DRYING OF BROWN COAL USING A SUPERHEATED STEAM ROTARY DRYER

Vast reserves of brown coal exist in Australia. However, the high moisture contents of these brown coals pose challenges for existing and potential users. An obvious solution is to remove the moisture by drying. A drying technique that is currently receiving increased focus is superheated steam drying which, relative to conventional air drying techniques, provides a number of significant advantages including increased efficiency, reduced fire or explosion risks, faster drying rates and no particulate or odorous emissions. In the current paper, the drying of brown coal in a pilot scale superheated steam rotary dryer developed by Keith Engineering is investigated. It is illustrated that the dryer is able to significantly reduce the moisture content of Australian brown coals, with moisture reductions of up to ninety per cent achievable. Through a statistically designed series of tests, the parameters affecting the drying performance are investigated. It is demonstrated that the final moisture content is particularly dependent on the steam temperature and coal feed rate while the drum rotational rate has a less significant effect.