Re-circulating Cooling Water Systems Research Articles

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

INTEGRAL METHODS FOR CONTROL OF COMPLEX PROCESSES IN NPP COOLING SYSTEMS

The relevance of the study is to ensure the reliable operation of NPP recirculating cooling water systems (RCWS) and select the method for discharge water conditioning. The purpose of the study is to provide scientific and technical substantiation of conditions that will effectively provide and improve the reliable and efficient long-term operation of NPP RCWS equipment. The study included analysis of main factors that influence the efficient and reliable performance of heat exchangers, and of modern scientific and technical approaches to study water-chemical regimes (WCR) of operating RCWS systems for preventing depositions of sparingly soluble salts and corrosion of power equipment, to study thermal-hydraulic regimes (THR) in RCWS WCR laboratory simulation, and to study the deposition rates on heat exchange surfaces (HES). The improvements refer to gas chromatography technique to control the content of oil product in water; the process flow diagram for the floor drain radioactive water treatment; methods of discrete control over RCWS operational efficiency with monitoring THR and WCR indicators, and deposition rates during laboratory studies and industrial tests. The obtained results make it possible to carry out a scientific and technical substantiation of the conditions for effective implementation of RCWS structural reconfigurations in order to increase the installed capacity factor (ICF) and for economical use of water during the variable loads on individual power units of large power facilities, considering their installed capacity, service life, and heat exchange equipment condition due to the use of separate RCWS with individual THR, WCR, and established individual standards for the amount of blowdown water and its possible reuse as makeup water for power units.

A comprehensive synthesis approach of re-circulating cooling water system based on stage-wise structure and Poppe method

Most studies in re-circulating cooling water system(RCWS) synthesis principally focused on configurations and economic optimizations but ignored the water and air evaluation in the cooling tower. This study proposes a comprehensive RCWS synthesis method based on stage-wise structure and the Poppe method to optimize the economic cost and determine the cooler configurations while simultaneously evaluating the water and air parameters. The closed-loop issues manipulation and differential evolution algorithm are applied for calculating the iteration process for unsaturated and supersaturated air conditions. The validation and case study are presented to confer the discrepancies between the proposed and previous models. Then different types of matching, comparison of different tower inlet limit temperatures, and makeup temperatures are proposed to explain the discrepancy of tower calculation methods and stage numbers. The validation and discussion show that the TAC calculations for the four cases are reduced by about 4% and the outlet air temperature of the Poppe method is about 2 °C lower than the Merkel method, with a supersaturated state. This study proposes a comprehensive approach for RCWS accurate synthesis problems.

Macrolepiota-mediated synthesized silver nanoparticles as a green corrosive inhibitor for mild steel in re-circulating cooling water system.

A simple, cost effective and eco-friendly silver nanoparticle (AgNPs) was synthesized by wild edible Macrolepiota mushroom. Nanoparticles were characterized by UV-visible, FTIR, XRD analysis and TEM analysis. The characterized studies confirmed the spherical shape of AgNPs with 20-50nm size. Biocorrosion efficacy of myco-synthesized AgNPs and the mushroom extract were tested against mild steel by corrosive bacteria Bacillus thuringiensis EN2, Terribacillus aidingensis EN3 and Bacillus oleronius EN9. Weight loss analysis, EIS, and surface analysis were used to evaluate the corrosion inhibition efficiency of mild steel in various experimental systems. Reduced corrosion rate (0.07mm/y, 0.14mm/y), reduced weight loss (0.006 ± 2, 0.011 ± 2) and increased corrosion inhibition efficiency (59%, 18%) were identified in both system II and system IV. Peak intensity was reduced in both surface analysis studies (FTIR and XRD) in the presence of mushroom extract and AgNPs. EIS studies reveal that the mushroom extract and AgNPs act as a corrosive green inhibitor and adsorbs on the mild steel surfaces in cooling water tower system, which are responsible for corrosion protection.

