Recirculating Cooling Water Research Articles

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

AbstractThe corrosion inhibition performance of air nanobubbles (A‐NBs) is expected to address the environmental problems arising from chemical corrosion. In order to regulate the corrosion inhibition performance of A‐NBs, the particle characteristics of A‐NBs in flowing composite salt solutions are investigated, and the corrosion inhibition effect of A‐NBs under different concentration ratios and rotational speed of simulated circulating cooling water is studied. High salt concentrations significantly reduced the particle size, concentration, and zeta‐potential value of A‐NBs, thus reducing the stability of A‐NBs. The flow velocity has a slight effect on A‐NBs. The results of the weight loss and electrochemical method showed that A‐NBs achieved the highest corrosion inhibition rate of 55% under a concentration ratio of 1.5 and a rotational speed of 100 r min−1. The surface characterization of brass specimens revealed that A‐NBs facilitated the formation of Cu2(OH)2CO3 passivation film, calcium carbonate scale film, and a layer of bubbles on the surface of brass, which subsequently mitigated the erosive impact of the fluid. A‐NBs can adsorb cations and thus reduce the concentration of corrosive ions. However, the increase in concentration ratio and rotational speed impeded the formation of the bubble layer and passivation film.

Assessment of the Impact of Organic Matter Discharge from a Nuclear Power Plant with a Recirculating Cooling Water System

Assessment of the Impact of Organic Matter Discharge from a Nuclear Power Plant with a Recirculating Cooling Water System

S-HGMS coupling with alkali precipitation for the scale inhibition in recirculating cooling water with high hardness: Performance, mechanism and field application

Recirculating cooling water (RCW) contains various scale-forming ions, such as Ca2+ and Mg2+, which tend to form the hard scale in the heat transfer process. In this study, a novel method via superconducting high-gradient magnetic separation (S-HGMS) coupling with alkali precipitation for scale inhibition in RCW was proposed, which could achieve efficient removal of total hardness (91.64 %). The scale inhibition mechanism of the S-HGMS coupling is attributed to the increase of ionic hydration shell thickness and the formation of hydrogen bonds, enhancing the solubility of scale-forming ions and diminishing their nucleation rate. Furthermore, this coupling induces a crystalline transformation from recalcitrant calcite to looser aragonite, contributing to the separation of scale from the pipe wall. Significantly, the proposed method was implemented in the field application by establishing a pilot-scale system with a capacity of 800–1000 L/h, which realized a stable reduction in the total hardness of the RCW from 1270 mg/L to below 127 mg/L at a magnetic flow ratio of 0.05 T·s/m. Moreover, the heat exchanger surface scaling was effectively controlled after 71 days of continuous treatment. This study helps promote the industrial application of S-HGMS technology for scale inhibition in high-hardness water.

Water Conservation: An Innovative Approach towards Minimization of Blow-Down for Recirculating Cooling Water System

Water Conservation: An Innovative Approach towards Minimization of Blow-Down for Recirculating Cooling Water System

Investigation on an electrochemical pilot equipment for water softening with an automatic descaling system: Parameter optimization and energy consumption analysis

Electrochemical water softening (EWS) technology is considered to be a very promising descaling method due to its superiorities in clean, efficient and water-saving ability, although limited by the cleaning of cathode scale. Herein, an innovative EWS device coupled with an automatic descaling module was manufactured and applied to treat the industrial recirculating cooling water (RCW). Response surface methodology (RSM) analysis based on Box–Behnken design (BBD) was applied to optimize the combination effect of four important operation parameters, including initial hardness (1150 mg/L, as Ca2+), ratio of hardness and bicarbonate (0.5), current density (30 A/m2) and circulating water flow (20 m3/h). Next, a mathematical dynamic model was employed to reveal the relationship between the hardness removal percentage and the current density (ρ, A/m2) according to the RSM analysis results. Additionally, various configurations of the device were performed and demonstrated that the integration of automatic descaling system enabled a significant improvement on the descaling capacity (19.95 g/h/m2) and energy consumptions (27.1 kW h/kg CaCO3), which exhibited evident economic and environmental advantages compared to the chemical scale inhibitor method. This work provides a facile strategy for the development and industrial applications of EWS technology.

