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Gold/Mining/Energy : ECHARTERS -- Ignore unavailable to you. Want to Upgrade?

To: Al Cern who wrote (2148)	1/7/1998 10:17:00 PM
From: Aurum	Respond to of 3744

Al, a company called Wiluna Mines Limited (ASX code WNA) operates a "Biox" plant at Wiluna, Western Australia. The plant has been working since 1993 and, apart from some teething problems it has worked well. The Wiluna ore is very refractory (ie. it is difficult to achieve a satisfactory recovery rate with conventional treatment processes). The "Biox" process was developed by a large South African company (Gencore I think, but I night be wrong) and there are several plants working around the world now using this process. A similar process was developed by an Australian company but I don't know what happened to it. These processes work by recovering the sulphides by conventional methods (such as froth floatation, gravity methods etc). The sulphide concentrate is then put in an tank (as a continuous process) with nutients and a certain strain of thiobacillus (ie. a "sulphur" bacteria) which will eat into the sulphide grains (the bacteria use the sulphide as a food source). Mostly, refractory gold in sulphides (usually pyrite) occurs along zones of dislocation and stress. It just so happens that it is along these zones that the bacteria attact and dissolve the sulphide away, exposing the gold grains. Only 10-20% of the sulphide usually has to be eaten away to liberate most of the gold. After the sulphide concentrate has been treated by the thiobacillus the gold is recovered by the conventional carbon in pulp cyanide process. The thiobacillus works best at warm temperatures, but I seem to remember that one of the teething troubles at Wiluna was that the temperature got so high (from the energy expended by the bacteria) that it killed the bacteria. once the reaction starts a major problem is getting rid of the waste heat (ie. cooling). This is a problem in Western Australia, but may not be a problem in Canada. Aurum