MIXING.pdf
3,154 views
91 slides
Dec 28, 2023
Slide 1 of 91
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
About This Presentation
Pharmaceutical engineering bpharm 3rd sem mixing notes
Slide Content
MIXING
Dr. Mrs. SUPARNA S BAKHLE
ASSOCIATE PROFESSOR
PHARMACEUTICS DEPARTMENT
PJLCP, NAGPUR
Dr. Mrs. SUPARNA S BAKHLE
ASSOCIATE PROFESSOR
PHARMACEUTICS DEPARTMENT
PJLCP, NAGPUR
MIXING
•Mixing may be defined as a unit operation that tends to
result in a randomization of dissimilar particles within a
system.
2
•Mixing may be defined as a unit operation that tends to
result in a randomization of dissimilar particles within a
system.
2
TYPES OF MIXTURES
•Positive mixtures - Positive mixtures are formed from
materials such as gases or miscible liquids which mix
spontaneously and irreversibly by diffusion, and tend to
approach a perfect mix.
•Negative mixtures- With negative mixtures the
components will tend to separate out. If this occurs
quickly, then energy must be continuously input to keep
the components adequately dispersed, e.g. with a
suspension formulation, such as calamine lotion.
•Neutral mixtures - Neutral mixtures are said to be static in
behavior, i.e. the components have no tendency to mix
spontaneously or segregate spontaneously once work
has been input to mix them. Examples of this type of
mixture include mixed powders, pastes and ointments
3
•Positive mixtures - Positive mixtures are formed from
materials such as gases or miscible liquids which mix
spontaneously and irreversibly by diffusion, and tend to
approach a perfect mix.
•Negative mixtures- With negative mixtures the
components will tend to separate out. If this occurs
quickly, then energy must be continuously input to keep
the components adequately dispersed, e.g. with a
suspension formulation, such as calamine lotion.
•Neutral mixtures - Neutral mixtures are said to be static in
behavior, i.e. the components have no tendency to mix
spontaneously or segregate spontaneously once work
has been input to mix them. Examples of this type of
mixture include mixed powders, pastes and ointments
3
Application of mixing
•Mixing is one of the most common pharmaceutical operations.
It is involved in preparation of many types of formulations.
•Mixing of powders is done prior to filling in capsules, sachets
and as dry powder inhalers.
•Blending of powders is required in the preparation of talcum,
tooth powders etc.
•Dry mixing of materials is required for direct compression into
tablets.
•Mixing of miscible liquids is done to prepare linctuses
•Mixing of immiscible liquids is done to prepare emulsions.
•Mixing is needed to prepare semi-solid dosage forms such as
ointments, creams, gels etc.
•In preparing pastes and suspensions a dispersions of solid
particles in the dispersion medium is possible by proper mixing.
4
•Mixing is one of the most common pharmaceutical operations.
It is involved in preparation of many types of formulations.
•Mixing of powders is done prior to filling in capsules, sachets
and as dry powder inhalers.
•Blending of powders is required in the preparation of talcum,
tooth powders etc.
•Dry mixing of materials is required for direct compression into
tablets.
•Mixing of miscible liquids is done to prepare linctuses
•Mixing of immiscible liquids is done to prepare emulsions.
•Mixing is needed to prepare semi-solid dosage forms such as
ointments, creams, gels etc.
•In preparing pastes and suspensions a dispersions of solid
particles in the dispersion medium is possible by proper mixing.
4
OBJECTIVES OF MIXING
•Simple physical Mixture: This may be simply the
production of a blend of two or more miscible liquids or two
or more uniformly divided solids.
•Physical Change: Mixing may aim at producing a change
that is physical as distinct from chemical, for example the
solution of a soluble substance.
•Dispersion: This includes the dispersion of two immiscible
liquids to form an emulsion or the dispersion of a solid in a
liquid to give a suspension or paste.
•Promotion of Reaction: Mixing will usually encourage
(and control at the same time) a chemical reaction, so
ensuring uniform products.
5
•Simple physical Mixture: This may be simply the
production of a blend of two or more miscible liquids or two
or more uniformly divided solids.
•Physical Change: Mixing may aim at producing a change
that is physical as distinct from chemical, for example the
solution of a soluble substance.
•Dispersion: This includes the dispersion of two immiscible
liquids to form an emulsion or the dispersion of a solid in a
liquid to give a suspension or paste.
•Promotion of Reaction: Mixing will usually encourage
(and control at the same time) a chemical reaction, so
ensuring uniform products.
5
Diff. between liquid and solid mixing
Liquid Mixing Solid Mixing
Flow currents are responsible for
transporting unmixed material to the
mixing zone adjacent to impeller
Flow currents are not possible
Truly homogenous liquid phase can be
observed
Product often consists of 2 or more
easily identifiable phases
Small sample size is sufficient to study
degree of mixing
Large sample size is required
Mixing requires low power Mixing requires high power
6
Liquid Mixing Solid Mixing
Flow currents are responsible for
transporting unmixed material to the
mixing zone adjacent to impeller
Flow currents are not possible
Truly homogenous liquid phase can be
observed
Product often consists of 2 or more
easily identifiable phases
Small sample size is sufficient to study
degree of mixing
Large sample size is required
Mixing requires low power Mixing requires high power
6
Types of mixing
1.Solid-solid mixing
2.Liquid-liquid mixing
3.mixing of immiscible liquids
4.Solid-liquid mixing
5.Semi solid mixing
7
1.Solid-solid mixing
2.Liquid-liquid mixing
3.mixing of immiscible liquids
4.Solid-liquid mixing
5.Semi solid mixing
7
Solid-solid mixing
•This is the process in which two or more than two solid
substance are mixed in a mixer by continuous movement of
the particle.
•MECHANISM OF MIXING IN SOLIDS:
•convective mixing (macro mixing): In the case of convective
mixing material in the mixer is transported from one location
to another. Usually this type of mixing is applied for free-
flowing and coarse materials
•Shear mixing: Force of attraction are broken down so that
each particles moves on its own between region of different
composition.
