Drying
Drying& distillation Prepared by: Engr. Melissa M.
Abansi
Drying DRYING Removal of water from materials containing a
relatively small amount of water using hot surfaces
DRYING (Direct Heating)Solvent Stream, S : leaves as a vapor,
and is solids freeDried Solids, D : leave in the solid phase, and
may contain the solventFeed, F : can be a solid, slurry or
solutionDRYERWet Solids, WDriedSolids, D Solvent, SDrying practices
can have a big impact on grain or seed quality.Drying of grain
involves exposing grain to air with low relative humidity which
will lead to evaporation of the moisture in the grain and then the
moistures removal away from the grain. 4Mechanisms of
DryingMigration of moisture from the interior of an individual
grain to the surface;Evaporation of moisture from the surface of
the surrounding airRate of Drying is Dependent on the
following:Moisture ContentTemperature and temperature of the
GrainRelative HumidityVelocity of the air in contact with the
grain.
Heat is necessary to evaporate moisture from the grain and a
flow of air is needed to carry away the evaporated moisture.The
moisture content falls rapidly at first but as the grain loses
moisture the rate of drying slows.In general the drying rate
decreases with moisture content, increases with increase in air
temperature or decreases with increase in air humidity. At very low
air flows increasing the velocity causes faster drying but at
greater velocities the effect is minimal indicating that moisture
diffusion within the grain is the controlling mechanism.5Mechanisms
of DryingIn general the drying rate decreases with moisture
content, increases with increase in air temperature or decreases
with increase in air humidity. At very low air flows increasing the
velocity causes faster drying but at greater velocities the effect
is minimal indicating that moisture diffusion within the grain is
the controlling mechanismDISTILLATION 7In general the drying rate
decreases with moisture content, increases with increase in air
temperature or decreases with increase in air humidity. At very low
air flows increasing the velocity causes faster drying but at
greater velocities the effect is minimal indicating that moisture
diffusion within the grain is the controlling mechanism
