Flash dryers are also known as pneumatic dryers. Flash dryers are used for drying free flowing powders or cakes containing moisture. A typical flash dryer consists of a long tube or duct called the flash duct, which is used to convey the product along with the hot air. The product gets dried as it travels in this flash duct and is then separated in cyclone or bag filter. The feeding system consists of a hopper having a screw conveyor at the bottom. Flash dryers are suitable for heat sensitive products. Even the heat sensitive products can be dried at high inlet air temperatures due to very low residence time of the product in the flash duct. The air can be directly or indirectly heated using steam, thermic fluid, oil, gas or solid fuel and is handled by centrifugal fans.
Cage mill flash dryers operate on the same basis as that of the agitated flash dryers. The difference is that the cage mill flash dryers consist of vertical pin mill type agitators in which the wet product is fed.