FIG 1 - uploaded by Liwei Zhang
Content may be subject to copyright.
Source publication
Determination of make-up cooling water scaling and corrosion potentials for power plants is essential to prevent cooling system fouling challenges linked to source water quality. In this study, a statistical model is proposed to evaluate the probability that scaling or corrosion could occur. These probabilities were determined from derived distribu...
Contexts in source publication
Context 1
... curves of LSI derived from Equations (9) and (10) Figure 3a-d shows CDF curves and the empirical CDF values of seven measurements of LSI for two river waters (RM 46 and RM 71) and secondary-treated wastewater and tertiary-treated wastewater, respectively. A good fit of the normal CDF with the empirical CDF indicates that the LSI is normally distributed, and the probability of scaling de- rived from normal distribution is valid. A poor fit of the normal CDF with the empirical CDF indicates that the LSI is not normally distributed, and the probability of scaling derived from normal distribution is not valid. The goodness- of-fit between normal CDF and empirical CDF of four types of water was calculated by plotting normal CDF values against empirical CDF values, and the correlation coefficients (R 2 ) of the plots were calculated. The plots and the R 2 values can be found in Supplementary Data (Supplementary Fig. S1). If the R 2 is high, then the LSI is normally distributed. The empirical CDF values of river water RM 46, secondary- treated wastewater, and tertiary-treated wastewater were con- sistent with the CDF curves derived from normal distribution (with R 2 values ‡ 0.9), which demonstrates that the normal distribution can describe the probabilistic distribution of LSI data collected from these waters. The empirical CDF values of river water RM 71 were not as consistent with the CDF curves derived from the normal distribution (R 2 = 0.74), but are still within a moderate level of agreement. Table 1. CDF curves of AI derived from Equations (11) and (12) Figure 4a-d shows CDF curves and the empirical CDF values of seven measurements of AI for two river waters (RM 46 and RM 71), secondary-treated wastewater, and tertiary- treated wastewater, respectively. The empirical CDF values of river water RM 46, secondary-treated wastewater, and tertiary-treated wastewater were consistent with the CDF curves derived from normal distribution, which demonstrates that normal distribution can describe the probabilistic dis- tribution of AI data collected from these waters (see Sup- plementary Fig. S2 in Supplementary Data for details). The empirical CDF values of river water RM 71 were not fully consistent with the CDF curves derived from the normal distribution, but the inconsistencies still lay within an ac- ceptable ...
Context 2
... common types of wet cooling systems currently employed in thermoelectric power plants include once- through and recirculating towers. In once-through cooling systems, cooling water circulated once through the system is directly discharged back to the source. In a recirculating cooling system (shown in Fig. 1), cooling water is circulated from the make-up water basin to the heat exchanger and then to the cooling tower and back to the basin completing one cycle of concentration (CoC). During each flow cycle, evap- oration and drift in the cooling tower cause a decrease in the cooling water quantity, which leads to an increase in the ionic concentrations of the make-up water. To maintain the CoC = 4 or 5 and to ensure that the heat exchanger functions efficiently with minimal fouling, it is necessary for the in- fluent make-up water to have low solid/ion concentrations and organic matter (Vidic and Dzombak, 2009). The focuses of this article are inorganic scale formation caused by high calcium concentration and high alkalinity, and corrosion caused by low pH. However, organic matters in cooling water also play an important role in heat exchanger fouling, because organic matters are food source for microorganisms and the growth of microorganisms results in biofilm formation and subsequent clogging of heat exchanger and reduction of heat- exchange efficiency (Cloete et al., 1998;Meesters et al., ...
Citations
... Using the RSI experimental data reported in the published literature, RSI calculation formula was fitted as in Formula 3 (Ryznar 1944;Changshan et al. 2009;Zhang et al. 2014;Kalyani et al. 2017). ...
The scaling problem exists universally in circulating water systems. Efficient and accurate assessment of scaling tendency is a prerequisite for solving the problem. In this work, it proposes electrolysis to induce hardness variation which connects with the water stability evaluation index for quantitatively assessing the scaling tendency of water. The quantitative assessment is further realized on the basis of qualitative assessment. Then, the dynamic simulation experiments of circulating water are carried out to provide support for the electrolysis-induced hardness variation which clarifies the criteria that can meet the actual water requirements. This work can achieve an efficient and accurate quantitative assessment of the scaling tendency, which is of great significance for solving the scaling problem of circulating water systems.
... Conductivity and pH values were measured using a conductivity meter (FiveEasy FE30, Mettler Toledo, resolution: 0.01 μS/cm) and a pH/ISE meter (PXSJ-216, Inesa, China), respectively. Ryzner stability index (RSI) was used to evaluate the scaling potential of the water in the reservoir simultaneously [28,29]. Repeat experiments were carried out so as to ascertain the accuracy of the results. ...
