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Electrode configuration is a key parameter that affect the operation of ESPs. In this study, through a wire-plate ESP at wide temperatures, the dynamic and ultimate removal characteristics of coal-fired power plant and coal pyrolysis furnace fly ash (ash A and B) with different resistivity under four electrode configurations were investigated. For ash A, the sawtooth electrode DE3 exhibited the largest current density under identical applied voltage. Each discharge electrode configuration had its efficient operating temperature. DE3 had the best removal performance when the temperature was 363 K and DE1 performed excellently at 500 K. For ash B, the removal efficiency with rod electrode DE4 was only 91.2% at 700 K in the simulated inert atmosphere. Through the optimization of electrode configuration with DE1, particles were effectively removed with collection efficiency exceeding 95%, and the particle removal efficiency of each diameter distribution was remarkably higher than that of DE4. Unlabelled Image • Four different electrode configurations were conducted to enhance the performance of ESP at high temperature. • The dynamic and ultimate removal characteristics were investigated. • The barbed electrode performed relatively best to remove particles at high temperatures. • A discharge electrode optimization with temperature regulation method was proposed. [ABSTRACT FROM AUTHOR]

Electrostatic precipitators (ESP) have been considered as the main particulate matter (PM) removal facility in the energy industry. This paper presents a real-time optimization method for a one-chamber industrial ESP in an ultra-low emission power plant with an intelligent optimization system (IOS). The IOS seeks to optimize the energy consumption of ESP subject to the outlet concentration requirement in real-time. A coordination control logic is designed to regulate the optimized operation set points with varying operation conditions. The operation optimized by the IOS is compared with the operations under PID (proportion-integral-derivative) and manual control. The results show that the IOS improves the emission compliance rate from 95% of manual control to 100% and the medium concentration is tuned to be 46.6% closer to the emission target. Furthermore, a good balance between emission and energy consumption is achieved, with 35.50% energy conservation for the same emission upper limit of 30 mg/m3. These results prove that the IOS significantly contributes to the efficient operation and economic PM removal by ESP for the energy industry. Electrostatic precipitators (ESP) is one of the main PM removal facilities in coal-fired power plants. An intelligent optimization system (IOS) with prediction, optimization, and control modules is designed and constructed for the ESP in an ultra-low emission power plant. A PM removal model is used to predict the outlet concentration of the ESP. The optimal energy consumption of ESP subject to the outlet concentration requirement problem is solved by the particle swarm optimization. A closed-loop and rapping tolerant method is used to eliminate the fluctuation in time-averaged concentration. The system raised is able to ensure the compliance rate while decreasing the energy consumption of the ESP. [ABSTRACT FROM AUTHOR]

Highlights • SO 3 formation and phase transformation mechanism in coal-fired plants are studied. • The adverse effects of SO 3 on the utility operations and environment are analyzed. • Different SO 3 test standards and measurement methods are compared. • Various SO 3 control technologies are reviewed and compared. • Future trends of SO 3 emission limits and control strategies are prospected. Abstract The formation and emission of sulfur trioxide (SO 3) in coal-fired power plants has received increasing attention due to its adverse effects on the operation of plant and environment. With the wide application of selective catalytic reduction (SCR) systems, the problem caused by SO 3 has become severe, especially when high sulfur coal is burned. Emission regulations of SO 3 for coal-fired power plants, which promote the development of SO 3 measurement and control technologies, have been set in some countries and regions. In this paper, recent advances in the formation, transformation, measurement, and control mechanism and technologies of SO 3 in coal-fired power plants were summarized. The formation mechanisms of SO 3 in boiler and SCR systems and its form transition and corresponding effects on the performance of power plants were analyzed. Different SO 3 test standards and methods were compared, and online SO 3 monitor based on isopropanol absorption method were developed. Various SO 3 control technologies, including simultaneous and specific removal technology, were summarized. Low-low temperature and wet electrostatic precipitators could remove up to 90% SO 3 /H 2 SO 4 aerosol, and the removal efficiency of SO 3 in wet flue gas desulfurization can be enhanced to 80% by absorber optimization and inlet flue gas temperature decrease. For power plants that burn high-sulfur coal, the injection of alkaline sorbent before the SCR or air preheater system can remove more than 90% of SO 3 to decrease the formation of NH 4 HSO 4 and the pressure drop in the air preheater. High SO 3 removal technology and strategies for different scenarios were proposed to meet different SO 3 emission requirements in the future. [ABSTRACT FROM AUTHOR]

