(1) The wet sludge with a moisture content of 60%-80% is crushed and extruded into a belt-type sludge drying box;

(2) The wet sludge in the belt-type sludge drying box becomes dry sludge with a moisture content of less than 30% after heat and mass exchange with the hot drying circulating air, and the hot drying circulating air becomes a wet low-temperature circulation Air;

(3) The wet low-temperature circulating air is sucked into the heat pump by the circulating fan, and is blown into the intermediate heat exchanger from the circulating fan to exchange heat with the evaporating air to further reduce the temperature.

(4) The low-temperature circulating air after cooling is discharged from the heat exchanger in the middle, and then the temperature is reduced by the water-cooled pre-cooling coil;

(5) The air from the water-cooled pre-cooling coil is evaporated through the evaporator, and the temperature is below the dew point, so that the condensed water is precipitated;

(6) The evaporative outlet air passes through the intercooler and exchanges heat with the return air of the heat pump, and then enters the condenser after raising the outlet air temperature;

(7) The circulating air is further heated up by the condenser, and the circulating air that becomes hot enters the belt-type sludge drying oven to realize the circulating treatment. The temperature as described hot drying circulating air is 60 ℃-70 ℃, and the humidity is below 20%, and the warm circulating air temperature entering the heat pump after being processed by the belt sludge drying box is 50 ℃-60 °, Humidity is above 50%.