Traditionally, spiral concentrators have not been widely employed in the separation process of minerals like copper, lithium, tin and tantalite, but all that is changing fast, according to Graeme Smith, application representative at Multotec Process Equipment.
“The move to spirals is highly significant because these commodities are being extensively used in technologies of the future, such as electric cars and cellular phones,” says Smith. “With the exponential growth that is expected in these kinds of products, the demand for these minerals is also sure to climb – potentially leading even to shortages of supply.”
While lithium is important to battery production, tantalite is used in resistors and capacitors, and copper and tin remain key contributors to electroconductivity.
“Spirals have now been proving their worth in economically treating these minerals, generating high value concentrate while reducing the size and cost of downstream processing,” he says.
In tin and tantalite mines – which tend to be much smaller operations relying on conventional technologies like low-volume shaking tables – spirals have been performing a bulk reduction function that allows up to 75% of the waste material to be discarded before product reports to downstream circuits.
“Tantalite’s head grade, for instance, is generally between 0,05% and 0,1% mineral in the run-of-mine (ROM) stream, while tin and copper are between 1% and 3% in the initial feed,” says Smith. “Compare this to traditional heavy-type minerals such as chrome and iron ore, where the comparison could be 15% to 45%.”
He emphasises, therefore, how bulk reduction in commodities like copper, tin and tantalite can play an important role in reducing capital costs and raising productivity. In copper mines in the Democratic Republic of Congo, Zambia and Zimbabwe, Multotec’s spirals have enabled copper ore to be upgraded into a high grade copper concentrate, upgrading from 1-3% to 20%-plus copper.
“These mines can sell the upgraded copper concentrate without having to immediately invest in leaching or electro-winning processes,” he says. “Spirals can also be applied as a bulk reduction strategy to achieve a higher-grade material for more efficient leaching.”
Multotec has also had considerable success in recent years with the separation and concentration of tin. Working with tin mining projects in Spain, Morocco and the DRC, Multotec spirals have succeeded in raising the initial head grades of 1-3% to achieve 50% or more tin in concentrate.
“Spiral technology can replace the traditional shaking table circuit – which often is accompanied by magnetics and flotation – but it can also be added to the process circuit prior to the shaking table phase,” he says. “This allows existing downstream processes to become more efficient due to higher grades and the removal of waste by upgrading the ore creates extra production capacity in downstream processes.”
An example of this has also been achieved in a tantalite tailings operation in the DRC, where spirals perform massive bulk reduction and upgrading, while the shaking tables clean the final product.
“Here, the deployment of two 20 tonne per hour test plants concentrates 40 tonnes per hour of low-grade material into just 200 kilograms per day of final material – a remarkably efficient concentration process,” he says. “For high value commodities like tantalite, spirals can therefore play a key role in economically improving low head grades.”
To deal with the remote location of many of these African sites, the Multotec solution can be provided in a modular format for which the company has become well known.
“These 20 tonnes per hour test plants can be transported in two standard containers; one of 12 metres in length and the other of 6 metres,” says Smith. “It is therefore much easier to move than a conventional, fixed structure.”
In another recent breakthrough, Multotec’s test work in the use of spirals to concentrate lithium has resulted in some remarkable findings.
In its pioneering test work to date, Multotec has shown that a 70% concentration of petalite can be achieved. Further test work hopes to achieve an 80% concentration, which would allow the element to directly enter the lithium carbonate circuit without passing through a flotation stage.
Beyond mining, the company has also conducted tests on the separation of electronic waste, to recover these high-value minerals from recycled electronic devices.
“Our work has included the separation of precious minerals from fibrous material in printed circuit (PC) boards, which are crushed, granulated into powdered form and fed into spiral concentrators,” he says.
He highlights the extraordinary value to be gained by ‘mining’ e-waste efficiently, given the relatively high levels of valuable minerals to be found in a cellular phone. Based on its total weight of about 100 grams, a recycled phone contains 13,7 grams of copper, 0,28 grams of gold and 0,014 grams of palladium.
“Recycling this device can release much higher mineral values than a typical ROM stream,” Smith explains. “For example, it contains 13-15% copper metal compared to 1-3% in ROM, some 2,8 g/t gold compared to 1-4 g/t in ROM, and 140 g/t palladium compared to 2-4 g/t in ROM.”