The disc dryer, also known as the tray dryer, operates on the following principle: the top layer of the dryer consists of small heating trays, the second layer comprises large heating trays, and then small and large trays alternate downward in sequence. During operation, the central main shaft, driven by a motor, rotates along with the raking arms and raking blades fixed to it.

The material to be dried is fed from the top of the dryer, first landing on the small trays. Under the continuous stirring and pushing of the raking blades, it moves in an exponential spiral from the inner edge to the outer edge of the heating tray, continuously falling from the outer edge of the small tray to the next layer of large trays. Pushed by the reverse raking blades, it then moves in an exponential spiral from the outer edge to the inner edge of the tray, continuously dropping from the inner edge of the large tray to the next layer of small trays. Alternating in this manner from inner to outer edges, the material moves downward layer by layer. Simultaneously, heat is transferred from the heating medium through the tray surface to the material, which is heated and dried, and finally discharged from the bottom outlet. The vaporized moisture is naturally expelled from the top outlet of the dryer or removed by an exhaust fan.