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| CSIRO | SOLVE | Issue 5 Nov 05 | |
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ARTICLE
MINERALS PROCESSING: Microwave Gets the Recipe Right
By Rebecca Thyer
In the often dusty, dry environment of Australia’s mining industry, water plays an important role in the handling of raw materials. Too much water can make materials difficult to work with; too little means dust remains an issue. It is one of those background technical dilemmas that is important to get right and the industry is now drawing on a new microwave development – low-frequency microwave (LFM) moisture technology, developed by CSIRO Minerals. LFM analysers have been developed for coal and iron ore to provide accurate, continuous moisture control so that the correct amount of water can be added from mine to port, improving product quality, minimising dust and making the most of limited water supplies. Graeme McGown, managing director of a new CSIRO commercial spin-off company, Intalysis Pty Ltd, says the latest, second-generation analysers have an important role to play for minerals processors operating in Australia’s dry environment, where ores with fine particles can cause handling problems. “Getting the moisture content right not only minimises dust, but is also important for meeting maximum shipping moisture limits and customer specifications,” he says. The technology works by transmitting low-frequency microwaves through the material while it is on a conveyor belt. Moisture content is determined by measuring microwave phase shift and attenuation. Mr McGown says moisture control is particularly critical at ports, especially as they grow and start to expand close to existing communities: “Towns need protection from dust, while port operators might need to make the most of a scarce resource like fresh water.” The technology also continues to have a role at sea: “If maximum shipping moisture levels are exceeded, the cargo may shift in rough weather, causing stability problems,” he says. While the technology is important for materials handling, it also has a part to play in processing operations in which moisture control is essential in agglomeration processes, such as pelletising or sintering. “Small changes from optimum moisture can critically affect the quality of blast furnace feed.” The value of moisture control is well recognised by the minerals processing industry. Resource giant BHP Billiton and infrastructure investor Babcock & Brown Infrastructure (formerly known as Prime Infrastructure) use the LFM Pilbara and LFM Bowen moisture analysers in their iron ore and coal operations. BHP Billiton senior process engineer John Groves says moisture control is an important element in the company’s iron ore operations. “The LFM system gives us accurate, on-line measurements that enable us to successfully implement our moisture control strategy.” The company initially introduced the LFM technology with trials on its Marra Mamba ore types, adding small amounts of water at frequent intervals. It has since extended these trials to include traditional hematitic and pisolitic ores, and is investing in further LFM Pilbara units after the technology helped it to optimise moisture control. A sister analyser – the LFM Bowen moisture analyser – has been specifically tailored for the coal industry and is being used by Babcock & Brown’s Dalrymple Bay Coal Terminal in Queensland, one of the world’s largest coal export terminals. The Bowen system provides the company with moisture readings for coal on plant conveyors, allowing operators to improve coal handling and dust suppression. LFM technology can also have a reverse role in situations where wet material needs drying. Mr McGown says this broadening application augurs well for the technology’s increasing reach into global minerals processing markets.
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