Abstract Sulfur trioxide (SO 3) pollution is becoming another severe problem in coal-fired power plants after SO 2 , NOx, and PM, however, the characteristics of SO 3 emission in China remains unclear. In this paper, we established a refined activity data, and summarized the removal efficiency of different control technologies according to the literature review and field test results. An emission inventory of SO 3 from coal-fired power plants in China between 2009 and 2014 was developed, which indicated the SO 3 emission increased from 199.7 kilotons (kt) to 314.6 kt at an average annual growth rate of 9.7%. The results show that Neimenggu, Shānxi, Jiangsu, Shandong, Guangdong and Guizhou were the largest emitters, accounting for 49.7% of the total SO 3 emissions in 2014. We analyzed the historical data with ArcGIS system, which allocates the emission into 36 km × 36 km grid cells. In addition, the result shows the unevenly spatial distribution. Combined with future economic development as well as implementation of policy, three different scenarios were set to project SO 3 emission in coal-fired power plants in 2020, which represented the potential of SO 3 emission reduction. Compared with scenario A, SO 3 emission can be reduced to 83.9 kt in scenario B, and in scenarios C, SO 3 emission can be reduced to 38.4 kt. Coal-fired power plants should adopt different technology routes to meet the ultra-low emission requirement and reduce the SO 3 emission according to the boiler type, sulfur content, and the emission standard. Highlights • The first SO 3 emission inventory of coal-fired power plants developed in the Period 2009–2014 in China. • Variations in regions and source characteristics were investigated and analyzed. • Uncertainties of inventory were assessed in a quantitative way. • Scenarios were set to project SO 3 emission for the year 2020, which present the potential of the emission reduction. [ABSTRACT FROM AUTHOR]

Aiming at enhanced particulate matter (PM) removal of electrostatic precipitators (ESPs) in coal-fired power plants, a pulse energization power supply that generates high-voltage pulses superimposed on a high-voltage dc was designed. The integrated theories of corona discharge, particle charging, and removal were presented, and the pulse energization strategy was studied through fractional particle removal simulation. The conclusion of simulation stated that pulse energization could significantly improve particle charge with a maximum enhancement at a particle diameter of $20~\mu \text{m}$ , while the fractional particle removal efficiency shows a different distribution that removal of particles less than $2.5~\mu \text{m}$ had the most significant enhancement. Based on the design and simulations, a full-scale comparative operation study testified the potential of dc + pulse energization to enhance particle removal with a limited power consumption increase. Pulse energization was applied to different industrial ESPs with various design and operation parameters and shown multicondition adaptability in PM removal enhancement, with the emission reduction ranging from 45.48% to 58.00% and outlet concentration from 8.60 to 47.48 mg/Nm3, proving it a convenient and economical method in the performance boost of industrial ESPs. [ABSTRACT FROM AUTHOR]

Abstract Improving the removal efficiency of fine particle is significant for the elimination of particle emission from coal-fired power plants. This work reports a combined wet electrostatic precipitator (WESP) enhanced by a novel perforated pre-charger to efficiently remove fine particle from wet flue gas. Penetration and charging characteristics of fine particle through the WESP were evaluated as a function of particle size. The collection performance was investigated under controlled gas temperatures and varied electrical conditions. Results showed that there was a maximum penetration ratio around 0.1 μm and it decreased with the increasing applied voltage. A portion of the escaping fine particles were not charged through the WESP, and the size limit for partial charging can be reduced to 0.025 μm when the applied voltage increased to 32 kV. Reducing gas temperature leaded to an obvious improvement in collection efficiency for particles in the size range of 0.1–1.0 μm. The test results of different electrodes showed that both the corona current and maximum collection efficiency ranked in the order of pin > sawtooth > rod. With the assistance of pre-charger, the particle charging was significantly improved and the charge amount was more than doubled. Consequently, the effective migration velocity for PM 0.1 , PM 1.0 and PM 2.5 increased by 69.9%, 65.7% and 34.2%, respectively. Actual application results showed that the average PM emission level can be reduced to 0.43 mg/m3 by the combined WESP in a 1000 MW coal-fired power plant. Graphical abstract Unlabelled Image Highlights • A combined WESP was developed to help to realize ultra-low emission. • Particle penetration and charging were evaluated as a function of particle size. • The charge amount was more than doubled assisted with the pre-charger. • The average PM emission level can be reduced to 0.43 mg/m3 in an actual plant. [ABSTRACT FROM AUTHOR]

