Page 29 - Practical Technology 2025

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Clinical Pharmacy-Pharm D Level Three 2 Semester 2024/2025 Pharmaceutical Technology (PT 607)

Lab (2): Evaporation
➢ Definition:
It is the removal of a solvent from a solution by vaporization (the concentration
of solution by boiling).

➢ General principle:
▪ The solution to be evaporated is heated by steam till boiling.

▪ The vapors coming out of solution is removed outside the evaporator.
▪ The solution is concentrated due to the loss of some of its solvent in the
form of vapors.
▪ After heating the solution, the steam is condensed into drips (condensate).
▪ The non condensed gases is removed due to steam passage through the
vent.
▪ Steam is separated from the heated solution by a metal surface (pan or

tubes).

➢ Terms:
▪ The solution to be evaporated = feed
▪ The concentrated product= concentrate= thick liquor
▪ Non condensed gases (air)= vent
▪ The condensed steam= drips = condensate
▪ Feed produces concentrate + vapors
▪ Steam produces drips (condensate) + vent

▪ Heating element = tube bundle

➢ Heat transfer in an evaporator:
The normal rate equation for heat transfer is given in the following form:

Q = U. A. T

Where,

Q is the heat transferred per unit time

U is the overall heat transfer coefficient

T is the temperature differences between the steam and the solution to
be evaporated

A is the area of the heat transfer surface (pan or the tube bundle) So
tubes bundle instead of pan to increase the area

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