Centrifuge tested at coal cleaning plant

A new centrifuge for removing water from ultrafine coal slurry has been successfully tested at the commercial scale at an operating coal cleaning plant.

After coal is mined it is cleaned with water to remove any impurities, after which it is subsequently dewatered.

However, a portion of mined coal particles are smaller than approximately 30-40 microns and these are difficult to dewater after cleaning. As a result, finer coal is often discarded to slurry impoundments. There are hundreds of such sludge impoundments in the US, mostly in Appalachia, creating environmental and safety concerns.

Now professors Roe-Hoan Yoon and Gerald Luttrell from Virginia Tech have developed a hyperbaric centrifuge that can help coal companies to recover all of their mined coal and recover the coal in existing impoundments.

The design was patented by Virginia Tech Intellectual Properties and sublicensed to Decanter Machine for manufacture.

In a pilot-scale test conducted in 2009, coal slurries consisting of ultrafine coal were dewatered to less than 20 per cent moisture. ’The product coal feels like dry powder when you touch it because the water left with the coal is spread so thinly across its large surface area,’ prof Luttrell said.

Encouraged by the results of the pilot-scale test, Walter Energy subsidiary Jim Walter Resources, an Appalachian coal producer, has now successfully tested a full-scale commercial unit.