An Equilibrium Model for Chloride Removal from Recycled Cooling Water Using Ultra-High Lime with Aluminum Process

摘要

Removal of chloride from recycled cooling water is needed to reduce corrosion and to prolongequipment life. Laboratory experiments have demonstrated that the ultra-high lime withaluminum process (UHLA) has the ability to achieve high chloride removal efficiency fromrecycled cooling water. In an effort to further understand the behavior of chloride in the UHLAprocess, a fundamental model of the chemical processes was developed. The purpose of thispaper is to describe this equilibrium model and present values for solubility products ofprecipitated solids that have not been previously investigated. The model was based onPHREEQC and a new program called INVRS K was integrated with PHREEQC to calculatevalues of unknown or poorly defined equilibrium or kinetic constants using a Gauss-Newtonnonlinear regression routine. Model predictions indicated that the results could be best describedby assuming the formation of a solid solution of calcium chloroaluminate (Ca4Al2Cl2OH12),tricalcium hydroxyaluminate (Ca3Al2OH12), and tetracalcium hydroxyaluminate (Ca4Al2OH14).