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Zero Liquid Discharge Solutions 497

High-pressure steam

Ejector
Feed

Steam

Condensate

High-pressure steam
Figure 13.5 Thermal vapor recompression system.

• TVR increases the overall energy efficiency of a multiple effect
evaporation plant.
• TVR is a more energy efficient system than multiple effect evaporation.
• TVR requires higher steam pressure.
• In TVR, steam condensate becomes contaminated with process conden-
sate (see Figure 13.5).

13.3.4 Mechanical Vapor Recompression
MVR achieves vapor compression through mechanically driven equipment
such as blowers or compressors (refer Figure 13.6).
• The system delivers superheated steam, which is then desuperheated
before it is fed back into the evaporator where it was produced.
• The energy input in the system is in the form of energy pumped to the
compressor.
• During steady operation, much less steam and cooling water is required,
as compared to the requirements of other evaporation systems.
• MVR is the most energy efficient system for evaporation.
• MVR requires almost no additional steam and cooling water during
steady operation.