Inorganic mineral precipitation from potable water on heat transfer surfaces

In this study, an experimental approach mimicking processes encountered in electric kettles has been designed to investigate the influence of heating and cooling rate, and water composition on the kinetics of inorganic salt precipitation taking place when water is heated from ambient temperature up to its boiling point. The kinetics of salt precipitation in the bulk solution have been monitored through turbidity measurements as well as tracking ion concentration throughout the heating/cooling process and the experimental findings highlight the critical role of the cooling step on the overall amount of salts that precipitate. The presence of magnesium ions in the water was found to influence the precipitation of calcium carbonate which was found to be the dominant salt crystallising out of solution; calcium sulphate was not observed.