FLASHDRYERS can be the most economical choice for drying solids that have been dewatered or naturally have a low moisture content.
Also known as “pneumatic dryer”, they are the simpliest gas suspension dryers with the smallest footprint. A single operation combines the necessary mixing, and heat and mass transfer fro drying a solid. Residence time is short producing almost immediate surface drying. These dryers are useful for moist, powdery, granular and crystallized materials, including wet solids discharged from centrifuges, rotary filters and filter presses.
Particle size must be quite small, generally less than 500 μm and the best feed is friable and not sticky. FLASHDRYERS are relatively simple and take up less space besides, because of the extremely short residence time, these devices are well-suited for processing heat sensitive materials. Process temperatures are controlled in a very simple way. The inlet gas temperature is kept constant and the outlet temperature controls the wet feed rate.
The heart of the system is the mill where the drying takes place. Here the material to be dried and the hot gas meet while the material is crushed and brought to a size which facilitate the drying process itself. A duct system connect the mill exit with the dedusting system usually composed of a cyclone and a bag filter. The first separation between the dried material and the exhaust gas takes place in the cyclone separator (when foreseen) and completed in the bag filter.
FLASH DRYING systems are designed based on feed and product characteristics, the available permissible heating source and safety requirements. Critical data include drying temperature, feed moisture content and product desired residual moisture content. FLASHDRYER is suitable for drying a wide range of products as, for instance, inorganic chemicals such ad sodium bicarbonate, gypsum, alumina and titanium dioxide and organic products ranging from native starch to sludges from wastewaters treatment.
