Miscellaneous Miscellaneous ProcessProcess

By: Dr. Tahseen By: Dr. Tahseen IsmailIsmail

Spray DryingSpray Drying Spray drying is one of the methods of Spray drying is one of the methods of

desiccation by which solutions or slurries are desiccation by which solutions or slurries are dried. dried.

The apparatus used for this purpose is known as The apparatus used for this purpose is known as spray drier. These driers consist of a hot air spray drier. These driers consist of a hot air chamber into which liquid to be dried is fed from chamber into which liquid to be dried is fed from the top and hot air is supplied from the base.the top and hot air is supplied from the base.

The spraying of the liquid is done either by The spraying of the liquid is done either by pressure jets. By the high current of hot air the pressure jets. By the high current of hot air the liquid is sprayed liquid is sprayed

in the form of a mist, the droplets of which are in the form of a mist, the droplets of which are readily evaporated and the dried particles fall to readily evaporated and the dried particles fall to the bottom of the chamber from where they are the bottom of the chamber from where they are collected. collected.

The exhausted air leaves the chamber through The exhausted air leaves the chamber through the air outlet.the air outlet.

Different types of spray driers are Different types of spray driers are available with various modifications. available with various modifications. In some forms of spray driers the In some forms of spray driers the liquid to be dried and hot air enters liquid to be dried and hot air enters from the top of the chamber and in from the top of the chamber and in others from the bottom. Still in other others from the bottom. Still in other types liquid is fed from the top and types liquid is fed from the top and hot air from the bottomhot air from the bottom

ApplicationsApplications

1. These driers are very useful because 1. These driers are very useful because the drying is very rapid as large surface of the drying is very rapid as large surface of liquid is exposed to hot air and liquid is exposed to hot air and temperature required for drying is also temperature required for drying is also low. Therefore heat sensitive products can low. Therefore heat sensitive products can be dried conveniently.be dried conveniently.

2. Spray drying is used for drying blood 2. Spray drying is used for drying blood plasma, milk and enzyme preparations plasma, milk and enzyme preparations such as pancreatin and pepsin.such as pancreatin and pepsin.

3. Spray driers can be designed for drying 3. Spray driers can be designed for drying under sterile conditions.under sterile conditions.

4. Solid and liquid particles can be 4. Solid and liquid particles can be encapsulated by employing spray drying.encapsulated by employing spray drying.

LevigationLevigation

The process of levigations is also known The process of levigations is also known as wet grinding. In this method the as wet grinding. In this method the particle size of a substance is reduced to particle size of a substance is reduced to fine state of subdivision by triturating fine state of subdivision by triturating the substance with a few drops of liquids the substance with a few drops of liquids to which it is insoluble, in a glass mortar to which it is insoluble, in a glass mortar with the pestle or on a slab with with the pestle or on a slab with spatula .The most commonly used spatula .The most commonly used levigating agents includes are oils, levigating agents includes are oils, water, alcohols and glycerin.water, alcohols and glycerin.

Uses of levigationUses of levigation

Can be use to incorporate solid Can be use to incorporate solid substances into:substances into:

dermatological preparationsdermatological preparations

ophthalmic ointments.ophthalmic ointments.

suspensionssuspensions

Pulverization by Pulverization by InterventionIntervention

This is a process by which the solid This is a process by which the solid substances are reduced to a fine powder by substances are reduced to a fine powder by mean of triturating the solid using suitable mean of triturating the solid using suitable solvent which can bee easily removed by the solvent which can bee easily removed by the end of process.end of process.

Camphor is triturated with few drop of Camphor is triturated with few drop of alcohols, ether or chloroform it can be alcohols, ether or chloroform it can be powdered easily. The solvent added evaporate powdered easily. The solvent added evaporate quickly leaving behind fine sub-divided quickly leaving behind fine sub-divided particles of camphor.particles of camphor.

Similarly iodine crystals may be powdered Similarly iodine crystals may be powdered with the help of small quantiy of ether. with the help of small quantiy of ether.

Elutriation: Elutriation:

Definition:Definition: “Elutriation is the process in which the “Elutriation is the process in which the particles of the fluid move in a direction opposite to particles of the fluid move in a direction opposite to that of the sedimentation. (Downward movement)”that of the sedimentation. (Downward movement)”

Explanation:Explanation: In gravitational sedimentation the In gravitational sedimentation the particles will move vertically downward while the particles will move vertically downward while the fluid travels vertically upward. fluid travels vertically upward.

If the velocity of the fluid is less then the setting If the velocity of the fluid is less then the setting velocity of the particles, then the particles will velocity of the particles, then the particles will move downward against the stream of fluid. If the move downward against the stream of fluid. If the setting velocity of particles is less then the velocity setting velocity of particles is less then the velocity fluid, the particles will move upward. fluid, the particles will move upward.

In other words small size particles will In other words small size particles will move upward while the large size move upward while the large size particles will move downward. particles will move downward.

So Elutriation is the process of So Elutriation is the process of separation of fine particles from course separation of fine particles from course particles. The particles size can also be particles. The particles size can also be measured by this process. measured by this process.

Apparatus used for Apparatus used for ElutriationElutriation

The apparatus used for Elutriation The apparatus used for Elutriation process is called as Elutriator. process is called as Elutriator.

