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Renin Angiotensin Mechanism.

Forced Circulation Evaporators.

 

Definition:

  • The equipment used for carrying out the process of evaporation are called “Evaporators”.

  • Evaporators are classified according to the form of the heat movement,

    • Natural circulation evaporators. e.g Evaporating Pan.

    • Forced circulation evaporation. e.g. Modified evaporating pan.

    • Film evaporators. e.g Climbing film evaporator.

FORCED CIRCULATION EVAPORATORS:

  • Forced circulation evaporators are natural circulation evaporators with some added form of mechanical agitation. Different forms of forced circulation evaporators can be designed.

  • An evaporating pan, in which the contents are agitated by a stirring rod or pole could be described as a forced circulation evaporator.

  • A mechanically operated propeller or paddle agitator can be introduced into an evaporating pan or still.

  • Propeller or paddle agitator can be introduced into the downtake of a short-tube evaporator.

  • A typical forced circulation evaporator can be shown as follows:


Construction:

  • The evaporator consists of a short tube calandria and a large cylindrical vessel (body of the evaporator) for separation of vapor and liquid. 

  • The liquor inlet is provided at the side of the cylindrical vessel. 

  • A pump is fitted in between the calandria and the body of the evaporator. 

  • A tangential inlet for liquid under high pressure is placed at the neck of the body of the evaporator. 

  • The vapor outlet is placed at the top of the body and it may be passed through a condenser to collect the condensed liquid.

Working Principle:

  • Feed is introduced through the liquor inlet. 

  • Pump will force the liquid through the calandria. 

  • Steam heats the liquid inside the calandria. 

  • As it is under pressure in the tubes the boiling point is elevated and no boiling takes place. 

  • As the liquor leaves the tubes and enters the body of the evaporator through the tangential inlet there is a drop in pressure and vapor flashes off from the superheated liquor. 

  • The concentrated liquid is pumped out through the product outlet and the vapor is collected through the vapor outlet.

Advantages

  1. Rapid liquid movement improves heat transfer, especially with viscous liquids or materials that deposit solids or foam readily.

  2. The forced circulation overcomes the effect of greater viscosity of liquids when evaporated under reduced pressure.

  3. Rapid evaporation rate makes this method suitable for thermolabile materials, e.g. it is used in practice for the concentration of insulin and liver extracts

Commonly Asked Questions.

  1. Define evaporation and write a short note on “Forced Circulation Evaporators.”.

  2. With help of a well labelled diagram, describe construction and working of “Forced Circulation Evaporators”.
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