Evaporation

1. RJSPM
RAJMATA JIJAU SHIKSHAN PRASARAK MANDAL’S
COLLEGE OF PHARMACY
DUDULGAON, PUNE
Savitribai Phule Pune University
B.PHARM
Semester- III
By
Ms . Priyanka Bagade
Assistant Professor
Dept. of Pharmaceutics
EVAPORATION

2. CONTENT
1. Objectives,
2. Applications
3. Factors Influencing Evaporation,
4. Differences Between Evaporation And Other Heat Process.
5. Principles, Construction, Working, Uses, Merits And Demerits :
• Steam Jacketed Kettle,
• Horizontal Tube Evaporator,
• Climbing Film Evaporator,
• Forced Circulation Evaporator,
• Multiple Effect Evaporator Economy Of Multiple Effect Evaporator.
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3. UNIT OUTCOMES
 Evaporation
 Evaporator
 Economy of an evaporator
 Tripal Evapotar
 Jacket
2

4. DEFINATION
Evaporation is a process of vaporizing large quantities of volatile liquid to get
a concentrated product.
Equipment's used for evaporation are known as evaporators.
Heat is supplied to the evaporator which transmit it to the evaporating liquid
so as to provide latent heat of vaporization.
Steam is the heating source
Evaporation is surface phenomenon i.e. mass transfer takes place from the
surface
Evaporation is practically defined as the removal of solvent from the solution
by boiling the liquor in a suitable vessel and withdrawing the vapor leaving a
concentrated liquid reside in the vessel. 3

5. OBJECTIVES
It reduces the bulk and weight of the fluids thus allowing efficient transportation of
important products and storage of the solid.
It efficiently removes large amount of moisture before a food material enters a
dehydration process (e.g. manufacturing milk powder.)
It also reduces water activity by increasing the concentration of solution solids in
food materials for preservation (e.g. manufacturing sweetened condensed milk)
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6. APPLICATION
 Concentration of milk to produce condensed milk
 Concentration of juices
 Concentration of NaOH, NaCl from aqueous solutions to produce salt.
 Ether recovery from fat extraction
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7. FACTOR AFFECTING
EVAPORATION
1) Temperature:
Heat is necessary to provide the latent heat of vaporization, and in general, the rate of
evaporation is controlled by the rate of heat transfer. Rate of heat transfer depends on the
temperature gradient.
Many pharmaceutical agents are thermo labile. So the temperature that will cause the least
possible decomposition should be used.
e.g. Many glycosides and alkaloids are decomposed at temperature below 1000C.
Some antibiotics are concentrated by freeze-drying.
2) Temperature and time of evaporation
Exposure to a relatively high temperature for a short period of time may be less destructive of
active principles than a lower temperature with exposure for a longer period.
Film evaporators used a fairly high temperature but the time of exposure is very short. An
evaporating pan involve prolonged heating.
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8. FACTOR AFFECTING
EVAPORATION
3) Temperature and moisture content
Some drug constituents decompose more rapidly in the presence of moisture, especially at a
raised temperature (by hydrolysis). Hence, evaporation should be carried out at a low controlled
temperature, although the final drying can be performed at higher temperature when little
moisture remains.e.g. Belladonna Dry Extract is an example of this type.
4) Type of product required
Evaporating pans or stills will produce liquid or dry products, but film evaporators will yield
only liquid products. So a dilute extract can be first concentrated in a film evaporator and then
the concentrated extract may be died in an evaporating pan.
5) Effect of concentration
As the liquor becomes concentrated, the increasing proportion of solids results in elevation of
the boiling point of the solution. This leads to a greater risk of damage to thermo labile
constituents and reduction of the temperature gradient.In general concentrated solutions will
have increased viscosity, causing thicker boundary layers, and may deposit solids that may build
up on the heating surface that reduce heat transfer.
All these problems may be minimized by turbulent flow condition.
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9. DIFFERENCE BETWEEN
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10. TYPES OF EVAPORATOR
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TYPES OF
EVAPORATERS
STEAM
JACKETED
KETTLE
CLIMBING
FILM
EVAPORATOR
MULTIPLE
EFFECT
EVAPORATOR
FORCED
CIRCULATION
EVAPORATOR
HORIZONTAL
TUBE
EVAPORATOR

11. STEAM JACKETED KETTLE
Steam Jacketed kettle is very large having deep kettles mounted on a platform
standing on the floor.
Two third portion of the kettle bottom is shielded by metal jacket.
The shallow kettles are fully jacketed
 PRINCIPAL
a. It is also a natural circulating evaporator
b. Steam is supplied to Jacketed kettle in which liquid extract is placed
c. Steam gives out heat to kettle.
d. The steam heat transferred to aqueous extract by Conduction and convection
e. As temperature raises solvent molecule present at surface starts vaporizing
f. As temperature raises vaporization increases
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12. CONSTRUCTION:
Hemispherical structure consist of inner pan called kettle
Kettle is enveloped with outer pan called Jacket
The two pan are joined to enclose a space thorough which steam is passed
Material of construction is Copper, Tinned Copper(For Acidic extract), Tinned Iron.
Jacket consist of Inlet and outlet for non-condensed steam at the top
Condensed steam removed through outlet provided at the bottom
The kettle is provided with one outlet for product discharge at the bottom.
WORKING:
Place the aqueous extract to kettle
Steam supplied through Inlet
Steam gives out heat to content and condensate leaves through outlet
Content must be stirred manually or mechanically
Rate of evaporation is fast initially and gradually slower down as extract became concentrated
Operation must carried out in well ventilated place.
On completion product is removed through outlet present at bottom or by tilting the kettle. 11

