pharmaceutical drying its advantages disadvantages a recent invention in the pharmaceutical drying process.

1. PRESENTATION ON PHARMACEUTICAL
DRYING
Submitted to,
Zaki Farhad Habib
Submitted by,
MD. Mehedi Hasan
NORTH SOUTH UNIVERSITY

2. DRYING
What is drying –
Drying is the process of thermal removal of water to about 15-20% moisture, at
ambient dry condition.
In drying, dry solid is the product

3. NEEDS OF DRYING
• To make products stable.
• Preparation of powder and granules
• Reducing the bulk and weight
• Dried before extraction to facilitate grinding and to avoid deterioration-Crude
drugs of animal and vegetable origin-chemical decomposition.
• Preparation of certain products like dried Aluminum hydroxide, spray dried
lactose and powder extracts

4. CHOICE OF METHOD OF DRYING
• Product is sensible to heat or not
• Nature of the solvent
• Process is to be carried out under aseptic condition
• Quantity of products to be dried
• Available source of heat
• Cost involved

5. PRINCIPLES OF DRYING
The general principles for efficient drying can be summarized as follows
1. Large surface area for heat transfer.
2. Efficient heat transfer per unit area (to supply sufficient latent heat of
vaporization or heat of sublimation in case of freeze-drying)
3. Efficient mass transfer of evaporated water through any surrounding vapor
boundary layers, i.e. sufficient turbulence to minimize vapor boundary layer
thickness.
4. Efficient vapour removal , i.e. low relative humidity air at adequate velocity.

6. A pharmaceutical dryer is a machine or device that is used during drug
manufacturing which carry out the “drying” process.
 Dryers are used in a variety of industries, such as the food processing,
pharmaceutical, paper, pollution control and agricultural sectors.
WHAT IS PHARMACEUTICAL DRYER?

7. TYPES OF DRYER
Dryer for dilute solutions ,suspensions and slurries:
 Drum dryer
 Spray dryer
Dryers for damp solid materials:
Tray or shelf dryer
Tunnel dryer
Rotary dryer
Fluidized bed drying
Vacuum dryer
Freeze dryer

8. DRUM DRYER
Principle :
In drum dryers, slurries or pasty feedstock's are dried on the surface of a
slowly rotating steam- heated drum. A thin film of the paste is applied on the
surface in various ways. The dried film is doctored off once it is dry and
collected as flakes (rather than powder).
Working:
Liquid is kept in a feeding pan in which the heated drum is applied to the
surface and spreads to a film which dries rapidly.
The dried product is scrapped from the surface of the drum by means of
Doctors knife” in the form of flakes.
The drying rate can be controlled by adjusting rotation speed and
temperature of drum

9. DRUM DRYER

10. USES
Milk products.
Starch powder.
Iron salts.
Suspensions of kaolin or zinc oxide.

11. ADVANTAGES
• It is quick method.
• Compact.
• Short heating time.
• Drying temperature can be reduced by enclosing in a vacuum chamber.

12. DISADVANTAGE
Operating conditions are critical and it is necessary to introduce careful control
on:
 Feed rate.
 Temperature of drum.
 Thickness of film.
 Speed of rotation of drum.

13. SPRAY DRYER
Principle
 In the spray dryer the fluid to be dried is atomized in to the fine droplets.
 Which are thrown radially in to a moving stream of hot gas.
 The temperature of the droplets is immediately increased.
 Fine droplets get dried instantaneously in the form of spherical particles.
 This process completes in a few seconds before the droplets reach the wall of the dryer.

14. CONSTRUCTION
 It consist of a large cylindrical drying chamber with a short
conical bottom, made up of stainless steel.
 Diameter of 2.5-9 meters and height 25 meters or more.
 An inlet for hot air is placed in the roof of the chamber and
another inlet carrying spray disk atomizer is set in the roof.
 Spray disk is about 30 mm in dia. and rotates at a speed of
3000 to 50000 rpm.
 Capacity of spray dryer – 2000kg/hr.