•Diffusive mixing (micro mixing): Random motion of particles
within the powder bed thereby particle change their position
relative to one another
8
•This is the process in which two or more than two solid
substance are mixed in a mixer by continuous movement of
the particle.
•MECHANISM OF MIXING IN SOLIDS:
•convective mixing (macro mixing): In the case of convective
mixing material in the mixer is transported from one location
to another. Usually this type of mixing is applied for free-
flowing and coarse materials
•Shear mixing: Force of attraction are broken down so that
each particles moves on its own between region of different
composition.
•Diffusive mixing (micro mixing): Random motion of particles
within the powder bed thereby particle change their position
relative to one another
8
Degree of mixing
•The mixedness or goodness of mixing of the powder
system is important because mixing involves particles
with different properties and different ratios.
•A powder mixture can be visualized as shown in the
slide.
9
•The mixedness or goodness of mixing of the powder
system is important because mixing involves particles
with different properties and different ratios.
•A powder mixture can be visualized as shown in the
slide.
9
IDEAL MIXING OR PERFECT MIXING
•Ideal degree of mixing is represented by a chessboard
with black and white squares representing two
components (equal quantities).
•It indicates that each particle of one component is lying
adjacent to a particle of another component.
•Such an arrangement is practically impossible to achieve
in any mixer.
•A random mixture is the one in which probability of
finding the particle of one component at any point is
equal to the proportion of that component in the mixture
10
•Ideal degree of mixing is represented by a chessboard
with black and white squares representing two
components (equal quantities).
•It indicates that each particle of one component is lying
adjacent to a particle of another component.
•Such an arrangement is practically impossible to achieve
in any mixer.
•A random mixture is the one in which probability of
finding the particle of one component at any point is
equal to the proportion of that component in the mixture
10
DEGREE OF MIXING
11
11
Factors affecting powder mixing
•Particle size: It is easy to mix materials having the same
particle sizes. If there is variation in particle sizes,
separation may occur since the small particles move
downward through the spaces between the bigger
particles. As the particle size increases, flow properties of
the material increases which facilitates mixing.
•Particle shape: Particles should be spherical in shape
for uniform mixing. If there is irregular shape of the
particles in a material, then they become interconnected
in such a way that their separation is relatively difficult
after mixing than if the particle shape is regular.
12
•Particle size: It is easy to mix materials having the same
particle sizes. If there is variation in particle sizes,
separation may occur since the small particles move
downward through the spaces between the bigger
particles. As the particle size increases, flow properties of
the material increases which facilitates mixing.
•Particle shape: Particles should be spherical in shape
for uniform mixing. If there is irregular shape of the
particles in a material, then they become interconnected
in such a way that their separation is relatively difficult
after mixing than if the particle shape is regular.
12
Factors affecting powder mixing
•Particle charge: If the particle has some
electrostatic charge that cause attraction forces
between particles, then there are more
chances of segregation or separation.
•Nature of the particle: Particle hardness,
elasticity, porosity, texture are also the factors that
affect mixing phenomena greatly.
•Relative Density: For uniform mixing, the
particles of the materials to be mixed should have
the same density approximately. If the
components are of different density, the denser
material will sink through the lighter one and
demixing will result.
13
•Particle charge: If the particle has some
electrostatic charge that cause attraction forces
between particles, then there are more
chances of segregation or separation.
•Nature of the particle: Particle hardness,
elasticity, porosity, texture are also the factors that
affect mixing phenomena greatly.
•Relative Density: For uniform mixing, the
particles of the materials to be mixed should have
the same density approximately. If the
components are of different density, the denser
material will sink through the lighter one and
demixing will result.
13
Factors affecting powder mixing
•Proportion of materials: It is easy to mix
materials which are equal in proportion by weight
or volume (1:1). If there is a large difference in
the proportion of materials, then mixing is done in
the ascending order of their weights.
•Presence of Moisture: Moisture present in
particles heap also affects mixing phenomena.
For example mixing of dry clay is more rapid and
efficient than wet mixing of clay. In fact proper
mixing requires specific moisture content in bulk.
14
•Proportion of materials: It is easy to mix
materials which are equal in proportion by weight
or volume (1:1). If there is a large difference in
the proportion of materials, then mixing is done in
the ascending order of their weights.
•Presence of Moisture: Moisture present in
particles heap also affects mixing phenomena.
For example mixing of dry clay is more rapid and
efficient than wet mixing of clay. In fact proper
mixing requires specific moisture content in bulk.
14
Classification of mixers
15
Classification
of Mixers
Free Flowing
Solids
V Cone
Blender
Double Cone
Blender
Cohesive
Solids
Planetary
Mixer
Sigma
Blender
15
Classification
of Mixers
Free Flowing
Solids
V Cone
Blender
Double Cone
Blender
Cohesive
Solids
Planetary
Mixer
Sigma
Blender
16
Classification of
Mixers
Batch Mixer
Double Cone
Blender
Twin Shell
Blender
Ribbon Blender
Sigma Blender
Planetary Mixer
Continuous Mixer
Barrel Mixer Zig-Zag Mixer
Classification of
Mixers
Batch Mixer
Double Cone
Blender
Twin Shell
Blender
Ribbon Blender
Sigma Blender
Planetary Mixer
Continuous Mixer
Barrel Mixer Zig-Zag Mixer
Cylindrical blenders
17
17
Cylindrical blenders
•Tumblers or cylindrical blenders with no mixing blade are
meant for dry powders
•Equipment consists of a container of any geometric form.
Container is mounted on special roller so that it can be
rotated about any axis.
18
•Tumblers or cylindrical blenders with no mixing blade are
meant for dry powders
•Equipment consists of a container of any geometric form.
Container is mounted on special roller so that it can be
rotated about any axis.
18
DOUBLE CONE BLENDER:
•Principle: It consists of double cone mounted on a
rotating shaft.
•As the mixer rotates, the materials to be mixed undergo a
tumbling motion.
•Mixing takes place due to convective transport and
diffusion.
19
•Principle: It consists of double cone mounted on a
rotating shaft.
