Evaporation-Plant

Evaporation

Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance.

A great variety of evaporator designs are developed for specialize applications, these can be grouped into following basic types:

Evaporation Systems:

1.Falling Film Evaporation

Principle of Operation:

Advantages:

Applications:

2.Rising Film Evaporation

Principle of Operation:

  • In rising film evaporator liquid being evaporated is fed from the bottom into long tubes and heated with steam condensing on the outside of the tube from the shell side.
  • This is to produce steam and vapour within the tube bringing liquid inside to a boil.
  • The vapour produced then presses the liquid against the walls of the tubes and causes the ascending force of this liquid.
  • As more vapours are formed, the centre of the tube will have a higher velocity which forces the remaining liquid against the tube wall forming a thin film which moves upwards.

    • Advantages:

  • Low residence time
  • High heat transfer coefficient
  • High evaporation ratio

    • Applications:

  • Juice concentration & Food processing
  • Production of polymers
  • Thermal desalination
  • Pharmaceuticals
  • Solvent recovery
  • Waste water& Effluent treatment

    • Rising_Film_Evaporator_Diagram_lable

    3.Forced circulation evaporation:

    Principle of Operation:

  • Liquid is circulated at high flow rate through heat exchanger, boiling being prevented within the unit by virtue of hydrostatic head maintained above top tube plate.
  • As liquid enters separator where absolute pressure is slightly less than in tube bundles, liquid flashes to form vapors.
  • Vapors are then passed to next effect and liquid is kept in continuous circulation. Once desired concentration is achieved product is taken out from final effect.
  • Steam or vapors are used as heating media in forced circulation evaporation.

  • To maintain a good heat transfer within the heat exchanger it is necessary to have a high recirculation flow rate.

  • Calendria can be arranged either horizontally or vertically depending on the specific requirements in each case.

    • Advantages:

  • Fouling is minimized due to high liquid velocities.
  • Optimized heat transfer.

    • Applications:

  • Spent Wash Distillery
  • Corn Steep Liquor
  • Liquids with a high tendency for fouling.
  • Highly viscous liquids.
  • Waste water treatment

    • Circulation-Evaporator