The document discusses various types of drying equipment used to remove moisture from foods and other materials. It describes common industrial dryers like spray dryers, tray dryers, fluidized bed dryers, drum dryers, vacuum dryers, and freeze dryers. For each type of dryer it provides details on how it works, advantages, disadvantages, and applications. The overall document provides an overview of key industrial drying methods and factors to consider when selecting appropriate drying equipment.

1. •Mamta Sahurkar
DRYING EQUIPMENTS

2. DRYING
AND
DRYING
EQUIPME
NTS

3. DRYING/DEHYDRATI
ON
 Drying is the simple
process of dehydrating
foods until there is not
enough moisture to
support microbial
activity.
 If adequately dried and
properly stored,
dehydrated foods are
shelf stable (safe for
storage at room
temperature).

4. PURPOSE OF DRYING
• Increase in shelf life/Preservation.
• Reduction in transportation cost.
• Easy material handling.
• Improve or maintain properties
(flow ability or compressibility)

5. • Dryer is a device that removes moisture by
heating the mass to a level where it becomes safe
to store.
• Batch dryers are used for solid throughout (flows)
below 50 kg/hr. Continuous dryers is preferred
above 1000 kg/hr.
DRYER
MOISTUR
E
HEAT
FEED
DRIED
PRODUCT
DRYING EQUIPMENTS

6. SELECTION OF EQUIPMENT
DEPENDS ON
GENERAL CONSIDERATION
 Physical/Chemical properties of
materials
 Production capacity
 Initial and final moisture content
required
 Particle size distribution
 Temperature and drying
characteristics
 Explosion and toxicological
characteristics
 Dryer must operate reliably, safely and
economically.
 Operating and maintenance must not be
excessive
 Pollution must be controlled
 Energy consumption must be minimized

7. INDUSTRIAL
DRYERS

8. CLASSIFICATION OF
DRYERS

9. INDUSTRIAL
DRYERS
SPRAY DRYER
TRAY DRYER
FLUIDIZED BED
DRYER
FLASH DRYER
DRUM DRYER
VACUUM DRYER
TUNNEL DRYER
ROTARY DRYER
FREEZE DRYER

10. SPRAY DRYER
• The spray dryer provides a large
surface area for heat and mass
transfer by atomizing the liquid to
small droplets. These are sprayed
into a stream of hot air, so that each
droplet dries to a solid particle.
• The drying chamber resembles the
cyclone ensuring good circulation of
air, to facilitate heat and mass
transfer, and that dried particles are
separated by the centrifugal action

11. • Product quality effectively
controlled
• Product properties effectively
controlled
• Suitable for heat sensitive foods
eg: milk
• High tonnage equipment
• Corrosion problem minimized
• Good efficiency
ADVANTAGE
S
• Product quality effectively
controlled
• Product properties effectively
controlled
• Suitable for heat sensitive foods
eg: milk
• High tonnage equipment
• Corrosion problem minimized
• Good efficiency
DISADVANTAGES
APPLICATIO
NS
• Drying of any substance in solution or in
suspension form
• It is most useful for drying thermolabile
materials eg: antibiotics
• Suitable for large quantities solution
• Suitable for both soluble and insoluble
substances
• It can produce spherical particles in the
respiratory range
• Drying of milk, soap and detergents

12. TRAY DRYER
• These types of dryers use trays or
similar product holders to expose
the product to heated air in an
enclosed space.
• The trays holding the product inside
a cabinet or similar enclosure are
exposed to heated air so that
dehydration will proceed.
• Air movement over the product
surface is at relatively high velocities
to ensure that heat and mass
transfer will proceed in an efficient
manner.
• Operated as batch systems

13. • Simple in
handling
• Lesser capital
cost
ADVANTAGES
• Non-uniform drying of a product at
different locations within the system
• Time required for drying is more
• The major disadvantages of this type
of dryers are the high labor cost
involved during loading and
unloading of the drying materials and
the low capacities of the units
DISADVANTAGES
• Mainly used for drying agricultural produce
• Drying foods Eg:( chillies and spices etc)
• Of potential use in
pharmaceuticals,paints,textile and other
industries
APPLICATIONS

14. FLUIDIZED BED
DRYER
• Fluid bed drying is most widely used
technique for drying pharmaceutical
powders and granulation
• The direct contact between particles
and air/gas is possible in fluid bed
systems.
• Here any type of inert gas or air is
used.
• They can be designed in either batch
or continuous type fluid bed dryer.
• In fluidized bed dryer, hot air is
passed at high pressure through a
perforated bottom of the container
containing granules to be dried.
• The granules are lifted from the

15. • The hot gas surrounding every granule to completely dry
them.
• The material or granule are uniformly dried.
• The hot air/gas used for drying can be generated by
either steam coils or a combustion furnace.
• The angle of repose of gas-solid mixture is zero and it
assumes the shape of vessel that contains it.
• Uniform conditions of temperature, composition and
particle size distribution is achieved throughout the bed
because of complete mixing between the solids and gas
is obtained.

