Outotec, a company that specializes in paste and high-rate thickening technology, is at the forefront of the trend toward adoption of this technology. Not only has the company designed and installed the first-ever paste thickener in Australia’s coal industry but has also recently won five further orders in the past year alone for paste and high-rate thickeners.
“Here in Australia we are leading the field in adoption of this technology into the coal industry. We expect this to expand even further as environmental demands and risk management policies make paste and high rate thickeners increasingly attractive,” said Brad Garraway, global technology development manager-thickening.
Even though paste thickening is fairly common for treating tailings at metal mines, many coal operators are unfamiliar with the practice. “Thorough test work is essential for the correct sizing and configuration of thickeners,” said Garraway. “Outotec has a range of dynamic bench and pilot scale test work techniques, which accurately simulate the high-rate principle. Outotec deep bed test units for high compression and paste applications have been invaluable for the coal industry.
“Our reliable test work has also enabled us to give performance guarantees, that have been vindicated by subsequent results,” said Garraway.
Another emerging trend in the coal industry is the use of bolted tanks in the design. Outotec’s design radically reduces site installation time, as the bolted tank can be delivered pre-painted with no site welding required. Bolted thickeners are also much easier to relocate should future operations require. Bolted designs have been specified for:

Carborough Downs (Queensland), 25-m diameter Outotec High Rate Thickener (HRT) bolted tank with patented Outotec Turbodil feed dilution system installed early in 2009. (Turbodil is a forced dilution system, upstream of the feedwell.)

Stockton Opencast mine (New Zealand), 24-m HRT bolted tank supplied and to be installed in 2009 with Outotec Vane Feedwell. The recently launched, high performance Vane Feedwell is Outotec’s global standard feedwell. Mt Arthur Coal (New South Wales), 35-m HRT bolted tank with both Vane Feedwell and Turbodil 2010 supply and install.

Clermont Coal (Queensland), 12-m Outotec High Compression Paste Thickener (HCPT) bolted tank scheduled for installation in the first quarter of 2010.

Bulga Coal (New South Wales), 18-m HCPT bolted tank installed September 2007.

Another recent Outotec coal project includes Cameby Downs (Queensland), 22-m HRT piecewise tank with Turbodil installation first quarter of 2010.
At one major coal preparation plant, an Outotec paste thickener installation was designed to save water and also reduce the tailings space required. Outotec’s professional and credible test work program was a key factor in the subsequent award for Australia’s first coal paste thickener, explained Garraway.
“The client also weighed up factors including industry experience, process guarantees and value for money and Outotec’s thickening solutions really impressed in this regard,” Garraway said. “Real total cost is also a prime consideration. More and more sites are now comparing not only initial capital outlay but also ongoing operational and maintenance costs. This is where some suppliers can really differ.”

Pumping Thickener Underflow Slurry
The heavy-duty Bredel SPX peristaltic pump is an effective solution for pumping thickener underflow slurries with specific gravities of up to 2.2. Advanced hose technology enables these units to pump harsh underflow thickener dependably for long periods of time. Peristaltic pumps are virtually maintenance free with no expensive seals to replace, no check valves to clog, and no rotors and stators to wear out. Unlike other pump types, the high levels of abrasives in the slurry do not affect pump life. With the self-loading design, hose replacement is quick and easy. The combination of these features make the Bredel SPX an enduring solution for tough coal preparation applications.
Every Watson-Marlow peristaltic pump is an inherent metering pump with repeatability at 99.5%. Many models include integral digital drives with Profibus or Scada control in Nema 4X wash-down enclosures. These self-priming pumps accommodate flow rates from 0.1 microliter to 350 gpm, and are extremely durable, withstanding pressures up to 232 psi. There are no internal universal joints, valves, dead corners, or glands to impede flow and these pumps are reversible for back flushing lines. They can also run dry indefinitely without damage and provide up to a 30-ft suction lift.