טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentVictor Lumelsky
SubjectStudy of an Electrolytic Scale Prevention Method
DepartmentDepartment of Chemical Engineering
Supervisors Professor Emeritus Semiat Raphael
Professor Emeritus Hasson David


Abstract


The precipitation of sparingly soluble salts such as , and from hard waters is a problem encountered in many industrial operations, notably cooling water systems and water desalination processes. In view of the deleterious effects caused by scale deposition, it is imperative to implement measures for preventing, or at least mitigating, the scaling process in water systems prone to scaling.

A relatively new technique proposed for scale control consists of an electrolytic process in which scaling ions are removed by electrolysis. The high pH environment formed around the cathode, induces precipitation of  a widely encountered scale species.

The aim of the present work was to evaluate the potential of electrolytic methods for scale control in reverse osmosis (RO) desalination processes. An experimental system was constructed consisting of a cylindrical geometry electrolytic cell and a feed system enabling preparation of feed water of a desired hardness.

The main results of this study were obtained with an improved electrolytic cell designed according to the model developed in this work. It was found that the specific energy required for precipitating a unit mass of scale can be minimized by operation at an optimum current density. This specific energy consumption was found to decrease with the increase in solution hardness. The rate of scale deposition increased with the velocity of flow through the electrolytic cell and was found to conform to a mass transfer model.

A preliminary economic analysis, based on the data of this research, indicates a marked potential of the electrolytic scale removal technique for reducing costs and justifies further work aiming to integrate this technique in RO desalination.