Flood-affected Australian mines have the opportunity to boost productivity while decreasing the costs of environmental compliance, thanks to new tailings reclamation technology now being trialled in the Bowen Basin.
Devastating floods over summer have left production severely affected at many mines, at a time when the possible introduction of a carbon tax looms large for coal mine operators. If the mining sector is to continue providing a solid foundation for the Australian economy, creative answers are needed for both these challenges.
“Hydraulic mining of tailings dams and waste represents a strong future for Australian coal, not just for flood recovery, but for the ongoing profitability and environmental sustainability of the industry,” said Ross Garling, Managing Director of Hydraulic Mining Solutions.
Hydraulic mining uses jets of water under pressure to cut large quantities of material, converting them into a slurry to be transported to the processing plant. Once the slurry is formed, it flows along a pre-established channel and over a screen to remove debris. The pressure of the water and density of t he slurry are carefully monitored for effective outcomes.
Techniques originally developed by the English china clay mining industry, and refined in South Africa’s gold mines, are now being effectively used in Australian coal mines to reclaim valuable commodities from tailings waste, increasing profitability and mine life.
“The hydraulic mining of old was low pressure and relatively fixed in location, requiring large infrastructure to supply the necessary volumes of water,” Garling said. “Today’s hydraulic mining is markedly different, with higher pressures, lower water requirements, and low infrastructure costs.”
Pressures have been increased to 23-40 bar – variable to suit the conditions – creating consistently high-density slurries. Special nozzle designs project a concentrated jet for maximum energy impact at the face.
One high pressure water monitor is capable of mining 200 to 500 tonnes per hour of material, and multiple monitors can be used to increase throughput. High per-unit production means low costs for the mine operator.
The monitors can be mounted on remote controlled caterpillar-type tracks, allowing excellent mobility and low ground pressure. Water is delivered by steel and flexible HP lines, so that the high pressure pump station can remain in a constant location. The slurry can flow over distances, requiring only minimal moves for the slurry pump stations. “Because the monitors are so mobile and the water and slurry can be moved considerable distances, civil infrastructure costs are low,” said Garling. “Also, because this method of mining is so precise, it is ideal for controlled clean-up around existing infrastructure without the risk of damage.”
At the trial of hydraulic mining currently underway at a Central Queensland mine, outcomes have been very positive at a critical time for the industry. “We’re supplementing the feed into their coal washery, so they can produce more coal, at a time when many mines are short of coal production,” said Garling.
Hydraulic mining is also environmentally friendly when combined with SCL’s coal processing, it uses only 1/8 of the greenhouse gases used in conventional mining to produce a tonne of product coal, which earns it strong government support. “In some cases, mine operators can reduce their rehabilitation bonds,” he said.
The water used is largely recycled, and as there is little expressed water, there are minimal evaporation losses. Even seawater and process water are acceptable, where available.
The technique also enables cost-effective relocation of tailings for the rehabilitation of mine sites. “Once the slurry has been processed for extraction of the coal, effluent can be pumped into a location where it can be placed sustainably for the future – frequently underground,” said Garling. “Hydraulic mining represents an effective solution to the growing demand for coal tailings management in this country.”
By Hydraulic Mining Solutions www.hydraulicminingsolutions.com.au