Closed cabinet structure makes less heat dissipation and less odor emission. Accurate humidity control technology avoids high energy consumption in later stage of drying. It is a combination of sludge hopper and dehumidification heat pump. Dehumidification heat pump heat up and dehumidify the air, while the sludge is placed into a hopper. The hot air is blow up from the bottom and recycle at the heat pump. The electricity power consumption is 0.4~0.5kw.h/kg.H2O.