Predicting the steam drying behavior of brown coals and lignites

For some selections of samples, drying time will be proportional to total moisture, and for others, there will be exceptions. One key aspect is whether or not the target moisture level requires removal of any monolayer moisture at all. Coals with abundant bulk and multilayer moisture can achieve targets on residual moisture by vaporizing only a portion of the multilayer moisture. Consequently, their drying times will be relatively modest. But coals with little bulk moisture and relatively abundant monolayer moisture will require relatively long drying times simply because monolayer moisture is always released much more slowly than multilayer moisture. Hence, the levels of the three forms of moisture in any particular coal sample are determining factors for drying times.