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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]

Highlights • The SCR reaction occurred within a thin layer (ca. 0.2 mm) in the wall near the catalyst channel. • The SO 2 oxidation occurred in the entire catalyst wall. • The effects of the operating parameters were investigated synthetically. • A strategy for catalyst design, i.e., applying thin-walled design was proposed. Abstract A three-dimensional model that combined the selective catalytic reduction (SCR) of NO with ammonia and SO 2 oxidation reactions over monolith honeycomb catalyst was established to study the effects of catalyst structure and operating parameters on NO reduction and SO 2 oxidation. The model was to proved to be valid by experimental data. Simulation results showed that the SCR reaction only took place within a thin layer (ca. 0.2 mm) of the catalyst wall surface, whereas SO 3 generated via SO 2 oxidation accumulated throughout the entire wall. The effects of typical operating parameters, i.e., space velocity, temperature, feed concentrations of NO, NH 3 and SO 2 were studied. Temperature and gas velocity were found to be the major influencing factors on SO 2 oxidation. A strategy for monolith catalyst struction optimization, i.e., using thin-walled catalyst was proposed on the basis of these results. [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 In an electrostatic precipitator, particles migrate to the collecting plates through electrostatic force. Simultaneously, the effect of gravity and hydrodynamic drag force will cause these particles to vacate the plates. Emission concentration and removal efficiency gradually stabilize after the particles pass through multiple electric fields, and this stability value determines the high limit of electrostatic precipitation capacity. In this study, the balance between particle electrostatic trapping and air re-entrainment was investigated through a closed-loop electrostatic precipitator system, and the behavior of the particles deposited into the collecting plates was qualitatively analyzed. The particle emission concentration was reduced significantly when residence time was within 40 s. The particle concentration reached its limit and remained relatively stable after remaining stable for 100 s in the electric field. The applied voltage, velocity of flow, and temperature are the influencing factors considered in this study, here it was found that the decreased flow velocity, temperature and rising voltage were benefiting to particles removal efficiency. The ultimate emission concentration gradually decreased from 13.14 mg/m3 to 7.19 mg/m3 while the velocity of the flow decreased from 0.376 m/s to 0.240 m/s at the temperature of 700 K. The ultimate emission concentration gradually increased from 6.24 mg/m3 to 1.79 mg/m3 while the temperature decreased from 800 K to 400 K when the flue gas velocity was 0.376 m/s, and the applied voltage was at its maximum which can be used at the corresponding temperature. The ultimate emission concentration gradually decreased from 19.5 mg/m3 to 6.0 mg/m3 when the flue gas temperature was 400 K, and the velocity of the flow was 0.376 m/s, with the increase in voltage from 14.9 kV to 32.5 kV. In addition, particles of different size segments and specific resistances exhibited various characteristics in this study because the electrostatic and van der Waals forces were significantly affected by the particle size. Graphic abstract Unlabelled Image Highlights • The balance between particle collection and re-entrainment was studied. • A closed-loop electrostatic precipitator system was designed. • The ultimate collection efficiency were proposed. [ABSTRACT FROM AUTHOR]

Abstract A hybrid modeling scheme for electrostatic precipitators (ESPs) integrating particulate matter (PM) removal mechanism and the data-driven compensation method is presented in this article. The structure of the training and coupling method for the mechanism model, which considers electrodynamics, including corona discharging, particle charging, and removal, and the data-driven method that was trained based on operation data to compensate for the distortion and flaw of the mechanism model was constructed. Design parameters and operation data of an ESP in a coal-fired power plant were collected for model training, and prediction performances were compared. Different combinations of correction factors, including exponential, proportional, and bias, were studied. The form with the highest prediction R2 of 0.889 on the training set and 0.867 on the validation set was chosen as the mechanism part of the model. Deep neural networks with the highest R2 of 0.885 on the training set and 0.857 on the validation set were also trained as a comparison group. The performance of the hybrid model achieved a R2 of 0.933 on the training set and 0.887 on the validation set and outperformed the mechanism and data-driven models, thereby indicating that the hybrid modeling method could enhance prediction performance while maintaining the generalization capability of the PM removal mechanism in ESP. Graphical abstract Unlabelled Image Highlights • Hybrid modeling scheme for electrostatic precipitators is proposed. • PM removal mechanism model with best combined of correction factors is derived. • Performance of deep neural networks is compared with mechanism models. • Data-driven model is coupled with mechanism model to enhance performance. • Hybrid model has better prediction performance compared with other models. [ABSTRACT FROM AUTHOR]

