Circulating Cooling Water System Research Articles

Biofouling behaviors of reverse osmosis membrane in the presence of trace plasticizer for circulating cooling water treatment: Characteristics and mechanisms

Reverse osmosis (RO) system has been increasingly applied for circulating cooling water (CCW) reclamation. Plasticizers, which may be dissolved into CCW system in plastic manufacturing industry, cannot be completely removed by the pretreatment prior to RO system, possibly leading to severe membrane biofouling. Deciphering the characteristics and mechanisms of RO membrane biofouling in the presence of trace plasticizers are of paramount importance to the development of effective fouling control strategies. Herein, we demonstrate that exposure to a low concentration (1 − 10 μg/L) of three typical plasticizers (Dibutyl phthalate (DBP), Tributyl phosphate (TBP) and 2,2,4-Trimethylpentane-1,3-diol (TMPD)) detected in pretreated real CCW promoted Escherichia coli biofilm formation. DBP, TBP and TMPD showed the highest stimulation at 5 or 10 μg/L with biomass increasing by 55.7 ± 8.2 %, 35.9 ± 9.5 % and 32.2 ± 14.7 % respectively, relative to the unexposed control. Accordingly, the bacteria upon exposure to trace plasticizers showed enhanced adenosine triphosphate (ATP) activity, stimulated extracellular polymeric substances (EPS) excretion and suppressed intracellular reactive oxygen species (ROS) induction, causing by upregulation of related genes. Long-term study further showed that the RO membranes flowing by the pretreated real CCW in a polypropylene plant exhibited a severer biofouling behavior than exposed control, and DBP and TBP parts played a key role in stimulation effects on bacterial proliferation. Overall, we demonstrate that RO membrane exposure to trace plasticizers in pretreated CCW can upregulate molecular processes and physiologic responses that accelerate membrane biofouling, which provides important implications for biofouling control strategies in membrane-based CCW treatment systems.

Corrosion behavior and mechanism of carbon steel in industrial circulating cooling water system operated by electrochemical descaling technology

Electrochemical descaling technology (EDT) can significantly increase the concentration ratio of industrial circulating cooling water systems (CCWSs), thereby reducing water, capital, and energy consumption. However, our understanding of the impact of EDT on carbon steel corrosion in CCWSs is limited, which increases the risk of long-term operation. In this study, the influence of the EDT on the corrosion characteristics of carbon steel was comprehensively investigated in field CCWSs (E-CCWSs) and compared with a system using traditional chemical processes (C-CCWSs). The corrosion characteristics, corrosion products, and corrosion mechanism of carbon steel have been studied using various testing methods, including the weight loss method, electrochemical testing, Confocal Laser Scanning Microscopy (CLSM), Advanced Mineral Identification and Characterization System (AMICS), etc. The research showed that the corrosion behavior of carbon steel in a circulating water system was similar and could be divided into three stages: the initial stage (corrosion rate increased), middle stage (corrosion rate slowed down gradually), and later stage (corrosion rate was stable). Owing to the lack of the corrosion inhibitor film, the corrosion rate of carbon steel in the electrochemical circulating water system was faster in the initial stage. However, the rapidly thickened corrosion product layer had a protective effect on the carbon steel. The corrosion of carbon steel entered the middle and late stages faster, and the corrosion rate decreased rapidly and tended to stabilize. In the long term, the corrosion rate of carbon steel in the electrochemical system was slightly lower than that in the chemical system. E-CCWS encounter serious pitting problems. At 120 days, the pitting depth in electrochemical systems was 108.22 μm, almost twice as deep as that in chemicals (54.79 μm). This research has important reference value for corrosion prevention and risk assessment of EDT for practical applications.

