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DRYINGDr. Basavaraj K. Nanjwade M. Pharm., Ph. D
Department of Pharmaceuticsacu!t" of Pharmac"
#mer $!%Mu&htar 'niversit"
(o)ru&, *i)"a.
+%mai! nanjwade)&-mai!.com
2014/03/11 1Faculty of Pharmacy, Omer Al-MukhtarUniverity, !o"ruk, #i"ya$
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/#N(+N(0
• Definition of drying
• Importance of drying
• Difference between drying and evaporation• Equipments
• References
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Dr"in
• Drying is commonly the last stage in a manufacture process.
• Drying is the final removal of water from material(usually by heat)
• Non%therma! dr"in
1% As quee!ing wetted sponge 2% Adsorption by desiccant (desiccation)
3% E"traction.
2014/03/11 3Faculty of Pharmacy, Omer Al-MukhtarUniverity, !o"ruk, #i"ya$
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Importance of dr"in
• In pharmaceutical technology# drying is carried out for one
or more of the following reasons$
1. %o avoid or eliminate moisture which may lead tocorrosion and decrease the product or drug stability.
2. %o improve or &eep the good properties of a material# e.g.'lowability, compressibility.
3. %o reduce the cost of transportation of large volume
materials ( liquids).4. %o ma&e the material easy or more suitable for handling.
5. reservative.
6. %he final step in Evaporation# 'iltration# rystalli!ation.
2014/03/11 4Faculty of Pharmacy, Omer Al-MukhtarUniverity, !o"ruk, #i"ya$
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Difference )etween dr"in
and evaporation0!. No.
Drying Evaporation*. In dr"in processes# the main operation
usually carried out on so!id materia!s, e.g. powders# or products
In evaporation processes# the mainoperation usually carried out on!i7uid materia!s, e.g. solution# or products
+. Dr"in in most of the cases means theremoval of relatively sma!! amounts ofwater from so!ids
+vaporation include theremova! of !are amounts of
water from solutions.
,. In most cases# dr"in involves the
remova! of water at temperatures
)e!ow its boiling point
-hereas evaporation means theremova! of water )" )oi!in a
solution.
. In dr"in , water is usually removed by circu!atin air over the materia! inorder to carr" awa" the water vapour
-hile in evaporation # water isremoved from the material aspure water vapour mi"ed withother ases.
2014/03/11 %Faculty of Pharmacy, Omer Al-MukhtarUniverity, !o"ruk, #i"ya$
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+7uipments
*. Drum dryer ('ilm drying)
+. pray dryer
,. 'ree!e Dryer . %ray drier
/. 'luidi!ed 0ed Dryer
1. 2acuum Dryer
2014/03/11 Faculty of Pharmacy, Omer Al-MukhtarUniverity, !o"ruk, #i"ya$
&
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Drum Dr"er 8i!m Dr"in9
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Drum Dr"er 8i!m Dr"in9
• It consists of a drum of about 3.4/5*./ m in diameter and+5 m in length# heated internally# usually by steam and
rotated on its longitudinal a"is.
• #peration %he liquid is applied to the surface and
spread to a film# this may be done in various ways# but
the simplest method is that shown in the diagram# where
the drum dips into a feed pan. Drying rate is controlled by using a suitable speed of rotation and the drum
temperature. %he product is scraped from the surface of
the drum by means of a doctor &nife.
2014/03/11 (Faculty of Pharmacy, Omer Al-MukhtarUniverity, !o"ruk, #i"ya$
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0pra" Dr"er
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0pra" Dr"er
• %he spray dryer provides a large surface area for heatand mass transfer by atomi!ing the liquid to small
droplets.
• %hese are sprayed into a stream of hot air# so that
each droplet dries to a solid particle.
• %he drying chamber resembles the cyclone ensuring
good circulation of air# to facilitate heat and mass
transfer# and that dried particles are separated by thecentrifugal action.
• pray dryer can be operated efficiently at variousfeed rates.
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ree:e Dr"er
2014/03/11 11Faculty of Pharmacy, Omer Al-MukhtarUniverity, !o"ruk, #i"ya$
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ree:e Dr"er
• 'ree!e drying is a process used to dry e"tremely heat5sensitive materials. It allows the drying # withoute"cessive damage# of proteins# blood products andeven microorganisms# which retain a small but
significant viability.
• In this process the initial liquid solution or suspensionis fro!en# the pressure above the fro!en state isreduced and the water removed by sublimation.
• %hus a liquid5to5vapour transition ta&es place# but herethree states of matter involved$ liquid to solid# thensolid to vapour.
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(ra" drier
2014/03/11 13Faculty of Pharmacy, Omer Al-MukhtarUniverity, !o"ruk, #i"ya$
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(ra" drier
• Air flows in direction of the arrows over each
shelf in turn.
• %he wet material is spread on shallow trays
resting on the shelves.
• Electrical elements or steam5heated pipes are
positioned as shown# so that the air is
periodically reheated after it has cooled by
passage over the wet material on one shelf
before it passes on the ne"t.2014/03/11 14Faculty of Pharmacy, Omer Al-Mukhtar
Univerity, !o"ruk, #i"ya$
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!uidi:ed Bed Dr"er
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!uidi:ed Bed Dr"er
• 6'luidi!ed7 means something that behaves li&e liquid.In the fluidi!ed bed dryer# the mi"ture of solids and
gas behave li&e a liquid and solid are called fluidi!ed.
• It provides good contact between hot air and particlesto obtain efficient drying.
• %he hot air is passed through a mesh# which supports
the conical vessel with a porous base.
• %his vessel is filled with powder to be dried.
• It has wheels and can be clipped to the central plate
by means of a rapid acting ring closure.
2014/03/11 1&Faculty of Pharmacy, Omer Al-MukhtarUniverity, !o"ruk, #i"ya$
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;acuum Dr"er
2014/03/11 1'Faculty of Pharmacy, Omer Al-MukhtarUniverity, !o"ruk, #i"ya$
Steam orWater Jacket
Condenser
Connection to
Vaccum Pump
Condensate
Receiver
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;acuum Dr"er
• %his equipment is a good e"ample of conduction
drier. %he vacuum oven consists of a 8ac&eted vessel
to withstand vacuum within the oven.
• %here are supports for the shelves giving a larger areafor conduction heat transfer. %he oven can be closed
by a door.
• %he oven is connected through a condenser and liquid
receiver to a vacuum pump.
• 9perating pressure can be as low as 3.3,53.3, bar# at
which pressures water boils at +/5,/ 3.
2014/03/11 1(Faculty of Pharmacy, Omer Al-MukhtarUniverity, !o"ruk, #i"ya$
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2014/03/11 1)Faculty of Pharmacy, Omer Al-MukhtarUniverity, !o"ruk, #i"ya$
(<$NK Y#'+%mai! nanjwade)&-mai!.com
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