Abstract Electrostatic precipitators (ESPs) are considered as cost-effective technology for separating the charged particle from flue gas. In this paper, a modified ESP model was developed to investigate the effects of charged particle on the electric field, ion density, particle charging and migration regarding various particle concentrations. Coupled processes of corona discharge, flow field, particle charging and transport were considered. Results showed that the particle space charge presented trajectory-dependent effects on the distributions of electric field and ion density in the gas flow direction. With the particle concentration increasing from 0 to 200 mg/m3, the electric field strength on the electrode surface was inhibited from 1.32 × 106 to 1.24 × 106 V/m, while the electric field strength on the plate surface was raised from 7.1 × 105 to 8.3 × 105 V/m. By contrast, the ion density within the whole domain decreased when particle space charge considered, and it decreased by more than 40% when the particle concentration was 50 mg/m3. The particle charging rate decreased due to particle space charge effects and consequently the overall particle charge decreased by 45.7% as particle concentration increased to 200 mg/m3. The correlation between collection efficiency and corona current was discussed, and it showed that the two didn't vary synchronously with the increasing concentration. A criterion for efficiency deterioration, under corona suppression conditions, was first proposed for instructing ESP design and operation. Graphical abstracts Unlabelled Image Highlights • A modified ESP model was established to study the particle space charge effects. • Corona discharge, flow field, particle charging and transport were coupled. • Correlation between corona current and collection efficiency was analyzed. • A criterion for ESP performance deterioration was first proposed. [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]

Wet electrostatic precipitators (WESP) have been proven to be a promising technology for the removal of sulfuric acid mist from flue gases. Recent studies indicate that WESPs, when mitigating sulfuric acid mist, can be less effective on systems that burn high sulfur content fuel. This paper reports on a pilot-scale WESP used to investigate SO 3 removal with high SO 3 concentration. Both mass concentration of SO 3 and number concentration of sulfuric acid mist were measured. Two key parameters, i.e., electrical characteristics and gas loading, were studied to evaluate their effects on SO 3 removal efficiency under severe corona suppression conditions. Results showed that the maximum corona current was reduced by 83.1% when the WESP inlet SO 3 concentration increased from 0 to 5 c 0 , and the corresponding SO 3 removal efficiency decreased from 74.5% to 54.2%. SO 3 removal efficiency can be improved by increasing corona power and reducing gas velocity. A comprehensive method was proposed to enhance SO 3 removal efficiency, with removal efficiencies greater than 90% using proper electrode configurations and lower velocity under a pilot plant condition. In addition, other challenges including new ultra-fine mist generation, material corrosion and insulator failure are summarized. [ABSTRACT FROM AUTHOR]

The corona discharge characteristics of an electrostatic precipitator are an important factor that affects particle charging and collection. The electrical characteristics of a wire-plate electrostatic precipitator and the particle transport behavior were studied by considering the electrohydrodynamics (EHD) and the effect of particle space charge through numerical simulation. Simulation results showed that the effect of particle space charge intensifies in extremely small particles, such as submicron particles. This condition significantly influences electric field, ionic charge density, and current. The electric field intensity and ionic charge concentration significantly decreased. The reduction in the minimum field intensity between the electrodes decreased to 50%, and the lowest concentration of the ionic charge tended to 0 when the particle size varied from 5 µm to 0.1 µm. When the applied voltage increased from 13 kV to 40 kV, the space charge ratio of the particles larger than 2 µm was reduced to almost 0 but remained at a high level for the particles less than 0.5 µm whose corresponding current was lower by 20% than that without particle condition. The ionic wind in the electrostatic field also weakened because the movement of ions was restricted for corona suppression, leading to decreased corona current. Furthermore, the particle transport behavior was compared considering the effect of particle space charge. Results indicated that the difference between the two conditions increased from 1.3% to 47.4% with decreasing particle size from 5 µm to 0.07 µm. In addition, the particle migration velocity of the 0.1 µm particles increased by 9.8%, from 0.2 to 0.1 µm, even if the drag force was reduced when considering the particle space charge. A modified I–V equation was provided, with fitting coefficient of 0.996, and is thus worthy of reference in practical application. [ABSTRACT FROM AUTHOR]

