1. MOISTURE
DISPERSION |
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4. PARTICLE
STRUCTURE |
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| This is defined
as the accessibility of the moist surface to the
drying medium (Hot air or gas). This is achieved
in a flash dryer by use of a product disperser
such as mechanical scatterer, double paddle feeder
or cage mill etc. by mixing dried product in the
feed. |
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Materials having
capillaries will be able to evolve moisture to
the surface from internal areas more rapidly resulting
in swift drying action. Dense particles which
have no voids are difficult to dry in a flash
drying system. |
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2. TEMPERATURE
DIFFERENTIAL |
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5. PARTICLE
SIZE |
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In flash drying it is possible
to use high initial temperatures. These are
possible due to short contact time with the
result that the product temperature never
exceeds the wet bulb temperature of the gas
unless all surface moisture is removed.
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Drying is accomplished
by evaporation from the surface of the particle.
Therefore to remove the internal moisture, it
is necessary that the moisture reaches the surface
by diffusion. This transfer will obviously take
place most rapidly with smaller particles. |
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3. AGITATION |
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In Flash Dryer, agitation
or turbulence is accomplished by the use of
high gas velocities. The vapour film is continuously
swept away from moist particles. As a result,
moisture removal is practically instantaneous.
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