Step 1: The wet sludge with a moisture content of 60%-80% is crushed and extruded into a belt-type sludge drying oven;

Step 2: After heat exchange with the drying circulation air, the wet sludge in the belt-type sludge drying oven is converted into dried sludge with a moisture content of less than 30%, and the hot circulation air has converted to wet&low-temperature circulation air.

Step 3: The wet & low-temperature circulating air is sucked into the heat pump by the circulating fan, and blown into the intermediate heat-exchange facility. After a heat exchange with the evaporated, the temperature becomes lower;

Step 4: The low-temperature circulating air is discharged from the intermediate heat-exchange facility, and the temperature drops down after passing through the desuperheating coil;

Step 5: The wind from the desuperheating coil is evaporated by passes through the evaporator, and the temperature drops below the dew point, so that condensed water is precipitated;

Step 6: After the heat exchange between the intercooler and the heat pump return air, the temperature of the evaporation air was rose and then enters into the condenser;

Step 7: After the circulating air further heated by the condenser, it will converted into heated and dried circulating air and will enters into the sludge drying oven to realize circulating treatment. Generally, the temperature of the drying circulating air is better at 60-70℃, the humidity is better below 20%. After it has being processed by the belt-type drying oven and enters into the heat pump, the temperature of the circulation air becomes low and wet, and it is better at 50-60℃, and the humidity is better above 50%.