If run-of-mine coal is difficult to screen, waste coal (gob, culm) is downright nasty. Today, a mixture of coal, silt, clay and soil, typical waste clay is reprocessed from abandoned settling ponds at closed mines. This material may have been sitting in place for 40 years or more, and every truckload of material has slightly different physical characteristics, from gradation and ash content to moisture and calorific value.
The intense action of the bivi-TEC screening deck eliminates blinding by accelerating the coal particles up to 50 Gs. This not only keeps the openings free from pegging, but also helps to break up the clumps of waste coal, liberating the fines and allowing them to fall through the screen openings.
The cost savings of eliminating water from the screening deck cannot be overstated. Coal processors get a bonus when using dry screens, in that the final coal product is sent to a boiler furnace. The lower the moisture level of the coal fuel, the more BTUs can be extracted from the coal. Energy is not wasted burning off water, making for a big spike in boiler efficiency.
According to the manufacturer, Arch Coal in Colorado, Foster Wheeler in Pennsylvania, Sunnyside Cogeneration in Utah and many others use multiple bivi-TEC screens to process high tonnages of coal 24/7.
