Forced Circulation Evaporator

Horizontal or vertical shell-and-tube heat exchanger or plate heat exchanger as the calandria, with flash vessel/separator arranged above the calandria, circulation pump.

Operation

The liquid is circulated through the calandria by means of a circulation pump, where it is superheated at an elevated pressure, higher than its normal boiling pressure. Upon entering the separator, the pressure in the liquid is rapidly reduced resulting in some of the liquid being flashed, or rapidly boiled off.

Since liquid circulation is maintained, the flow velocity in the tubes and the liquid temperature can be controlled to suit the product requirements independently of the pre-selected temperature difference.

Particular features

Long operating periods – boiling/evaporation does not take place on the heating surfaces, but in the separator. Fouling due to incrustation and precipitation in the calandria is therefore minimized.
Optimized heat exchange surface – flow velocity in the tubes determined by the circulation pump.

Fields of application

Liquids with a high tendency for fouling, highly viscous liquids, as the high concentration step in multiple-effect evaporation plants.
Forced circulation evaporators are optimally suited as crystallizing evaporators for saline solutions.