STRUCTURE OF CaCO3 NANOCRYSTALS ON THE HEAT EXCHANGER WALL AND IN A SUPERSATURATED AQUEOUS SOLUTION

An analysis of thermodynamics of CaCO3 phase transition in a supersaturated aqueous solution showed that the formation of scale in the form of calcite on the channel wall in the absence of magnetic treatment of a water flow is related to a smaller Gibbs energy of the generation of the crystalline phase mentioned. Moreover, such a character of CaCO3 crystallization is caused by the fact that the magnitude of crystallographic mismatch between the crystallized salt (calcite or aragonite) and the surface (iron oxide and iron carbonate) is several times higher for aragonite. On considering the process of homogeneous generation in the aqueous bulk, it was found that nanosized nuclei with a radius over 1 nm also had the calcite phase, and those with a radius less than 1 nm have the aragonite phase. This effect was caused by a higher density of the aragonite phase. The results of the analysis of the thermodynamics of CaCO3 phase transition allow one to explain manifestations of the magnetic treatment antiscale effect observed in real-life heat-and-power installations.