Evaporators are used widely in the food industry to concentrate foods through the removal of water. There are several types of evaporators that operate using different mechanisms, but they all work to boil a liquid and remove the vapor, leaving a more concentrated solution. Single effect evaporators use a single heating and evaporation section, while multiple effect evaporators allow vapor from one chamber to heat the next, improving efficiency. Common applications in food processing include concentrating fruit and vegetable juices, dairy products, and syrups to reduce weight and volume before further processing.

1. Application Of Evaporator/Evaporation in food processing or in food industry
Assignment
Advanced Food Process Engineering( FEM2009)
Submitted by :-
Usman khan
M-Tech Processing and Food Engineering
Enrollment No.- FC1044 Submitted to :-
Er. Faizan Ahmed
Assistant Professor
Department Of P.H.ET

2. Contents
 What is Evaporation?
 What is Evaporator?
 Equipment/Types of Evaporator
 Methods Of operation of Evaporator
 Application Of Evaporator In Food Industry

3. Evaporation
 Evaporation may be defined as the vaporization of a
volatile solvent by ebullition to increase the
concentration of essentially non-volatile components
of a solution or suspension.
 In Evaporation, the vapour from a boiling liquid
solution is removed and a more concentrated solution
remains or removal of solvent ( Water) from an
aqueous solution by the action of heat.

4. Evaporation
 It increases the solids content of a food and hence
preserves it by a reduction in water activity.
 Evaporation is used to pre-concentrate foods (for
example fruit juice, milk and coffee) prior to drying,
freezing or sterilisation and hence to reduce their
weight and volume.

6. Evaporator
 An evaporator is a device in a process used to turn
the liquid form of a chemical substance such as
water into its gaseous-form/vapor.
 The liquid is evaporated, or vaporized, into a gas
form of the targeted substance in that process.
 Most of the industrial evaporators have tubular
heating surfaces.
 The tubes may be horizontal or vertical, long or
short .
 The liquid may be inside or outside the tubes.

7. Evaporator
 The selection of an evaporator should include the
following considerations:
 Operating capacity (as kilograms of water removed
per hour)
 Efficiency of the evaporator (Unit of water
evaporated per unit steam used).
 Degree of concentration required (as percentage of
dry solids in the product)
 Heat sensitivity of the product in relation to the
residence time and temperature of evaporation

8.  The requirement for facilities to recover
volatiles
 Ease of cleaning
 Reliability and simplicity of operation
 Size of the evaporator in relation to its capacity
 Capital and operating costs in relation to
capacity and product quality (Mannheim and
Passy, 1974).

9. Equipment/Types of Evaporator
1. Open kettle or pan
2. Horizontal-tube natural circulation evaporator
3. Vertical-type natural circulation evaporator
4. Long-tube vertical-type evaporator
5. Falling-film-type evaporator
6. Forced-circulation-type evaporator
7. Agitated-film evaporator
8. Open-pan solar evaporator

10. Open Kettle Or Pan Evaporator
 The simplest evaporator
consists of an open pan
or kettle in which the
liquid is boiled.
 The heat is supplied by
condensation of steam in
a jacket or in coils
immersed .

11. Horizontal tube Evaporator
 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.

12. Construction And Working-
 Construction- Large cylinder body with doomed shaped at
the top and bottom, made of Cast iron or plate steel.
Stainless steel tubes are used in steam
 Working - Feed is introduced into the evaporator untill the
steam compartment is immersed.
 The horizontal tubes recieves the heat and conduct it to the
liquid.
 The feed absorbs heat and solvent gets evaporated.
 Uses- Best suitable for non-viscous solution Eg- Cascara
extract

13. Fig. Horizontal tube Evaporator

14. Falling Film type Evaporator
 In a falling film evaporator, the liquid is fed
at the top of the tubes in a vertical tube
bundle.
 The liquid is allowed to flow down through
the inner wall of the tubes as a film.
 As the liquid travels down the tubes the
solvent vaporizes and the concentration
gradually increases.
 Vapor and liquid are usually separated at the
bottom of the tubes and the thick liquor is
taken out.