16. • Fluidized bed dryer requires less time
to complete drying ie: 20 to 40 min.
• Hot spots are observed in the dryer,
because of its excellent mixing and
drying capacities.
• The thermal efficiency is 2 to 6 times
greater than tray dryer
• It facilitates the drying of
thermolabile substances, since
contact time for drying is short.
• It can be used as batch type or
continuous type.
• The free movement of individual
particles eliminates the risk of
soluble material migrating as may
occur in static bed
• Equipment is bulky.
• Expensive
ADVANTAGES DISADVANTAGES
APPLICATIONS

17. • Flash dryer utilizes superheated
steam as the drying medium have
some unique quality and energy
advantages over air drying systems.
• Flash dryers consisting of inert media
have been employed at pilot scales to
dry slurries and suspensions sprayed
onto them.
• The particles are coated thinly by the
slurry and dried rapidly as a thin film.
• Attrition due to inter-particle
collisions and shrinkage induced
breakage of the dried film allows
entrainment of the dry powder into
the drying gas for collection in
cyclone or baghouse.
FLASH DRYER

18. • Short contact time and parallel
flow make possible to dry thermo
liable materials.
• The dryer needs only a very small
area and can be installed outside a
building.
• The dryer is easy to control. The
low material content in the dryer
enables equilibrium conditions to
be reached very quickly.
• Due to small number of moving
parts the maintenance cost is low.
• The capital cost are low in
comparison with other types of
dryers.
• Simultaneous drying and
transportation is useful for
material handling.
ADVANTAGES DISADVANTAGES
• High efficiency of gas cleaning
system is required.
• Dryer cannot be used for toxic
materials.
• Not suitable for lumped
materials.
• Risk of fire and explosion.
• Generally, not all the particles
have same residence time in the
dryer.
• Drying of heat sensitive
products in this type of dryers is
very useful.
• They are successfully used in
food, chemical, pharmaceutical,
mining, ceramic and wood
industries.
• Widely used in plastic and
APPLICATIONS

19. • The drum dryer is an indirect type
dryer in which the feed to be dried
is maintained in a thin film on a
rotating steam heated drum.
• The feed being dried is spread over
the outside surface of the dryer.
Clinging to it drying continues ad
the hot drum rotates.
• At the end of revolution, the drum
comes to a ‘doctor blade’ which
scrapes the dried film from the
drum,when the product has made
about three quarter of a complete
rotation on the drum surface.
• The process is known as roller
drying.
• Drum diameter: 0.5 to 6m and the
length from 1m to 6m
• In operation, steam at temperature
to 200 degree celsius heats the
inner surface of the drum.
DRUM/ROLLER
DRYER

20. CLASSIFICATIO
N
DRUM
DRYERS
Number of
drums
Pressure
Feeding
arrangemen
t
Material of
constructio
n
A)Single
drum
B)Double
drum
C)Twin
drum
A)Atmosph
eric
B)Vacuum
A)Nip feed
B)Splash
feed
C)Dip feed
D)Roller
feed
A)Alloy steel
B)Stainless steel
C)Chrome
D)Nickel plate
steel

22. • Large production capacity
• Continuous operation
• Simple structure
• Easy to operate
• Less failure
• Low maintenance costs.
ADVANTAGES
• Large equipment
• High one time investment
• Installation and removal are
difficult
• Heat loss is large
• Thermal efficiency is low
• Material in dryer stay for long
time
DISADVANTAGES
A
P
P
L
I
C
A
T
I
O
N
S

23. VACUUM DRYER
• This equipment is a good example
of conduction drier.
• The vacuum oven consists of a
jacketed vessel to withstand
vacuum within the oven
• There are supports for the shelves
giving a larger area for conduction
heat transfer.
• The oven can be closed by a door.
• The oven is connected through a
condenser and liquid receiver to a
vacuum pump.
• Operating pressure can be as low as
0.03 bar, at which pressures water
boils at 25-35 degree Celsius.

24. • Drying takes place at low
temperature.
• Maximum retention of nutrition.
• There is little air present, so there
is minimum risk of oxidation.
ADVANTAGES DISADVANTAGES
• Drying takes place at low
temperature.
• Maximum retention of nutrition.
• There is little air present, so
there is minimum risk of
oxidation.
• Mainly used for puffed cereals.
APPLICATIONS

26. • Freeze drying is a process in which
water is removed from a product
after it is frozen and placed under
a vacuum, allowing the ice to
change directly from solid to vapor
without passing through a liquid
phase.
FREEZE DRYING
STAGES
• Freezing stage
a)Shell freezing
b)Centrifugal evaporative freezing
• Vacuum application stage
• Sublimation stage
Primary drying
Heat transfer
Vapour removal
Rate of drying
• Secondary drying
• Packaging

27. • Drying takes place at low
temperature.
• Product is light and porous
• The porous form of the product
gives ready solubility
• No concentration of solution prior
to drying
• Nutrition retention.
• There is little air present, so there
is minimum risk of oxidation.
ADVANTAGES DISADVANTAGES
• The porosity, ready solubility and
complete dryness yield a very
hygroscopic product. Unless the
products are dried in their final
container and sealed in situ,
packing require special
conditions.
• The process is very slow.
• Uses complicated plant which is
very expensive.
• Limited to certain types of
valuable products
• The method is used for products that cannot be dried by any other heat
method. These include biological products,eg:antibiotics,blood
products,vaccines,enzyme preparations and microbiological cultures.
APPLICATIONS