Direct water removing from frozen brown coal at −20 °C

The liquefied dimethyl ether (DME) was used to dewater the frozen brown coal under a designed experimental condition at −20 °C. With this method, 98.1 wt.% of the initial water was removed from the frozen brown coal. The properties of the brown coal were not changed obviously after the dewatering treatment. By means of differential scanning calorimetry measurement, it is found that the water in tested brown coal existed in both ice and non-freezing forms at the temperature below frozen point indicating that both forms of water can be directly removed by DME at frigid condition.