16. CLASSIFICATION OF DRYERS
Convection/direct drying/Adiabatic dryers
Indirect /contact drying /Non Adiabatic dryers
Dielectric drying
Freeze drying or lyophilization
Super critical drying
Natural air drying
17.
18.
19. • Conduction ,convection
,radiation
• Electromagnetic field
• Adiabatic and non adiabaticThermal
• expression
• Extraction
• Adsorption
• desiccation
Non thermal
20. Mode of operation
batch wise
continuous
Heat Input Type
convection
conduction
radiation
electromagnetic fields
adiabatic and non adiabatic
21. State of material in dryer
stationary
moving ,agitated, dispersed
Operating pressure
vacuum
atmospheric
Drying medium
air
superheated steam
flue gases
Drying temperature
below boiling point
above boiling point
below freezing point
22. Relative motion between drying medium and drying solids
co-current
counter current
mixed flow
Number of stages
single
multistage
23. “Dried” – the final product must be solid
In the form of a continuous sheet
Long pieces (wood)
Particles (cornflakes)
Powder (sand , salt , milk powder)
25. It is used for chemicals of all types
1. Pharmaceuticals
2. Biological materials
3. Foods
4. Detergents
5. Wood
6. Minerals
7. Industrial wastes.
26. THE MATERIALS DRIED MAY BE IN THE FORM OF
1. Thin solutions
2. Suspensions
3. Slurries
4. Pastes
5. Granular materials
6. Bulk objects
7. Fibers
8. Sheets.
27. Drying evaporate
a few ounces/ hour - 10 tons / hour in a single dryer.
Drying temperatures may be as high as
1400°F (760°C),
as low as -40°F (-40°C) in freeze drying
Dryers range in size
small cabinets to spray dryers
steel towers 100 ft (30 m) high and
30 ft (9 m) in diameter.
28. Removal of moisture from liquids -Distillation
done in distillation columns
Removal of moisture from gases – Adsorption
done in Adsorbers
30. TRAY DRYER
Box dryer /Hot air Oven Dryer
Simplest form
A cabinet with a heater a the bottom
No control of heat transfer and humidity
31. TRAY DRYER
when the production rate is small
used to dry wide range of materials,
but have high labor requirement for loading and unloading the
materials
Drying operation is slow
Requires several hours to complete drying of one batch.
With indirect heating often the dryers may be operated under
vacuum.
Vapor from the solid may be removed by an ejector or vacuum
pump
36. TUNNEL DRYER
Modification of tray dryer
Oven is replaced by a tunnel
Receives damp material at one end and discharges the dried
product at the other end
Batch wise or continuously
37. FREEZE DRYER
Processing of food
Pharmaceuticals
Diagnostic kits
Restoration of water
Manufacture of sulfur coated vials
38.
39.
40. Removal of water vapours from a frozen solution by sublimation
Hence sublimation drying / lyophilization
41. COMPONENTS OF A FREEZE DRYER
1.A chamber for vacuum drying
2.A vacuum source
3.A heat source
4.A vapour removal system
43. • preservation• Storage is easy
• Raw
drugspecification
• Final product
Light
Porous
Excellent
solubility
No specification
Heat sensitive
materials
Minimum loss of
volatile material
Sterility
maintained
Oxidation is
minimized as
there is no
contact with air
At room
temperature
If properly sealed
in an inert
atmosphere
44. • expensive • Very hygroscopic
• Packaging is
very important
Final
product
• Period of drying
is long
• Not less than 10
hrs
Duration
46. ROTARY DRYER
Modified form of the tunnel dryer
Material is passed through a rotating cylinder
Consist of a cylindrical shell -10m
10 rpm
Heating is done by direct or indirect method
47.
48.
49. PRINCIPLE
The sleeve column structure of the rotary drying machine or
rotary dryer shortens the dryer length in multiple times.
