Tailings energise renewables vision
Waste tailings from a former gold mine in Australia could become a new source of silicon for the solar power sector.
The mine, based at Smeaton in Victoria, covers a licensed area of 325 km2, although not all this area is in use. At the moment, the waste generates a supply of quartz – the primary source for silica – for the construction sector, produced by Creswick Quartz for the last 15 years. The company says its quartz is of a high quality, because impurity levels are low. As a result, it is considering converting some of it to an unusually pure grade silicon feedstock (at least 99.995% pure silica) needed by solar panel manufacturers.
The potential benefits are a reduction in mining waste from the area, in addition to a new supply of high quality raw material to the solar industry that could reduce costs and carbon emissions. ‘It has advantages other products can’t match in terms of [low] boron and phosphorus content,’ asserts Chris Karamountzos, Creswick’s CEO.
Solar-grade silicon is currently manufactured from scraps of semiconductor-grade silicon, which involves chlorination. Demand is exceeding supply, and the team at Creswick sees a gap in the market for high-purity feedstocks for solar panel manufacture.
Dr Hal Aral, a scientist at Australia’s Commonwealth Scientific and Industrial Research Organisation, has been developing an environmentally friendly and commercially viable quartz purification process for this purpose by applying water wash. He says this generates high purity quartz that can be below 100ppm total impurities.
For higher purity applications, caustic and acid leach treatment can be used as their waste streams neutralise each other when mixed, which is said to make the process environmentally more acceptable than direct acid leach. The neutralisation process, Aral insists, does not generate much solid waste because the Creswick quartz contains a very small amount of impurities to start with.
He adds, ‘Removal of these tails puts the landscape to its original form. This is because the removal process does not impact upon the surface by way of extraction at all.’
No decisions, however, have been made as to whether to continue with the project. A million tonnes of tailings are available. If the company continues to use the tailings for the broader category of quartz, it estimates it will run out of waste tailings above ground in a shorter space of time and need to drill some of the material underground. So it hopes to build a processing plant to produce ultra-pure quartz. This, says Karamountzos, would be likely to have a 30-year life span.
Professor John Monhemius, a mining engineer at Imperial College London, UK, draws attention to the abundance of quartz on this planet, but adds, ‘this quartz is pretty pure so that’s unusual. Ultra-pure quartz has a certain market value’. However, he also points out, ‘Pure quartz is not likely to be causing environmental problems and is pretty inert anyway. It’s more about removing an eyesore’. Other types of pure quartz are available, for example, in Brazil. The big advantage, Monhemius indicates, is that the company does not have to mine it, thus lowering its costs.
Materials World Magazine, 03 Sep 2010
The mine, based at Smeaton in Victoria, covers a licensed area of 325 km2, although not all this area is in use. At the moment, the waste generates a supply of quartz – the primary source for silica – for the construction sector, produced by Creswick Quartz for the last 15 years. The company says its quartz is of a high quality, because impurity levels are low. As a result, it is considering converting some of it to an unusually pure grade silicon feedstock (at least 99.995% pure silica) needed by solar panel manufacturers.
The potential benefits are a reduction in mining waste from the area, in addition to a new supply of high quality raw material to the solar industry that could reduce costs and carbon emissions. ‘It has advantages other products can’t match in terms of [low] boron and phosphorus content,’ asserts Chris Karamountzos, Creswick’s CEO.
Solar-grade silicon is currently manufactured from scraps of semiconductor-grade silicon, which involves chlorination. Demand is exceeding supply, and the team at Creswick sees a gap in the market for high-purity feedstocks for solar panel manufacture.
Dr Hal Aral, a scientist at Australia’s Commonwealth Scientific and Industrial Research Organisation, has been developing an environmentally friendly and commercially viable quartz purification process for this purpose by applying water wash. He says this generates high purity quartz that can be below 100ppm total impurities.
For higher purity applications, caustic and acid leach treatment can be used as their waste streams neutralise each other when mixed, which is said to make the process environmentally more acceptable than direct acid leach. The neutralisation process, Aral insists, does not generate much solid waste because the Creswick quartz contains a very small amount of impurities to start with.
He adds, ‘Removal of these tails puts the landscape to its original form. This is because the removal process does not impact upon the surface by way of extraction at all.’
No decisions, however, have been made as to whether to continue with the project. A million tonnes of tailings are available. If the company continues to use the tailings for the broader category of quartz, it estimates it will run out of waste tailings above ground in a shorter space of time and need to drill some of the material underground. So it hopes to build a processing plant to produce ultra-pure quartz. This, says Karamountzos, would be likely to have a 30-year life span.
Professor John Monhemius, a mining engineer at Imperial College London, UK, draws attention to the abundance of quartz on this planet, but adds, ‘this quartz is pretty pure so that’s unusual. Ultra-pure quartz has a certain market value’. However, he also points out, ‘Pure quartz is not likely to be causing environmental problems and is pretty inert anyway. It’s more about removing an eyesore’. Other types of pure quartz are available, for example, in Brazil. The big advantage, Monhemius indicates, is that the company does not have to mine it, thus lowering its costs.
Materials World Magazine, 03 Sep 2010
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