Resistivity is a key factor in the efficient and stable operation of electrostatic precipitators. Sixty types of typical industrial fly ashes were collected for this study. Subsequently, fly ash resistivity at the temperature range of 303–1073 K, and the chemical compositions, micrographs, and size distributions of the samples were measured. The joint influence of chemical composition and temperature on resistivity was also investigated. The main components of the fly ash samples were Fe (0.8–5.0%), K + Na + Li (0.3–5.1%), Ca + Mg (0.5–4.0%), and Al + Si (10–34%), respectively. Fe, K, and Na were highly sensitive to fly ash resistivity. Resistivity decreased with the increase in Fe, K, Na, and Li contents; by contrast, resistivity increased with Ca and Mg contents. The effects of Si and Al on fly ash resistivity were weak. Resistivity initially increased first and then decreased with the increase in temperature. Maximum resistivity was observed at 373–473 K. Based on the experimental data, a prediction model for fly ash resistivity over a wide range of temperature (303–1073 K) was established. The resistivity diagrams generated specifically for this study suggest that typical fly ash samples from different industries can be estimated using chemical composition and temperature data. [ABSTRACT FROM AUTHOR]

Non-thermal plasma with different O 2 concentration in discharge atmosphere was applied to synthesize manganese and cerium mixed-oxides catalysts, which were compared in NO oxidation activity. Discharge atmosphere displayed a crucial influence on the performance of the catalysts prepared by plasma. Relatively low O 2 concentration in discharge atmosphere allows synthesizing manganese-cerium oxides catalysts in a moderate environment and therefore is favorable for better physicochemical properties which lead to superior catalytic behavior. The best catalyst was obtained by treatment with 10% O 2 /N 2 plasma and presented over 80% NO conversion in the temperature range of 275–325 °C, whereas catalyst prepared in pure O 2 discharge atmosphere had the same activity with a catalyst prepared by calcinations. A correlation between the surface properties of the plasma prepared catalysts and its catalytic activity in NO oxidation is proposed. The amount of the surface adsorbed oxygen has an obvious linear correlation with the amount of Ce 3+ , the H 2 consumption at low temperatures and the catalytic performance. The superior catalytic performance is mainly attributed to the stronger interaction between manganese oxides and ceria, and the formation of poorly crystallized Mn-O-Ce phase in the catalyst which resulted from the slow decomposition of nitrates and organics during plasma treatment. Catalysts prepared in relatively low O 2 concentration have large specific surface area and is abundant in Ce 3+ species and active oxygen species. The study suggests that plasma treatment with proper discharge gas components is a promising method to prepare effective manganese- cerium oxides catalyst for NO oxidation. [ABSTRACT FROM AUTHOR]

The flue gas generated from glass furnaces contains particles with high concentrations of alkali metals and hazardous heavy metals, which could reduce the lifespan of selective catalytic reduction (SCR) catalysts and lead to catalyst deactivation. Removing the particles before SCR could improve system operation reliability and reduce nitric oxides (NOx) emission. In this paper, the characteristics of fly ash from glass furnaces and the particle removal properties in the electrostatic precipitator (ESP) from 363 K to 623 K were studied. The particle collection efficiency was found to decrease with increasing temperature. A method of enhancing particle removal was proposed and tested through particle conditioning in a lab-scale experiment. In order to change the characteristics of the fly ash, calcium carbonate powders were used as conditioning particles and the particle collection efficiency increased from 65.8% to 87.6% at 623 K. This method was further applied in an industrial high-temperature ESP for a glass furnace. When the ratio in mass between the particles from the glass furnace and from the conditioning proportion was 1:1.5, the particle collection efficiency of the ESP was improved significantly and the outlet particle concentrations decreased from 103.23 mg/Nm 3 to 39.25 mg/Nm 3 . [ABSTRACT FROM AUTHOR]

Electric agglomeration is a useful method to improve fly-ash particle collection efficiency in traditional electrostatic precipitators (ESPs) by increasing particle diameter and achieving particle pre-charging. In this study, a laboratory agglomerator, which consisted of a pre-charging region and a static mixer, was designed and tested for fine particle agglomeration. The pre-charging provided both positive and negative discharges in parallel channels. Fine water droplets were used to enhance particle agglomeration and collection efficiency in a downstream small ESP. The operating effects were evaluated under various applied voltages and droplet concentrations. Experimental results showed that the presence of water droplets effectively improved coal-fired particle agglomeration, pre-charging, and collection in the ESP. The total number collection efficiency improved from 53.91% to 86.02% compared with the condition without the agglomerator. In addition, a novel sampling method was used to observe agglomerated particles using scanning electron microscopy, and theoretical adhesive force analysis supported the proposal of a series of power-plant particle electric agglomeration modes. [ABSTRACT FROM AUTHOR]