•As the mixer rotates, the materials to be mixed undergo a
tumbling motion.
•Mixing takes place due to convective transport and
diffusion.
19
20
Double Cone Blender
•Construction: It consists of a container in
the shape of a double cone mounted on a
rotating shaft.
•Material loading and emptying is done
through the same port.
•The rate of rotation should be optimum
depending upon the size, shape of the
tumbler and nature of the material to be
mixed.
•The rate of rotation commonly ranges from
30 -100 rpm.
21
•Construction: It consists of a container in
the shape of a double cone mounted on a
rotating shaft.
•Material loading and emptying is done
through the same port.
•The rate of rotation should be optimum
depending upon the size, shape of the
tumbler and nature of the material to be
mixed.
•The rate of rotation commonly ranges from
30 -100 rpm.
21
Double Cone Blender
•Working: The material to be mixed is
loaded approximately two-third of the
volume of the blender.
•The blender is allowed to rotate.
•The materials inside the mixer undergo a
tumbling motion.
•The particles of the materials are displaced
from one location to another to enable
mixing to occur by convection and diffusion.
22
•Working: The material to be mixed is
loaded approximately two-third of the
volume of the blender.
•The blender is allowed to rotate.
•The materials inside the mixer undergo a
tumbling motion.
•The particles of the materials are displaced
from one location to another to enable
mixing to occur by convection and diffusion.
22
Double Cone Blender
Uses:
•The mixer is good for mixing of free-flowing
granules/powders but poor for
cohesive/poorly flowing powders because
the shear forces generated are usually
insufficient to break up any aggregates.
•A common use is in the blending of
lubricants, glidants or disintegrants with
granules prior to tableting.
23
Uses:
•The mixer is good for mixing of free-flowing
granules/powders but poor for
cohesive/poorly flowing powders because
the shear forces generated are usually
insufficient to break up any aggregates.
•A common use is in the blending of
lubricants, glidants or disintegrants with
granules prior to tableting.
23
Double Cone Blender
Merits:
•The mixer is suitable for mixing of fragile granules as
there is minimum attrition
•It is available in large capacity
•It is easy to clean, load and unload
•It is easy to maintain
Demerits:
•It requires a high headspace for installation
•It is suitable only for mixing of free flowing and granular
materials
•It is not suitable for mixing of powders with large
differences in particle size distribution because not
enough shear is applied to the materials.
24
Merits:
•The mixer is suitable for mixing of fragile granules as
there is minimum attrition
•It is available in large capacity
•It is easy to clean, load and unload
•It is easy to maintain
Demerits:
•It requires a high headspace for installation
•It is suitable only for mixing of free flowing and granular
materials
•It is not suitable for mixing of powders with large
differences in particle size distribution because not
enough shear is applied to the materials.
24
V Cone Blender
25
25
V-cone blender
•It is V shaped and made up of stainless steel or
transparent plastic. Material is loaded through either of
shell hatches and emptying is normally done through an
apex port.
•The material is loaded approximately 50-60 % of the total
volume.
•Small models – 20 kg , rotate at 35 rpm Large models – 1
ton, rotate at 15 rpm.
•As the blender rotates , the material undergoes tumbling
motion. When V is inverted, the material splits into two
portions. This process of dividing and recombining
continuously yields ordered mixing by mechanical means
26
•It is V shaped and made up of stainless steel or
transparent plastic. Material is loaded through either of
shell hatches and emptying is normally done through an
apex port.
•The material is loaded approximately 50-60 % of the total
volume.
•Small models – 20 kg , rotate at 35 rpm Large models – 1
ton, rotate at 15 rpm.
•As the blender rotates , the material undergoes tumbling
motion. When V is inverted, the material splits into two
portions. This process of dividing and recombining
continuously yields ordered mixing by mechanical means
26
Advantages and Disadvantages
Advantages of V cone blender
•If fragile granules are to be blended, twin shell blender is
suitable because of minimum attrition.
•They handle large capacities.
•Easy to clean , load, and unload.
•This equipment requires minimum maintenance.
Disadvantages of V cone blender
•Twin shell blender needs high headspace for installation.
•It is not suitable for fine particulate system or ingredients
of large differences in the particle size distribution,
because not enough shear is applied.
•If powders are free flowing, serial dilution is required for
the addition of low dose active ingredients
27
Advantages of V cone blender
•If fragile granules are to be blended, twin shell blender is
suitable because of minimum attrition.
•They handle large capacities.
•Easy to clean , load, and unload.
•This equipment requires minimum maintenance.
Disadvantages of V cone blender
•Twin shell blender needs high headspace for installation.
•It is not suitable for fine particulate system or ingredients
of large differences in the particle size distribution,
because not enough shear is applied.
•If powders are free flowing, serial dilution is required for
the addition of low dose active ingredients
27
DOUBLE CONE AND TWIN SHELL BLENDER
WITH AGITATION MIXING BLADE
28
WITH AGITATION MIXING BLADE
28
DOUBLE CONE AND TWIN SHELL BLENDER WITH
AGITATION MIXING BLADE
•The double cone and v-cone blender can
be fitted with mixing blades for agitation.
•These blenders are same as double cone
and v-cone blender in terms of construction
and working with the added advantage of
the presence of agitator blade in them.
•Uses: These blenders are suitable for
mixing of not only dry powders/granules but
also for mixing of cohesive solids.
29
AGITATION MIXING BLADE
•The double cone and v-cone blender can
be fitted with mixing blades for agitation.
•These blenders are same as double cone
and v-cone blender in terms of construction
and working with the added advantage of
the presence of agitator blade in them.
•Uses: These blenders are suitable for
mixing of not only dry powders/granules but
also for mixing of cohesive solids.
29
DOUBLE CONE AND TWIN SHELL BLENDER WITH
AGITATION MIXING BLADE
•Merits:
•Attachments of agitator blades are
beneficial for both wet and dry mixing.
•Wide range of shearing force can be
applied with agitator bars permitting the
intimate mixing of very fine as well as
coarse powders.
