Effect of electric field and Mg2+ doping on calcium carbonate scaling shown in experiments and first principle calculations

Abstract

The effect of electric field applied and Mg2+ doped on formation of calcium carbonatescale in circulating cooling water is investigated by using home-made experimental device, which can simulate the scaleof formationin local power plant. The results showthat high-voltage electrostatic fields and magnesium ions can inhibit scale growthin circulating cooling water. When the magnesium ion concentration is 4 mmol/L, the scale inhibition effect is the best under the action of the electric field (6 kV), and its scale inhibition rate can reach 44.56%. Meanwhile, some phenomenonare explained and confirmed by the results of first-principles calculations. The calculated shear modulus of aragonite is greater than that of calcite. This might be used to explain that aragonite is easier to adhere to the heat exchange surface. This is in good agreement with experimental results. Calcite has better anti-scaling property than aragonite. The crystal structure after physical water treatment is blunt, and the untreated crystal structure is sharp.

Effect of fouling resistance in heat exchanger and the crystal form of CaCO3 in hard circulating cooling water with electrostatic field and alternating current electric field

“…In addition, the XRD spectra of (Mg, Ca)CO 3 and CaCO 3 are identical, supporting the hypothesis that Mg 2þ may enters the calcite lattice. This is consistent with the conclusion of Gao et al (2020). Large amounts of calcite forming on the heat exchanger surface and in solution are beneficial to achieve scale inhibition.…”

“…These results indicate that the hardness of the water affects the treatment effect of the high voltage electrostatic field. Previous studies have shown that the electrostatic field treatment of hard water with high levels of hard ions promotes scaling, while the electrostatic field treatment of artificial hard water with low levels of hard ions showed the effect of scale inhibition (Gao et al 2020).…”

“…It easily adheres to the heat exchanger surface and is difficult to remove. However, block-like calcite has lower adhesive properties than aragonite and can be washed away by water easier (Xing 2008;Tijing et al 2010;Gao et al 2020). Therefore, if aragonite adhesion on the heat exchanger surface is reduced, scale formation inhibition is feasible.…”

“…On the other hand, the treatment of the electromagnetic field not only affected the growth of scale in the heat exchanger but also changed the water quality parameters of the circulating water such as conductivity, pH, turbidity, etc. (Mosin & Ignatov 2015;Gao et al 2020;Lyu et al 2020). In 2020, Lyu et al (2020) studied the effect of alternating electromagnetic field on the thermal resistance, conductivity, pH, and dissolved oxygen of CaCO 3 solution and indicated that the fouling induction period can reach 10,000 minutes at 0.02 T, the scale inhibition effect is the best, and the conductivity can be used as a water quality indicator that reflects the change in fouling resistance.…”

“…By considering Mg 2þ concentration with electromagnetic field or ultrasonic, they can improve the scale inhibition effect and make the CaCO 3 particles gradually change into aragonite (Han et al 2018). Gao et al (2020) indicated that the scale inhibition under the electric field and Mg 2þ is better than that under a single electric field.…”