Evaluation of Pilot Scale Drying of Brown Coal in a Keith Rotary Superheated Steam Dryer
Relative to conventional air drying techniques, superheated steam drying provides a number of advantages, including increased efficiency, reduced fire or explosion risks, faster drying rates and no particulate or odorous emissions. Consequently, superheated steam drying is currently receiving increased focus for drying in a range of industries.
The potential of using superheated steam to dry Victorian brown coals, which have moisture contents of 50-70% wet basis, has been known for several decades and a significant amount of research has been completed. However, the majority of research has focused on fluidised bed systems. In the current paper, the superheated steam drying of brown coal using a rotary dryer technology developed by Keith Engineering of Australia is investigated.
The results of a full factorial experimental design for four system parameters (namely steam temperature, coal feed rate, steam velocity and drum rotational rate) tested at two processing levels are presented. Through a statistical analysis of the experimental results, the significance of each system parameter on the final moisture content is investigated. In addition, the interaction between the system parameters is examined. From the results of the statistical analysis and the results of selected additional experiments, it is demonstrated that a desired moisture content can be achieved by careful selection of the processing conditions. Importantly, it is shown that the Keith dryer can reduce the moisture contents of Victorian brown coals by as much as ninety per cent.