•Serial dilution is not needed when
incorporating low-dose active ingredients.
30
AGITATION MIXING BLADE
•Merits:
•Attachments of agitator blades are
beneficial for both wet and dry mixing.
•Wide range of shearing force can be
applied with agitator bars permitting the
intimate mixing of very fine as well as
coarse powders.
•Serial dilution is not needed when
incorporating low-dose active ingredients.
30
•Demerits:
•Attrition is large, size reduction of friable
particles results.
•Cleaning may be a problem, because
agitator assembly must be removed and
the packing should be replaced for a
product change over.
•Potential packing (sealing) problems may
occur in these mixers.
31
•Attrition is large, size reduction of friable
particles results.
•Cleaning may be a problem, because
agitator assembly must be removed and
the packing should be replaced for a
product change over.
•Potential packing (sealing) problems may
occur in these mixers.
31
Ribbon blender
•Principle: Mechanism of mixing is shear. Shear is
transferred by moving blades. High shear rates
are effective in breaking lumps and aggregates.
Convective mixing also occurs as the powder bed
is lifted and allowed to cascade to the bottom of
the container
32
•Principle: Mechanism of mixing is shear. Shear is
transferred by moving blades. High shear rates
are effective in breaking lumps and aggregates.
Convective mixing also occurs as the powder bed
is lifted and allowed to cascade to the bottom of
the container
32
Ribbon
33
33
Ribbon Mixer
34
34
Ribbon Blender
Construction: It consists of horizontal
cylindrical trough usually open at the top
and fitted with helical blades.
• The blades are mounted on a shaft
through the long axis of the tank and are
often of both right and left-hand twist.
•The blades are connected to fixed speed
drive.
•The blender can be loaded by top loading
and emptying is done through bottom port.
35
Construction: It consists of horizontal
cylindrical trough usually open at the top
and fitted with helical blades.
• The blades are mounted on a shaft
through the long axis of the tank and are
often of both right and left-hand twist.
•The blades are connected to fixed speed
drive.
•The blender can be loaded by top loading
and emptying is done through bottom port.
35
Ribbon Blender
•Working: During mixing the blades rotate at fixed
speeds.
•One blade moves the solids slowly in one
direction.
• At the same time the other blade quickly turns
the solids in opposite direction.
•The powders are lifted and allowed to cascade to
the bottom of the container with a centrally
located screw.
•After blending, the blend is discharged from a
discharge valve located at the bottom of the
trough.
36
•Working: During mixing the blades rotate at fixed
speeds.
•One blade moves the solids slowly in one
direction.
• At the same time the other blade quickly turns
the solids in opposite direction.
•The powders are lifted and allowed to cascade to
the bottom of the container with a centrally
located screw.
•After blending, the blend is discharged from a
discharge valve located at the bottom of the
trough.
36
Ribbon Mixer
37
37
Ribbon Mixer
•For mixing finely divided solids, wet solid mass, sticky &
plastic solids. It is used for liquid-solid & solid-solid mixing
Advantages:
• High shear can be applied by using baffles, which bring
about a rubbing & break down aggregates.
Disadvantages:
•Shearing action is less than in planetary mixer.
•Dead spots are observed
•It is a poor mixer, because movement of particles is 2 –
dimensional
•Speed is fixed
38
•For mixing finely divided solids, wet solid mass, sticky &
plastic solids. It is used for liquid-solid & solid-solid mixing
Advantages:
• High shear can be applied by using baffles, which bring
about a rubbing & break down aggregates.
Disadvantages:
•Shearing action is less than in planetary mixer.
•Dead spots are observed
•It is a poor mixer, because movement of particles is 2 –
dimensional
•Speed is fixed
38
Sigma Blade Mixer
39
39
Sigma Blade Mixer
•Principle: This robust mixer will deal with
stiff pastes and ointments and depends for
its action on the close intermeshing of the
two blades which resemble the Greek
letter Ʃ in shape.
•The clearance between the blades and the
mixing trough is kept small by the shape.
•Inter meshing of sigma blades creates high
shear and kneading action.
40
•Principle: This robust mixer will deal with
stiff pastes and ointments and depends for
its action on the close intermeshing of the
two blades which resemble the Greek
letter Ʃ in shape.
•The clearance between the blades and the
mixing trough is kept small by the shape.
•Inter meshing of sigma blades creates high
shear and kneading action.
40
Sigma Blade Mixer
Construction: It consists of double trough
shaped stationary bowl.
Two sigma shaped blades are fitted
horizontally in each trough of the bowl.
These blades are connected to a fixed speed
drive.
Mixer is loaded from top and unloaded by
tilting the entire bowl.
41
Construction: It consists of double trough
shaped stationary bowl.
Two sigma shaped blades are fitted
horizontally in each trough of the bowl.
These blades are connected to a fixed speed
drive.
Mixer is loaded from top and unloaded by
tilting the entire bowl.
41
Sigma Blade Mixer
•Working: Powders are introduced from the top of
the trough.
•During blending, the two blades rotate at different
speeds, one usually about twice the speed of the
other, which allows movement of powder from
sides to centers.
•The material also moves top to downwards and
gets sheared between the blades and the wall of
the trough resulting in cascading action.
•The perforated blades helps to break lumps and
aggregates creating high shear forces.
•The final stage of mix represents an equilibrium
state.
42
•Working: Powders are introduced from the top of
the trough.
•During blending, the two blades rotate at different
speeds, one usually about twice the speed of the
other, which allows movement of powder from
sides to centers.
•The material also moves top to downwards and
gets sheared between the blades and the wall of
the trough resulting in cascading action.
•The perforated blades helps to break lumps and
aggregates creating high shear forces.
•The final stage of mix represents an equilibrium
state.
42
Sigma blade mixer
43
43
Sigma Blade Mixer
Uses: The mixer is used in the wet
granulation process in the manufacture of
tablets, pill masses and ointments.
It is primarily used for liquid – solid mixing,
although it can be used for solid – solid
mixing.
It is ideal for mixing, kneading of highly
viscous mass, sticky and dough like
products.