15.  The falling film evaporator is largely used
for concentration of fruit juices and heat
sensitive materials because of the low holdup
time.
 The device is suitable for scale forming
solutions as boiling occur on the surface of the
film.
 Pressure drop (up to 100 psig ), measured with a
pressure gauge at the entrance of the preheater.

17. Advantages Of Falling Film Evaporator
 The material passes through One time, and the heating time is
short , which can prevent thermal decomposition.
 Continuous operation, high effective time utilization rate of the
equipment.
 Low cooling water consumption.
 High heat transfer coefficient and good heat transfer
performance.
 Can be used for materials with higher solid content and
viscosity.
 Aroma recovery system can be added into the evaporator when
producing apple or orange concentrated juice processing line.

18. Agitated Thin Film Evaporator
 Agitated thin film evaporator consists of a vertical steam-
jacketed cylinder and the feed solution flows down as a film
along the inner surface of large diameter jacket .
 Liquid is distributed on the tube wall by a rotating assembly
of blades mounted on shaft placed coaxially with the inner
tube.
 The blades maintain a close clearance of around 1.5 mm or
less from the inner tube wall.
 The main advantage is that rotating blades permits handling
of extremely viscous solutions.
 The device is suitable to concentrate solutions having
viscosity as high as up to 100 P.

20. Method Of Operation Of Evaporators
 Single Effect Evaporators
 Multiple Effect Evaporators

21. Single Effect Evaporators
 The typical Evaporator is made up of three
function section .
 The Heat Exchanger
 The Evaporating section- Where liquid boils
and evaporates.
 Separator- In Which vapor leaves the liquid and
passes off to the condenser or the other
equipment.
 In many Evaporators all these three sections
are contained in a single vertical cylinder

22. Fig .Single Effect Evaporator

23. Construction Of Single Effect Evaporator
 In the centre of cylinder there is steam heating
section, with pipe passing through it in which the
Evaporating liquors rise .
 At the top of the cylinder the baffles which allow the
vapors to escape but check liquid droplets which may
accompany the vapors from the liquid surface.
 This type of Evaporator which may be called
conventional evaporator.

24. Mechanism Of Single Effect Evaporator
 In the heat exchanger section, called a Calandria
in this type of Evaporator, Steam condenses in
the Jacket and the liquid being evaporated boils
on the inside of the tubes and in the space above
the upper tube plate.
 The circulation of liquids greatly affects
evaporation rates but circulation rates and pattern
are very difficult to predict in any detail.
 As evaporation proceed, the remaining liquors
become more concentrated and because of this
the boiling temperature rise.

25. Mechanism of Single Effect Evaporator
 The rise in temperature of boiling reduces the
available temperature drop, Assuming no change
in the heat source . And so the total rate of heat
transfer will drop accordingly.
 Also the Viscosity of liquid will increase often
quite sabstantially , this affects circulations and
heat transfer coefficients leading again to lower
rates of boiling.

26. Multiple Effect Evaporator
 The method of increasing the evaporation per kilogram
of steam by using a series of evaporators between steam
supply and condenser is known as multiple-effect
evaporation.
 Multi effect Evaporation system is based on repeated
use of the water vapors from one evaporation unit
(effect) to heat the next effect, which operates at a lower
pressure.
 Thus 1Kg of steam can evaporate more water,
depending on the number of effects and the operating
pressure.
 In case of a tripple-effect evaporator, if the first effect is
operating at atmospheric pressure, then the second and
third effect operate under vacuum.

28. Application Of Evaporator In Food Industry
 Evaporators are used in a wide range of process.
 Including pharmaceuticals, Foods beverages,
Juices, dairy industry, sugar syrups, pulp and
paper, chemicals, polymers and resins, inorganic
salts, acids, bases, and a variety of other
materials.

29. Fruits and Vegetables
 Fruits puree (Grapes,Apple,Cherry)
 Grape juice, Blueberry juice.
 Beetroot juice, Lime juice,Carrot Juice.
 Pear juice,Passion fruit juice,Pineapple juice
 Acerola juice, Mango juice, Coconut juice
 Orange juice, Citrus Juice, Other Vegetable juice

30. Thank You