Equipments used in dispersed systems

1. EQUIPMENTS USED IN
DISPERSE SYSTEM
Presented by:
L.Pavani
Roll No:256212886018
M.Pharm 1st yr
Pharmaceutics
Guided by:
Dr.S.B.Bhanja
M.Pharm,Ph.D

2. Definition:
 Dispersion system is defined as a
heterogenous two phase system in which
internal (dispersed,discontinous ) phase is
distributed or dispersed within the continuous
(external) phase or vehicle.
 The internal and external phase may be
solids, liquids and also gases.
Eg.suspensions,emulsions,aerosols

3. Dispersion equipments
A. Mixers
B. High speed dispersers
C. Rotor stator mixers
D. Combination mixers
E. In- line mixers
F. Non- mechanical disperse processing
G. Fine suspension and size reduction
equipment

4. Mixers
 Propeller mixers
 Turbine mixers
 Anchor mixers
 Scraped surface agitators
 Counter rotation

5. Propeller mixers
 The most often used mixing implement is marine
propeller mixer.
 These machines use rounded,pitched,three blade
design that produces mostly axial flow
 They provide good flow and blending capabilities in
small batches of low to medium viscosities
 Propellers mixers can be installed on vertical
centerline or through the side wall of process vessel
 They can be operated at around 300-400rpm
 These are used mostly for liquid-liquid blending
applications in some easily producible suspensions.

6. PROPELLER MIXERS
Marine Propeller mixer
Clamp mounted
portable mixer

7. Turbine mixers
 The most versatile of all mixers in the entire span of
mixing equipments are the axial and radial flow turbines
 Turbines mixers can be made to handle huge
batches,evenupto 5,00,00gal & suitable for
emulsification process.
Radial Flow turbine Axial flow turbine

8. Anchor mixer
 It is low speed and low capability
 The anchor agitator is a slow
(50rpm) device whose sole
function is to rotate the contents
of a batch in a radial direction
without providing any significant
shear
 They are typically designed to be
able to withstand a maximum
viscosity beyond which they
might actually blend or break.

9. Scrapped surface agitators
 A flexible or movable
blades are attached to
the anchor for the
purpose of actually
scrapping the side
walls,they are known as
scraped surface
agitators
 These are definitely
required in emulsification
equipment where heat
transfers are necessary

10. Counterrotation agitator
 It consists of anchor agitator
and counterrotating set of
cross bars provides excellent
blending
 These works well on
materials with viscosities from
5000-25,000cps
 By installing a stationary
baffle,some mixing
capabilities are improved

11. High speed Dispersers
It is also called as saw blade disperser
 This machine consists of a variable speed shaft
connected to an impeller with a serrated edge
 The tip speed is set around 4000 ft/min
 The diameter of impeller should be 1/3 of
diameter of vessel
 The impeller should be located one impeller
diameter off the bottom of vessel
 It can deagglomerating particles when the
viscosities between 10,000 to 20,000cps.
Application:
It is used for pigment dispersion,dye stuffs,
carbon dispersion and paints

12. High speed disperser
Limitations:
 Air incorporation is
another problem so it
is best used for
suspensions and not
for emulsions

13. Rotor/stator mixers
 This mixing machine uses an impeller that is
installed at a close tolerance to a stationary
housing,which baffles and restrict the flow
caused by the rotation of the impeller in the
liquid.
 Particles caught between rotor & stator are
crushed and separated by mechanical action of
the impeller.
 They are three types:
1. Radial flow with stator
2. Rotating stator
3. Axial flow rotor/stator mixers

14. RADIAL FLOW WITH
STATOR ROTATING
STATOR
AXIAL FLOW ROTOR/STATOR
MIXER

15. COMBINATION MIXERS
 Better control of temperature and pressures
 Eliminates line loses caused by pumping from
tank to tank
 Saves floor space
 Simplifies the process, save labor costs
Types : Anchor plus rotor/stator
Anchor plus disperser
Counter rotating with coaxial rotor/stator

16. Achor plus rotor/stator
 It is combination of simple anchor
agitator with a rotor/stator mixer
 It provides a high shear rates for
dispersion and emulsification
 It is beneficial if there is
requirement to pull down powders
from the top
Limitation:
 It is difficult to design the anchor
such that it allows the placement
of the high shear mixer close to
the bottom of the vessel.

