The classifier, cyclone separator, dust collector, and induced draft fan form a classification system. Under the suction force of the fan, the material moves at high speed from the lower inlet of the classifier to the classification zone along with the rising airflow. Under the strong centrifugal force generated by the high-speed rotating classification turbine, the coarse and fine materials are separated. The fine particles that meet the particle size requirements enter the cyclone separator or dust collector through the gap between the classification wheel blades. The coarse particles carry some of the fine particles and their velocity disappears after hitting the wall. They descend along the cylinder wall to the secondary air outlet and are separated by the strong washing effect of the secondary air. The fine particles rise to the secondary classification zone for secondary classification, and the coarse particles descend to the discharge port for discharge.