2. DRYERS
• dryers are used to efficiently process large quantities of bulk materials
that need reduced moisture levels.
• Depending on the amount and the makeup of material needing to be
dried, industrial dryers come in many different models constructed
specifically for the type and quantity of material to be processed
3. Drying
• Drying is commonly the last stage in a manufacture process.
• Drying is the final removal of water from material (usually by heat)
Non –thermal drying
• 1-Adsorption by desiccant (desiccation)
4. Purposes of drying
In pharmaceutical technology, drying is carried out for one or more of the
following reasons:
1-To avoid or eliminate moisture which may lead to corrosion and decrease the product or
drug stability.
2-To improve or keep the good properties of a material, e.g. flowability, compressibility.
3-To reduce the cost of transportation of large volume materials ( liquids)
4-To make the material easy or more suitable for handling.
5- Preservative.
6-The final step in: Evaporation- Filtration- Crystallization.
5. Heatless Desiccant Dryers
Compressed air is provided to power
pneumatic valve actuators, drive air motors,
convey raw material and products, activate
analytical instrumentation, and for cooling
services. To be effective, compressed air
must be dried to remove moisture, and
other contaminants, which contaminate and
corrode critical components
6. Heatless Desiccant Dryers
Provide a continuous supply of
compressed
air at low dew points
Operation:
One tower is on-line drying the air while
the
other tower is off-line being regenerated
Towers alternate so that the air stream
is always exposed to dry desiccant
7. REFRIGERANT DRYER
• A refrigerant dryer uses a refrigerant circuit and heat exchanger(s) to pre-cool
air, refrigerate it to condense out moisture vapor, and then re-heat the air to
prevent pipe sweating downstream. Refrigerant dryers can lead to a pressure
dewpoint (PDP) as low as +3°C/+37.4°F for many applications where there is a
need for dry air. They can be used at different pressures and consume no
processed compressed air.
10. • Refrigeration drying is a process in which the compressed air is cooled by a refrigerant in a
heat exchanger. This condenses the water vapour in the compressed air and separates it out.
The greater the difference between inlet and outlet compressed air temperature, the greater
the amount of water condensed. The lower the compressed air's cooling temperature, the
less moisture remaining.
Drying comprises two phases
• First phase: The warm compressed air enters an air / air heat exchanger in the opposite
direction to the compressed air already cooled and exiting the unit. No extra energy is
required for this process. Around 70 percent of the water vapour is removed as
condensate.
• Second phase: The compressed air flows through an air / refrigerant heat exchanger and
cools to the specified pressure dew point (e.g. 3°C). The remaining moisture condenses
before this point is reached, is removed and discharged through a condensate drain.
11. Advantages of Refrigerant Type Air Dryers
•Low, initial capital cost.
•Relatively low operating cost.
•Low maintenance costs.
•Not damaged by oil in the air stream (although, filtration
normally is sometimes recommended).
•Limited dew point capability.
Disadvantages of Refrigerant Type Air Dryers
12. Air Dryer Selection Factors
• Flow Capacity
• Drying Capacity
• Air Compressor Duty Cycle