Four typical coal-fired power plants were employed to explore the performance evolution within the whole life cycle of catalysts. The results revealed that the amount of active ingredients in the catalysts decreased over time. The content of V 2 O 5 and WO 3 in four units had decreased by 3.32%–32.8% and 12.9%–22.9% respectively. However, alkali metals and alkaline earth metals in flue gas were gradually deposited on the catalyst and led to catalyst poisoning, especially in two units due to arsenic poisoning. The specific surface area of catalysts decreased significantly in the first year of operation, accounting for 87.3%, 47.8%, 55.1% and 86.7% of the decline in the lifetime, which may be the main reason for the decline of catalyst activity during this period. The wall thickness of catalysts decreased linearly with the operation time in the lifetime. The relative activity of catalysts at the end of designed service lifetime was between 0.90 and 0.93, whereas the decrease range of SO 2 /SO 3 conversion rate was within 15.4%–35.6%. Influenced by the catalyst design and the variations of practical operation conditions, the difference between the actual and designed service lifetimes of catalysts in the four units was 2.08%, 44.0%, 4.17%, and − 25.0%, respectively. • SCR catalyst of four typical coal-fired power plant was investigated. • Catalyst performance evolution in three consecutive years of operation were analyzed. • A method for checking actual service lifetime of SCR catalyst was proposed. • Difference between the actual and designed catalyst lifetimes was obtained. • K/K 0 at the end of catalyst service lifetime was between 0.91 and 0.93. [ABSTRACT FROM AUTHOR]

• A new corrosion-resistant experimental system was designed to study SOx absorption reaction with alkaline sorbents. • The SO 3 absorption performance of the three alkaline sorbents was Na 2 CO 3 > Ca(OH) 2 ≈ Mg(OH) 2. • The influence of operating parameters on SO 3 removal had been deeply studied. • The SO 3 absorption variation above 300 °C was similar to the condition without vapor. • The external diffusion control model was established for SO 3 absorption rate. Selective Catalytic Reduction (SCR) system can efficiently remove NOx in coal-fired power plant, while raise SO 3 concentration in the flue gas. Alkaline sorbent injection is a major approach to remove SO 3. Experiments were conducted to study the SO 3 absorption performance of alkaline sorbent. The SO 3 absorption performance of the three alkaline sorbents was Na 2 CO 3 > Ca(OH) 2 ≈ Mg(OH) 2. The ratio of SO 3 absorption rate to SO 2 absorption rate for Na 2 CO 3 increased with the increasing temperature. The key parameters on the SO 3 absorption performance of Na 2 CO 3 were studied. The SO 3 absorption by Na 2 CO 3 was increased by 72.7% with increasing temperature from 150 °C to 300 °C, and the temperature had little influence on SO 3 absorption above 300 °C. The increasing SO 3 concentration and decreasing particle size of Na 2 CO 3 enhanced SO 3 absorption. However, when the average particle diameter was less than 50 μm, the SO 3 absorption was no longer significantly increased. The increasing CO 2 concentration slightly reduced the SO 3 absorption. After adding vapor into the flue gas, the SO 3 absorption was obviously increased below 300 °C. The SO 3 absorption variation above 300 °C was similar to the condition without vapor. When reaction temperature was 300 °C or above and reaction time was less than 20 min, external diffusion became the control step for SO 3 absorption. On the basis of external diffusion control model, the mass transfer coefficient slightly increased from 1.68 × 10−3 m/s to 1.75 × 10−3 m/s when the reaction temperature increased from 300 °C to 400 °C. [ABSTRACT FROM AUTHOR]

