Anti-fouling effect of axial alternating electromagnetic field on calcium carbonate fouling in U-shaped circulating cooling water heat exchange tube

Four indicators, namely, conductivity, fouling induction period (FIP), scanning electron microscopy, and particle size distribution, were adopted in this study based on an online evaluation experimental platform of the electromagnetic anti-fouling effect and an electromagnetic anti-fouling treatment (EAT) device to investigate the anti-fouling effect of axial alternating electromagnetic field with different magnetic induction intensities (i.e., 0, 10, 15, 17.5, 20, 22.5, and 25 mT) on calcium carbonate (CaCO3) fouling in the U-shaped circulating cooling water heat exchange tube. The function model for FIP and magnetic induction intensity was established. Experimental results indicate that the anti-fouling effect was related to the magnetic induction intensity at a specified electromagnetic frequency (i.e., 1 kHz). Moreover, the magnetic induction intensity of 20 mT was considered an inflection point, in which the axial alternating electromagnetic field exhibited the best anti-fouling effect. The following results were obtained at 20 mT in this study. The conductivity increased by 84.87 mu s/cm in average compared with that of the no treatment group. FIP reached a maximum of 10,536 min. The average diameter of CaCO3 particles decreased to 4.04 mu m. In summary, EAT can effectively prevent and mitigate CaCO3 fouling, and the magnetic induction intensity of 20 mT was found to be the best magnetic induction intensity for the EAT device in the current experiment. (C) 2017 Elsevier Ltd. All rights reserved.