Types of Evaporator

TYPES OF EVAPORATORS

ARAVIND.S

• NATURAL CIRCULATION EVAPORATORS• FORCED CIRCULATION EVAPORATORS

STANDARD VERTICAL TUBE EVAPORATOR• Consists of vertical cylindrical shell incorporating a tube

bundle with horizontal tube sheets bolted• Vapor outlet – Top• Liquor discharge – Bottom• Tube bundle – 150 cm height• Tube diameter > 75mm• Down take – At the centre circulates cooler liquid• Solution to be evaporated is inside and steam flows outside

the tubes

• Baffles – mixing• Vapors formed are disengaged into VAPOR DIDENGAGEMENT

SPACE• Condensate withdrawn at the bottom• Non condensable gas is vented out• Also called Calendria type evaporator

ADVANTAGES• Used to separate water and salts in sea water(DESALANATION)• Used in liquid food preservation.

HORIZONTAL TUBE EVAPORATOR

• Oldest type • Vertical cylinder shell has horizontal square tube bundles.• Channels are present for introduction of steam and

withdrawal of condensate• Vapor outlet – Top• Liquor discharge – Bottom• Steam is inside the tube and liquor surrounds the tube• Evaporation occurs OUTSIDE• Small diameter tubes than any other type

ADVANTAGES• Very low head room requirements• High heat transfer coefficient

DISADVANTAGE • Not suitable for viscous liquids

LONG TUBE VERTICAL EVAPORATOR

• Long tubular heating element • Incorporates tubes of diameter 25 – 50mm and 4 – 8m long• Heating element projects into a vapor space• Vapor outlet – Top• Liquor discharge – Bottom• Return pipe connecting the vapor space to the exchanger

provides NATURAL CIRCULATION

JACKETED PAN EVAPORATOR• Jacketed pans used in which condensing steam evaporates

part of the solvent• Pans are made of steel, copper, Aluminium• Mild steel jacket may be welded to the pan• Steam inlet – top• Product collector – bottom• Used only when small quantities are handled

Evaporator accessories

1. CondensersTwo types: surface condensers:The vapor to be condensed and cooling medium SEPARATED BY METAL WALLcontact condensers:They are MIXED directly

2. Vacuum pump/steam jet ejector

• PARALLEL CURRENT : non- condensed gases leave at the temperature of exit cooling water

• COUNTER CURRENT : non- condensed gases leave at the temperature of the entering cooling water

• WET CONDENSOR : non- condensed gases & Cooling water are removed by the same pump

• DRY : non- condensed gases & Cooling water are removed by the separate pump

• BAROMETRIC : Placed high enough so that water escapes from it by a barometric leg

• LOW LEVEL CONDENSER: water is removed by a pump.

MATERIALS OF CONSTRUCTION

• EVAPORARTOR BODY : fabricated from mild steel ( less expensive)• To PREVENT CORROSION : monel, inconel and

stainless steel are used.• TUBES : Copper, stainless steel.• TUBE SHEETS : bronze, nickel clad steel or

stainless steel