High cathode area requirement limits industrial applications of electrochemical water softening technology. Based on previous works, the electrochemical water softening mechanism of high-efficient multi-layer mesh coupled cathode which consists of multilayers of stainless steel woven nets with different mesh sizes was studied systematically in this paper. Results reveal that the external and internal layers synergically enhance the performance of the coupled cathode. Calcium carbonate deposition reaction preferentially occurs on the external layers of the coupled cathode, due to the shielding effect caused large differences in current density and potential among the layers of the coupled cathode. Meanwhile, hydrogen bubbles can not only serve as soft templates, allowing nucleation sites to be transferred from the substrate surface to the formed calcium carbonate crystals, but also easily bring scale films with low coverage and adhesion force away from the substrate surface by mechanical stripping, prolonging the cathode deactivation time and making the cathode self-cleaning. Besides, the internal layers provide an alkaline environment through the stable hydrogen evolution process, further accelerating the deposition of hardness ions and reducing the cathode area required for water softening.
... Repeat experiments were carried out so as to ascertain the accuracy of the results. Ryznar stability index (RSI) was used to evaluate the scaling potential of the water in the reservoir simultaneously [33,34]. ...
The high electrode area requirement limited the applications of electrochemical water softening technology, despite of conspicuous advantages. This work introduces an electrochemical water softening system with multi-meshes coupled cathodes to address fouling in industrial circulating cooling water systems. Experimental data indicate that the coupled cathode increases the descaling rate of electrochemical water softening system due to the produced self-synergy effect based on its unique multilayer structure. The synergistic effect is constructed by separating and positioning the chemical reactions (alkalinity production and scale deposition) to different regions of the coupled cathode, thus a large amount of OH ⁻ ions from the internal layers and the preferentially deposited scale on external layers accelerate the subsequent scale deposition in later stage of the process. This system displays the reduced electrode area requirement and energy consumption depending on the increased descaling rate. This work provides a facile strategy for the development and applications of electrochemical water softening technology.
... In most of these studies, the evaluation of corrosion is made using weight loss, while our investigations have been directed towards obtaining information about the kinetics of the process, the morphology of corrosion products, interfacial properties, and the identification of the phases. [5][6][7][8][9][10][11] In conducting the current study, river water was used as corrosive environment (from Bahlui River, Iasi, Romania), and the metallic materials of interest were four mild steels alloys. Iasi is one of the most important and largest cities in Romania, being crossed by Bahlui River. ...
The corrosion processes of mild steel immersed in river water were investigated. The reaction of the Bahlui River on common steel used in domestic and industrial installations was studied. The corrosion of mild steel is an extensive topic approached in different media, yet little information about river water as a corrosive has been reported. The experimental determinations were performed for short term immersion of four alloys in the laboratory. By using Tafel extrapolation and electrochemical impedance spectroscopy, the corrosion of the alloys was investigated. Scanning electron microscopy coupled with energy dispersive x-ray analysis and Fourier-transform infrared spectroscopy were employed to characterize the morphology of corrosion products and dentify their phases. The corrosive activity of river water leads to the formation of inner compact and an outer porous layers. The differences between corrosion products formed in the presence of underground and surface waters are described.
In this paper, the electrochemical ion exchange technology was adopted, and the self-made swirl bed electrochemical ion exchange device was taken as the research object. The results presented that the device had the best water treatment effect with 1:0 of the split ratio and the smaller effluent flow. When the electrochemical device was filled with the mixed ion exchange resin after in-situ regeneration, after 5 h of operation, the hardness removal rates of cathode and anode were 6.25 and 22.5%, respectively. Backwash experiment revealed the treatment effect of power backwash was better than that of large flow backwash.
Limited qualified water resources have necessitated industries to use unconventional water resources such as wastewater. The aim of this study is to evaluate the risk of using urban treated wastewater to replace freshwater as a water source of cooling systems for industrial cooling water consumptions considering three main risks: corrosion, scaling, and biofouling. To perform this research, a risk analysis framework has been developed in three stages: identification of risks and the influential parameters, evaluation of the consequences of failure, and calculation of the probability of failure. The identified parameters were weighted using a paired comparison matrix, and the consequences of failure have been calculated using defined criteria. Questionnaires were used for scoring risks. In this research, the Isfahan Mobarakeh Steel Complex was chosen as the case study. The results of the risk assessment indicated that biofouling failure had the largest score. Furthermore, among the influential major failures, ammonium, phosphate, and chlorine, respectively, had the maximum risk. Based on the results, the developed framework can be used for ranking the risks of using urban treated wastewater instead of freshwater in industrial cooling systems.
