Cyclone dryer: A pneumatic dryer with increased solid residence time

Pneumatic dryers, in which the moist solid is carried and transported by th e drying air while being dried, are very cost-efficient dryers where short- time drying is sufficient. Their basic and most widely used form is the fla sh dryer. Most drying tasks requiring a longer drying time, however, could so far not be solved by pneumatic dryers. Long-time dryers like fluidized b ed dryers or rotary drum dryers had to be used. In this paper, the cyclone dryer, a pneumatic dryer with significantly increased solid residence time, is described. Combined with a flash dryer as pre-dryer, it offers a straig htforward and cost-efficient solution for many drying problems otherwise so lved using fluidized bed or rotary drum dryers. The paper gives a brief des cription of design and working principles of the cyclone dryer and recalls the basic principles of parallel flow pneumatic drying. The dimensioning of flash dryer - cyclone dryer units for changing products in day-to-day prac tice is largely experimental due to the different and hardly predictable dr ying characteristics of the solids. A choice of products successfully dried on flash dryer cyclone dryer units is presented.