They are of two types:They are of two types: Gravitational ElutriationGravitational Elutriation Centrifugal ElutriationCentrifugal Elutriation

Gravitational ElutriationGravitational Elutriation

1- Gravitational Elutriation:1- Gravitational Elutriation: In gravitational Elutriation the fluid In gravitational Elutriation the fluid

particles move downward due to particles move downward due to sedimentation (force of gravity) while the sedimentation (force of gravity) while the lighter particles remain upward. lighter particles remain upward.

Centrifugal Elutriation:Centrifugal Elutriation:

Centrifugal Elutriation causes the fluid Centrifugal Elutriation causes the fluid stream to rotate under high centrifugal stream to rotate under high centrifugal force to suspend the particles. These force to suspend the particles. These particles which are too large to rotate particles which are too large to rotate with direction of flow of fluid, separates with direction of flow of fluid, separates out on the wall of the elutriator. However out on the wall of the elutriator. However the fine particles move easily with the the fine particles move easily with the stream of fluid.stream of fluid.

Uses of ElutriationUses of Elutriation

Heavy and light Kaolin can be separated Heavy and light Kaolin can be separated by this process, because the particles of by this process, because the particles of heavy Kaolin move downward and those heavy Kaolin move downward and those of the light Kaolin move upwardof the light Kaolin move upward. .

DECANTATIONDECANTATION Decantation is a process for the separation of Decantation is a process for the separation of

mixtures. mixtures.

MethodMethod:: Method consists of allowing the slurry to stand in a Method consists of allowing the slurry to stand in a

suitable vessel until the solids either settle down at suitable vessel until the solids either settle down at the bottom. Now carefully pouring a solution from a the bottom. Now carefully pouring a solution from a container in order to leave the precipitate (sediment) container in order to leave the precipitate (sediment) in the bottom of the original container. Usually a in the bottom of the original container. Usually a small amount of solution must be left in the small amount of solution must be left in the container, and care must be taken to prevent a small container, and care must be taken to prevent a small amount of precipitate from flowing with the solution amount of precipitate from flowing with the solution out of the container. It is generally used to separate a out of the container. It is generally used to separate a liquid from an insoluble solid (e.g. in red wine, where liquid from an insoluble solid (e.g. in red wine, where the wine is decanted from the potassium bi tartrate the wine is decanted from the potassium bi tartrate crystals).crystals).

Separation of liquid from any other Separation of liquid from any other immiscible liquid can also be done by immiscible liquid can also be done by decantation .For example,decantation .For example,

the oil and water extracted from the oil and water extracted from olives may be decanted to obtain the olives may be decanted to obtain the olive oil. olive oil.

A mixture of kerosene and water can A mixture of kerosene and water can also be separated through also be separated through decantationdecantation

CENTRIFUGATIONCENTRIFUGATION Centrifugation is a process that involves the use of Centrifugation is a process that involves the use of

the centrifugal force for the separation of mixtures, the centrifugal force for the separation of mixtures, used in industry and in laboratory settings.used in industry and in laboratory settings.

More-dense components of the mixture migrate More-dense components of the mixture migrate away from the axis of the centrifuge, while less-away from the axis of the centrifuge, while less-dense components of the mixture migrate towards dense components of the mixture migrate towards the axis. the axis.

The effective gravitational force on a test tube may The effective gravitational force on a test tube may be increased so as to more rapidly and completely be increased so as to more rapidly and completely cause the precipitate ("pellet") to gather on the cause the precipitate ("pellet") to gather on the bottom of the tube. The remaining solution is bottom of the tube. The remaining solution is properly called the "supernate" or "supernatant properly called the "supernate" or "supernatant liquid". liquid".

The supernatant liquid is then either quickly The supernatant liquid is then either quickly decanted from the tube without disturbing the decanted from the tube without disturbing the precipitate, or withdrawn with a Pasteur pipette. precipitate, or withdrawn with a Pasteur pipette.

The rate of centrifugation is specified by The rate of centrifugation is specified by the acceleration applied to the sample, the acceleration applied to the sample, typically measured in revolutions per typically measured in revolutions per minute (RPM).minute (RPM).

The particles' settling velocity in The particles' settling velocity in centrifugation is a function of theircentrifugation is a function of their

size and shape, size and shape, centrifugal acceleration, centrifugal acceleration, the volume fraction of solids present, the volume fraction of solids present, the density difference between the the density difference between the

particle and the liquid, particle and the liquid, viscosity.viscosity.

VAPORIZATIONVAPORIZATION

VaporizationVaporization of an element or compound is a phase of an element or compound is a phase transition from the liquid or solid phase to gas phase.transition from the liquid or solid phase to gas phase.

There are three types of vaporization: There are three types of vaporization: evaporation, evaporation, boiling and boiling and sublimation.sublimation. EvaporationEvaporation is a phase transition from the liquid phase to is a phase transition from the liquid phase to

gas phase that occurs at temperatures below the boiling gas phase that occurs at temperatures below the boiling temperature at a given pressure. Note: evaporation usually temperature at a given pressure. Note: evaporation usually occurs on the surface.occurs on the surface.

BoilingBoiling is a phase transition from the liquid phase to gas is a phase transition from the liquid phase to gas phase that occurs at or above the temperature the boiling phase that occurs at or above the temperature the boiling temperature. temperature.

Note: boiling occurs below the surfaceNote: boiling occurs below the surface..