In the field of sand washing, major developments are few and far between. Some types of equipment actively used today were developed over a century ago, and many items are 50 years old. There are improvements over time, of course, in quality, tolerances, efficiencies, motors, bearings, wear parts, and so on. However, there are few transformative leaps in the actual washing process.
However, we may now be approaching a paradigm shift in the processing of crusher fines or dust – thanks to results produced by the Superior Industries Alliance low water washer at a basalt operation in southern New South Wales.
Crusher dust has been washed for decades with cyclones and sand screws. Both techniques have been fine-tuned to carry out this process, and with sufficient power and sufficient water, each application can achieve an outcome. The Alliance low water washer, using minimal water and limited power, conditions or “wets” the crusher fines with agitation, then builds a deep bed of material on the deck of a dewatering screen. The dewatering screen has spray bars to inject water into the product bed, releasing finer size particles through the apertures of the deck.
In the December issue of Quarry, Superior Industries covers the development and technical aspects of the Alliance low water washer.
The Alliance low water washer made its international debut at Bauma earlier this year. At almost the same time, the first unit arrived in Australia. It was delivered and installed at a basalt operation, south of Sydney, virtually going straight to work.
The quarry has previously washed crusher fines with a sand screw and used an air separator. Its owners were interested in controlling their particle separation and using as little water as possible.
Once the Alliance low water washer was commissioned and operational, the quarry operators fine-tuned it to their satisfaction. At this site, there are typical averages of 17 per cent passing 75 microns (μm) in the crusher fines material (the minus 5mm material). The aim was to achieve an average of nine per cent -75μm.
The operation has now been producing manufactured sand at its preferred grading for more than six months. The operators have complete control and can readily adjust any changes in the feed. They have been able to get the product stockpile down to six per cent moisture.
Different crushers and different rock types produce a range of gradings, particularly in the -75μm percentages. The initial challenges in manufactured sand were focused on removing excess -75μm material.
The industry has reached a stage where individual sites are attempting to make their manufactured sand suit individual batch plants, as well as the broader market. Achieving five per cent -75μm is possible with certain rock types and feed gradings.
All of this is carried out with similar power usage to a sand screw, and less than a third of the power used to pump to a cyclone, with a fraction of the amount of water used in either of those processes.
Superior Industries continues to develop a broad range of experience in rock types, as the use of the Alliance low water washer continues to grow. Locally, discussions have been held with a number of other producers with differing issues, gradings and rock types. The evolution of producing manufactured sand appears to have reached a paradigm shift.
Jim Hankins is the principal of Rivergum Industries, based in Endagine, NSW.
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