13. Working:
Place the aqueous extract to kettle
Steam supplied through Inlet
Steam gives out heat to content and condensate leaves through outlet
Content must be stirred manually or mechanically
Rate of evaporation is fast initially and gradually slower down as
extract became concentrated
Operation must carried out in well ventilated place.
On completion product is removed through outlet present at bottom or
by tilting the kettle.
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14. HORIZONTAL TUBE
EVAPORATOR
Horizontal Tube Evaporator is a modified form of open pan evaporator. In this the pan is enclosed
within a vertical cylinder.
Bottom portion of this cylinder contains the liquid to be evaporated in which horizontally
arranged heating tubes are immersed.
However in this evaporator circulation of liquid is poor.
Principle:
Steam is passed through the horizontal tubes, which are immersed in a pool of liquid to be
evaporated.
Heat transfers through the tubes and the solvent evaporates.
Concentrated liquid is collected.
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15. Construction:
Large cylindrical body with doomed shaped at the top and bottom, made of cast iron or plate steel.
The lower part of the body consists of steam compartment with inlet for steam at one end and a
vent for non-condensed gases on the other end.
A condensate outlet is provided at the bottom of the steam compartment.
At one point an inlet for feed is provided and one outlet for vapor is placed at the top of the dom.
Another outlet for thick liquid is placed at the center of the conical bottom of the body.
Working:
Feed is introduced into the evaporator until the steam compartment is immersed.
The horizontal tubes receives the heat and conduct it to the liquid.
The feed absorbs heat and solvent gets evaporated.
Concentrated liquid is collected.
Uses:
Best suited for non-viscous solution. E.g. Cascara extract
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16. 15
Advantages:
Cost per square meter of heating surface is less.
Disadvantages:
Requires large heating area
Not suitable for heat sensitive material
Unsuitable for crystalline products

17. CLIMBING FILM
EVAPORATOR
The climbing film evaporator has advantages of high heat transfer coefficient and
short residence time for the liquid to be evaporated.
The temperature difference in rising film evaporators should be high between the
heating chest and boiling chamber for proper circulation and formation of a climbing
film.
Principal
Tubes are heated externally by steam.
The preheated tubes enters from the bottom and liquid flows up through the heated
tubes.
Liquid near walls becomes vapor and forms small bubbles. Larger bubbles flow up
with slag and strikes deflector.
Deflector throws the concentrate, down to the bottom.
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18. Construction:
Heating unit consists of steam jacketed tubes.
 Long and narrow tubes are held between the
plates.
Deflector is placed at the top of the vapor head.
 Inlets are provided for steam and feed.
Outlets are provided for vapor, concentrated
product, non condensed gases and condensate.
Uses:
 Insulin, liver extracts, vitamins, foaming liquids,
corrosive solutions can be concentrated
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19. Working:
The preheated liquid feed is introduced from the bottom of the unit.
Steam enters into the spaces outside the tubes through the inlet.
Heat transferred to the liquor through the walls of the tubes.
Liquid and vapor moves upward at high velocity.
Vapor and liquid is separated from upper part having cyclone separator.
The vapor leaves from the top while concentrate is collected from the
bottom
Advantages:
•Large area for heat transfer
•Enhanced heat transfer
•Suitable for heat sensitive materials
•Used for foam forming liquids
•Instrument needs less space
Disadvantages:
•Expensive, construction is quite
complicated
•Cleaning and maintenance is quite
difficult
•Large head space required
•Not for viscous, salting and scaling
liquids
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20. FORCED
CIRCULATION
EVAPORATOR
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Principle:
 Liquid is circulated through the tubes at high pressure by means of pump. Hence
boiling does not takes place as boiling point is elevated.
 Forced circulation creates agitation. When liquid leaves the tube and enters the vapor
head, pressure falls suddenly.
 This leads to flashing of superheated liquor. Thus evaporation is effected.

