Division of Information Technology, Engineering and the Environment
Applied Centre for Structural and Synchrotron Studies
Applied Centre for Structural and Synchrotron Studies
Project Duration: 2006-2008
Funding: Rio Tinto, ARC Linkage Grant
Chief Investigators: Roger Smart, Daniel Weissmann, Marek Zbik,** Rada Pushkarova,** Gayle Morris *
Description:
Millions of tonnes of tailings wastes, from
minerals separation processes, are produced in mining operations every
year. Huge volumes of these slurry streams, often <25% solids,
containing high clay content are disposed into dams and landfill.
Disposal of these wastes is costly, potentially environmentally
problematic and they usually contain very high volumes of precious
water. Expenditure for impoundments includes land acquisition,
perimeter wall construction, drains and slurry pipelines.
Environmentally, impoundments can lead to seepage, dust and loss
of visual amenity. The majority of water loss occurs as seepage,
evaporation and entrained capillary water. Clay settling in dams
can be very slow often requiring months before liquid separation and
solids removal. Costly chemical treatment may be required to allow
continual dumping. Reducing entrained water through designed
modification of clay aggregate structures can increase settling rates
and, importantly, consolidate bed density reducing land use. It
will also minimise pore space and correspondingly increase water
recovery.
We have shown that aggregate structures of clays (kaolinite and
smectites) can be changed from edge-face (EF) and edge-edge (EE)
stacking to the much denser face-face (FF) packing of clay platelets by
both chemical (reagent additions) and physical (degassing, ultrasonic
agitation) manipulations. The application of high power ultrasonics,
(US) offers major advantages of transportable technology, low running
costs and high throughput with in-stream sonotrodes. The
practical, industrial application of high power US has been shown in
initial empirical trials with high clay streams at Rio Tinto Labs
(Bundoora, Victoria) to produce increases in settling rates >50% and in
bed density by >25%. Both improvements may translate into
potential savings of $M in processing time, land area and water recovery
in minerals processing operations.
The initial trials were conducted by three partner organisations with complementary expertise and experience. The University of South Australia (IWRI** and ACeSSS) has specific expertise in techniques for mechanistic studies of tailings and consolidation and dewatering including a previous ARC SPIRT/Rio Tinto project (2001-2003); High Power Ultrasonics (HPU) P/L has research and application expertise in control of ultrasonic actions through power, amplitude, frequency and scale-up; Rio Tinto, as end-user in tailings thickener operation and tailings disposal, provides the operating experience and commercial focus.
This project has two general research aims in minerals processing,
focussing on ultrasonic (and other) modification of aggregate structures
and mineral surfaces; namely improved settling/densification; and
improved dewatering of high-clay tailings slurries. The ARC
Linkage project represents the fundamental research to accompany the
applied, Rio Tinto-supported project.
* Victoria University
** Ian Wark Research
Institute, University of South Australia