Analysis of Microbial Community in Circulating Cooling Water System of Coal Power Plant during Reagent Conversion

The use of phosphorus-containing chemical corrosion and scale inhibitors has been found to result in excessive phosphorus discharge and an inability to reduce the high concentration of CODcr in the circulating cooling water, thereby making it challenging to comply with increasingly stringent sewage discharge standards. This study aims to assess the practicality of utilizing biological corrosion and scale inhibitors in coal power plants’ operation, as well as investigating the correlation between water quality indicators and microbial communities during the conversion period. The data illustrates that, in comparison to the chemical method, there is a decrease in turbidity of the circulating water from 19.44 NTU to 9.60 NTU, a reduction in CODcr from 71.55 mg/L to 45.47 mg/L, and a drop in TP from 2.35 mg/L to 0.38 mg/L. Microbial community analysis during the transition period reveals that microorganisms rapidly establish a new equilibrium in the circulating water, sediment, and fiber ball, resulting in significantly different microbial community structures. The relative abundance of corrosive microorganisms such as Flavobacterium, Pedomicrobium, and Hydrogenophaga is significantly diminished in the circulating water, whilst the abundance of anaerobic microorganisms like Anaerolineaceae and Rhodopseudomonas in the sediment also declines. Conversely, there is an increased presence of microorganisms associated with contaminant degradation, such as CL500-3 and SM1A02. These findings suggest a decrease in the risk of system corrosion and an enhancement in contaminant degradation capability. This study provides evidence supporting the replacement of chemical agents with biological agents in circulating cooling water systems, contributing to more environmentally friendly and sustainable practices.

Method for increasing net power of power plant based on operation optimization of circulating cooling water system

Due to the low power generation performance caused by the unreasonable regulation of the circulating cooling water system (CCWS), a method for increasing the net power of a thermal power plant by optimizing the CCWS operation points was proposed. First, an iterative solver was developed to calculate the stable heat transfer parameters of water circulation processes. Then, the net power model of power plants was established according to the relationship between the CCWS operating points and steam turbine power. Considering the constraints of water flow and the number of pumps in operation, an optimization model with the objective of maximum net power was established. A joint program for solving the objective considering environmental parameters was developed based on artificial neural networks and a hybrid improved particle swarm algorithm. The joint solver could obtain the stable operating temperature of cooling water, the optimal operating point of CCWSs, and the maximum net power of power plants. In addition, the influence of steam load and environmental parameters on optimal solutions was summarized. After executing the operation optimization for a CCWS, the results showed that the net power of typical operating conditions in different seasons increased by 35.85–1423.64 kW, indicating a remarkable effect.

Operation Optimization of Circulating Cooling Water System Based on Adaptive Differential Evolution Algorithm

The circulating cooling water system (CCWS) is a commonly used auxiliary system in industrial production, and it is also one of the main energy-consuming systems. The operating conditions of the system vary with the temperature changes caused by seasons, day and night, causing different energy consumption. If the system still maintains conditions when the actual conditions change, energy would be wasted. Operation optimization for the system can improve the operation effect of the system, reduce energy consumption, and increase operating efficiency. Therefore, through operation mechanism analysis for the main energy-consuming components of the CCWS that has been put into use, an operation optimization model is established integrating the domain knowledge. After that, an adaptive differential evolution (ADE) algorithm is proposed by introducing the adaptive mutation and crossover operator to solve the model. According to the minimum circulating water volume and air volume required by the system under different working conditions, the optimal start-up combination mode and operating frequency of the water pumps and fans are determined. And then, the optimal opening values of the regulating valves and baffles in the system are determined, thereby saving the energy of the system. Considering system operation knowledge, the synchronous optimization of the operation mode and operation status of the components in the system is realized. Finally, the effectiveness of the optimization method is verified through a case study.

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

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 (Ca2+) 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.