Heat and mass transfer performance and exergy performance evaluation of seawater cooling tower considering different inlet parameters

Cooling towers are important components within re-circulating cooling water systems. Due to a shortage of freshwater resources, seawater cooling towers are widely used both in manufacturing and everyday life. This paper researches the mechanical draft counterflow wet seawater cooling tower, and establishes and verifies a detailed thermal performance calculation model. Referring to the Second law of thermodynamics, the heat and mass transfer performance and exergy performance of the seawater cooling tower were studied. The effects of salinity, inlet air speed, and air wet-bulb temperature on the cooling efficiency, thermal efficiency, and exergy efficiency were analyzed. The results show that compared to the air wet-bulb temperature, changes in air speed have more influence on cooling and thermal efficiency under the study conditions. Moreover, the air wet-bulb temperature is the significant parameter affecting exergy efficiency. With an increase in salinity, the cooling, thermal, and exergy efficiency are about 2.40-8.25%, 1.06-3.09%, and 2.47-7.73% lower than that of freshwater, respectively, within an air speed of 3.1-3.6 m/s. With an increase in salinity, the cooling, thermal, and exergy efficiency are about 2.28-8.47%, 1.03-3.37%, and 2.44-7.99% lower than that of freshwater, respectively, within an air wet-bulb temperature of 25-27?. Through the exergy analysis of the seawater cooling tower, it is obvious that the heat and mass transfer performance and exergy performance can be improved by selecting the optimum operating conditions and appropriate packing specifications.

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

Long alkyl-chain imidazolium ionic liquids: Antibiofilm activity against phototrophic biofilms

Biofilm formation is problematic and hence undesirable in medical and industrial settings. In addition to bacteria, phototrophic organisms are an integral component of biofilms that develop on surfaces immersed in natural waters. 1-Alkyl-3-methyl imidazolium ionic liquids (IL) with varying alkyl chain length were evaluated for their influence on the formation of monospecies (Navicula sp.) and multispecies biofilms under phototrophic conditions. An IL with a long alkyl side chain, 1-hexadecyl-3-methylimidaazolium chloride ([C16(MIM)][Cl]) retarded growth, adhesion and biofilm formation of Navicula sp. at concentrations as low as 5μM. Interestingly, [C16(MIM)][Cl] was very effective in preventing multispecies phototrophic biofilms on fibre reinforced plastic surfaces immersed in natural waters (fresh and seawater). SYTOX® Green staining and chlorophyll leakage assay confirmed that the biocidal activity of the IL was exerted through cell membrane disruption. The data show that [C16(MIM)][Cl] is a potent inhibitor of phototrophic biofilms at micromolar concentrations and a promising agent for biofilm control in re-circulating cooling water systems. This is the first report that ionic liquids inhibit biofilm formation by phototrophic organisms which are important members of biofilms in streams and cooling towers.

Hydroxyl carboxylate based non-phosphorus corrosion inhibition process for reclaimed water pipeline and downstream recirculating cooling water system

A combined process was developed to inhibit the corrosion both in the pipeline of reclaimed water supplies (PRWS) and in downstream recirculating cooling water systems (RCWS) using the reclaimed water as makeup. Hydroxyl carboxylate-based corrosion inhibitors (e.g., gluconate, citrate, tartrate) and zinc sulfate heptahydrate, which provided Zn2+ as a synergistic corrosion inhibition additive, were added prior to the PRWS when the phosphate (which could be utilized as a corrosion inhibitor) content in the reclaimed water was below 1.7mg/L, and no additional corrosion inhibitors were required for the downstream RCWS. Satisfactory corrosion inhibition was achieved even if the RCWS was operated under the condition of high numbers of concentration cycles. The corrosion inhibition requirement was also met by the appropriate combination of PO43− and Zn2+ when the phosphate content in the reclaimed water was more than 1.7mg/L. The process integrated not only water reclamation and reuse, and the operation of a highly concentrated RCWS, but also the comprehensive utilization of phosphate in reclaimed water and the application of non-phosphorus corrosion inhibitors. The proposed process reduced the operating cost of the PRWS and the RCWS, and lowered the environmental hazard caused by the excessive discharge of phosphate. Furthermore, larger amounts of water resources could be conserved as a result.

