Evaporation
Contents
Introduction to
evaporation
Basic concept of phase equilibrium
Factors affecting
evaporation
Theory of
evaporation
Classification of
evaporators
Parts of an
evaporator
Construction &
working of evaporating still
Horizontal and
vertical tube evaporator
Multiple effect
evaporator
Learning
objectives
At the end of this
notes student will be able to:
• Outline the
industrial applications of evaporation
• Explain the
differences between evaporation and distillation
• Describe the
basic concepts of phase equilibrium
• Discuss the
factors affecting evaporation process
• Explain the
theory of evaporation process
• Describe the
parts of an evaporator
• Discuss the
construction and working process of evaporating still
• Explain the
process of horizontal and vertical tube evaporator
• Discuss the
construction and working process of multiple effect evaporator
• Recommend
suitable evaporator for the evaporation process
EVAPORATION
• Evaporation is
nothing but a thermal separation process.
• Theoretically,
evaporation means simply vaporization from the surface of a liquid.
• Vaporization of
a liquid below its boiling point is called evaporation.
Thus, no boiling
occurs and the rate of vaporization depends on the diffusion of
vapour through the boundary layers above the liquid.
Evaporation is a
type of phase transition; it is the process by which molecules in a
liquid state (e.g. water) spontaneously become gaseous (e.g. water
vapour).
Evaporation is a
unit operation of vaporizing large quantities of volatile liquid to
get a concentrated product
Evaporation
v/s Distillation
Evaporation
Vaporization takes
place below the boiling point
Takes only from the
surface of the liquid
There is no bubble
formation in evaporation
Not necessarily a
separation or purification technique. Vaporisation occurs rapidly
Distillation
Vaporization takes
place at the boiling point
Takes place from
whole of the liquid
There is bubble
formation
It is a separation
or purifying technique. It is a slow process
Drying
v/s Evaporation
Drying
It refers to the
removal of relatively small amounts of water from solid or nearly
solid material
In most cases drying
involves the removal of water at temperatures below its boiling point
Evaporation
It refers to the
removal of relatively large amounts of water from solutions
Removal of water by
boiling a solution- (wherever removing water is necessary)
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