Hydraulic mining cannons shooting water at 30-40 bar pressure will help release the value of tailings at the Century zinc site in Queensland’s lower Gulf.
New Century Resources manager – mine technical services Tim Edwards said this would be the largest hydro-mining operation in Australian history.
“We have engaged National Pump and Energy (NPE) as our mining contractor and subcontracting to them is a company called Paragon Tailings – a hydraulic mining specialist,” he said.
The tailings deposit at the Century site has a proven ore reserve of 77.3 million tonnes at 3.1 per cent zinc.
The hydraulic mining operation will draw water from site’s evaporation dam, which is adjacent to the tailings dam.
“We pump the water from the evaporation dam to a pump station, where we have a series of high-pressure pumps to send the water out to the hydraulic mining cannons,” Mr Edwards said.
“It is like a really big fire hose mounted on a bob cat and the pressures are extreme – 30-40 bar.”
New Century Resources has four hydraulic mining cannons, with two deployed for mining at any time and two acting as back-up.
Mr Edwards said steel pipe carried the water under pressure to the machines, meaning lengths of steel had to be shifted and reconnected as the mining progressed.
In preparation for the start of mining, a sump 12m deep was excavated into the tailings surface using trucks and excavators, Mr Edwards said.
The hydraulic cannons are used to cut the hardened tailings material back into that sump.
“The cannons fluidise the tailings,” Mr Edwards said.
“The aim is to get the tailings into suspension into the water and it gravity feeds into the sump.
“We have four submersible slurry pumps that pump the tailings slurry through a vibrating screen.”
It is then pumped through an 8km pipeline from the dam to the concentrator.
This is powered by two 500KW slurry pumps.
Mr Edwards said about 1000 dry tonnes an hour of tailings would be pumped back to the concentrator for processing – or about 33,000 cubic metres a day (24,000 dry tonnes).
“The scale is the really impressive thing at Century” he said. “We’re starting at 8Mtpa and moving to 15Mtpa.”
The operational mining team includes seven NPE personnel and 25 from Paragon.
Paragon runs a number of large hydro-mining operations globally, including a 15Mtpa tailings hydraulic mining operation at Morila gold mine in Mali.
NPE and Paragon are also working together on a planned hydraulic mining operation at the Woodlawn zinc-copper project in New South Wales.