Parametric study of calcium sulfate crystallization fouling in cross-flow heat exchanger using response surface methodology.

Super saturation of inversely soluble salts in the phosphoric acid concentration process, like calcium sulfate, promotes fouling on the heat exchanger walls. This phenomenon leads to reduce the efficiency of such equipment and their continuous operation and increase energy losses. The present work aimed at studying the effect of the deposit of calcium sulfate on the fouling resistance on a heated walls. The fouling resistance was determined based on the operating data collected from the phosphoric acid concentration loop of a cross flow heat exchanger. X-ray diffraction analysis method was used to determine the crystal form of calcium sulfate. In addition, this paper aimed at modeling the fouling resistance with experimental data under various operating conditions using response surface methodology (RSM) in order to studying the interactive effects of operating parameters on fouling. Results show that the anhydrite (CaSO4) is the main crystal form of fouling formed on heat exchanger walls indicating that the crystallization fouling dominates the fouling process. The volume flow affects the fouling resistance especially at high wall temperature by increasing the fouling resistance with decreasing volume flow. The fluid temperatures are found to enhance significantly the fouling resistance on the surface. The determination coefficient of the proposed RSM model in the studied case was found to be 99.54%, which is considered to be satisfactory. [ABSTRACT FROM AUTHOR]