15. WORKING

16. WORKING
Drying of materials in spray dryer involves three stages.
1. Atomization of liquid
The feed is introduced through the atomizer either by gravity or by using suitable
pump to form fine droplets.
The properties of fine product depends upon the droplet form. Atomizer of any type:
1. pneumatic atomizer
2. pressure nozzle type
3. spinning disc atomizer
Rate of feed adjusted in a such a way that droplets should be completely dried
before reaching walls of drying chamber.

17. 2. Drying of the liquid droplets:
 Surface of a liquid drop is dried immediately to form a tough shell. Liquid inside must
escape by diffusion through the shell at a particular rate.
 Heat transfer from outside to inside takes place at a rate greater than liquid diffusion rate.
As a result heat inside mounts up which allow the liquid to evaporate.
 The shells thickness decreases where as permeability for vapor increases. If the shell is
neither elastic nor permeable it ruptures and pressure escape.
3. Recovery of the dried product:
Centrifugal force of atomizer drives the droplet to follow helical path. Particles are dried their
journey and finally fall at the conical bottom.
All these process are completed in a few seconds. Particles size of the final ranges from 2 to
500mm.

18. Advantages
 It is continuous process and drying completes within 3 to 30 seconds.
 Product of uniform and controllable size can be obtained.
 Labor cost is low.
 Volatile solvent can be recovered.
Disadvantages
 The spray dryers is very bulky (height of 25 m and diameter of 9 m)
Lots of wastage of heat.
 Huge equipment is not easy to operate.
 Expensive process.

19. Uses
 Useful for all solution or in suspension form.
 For drying of thermo labile materials e.g. antibiotics.
 Suitable for both soluble and insoluble substances e.g. citric acid, gelatin, starch
 Drying of Boric Acid, Methyl cellulose, Sulphur milk, soap and detergents.

20. Vacuum Dryer
PRINCIPLE:
In vacuum dryer, material is dried by application of vacuum. When vacuum is created the
pressure is lowered so that water boils at lower temperature. Hence water evaporates faster.
The heat transfer become efficient .
Working
For drying the material is spread on trays which are placed on steam heated shelves in the
jacket of vacuum oven.
It provides large surface area for heat transfer by conduction and is provided with door.
The oven is connected through condenser and receiver to a vacuum pump. The vacuum
pump can be directly connected to oven.

21. USES:
1.Heat sensitive material, which undergoes decompositions.
2.Dusty and hygroscopic material
3.Friable dry extracts
4.Drugs which required porous end products
6.Drugs containing toxic solvents
Tray dryer

22. Advantages
Thermo labile substances can be dried at a low temperature and chances of oxidation are
reduced.
During the manufacture of dry extract, a porous and friable product is obtained which is
especially useful in tablet manufacturing.
By the use of condenser the solvent can be recovered from the product.
Disadvantages
Heat transfer may be low and non uniform.
It is not be suitable option for large scale drying.
Labor and running costs are high.
After drying a grinding process is necessary to get powder product.
There is danger that the finally powder material may be drawn off by vacuum pump, and
filter that requires frequent cleaning have to be provided

23. FREEZE DRYER
PRINCIPLE:
Drying occurs below the triple point of the liquid by sublimation of the frozen moisture into
vapor, which is then removed from the drying chamber by mechanical vacuum pumps or
steam jet ejectors. Generally, freeze drying yields the highest quality product of any
dehydration techniques.
BASIC PROCESS OF BIOLOGICAL DRUGS FREEZE-DRYING
The technical procedures of drug freeze-drying consist of four processes:
preparation and freezing,
primary drying (sublimation drying),
secondary drying (desorption drying)
package.

24. Uses:
It is used in production of dosage forms which are thermo labile such as injection
solution and suspension.
Used for drying the following products.
Blood Plasma
Bacterial and Viral Culture.
Antibiotics and plant extract.
Steroids, vitamins and enzymes.

