Drying and Solids

  1. Rotary, cylindrical dryers employ superficial air velocities of 5-10 ft/s, sometimes to 35 ft/s when the material is coarse. Residence times are 5-90 min. Holdup of solids is 7-8%. An 85% free cross section is taken for design purposes. In countercurrent flow, the exit gas is 10-20ƒC above the solid temperature; in parallel flow, the temperature of exit solids is 100ƒC. Rotation speeds of about 4 rpm are used, but the product of speed (rpm) and diameter (ft) is typically between 15 and 25.

  2. Drying times range from a few seconds in spray dryers, to one hour or less in rotary dryers, and up to several hours (or even days) in tunnel shelf or belt units.

  3. Continuous tray or belt dryers for granular materials of natural size or pelleted to 3-15 mm have 10-200 min drying times.

Drying and SolidsConveyors for Particular SolidsCooling TowersCompressors and Vacuum PumpsCrushing and Grinding
Extraction, Liquid-LiquidCrystallatisation from SolutionFiltrationHeat ExchangersMixing and Agitation
Particle Size EnlargementpipingPumpsReactorsRefrigeration
Size Seperation of ParticlesUtilities, Common SpecificationsVessels (Storage Tanks)

The information is arranged by commonly recognised categories. In some instances, definitions and general statements have been included for clarity.