טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMaya Ilevicky
SubjectScale Inhibition by Trace Amounts of Metallic Ions
DepartmentDepartment of Chemical Engineering
Supervisors Professor Emeritus Semiat Raphael
Professor Emeritus Hasson David


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.