This presentation helps to understand basic knowledge of unit operations.

1. PROCESS ENGINEERING
UNIT OPERATIONS
&
UNIT PROCESS
Presented by:
Neeraj Kumar Rai

2. UNIT OPERATIONS
 Unit operations involve a physical change or
chemical transformation such as separation,
crystallization, evaporation, filtration,
polymerization, isomerisation etc.
 A unit operation is defined as a process which
does not involve any chemical reaction. Unit
operations only deal with physical changes of
the materials involved in the process. They are
equipments which cause the materials to
undergo physical changes.

3. UNIT OPERATIONS
 The physical changes are carried out for variety of purposes.
Generally unit operations steps are carried out before
subjecting the materials to chemical reactions so that
chemical reactions happen smoothly.
 The physical changes can imply phase changes such as;
evaporation, condensation, crystallization etc. Thus
Distillation is a unit operation step because condensation
and evaporation happens inside the column. Evaporators,
and crystallisers are also unit operations equipment.
 Unit operation equipments are also responsible for
mechanical operations which involves size reduction,
physical separations, mixing, and grinding. The mass transfer,
heat transfer process all may happen together. Chemical
reaction doesn’t happen.

4. History
 Arthur Dehon Little developed the concept of
"unit operations" to explain industrial chemistry
processes in 1916. In 1923, William H.
Walker, Warren K. Lewis and William H.
McAdams wrote the book The Principles of
Chemical Engineering and explained that the
variety of chemical industries have processes
which follow the same physical laws.
 The concept of unit processes was introduced in
1923 by P.H. Groggin.

5. UNIT OPERATIONS
Chemical engineering unit operations consist of five classes
 Fluid flow processes, including fluids transportation, filtration, and solids
fluidization.
 Heat transfer processes, including evaporation and heat exchange.
 Mass transfer processes, including gas
absorption, distillation, extraction, adsorption, and drying.
 Thermodynamic processes, including gas liquefaction, and refrigeration.
 Mechanical processes, including solids transportation, crushing and
pulverization, and screening and sieving.
 Chemical engineering unit operations also fall in the following categories
which involve elements from more than one class:
 Combination (mixing)
 Separation (distillation, crystallization)
 Reaction (chemical reaction)

6. UNIT OPERATIONS
 The unit operations are classified in the following
manner:
 Fluid flow operations: Pumping, compression, and
fluidisation.
 Mechanical operations: Size reduction, size
enlargement, mixing, agitation, blending, filtration,
classification-separation, etc.
 Mass transfer: Distillation, evaporation, crystallization,
leaching, absorption, adsorption, extraction, etc.
 Heat transfer: When materials are handled the heat
transfer can take place by any fundamental mechanism;
conduction, convection, or radiation. Usually two
fundamental mechanisms occur simultaneously.

7. UNIT PROCESS
 A chemical reactor is an equipment which falls
under the category of unit processes. Chemical
change takes place inside the equipment wherein
the chemical structure of the material changes
and it transforms and forms an entirely new
material.
 All kinds of chemical reactions carried out in
industrial equipments comes under this category.
Some examples of such chemical reactions are;
sulphonation, nitration, halogenation, alkylation,
hydrolysis, hydrogenation, polymerization,
oxidation, reduction, etc.

8. Discussion of different unit
operations
 Material handling, transportation / Fluid flow process
Pumping
Compression
fluidization
 Mechanical unit operations
Size reduction
Size enlargement
Mixing, agitation, blending, etc
 Mass transfer operations
Evaporation
Distillation
Absorption
Extraction
leaching.
 Heat transfer operations
conduction
convection
radiation