A rising film evaporator is primarily used to concentrate non-salting and non scaling liquors.

In order to achieve a good heat transfer rate, the ΔT between the heat medium and the liquor should be preferably greater then 5 15 K. Operation of the rising film evaporator is straightforward. Liquor is fed into bottom of the heater. There it is heated with steam or any other suitable heat medium. If the vapor pressure of the feed equals or exceeds the system pressure, vaporization will occur immediately. The liquor climbs up inside of the tubes and therefore additional vapor is generated and the velocity of the liquor-vapor mixture increases to a maximum at the end of the tubes. The liquor-vapor separation takes place in the evaporation body by gravity and by an entrainment separator.