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 toinvestigate the influence of heating and cooling rate, and water composition on the kinetics of inorganic saltprecipitation taking place when water is heated from ambient temperature up to its boiling point. The kinetics ofsalt precipitation in the bulk solution have been monitored through turbidity measurements as well as trackingion concentration throughout the heating/cooling process and the experimentalfindings highlight the criticalrole of the cooling step on the overall amount of salts that precipitate. The presence of magnesium ions in thewater was found to influence the precipitation of calcium carbonate which was found to be the dominant saltcrystallising out of solution; calcium sulphate was not observed.