Drying method for processing material and horizontal rotary dryer

Abstract

To provide a drying method for processing material and a horizontal rotary dryer allowing easy performance of mass processing of the processing material and enabling size reduction by improving drying performance of the dryer. In a drying method for processing material in which a horizontal rotary dryer provided with: a rotating shell having a feed port for processing material on one end side thereof and a discharge port for processing material on the other end side thereof, and capable of freely rotating around an axial center; and a group of heating tubes through which a heating medium passes, provided within the rotating shell, and configured in a manner that the processing material is lifted up in a rotational direction by the group of heating tubes in accordance with the rotation of the rotating shell, is used, and the processing material is dried, through indirect heating, by using the group of heating tubes in a process of feeding the processing material to the one end side of the rotating shell and discharging the processing material from the other end side of the rotating shell, the rotating shell is rotated to make a critical speed ratio α defined by the following expression 1 and expression 2 become 30 to less than 100% to dry the processing material,=2.211/2  Expression 1α=·100  Expression 2 wherein Vc indicates a critical speed (m/s), D indicates an inside diameter (m) of the rotating shell, α indicates the critical speed ratio (%), and V indicates a rotation speed (m/s).