Page 524 - Industrial Wastewater Treatment, Recycling and Reuse

494 Industrial Wastewater Treatment, Recycling, and Reuse

Vapors
Steam
Feed

Condensate

Concentrated
product

Figure 13.2 Forced circulation evaporator.

• This type of evaporator can operate with minimal temperature differ-
ences between the heating media and the boiling liquid, and therefore,
it involves a greater number of effects.
• Scaling inside the tubes is less, leading to high operating time.
• Forced circulation evaporators can be installed vertically as well as hor-
izontally, thereby saving space.

Limitations
• Relatively high heat transfer area, leading to higher CAPEX.
• Higher recirculation rates, leading to higher power requirements and
thus higher OPEX.

13.3.1.3 Forced Falling Film Evaporator
This design is a variation on the conventional falling film evaporator, and has
additional benefits in terms of the following:
• It has all of the advantages of conventional falling film evaporation (see
Figure 13.3).
• Proper wetting rate in the tubes is achieved by using spraying nozzles.
• It is less prone to fouling than its conventional counterparts.