A new technology for removing water from ultrafine coal slurry has been successfully tested at the commercial scale at an operating coal cleaning plant. The technology offers the possibility of reducing the coal slurry impoundment problem from the source. A peer-reviewed paper on this new technology was presented Sept. 15 at the 13th Australian Coal Preparation Society Conference, Cairns, Queensland.
Cleaning coal after it has been mined is done with water. The bulk of the coal mined is relatively coarse in size and, therefore, can be readily washed of impurities and subsequently dewatered. However, a portion of mined coal is smaller than approximately 30-40 microns something like the size of talcum powder and is difficult to dewater after cleaning, said Roe-Hoan Yoon, the Nicholas T. Camicia Professor of Mining and Mineral Engineering in Virginia Tech's College of Engineering. As a result, finer coal is often discarded to slurry impoundments. There are hundreds of sludge impoundments in the U.S., mostly in Appalachia, creating environmental and safety concerns, said Yoon.
Yoon presented the paper in Australia with co-author Wally Schultz, executive vice president of Decanter Machine Inc. of Johnson City, Tenn., the largest supplier of screen-bowl centrifuges internationally.
Yoon, Gerald Luttrell, Massey Professor of Mining and Mineral Engineering, and their colleagues at the Center for Advanced Separation Technologies (CAST) at Virginia Tech have developed a hyperbaric centrifuge that was patented by Virginia Tech Intellectual Properties Inc. and sublicensed to Decanter Machine. "The new technology compliments what Decanter already has," said Yoon.
Encouraged by the results of a pilot-scale test conducted in 2009, Jim Walter Resources Inc. of Brookwood, Ala. (Walter Energy) tested a full-scale commercial unit successfully. "Everything has performed as promised by Decanter," said Joel Franklin, preparation engineer for J
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