Influence of Tubular Turbine Runaway for Back Pressure Power Generation on the Stability of Circulating Cooling Water System

With the increasing maturity of tubular turbine power generation technology, an increasing number of industrial applications use it to recover the rich back pressure energy of a circulating cooling water system (CCWS). However, the influence of tubular turbine runaway on the stability of CCWS is still unclear. This work combines the one-dimensional (1D) method of characteristics (MOC) with the three-dimensional (3D) computational fluid dynamics (CFD), develops a 1D CCWS and 3D tubular turbine coupling simulation method, and simulates the runaway and runaway shutdown processes of tubular turbine under small flow rate condition and large flow rate condition in the real system. Results show that the main operating parameters of the system slightly change when the tubular turbine transitions from the steady state to the runaway condition. The runner’s radial force substantially increases in the runaway condition of the tubular turbine, and the phenomenon of violent oscillation is observed compared with the steady state. During the shutdown process of the tubular turbine runaway condition, the valves in parallel and series with the faulty turbine adopt a reasonable cooperative control strategy, which allows for a smooth recovery of the system operating pressure to the original steady state conditions.

Energy Saving Application of Variable Speed Auxiliary Pump Plus Hydro Turbine in Circulating Cooling Water System

The circulating cooling water system (CCWS) is a common industrial auxiliary system, and water pumps need to consume much energy to transport cooling water to distributed heat exchangers. Previous studies show that a pump network configuration with constant speed auxiliary pump plus hydro turbine (CSAP-T) plays a significant role in energy conservation. However, given the fluctuations in the production load and cooling water supply temperature, the flow demand of heat exchangers for cooling water varies. Under different working conditions, the CSAP-T scheme cannot supply the minimum cooling water flow required by all heat exchangers at the same time, thereby wasting energy. Therefore, this paper proposes a new fluid machinery network configuration called variable speed auxiliary pump plus hydro turbine (VSAP-T) and establishes a mathematical model of the total output power of the fluid machinery network in CCWS to minimize network energy consumption. To illustrate the effectiveness of the VSAP-T scheme, a real system is used as the research object, and both CSAP-T and VSAP-T schemes are used to optimize the system. When the working conditions are changed, the total output power of the system fluid machinery network can be conserved by 30% to 50%.

Gene Regulatory Network Construction Based on a Particle Swarm Optimization of a Long Short-term Memory Network

Background: The Gene Regulatory Network (GRN) is a model for studying the function and behavior of genes by treating the genome as a whole, which can reveal the gene expression mechanism. However, due to the dynamics, nonlinearity, and complexity of gene expression data, it is a challenging task to construct a GRN precisely. And in the circulating cooling water system, the Slime-Forming Bacteria (SFB) is one of the bacteria that helps to form dirt. In order to explore the microbial fouling mechanism of SFB, constructing a GRN for the fouling-forming genes of SFB is significant. Objective: Propose an effective GRN construction method and construct a GRN for the foulingforming genes of SFB. Methods: In this paper, a combination method of Long Short-Term Memory Network (LSTM) and Mean Impact Value (MIV) was applied for GRN reconstruction. Firstly, LSTM was employed to establish a gene expression prediction model. To improve the performance of LSTM, a Particle Swarm Optimization (PSO) was introduced to optimize the weight and learning rate. Then, the MIV was used to infer the regulation among genes. In view of the fouling-forming problem of SFB, we have designed electromagnetic field experiments and transcriptome sequencing experiments to locate the fouling-forming genes and obtain gene expression data. Results: In order to test the proposed approach, the proposed method was applied to three datasets: a simulated dataset and two real biology datasets. By comparing with other methods, the experimental results indicate that the proposed method has higher modeling accuracy and it can be used to effectively construct a GRN. And at last, a GRN for fouling-forming genes of SFB was constructed using the proposed approach. Conclusion: The experiments indicated that the proposed approach can reconstruct a GRN precisely, and compared with other approaches, the proposed approach performs better in extracting the regulations among genes.

Effect of Deposits on Corrosion of Copper Tubes in a Circulating Cooling Water System

Effect of Deposits on Corrosion of Copper Tubes in a Circulating Cooling Water System

Research on the application of compound microorganism preparation in reusing urban reclaimed water in circulating cooling water system.

