Pharmaceutical technology module notes

2. 2
COMMMON PROCESSES

3. 3
GRANULATION
& POWDERS

4. Granulation
• Is done to:
• improve flow properties of the mix
• improve compression properties of the mix
• prevent segregation of components in powder mix
• reduce production of toxic dust
• reduce possibility of ‘cake’ formation
• increase convenience of transport
4

5. 5
Granulation Techniques
Batch processes
High
shear
Mechanical
Extruders
Fluid bed
Spray
dryer
Mixers
Low shear
Fluid
bed
Mechanical
Continuous processes
Rotary
granulators
Roller
compactor

6. 6
Spray drying techniques
This a technology for conversion of a liquid, slurry or low-viscosity paste
to a dry free-flowing powder in one unit operation.
Advantages of spray drying
• The process can be run continuously for as long as there is a supply of
liquid product to be dried.
• The drying process is instantaneous making it suitable for heat
sensitive products
• Corrosive and abrasive material can be readily accommodated
because of minimal contact between the mechanical parts and
materials.
• Operation requirements for small and larger equipment are the same
making it labor cost effective
• The spray drying process can be fully automated.

7. 7
Stages of Spray Drying
Liquid Atomization
Spray-Air Contact and
Evaporation
Drying
Dried Powder Separation

8. 8

9. 9
Selection of atomizer
The choice of atomizer is determined by:
•Nature of the feed
•The characteristics of the spray
•Desired properties of the resulting product.
For a given spray drying application, the following should be
taken into consideration.
1.The feed capacity range of the atomizer for which complete
atomization is attained.
2.The atomization efficiency
3.Droplet size distribution at identical feed rates
4.Spray homonegeity
5.Operational flexibility
6.The feed properties
7.Suitability of dryer chamber design for atomizer operation
8.Atomizer experience available for the product in question

10. 10
Stages Spray drying Process
Atomization:
•This is the first stage of the drying process in which a
liquid disintegrate into many fine droplets.
•High surface-to-mass ratio is critical for optimum liquid
evaporation conditions and consequently the desired
properties of the resulting product.
Types of Atomizers
Centrifugal (rotary) atomizers
•These utilize either a rotating disk or wheel to disintegrate
the liquid film.
•Mean droplet sizes can be varied from 15 μm to 250 μm
by varying process parameters such rotating speed

11. 11
Pneumatic atomizers
•Atomization is accomplished by interaction of the liquid
with a second fluid normally compressed air.
•High air velocities are generated within the nozzles for
effective feed contact which break-up the liquid the
liquid into fine spray.
Advantages
•Liquid has a relative low velocity as it exit the nozzle,
hence require shorter flight path. This makes suitable for
pharmaceutical applications where smaller equipment is
used
•The simple design makes it easy to clean, for sterile
operation is prone minimal contamination.

12. 12
Pressure nozzle atomization
•Liquid feed is pressurized by pump and forced through a
nozzle orifice as a high speed film that readily
disintegrates into fine droplets.
•The feed is made to rotate within the nozzle resulting in
a cone-shaped spray pattern emerging from the orifice.
•Because of relatively high velocities a spray chamber of
at 2.5 m i.d. and 3 m in cylinder height is minimal
requirement
•Mean size of spray is directly proportional to feed rate
and inversely proportional to pressure.
•Pressure nozzle atomization generally used to form
coarse spray-dried particles (120 to 300 μm mean particle
size) with good flow properties.

13. 13
Illustration of a pressure nozzle atomizer

14. 14
Sonic Energy Atomizers
•Uses sonic energy and vibrations to produce a
fine spray
•It yet to find significant commercial applications
•Developments for special applications are on-
going e.g. for very fine sprays of mean size 20
μm
Advantages
•Operates at very low pressure
•Suitable for abrasive material

15. 15
Stage II: Spray-Air Contact and Evaporation
•Atomized liquid is brought into contact with a heated
gas for evaporation to take place.
•Spray-Air Contact is classified according to
movements within the drier:
•Counter-current flow: where air and spray enter the
opposite ends of the drier. Configuration is very
efficient in terms of heat utilization
•Co-current: where spray and drying air pass through
the drier in the same direction.
•Mixed flow: which incorporates both co- and counter
current. This configuration produces a coarse-free
product with relatively small drying chambers.

