2. • Definition- Process of vaporizing large quantities of
volatile liquid to get concentrated product.
OR
• The removal of solvent from solution by boiling the liquor
in suitable vessel and withdrawing the vapour ,leaving
concentrated liquid residue in vessel.
• Application –
Manufacturing of bulk drugs.
Manufacturing of biological product.
Eg.. Enzymes,Insulin,harmones,Antibiotics….
Miscellaneous.
Eg.. Preparation of demineralized water.
3. Properties of evaporating liquids that influence
the process of evaporation
• Concentration: As the concentration increases, the
viscosity and density increases thereby the boiling point
of solution increases
• Foaming: Solutions like organic compounds tend to
foam during vaporization. The foam is carried away
along with vapor heavy entrainment.
• Scale: Solutions deposit scales on the heating surface .U
drastically decreases and leads to shut down of the
evaporators
4. • Temperature sensitivity: Pharmaceuticals products,
fine chemicals and foods are damaged when heated
to moderate temperatures for relatively short times.
So special techniques are employed to reduce
temperature of the liquid and time of heating,
• Material of construction: Evaporators are made of
some kind of steel. however many sols attack
ferrous metals and are contaminated by them .
Copper, nickel, stainless steels can also be used.
5. M = KS
p
( b – b)
Where,
M = mass of vapour formed per unit time
S = Surface area of the liquid exposed
p = atmospheric pressure
b = Max. V. pressure at the temp. of air
b = actual pressure
K = constant
Factors influencing Evaporation
6. • Temperature
• Vapour pressure
• Surface area
• Moisture content
• Type of product required
• Time of evaporation
• Film and deposits
• Economic factors
Factors influencing Evaporation
7. Classification
I) Evaporators with heating medium in jacket
E.g. = Steam jacketed kettle (Evaporating pan)
II) Vapour heated evaporators with tubular heating surfaces
A) Horizontal evaporators
E.g.= Horizontal tube evaporators
B) Vertical evaporators
i) Evaporators with short tubes
a) Single effect evaporators
E.g. = Short tube vertical evaporator, Short tube
vertical evaporator with propeller, Basket
type.
b) Multiple effect evaporator
E.g. = Triple effect evaporators
8. ii) Evaporators with long tube
a) Evaporators with natural circulation
E.g. = Rising film evaporators,
Falling film evaporator.
b) Evaporation with forced circulation
E.g. = Forced circulation evaporator.
