The sand water mixture enters the cleaning box; Separate with an impeller separator; Then enter the lower dehydration screen for dehydration treatment; The wastewater (containing a large amount of impurities such as fine sand, mud, dust, etc.) from the cleaning box is transported to the separator by the slurry pump, and then the fine sand after centrifugal classification and concentration is discharged into the upper layer of the dewatering screen through the settling nozzle; The wastewater, mud, dust, impurities, etc. inside the cleaning box are discharged into the high-level return water tank after passing through the overflow port of the separator; Upper layer produces coarse sand as finished material; Fine sand or a mixture of coarse and fine materials is discharged from the lower layer of finished products (can be adjusted according to customer requirements)