Rock Products

JUL 2017

Rock Products is the aggregates industry's leading source for market analysis and technology solutions, delivering critical content focusing on aggregates-processing equipment; operational efficiencies; management best practices; comprehensive market

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28 • ROCK products • July 2017 Efficient Fines Management Bennington stressed that many operations stockpile material to be washed, and sometimes those stockpiles simply collect over time. When necessary, that material is hauled over to a separate screen/screw wash plant, meaning that the oper- ation is handling the material multiple times. "This method typically incurs three 'touches' to the material, at a cost of an additional $1.50 per ton to wash the sand," he said. To avoid washing altogether, Bennington said that some operations will employ a common shortcut by trying to dry feed a sand screw. "That method doesn't work very well, particularly in limestone. Ultimately, they find that they can only lower the minus-200 mesh by about 3 percent, which is almost nothing," he said. The new low-water washer, said Bennington is a far more economical and efficient method. Its agitator section is posi- tioned at the front end of the screen where water is added to the dry feed and mixed, producing a thick slurry. The agitator is equipped with a spray bar along the length of the blade mill for thorough cleaning. The slurry is fed to a robust dewatering screen that is outfit- ted with a series of spray bars that help to push the material down through the screen. "Using a sand screw requires 'lifting the silt over the weirs of the screw with much water usage. Alternatively, when the new washer pushes the mate- rial down through the screen, much less water is needed," Bennington said. Conventional wash methods, high water use, and multiple material handling is much like the cliché of "throwing the baby out with the bath water." New low-water washing systems ensure efficient crusher fines management, high- er-quality products and lower operating costs per ton. Carol Wasson is a Fort Wayne, Ind.-based freelancer. WATER WASHING After washing, the operation is achieving under a 6-percent minus-200 mesh. Aerial view of the water-saving equipment.

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