This document discusses various types of mixing and homogenization. It defines mixing as combining two or more substances and describes different types of mixing like solid-liquid and gas-liquid mixing. It also defines positive, negative and neutral mixtures. The objectives, mechanisms and factors affecting mixing are explained. Finally, it describes common mixing and homogenization equipment like double cone blenders, propeller mixers, hand homogenizers, Silverson mixer homogenizers and colloidal mills and how they work.

1. MIXING AND
HOMOGENISATION
BY:Pratishruti Mishra
D.pharm 1st year
Aurosri Institute of
Pharmaceutical Education
and Research (AIPER)
Kadei,Tangi,Cuttack

2. MIXING:
Mixing may be defined as a unit operation in which two or
more substances are combined together.

3. TYPES OF MIXING:
Cohesive solis
Non cohesive solid
Mixing of liquid
Single phase liquid mixing
Mixing of immiscible liquid

4. Gas liquid mixing
Liquid solid mixing
Solid liquid gas mixing
Solid solid mixing

5. TYPES OF MIXTURE:
Positive mixture
Negative mixture
Neutral mixture

6. POSITIVE MIXTURE:
When two or more than two miscible liquids are mixed or
soluble solid is dissolved in water, the mixtures are called
positive mixture.
The mixture formed is a irreversible mixture.

7. NEGATIVE MIXTURE:
When two immiscible liquids are mixed or insoluble
solids are mixed with water it forms negative mixture.
For preparing such type of mixture a higher degree of mixing
of material is required.
The mixture formed is a reversible mixture.

8. NEUTRAL MIXTURE:
These mixtures are static in behaviour. (No tendency to mix
spontaneously , nor segregate when mixing)
Once mixed they do not separate after mixing.

9. OBJECTIVES OF MIXING:
Simple physical mixing of materials to form a uniform mixture.
To promote the chemical reaction to get uniform products.
Dispersion of solid in liquid to form suspension or paste.
Dispersion of two immiscible liquids to form an emulsion.

10. MECHANISM OF MIXING:
01. CONVECTING MIXING:
It is also known as bulk transport.
It takes place by transferring thr part of material
from one location to another location of the
system by means of blades or paddles of the
equipment.

11. 02. SHEAR MIXIMG:
This type of mixing occurs when a layer of
material flows over another layer resulting in
the layers moving at different speeds and
therefore mixing at the layer interface.

12. 03.DIFFUSION MIXING:
Diffusion mechanism occurs by random movement of
particles within a powder bed and causes them to change
their relative position in relation to one another.

13. FACTORS AFFECTING MIXING:
01. PARTICLE SIZE:
It is easy to mix two powder having approximate
the same particle sizes.
The variation of particle size can lead to separation
also,because the small particles move downward
through the spaces between the bigger particles.

14. 02.PARTICLE SHAPE:
The ideal particle is spherical in shape for the purpose of
uniform mixing.
The irregular shapes can become interlocked and there are
less chances of separation of particles once these are mixed
together.

15. 03. PARTICLE ATTRACTION:
Some particles exert attractive forces due to
electrostatic charges on them.
This can lead to separation.

16. 04. MATERIAL DENSITY:
It is difficult to mix two powders having different density.
This is due to the fact that dense material always moves
downward and settles down at the bottom.
Therefore, for uniform mixing of powders, proper attention should b
given to their density.

17. 05. PROPORTIONS OF MATERIAL:
The best results can be achieved if two powers are mixed in equal
proportions by weight or by volume.
In case there is a large difference in the proportions of two
powders to be mixed the mixing of powders is always done in
the ascending order of their weight.

18. 1. DOUBLE CONE BLENDER
2. PROPELLER MIXER
3. HAND HOMOGENISER
4. SILVERSON MIXER HOMOGENISER
5. COLLOIDAL MILL

19. DOUBLE CONE
BLENDER

20. PRINCIPLE:
01
The mixing of powder in double cone blender is due to
tumbling and shearing action with blade.

21. 02
CONSTRUCTION:
Double cone blender is made up of stainless steel
and is available in different capacity ranging from 5
kg to 200 kg or even more.
It consists of double cone on rotating
shaft.
There is an electric motor gear box by which we
control the speed of rotation.
The efficiency of rotation depends mainly on the
speed of rotation.
The common range of rotation is 30-100 rpm.

22. 03
WORKING:
The powder to be blended is fed from the hopper is approximately
50-60% of total capacity of blender..
As the blender rotates, the material undergoes tumbling motion and mixes
the material thoroughly.
Agitator blade can also be fixed in order to produce shearing action.
After a successful mixing the powders are collected.

23. 04
USE:
Double cone blender is used to produce homogeneous powder mixer.
It is an efficient design for mixing of powder of different densities.

