Scaling of process equipment by saline streams - challenges ahead

Scaling is a major problem and bottleneck in operation of all types of equipment used for handling and/or processing saline streams. The challenge is to be able to determine the criteria to define and predict the onset and rate of scale formation. Even though precipitating salts co-exist in industrial water systems, due to the complexity of the fouling process, research has primarily been concentrated on a single salt precipitation. And solubility concentrations obtained for single salt crystallization have been used as a measure of scaling potential in actual practical situations and usually not with much success. This paper critically assesses the current practices and shows based on the recent work by the author's research group that the thermodynamics and kinetics of single salt crystallization are not applicable to practical conditions of feed water when a mixture of salts is present. Presence of other species, salinity effects and even presence of trace components could have a detrimental effect on scaling potential of given water and cannot be ignored. Application of Debye Huckle theory or a modified version of that though essential, is not sufficient.