Sulfur dioxide (SO2) is one of the main air pollutants from many industries. Most coal-fired power plants in China use wet flue gas desulfurization (WFGD) as the main method for SO2 removal. Presently, the operating of WFGD lacks accurate modeling method to predict outlet concentration, let alone optimization method. As a result, operating parameters and running status of WFGD are adjusted based on the experience of the experts, which brings about the possibility of material waste and excessive emissions. In this paper, a novel WFGD model combining a mathematical model and an artificial neural network (ANN) was developed to forecast SO2 emissions. Operation data from a 1000-MW coal-fired unit was collected and divided into two separated sets for model training and validation. The hybrid model consisting a mechanism model and a 9-input ANN had the best performance on both training and validation sets in terms of RMSE (root mean square error) and MRE (mean relative error) and was chosen as the model used in optimization. A comprehensive cost model of WFGD was also constructed to estimate real-time operation cost. Based on the hybrid WFGD model and cost model, a particle swarm optimization (PSO)-based solver was designed to derive the cost-effective set points under different operation conditions. The optimization results demonstrated that the optimized operating parameters could effectively keep the SO2 emissions within the standard, whereas the SO2 emissions was decreased by 30.79% with less than 2% increase of total operating cost. Implications: Sulfur dioxide (SO2) is one of the main pollutants generated during coal combustion in power plants, and wet flue gas desulfurization (WFGD) is the main facility for SO2 removal. A hybrid model combining SO2 removal mathematical model with data-driven model achieves more accurate prediction of outlet concentration. Particle swarm optimization with a penalty function efficiently solves the optimization problem of WFGD subject to operation cost under multiple operation conditions. The proposed model and optimization method is able to direct the optimized operation of WFGD with enhanced emission and economic performance. [ABSTRACT FROM AUTHOR]

Pollutant abatement systems are widely applied in the coal-fired power sector, and the energy consumption is considered an important part of the auxiliary power. An energy consumption analysis and assessment model of pollutant abatement systems in a power unit was developed based on the dynamic parameters and technology. The energy consumption of pollutant abatement systems in a 1000-MW coal-fired power unit that meets the ultra-low emission limits and the factors of operating parameters, including unit load and inlet concentration of pollutants, on the operating power were analyzed. The results show that the total power consumption of the pollutant abatement systems accounted for 1.27% of the gross power generation during the monitoring period. The wet flue gas desulfurization (WFGD) system consumed 67% of the rate, whereas the selective catalytic reduction (SCR) and electrostatic precipitator (ESP) systems consumed 8.9% and 24.1%, respectively. The power consumption rate of pollutant abatement systems decreased with the increase of unit load and increased with the increase of the inlet concentration of pollutants. The operation adjustment was also an effective method to increase the energy efficiency. For example, the operation adjustment of slurry circulation pumps could promote the energy-saving operation of the WFGD system. Implications: The application of pollutant abatement technologies increases the internal energy consumption of the power plant, which will lead to an increase of power generation costs. The real-time energy consumption of the different pollutant abatement systems in a typical power unit is analyzed based on the dynamic operating data. Further, the influence of different operating parameters on the operating power of the system and the possible energy-saving potential are analyzed. [ABSTRACT FROM AUTHOR]

The implementation of ultra-low emission (ULE) limits (SO 2 : 35 mg/m3, NO x : 50 mg/m3, PM: 10 mg/m3) promoted the development of flue gas treatment technologies in China. Pollutant control technology development for Chinese coal-fired power plants was summarized and an analysis of the applicability and cost of pollutant control technologies was conducted. Detailed data were collected from 30 ultra-low emission coal-fired units across China. Based on a cost analysis model, the average unit power generation incremental costs were 0.0144 and 0.0095 CNY/(kW·hr) for SO 2 and NO x control technologies, respectively. The unit power generation incremental cost of twin spray tower technology was 7.2% higher than that of dual-loop spray tower technology. The effect of key parameters on operating cost was analyzed. The unit power generation incremental cost increased because of increments in the electricity price for SO 2 control technology and the price of the reductant in NO x control technology. With high sulfur content or NO x concentration, the unit power generation incremental cost caused by pollutant control increased, whereas the unit pollutant abatement cost decreased. However, the annual operating hours or load increased, thereby leading to a decline in unit power generation incremental cost and unit pollutant abatement cost. Unit power generation incremental cost of SO 2 and NO x control technologies for different coal-fired units. [Display omitted] [ABSTRACT FROM AUTHOR]

