Physicochemical Characteristics and the Scale Inhibition Effect of Air Nanobubbles (A-NBs) in a Circulating Cooling Water System

Abstract

Air nanobubbles (A-NBs) in a circulating cooling water system have not been investigated, although their role is significant. In this paper, the influences of the contents of main salts and other parameters on the physicochemical characteristics and scale inhibition performance of A-NBs in circulating cooling water were investigated and the scale inhibition mechanism of A-NBs in a simulated circulating cooling water system was explored. A-NBs realized a higher scale inhibition rate of 90%, which was higher than that of 1-hydroxyethane-1,1-diphosphonic acid (40%), and A-NBs stably existed for more than 5 days in the complex water environment. Four interface functions were proposed to interpret the scale inhibition effect of A-NBs in circulating cooling water as follows. First, the negatively charged surface of A-NBs adsorbed cations (Ca 2+ ) reduced the concentration of scaling ions. Second, the negatively charged surface of A-NBs could also adsorb microcrystals, and their crystal-like seed action was conducive to the formation of large-size crystals, broke the rules of crystal growth, and reduced the adhesion of scales to the pipe wall. Third, A-NBs could also form a bubble layer after they were adsorbed on the inner surface of pipes, thereby preventing the deposition of scales on the surface. Fourth, A-NB burst caused local turbulence, increased the shear force onto the pipe surface, and reduced the scales adhering to the pipe surface. The interface effect of A-NBs in metal pipes is important in many industrial applications. This study laid the basis for the development of a new green A-NB scale-inhibiting technology.

Optimization on Microbial Anti-Scaling and Corrosion Inhibition Technology for Low Alkalinity and Low Hardness Circulating Cooling Water in Thermal Power Plants

“…Therefore, although the amount of aeration can provide the necessary dissolved oxygen environmental requirements for the experimental functional bacterial agents, due to the low alkali and low hardness of the thermal power plant circulating cooling water in the low oxygen-consuming substances, the microbial oxygen depletion rate by the atmospheric oxygen enrichment rate of the limitation, resulting in the amount of aeration in the microbial technology scale inhibition efficacy of microorganisms is difficult to play a significant role. However, it is worth noting that aeration measures not only provide dissolved oxygen but also provide the necessary shear force to ensure the stability of system homogeneity in the circulating cooling water [9]. Given that the mixing equipment has been used in this experiment to control the uniformity of the system, the experimental results may have underestimated the impact of the aeration parameters on the system, and the operational settings of the equipment and the design of the aeration conditions should be considered comprehensively during the actual application of the technology.…”

“…However, it is also crucial to consider the physical effects generated by this measure. Recent studies report that bubbles from aeration can provide a passivation layer for materials, reducing the contact area between corrosion ions and metal surfaces [12]. Considering the relatively small impact of aeration volume on corrosion inhibition effects for brass and stainless steel 304, the study suggests that in the microbial scale inhibition and corrosion inhibition technology for treating low-alkalinity and lowhardness circulating cooling water of thermal power plants, the mechanism of action of the aeration volume factor in corrosion inhibition is more related to physical effects.…”

Particle Properties of Air Nanobubbles and Their Inhibition Mechanism on Brass Corrosion in Recirculating Cooling Water: Effects of Concentration Ratio and Flow Velocity

“…As a result, the corrosion inhibition of A-NBs decreased. [19] Additionally, the rupture of larger-sized A-NBs generated a certain amount of ─OH, which possessed strong oxidizing properties [28] and promoted the formation of a passivation film on the surface of brass specimens, thereby alleviating corrosion. In a word, as the concentration ratio increased, the corrosion inhibition of A-NBs was closely associated with the ratio of A-NBs concentration to corrosive ion concentration, particle size distribution, A-NBs rupture ratio, and so on.…”

“…The adsorption of ions onto the surface of NBs led to a reduction in the zeta potential of bubbles and significantly decreased the stability of NBs by reducing the energy barrier between them. [ 18–19 ] Conversely, the introduction of ions can decrease the thickness of double layers of NBs, thus leading to a reduction in their size and promoting stability. [ 18–19 ] It is necessary to investigate the particle properties of A‐NBs in composite salt solutions, such as particle size, zeta potential, and stability.…”

Research Progress on Novel Electrochemical Descaling Technology for Enhanced Hardness Ion Removal

“…Scale formation in circulating cooling systems poses several hazards, including (1) scale, being a poor conductor, can impede heat transfer during the circulation process, indirectly affecting production efficiency and, in severe cases, may lead to hazardous events like explosions; (2) scale can reduce the flow area in pipes, increasing fluid resistance and thus energy consumption; (3) excessive scale deposition necessitates shutdowns for cleaning, reducing equipment operational time and efficiency [17][18][19][20][21][22]. Hence, addressing scale formation in CCW is urgent, not only for average industrial production and economic benefits but also for conserving water resources and ensuring industrial safety [23,24].…”