Effects of Sodium and Potassium Chlorides on Silica Fouling

Abstract

The effects of NaCl and KCl salts in aqueous solutions on silica fouling of heat exchangers under turbulent flow conditions were examined experimentally over a range of pH, velocity, and salt concentration levels. The fundamental attachment process of silica fouling from those aqueous solutions was described. The silica fouling rate in NaCl solutions was found to be greater than that in KCl solutions. In all cases, the fouling rate increased with the salt concentration. When both salts were present simultaneously, the fouling rate found to be closer to that of the KCl system than that of the NaCl system. Effects of salinity on equilibrium solubility of silica at 165° C were also reported. Finally, the plausible theory of polymerization and the fundamental ion-cloud theory were used to describe the silica scale attachment process and the possible causes of salt effects on silica fouling of heat transfer surfaces.