Comprehensive utilization of phosphate in a highly concentrated recirculating cooling water system using secondary-treated municipal wastewater as make-up

A comprehensive utilization process using phosphate was developed for the reuse of high hardness secondary-treated municipal wastewater to a highly concentrated recirculating cooling water system (RCWS). It showed that the soluble phosphate in the wastewater could be directly reused as a corrosion inhibitor to prevent the RCWS from severe corrosion caused by the contaminants in the wastewater. Based on the synergetic corrosion inhibition of PO43- and Zn2+, a chemical program was achieved for recirculating cooling water treatment. It contains 1-hydroxyethylidene-1,1-diphosphonic acid, polyepoxysuccinic acid, zinc sulfate heptahydrate, and a copolymer dispersant of LN-104B. In addition, LN-104B was verified to have excellent inhibition capability to calcium phosphate scale and zinc salts scale in the bench experiments. The pilot-scale experimental results showed that the simulated RCWS operated very well under the condition of high Ca2+ concentration (1,500 mg/L as CaCO3) using the chemical program and automatic pH-controlled technique. The corrosion rate and the adhesion rate of the test tubes are only 0.023 mm/a and 2.32 mcm, respectively, which perfectly meet the requirements of the international standard of ISO 16784-2006. Not only can the process cut down the operating cost of RCWS, but also can reduce the environmental risk caused by excessive emission of phosphate. Moreover, large amounts of fresh water and phosphorus resources are expected to be conserved.

English

An important area in process integration is the development of methodologies to minimize water and energy use in industry. More than 20 % of the energy consumption in industry is associated with cooling and heating water. This paper presents analysis and optimization of a re-circulating cooling water system, with the aim to satisfy any supply conditions for the cooling tower. The part of the atmospheric crude oil distillation unit was chosen for analysis and synthesis of cooling water systems by the Kim and Smith design (KSD) method. The load of the cooling tower and the cost related to the cooling water system could be reduced by modifying the configuration of the heat exchanger network. In this paper, the KSD methodology for a developed heat exchanger network is expanded with the principle based on the heuristic algorithmic water sources diagram procedure (WSD) to synthesize the mass exchange network. These procedures are advantageous compared with other methodologies since hand calculation is used, a very useful feature for process engineers. The cooling water network was synthesized, leading to a 40 % reduction in cooling tower load, and consequently, lower operating costs and water consumption.

Simultaneous water and energy conservation through graphical and mathematical programming: a case study for float glass industry

This paper represents a systematic approach for the synthesis of re-circulating cooling water systems consisting of a cooler network and a cooling tower network of a float glass process industry. A unique combination of graphical and mathematical programming technique of water pinch was used to revamp the existing water and energy network. Total nine different types of methods including Aspen Water used to develop nine different integrated water and energy networks with a payback period of around 8–11 months which clearly reflects that all the WENs are techno-commercially viable. There will be a reduction in consumption of makeup water in tune of 15–65% and savings in energy will be around 34–52%. There will be an overall reduction of 13–35% in terms of cost.

Synthesis of cooling water systems with multiple cooling towers

This paper presents a systematic approach for the synthesis of re-circulating cooling water systems consisting of a cooler network and a cooling tower network (i.e. a general arrangement of multiple interconnected cooling towers with different supply temperatures). An overall superstructure is developed, which contains all the different alternatives for the cooler and cooling tower networks, as well as all their potential interconnections for fixed data of hot process streams. The synthesis problem is formulated as a mixed integer nonlinear programming problem. The continuous variables include the flow rates and temperatures of the circulating cooling water in the superstructure while the integer variables describe the existence of the coolers and the cooling towers. The objective function is to minimize the total annual cost, which includes the investment costs of cooler units and cooling towers, as well as the operating costs due to make-up water and power consumption of the circulating-water pumps and cooling tower fans. The solution of the proposed MINLP formulation provides simultaneously both the optimal configuration and operating conditions of the cooler and cooling tower network to comply with given process cooling demand at minimum total annual cost. One of the most important design variables is the number of cooling water sources (i.e. cooling water streams at different temperatures originated from the outlets of cooling towers) for removing heat from several hot process streams at different temperature ranges. Results show that cooling systems consisting of multiple cooling towers with different supply temperature yield significant better results than traditional systems with a cooler network in parallel arrangement that is supplied with cooling water from a single cooling tower.

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.

