Application of pellet softening (PS) as a scale prevention method in seawater desalination plants

Abstract

A B S T R A C TThis research investigates the potential of pellet softening (PS) on calcite particles as a control method to avoid scaling of calcium carbonate from seawater in desalination. Experimental studies were conducted in a 5 L agitated vessel under controlled temperature and agitation. The measured transient calcium ion concentration, salinity, pH, and total alkalinity of seawater during mixing with calcite particles show that the Ryznar Stability index (RSI) increased from 4.3 to 5.7, which means that the status of seawater changed from "high scaling potential "to "low scaling potential" after being subjected to PS process at 70˚C. The supersaturation of seawater with respect to calcite is reduced from 33.5 to 5.27. The results demonstrate that PS is a feasible and effective pretreatment strategy for thermal and membrane seawater desalination facilities.

Thermal Desalination

“…Addition of calcite and aragonite seed crystals to seawater at pH !8.2 and 50 C has been found to initiate precipitation. Treatment with relatively coarse (w0.5 mm) calcite seeds of seawater in the laboratory scale at pH ¼ 8.25 and T ¼ 50 and 70 C was found to reduce supersaturation with respect to calcite by a factor of six [69]. Treatment with relatively coarse (w0.5 mm) calcite seeds of seawater in the laboratory scale at pH ¼ 8.25 and T ¼ 50 and 70 C was found to reduce supersaturation with respect to calcite by a factor of six [69].…”

Corrosion protection effect of rust and scales: A “metal protects metal” perception by considering the examples of hematite and magnetite

“…The Ryznar stability index (RSI) is an effort to link water chemistry to an objective dataset of scale thickness seen in municipal water systems. 7,8 The idea of saturation level serves as the foundation for the RSI. Ryznar quantified the link between the saturation state of calcium carbonate and scale development.…”

“…The water heater eventually malfunctions because the metal surface pits to the point where it can no longer withstand the pressure of the water. The Ryznar stability index (RSI) is an effort to link water chemistry to an objective dataset of scale thickness seen in municipal water systems 7,8 . The idea of saturation level serves as the foundation for the RSI.…”