44
Uses: The mixer is used in the wet
granulation process in the manufacture of
tablets, pill masses and ointments.
It is primarily used for liquid – solid mixing,
although it can be used for solid – solid
mixing.
It is ideal for mixing, kneading of highly
viscous mass, sticky and dough like
products.
44
Sigma Blade Mixer
•Merits:
•Sigma blade mixer creates a minimum
dead space during mixing.
•It has close tolerances between the blades
and the sidewalls as well as bottom of the
mixer shell.
•Demerits:
•Sigma blade mixer works at a fixed speed.
45
•Merits:
•Sigma blade mixer creates a minimum
dead space during mixing.
•It has close tolerances between the blades
and the sidewalls as well as bottom of the
mixer shell.
•Demerits:
•Sigma blade mixer works at a fixed speed.
45
Planetary mixer
Principle
•Mechanism of mixing is shear. Shear is applied between
moving blade and stationary wall. Mixing arm moves
around its own axis and around the central axis so that it
reaches every spot of the vessel. The plates in the blades
are sloped so that powder makes an upward movement to
achieve tumbling action also.
Construction:
Consists of vertical cylinder shell which can be removed.
The blade is mounted from the top of the bowl. Mixing shaft
is driven by planetary gear and it is normally built with
variable speed drive.
46
Principle
•Mechanism of mixing is shear. Shear is applied between
moving blade and stationary wall. Mixing arm moves
around its own axis and around the central axis so that it
reaches every spot of the vessel. The plates in the blades
are sloped so that powder makes an upward movement to
achieve tumbling action also.
Construction:
Consists of vertical cylinder shell which can be removed.
The blade is mounted from the top of the bowl. Mixing shaft
is driven by planetary gear and it is normally built with
variable speed drive.
46
47
•Working: The mixing blade is set off centre and is carried
on a rotating arm. It therefore travels round the
circumference of the rotating bowl while simultaneously
rotating around its axis. This is therefore a double rotation
similar to that of a spinning planet around the sun-hence
the name. The blade tears the mass apart and shear is
applied between the moving blade and its stationary wall.
The plates in the blade are sloped so that the powder
makes an upward movement. Thus the tumbling motion is
also achieved. Since the speed of the blade can be
changed, initially the blade is allowed to move at slow
speed for pre-mixing and finally at increased speed for
active mixing. The mixer is designed so that the blade
covers all the volume of the mixer.
48
on a rotating arm. It therefore travels round the
circumference of the rotating bowl while simultaneously
rotating around its axis. This is therefore a double rotation
similar to that of a spinning planet around the sun-hence
the name. The blade tears the mass apart and shear is
applied between the moving blade and its stationary wall.
The plates in the blade are sloped so that the powder
makes an upward movement. Thus the tumbling motion is
also achieved. Since the speed of the blade can be
changed, initially the blade is allowed to move at slow
speed for pre-mixing and finally at increased speed for
active mixing. The mixer is designed so that the blade
covers all the volume of the mixer.
48
•Uses: Planetary mixer is a very efficient mixer and can
break down agglomerates rapidly producing precise
blends. Low speeds are used for dry blending and fast for
wet granulation.
•Merits:
•In this mixer, the speed of rotation can be varied at will. It
is more useful for wet granulation process as compared to
sigma blade and ribbon blender.
•Demerits:
•Mechanical heat is buildup within the powder mix.
•It requires high power.
•It has limited size and is useful for batch work only.
49
break down agglomerates rapidly producing precise
blends. Low speeds are used for dry blending and fast for
wet granulation.
•Merits:
•In this mixer, the speed of rotation can be varied at will. It
is more useful for wet granulation process as compared to
sigma blade and ribbon blender.
•Demerits:
•Mechanical heat is buildup within the powder mix.
•It requires high power.
•It has limited size and is useful for batch work only.
49
Planetary Mixer
50
50
MIXING OF MISCIBLE LIQUID AND
SUSPENSION
•Mobile liquids with a low viscosity are easily
mixed with each other.
•Similarly, solid particles are readily
suspended in mobile liquids, although the
particles are likely to settle rapidly when
mixing is discontinued.
•Viscous liquids are more difficult to stir and
mix, but they reduce the sedimentation rate
of suspended particles.
51
SUSPENSION
•Mobile liquids with a low viscosity are easily
mixed with each other.
•Similarly, solid particles are readily
suspended in mobile liquids, although the
particles are likely to settle rapidly when
mixing is discontinued.
•Viscous liquids are more difficult to stir and
mix, but they reduce the sedimentation rate
of suspended particles.
51
LIQUID MIXING
•The mechanism of mixing can be classified into four
classes .
•Bulk transport
•Turbulent
•Laminar mixing
•Molecular diffusion
52
•The mechanism of mixing can be classified into four
classes .
•Bulk transport
•Turbulent
•Laminar mixing
•Molecular diffusion
52
Mechanism of mixing in liquids
•Bulk Transport: Bulk transport involves the movement of
a relatively large amount of material from one position in
the mixing equipment to another.
•Turbulent Mixing: Turbulent mixing arises from the
haphazard movement of molecules when forced to move
in a turbulent manner. The constant changes in speed and
direction of movement means that induced turbulence is a
highly effective mechanism for mixing.
•Laminar Mixing: It is the mixing of two dissimilar liquids
through laminar flow, i.e., the applied shear stretches the
interphase between them. In this mechanism, layers fold
back upon themselves.
•Molecular Diffusion: It is the mixing at molecular level in
which molecules diffuse due to thermal motion.
53
•Bulk Transport: Bulk transport involves the movement of
a relatively large amount of material from one position in
the mixing equipment to another.
•Turbulent Mixing: Turbulent mixing arises from the
haphazard movement of molecules when forced to move
in a turbulent manner. The constant changes in speed and
direction of movement means that induced turbulence is a
highly effective mechanism for mixing.
•Laminar Mixing: It is the mixing of two dissimilar liquids
through laminar flow, i.e., the applied shear stretches the
interphase between them. In this mechanism, layers fold
back upon themselves.
