Unit operations are the physical steps needed to convert raw materials into products. In chemical engineering, unit operations encompass all physical steps needed right from preparation of reactant, the reactions and transfers of energy in the reactor, product isolation and purification to the handling of unreacted chemicals, by-products and waste materials.
In chemical engineering, there are 4 unit operations: fluid mechanics, heat transfer, mass transfer and solid particulates operations. Let’s discuss each of these unit operations.
o Fluid mechanics
Fluid mechanics is the study of behavior and properties of fluids. Fluid mechanics is a crucial line of unit operations, considering that most of the chemical industry processes are done in total or partial liquid phase. Fluid mechanics is divided into two branches:
Fluid statics- This is the study of the behavior of fluids at rest. If the fluid is gas, the study is called pneumatics, while if the fluid is a liquid, it is called hydrostatics.
Fluid dynamic or fluid flow- This is the study of fluids in partial or full motion. Here the flow can be parallel to the axis of the pipe; laminar flow or not parallel to the axis; turbulent flow.
o Heat transfer
This is the exchange of heat between hot and cold bodies. Since most chemical processes absorb or produce heat, these are also essential unit operations in chemical engineering. The modes of heat transfer common in many processes are:
Conduction- Heat transfer by means of molecular excitement rather than the bulk movement of the material.
Convection- Heat transfer through liquids and gases utilizing movement of the matter.
Radiation- Heat transfer through empty space from one body to another.
o Mass transfer
This is the transfer of a component in a mixture from a high concentration region to a region of low concentration. Since these operations determine the rate of chemical reactions, they are crucial in chemical engineering. These operations also form the basis of separation or isolation of substances in a mixture.
o Solid particulate operations
Solids are also an essential part of chemical processes. Unlike fluids, solids behaviors such as mixing are more complex, so they need special treatment. This category of unit operations deals with solid size reduction, solid settling and solid separation techniques.
In conclusion, we can say that considering the complexity of modern chemical manufacturing processes, unit operations are the heart of chemical engineering. All these activities must be well thought for and executed for any chemical manufacturing process to be successful.