Page 526 - Industrial Wastewater Treatment, Recycling and Reuse

496 Industrial Wastewater Treatment, Recycling, and Reuse

1st effect
Calandria
2nd effect
Feed in Vapors to
2nd effect Calandria
Steam in
Vapors to 3rd effect
3rd effect Calandria
Vapors to
condensor

1st effect
vapor
separator
Condensate 2nd effect
out vapor
separator 3rd effect
vapor
Feed to 2nd effect
Condensate separator
out
Feed to 3rd effect
Condensate
out
Product
out
Figure 13.4 Schematic of multiple effect evaporator.

• Evaporators with more than four to five effects are rarely practical (see
Figure 13.4 for a schematic of a multiple effect evaporator).
MEE is very simple in operation and the most proven system for evapora-
tion. It is the least energy efficient of all evaporation types, however. The
most important parameter for MEE is the feed effluent characteristic, which
plays a major role in deciding the number of effects.

13.3.3 Thermal Vapor Recompression

In this evaporation method, compression is performed thermally, as opposed
to mechanical vapor compression. The TVR system is shown in
Figure 13.5.
• A steam jet ejector is used to raise the temperature and pressure of vapors
generated from the first effect of the evaporator.
• The motive steam mixes with a portion of the vapors generated from the
first effect of the evaporator.
• The resultant vapors (motive steam plus some vapors from the first effect)
are utilized in first effect for condensation.