Wet material is continuously fed into the first drying tray at the top of the dryer via a feeder. Rotating agitator arms equipped with rake blades contisly turn and agitate the material. The material traverses the surface of the drying tray along an exponential spiral path; material on the small tray is conveyed to the outer edge and fato the outer edge of the large tray below, while on the large tray, the material moves inward and falls through the central discharge opening into the next lower small tray. Large andll trays are arranged alternately, allowing the material to flow continuously through the entire dryer. The hollow drying trays are supplied with heating media, which can be saturated steam, hot water thermal oil; the heating medium enters at one end of the tray and exits at the other end.