26. ADVANTAGE:
Can prevent the active components from denaturation, Oxidation
Can greatly reduce the loss of volatile components in drugs.
Inhibit the growth of microorganism and the activity of enzyme in drugs.
Maintain the original structure.
Have good rehydration property.
Freeze dried drugs can be stored at room temperature for a long time
DISADVANTAGE:
1. Frozen drugs will melt, collapse if the temperature is higher than the optimum temperature.
2. If the temperature is too low, refrigeration load will causing excessive energy consumption and
the sublimation rate will be decreased greatly
3. It is a time and energy consuming process
4.Equipment and running cost is very high.
5.It is difficult to adopt the method for solutions containing non-aqueous solvents.

27. CONVENTIONAL DRYING METHODS
SUFFER FROM THE FOLLOWING
MAJOR LIMITATIONS
1. Freezing and moderate low temperatures cause damage to thermolabile
biomolecules.
2. Process is lengthy and time consuming.
3. If formulated successfully, storage facility such as cold chain storage
transport is a must to maintain stability.
4. Not suitable for bulk aseptic production.

28. NEW TECHNOLOGY OF DRYING
Preservation by Foam Forming Drying is a new technology proposed by
Bronshtein in 1996 .
According to Bronshtein , this belife in low
temperature drying with minimum damage is not correct.
Before Bronshtein’s invention of foam formation no scalable technology had been
proposed to preserve thermolabile biomolecule at ambient temperature

29. FOAM FORMATION PROCESS
The biological solutions or suspensions are first transformed into mechanically
stable dry foams.
 Samples are then subjected to stability-drying at elevated temperature to
increase the Tg
Activity yield after rehydration of foam-dried sample is achieved by proper
selection of protectants, which are dissolved in the suspension before processing.

30. ADVANTAGES OF PFF
1. More scalable process compared to freeze drying, which has limitation of cake
height in container.
2. Does not require freezing of sample before drying; therefore, it is more efficient,
gentle and less damaging.
3. Less time consuming and more energy-efficient.
4. Allows effective high ambient temperature stabilization with minimum loss of
activity during drying and storage.
5. It offers the potential to deliver biomolecules outside the cold chain storage
6. Lends itself as aseptic process due to higher vapour pressure above sample
during PFF, leading to less surface area exposure and less exposure time.

31. APPLICATIONS OF PFF
PFF has been used successfully for stabilization of thermolabile enzymes and
pharmaceuticals such as amphotericin, urokinase, luciferase, β-galactosidase, lactate
dehydrogenase, isocitric dehydrogenase etc.
Live viruses like lasota, herpesvividae, paramyxovividae, flaviviridae, parvoviridae
and retroviruses are stabilized by foam formation by using vacuum foam drying
technique.
Gram-negative bacteria such as E. coli and B. bronchiseptica and gram-positive
bacteria such as Lactobacillus acidophilus and Lactococcus lactis subsp. Cremoris
are stored for longer time at 37oC temperature.

32. REFERENCES
 https://www.ncbi.nlm.nih.gov/pubmed/28925794
 Aulton's pharmaceutics; the design and manufacture of medicine.
 Classification and selection of industrial dryers by Arun S Mujumdar.
 https://www.ethz.ch/content/dam/ethz/special-interest/mavt/process-engineering/particle-
technology-laboratory-dam/documents/lectures/practica/lecture-documents-
2016/Additional_theory.pdf
 Mehta RM, Pharmaceutics-I: introduction to the drying process (1996), Page no: 194.
 C.v.s subrahmanyam et al., pharmaceutical engineering principles and practices-filtration,
2001, page no. 394 - 397.
https://www.researchgate.net/publication/242426874_Vacuum_foam_drying_New_technology
_for_preservation_of_sensitive_biomolecules

33. Jazak Allah