•Molecular Diffusion: It is the mixing at molecular level in
which molecules diffuse due to thermal motion.
53
FACTORS INFLUENCING LIQUID MIXING
•Viscosity: Mixing is affected by viscosity of the
liquids. More the viscosity of the liquids more will
be the hindrance to proper mixing.
•Miscibility of the liquids: It is easier to mix a
mixture of miscible liquids than immiscible ones.
•Surface tension of liquids: surface tension of
liquid is also an important factor that effects mixing.
High surface tension reduces extent of mixing.
•Temperature: Temperature also affects mixing as
viscosity changes with the change in temperature.
54
•Viscosity: Mixing is affected by viscosity of the
liquids. More the viscosity of the liquids more will
be the hindrance to proper mixing.
•Miscibility of the liquids: It is easier to mix a
mixture of miscible liquids than immiscible ones.
•Surface tension of liquids: surface tension of
liquid is also an important factor that effects mixing.
High surface tension reduces extent of mixing.
•Temperature: Temperature also affects mixing as
viscosity changes with the change in temperature.
54
FACTORS INFLUENCING LIQUID MIXING
•Mixer volume: Mixer volume also affects
mixing phenomena. Mixer volume
should be such that over filling should not
be done as it decreases efficiency of mixing
and mostly material can’t be mixed
thoroughly.
•Mixing time: mixing time is also very
important for proper mixing. There is
always an optimum mixing time for specific
conditions in which mixing is taken place.
55
•Mixer volume: Mixer volume also affects
mixing phenomena. Mixer volume
should be such that over filling should not
be done as it decreases efficiency of mixing
and mostly material can’t be mixed
thoroughly.
•Mixing time: mixing time is also very
important for proper mixing. There is
always an optimum mixing time for specific
conditions in which mixing is taken place.
55
Mixing equipment
•A system for batch mixing commonly
consists of two primary components:
A tank or other container suitable to hold
the material being mixed and
A means of supplying energy to the system
so as to bring about rapid mixing.
56
•A system for batch mixing commonly
consists of two primary components:
A tank or other container suitable to hold
the material being mixed and
A means of supplying energy to the system
so as to bring about rapid mixing.
56
57
Mixing equipment
•The mixing device is called impeller, which
is mounted with the help of shaft. The shaft
is driven by a motor.
•Three main types of impeller are used
namely-
•Propeller
•Turbine and
•Paddles
58
•The mixing device is called impeller, which
is mounted with the help of shaft. The shaft
is driven by a motor.
•Three main types of impeller are used
namely-
•Propeller
•Turbine and
•Paddles
58
Flow pattern during mixing
•The movement of the liquid at any point in the vessel will
have three velocity components which are as follows:
•Radial component, acting in a direction vertical to the
impeller shaft. Excessive radial movement will take
materials to the container wall, whence they fall to the
bottom and may rotate as a mass beneath the impeller.
59
•The movement of the liquid at any point in the vessel will
have three velocity components which are as follows:
•Radial component, acting in a direction vertical to the
impeller shaft. Excessive radial movement will take
materials to the container wall, whence they fall to the
bottom and may rotate as a mass beneath the impeller.
59
Flow pattern during mixing
•A longitudinal or axial component acting parallel to the
impeller shaft. Adequate longitudinal pattern is best used
to generate strong vertical currents particularly when
suspending solids are present in a liquid.
60
•A longitudinal or axial component acting parallel to the
impeller shaft. Adequate longitudinal pattern is best used
to generate strong vertical currents particularly when
suspending solids are present in a liquid.
60
Flow pattern during mixing
•A tangential component acting in a direction
that is tangent to the circle of rotation round the
impeller shaft.
61
•A tangential component acting in a direction
that is tangent to the circle of rotation round the
impeller shaft.
61
Flow pattern during mixing
62
62
Mixing devices
63
63
Propellers
64
64
Propellers
•It consists of number of blades, generally 3
bladed design is most common for liquids.
•Blades may be right or left handed
depending upon the slant of their blades.
•Two or more propellers are used for deep
tank.
•Size of propeller is small and may
increased up to 0.5 metres depending upon
the size of the tank.
•Small size propellers can rotate up to 8000
rpm , produces axial and radial flow pattern
65
•It consists of number of blades, generally 3
bladed design is most common for liquids.
•Blades may be right or left handed
depending upon the slant of their blades.
•Two or more propellers are used for deep
tank.
•Size of propeller is small and may
increased up to 0.5 metres depending upon
the size of the tank.
•Small size propellers can rotate up to 8000
rpm , produces axial and radial flow pattern
65
Propellers
Uses:
The propeller will perform most mixing
duties with liquids when used correctly.
It is the best unit when strong vertical
currents are required as in suspension of
solids in a liquid.
It is not normally suitable when considerable
shear is needed as in emulsification.
66
Uses:
The propeller will perform most mixing
duties with liquids when used correctly.
It is the best unit when strong vertical
currents are required as in suspension of
solids in a liquid.
It is not normally suitable when considerable
shear is needed as in emulsification.
66
Propellers
Merits:
•Used when high mixing capacity is required.
•Effective for liquids which have maximum viscosity
of 2.0 pascals. sec or slurry up to 10% solids of
fine mesh size.
•Effective gas-liquid dispersion is possible at
laboratory scale.
Demerits:
•Propellers are not normally effective with liquids of
viscosity greater than 5 pascal.second, such as
glycerin castor oil, etc.,
67
Merits:
•Used when high mixing capacity is required.
•Effective for liquids which have maximum viscosity
of 2.0 pascals. sec or slurry up to 10% solids of
fine mesh size.
•Effective gas-liquid dispersion is possible at
laboratory scale.
Demerits:
•Propellers are not normally effective with liquids of
viscosity greater than 5 pascal.second, such as
glycerin castor oil, etc.,
67
68
Propeller
Mixing Process
Propeller
Mixing Process
Turbines
• A turbine mixer may be used for more
viscous liquids.
