Calcium Carbonate Scaling Kinetics Determined from Radiotracer Experiments with Calcium-47

Abstract

The deposition rate of calcium carbonate on a heat-transfer surface has been measured using a calcium-47 radiotracer and compared to the measured rate of thermal fouling. The crystalline phase of calcium carbonate that precipitates depends on the degree of supersaturation at the heat-transfer surface, with aragonite precipitating at higher supersaturations and calcite precipitating at lower supersaturations. Whereas the mass deposition rates were constant with time, the thermal fouling rates decreased throughout the course of each experiment as a result of densification of the deposit. It is proposed that the densification was driven by the temperature gradient across the deposit together with the retrograde solubility of calcium carbonate. The temperature dependence of the deposition rate yielded an activation energy of 79 ± 4 kJ/mol for the precipitation of calcium carbonate on a heat-transfer surface.

Investigation of Calcium Carbonate Scaling Inhibition and Scale Morphology by AFM

“…Furthermore, the fouling resistance increases with increasing initial surface temperature in the absence of inhibitors. This inhibitor-free result is consistent with the results obtained by Hasson et al (28) and Turner and Smith (25). An increase in the initial surface temperature will speed up the scaling process due to the increase in both the reaction rate constant and the reaction driving forces (supersaturation).…”

“…The induction period has also been observed by other researchers (24)(25)(26). When the inhibitors were present, the induction periods increased to about 20 and 30 min for 5 mg/L PAA and 5 mg/L PBTCA, respectively.…”

Crystallization of calcium sulfate on polymeric surfaces

“…Surface mineral scaling on polymeric surfaces is of considerable importance in various industrial processes such as those involving heat exchange [1][2][3], mineral processing [4], and membrane desalination via reverse osmosis (RO) and nanofiltration (NF) [5]. Mineral scaling on polymeric surfaces is of particular concern in membrane desalination applications.…”

Fouling Of Nuclear Steam Generators: Fundamental Studies, Operating Experience and Remedial Measures Using Chemical Additives

“…For deposit composed of material with a retrograde temperature-dependent solubility, the deposit will tend to dissolve at the deposit fluid interface and re precipitate at the heat-transfer surface. This phenomenon has been demonstrated with the precipitation of calcium carbonate from a flowing solution onto a heattransfer surface [65] and with the precipitation fouling of magnetite onto the inside surface of SG tubes located in the preheater section of a CANDU SG [66], where the deposit porosity at the heat-transfer surface was estimated to be ~ 5%. The third mechanism proposed for consolidation, boiling induced precipitation, will contribute to deposit consolidation on the secondary side of the SG for deposit on the tube-sheet, on the tube-bundle and at the entrance to the TSPs where flashing is proposed to cause localized boiling and precipitation onto the TSP [67,68].…”