What is Unit Operation?

Heat Exchanger

Have you ever wondered how does your air conditioner or your refrigerator in your house works? The cooling mechanism in your household machinery is achieved by a simple unit operation device such as the HEAT EXCHANGER!



So what is Unit Operation?

Firstly, unit operation is the operation that involves basic physical operations of chemical engineering in a chemical process plant, that is distillation, fluid transportation, heat and mass transfer, evaporation, extraction, drying, crystallization, filtration, mixing, size separation, crushing and grinding, and conveying.

Distillation is a unit operation that is used to purify or separate alcohol in the brewery industry.

The same distillation separates the hydrocarbon in a petroleum industries.

Flow of liquid hydrocarbon in a petroleum refinery and flow of milk in a daily plant for the solidification in spray dryer.

What are the many different Unit Operations?

Crystallization

1. Crystallization: The removal of a 
solute such as a salt from solution by precipitation in the industries for large scale operations, electrostatic precipitation is operated for this concept.

2. Fluid Flow: Concerns the principle that determine the flow or transformation of fluids from one point to another. The fluid can be a liquid or a gas. (Bernoullie's equation)

3. Heat Transfer: Deals with principles that govern accumulation and transfer of heat and energy from one place to another. The three concepts followed here are conduction, convection and radiation.

4. Evaporation: A special case of heat transfer which deals with the evaporation of volatile solvent such as waste from a non-volatile solute such as salt or any other material in the solution. Example: The evaporation of trichloro-ethylene a cleaning agent in the automobile service industry and acetone in the case of glassware in a chemical process industries follow this unit operations.

5. Drying: An operation in which volatile liquids (usually water) are removed from solid material.

6. Distillation: An operation where a components of the liquid mixture are separated by boiling because of their difference in vapour pressure.

7. Absorption: A process whereby a component is removed from gas mixture by treatment with liquid.

8. Liquid-Liquid Extraction: A process in which a solute in a liquid solution is removed by contact with another liquid solvent that is relatively irreversible with solution.

9. Liquid-Solid Leaching: It involves treating a finely divided solid with a liquid that dissolves and removes a solute contain in the solid.

10. Mechanical physical separation: This involves separation of solids, liquids or gases by mechanical means such as filtration, settling, size reduction which are classified as separate unit operations.    

The outline of unit operation defines the settling tanks for sedimentation, filter press for separations, pressurized spheres for ammonia storage, palletising for fertilizer compounds, pneumatic conveyors for cement industry, bucket wheel  elevators for thermal power stations and belt conveyors for core industries and many more in operation.