Application of evaporator in food 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
Editor's Notes
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