•A turbine consists of a circular disc to
which a number of short vertical blades are
attached.
•Blades may be straight or curved.
•The diameter of the turbine ranges from
30-50% of the diameter of the vessel.
•The turbines impeller is rotated at a lower
speed than the propellers (50-200rpm).
69
• A turbine mixer may be used for more
viscous liquids.
•A turbine consists of a circular disc to
which a number of short vertical blades are
attached.
•Blades may be straight or curved.
•The diameter of the turbine ranges from
30-50% of the diameter of the vessel.
•The turbines impeller is rotated at a lower
speed than the propellers (50-200rpm).
69
70
Flat blade turbine Pitched blade turbine
71
Most turbine impellers have flat blades and
cause the liquid to move rapidly in a radial
direction.
71
Most turbine impellers have flat blades and
cause the liquid to move rapidly in a radial
direction.
turbines
Uses:
Turbine mixers are satisfactory with
mobile liquids, but, because of the
greater shearing effects they can deal
with more viscous liquids than the
propeller mixers.
The turbines are particularly suitable
for preparing emulsions.
72
Uses:
Turbine mixers are satisfactory with
mobile liquids, but, because of the
greater shearing effects they can deal
with more viscous liquids than the
propeller mixers.
The turbines are particularly suitable
for preparing emulsions.
72
Turbines
73
Turbine
73
Turbine
Turbines
Merits:
•Turbines give greater shearing forces than propellers and
is suitable for emulsification.
•Effective for high viscous solutions.
•They can handle slurries with 60% solids.
•Turbines are suitable for liquids of large volume and high
viscosity, if the tank is baffled.
Demerits:
•The standard turbine mixer is less suitable than propellers
for suspending heavy solids because of absence of
vertical flow.
74
Merits:
•Turbines give greater shearing forces than propellers and
is suitable for emulsification.
•Effective for high viscous solutions.
•They can handle slurries with 60% solids.
•Turbines are suitable for liquids of large volume and high
viscosity, if the tank is baffled.
Demerits:
•The standard turbine mixer is less suitable than propellers
for suspending heavy solids because of absence of
vertical flow.
74
Paddles
•A paddle consists of a central hub with long flat
blades attached to it vertically.
•Two blades or four blades are common.
•Sometimes the blades are pitched and may be
dished or hemispherical in shape and have a
large surface area in relation to the tank in which
they are used.
•Paddles rotates at a low speed of 100 rpm.
•They push the liquid radially and tangentially
•In deep tanks several paddles are attached one
above the other on the same shaft.
75
•A paddle consists of a central hub with long flat
blades attached to it vertically.
•Two blades or four blades are common.
•Sometimes the blades are pitched and may be
dished or hemispherical in shape and have a
large surface area in relation to the tank in which
they are used.
•Paddles rotates at a low speed of 100 rpm.
•They push the liquid radially and tangentially
•In deep tanks several paddles are attached one
above the other on the same shaft.
75
76
Hemispherical Paddle
Flat Blade Paddle
Hemispherical Paddle
Flat Blade Paddle
Paddles
Uses: Paddles are used in the manufacture
of antacid suspensions, antidiarrheal
mixtures such as bismuth-kaolin.
Merits:
Vortex formation is not possible with
paddle impellers because of low speed
mixing.
Demerits:
Mixing of the suspension is poor therefore
baffled tanks are required.
77
Uses: Paddles are used in the manufacture
of antacid suspensions, antidiarrheal
mixtures such as bismuth-kaolin.
Merits:
Vortex formation is not possible with
paddle impellers because of low speed
mixing.
Demerits:
Mixing of the suspension is poor therefore
baffled tanks are required.
77
Vortex formation
•A strong circulatory flow pattern sometimes
manifests into formation of a vortex near
the impeller shaft .
78
•A strong circulatory flow pattern sometimes
manifests into formation of a vortex near
the impeller shaft .
78
VORTEX FORMATION
Vortex can be formed when:
Shaft is placed symmetrically in the tank.
Blades in the turbines are arranged
perpendicular to the central shaft.
At high impeller speeds
In unbaffled Containers
79
Vortex formation reduces mixing intensity by reducing
velocity of the impeller relative to the surrounding fluid
Vortex can be formed when:
Shaft is placed symmetrically in the tank.
Blades in the turbines are arranged
perpendicular to the central shaft.
At high impeller speeds
In unbaffled Containers
79
Vortex formation reduces mixing intensity by reducing
velocity of the impeller relative to the surrounding fluid
80
Prevention of Vortex Formation
Off-Centre Inclined
Side-entry
Push-pull
Baffled Container
Prevention of Vortex Formation
Off-Centre Inclined
Side-entry
Push-pull
Baffled Container
Mixing of immiscible Liquids
Mixing of immiscible liquids is carried in
pharmacy mainly in the manufacturing of
emulsions.
The equipment used for preparing the
emulsion is called emulsifier or
homogenizer.
Silverson mixer, colloid mill and rapisonic
homogenizers are suitable for
emulsification.
81
Mixing of immiscible liquids is carried in
pharmacy mainly in the manufacturing of
emulsions.
The equipment used for preparing the
emulsion is called emulsifier or
homogenizer.
Silverson mixer, colloid mill and rapisonic
homogenizers are suitable for
emulsification.
81
82
SILVERSON MIXER-HOMOGENIZER
SILVERSON MIXER-HOMOGENIZER
Silverson Mixer-Emulsifier
Principle:
•It produces intense shearing forces and
turbulence by use of high speed rotors.
•The emulsifier head is dipped in the mixture of
immiscible liquids.
•The liquid mixture is sucked inside the
emulsifying head due to suction and is dispersed
in the form of fine globules when acted upon by
the turbine blade and issued through the
perforations from the head.
83
Principle:
•It produces intense shearing forces and
turbulence by use of high speed rotors.
•The emulsifier head is dipped in the mixture of
immiscible liquids.
•The liquid mixture is sucked inside the
emulsifying head due to suction and is dispersed
in the form of fine globules when acted upon by
the turbine blade and issued through the
perforations from the head.
