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| CSIRO | SOLVE | Issue 9 | NOV 06 | |
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ARTICLE
WATER:
Designing Greener Pipelines By David Adams
With increasing concern over water use, scientists are examining how minerals processing pipelines can use less without compromising efficiencyFor decades the mining and minerals processing industries have used massive pipeline networks to flush waste materials to disposal sites. But growing pressure on the industry to reduce its water use is leading scientists to look at how the design of pipelines can reduce the amount of water needed to transport waste materials and, at the same time, actually increase the size of material that can be transported. CSIRO's Dr Murray Rudman is overseeing a three-year research project that aims to improve pipeline design by providing a fundamental understanding of the way in which solutions containing a high concentration of solids flow along them. "Typically, the kind of flows that we're looking at would be used in things like waste disposal in the mining industry – when they've finished processing and want to get rid of the fine particles left after the processing step, and the coarse rock they don't process at all," he says. "We're interested in understanding how these materials flow when you put them down a pipeline."
The latest project, which ends in May, follows an earlier study that found bigger rocks are not suspended in the slurry, even when common wisdom suggests they should be. Using an inclinable pipeline test facility built at the CSIRO Manufacturing and Materials Technology (CMMT) laboratories in Melbourne, the project is focusing on the effect pipes' angles have on the flow of materials. Dr Rudman says such information allows the development of models that can predict how high-concentration materials flow in a pipeline and what sort of 'pressure gradients' are required to ensure the most efficient movement. "That influences the type and size of pumps you'll need, and how much it's going to cost energy-wise and dollar-wise to move this material down the pipeline to a tailings facility or whatever." One of the drivers for the project is the need for water conservation, with Australia, South Africa and many South American countries pushing strongly for greater efficiency in water use. In mining, this often means reducing the amount of water pumped to waste disposal facilities. "If you can move materials down at a higher concentration there are advantages purely from the point of view of saving water, let alone the reduction in real estate and the deposit's mobility," says Dr Rudman. "That's one of the key motivating factors." He says there have already been situations where mines have been forced to shut down their plants due to a lack of water, costing mining companies millions of dollars in lost throughput. Although it is understood that most mining operations in Australia pay for water access and consumption, these charges are generally low.
Shortages may eventually result in the introduction of other fees by governments, as has been the case in South Africa, a move that would further increase the need to reduce water use as much as possible. Reducing the amount of water in solutions deposited at disposal facilities can also reduce the potential for damage to the surrounding environment. The danger 'mobile' mine tailings can pose was illustrated in Romania six years ago, when the wall of a disposal dam owned by Australian and Romanian joint venture Aurul broke open, spilling cyanide-tainted water into the Danube river system. If low-concentration material is kept at disposal sites, heavy rain can be calamitous because the material becomes 'just like water', Dr Rudman says. In contrast, the higher the concentration of solid material deposited at tailings sites, the less likely the tailings are to flow away from the disposal site and damage the environment. One of the project's sponsors, global resources company Rio Tinto, has already employed the research results – and in particular the computer modelling software called Pipe Tools, which has been developed out of the project's findings – to address issues at mine sites in Australia, Chile, the US and Canada. Although it has not been the main focus of the research, the project is also looking at 'vertical hoisting' – lifting material vertically out of mines. The project aims to determine whether transporting material in slurries via pipelines is a more economical way of getting mined materials to processing plants on the surface than traditional methods using haulage buckets or trucks. "Ultimately, it's going to come down to an economic assessment," Dr Rudman says. "There is not going to be a panacea or a catch-all for everything, but there will be some operations where there will be a clear economic benefit in utilising vertical hoisting and others where it will be more beneficial to use conventional methods." Dr Mark Coghill, principal adviser within Rio Tinto's Operational and Technical Excellence group, says the company plans to use CSIRO's pipe facility in Melbourne to investigate the possibility of using hydraulic conveying to transport ore from mines and for the disposal of coarse and fine tailings. For further information contact: |
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