Mineral Processing Equipments: Dryers

Dryers remove water or other volatile material from solid substances primarily by introducing hot gases into a drying chamber. The hot air readily absorbs moisture from the material.

Rotary dryers, flash dryers, spray dryers, and tray and compartment dryers are a few of the many types of dryers. However, in minerals processing operations, rotary dryers are the most commonly used.

Rotary dryers consist of a horizontally inclined rotating cylinder. Material is fed at one end and discharged at the other end. In direct-type rotary dryers, hot gases move through the cylinder in direct contact with the material, either with or against the direction of its flow. The cylinder is equipped with flights, which lift the material and shower it down through the hot gas stream. This type of dryer has a potential for high levels of dust emission. In an indirect-type rotary dryer, heat is applied by combustion gases on the outside of the cylinder or through steam tubes inside the cylinder. This type of dryer has much less tendency to emit dust. It is usually used when continuous drying of powdery or fine material is needed.

Article Sources:
http://www.osha.gov/SLTC/silicacrystalline/dust/chapter_2.html