83
SILVERSON HOMOGENIZER
CONSTRUCTION:
•It consists of long supporting columns and a central
portion.
•The central portion consists of a shaft which is connected
to motor at one end and other to the emulsifying head.
•The emulsifying head carries turbine blades.
•The blades are surrounded by a mesh, which is further
enclosed by a cover having openings.
84
CONSTRUCTION:
•It consists of long supporting columns and a central
portion.
•The central portion consists of a shaft which is connected
to motor at one end and other to the emulsifying head.
•The emulsifying head carries turbine blades.
•The blades are surrounded by a mesh, which is further
enclosed by a cover having openings.
84
SILVERSON HOMOGENIZER
•Working: The emulsifier head is placed in the vessel
containing immiscible liquids (or coarse emulsion) in such
a way that it should get completely dipped in the liquid.
When the motor is started, the central rotating shaft
rotates the head, which in turn rotates turbine blade at a
very high speed. This creates a pressure difference. As a
result, liquids are sucked into the emulsifier head from the
center of the base and subjected to intense mixing action.
Centrifugal force expel the contents of the head with great
force through the mesh and onto the cover. As a result a
fine emulsion emerges through the openings of the outer
cover. The intake and expulsion of the mixture set up a
pattern of circulation to ensure rapid breakdown of the
bigger globules into smaller ones.
85
•Working: The emulsifier head is placed in the vessel
containing immiscible liquids (or coarse emulsion) in such
a way that it should get completely dipped in the liquid.
When the motor is started, the central rotating shaft
rotates the head, which in turn rotates turbine blade at a
very high speed. This creates a pressure difference. As a
result, liquids are sucked into the emulsifier head from the
center of the base and subjected to intense mixing action.
Centrifugal force expel the contents of the head with great
force through the mesh and onto the cover. As a result a
fine emulsion emerges through the openings of the outer
cover. The intake and expulsion of the mixture set up a
pattern of circulation to ensure rapid breakdown of the
bigger globules into smaller ones.
85
Silverson mixer -Emulsifier
Uses: Used for the preparation of emulsions and creams
of fine particle size.
Advantages: Silverson mixer is available in different sizes
to handle the liquids ranging from a few milliliters to
several thousand liters.
•Can be used for batch operations as well as for
continuous operations by incorporating into a pipeline,
through which the immiscible liquids flow.
Disadvantages: Occasionally, there is a chance is
clogging of pores of the mesh
86
Uses: Used for the preparation of emulsions and creams
of fine particle size.
Advantages: Silverson mixer is available in different sizes
to handle the liquids ranging from a few milliliters to
several thousand liters.
•Can be used for batch operations as well as for
continuous operations by incorporating into a pipeline,
through which the immiscible liquids flow.
Disadvantages: Occasionally, there is a chance is
clogging of pores of the mesh
86
Silverson Emulsifier
87
87
Semi-Solid Mixing
•Semi solids dosage forms include ointments, pastes,
creams, jellies, etc., while mixing such dosage forms, the
material must be brought to the agitator or the agitator
must move the material throughout the mixer.
The following mixers are helpful for mixing:
•Agitator mixers: e.g.:- Sigma mixers and Planetary mixer.
•Shear mixers: e.g.:- Triple roller mill and Colloidal mill.
88
•Semi solids dosage forms include ointments, pastes,
creams, jellies, etc., while mixing such dosage forms, the
material must be brought to the agitator or the agitator
must move the material throughout the mixer.
The following mixers are helpful for mixing:
•Agitator mixers: e.g.:- Sigma mixers and Planetary mixer.
•Shear mixers: e.g.:- Triple roller mill and Colloidal mill.
88
Mixing of semi-solids
•The problems that arise during the mixing of semisolids
(ointments and pastes) stem from the fact that, unlike
powders and liquids, semisolids will not flow easily. Material
that finds its way to 'dead' spots will remain there. For this
reason, suitable mixers must have rotating elements with
narrow clearances between themselves and the mixing
vessel wall and they must produce a high degree of shear
mixing, as diffusion and convection cannot occur. The forces
required for efficient mixing are high and consumption of
power is also high. Hence the equipment must be rugged
constructed to tolerate these forces. Some semisolids
exhibit dilatant property i.e., viscosity increases with
increase in shear rates. Therefore, mixing must be done at
lower speeds. The speed must be changed accordingly to
thixotropic, plastic and pseudo plastic materials.
89
•The problems that arise during the mixing of semisolids
(ointments and pastes) stem from the fact that, unlike
powders and liquids, semisolids will not flow easily. Material
that finds its way to 'dead' spots will remain there. For this
reason, suitable mixers must have rotating elements with
narrow clearances between themselves and the mixing
vessel wall and they must produce a high degree of shear
mixing, as diffusion and convection cannot occur. The forces
required for efficient mixing are high and consumption of
power is also high. Hence the equipment must be rugged
constructed to tolerate these forces. Some semisolids
exhibit dilatant property i.e., viscosity increases with
increase in shear rates. Therefore, mixing must be done at
lower speeds. The speed must be changed accordingly to
thixotropic, plastic and pseudo plastic materials.
89
Colloid Mill
90
90
Triple Roller Mill
91
91
Tags
Categories
GeneralDownload
Download Slideshow Get the original presentation fileQuick Actions
Statistics
- Views 3,154
- Slides 91
- Favorites 1
- Age 718 days
Related Slideshows
22
Pray For The Peace Of Jerusalem and You Will Prosper
RodolfoMoralesMarcuc
41 views
26
Don_t_Waste_Your_Life_God.....powerpoint
chalobrido8
45 views
31
VILLASUR_FACTORS_TO_CONSIDER_IN_PLATING_SALAD_10-13.pdf
JaiJai148317
40 views
14
Fertility awareness methods for women in the society
Isaiah47
38 views
35
Chapter 5 Arithmetic Functions Computer Organisation and Architecture
RitikSharma297999
37 views
5
syakira bhasa inggris (1) (1).pptx.......
ourcommunity56
39 views