grade ore.

At the same time, mining companies are under increasing pressure to lower the environmental impact of their operations, and this trend is set to continue for the foreseeable future. With environmental regulations tightening worldwide and shareholders becoming more environmentally conscious, gold miners will be obliged to lower their greenhouse gas emissions and decrease their use of toxic chemicals such as cyanide in order to continue to operate. This, along with the need for more efficient operation, necessitates innovation in the industry.

One of the major developments taking place in gold mining and in the mining industry generally is the shift to renewable energy, with gold mining companies such as Polyus already using renewable energy to power 90% of their gold production. Many gold miners are investigating new technologies with the potential to facilitate this shift. Numerous other new and established technologies, aimed at both increasing the efficiency of gold mines and decreasing their environmental impact, are also being trialled and used by gold mining companies around the world.

 

Rio2

Rio2 is involved in a trial of gold processing technology which uses molecularly imprinted polymers, rather than activated carbon, to recover gold from cyanide leach. In August, the miner signed a contract with Sixth Wave Innovations which will enable the continued testing of Sixth Wave’s patented IXOS purification polymer at Rio2’s Fenix Gold Project in Chile. Sixth Wave began the testing in September 2020 at its facility in Utah, and testing will now move to Rio2’s Lince Infrastructure facilities near the Fenix site.

The IXOS polymer is reusable, and previous tests indicate that it outperforms activated carbon on several fronts, being faster, cleaner and more cost-effective. The next stage of testing will involve 50 days of onsite testing of the IXOS polymer, with parallel testing on activated carbon leaching columns. If the testing is successful, the companies will proceed with the next stage of testing, incorporating the new technology into a long-term pilot plant which will operate alongside a planned carbon adsorption circuit. This will provide specifications for full-scale implementation of the new technology.

 

Gold Fields

The South African mining company Gold Fields has ordered three Metso Vertical Plate Pressure Filters, with all the associated equipment for dry tailings processing, for its Salares Norte site in Chile. Gold Fields ordered the pressure filters from the Finnish industrial machinery company Metso Outotec, and they are set for commissioning in 2022.

Dry tailings processing involves the dewatering of mine tailings to achieve less than 20% moisture content, followed by reuse of the water and storage of the remaining “dry” material in an unsaturated tailings deposit. This form of tailings management is both safer and more water efficient than the traditional method.

Dry tailings processing is particularly appropriate for use at the Salares Norte mine. The site is located 4500m above sea level in the Andean Mountains, where water is scarce and water efficiency is particularly important in mining operations.

 

 

Barrick

Barrick Gold Corporation has joined the “Charge On” Innovation Challenge, a competition launched by BHP, Vale and Rio Tinto in partnership with Austmine, Australia’s leading mining equipment, technology and services industry association. The aim of the competition is to develop new concepts and solutions for large-scale haul truck electrification, and the challenge is to develop a solution that will safely deliver electricity to large surface haul trucks without adding time to the haul cycle. This is expected not only to provide a zero-carbon energy source but to potentially unlock value, as electric motors have fewer moving parts than standard equipment.

Over 350 companies from across 19 industries have registered their interest as vendors, with 80 companies submitting formal expressions of interest. With the help of Austmine, the patrons of the challenge will evaluate proposals over the next month to create a short-list of vendors to submit formal proposals. Site trials of the chosen solution are expected to start within the next few years.

Many companies are currently looking for ways to reduce the greenhouse gas emissions associated with mining, and the decarbonisation of mining fleets would reduce the emissions produced by surface mining operations.

 

Evolution

To increase the efficiency of its operations, Evolution Mining has deployed Aspen Technology’s Mtell plant monitoring software at its Mungari Gold Operations in Western Australia. The software utilises historical and real-time operational and maintenance data to identify specific failure signatures. This allows it to predict impending asset breakdowns and thus assists in preventing them.

Evolution plans to use the software to help mitigate unplanned downtime and optimise operations.

 

Itronics

At the beginning of the year, US-based cleantech materials growth company Itronics announced that it had developed a process capable of recovering silver and gold, as well as base and ferrous metals, nutrient materials, and industrial minerals, from “sub-ore grade” mine tailings. The process, called Rock Kleen Tailings Processing Technology, also neutralises residual cyanide from the leaching process.

The use of cyanide in the gold recovery process is associated with both environmental damage and human safety risks. As a result, it is controversial, and the use of cyanide in heap-leach applications is now banned in several countries. There has therefore been a long search for alternatives to the use of cyanide in gold mining. One solution which has already been utilised by Barrick Gold Corporation, among others, is the replacement of cyanide with a safer chemical reagent called thiosulphate. Itronics’ new technology offers another solution which also unlocks value from mine waste materials.

 

 

Technological Solutions

In future, gold mining companies will be required to increase the efficiency and cost-effectiveness of their operations to counter the declining grade of ore and associated rise in the costs of production. At the same time, they will be obliged by increasing pressure from governments, investors and communities to decrease their environmental footprint. Many are therefore testing, using or contributing to the creation of technologies capable of bringing them closer to these goals. New technologies capable of simultaneously improving the environmental footprint and the cost-effectiveness of mines are particularly promising. Many have recently become available, and mining and other companies are taking steps to develop more.