Unit operation and Unit Process | Difference between unit operation and unit process

Chemical engineering as a vast subject and if you are an engineering student, you will encounter various concepts. There are some terms that are considered basic and one should know them at least. The first thing that will encounter you if you start studying chemical engineering is what is unit operation and unit process.

Unit Operation And Unit Process
Unit operation and unit process | Difference between unit operation and unit process

Chemical engineering is all about chemical reactions and elements, factors, and optimization of those to understand the mechanics of chemical reactions and production products. The combination of both unit operation and the process is called the manufacturing process or chemical process.

Today, in this article, we will learn what is unit operation and unit process with examples that will clear all your doubts. We will also see the difference between unit operation and unit process which is considered as the most basic question that fresher chemical engineers faced on-campus interviews or open interviews. So without wasting more time, let’s jump into the article and learn in detail.

Unit Operation

Unit operation is a basic step in a process that involves physical change or chemical transformation during the process like polymerization separation, evaporation crystallization, filtration, isomerization, and other reactions. 

What Is Unit Process

Example of Unit operation

Example 1 – Distillation of Methylene Di Chloride with water

Explanation – In a process, the separation of Methylene Di Chloride with water using a liquid-liquid separation technique can be called as a unit operation.|
Explanation – In the above process, only separation is taking place which will be done base on density difference. This is a physical change and no chemical reaction taking place, hence this process is considered as unit operation.

Example 2 – Distillation of acetone and water

Explanation – The distillation of acetone from the water is an example of unit operation. In the distillation process, acetone is separated and that is due to boiling point difference or volatility of the components. This is also a physical change and no chemical reaction is carried out. Hence distillation is a unit operation.

Classification of Unit Operation

Now we had seen the definition of unit operation and hereby learned what is unit operation. There are 4 classifications of unit operation, classification of unit operation are listed below.

  1. Material handling, transportation / Fluid flow process
  2. Mechanical unit operations
    Size reduction
    Size enlargement
    Mixing, agitation, blending, etc
  3. Mass transfer operations
  4. Heat transfer operations

We recommend you to read When vacuum distillation is selected – Purpose of vacuum distillation

Unit Process

The unit process is a process in which chemical changes take place to the material present in the reaction and result in the chemical reaction is known as the Unit process. This basically consists of a reaction between two or more chemical which results in another chemical and can also be defined as a unit process. Sulphonation, nitration, oxidation, halogenation, and many more.

Example of Unit process

Example 1 – Electrolysis of sodium chloride solution

Electrolysis Of Sodium Chloride Solution

As I currently work in a Chlor Alkali industry where we do electrolysis of sodium chlorine solution, we will take this as an example of a Unit process.

Explanation – Here, electrolysis of NaCl is being done and the concentration of sodium chloride is taken as 305 (around) GPL (gram per liter) concentration is feed to electrolysis cell in which electricity is passed and sodium hydroxide is produced. In this reaction, a decomposition reaction takes place hence, this is a unit operation. If you are interested, you can read Fundamentals of Electrolysis

Example 2 – Production of Hydrogen

Steam Methane Reforming Reaction

Hydrogen is produced using very popular method i.e. Steam-methane reforming reaction. In this method, methane reacts with steam at a pressure under 3–25 bar pressure in the presence of a Nickel catalyst at about 750 to produce hydrogen.

In this Steam-methane reforming reaction, chemical reaction under pressure and temperature is being conducted to react Methane with steam and generate Hydrogen. As here the reaction is begin conducted, this process comes under unit process.

Manufacturing process | What is Manufacturing process | What is chemical Process

The manufacturing process consists of a combination of various unit operations and unit processes which being conducted considering factors like optimization, design of equipment and selection of equipment, use of suitable utilities, and many more to make product is known as the Manufacturing process/chemical process.

Example Manufacturing process of cement

Cement is considered as a product which is a result of unit operation and unit process. There are various unit operations and unit processes are involved in the manufacturing process of cement. We will not go in-depth into the manufacturing process and will consider the relevant things only. For the manufacturing process of cement. The main raw material of cement is limestone which is present in the hard solid rock form. It is crushed into a fine powder using a jaw crusher. Using Jaw crusher, only physical changes will be conducted hence it is a unit operation. In the chemical process, limestone is heated and decomposes into lime and carbon dioxide is released which is a unit process.

Difference between unit operation and unit process

Unit OperationUnit Process
Process in which chemical changes takes place are considered as a unit process.Process in which chemical changes takes place are considered as unit process.
Mixing, blending, crushing distillation, etc are considered as unit operationsBromination, halogenation, sulphonation, etc are called unit process

FAQ (Unit process and unit operation)

1. Is distillation unit process or unit operation?

Ans – Distillation is a unit operation as there is not chemical reaction taking place and only physical separation takes place. Hence, the answer to the question Is distillation a unit operation? is Yes, distillation is a unit operation.

2. What is unit process example?

Ans – Process in which chemical reaction takes place such as nitration, sulphonation, chlorination and many more are unit process example.

3. What is unit operation in food industry?

Ans – In the food process industry, unit operations such as cleaning, mixing, separation, and filtration are used.

4. is filtration a physical or chemical change?

Ans – Filtration is a unit operation as only separation takes place which is a physical change. Hence filtration is a physical change.

Wrapping Up

This was the detailed tutorial on the unit operation and unit process and with respect to that, we had also covered the difference between unit operation and unit process with examples. If you have any doubts related to the topic then drop your question in the comment section, we will help you and explain to you in detail. Till then if you are a chemical engineer professional or a chemical engineering student then do check out the chemical engineering article. We also write Industrial safety articles like Safety Abbreviation List and many more, so in case you have an interest in workplace safety then do read that also.

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Me - Founder of Chemical Tweak - A Chemical Engineer by profession and a part-time self-trained technology blogger.

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