16. 16
Stage III: Drying
•This takes place in the drying chamber which is the
largest part of the drying system. The chamber can be tall
and slander or have a large diameter with a short cylinder
height.
•The volume is calculated by determining the mass of air
required for evaporation and multiplying with it by the gas
residence time
Stage IV: Dried Product Separation
A dried powder is formed as a result of drying process and
normally collects at the cone-bottom of the drying chamber

17. 17
Process Layouts for Spray dryers
Open-Cycle Layouts
In open-cycle layouts, air is drawn from the atmosphere,
passed through the drying chamber and exhausted back
to the atmosphere. Configuration is determined by the
fineness of the particulate product
Closed-cycle Layout
Closed-cycle layouts are used for non-aqueous feedstock
(e.g. organic solvent). An inert gas is used as drying
medium. The technique is employed when flammable
liquids, explosive or toxic products are used in the drying
process or where atmospheric pollution is not permitted.

18. 18
Layout of the open-cycle spray dryer system: A=
cyclone/scrubber and B=bag filter. A=air, f=feed, p=spray-
dried product, 1=spray dryer chamber, 2=cyclone, 3=wet
scrubber, 4=bag filter/collector

19. 19
Layout of the closed-cycle spray dryer system
Abbreviations: c=coolant, f=feed, l=solvent recovery,
p=spray-dried product, 1=dried powder, 2=cyclone, 3=liquid-
phase indirect heater, 4=heat exchanger, 5=scrubber-
condenser

20. 20
GRANULATORS
Commonly used granulation methods
•Wet Granulation
•Dry Granulation
•Hot-melt granulation
Equipment used during granulation processes is
classified into the following major categories based on
shearing strength generated on the powder bed.
•Low-shear Granulators
•Medium-shear Granulators
•High-shear Granulators

21. Wet Granulation
• low shear granulator
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22. 22
Planetory mix conical (orbiting) screw
mixer

23. 23
Rotating mixers

24. Wet Granulation
High-shear Granulator
•Consist of mixing bowl which may be jacked for heating or
cooling purposes, three-blade impeller and a chopper.
•Impeller rotates at 100 – 500 rpm
•Chopper rotates at 1000 – 3000 rpm to break-down wet
lumps
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25. 25
Horizontal high-shear mixer granulator

26. 26
Advantages over other granulation techniques
Short processing time.
Granulation of highly cohesive material containing
hydrophilic polymers which is not achievable in low-shear
granulation methods
Production of reproducible granules with uniform particle
size distribution
Obtaining predictable granulation end point determination
Reduction of process dust.
Greater densification and production of less friable
granules than low-shear granulated product.

27. 27
Fluid Bed Processing
• In fluid bed processing granules are
produced in a single piece of equipment by
spraying a binder solution onto a fluidized
bed.
• Fluidization is the unit operation by which
fine solids are transformed into a fluid-like
state through contact with a gas.
• At certain gas velocities, the gas will support
the particles, resembling a vigorously boiling
fluid where solid particles undergo extremely
turbulent motion.

28. 28
Fluidized bed granulator description
• This a system of unit operation involving:
 Conditioning of process air
 A system to direct it through the material to be processed.
 And has the same air exit unit void of the product.
• At the downstream end of the fluid bed processor, an exhaust blower or fan
is situated to draw the air through the entire unit.
Components:
• Air handling area unit,
• product container and air distributor,
• spray nozzle and
• disengagement area and process filters

29. Wet Granulation
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fluidized bed granulator

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31. 31

32. Dry Granulation
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33. 33
Binders used in Pharmaceutical Granulation
•Granulation is the most practiced unit process in
pharmaceutical manufacturing.
•Once again the purpose of granulation is to:
 Improve powder flow properties
 Reduce fine dust through agglomeration and
densification
 To improve solubility and dispersibility of powders
and tablets in water
Binders
•Granulation is achieved by adding a solvent as binder
fluid
•However, in most cases binders are also included by
either being pre-dissolved in a suitable granulating fluid
or by pre-blending with other formulation components

34. 34
Function of a binder
• To improve bonding between primary particles of the formulation,
thereby assuring granule strength and density.
• To provide , in the case of compaction into tablets, the necessary
thermoplasticity and toughness to improve formulation compactibility.
• Types of binders
• Traditionally natural polymers such as gelatin, gum acacia, gum
tragacanth, starch, sugars (glucose and sucrose)
• Current pharmaceutical practice has seen replacement of most natural
polymers with the exception of starch and acacia.
• New type of binders are derivative of celulose.

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36. 36
Other Granulating techniques
•Melt Granulation
•Effervescent Granulation
•Extrusion-Spheronization
•Roller Compaction Technology
•Supercritical Fluid Technology