Brown coal drying processes-a review

Brown coals become increasingly important in energy consumption with the deposits of other energy resources decreasing every year. The direct utilization of moist brown coals without drying brings many problems such as low combustion efficiency, high greenhouse gas emissions, and it is not acceptable for coal gasification or liquefaction. Pre-drying brown coal is necessary and meaningful. Various drying processes, mainly classified into evaporative and non-evaporative drying, are summarized in this paper, introducing the principles and analyzing the advantages and disadvantages.