A biological method was developed for reusing urban reclaimed water in circulating cooling water systems (CCWS), in which the compound microorganism preparation (CMP) mainly included nitrobacteria, Bacillus subtilis, photosynthetic bacteria and Thiobacillus denitrificans, was used to control the scaling, corrosion and biofouling of CCWS. The abundant carbon, nitrogen and phosphorus in urban reclaimed water met the needs of microbial growth. Compared with chemical agents, CMP had the advantages of high efficiency, no additional chemicals and being more economical. The research results showed that CMP improved water quality and decreased ammonia nitrogen (NH3-N) and chemical oxygen demand (COD). The concentration ratio of CCWS reached 3.87 using CMP. The corrosion inhibition rate of CMP and the removal rate on biofouling achieved 99.69% and 22.21%, respectively. The mechanisms of CMP to control scaling, corrosion and biofouling were discussed, and the surface characteristics and chemical compositions of corrosion products and biofouling were analyzed.

Sequential optimization of cooler and pump networks with different types of cooling

A cooler network plays an important role in a heat exchanger network (HEN) in aspects of energy and water conservation, and economic performance of the whole process. However, most studies focus on the circulating cooling water system (CWS), paying less attention to the extensive used various air coolers in industrial practice, including the dry type air cooler (DAC) and wet type air cooler (spray type air cooler (SAC) is a typical example). In addition, the usage of auxiliary pumps in CWS can effectively reduce energy consumption. In this paper, the objective system is a cooler network coupled with the main-auxiliary pump network. In the cooler network, cooling types are considered among CWS, DAC and SAC. Superstructure-based mathematical models are proposed with the minimum total annual cost of the whole system as the objective function. A case study is used to demonstrate the effectiveness of the proposed model, which can obtain the expense reduction with 13% of the cooler network and 32% of the pump network.

Operation optimization research of circulating cooling water system based on superstructure and domain knowledge

Circulating cooling water system (CCWS) is an important auxiliary system in the industrial production process, and it is also one of the main energy-consuming units in the whole process. This paper presents a comprehensive operation optimization method of water and energy, and aims to design an optimal operation plan of the CCWS with improved system operation status and reduced system operation cost. To this end, the operation optimization model based on superstructure method is established, which is comprehensive and practical compared with previous researches in two aspects. Firstly, this model is further extended to realize the comprehensive description and synchronous optimization of network structure, equipment operation mode and equipment operation status, and the optimal operation plan of the system is thus obtained. Secondly, the application range of this model is expanded and thus the proposed method is made more general for various of networks. Moreover, proposed optimization model and the solution algorithm are improved with the fusion of domain knowledge. To be specific, the knowledge of system hydraulic balance and system operation are fused into the operation optimization problem, which improves the energy-saving optimization effect and the algorithm calculation efficiency. Finally, the practicality of the proposed operation optimization method is verified through simulation experiments based on the actual network data, and the comprehensive energy-saving rate reaches 31.3%, so the system operation costs are effectively reduced.

Analysis and Optimization of Open Circulating Cooling Water System

Open circulating cooling water system is widely used in process industry. For a system with a fixed structure, the water consumption and blowdown usually change with the varying parameters such as quality and temperature. With the purpose of water saving, it is very important to optimize the operation strategy of water systems. Considering the factors including evaporation, leakage, blowdown and heat transfer, the mass and energy conservation equations of water system are established. On this basis, the quality and temperature models of makeup and blowdown water are, respectively, developed. The water consumption and discharge profiles and the optimal operating strategy of the open recirculating cooling water system under different conditions are obtained. The concept of cycles of temperature is proposed to evaluate the temperature relationship of various parts of the open circulating cooling water system. A mathematical relationship is established to analyze the influence of the water temperature on the makeup water rate of the system under the condition of insufficient cooling capacity of the cooling tower. In addition, the co-influences of quality and temperature parameters on the system are analyzed.