As the heat delivery area is greatly reduced, so is the heat
consumption. However, the multiplication heat exchange area
increases the heat performance.
50. FEATURES
High mechanization
Strong production capability
Continuous operation
Excellent and simple structure
Steady operating process under resistance of the drum
Easy operation
Little malfunction
Low maintenance cost
Power consumption
Wide application range
Good drying effect.
51. FLUIDISED BED DRYER
Theory
Gas is allowed to flow upward through a bed of solid particles
At a velocity greater than the settling velocity of the particles
The particles are partially suspended in the gas stream
Resultant mixture of solid and gas behave like a liquid
The solids are said to be fluidised
52. OPERATION
Due to induced draft created by specially designed heavy-duty fan,
the atmospheric air is drawn through air filter
The filtered air is then heated to the required temperature by
electric/ steam radiator
The hot air passes through the product container and the product is
dried by air fluidization
The air circulation is controlled by damper
The filter bag prevents fine particles from carrying over to exhaust
air stream
53. SELECTION
Selection of capacity of fluid bed dryer depends upon
Bulk density,
Drying temperature
Moisture contents of wet material to be dried
Pharmaceutical granules with 20-25% moisture can be dried in 30-
45 minutes at 800 C approximately
54. SALIENT FEATURES
Better productivity and lesser drying time with less handling
More hygienic
Uniform drying at low temperature
Models available from 2 Kg to 300 Kg capacity
55.
56.
57. DIELECTRIC DRYING
Or microwave drying
Microwaves are converted in to internal heat
The heating effect produced –interaction of rapidly oscillating
electric field
Lead to rapid heating
60. DRYERS USED FOR SOLUTIONS AND
SUSPENTIONS
1.Drum dryer
2.Spray dryer
61. ROTARY DRUM DRYER
Rotary drum dryer/ dryer drum
drum drying equipment or cylinder dryer, is the most common
and widely used drying equipment.
There are two kinds of drum dryer:
direct heat transmission rotary drum dryer
indirect heat transmission rotary drum dryer.
62. PRINCIPLE
Materials are sent from the higher section of the drum and contact
with hot air.
With the rotation of cylinder, the material flow down to the lower
end with the effect of gravity
discharge after drying.
Since the rotary drum dryer is working under negative pressure
conditions, feeding and discharge end use seals to prevent air
leakage.
1. High productivity.
2. Easy operation.
63. SPRAY DRYER
Both for solutions and suspensions
Useful for drying thermo labile substances
Milk
Soap
Detergents
64. Liquid to be
dried is sprayed
through an
atomizer
Droplets are
readily
evaporated
Solid dried
particles are
settled down at
the bottom
70. • The raw
material
solution, dried
directly into a
fine powder Does not
change the
nature of
raw
materials
after
High
concentrated
and high-
viscosity
liquid can
also be dried
The instant
dry, drying
time is
short.
The heat-
sensitive
material, the
raw material
can be
maintained
color, smell
and taste.
73. STANDARD TURBO-DRYER
consists of a stack of slowly rotating circular trays.
Material is fed onto the top tray.
After one revolution the material is wiped onto the next lower tray
where it is mixed, leveled, and then after one revolution, is wiped to the
next tray
The operation is repeated.
The trays are contained in an enclosure in which heated air or gas is
circulated by internal fans.
74.
75. ADVANTAGES
Even, thorough, and rapid drying
Uniform inside temperature or zoned temperature regions.
The closest product temperature control of any dryer possible.
Can give the lowest residual moisture of any dryer.
76. Easy startup and operation on different materials
Low maintenance costs because of its unparalleled reliability
Low energy costs.
Low labor costs
Can use any heating medium: steam, gas, electricity, oil, high
temperature oil or waste gas from other operations
.
77. Does low temperature drying as low as 60°F without vacuum or
up to 1200°F
Available in laboratory sizes, package units, and large field erected
sizes
Manufactured in a wide range of materials
Vertical construction, little space requirements.