Flash Dryers

Flash drying systems is in which particulate solids are dried during transport in a hot gas stream usually air or combustion gases. The simple flash drying system includes six basic components: the gas heater, the wet material feeder, the drying duct, the separator, exhaust fan, and a dried product collector. The wet particles are fed into the hot gas stream sometimes with special mixing devices. The stream flows up the drying tube. The gas velocity must be greater than the free fall velocity of the largest particle to be dried. The gas velocity in relation to the particle velocity is high. Thermal contact between the conveying air and the solids as mentioned above is usually very short and therefore flash dryers are most suitable for removal of external moisture (surface moisture) and are less suitable for removal of internal moisture. At the end of the drying process a dust separation arrangement is installed. It must comply with the regulations for pollution control. For this purpose cyclone dust separators, fabric filters, electrostatic precipitators, wet scrubbers, and fabric filters are used. Flash dryers are used in various Sectors of the chemical, pharmaceutical, ceramic, gypsum, wood, and mining industries. Flash dryers are simple in construction and have low capital cost and they are almost trouble free.