Effect of pH on the Passivation of Carbon Steel by Sodium Borosilicate Controlled-Release Inhibitor in Simulated Recirculating Cooling Water

A sodium borosilicate controlled-release inhibitor has been prepared via calcination for suppressing carbon steel corrosion in simulated recirculating cooling water (SRCW). The synthesized inhibitor was mainly composed of B2O3 and SiO2, coupling with small quantities of NaB5O6(OH)4·3H2O and NaB5O8·5H2O crystals. The total boron concentration gradually increased to 250 mg L–1 during the 28 days of release (2 g inhibitor in 500 mL SRCW) at 50 °C. A higher controlled-released rate existed in acidic environments (pH 5) than in neutral environments (pH 7) and alkaline environments (pH 9). The potentiodynamic polarization and electrochemical impedance spectroscopy results indicated that the inhibitor showed a better anticorrosion performance in neutral and alkaline environments than in acidic environments. In addition, a passive film with a Fe–O–B structure formed on the carbon steel surface to prevent the attack of the corrosive ions. A passivation-pitting-repassivation process was detected in the passive film...

Inhibition Effect of Environment-Friendly Inhibitors on the Corrosion of Carbon Steel in Recirculating Cooling Water

We studied the corrosion inhibition properties of a combination of polyaspartic acid, polyepoxysuccinic acid, polyamino polyether methylenephosphonate, and sodium gluconate for carbon steel in recirculating cooling water. Characterization employed weight loss measurements, Tafel polarization, electrochemical impedance spectroscopy, X-ray fluorescence (EDX), and atomic force microscopy (AFM). The results show that the composite efficiently inhibited corrosion on carbon steel at relatively low dosages in severely corrosive soft water media. The EDX spectrum determined the nature of the adsorption layer on the steel surfaces. Scanning electron microscopy and AFM further confirmed the formation of a protective film on the carbon steel surface.

Design of the Reclaimed Water Reuse Project for Recirculating Cooling Water in a Thermal Power Plant

The paper introduced the design parameters of a reclaimed water island engineering in a power plant. The total processing scale was 3.84×104m3/d. The raw water source of this project was the further treated wastewater from municipal treatment plant. The combination of BAF-Lime Conglomeration and Clarification-Filtration was employed in the design for advanced treatment. The operation results showed that the quality of treated water with this process in the reclaimed water island could satisfy the design requirement and the treated water was reused as recirculating cooling water in a thermal power plant.

Effect of Inorganic Ions on Biofilms Component and Activity in the Recirculating Cooling Water System

In this research a laboratory model recirculating cooling water system was applied to investigate the effects of four kinds of inorganic ion concentrations on extracellular polymeric substances (EPS) content, the ration of proteins and polysaccharides ratio in EPS (PR/PS) and dehydrogenase activity (DHA) in the attached biofilms. The results showed that the low Na+ concentration was beneficial to EPS production and biofilms DHA. With Ca2+ concentration increasing, EPS content first increased and then decreased as a whole. Mg2+ showed no obvious effect on biofilms EPS content, while had the effect on PR/PS and DHA. The increase of Fe3+ concentration was beneficial for EPS formation and DHA when Fe3+ concentration was below 1.5 mg/L.

Integrated process control for recirculating cooling water treatment in the coal chemical industry

This work focused on the integrated process of the recirculating cooling water (RCW) treatment to achieve approximate zero emission in the coal chemical industry. The benefits of fractional and comprehensive RCW treatment were quantified and qualified by using a water and mass balance approach. Limits of cycle of concentrations and some encountered bottlenecks were used to ascertain set target limits for different water sources. Makeup water was mixed with water produced from reverse osmosis (RO) in the proportion of 6:4, which notably reduced salts discharge. Side infiltration, which settled down suspended solids, can reduce energy consumption by over 40%. An automated on-line monitoring organic phosphorus inhibitor feed maintains the RCW system stability in comparison to the manual feed. Two-step electrosorb technology (EST) instead of an acid feed can lead cycle of concentration of water to reach 7.0. The wastewater from RO, EST and filter was transferred into a concentration treatment system where metallic ions were adsorbed by permanent magnetic materials. Separation of water and salts was completed by using a magnetic disc separator. Applying the integrated process in a coal chemical industry, a benefit of 1.60 million Yuan annually in 2 years was gained and approximate zero emission was achieved. Moreover, both technical and economic feasibility were demonstrated in detail.

