M.Sc Thesis


M.Sc StudentIlevicky Maya
SubjectScale Inhibition by Trace Amounts of Metallic Ions
DepartmentDepartment of Chemical Engineering
Supervisors PROFESSOR EMERITUS Raphael Semiat
PROFESSOR EMERITUS David Hasson


Abstract

A serious difficulty encountered in many industrial processes is the tendency of sparingly soluble salts such as CaCO3 to precipitate from hard water on flow surfaces and cause operational problems. A common technique for coping with this difficulty is to dose to the water with scale inhibiting chemicals (“anti-scalants”). The objective of the present research was to investigate the potential of scale inhibition by a new technique based on releasing Zn ions by contact with readily available Cu-Zn alloy redox media.

The tasks accomplished in this study were a critical literature review of the scale inhibition mechanisms involved, correlation of literature data, and experimental investigation of the scale suppression induced by Zn released from Cu-Zn redox alloy media in two systems - an electrically heated kettle simulating heating of water in a flow tank and an annular flow constant heat flux system simulating heating of water flowing through heat exchangers pipes.

Results of this research indicate a significant potential for the technique of  Zn release by contact with Cu-Zn for scale control. The experimental data show that that the presence of 1-1.5 ppm of Zn+2 in scaling waters of LSI in the range of 1.0 to 1.5 can reduce the scaling rate by a factor of 3 to 5 in a hot water kettle system and by a factor of about 2 in the flow of water at high Reynolds numbers over a heated tube.