The life cycle environmental impacts of widely used flue-gas cleaning processes, including limestone-gypsum wet flue-gas desulfurization (FGD), selective catalytic reduction denitration (SCR) and electrostatic precipitators (ESP), are compared. The abbreviations FGD, SCR and ESP in this article refer in particular to the above listed processes. Energy consumption, resource consumption and emission inventories of each life cycle phase are established. The potentials of five environmental impact categories, namely, global warming, acidification, nutrient enrichment, photochemical ozone formation, soot and ashes are finally obtained. The current paper reveals that the total energy consumption and resource consumption are dominated by the process operation. The three processes are compared and it is found that to achieve equal environmental burden reductions, the SCR process consumes more energy and approximately the same amount of air and inert rock as the FGD. But the water consumption of the FGD is much higher than the SCR. The ESP process consumes both the least energy and the least resource in general. The economic assessment indicates that the performance of the ESP process tends to be the best and the FGD follows when equally invested. [ABSTRACT FROM AUTHOR]

The environmental issue of SO 3 pollution caused by coal-fired power plants attracts increasing attention. This work focused on the synergies between air pollution control devices in a 660 MW power plant burning high-sulfur coal. Parameters such as gas temperature and flow rate were varied within wide ranges under actual conditions. Both continuously tested SO 3 concentration and on-line operational data were combined to establish a correlation between device performance and operational parameter. Results indicated that the gas temperature acted as a bridge of synergies between the electrostatic precipitator (ESP) and wet electrostatic precipitator (WESP). The SO 3 removal efficiency across the ESP increased from 60.3% to 91.1% with the gas temperature decreasing from 136.7 to 114.8 °C, leading to the increase in corona current and the decrease in spark-over frequency of WESP. Moreover, additional electric field stages are also effective to enhance the corona current and reduce spark-over frequency. Furthermore, deviations between the design and operational data within 0–100% loading provided a correction to appropriately choose the gas velocity. With the proposed countermeasures, the SO 3 emission can achieve a favorable level less than 5 mg/m3. The research findings provide a valuable technical pathway to eliminate the SO 3 emission from power plants burning high-sulfur coal. Image 1092559 • A full-scale 660 MW power plant burning high-sulfur coal was investigated. • SO 3 effects on synergies among air pollution control devices were analyzed. • The gas temperature acted as a bridge of synergies between the ESP and the WESP. • Deviations were provided to guide the design and operation. • SO 3 emissions less than 5 mg/m3 can be realized with synergetic methods. [ABSTRACT FROM AUTHOR]

• Energy-cyber-physical-systems improve flexibility in fuel sources & energy products. • Quantitative analysis of improvement in coal-sludge co-combustion is conducted. • Quantitative thermodynamic and economic assessments are conducted. • The heating, cooling, power and compressed air products are stably produced. • Artificial neural network is employed for the prediction of realistic scenarios. The fluctuating energy requirement from time-varying demand changes require flexible power system to respond to the dynamic load balance. In certain scenarios, flexible power systems are necessary to provide high system efficiencies and increase the long-term economic benefits. Therefore, it is important to identify the relationship between energy requirement of a city and/or industrial zone with the dynamics of a flexible power system. In this paper, we evaluate the possible benefits of adopting the energy-cyber-physical-systems (e-CPSs) concept in realization of a flexible closed-loop control power system in case of coal-sewage sludge co-combustion. The case study performance analysis of flexibility, efficiency and economics (FEE) for a 356 MW coal-fired power plant was conducted by means of simulation in Aspen PLUS software. The analysis was based on a specific multifarious model of a dynamic power system with two energy sources and four energy products. The results confirmed that substantial advantages including a more flexible, efficient and economically viable system can be achieved by using e-CPSs based solution in different case scenarios. Moreover, following the analyzed data from the proposed case scenarios, a forecasting model for optimization of the power plant parameters based on the use of artificial neural network (ANN) was established. The results showed that ANN-based approach for predictive model is capable of modelling the complex process within an acceptable prediction accuracy. The study demonstrates that the proposed flexible closed-loop control power system based on e-CPSs concept is able to achieve higher efficiency and economic benefits compared to the traditional approaches. [ABSTRACT FROM AUTHOR]