Corrosion Inhibition of Carbon Steel in Open Recirculating Cooling Water System of Petroleum Refinery by Thiourea and Imidazole in Presence of Zinc (II) Sulphate

The inhibiting action of thiourea and imidazole towards corrosion for carbon steel in open recirculating cooling system (ORCS) of Numaligarh Refinery Limited (NRL) , Golaghat , Assam,India has been studied in presence of Zn2+(as ZnSO4.7H2O) by weight loss and potentiodynamic polarization methods. The values of inhibition efficiency from weight loss method are in good agreement with those obtained from polarization studies. Polarization study indicates that imidazole retards the cathodic corrosion reaction where as thiourea inhibits anodic corrosion reaction in these particular blends of inhibitors. SEM and EDS study confirm the formation of an adsorbed protective film on the carbon steel surface.

Effect of coagulation pretreatment on membrane distillation process for desalination of recirculating cooling water

The objective of this work was to study the performance of coagulation pretreatment and the effect of coagulation pretreatment on membrane distillation (MD) process for desalination of recirculating cooling water (RCW). In this study, RCW was desalinated by MD process after pretreated by coagulation, precision filtration, acidification and degassing. Pre-coagulation of RCW with poly-aluminum chloride (PACl) coagulant improves the elimination of total organic carbon (TOC), total phosphorus (TP) substances. The optimized pH value and PACl dosage were 7 and 15 mg/L, respectively. Compared with MD process without coagulation pretreatment, much slighter MD flux decrease was observed when coagulation pretreatment was employed for desalination of RCW using MD process. Compared with the membrane flux of MD process for the RCW without coagulation pretreatment, about 23% improvement of MD flux was obtained by employing coagulation pretreatment after 30 days operation. The variation of crystal morphology on membrane surface and hydrophobic character of PVDF hollow membranes were investigated. The results show that distorted rhombic magnesium-calcite scale formed on membrane surface when coagulation pretreatment was employed. However, the deposited magnesium-calcite on the membrane surface was loosely packed with particles of much smaller size when RCW without coagulation pretreatment was fed. It is because that the coagulation pretreatment removed most of the natural organic matter (NOM) and antiscalant additives in RCW, which act as an inhibitor to calcium carbonate crystal growth in water. After coagulation pretreatment, bigger crystal deposit formed on membrane surface with the increase in CF of RCW. It was rather difficult for bigger crystal to enter membrane pores and thus the formation of bigger crystal reduced partial wetting of membrane, which enhanced trans-membrane flux. The hydrophobic character of PVDF hollow membranes used in MD process can be easily recovered by chemical rinsing using acid–base solutions. The results indicate that the pretreatment with chemical coagulant, PACl, is effective for the desalination of RCW by MD process.

Integration of direct contact membrane distillation and recirculating cooling water system for pure water production

A novel cleaner production technology (CPT) using waste heat for pure water production was established by integration of direct contact membrane distillation (DCMD) and traditional recirculating cooling water (RCW) process. The effect of temperature difference and flow rate of fluid between the hot and cold sides in a membrane module on the membrane flux was investigated. The results of the study show that the membrane flux increases with an increase in the flow rate in both hot and cold sides and also increases linearly with the increase in fluid temperature difference between the hot and cold sides of the membrane module. Waste heat was utilized for pure water production, which will reduce the pure water production cost. The employment of DCMD in the RCW process may also reduce the amount of scale and corrosion inhibition additives needed in the CPT, the makeup water and blowdown quantity.

