Rotating cylinder technique for assessing the effectiveness of anti-scalants

•Novel technique for evaluating anti-scalants (AS).•AS effectiveness analyzed from scale deposition tests on a rotating cylinder.•In the absence of an AS scale deposition rate found to be mass transfer controlled.•In the presence of effective AS dosage deposition shown to be independent of mass transfer rate.•AS effectiveness assessed by dosage level providing surface deposition control.

A novel technique for evaluating the relative inhibition effectiveness of different anti-scalants is presented. The technique is based on the ability of anti-scalants to modify the scale deposition mechanism from mass transfer control to surface control. A rotating cylinder system which is known to provide well controlled mass transfer conditions is used to determine the scaling rate of a supersaturated solution dosed with various feed concentrations of an anti-scalant. Mass transfer conditions were characterized by turbulent flow at hydrodynamically smooth surface. In the absence of an anti-scalant, scale deposition is mass transfer controlled and scaling rate increases with rotation speed. With sufficient anti-scalant dosage, precipitation is modified to surface control and rotation speed has no effect on the scale deposition rate. Determination of the critical anti-scalant dosage enabling surface controlled precipitation provides a sensitive technique for comparing the relative effectiveness of different anti-scalants.