17. Anchor plus disperser
 It is combination of
high speed
disperser with an
anchor agitator
 It works well on
medium to high
viscosity
suspensions

18. Counterrotating with coaxial
rotor/stator
 This design is known as triple action mixer,combines the
high viscosity mixing capabilities of counterrotating axial
flow cross bars with a standard anchor type scraped
surface agitator and also with a high speed rotor/stator
mixer
 It is capable of generating fine dispersions and fine
droplets of the internal phase for stable emulsions
 It can operated at viscosity of 50,000cps
 They are always jacketed for heating and cooling
because it is necessary in case of preparation of creams
and ointments

19. Counterrotating with coaxial
rotor/stator
Advantages:
 Handles wide range of
viscosities from water thin
to as high as 1million cps
 Disperse and emulsifies
very efficiently
 Provides shortest mixing
time
Disadvantages:
 Difficult to clean due to
complicated design

20. IN LINE MIXERS
1.Rotor/stator mixer disperser emulsifier
2.Colloidal mill
3.Piston homogenizer
4.Ultrasonic vibrating homogenizer
5.Micro fluidizer
6.Low pressure cyclone emulsifier
7.Homogenizer/Extruders
8.Static mixer

21. Rotor stator mixer emulsifier
disperser
 These mixers acting as submerged pumps
design can be made that places the
rotor/stator in a pump housing and allows for
product to be pumped through itself.
 The product inside the rotor/stator mixing
pump,the droplets and particles subjected to
a wide variety of high shear rates.
 It is designed with fine tolerance rotor/stator
gaps that promotes high shear rates and high
amount of shear per pass through.

22. Stage 1
Stage 2
Stage 3

23. Colloid mill
 It is used to disperse the solids into liquids and
to emulsify liquid-liquid systems.
 These generally used as polishing machines for
emulsions or suspensions because they
produce fine particle or droplet size product to
enhance a products stability.
 The rotor/stator gap is generally set between
0.030 & 0.001 inch.
 They are operated at speed of 3600 rpm
 The rotor diameter is 10-30cm provides flow
rates in the area of 4000-6000L/hr depending
upon the viscosity.

24. Colloidal mill

25. Advantages :
 Shear rates high than in rotor/stator
machines
 Colloidal mill produces emulsions and
suspensions with particle size distribution
smaller than the particle sizes obtainable
using fixed gap rotor/stator mixers.
Limitations :
 Flow rates lower than in rotor/stator machines
 Not used for abrasive products

26. Piston homogenizers
 It is the most powerfull device for producing
emulsions and suspensions
 It uses high power positive displacement piston
type pump to produce pressure of 3000-10,000
psig and then force the premixed product
through a specially designed restricting wall
where a extremely high shear forces are exerted
 Here turbulence and high shear are the major
parameters in size reduction

27. Piston homogenizers
 It having continuous
Capabilities of 2500L/hr at
15hp to 50,000L/hr at
150hp
Limitations:
 They cannot handle the
product feed above 200cps
 High maintanence cost and
down time
 Lack product homogenity
and batch to batch
variability

28. Ultrasonic vibrating
homogenizer
 Has similarity with high pressure
homogenizer effective device for dispersing
and emulsifying
 It uses a positive displacement pump to force
the premixed liquid through an elliptical
opening at a speed of 100m/sec
 This high speed flow impinges on to the edge
of blade shaped obstacle called a vibrating
knife.

29. Ultrasonic vibrating
homogenizer
 Capacities and
pressures of systems
range from laboratory
units, producing 4-
10L/min at 1200-1700
psig requiring 2-5hp,to
full scale productions
units with capacities of
upto 450L/min at
350psig requiring 60hp.

