Filtration: The separation of solid from a suspension in a liquid with the help of a porous medium which retains the solid and allows the liquid to pass through it is termed as filtration. Filtration involves the separation of solids from a liquid and is effected by passing the slurry through a porous medium. The pressure difference set up across the filter medium causes the fluid to flow through the small holes of a filter cloth or screen which blocks the passage of the larger solid particles. Filter aids are used as a pre coat to the filter medium before the slurry is filtered. This will prevent small particles from plugging the filter medium and also give a clearer filtrate.
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Distillation:-
- Distillation is an operation in which the components of a liquid mixture are separated using thermal energy.
- In this operation, liquid and vapour are involved. The vapour phase is created by supplying heat to the liquid phase.
-This unit operation is also termed as fractionation and with this technique it is possible to separate a liquid mixture into its components in almost pure forms.
- In this operation mass is transferred from both the phases to one another by vaporization from the liquid phase and by condensation from the vapour phase.
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Gas Absorption:
-This operation is used to separate the components of gas mixture .
-It is carried out for the recovery or the removal of a soluble components of a gas mixture depending upon the situation.
-Absorption is an operation in which a gas mixture is contacted with a liquid solvent for the purpose dissolved a definite component of the gas mixture in the liquid.
- Gas absorption is usually carried out in packed columns.
Example:
1) Absorption of ammonia from an air- ammonia mixture by water
2) Removal of hydrogen sulfide from naturally occurring hydrocarbon gases
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Drying: Drying is an operation in which the moisture of a substance is removed by means of thermal energy. In this operation, moisture is removed by circulating hot air or gas over the material in order to carry away the water vapour. In this operation, heat and mass transfer occur simultaneously. Heat is transferred from the gas phase to the solid phase and mass is transferred from the solid phase to the gas phase. Usually a solid or nearly solid materials are processed in dryer.