DEPARTMENT OF CHEMICAL ENGINEERING 21.3.2016 1 EVAPORATORS DAIRY INDUSTRY APPLICATION Asist. Prof. Levent AKYALÇIN 21.3.2016 2 Evaporation • Evaporation is the conversion of a liquid to a vapor. • Evaporation is the removal of volatile solvent from a solution or relatively dilutes slurry by vaporizing the solvent. Evaporators are used for this process. 21.3.2016 3 Evaporators Evaporators are used to separate materials based on differences in their boiling temperatures. Its purpose is to concentrate nonvolatile solutes such as organic compounds, inorganic salts, acids or bases. Typical solutes include phosphoric acid, caustic soda, sodium chloride, sodium sulfate, gelatin, syrups and urea. 21.3.2016 4 Types of Evaporators 1) 2) 3) 4) 5) Long-Tube Vertical Evaporators Short-Tube (Calandria) Vertical Evaporators Horizontal-Tube Evaporators Forced Circulation Evaporators Agitated, Thin Film Evaporators 21.3.2016 5 LONG-TUBE VERTICAL (LTV) EVAPORATORS These types of evaporators are used more than all other types combined for evaporation because of low cost per unit capacity simplicity of construction heat transfer performance The LTV-type evaporator cannot handle crystallizing solutions but excellent for foaming solution. There are two main types of LTV evaporators: a) b) 21.3.2016 Climbing (Rising) film evaporators Falling film evaporators 6 Climbing (Rising) Film Evaporators • LTV rising-film evaporator is used primarily to concentrate non-salting liquors. • Climbing film evaporators are used mainly in the paper industry, food industry to condense milk. 21.3.2016 7 Double-Effect, LTV Climbing (Rising) Film Evaporator 21.3.2016 8 Falling Film Evaporators • LTV falling film evaporator can be used to concentrate the non-salting liquids and more viscous liquors. • Principal applications have been for citrus juices. They are also used to concentrate heat-sensitive materials and corrosive solutions. 21.3.2016 9 Two, 4-Stage, Mechanical Recompression, Falling-Film Evaporators 21.3.2016 10 SHORT-TUBE (CALANDRIA) VERTICAL EVAPORATORS (STV) • The short tube evaporators were the first developed commercially and still represent probably the largest number of unit in operation. • Used in sugar factory. • Used for noncorrosive materials. 21.3.2016 11 Advantages Inexpensive Efficient heat transfer at high temperature Easy to descale Disadvantages × × Poor heat transfer at low temperature differences or with viscous liquids Require a great deal of floor space 21.3.2016 12 HORIZONTAL TUBE EVAPORATORS Horizontal tube evaporators use a tube and spray method of heat transfer. The tubes are arranged so as to maximize the heat transfer area between the steam and the liquor. Symbols: C = condensate F = feed N = noncondensibles’ vent P = product or concentrate S = steam V = vapor 21.3.2016 13 The major use is for making distilled water for boiler feed. Horizontal tube evaporators are used in the pharmaceutical industry, pulp and paper industry. They are relatively low cost. They have very low headroom. Horizontal tube evaporators are not suitable for salting or scaling liquids, and they have smaller capacity than other evaporators. 21.3.2016 14 Horizontal Tube Evaporator 21.3.2016 15 FORCED CIRCILATION EVAPORATORS • The liquor in a forced-circulation evaporator is pumped through the tubes to minimize tube scaling or salting when precipitates are formed during evaporation. • Submerged-tube type is the most common type forced circulation evaporator. • Forced circulation evaporators are used in the mining industry, and also they are used to evaporate corrosive or highly viscous solutions. • Forced circulation evaporators are efficient the transfers heat from steam to liquid, continuous liquid flow, low amount of salting, scaling and fouling. They are expensive and need power for circulating pump. 21.3.2016 16 Forced Circulation Evaporator 21.3.2016 17 AGITATED THIN (WIPED-FILM) FILM EVAPORATORS Agitated film evaporators use mechanical to promote heat transfer. They employ a single large diameter straight or tapered tube as the heating surface, in which a set of the blades is rotated. The cost of these evaporators is very high and the capacity relatively low. These evaporators are used highly viscous liquids or liquids requiring very low residence times. These evaporators exhibit poor heat transfer performance on low viscosity fluids. Their maintenance are difficult because of internal moving parts. Symbols: C = condensate F = feed N = noncondensibles’ vent P = product or concentrate S = steam V = vapor Agitated Thin Film Evaporator 21.3.2016 18 21.3.2016 19 Evaporated and Condensed Milk Evaporated milk is made by reducing the water content by using an evaporator. Condensed milk is processed similarly to evaporated milk, but sugar is added to improve flavor and increase storage life. The following processing steps are usually involved: Milk is received an cooled. Milk is sampled and evaluated for bacterial count, sediment, acidity, alcohol, appearance, flavor, and odor. Milk is clarified or filtered. Milk is stored and fat standardized to solids not fat. Milk is preheated and held. Water is removed by evaporation. Product is homogenized. Product is cooled. (If making condensed milk, homogenized precedes evaporation and sugar is added immediately after condensation.) Product is restandardized Product is placed in cans which are sealed. Leaking cans are rejected. Product in cans is heated, sterilized, and cooled. Cans are cased. Cans with product are stored. 21.3.2016 20 EVAPORATION İN DAIRY INDUSTRY Definition of evaporation in application of dairy industry is removing moisture from milk under a vacuum with boiling. A type of evaporator used in milk industry 21.3.2016 21 EVAPORATOR TYPES USED IN THE MILK INDUSTRY Many evaporators are produced in various designs. Single-or multiple-effect evaporators are used. Double- and triple- effect evaporators are most common. Appropriate types of evaporators that can be used in the milk industry are as follows; 21.3.2016 Falling Film Evaporators Circulation/Vertical Evaporators Horizontal Tubes Evaporators 22 Some Photos of Evaporators Which are used in Bozüyük Milk Industry 21.3.2016 23 21.3.2016 24 21.3.2016 Number Name 23378324080 BERDA ALTUN 24395379350 EMRAH ÖREK 37750471576 CANSU KAYAALP 55129570408 SEVİM ÖZGÜL 60907135168 PINAR ERKUŞ 25 THANKS… 21.3.2016 26