Optimization model for re-circulating cooling water systems

This paper presents an optimization model for the simultaneous synthesis and detailed design of re-circulating cooling water systems. A cooler network superstructure that embeds all network configurations of practical interest is used as part of the integrated model. Pressure drops in each cooler are treated as optimization variables, and design guidelines and constraints are included in order to provide practical and feasible units. The model is based on a generalized disjunctive programming formulation, which gives rise to a mixed-integer nonlinear programming problem. The objective is to find cooling water systems that minimize the total annual cost. Solution of this mathematical formulation provides the optimal system configuration as well as the optimal operating conditions and design parameters required for each cooler unit in the network and in the cooling tower. Three example problems are presented to show the application of the proposed approach.

Application of ozone treatment and pinch technology in cooling water systems design for water and energy conservation

Re-circulating cooling water systems offer the means to remove heat from a wide variety of industrial processes that generate excess heat. Such systems consist of a cooling tower and a heat-exchanger network that conventionally has a parallel configuration. However, reuse of water between different cooling duties allows cooling water networks to be designed in a series arrangement. This results in performance improvement and increased cooling tower capacity. In addition, by the integration of ozone treatment into the cooling tower, the cycle of concentration can be increased. The ozone treatment also dramatically reduces the blow-down that, in turn, is environmentally constructive. In this study, a new environmental-friendly and cost-effective design methodology for cooling water systems was introduced. Using this design methodology, Integrated Ozone Treatment Cooling System (IOTCS), achievement of minimum environmental impacts and total cost were afforded through a simultaneous integration of the cooling system components using an ozone treatment cooling tower and optimum heat-exchanger network configuration. Moreover, in the proposed method, the cooling tower optimum design was achieved through a mathematical model. The IOTCS design method is based upon a complex design approach using a combined pinch analysis and mathematical programming that provides an optimum heat-exchanger configuration while maximizing water and energy conservation and minimizing total cost. Related coding in MATLAB version 7.3 was used for the illustrative example to obtain optimal values in the IOTCS design method computations. The results of the recently introduced design methodology were compared with the conventional method. Copyright © 2009 John Wiley & Sons, Ltd.

Optimum design of cooling water systems for energy and water conservation

Re-circulating cooling water systems (RCWSs) are widely used to reject waste process heat to the environment, conserve fresh water and reduce thermal pollution relative to once-through systems. Research on RCWS has mostly focused on individual components, cooling tower and heat-exchanger network. Kim and Smith [Kim, J.K. and Smith, R., 2001, Cooling water system design, Chem Eng Sci, 56(12): 3641–3658] developed a grass-root design method of RCWS (KSD). In this paper, the KSD method is expanded and a comprehensive simulation model of RCWS is developed accounting for interaction between cooling tower and heat-exchanger network. Regarding this model, a modern grass-root design method of RCWS, we call it Advanced Pinch Design (APD), based on combined pinch technology and mathematical programming is developed for minimum cost achievement. Having considered cycle water quality through introducing ozone treatment technology, APD methodology is further improved. This technique that we call Enhanced Cooling Water System Design (ECWSD), as the APD supplementary methodology, is provided water and energy conservation, minimum cost and environmental impacts. Related coding in MATLAB version 7.1 is developed for the illustrative example to get optimal values in RCWS design method computations. Finally the results of the introduced grass-root design methodologies, APD and ECWSD, are compared with KSD.

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...

Cooling water system design

Research on cooling systems to date has focussed on the individual components of cooling systems, not the system as a whole. Cooling water systems should be designed and operated with consideration of all the cooling system components because of the interactions between cooling water networks and the cooling tower performance. In re-circulating cooling water systems, cooling water from the cooling tower is supplied to a network of coolers that usually has a parallel configuration. However, re-use of cooling water between different cooling duties enables cooling water networks to be designed with series arrangements. This allows better cooling tower performance and increased cooling tower capacity, both in the context of new design and retrofit. A methodology has been developed for the design of cooling networks to satisfy any supply conditions for the cooling tower. A model of cooling tower performance allows interactions between the performance of the cooling tower and the design of cooling water networks to be explored systematically. In debottlenecking situations, better design of the cooling network using the new method, including increasing cooling tower blowdown, taking hot blowdown and strategic use of air coolers, can all be used to avoid investment in new cooling tower capacity and to improve the performance of the cooling tower in a systematic way.