Evaporation plants heated by mechanical vapor recompressors (MVR) require particularly low amount of energy.
Whereas steam jet compressors only compress part of the vapor, mechanical vapor recompressors recycle all of the vapor leaving the evaporator.
The vapor is recompressed to the pressure of the corresponding heating steam temperature of the evaporator, using a mere fraction of electrical energy relative to the enthalpy recovered in the vapor. The energy of the vapor condensate is frequently utilized for the preheating of the product feed. The amounts of heat to be dissipated are considerably reduced, with the evaporator itself absorbing the energy normally dissipated through the condenser cooling water.
Depending on the operating conditions of the plant, a small quantity of additional steam, or the condensation of a small quantity of excess vapor may be required to maintain the overall evaporator heat balance and to ensure stable operating conditions.
Due to their simplicity and maintenance friendly design, single stage centrifugal fans are used in evaporation plants.
These units are supplied as high-pressure fans or turbo-compressors. They operate at high flow velocities and are therefore suited for large and very large flow rates at vapor compression ratios of 1:1.2 to 1:2.
Rotational speeds typically are 3,000 up to 18,000 rpm. For high pressure increases, multiple-stage compressors can be used.
