Hydraulic mining techniques currently being trialled successfully in Queensland coal mines can be extended across a wide array of minerals, Hydraulic Mining Solutions (HMS), an Australian-South African joint venture established in 2009, is at the forefront of this developing industry.
Hydraulic mining allows cost-effective and environmentally sustainable management of tailings, for most sectors of the Australian mining industry. “This method can be used on anything soft, from beach sands to clay,” said Dave Prentice, Operations Manager of HMS. “As long as there is water available and the grain size is small, we can mine it.”
As well as tailings re-mining, the HMS process is suited to river clean-ups and the mining of soft deposits such as laterites, alluvials, clay and talc. Trash can be screened from the slurry before it is pumped to the processing plant.
HMS is a joint venture between Australian-based company Superior Coal, and South Africa’s Fraser Alexander Tailings. Superior Coal has been remining, reprocessing and rehabilitating coal tailings and coarse rejects in Australia since 2004. Fraser Alexander, who have been operating for 100 years, has unparalleled expertise in hydraulic mining, currently moving approximately 100mt pa hydraulically and is the world’s largest hydraulic mining contractor. The variety of tailings mined thus far includes gold, platinum, kimberlite, iron, copper, magnetite, coal, gypsum, heavy mineral sands, andalusite, chrome, ferrochrome, zinc and nickel.
The specialist techniques employed by HMS were refined over the past 50 years, particularly while mining gold tailings dumps, and drawing on some of the latest technology from China clay mining in the United Kingdom. Fraser Alexander currently produces 1.2-1.8 million tonnes per month from each of two gold tailings dumps around Johannesburg.
Hydraulic mining itself is now new to Australia, having been used for more than a hundred years for alluvial and tailings deposits in tin and gold mining areas in Tasmania and Queensland. However, the techniques employed by HMS today are markedly different.
“We use much higher pressures, typically in the order of 30 bar, but variable to suit the conditions,” said Prentice. “The high intensity jetting provides a consistent fine slurry to the mill for reprocessing, with no clay balls.”
“This allows us to use much less water,” he said, “and the water is also generally recyclable. The only water is between the monitor and the slurry pump, so evaporation losses are also minimised.”
Consistently high densities of 30-50 percent solids have been achieved, depending on the tailings characteristics, and this is the key to effective hydraulic mining production. “High slurry densities are achieved through constant vigilance, specialist techniques and skill,” said Prentice. “Otherwise many materials, particularly clay, tend to break into clods which settle out in launders or are caught on screens, reducing production. Our team is highly experienced, and has the skill to achieve a concentrated stream of slurry, inhibiting meandering, velocity losses and settlement of solids.”
The equipment can be track mounted, remote controlled, and utilises flexible supply hoses, making it highly manoeuvrable. This means infrastructure costs are kept very low.
“The process allows good visual control, to mine cleanly, safely, and efficiently, while protecting existing infrastructure,” said Prentice. “HMS can operate under most weather conditions, and there is no requirement for trucks or haulers. Being a wet process, there are no dust emissions to control. It is the most cost-effective recovery method available.”
“HMS offers mine operators a cost-effective, safe and environmentally sound way to recover their tailings and reduce their footprint.”