Development and commercial demonstration of the BioCOP™ thermophile process
Introduction
The commercialisation of a new technology entails a large number of risks. Many of these risks can be mitigated by the manner in which the technology is developed from the conceptual stage to a commercial operation. The types of risks that can be easily reduced revolve around the physical characteristics of the process and its requirements. There are a considerable number of other risks when commercialising a new technology. These range from the unforeseen to simple problems of human nature, such as focusing on the novel to the detriment of support unit operations.
This paper leads you through the initial stages of development of the BioCOP™ technology through to the construction of a 200 t per day (tpd) prototype plant at Chuquicamata in Chile.
Section snippets
The concept
The first bioleach laboratory tests were performed in the seventies and possibly even before. BHP Billiton's Johannesburg Technology Centre (JTC), then known as Genmin Process Research, was very involved with the subsequent development and commercialisation of BIOX® process. The BIOX® process utilised mesophilic microorganisms (± 40 °C) to oxidise sulphide minerals to liberate gold in refractory sulphide gold concentrates. The minerals involved were mainly pyrite, pyrrohtite and arsenopyrite.
Laboratory test phase
The first laboratory tests on a copper concentrate were performed at JTC in 1995. Batch type tests involve slurrying a concentrate sample at a predetermined percent solids in a small agitated reactor vessel. The slurry is then pH-stabilised, inoculated and process parameters such as dissolved oxygen are monitored and controlled. The results of these laboratory tests start to give an understanding of the process.
Results of laboratory tests and start of thermophile technology
Initial tests showed that the standard mesophile (40 °C) culture was very successful at oxidising secondary sulphide minerals, but was not effective for primary copper sulphide minerals especially chalcopyrite. Oxidation of chalcopyrite stopped at a relatively low oxidation value (30%–60%) and additional leach time failed to improve recovery. The mesophile technology still has applications, but for concentrates with high chalcopyrite, something new was needed.
A thermophilic microorganism was
Results of piloting
The first thermophile pilot trials on a copper concentrate began in 1995 in a small test unit with reactors of 10 L each. In 1997, the first of two larger pilot units was constructed. This unit consisted of two 240-L stirred tanks operating in parallel as primary reactors. These overflowed to four 140-L stirred tanks operating in series as secondary reactors. Each reactor was equipped with independent temperature control and independent gas mass flow meters. The gas flow meters allowed mixing
Determining scale-up parameters – 5-m3 reactor and ITR facility
There were two projects to look at the engineering requirements for an industrial plant. The first was a 5-m3 single reactor built and operated at JTC's facility in Randburg, Gauteng, South Africa. Later, a second much larger project known as the Industrial Test Reactor Facility (ITR) was built at the Pering mine, Reivilo, Northwest Province, South Africa. The ITR facility consisted of a 50-m3 and 300-m3 reactor.
20KTPA cathode prototype plant
A joint venture company called Alliance Copper Limited was formed between BHP Billiton and Codelco. The purpose of Alliance Copper was to exploit the BioCOP™ technology. The BioCOP™ encompasses both mesophile and thermophile technologies. Of the two processes, mesophile operations are well understood and it is the thermophile process that required prototyping for confidence.
Pilot plant test work had been carried out at the Codelco mine of Chuquicamata in Chile since 1997. BHP Billiton conducted
Acknowledgements
Many thanks to the personnel from BHP Billiton Johannesburg Technology Centre through whose work this technology came into existence. Many thanks to the personnel of Alliance Copper through whose dedication the Prototype plant continues to be a source of pride and thanks to our joint venture partner Codelco for their efforts.
Reference (1)
Milestone for Bioleaching
Mining Journal
(2001 March 9)
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