Superstructure-Based MINLP Formulation for Synthesis of Re-Circulating Cooling-Water Networks with Intermediate Mains

A novel superstructure-based MINLP formulation is proposed for the synthesis of cooling water networks with intermediate mains. The proposed mathematical model considers the generic problem confronted in the design of a recirculating cooling-water system, including stretching the cooler network design and setting the operation constraints. Besides the original design items, this research probes into how the number of intermediate cooling-water mains influences the performance of a recirculating cooling-water system. We also study how the conditional direct connections between cooling units can decrease the consumption of the recirculating cooling-water with a little sacrifice of pipeline complexity. Typical representative examples are presented to demonstrate the viability of proposed superstructure-based MINLP formulation. Supported by the results of computer analysis, the network superstructure and its design scheme can effectively accomplish the goal of unraveling the design problem of the recirculating cooling-water system with intermediate cooling-water mains, and proffering the optimal structure in designing the recirculating cooling-water systems.

Corrosion and Scale Inhibition Properties of Sodium Lignosulfonate and Its Potential Application in Recirculating Cooling Water System

The corrosion and scale inhibition properties of sodium lignosulfonate (SL) were investigated by determining the corrosion and scale inhibition efficiency, the polarization curve, the residual turbidity, and the polymorph of calcium carbonate (CaCO3) scale. It is found that, to a certain degree, SL has a positive corrosion inhibition effect at the higher dosage, whereas it accelerates the corrosion of carbon steel at the lower dosage. SL also has a good dispersibility to CaCO3, causing a small CaCO3 scale inhibition efficiency of maximum value of 2.5% at a dosage of 50 mg/L SL. Because there exist intrinsic limitations of SL without modification as a water treatment agent in a cooling water circulation system, the original SL was further chemically modified by grafting with acrylic acid monomer. The modified SL increases its negative charge density and hence an adsorption quantity on the active anodic sites in the electrochemical reaction. The corrosion inhibition efficiency of modified SL is consequently...

Seasonality of cooling tower drift in vegetation at ORGDP

Cooling tower operation at the Oak Ridge Gaseous Diffusion Plant (ORGDP) requires the addition of a chromated corrosion inhibitor to the recirculating cooling water (RCW) system. Fluctuations in the RCW flow rates of the ORGDP cooling towers correlates with operational levels of the enrichment plant. Drift fraction is a function of the RCW flow rate, with variations in chromium deposition reflected in vegetation contamination. Fescue grass and litter were collected in the plant environs along a distance gradient, during different seasons, and analyzed for chromium. Foliar chromium concentrations were maximum (1390 μg/g) during the winter months, decreasing in spring and summer months (190 and 173 μg/g, respectively) at 13 m as the demand for cooling decreased with lower plant operations. In contrast, concentrations in litter increased with time, ranging from 894 μg/g at 13 m during the winter to 1890 and 2140 μg/g during the summer and fall months. The accumulation of chromium in the litter component was likely related to more exchange sites associated with increased litter biomass due to the seasonal senescence of foliage, whereas decreased accumulations on foliage reflected high mobility of the drift residue due to leaching and a short lifespan of individual leaves. In addition to operational considerations, the data illustrate the importance of seasonal considerations in the use of biological materials in a monitoring program.

Improved Laboratory Technique for Investigating Corrosion by Recirculating Cooling Water

Abstract A description of an improved testing loop for the evaluation of cooling water corrosion inhibitors for open recirculating systems is given, together with the performance characteristics of the laboratory apparatus. The test equipment included heat transfer surfaces and permitted velocities of 2 to 3 feet per second. Corrosion rate comparisons are made with data previously obtained in a screening test loop operated under less severe test conditions. Attempts are made to detect the extent of scale build-up on heat transfer surfaces through losses in heat transfer and increased friction losses in the system. Results indicate that scaling and fouling characteristics of inhibited open cooling water systems were not satisfactorily measured in the apparatus described.

Water Utilization and Treatment Efficiency Of Gulf Coast Cooling Towers—A Report of the Recirculating Cooling Water Work Group Of NACE Task Group T-5C-1 on Corrosion by Cooling Waters (South Central Region)

Water Utilization and Treatment Efficiency Of Gulf Coast Cooling Towers—A Report of the Recirculating Cooling Water Work Group Of NACE Task Group T-5C-1 on Corrosion by Cooling Waters (South Central Region)