Evaporator Ppt

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Evaporator

EvaporatorEvaporationAnevaporatoris a device used to turn the liquid form of a chemical into its gaseous form. The liquid is evaporated, or vaporized, into a gas.

23.11.20132

EvaporationEvaporators are used to separate materials based on differences in their boiling temperatures.Evaporation is the removal of volatile solvent from a solution or relatively dilutes slurry by vaporizing the solvent.

Working PrincipleThe solution containing the desired product is fed into the evaporator and passes across a heat source. The applied heat converts the water in the solution into vapor. The vapor is removed from the rest of the solution and is condensed while the now-concentrated solution is either fed into a second evaporator or is removed. ApplicationsPharmaceuticalIndustry

Food and beverage Industry

Air conditioning systemClassification of EvaporatorNatural circulation EvaporatorForced circulation EvaporatorNatural Circulation EvaporatorNatural circulation evaporators are based on the evaporation of the product caused by thedensitydifferences that arise from heating. In an evaporator using tubing, after the water begins toboil, bubbles will rise and cause circulation, facilitating the separation of the liquid and the vapor at the top of the heating tubes. The amount of evaporation that takes place depends on the temperature difference between the steam and the solution.Types of Natural Circulation evaporatorsShort tube vertical evaporator

Basket type vertical evaporator

Long tube vertical evaporator

Forced Circulation EvaporatorForced circulation can be used by inserting a pump to increase pressure and circulation. Forced circulation occurs when hydrostatic head prevents boiling at the heating surface. A pump can also be used to avoid fouling that is caused by the boiling of liquid on the tubes.The residing time is undefined and the consumption of steam is very high, but at high temperatures, good circulation is easily achieved.Types of Forced Circulation EvaporatorsFalling film Evaporator

Climbing or Rising film Evaporator

Agitated Thin film Evaporator

The Plate EvaporatorShort-Tube Vertical Evaporators (STV) It has a short tube bundle enclosed in a shell called calandria. Calandria is annular in shape. Feed is supplied through a nozzle above the upper tube sheet & steam inlet is through calandria.When we heat it, first liquid will flow up because of density gradient. Then, because of this Vapour-Liquid disintegration it will flow down through central open surface of calandria called downtake or downcomer.

Short-Tube Vertical Evaporators (STV) AdvantagesInexpensiveEfficient heat transfer at high temperatureEasy to descale

DisadvantagesPoor heat transfer at low temperature differences or with viscous liquidsRequire a great deal of floor space

23.11.201312Basket-type EvaporatorThe liquid is inside the tubes and the steam is outside the tubes but the down take is annular.Recirculation occurs through the annular space.The condensate drips from the bottom of the basket through a steam trap.The vapor generated by the boiling of the liquid strikes a deflector plate fixed to the steam pipe.

Basket-type EvaporatorAdvantages:It can handle better scale forming solutions because of the convenience with which it can be cleaned.The heating element is held by 2 holders so it can be removed easily for repair work.Disadvantages:Like the calandria type device the basket evaporator is also unsuitable for viscous liquids because the natural circulation forces are not strong enough to circulate viscous liquidsComparison between standard type and basket type evaporatorsStandardBasket1

With central downtakeWith annular down take2Without baffleWith baffle3

The heating element cannot beremoved to cleanThe heating element can be easily removed to clean and repair4Not used for scaly liquorsCan be used for scaly out liquorsApplicationsThese evaporators lend themselves particularly well to the evaporation of salting and scale forming liquids. They have been used successfully in the sugar, caustic soda, sodium sulfate, and similar industries, wherever difficult maintenance and entrainment problems are encountered.

Long Tube Vertical EvaporatorVertical type evaporator differ from horizontal type evaporator in that the heating tubes are locating in a vertical position,and in that the boiling liquor is inside the tube and the heating system surrounds it.The long tube type evaporator is different from the calandria and basket vertical tube types in that the tubes are longer usually from 50 to 100 times the tube diameter.

Long Tube Vertical EvaporatorAdvantagesThe velocity of the boiling liquor (hence the rate of heat transfer) is greater.Capacity per unit of heating surfaceLow cost and less floor space requirementDisadvantages:High headroom requirement, unsuitable for viscous scale forming materials.

Evaporator AuxiliariesVacuum Pumps

Steam Traps

Float and Thermostatic Trap

The Inverted Bucket Trap

Entrainment Separator