Laizhou looks to double capacity

Partners BacTech Enviromet (YBA-V) of Toronto and Mintek of South Africa have successfully commissioned the Laizhou gold metallurgical bioleach plant in China’s Shandong province.

The facility can treat refractory gold concentrates from mines in the region and has an initial capacity of 65,000 oz. gold annually. Gold recoveries, following cyanidation of bacterial oxidation residue, are running at more than 97% using stockpiled concentrate feedstock. Reagent consumption is running about 9 kg cyanide and 14 kg lime per tonne.

"The Laizhou bioleach facility further demonstrates the viability and commercial potential of BacTech’s proprietary process technology," says Geoffrey Donohue, BacTech’s president. "It is a highly efficient and environmentally safe technology with the potential to fundamentally impact the mining industry."

Based on the encouraging results, Laizhou plans to build another reactor train to double the facility’s capacity.

In June, BacTech and Mintek signed a marketing agreement with Laizhou, which will act as the exclusive marketing and sales agent for the gold bioleaching technology for China, Korea, Siberia and Mongolia. The deal could be worth about US$1 million a year over 10 years for BacTech and Mintek.

Under the initial three-year agreement, Laizhou must complete at least two technology sales. The agreement can then be extended yearly, with Laizhou responsible for at least one sale per year.

BacTech and Mintek retain the first right to participate in any project made available to Laizhou and will provide technical support, including manuals, new technology information and advertising.

The fees for each technology sale will include a net smelter return royalty plus a net profits interest. They exclude reimbursable costs.

Under a working agreement between BacTech and Mintek, all rights to biotechnical innovations and developments are shared equally.

"As a result of the success of this project, we anticipate additional sales of bioleach technology in China in accordance with the marketing agreement,” says Donohue.

Bioleaching involves crushing the ore-bearing material, stacking it on plastic-lined pads and spraying it with a dilute sulphuric acid solution containing high-temperature thermophilic bacteria and nutrients. The solution drains through the heap, is recovered and is re-sprayed over the heap.

In the case of gold-bearing ore, the solution is recycled until sufficient sulphides have been oxidized to expose the gold. The residue is washed with water to remove acid and metals. It is treated with lime to neutralize any remaining acid. Then it is sprayed with cyanide for gold recovery.

Better gold recoveries may be achieved by processing the oxidized residue through a conventional milling-and-cyanidation circuit.

BacTech and Mintek are also conducting a feasibility study in a joint venture with Industrias Peoles of Mexico to build, own and operate a commercial bioleach treatment plant in Mexico. The plant would treat complex polymetallic copper concentrates.

Noranda (NRD-T) has teamed with Mintek and BacTech to study bioheap-leaching of chalcopyrite material. Noranda will invest $400,000 in work aimed at developing the technology and establishing its commercial viability.