A multiple-effect evaporator, as defined in chemical engineering, is an equipment for efficiently using the heat from steam to evaporate water. Steam is mostly used as heating medium in Multiple effect evaporator. Multiple Effect Evaporation remains one of the popular method for the concentration of aqueous solutions.

1. MULTIPLE EFFECT EVAPORATOR
EVAPORATION
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2. MULTIPLE EFFECT EVAPORATOR
 A multiple-effect evaporator, as defined in
chemical engineering, is an equipment for
efficiently using the heat from steam to
evaporate water.
 Steam is mostly used as heating medium in
Multiple effect evaporator.
 Multiple Effect Evaporation remains one of the
popular method for the concentration of
aqueous solutions.
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3.  Multiple effect evaporators are basically vertical tube evaporators
connected together.
 It consists of a large cylindrical body made up of cast iron with dome
shaped top and bottom. Inside the body, calandria is fitted at the
bottom.
 Calandria consists of a number of vertical tubes, diameter ranges from
0.05 to 0.075 meter and length of 1-2 meter. Figure indicates that the
vapor from first evaporator serves as a heating medium for the 2nd
evaporator. Similarly, vapor from 2nd evaporator serves as a heating
medium for the 3rdevaporator.
 Last evaporator is connected to a Cyclone separator.
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4. Construction
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5. Types of Feed Arrangement
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It’s divided in to Four category on the basis of feed
direction:-
1. Forward Feed Arrangement
Both feed and steam introduced in the first effect

6. Types of Feed Arrangement
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Backward feed Arrangement
Feed is introduced in last effect and steam
is introduces in first effect.

7. Types of Feed Arrangement
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Mixed Feed Arrangement
Feed is introduced in intermediate effect move
forward and then backward to effect 1 and
steam introduced in first effect

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Types of Feed Arrangement
Parallel Feed Arrangement
Feed is introduced directly in all three evaporators
without transferring it from one to the another

9. Working
 Multiple Effect Evaporation remains one of the
popular method used for the concentration of
aqueous solutions.
 Evaporation occur in three steps:-
1. Pre-heating of a solution prior to evaporation.
2. Removal of water (solvent) as vapor by steam
heating
3. Condensing the vapor removed.
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10. Operation (Parallel Feed Arrangement)
 In the beginning, the equipment is at room temperature and atmospheric
pressure. The liquid feed is introduced to all the three evaporator up to the level
of the upper sheets. The following operations are attempted to achieve the
effects as specified below.
 1. The vent valves V1, V2 and V3 are kept open and all other valves are
closed.
 2. Now high vacuum is created in liquid chamber of evaporator.
 3.The steam valve S1 and condensate valve C1 are opened. Steam is supplied.
Steam first replaces cold air in the steam space of 1st evaporator. When all the
cold air is removed, the valve, V1 is closed.
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12. 4. The supply of steam is continued until the desired pressure Po is
created in the steam space of 1st evaporator. At this pressure, the
temperature of the is t0.
5. Steam gives its temperature to the liquid feed in the 1st evaporator
and gets condensed. Condensate is removed through the valve C1.
6. Due to heat transfer, the liquid temperature increases and reaches
the boiling point. During this process, vapor will be generated from
the liquid feed.
7. 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.
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13. 8. After complete displacement off air by vapor in the steam
compartment of 2nd evaporator, the valve V2 is closed.
9. The vapor of 1st evaporator transmits its heat to the liquid of 2nd
evaporator and gets condensed. Condensate is removed through the
valve C2. These steps continue in the 3rd evaporator also.
 As the liquid in the 1st evaporator gains temperature, the
difference in temperature between the liquids and steam decreases
hence, the rate of condensation decreases..
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14.  A similar changes takes place in the 2nd evaporator and the liquid reaches the
boiling point. Similarly, the process will be repeated in 3rd evaporator. Finally three
evaporators comes to a steady state with the liquid boiling in all three bodies.
 As boiling proceeds, liquid level in evaporator comes down. Feed is introduced
through the feed valve F1, F2 and F3 are used for 1st, 2nd and 3rd evaporators,
respectively, to maintain the liquid level constant.
Thus in this evaporator, there is a continuous supply of feed, steam and
continuous withdrawal of liquid from all the three evaporators. Hence,
evaporator works continuously with all the temperature and pressure in
balance.

15. Applications
 Product concentration,
 Solvent Volume reduction in a
solution,
 Water / solvent recovery,
 Crystallization.
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16. Advantages
 Advanced System,
 Easy Operation And Maintenance, ,
 It is continuous operation
 Cost Effective Operations.
 Solvent recovery is possible.
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