Optimization of calcium sulfate precipitated in the laminar flow pipe through response surface modeling of temperature, Ca2+ concentration and citric acid additives

Abstract

This paper presents results of investigation of scaling of calcium sulfate (CaSO4) on metallic pipes. In this study, the optimizing variables; namely temperature (50-60°C), concentration of Ca2+ (2000-3000 ppm), citric acid concentration (10-20 ppm) were set-up to provide the optimum yield of the mass scales. The mineral scale detected using XRD is mainly gypsum, and the scale has a plate like morphology under SEM examination. SRM (surface response methodology) prediction provided that the temperature is a significant factor, while the Ca2+ concentration and the citrate are insignificant variables determining the optimal condition of the mass scale yields. An optimized mass scale response of 119.99 mg was obtained at a temperature of 56.36°C, concentration Ca2+ of 2649.21 ppm and citric acid concentration of 12.11 ppm, respectively. The addition of citric acid did not modify the crystal morphology, but may control the size of crystals.