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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26 • ROCKproducts • July 2017 WATER WASHING D epleted natural sand reserves, environmental constraints and decade-long permitting processes are just a few of the drivers behind a fast-growing demand for manufactured sand – and a significant need for effi- cient crusher fines management. To meet product specifications, opera- tors are typically turning to costly air classifiers or high-water-use washing with cyclones or sand screws. While the latter options may work well for some operations, others are seeking alterna- tive, affordable solutions especially if they operate dry crushing facilities, or portable plants; or if they are limited by their footprint or available water resources. At issue is the amount of water required for conventional washing methods; and a welcomed access to a new, econom- ical low-water washing solution. "A sand screw needs 50-gal.-per-minute of water for every ton of minus-200 mesh in the feed," said John Benning- ton, director of washing and classifying equipment for Superior Industries. "Even if an operation is only running at 100 tph, and their minus-200 mesh is at 15 percent – that is 15 tons of fines requiring 750-gal.-per-minute of water to adequately lift the silt over the weirs of the screw. That's a lot of water for most crushing operations," he said. As an industry veteran in washing and classifying, Bennington had been brain- storming a low-water washing solution for many years, and "with the resources of Superior Industries, we were able to design it, refine it, and prove it in the field," he said, referring to the new Alli- ance Low Water Washer. Low-Water Washing A New Economical Solution to Efficient Crusher Fines Management. By Carol Wasson Bennington explained that the unit combines a specially designed agita- tor and a dewatering screen within one machine. It allows the operation to wash crusher dust right next to the crushing circuit, eliminating the cost of handling and hauling the fines to a separate washing circuit. Notably, he said that the system accepts a dry feed directly from the crushing circuit and processes the material into a higher-value manufactured sand, while requiring up to 80 percent less water consumption. Field-Proven Operation Reno, Nev.-based Rilite Aggregate was facing a water management challenge. The company had been washing its con- crete sand with a 54-in. twin screw that required 2,200 gal.-per-minute. "We had to fill a holding pond and utilize a large pump. With that, we could wash material for only three hours per day," said Michael Rudolf, a long-term crush- ing subcontractor who has worked with Rilite for nearly 20 years. He added that the facility must use an additional 60,000 gal.-per-day to fill the water trucks used to wet the quarry roads for airborne dust control. The water-management situation reached a "crisis-mode" when a specification change in utility bedding sand required the company to wash that product as well, lowering the minus-200 mesh from 15 percent to 7 percent or less. Rudolf said that they needed an aggres- sive washing system that could run off available water. "With a drastic change Superior's Alliance Low Water Washer.

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