24. 0
5
ADVANTAGE DISADVANTAGE
If fragile granules are to be
blended ,double cone
blender is suitable beacuse
of minimum attrition.
They handle large
capacities.
Easy to clean , load and
unload.
It needs high headspace for
installation.
It is not suitable for fine
particulate system.

25. PROPELLER MIXER

26. 06
PRINCIPLE:
Propeller mixer works on the principle of agitation.

27. 07
CONSTRUCTION:
It consists of an angle blades attached to the end of the shaft rotated by means
of motor.
Any number of blades may be used but 3 bladed design is most common.
Propeller is quiet small as compare to size of the vessel(ratio of diameter
between propeller and container is 1:20) but it's operational speed (usually
8000 rpm) compensate for the size and produce efficient mixing in case of low
viscosity liquid.

28. 08
WORKING:
The material is to be mixed is taken in a vessel and the propeller
bearing shaft is inserted.
The angle blades of propeller cause circulation of the liquid in both
axial and radial direction ensuring good bulk transport but low
shearing force.
The centrally mounted vertical propeller is however not
considered good as it produces vortex.

29. 09
ADVANTAGE DISADVANTAGE
This mixer is used when high mixing
capacity is required.
Effective for liquid which have
maximum viscosity of 2.0 Pascal.sec
uptown 10% solids of fine mesh size.
Effective gas liquid dispersion is
possible at laboratory scale.
Ex//Multivitamin elixiers, Disinfectant
solutions
Propeller are not normally effective
with liquid of viscosity greater then
5 Pascal.sec
Ex//Glycerin, Castor oil etc
The centrally mounted vertical
propeller produces vortex.

30. 10
VORTEX:
It is a powerful circular moving mass of water or wind that can
draw object into its hollow which may result in air entrapped
and bubble formation.

31. 11
HOW IS IT FORMED?
It is an unbaffled tank, a vortex is produced due to the centrifugal
force on the rotating liquid.
This creates a swirling motion in the liquid and the surface tends to go
upward near the vessel rim and download near the shaft .
So a 'V' shaped is formed , which is called as vortex.

32. 12
REASONS:
If the shaft is placed symmetrically in the tank.
If the blades of turbines are arranged perpendicular to the central
shaft.
At high impeller speed.
Unbaffled tank

33. 13
PREVENTION:

34. HOMOGENISATION:
Homogenisation is a process of preparing fine
emulsion from a coarse emulsion by converting
the large globular to small globular.
The apparatus used in the process of
homogenisation is called ' Homogeniser'.

35. PRINCIPLE:
The homogeniser are based on the principle that
the large globules in a coarse emulsion are broken
into smaller globules by passing them under
pressure through a narrow orifice.
14

36. TYPES OF HOMOGENISER:
Hand homogeniser
Silverson mixer homogeniser
Colloidal mill
15

37. HAND
HOMOGENISER:

38. 16
CONSTRUCTION:
It consists of a inlet valve , homogenising valve
and fine orific .

39. 17
WORKING:
The homogeniser is hand-operated and the coarse emulsion is
passed through a fine orific.
The emulsion is placed in the hopper of the homogeniser.
The up and down movement of the handle causes coarse emulsion to
draw in through inlet valve and pass through homogenising valve.
In this way the emulsion is forced to pass through the fine orifice(aperture
The oil globules are broken into fine globules of uniform size.

40. 18
SILVERSON MIXERHOMOGENISER:

41. 19
CONSTRUCTION:
It consists of an emsifier head which is covered
with fine meshed stainless steel sieve.
The emulsifier head consists of a number of
blades which rotates at a very high speed , in
order to produce a powerful shearing action.
The blades are rotated by using an electric motor
fitted at the top.

42. 20
WORKING:
The emulsifier head is placed in the vessel containing immiscible liquid,in
such a way that it should get dipped into it.
When the motor is started , the liquids are sucked through the fine
holes and the oil is reduced into fine globules due to the rotation of the
blades.
So a fine emulsion is produced which is then expelled out.
The intake and expulsion of the mixture set up a pattern of circulation.

43. COLLOIDAL MILL:

44. PRINCIPLE:
The size reduction is affected due to shearing,when the material
is passed between the narrow gap of milling surface of rotor and
stator.
21

45. CONSTRUCTION:
Colloidal mill contains of a rotor and a
starter.
The rotor rotates at a speed of 3,000 to
20,000 r.p.m.
The stator have conical milling surfaces
between which there is an adjustable
clearance between 0.002 to 0.3 inches.
22

46. WORKING:
The material e.g. emulsion and suspension is placed into the hopper of
the mill.
It is then passed through the narrow gap between the rotor and stator and
thus reduced to fine particle size.
23

47. USE:
Colloidal mills are capable of producing particles in micron size.
These are commonly used to prepare pharmaceutical
suspensions and emissions having particle size less than one
micron.
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48. THANKS！