21. Construction:
The evaporator consists of a short tube calendria and a large cylindrical vessel (body of the
evaporator) for separation of vapor and liquid takes place.
The liquor inlet is provided at the side of the cylindrical vessel.
A pump is fitted in between the calendric and the body of the evaporator.
A tangential inlet for liquid under high pressure is placed at neck of the body of the evaporator
The vapor outlet is placed at the top of the body and it may be passed through a condenser to
collect the condensed liquid.
Working:
Feed is introduced through the liquor inlet.
Pump will force the liquid through the calendria.
Steam heats the liquid inside the calendria.
As it is under pressure in the tubes the boiling point is elevated and no boiling takes place. As the
liquor leaves the tubes and enters the body of the evaporator through the tangential inlet there is a
drop in pressure and vapor flashes off from the superheated liquor. The concentrated liquid is
pumped out through the product outlet and the vapor is collected through the vapor outlet.
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22. Uses:
 Insulin and liver extract
 Crystallizing operations
 Suitable for thermo labile substance
Advantages:
 Heat transfer coefficient is high
 Salting, scaling are not possible
 Suitable for high viscous preparations
Disadvantages:
 Equipment is expensive
 More power supply is required
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23. MULTIPLE EFFECT
EVAPORATOR
 A multiple-effect evaporator, as defined in chemical engineering, is an apparatus for
efficiently using the heat from steam to evaporate water.
 Water is boiled in a sequence of vessels, each held at a lower pressure than the last.
 Because the boiling point of water decreases as pressure decreases, the vapour boiled off in
one vessel can be used to heat the next.
 Generally the first vessel (at the highest pressure) requires an external source of heat
 Multiple Effect Evaporation remains one of the popular methods used for the concentration of
aqueous solutions.
 Water is removed from a solution by boiling the liquor in an evaporator and withdrawing the
vapour.
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24. Mechanism :
Pre-heating of a solution prior to evaporation – The feed solution is brought to its respective
boiling point before feeding it into the MEE plant.
Removal of water (solvent) as vapour by steam heating - steam injected in the steam chest
jacket gives an efficient heating to the feed solution by transferring its heat, hence the vapour of
solvent rises due to temperature difference.
Condensing the vapour removed – ones the vapour is separated from the fees then a cold inlet
in givento condense the vapors and the clean solvent is collected.
Construction:
A multiple effect evaporator system for concentrating a process liquid comprises:
 a plurality of evaporator effects arranged in series, each effect including a process liquid inlet
and a process liquid outlet; a heating fluid inlet and heating fluid outlet;
 heat exchange means in each effect for passing said process liquid in heat exchange
relationship with heating fluid for evaporating water out of said process liquid; and wherein
evaporated water from one effect serves as heating fluid for an adjacent effect; and
 an evaporative condenser provided with liquid inlet means for receiving process liquid from
one of said evaporator effects, and liquid outlet means for transmitting said process liquid to
another of said evaporator effects; and means for receiving heating fluid vapor and for passing
said heating fluid vapor in heat exchange relationship with cooled process liquid in a cooling
circuit, for condensing said heating fluid vapor.
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25. Working:
 Due to heat transfer, the liquid temperature increases & reaches the B.P. during this
process, vapor well be generated from the liquid feed.
 So, formed vapor displaces air in the upper part of 1st evaporator.
 Moreover, the vapor also displaces the air in the steam space of the 2nd evaporator.
 After complete displacement of air by vapor in the steam compartment of 2nd evaporator,
the second valve is closed. the vapor of 1st evaporator transmits its heat to the liquid of
2nd evaporator & gets condensed.
 Condensate is removed through the second condensate valve.
 These steps continue in the 3rd evaporator also.
 As the liquid in 1st evaporator gains temperature the difference in temperature between the
liquid & steam decreases, hence, the rate of condensation decreases.
 As a result, the pressure in the vapor space of 1st evaporator gradually increases to P1 by
increasing temperature to T1 , which is the B.P. of the liquid in first evaporator &
decreasing the temperature difference(t0- t1).
 A similar change takes place in the 2nd evaporator & the liquid reaches the B.P.
 similarly, the process will be repeated in 3rd evaporator. Finally 3 evaporators come to a steady
state with the liquid boiling in all the 3 bodies.
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26. As boiling proceed, liquid level in 1st evaporator comes down. Feed is introduced through the feed
valve to maintain the liquid level constant.
Similarly evaporation of liquid takes place in 2nd & 3rd evaporators.
To maintain the liquid levels constant, feed valves F2 & F3 are used for 2nd & 3rd evaporator
respectively.
This process is continued until the liquid in all the evaporators reaches the desired viscosity.
Now the product valves are opened to collect the thick liquid.
Thus in this evaporators, there is continuous supply of feed, continuous supply of steam &
continuous withdrawal of liquid from all 3 evaporators. Hence, evaporators work continuously.
Advantages:
 Suitable for large scale & for continuous operation.
 Highly economical when compared to single effect.
 Multiple effects, or stages, are now used to minimize the energy input
required to evaporate or boil off undesirable water content.
 The total evaporation achieved in these systems is approximately the number of effects times the
energy input to the first effect.
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27. 26
STEAM JACKETTED
KETTLE
HORIZONTAL TUBE
EVAPORATOR
CLIMBING FILM FORCED CIRCULATION

28. Thank You
Maharashtra (India)