The sludge evaporator concept utilizes a Mechanical vapor Recompression (MVR) design and falling film principles. Designed to operate below atmospheric pressure, the system enables an incoming influent to boil at a relatively low temperature. The resulting vapor gains both heat and pressure energy from a compressor (fan) and is then condensed on the pressure side of the heat transfer element. Latent heat from the condensing side of the surface is transferred to the concentrating side and is used as the heating stream in the same stage. The MVR system typically returns 80% – 99% of the waste effluent to the process as clean condensate while reducing the waste water volume to less than 20% to 1% of the original system. These values are the effluent specific and can vary due to wastewater characteristic.
The system design pressure is maintained by a standard liquid ring vaccum pump. This pump is also used to remove any incondensable gases. Heat from this gas vapor mixture is recovered by a plate exchanger. Evaporation takes place under vaccum: operation is 150 – 250 mbar in which water vaporizes at the temperatures of 55-65 Deg C.