The Use of Modern Methods in the Development of Calcium Carbonate Inhibitors for Cooling Water Systems

Cooling water systems represent the single largest area of industrial water use. Most of these systems operate by evaporative cooling, allowing the system water to become supersaturated with respect to dissolved mineral salts. In such a cooling system, cool water is pumped across metal heat exchange tubes which are in contact with a hot process. The heated water then enters a cooling tower and, through evaporation, becomes cooled. The remaining cool water reenters the system to repeat the process. Since heated system water is lost through evaporation, the concentration of dissolved solids in the system water increases. As a result, the cooling water can become highly supersaturated with respect to mineral salts. Calcium carbonate, for example, can deposit on the heat transfer surfaces of the cooling system, thus lowering heat transfer efficiency, increasing pumping costs and requiring frequent system cleaning. Substoichiometric deposition control chemicals have long been the most cost effective solution to the problem of mineral salt deposition.1 The addition of a small amount of deposit treatment chemical can have a dramatic effect on the formation of mineral scales. Continuous improvement of inhibitor chemistries is necessary due to constantly progressing technical, financial, and environmental treatment requirements. A key to the efficient development of acceptable calcium carbonate control chemistries is an understanding of the influence of inhibitor structural parameters on the fundamental processes involved in scale formation.2