30. Continuous dual feed system configuration using
ultrasonic homogenizer

31. microfluidizer
 This device uses a high pressure positive
displacement pump operating at a pressure of 500-
20,000psig which accelerate the process flow upto
500m/min through the interaction chamber
 The interaction chamber consists of small channels
known as micro channels having diameter narrow as
50μm and cause the flow of product to occur as very
thin sheets.
 The configuration of micro channels within the
interaction chamber ressembles Y-shaped flow
streams in which the process stream divides into
these micro channels,creating two separate micro
streams

32.  The micro streams are then brought together in
an impingement area through which all of the
product must flow
 At the impingement area the collision of the two
high speed flow streams in a very tight spot
creates various droplet size reduction and
different mixing mechanisms such a
cavitation,implosion,shears and turbulence
 The micro fluidizer technology satisfy the
requirements for producing finest emulsions
known as micro emulsions

33. Flow path through the microfluidizer

34. Low pressure cyclone emulsifier
 It is used for formation of emulsions and
suspensions
 the shear arises from the difference in the
velocity of the fluid,as the fluid travels in a spiral
towards the center
 They operates in the 200psig and capacities of
7.5-225L/min.
 The recommended viscosity limit is 1-2000cps.
 They are capable of producing emulsions in the
2-10μm range.

35. Working :
 Product enters through
tangential entry port
 Product is forced to
circulate in concentric
layers towards the
center and ends of the
chamber
 Shear arises from the
difference in the
velocity of fluid,as the
fluid travels in a spiral
towards the center Cross section of flow path
through the interaction
chamber

36. Homogenizer/Extruder
 It is a high pressure homogenizer with an
adjustable valve having production capacities
from 8mL/hr to 12000mL/hr
 A positive displacement pump produces
pressure up to 30,000psig.
 The apparatus capable of producing fine
emulsions and liposomal dispersions

37. Static mixers
 A true low shear and low energy requirement
device for emulsifying immiscible liquid
mixture is the static mixture.
 It is also called as pipe line mixture,this
device is actually a series of specially
designed baffles in a cylindrical pipe.

38.  These simple devices are extensively used for
the preparation of unstable emulsions for liquid-liquid
extraction purposes
 Size distributions obtainable range from 100-
1000μm

39. Nonchemical disperse
processing
Critical fluids liposome process:
 Near critical or super critical fluid solvents with or
without polar co-solvents for the formation of
uniform and stable liposomes having high
encapsulation efficiences.
 Super critical fluids can be uniquely used to
encapsulate very hydrophobic molecules
 Super critical fluids are gases such as carbon
dioxide & propane

40.  When these fluids compressed at conditions
above their critical temperature and
pressure,these substances become fluids
and ability to dissolve other materials.
 The gaseous characteristics increases mass
transfer rates,thereby significantly reducing
processing time.
 Small added amounts of visible polar co-solvents
such as alcohol can be used to
adjust polarity and to maximize the selectivity
and capacity of the solvents

42. Fine suspensions and size
reduction equipment
Types:
1. Triple roll mill
2. Ball mill
3. Agitated bead mill

43. Triple roll mill:
• Disperse small tightly bound agglomerates
and hard discrete particles
 Particles are subjected to
High shear
Mechanical crushing
Smearing

44. BALL MILL
 It is used for size reduction fine solid discrete
particles or for deagglomeration of very tightly
bound agglomerates.
 The machine consists of cylindrical drum into
which a charge of heavy spherical balls
usually metal or ceramic is loaded along with
the components of the dispersion.

45. Ball mill
Limitations
Typically time consuming process,milling time are
often measured in days.

46. Agitated bead mills
 A Modernized improvement of the ball mill is the
agitated bead mill
 The bead mill uses a charge of inert small balls to 2-
8mm diameter
 Media mill- if beads are ceramic
 Shot mill- if beads are steel
 Sand mill- if grains of sand are used
 The Design consist of a cylinder which can be either
vertical or horizontal,that has a high speed
agitator,which is capable of fluidizing the charge of
beads,causing them to collide at very high speed.

47.  The premix is pumped through the
housing.There is a high probability that each
particle must be repeatedly subjected to the high
stresses that result when the beads collide with
each other or the high speed impeller
 Agitated bead mill is used in pigment dispersion
industry due to its fine solids grinding and
dispersing capabilities.It is not often used in
pharmaceutical industry except when particle
size requirements falls below 10μm.

48. Reference
 Pharmaceutical dosage forms,disperse
systems volume 3 by
Lackman,Lieberman,Marcel Dekker,NY.pg
no:291-362
 Pharmaceutical engineering(principles &
practices) by C.V.S.
Subrahmanyam.pg.no:155,161,229.