Study on Biocides of Municipal Middle Water Reused to the Circulating Cooling Water System

This subject used oxidizing biocide C, non-oxidizing biocide Y, and J for single, compound screening, and studied killing performance of them used in municipal middle water. Results indicated that the Y worked best, followed by the J, and C the worst; synergistic biocide P best formula was: J 10 mg/L, and Y 5 mg/L, as this P could be effective in controlling microbial growth.

The Research of the Water Quality Prediction Model for the Circulating Cooling Water System

Aiming at the common quality faults of scaling and corrosion in circulating cooling water, water quality index were often used to determine the scaling and corrosion of circulating cooling water quality trends. Prediction model of corrosion and scaling rate was built based on BP Neural Network in this paper. The optimal initial individuals were written into the network operating system to optimize the disadvantages of weights and thresholds in BP neural network based on genetic algorithm. The prediction function would output after the network training after comparison of predicted and actual values of the model. The performance of the actual situation was verified to match the model prediction.

Application of Physical Polarization Water Treatment Technology on Circulating Cooling Water System of Power Plant

Physical polarization Water Treatment (PPWT) is a new technology that takes advantage of polarization electric field polarizing water molecules to achieve the purpose of scale inhibition and dissolution as well as killing bacteria and algae. The PPWT device made by Shandong Langkun Energy Conservation & Environmental Protection Technology Co., Ltd and running in the biomass power plant of Shandong Kaitai Group Co. achieved the effects of scale inhibition and solution which are even more superior to the traditional method of chemical dosing. It brings annual water conservation of 147600 m3 and economic benefits of hundreds of thousands to millions for forsaking chemical dosing for a 15MW power unit. Therefore, Considerable economic and social benefits and the goals required by the state to the enterprises of energy saving, emission reduction and environmental protection are achieved.

Microbial Population Structure In Circulating Cooling Water System Makeup By Municipal Reclaimed Water

The municipal reclaimed water, which often reused in circulating cooling water system, can effectively alleviate the urban water crisis. However, the reclaimed water contains a large number of microorganisms while the water environment in circulating cooling water system allows the micro-organisms to further increase. Therefore, circulating cooling water system faces slime, corrosion and other microbial problems. In this work, the microbial population structure of circulating cooling water makeup by municipal reclaimed water was investigated by using modern molecular biology DNA technology. Our results demonstrated that at the level of family, there were 17 kinds of suspended microorganisms in municipal reclaimed water, in which the dominant strain belonged to Proteobacteria, Betaproteobacteria, Methylophilales, Methylophilaceae. For the circulating cooling water without chemical agents, 13 kinds of suspended bacterias and 36 kinds of immobilized bacteria were detected, in which the dominant strain respectively was Comamonadaceae and Pseudomonadaceae which belonging to Proteobacteria Betaproteobacteria. After adding chemical agents, the number of suspended bacteria increased to 26 kinds and the distribution of bacteria species was even more. And the dominant strain become Staphylococcaceae, which belonged to Firmicutes, Bacilli, Bacillales, the reason for this was the sharply increase of TOC and TP after adding scale and corrosion inhibitors. Corrosion of instrumentation and pipe network systems caused by microorganisms is particularly complicated in circulating cooling water systems and even in whole reclaimed water utilization systems. The corrosion mechanism and corrosion process caused by different microorganisms are different. Therefore, it is very important to explore the composition of microorganisms in reclaimed water to study the corrosion of microorganisms. Based on the study of microbial population structure in municipal reclaimed water, this paper explores the microbial population structure and dominant species in the water in response to the specific situation in which reclaimed water is reused in the circulating cooling water system. At the same time, it also provides some research suggestions for the future research on the corrosion caused by microorganisms in the reuse of recycled water.