By : Afaf Hithnawi Dr: Mohammad Sabbah Spray drying 1
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Out line Definition. Main terms of spray drying. Stages of
spray drying. Atomizer type. Advantages,disadvantages. 2
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Definition : Physical separation process for solid particles
from solution, suspended particles, slurries, and pasts by using
sources of heat (thermal energy), to form powders (solid products).
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Main terms of spray drying : 1-Solution with can be pumped
(flow). 2-Non sintering solid particles. 3- High temperature demand
( source of energy). 4-product with high solubility,
hygroscopicity. 4
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Stages of conventional spray drying: 1-Heating of hot drying
medium. 2-Atomization of feed into droplet. 3-Spray-air contact and
drying droplet. 4-Product recovery and air treatment.. 5
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Atomizer types: 1-Centrefugal atomizers(Rotary): droplet size
range with (1-600) micron can be produced. -_Rotary atomization
based on centrifugal energy,. rotating wheel and speed of rotation
_And these variables are selected according to the liquid product
and. required dried properties 6
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2-Pressure nozzle A device designed to control the direction or
characteristics of a fluid flow (especially to increase velocity)
as it exits (or Droplet size 10-600micron))enters) an enclosed
chamber or pipe. Advantages : _ simple and cheap. _No moving part.
_Low energy consumption. Limitations : _Low capacity (feed rat for
nozzle) _high tendency to clots. 7
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3-Two fluid nozzles(Pneumatic) _ Droplet size( 6-600 micron).
_Produce a spray by using a second fluid,such as compressed air or
steam, to atomize the feed. advantages : -no moving part -produce
product with very small size. Limitation : -high energy
consumption. -high tendency to erosion. 8
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Air direction compared with feed direction 10
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Advantages of spray drying 1-continuos and easy to control
process. 2-rapid and non-contact draying. 3- The droplets are small
4-Applicable to toxic and explosive materials. 5-Good properties
for the spray-dried powder so it can be easily compressed into the
form of tablets. 6-labor cost is low since the materials is dried
in single operation without handling. 11
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Disadvantages of spry draying 1- solid materials cannot be
dried. 2- the equipment is very costly and bulky. 3- there is a lot
of heat wasted 4-heat degradation possibility in high -temperature
spray drying. 12
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http://www.arunmujumdar.com/file/Publications
/books/Spray%20Drying%20Technology.pdf Thank you ^_^ 13