A method is disclosed for drying and passivating wet coals, for example bituminous, subbituminous or lignite. The wet coal is introduced into a heating zone at a controlled rate, then is contacted with a heavy hydrocarbonaceous treatment material having a softening point of at least 60.degree. C. The particles and treatment material are simultaneously intimately mixed and are heated to a temperature of at least 200.degree. C. but below the coal decomposition temperature while being moved along the heating zone in a plug flow manner. The particles are then cooled in a cooling zone.