Electrostatic precipitation is considered as an effective technology for fine particle removal. A lab-scale wet electrostatic precipitator (ESP) with wire-to-plate configuration was developed to study particle migration and collection. The performance of the wet ESP was evaluated in terms of the corona discharge characteristics, total removal efficiency and fractional removal efficiency. The corona discharge characteristics and particle removal abilities of the wet ESP were investigated and compared with dry ESP. Particle removal efficiency was influenced by discharge electrode type, SO2concentration, specific collection area (SCA) and particle/droplet interaction. Results showed that the particle removal efficiency of wet ESP was elevated to 97.86% from 93.75% of dry ESP. Three types of discharge electrodes were investigated. Higher particle removal efficiency and larger migration velocity could be obtained with fishbone electrode. Particle removal efficiency decreased by 2.87% when SO2concentration increased from 0 ppm to 43 ppm as a result of the suppression of corona discharge and particle charging. The removal efficiency increased with higher SCA, but it changed by only 0.71% with the SCA increasing from 25.0 m2/(m3/s) to 32.5 m2/(m3/s). Meanwhile, the increasing of particle and droplet concentration was favorable to the particle aggregation and improved particle removal efficiency. Implications: This work tends to study the particle migration and collection under spraying condition. The performance of a wet electrostatic precipitator (ESP) is evaluated in terms of the corona discharge characteristics, total particle removal efficiency, and fractional particle removal efficiency. The effects of water droplets on particle removal, especially on removal of particles with different sizes, is investigated. The optimization work was done to determine appropriate water consumption, discharge electrode type, and specific collection area, which can provide a basis for wet ESP design and application. [ABSTRACT FROM AUTHOR]

The temporal trends of industrial volatile organic compound (VOC) emissions was comprehensively summarized for the 2011 to 2013 period, and the projections for 2020 to 2050 for China were set. The results demonstrate that industrial VOC emissions in China increased from 15.3 Tg in 2011 to 29.4 Tg in 2013 at an annual average growth rate of 38.3%. Guangdong (3.45 Tg), Shandong (2.85 Tg), and Jiangsu (2.62 Tg) were the three largest contributors collectively accounting for 30.4% of the national total emissions in 2013. The top three average industrial VOC emissions per square kilometer were Shanghai (247.2 ton/km 2 ), Tianjin (62.8 ton/km 2 ), and Beijing (38.4 ton/km 2 ), which were 12–80 times of the average level in China. The data from the inventory indicate that the use of VOC-containing products, as well as the production and use of VOCs as raw materials, as well as for storage and transportation contributed 75.4%, 10.3%, 9.1%, and 5.2% of the total emissions, respectively. ArcGIS was used to display the remarkable spatial distribution variation by allocating the emission into 1 km × 1 km grid cells with a population as surrogate indexes. Combined with future economic development and population change, as well as implementation of policy and upgrade of control technologies, three scenarios (scenarios A, B, and C) were set to project industrial VOC emissions for the years 2020, 2030, and 2050, which present the industrial VOC emissions in different scenarios and the potential of reducing emissions. Finally, the result shows that the collaborative control policies considerably influenced industrial VOC emissions. [ABSTRACT FROM AUTHOR]

This study investigated the influence of electrode configuration on corona discharge and particle collection from 300 K to 900 K. Electrodes of different shapes (rod, saw, and screw), diameters (3, 5, and 8 mm), and intervals (55, 110, and 165 mm) were tested in an experimental-scale electrostatic precipitator (ESP). Results showed that a high current was generated with a saw electrode and increased the particle collection efficiency, particularly for fine particles (diameter smaller than 0.1 μm), with the best particle collection efficiency being 99.8% at 300 K. However, with an increase in temperature, the rod electrode obtained an applied voltage higher than those of other electrode types and, as a result, generated relatively high particle collection efficiencies at 700 K and 900 K. Increasing the electrode diameter from 3 mm to 5 mm improved the applied voltage, whereas increasing this diameter from 5 mm to 8 mm reduced the discharge current. Among electrodes with different diameters, the electrode with a diameter of 5 mm achieved the best particle collection efficiency (87.4%) at 900 K. The applied voltages of the electrodes with different intervals were almost similar, but the discharge currents varied significantly. The best particle collection efficiencies were achieved by the electrode with an interval of 55 mm at 300 K and 500 K, but at 700 K and 900 K, the electrode with an interval of 110 mm obtained the best result. The interval between electrodes should be expanded with an increase in temperature to avoid the offsetting of electric field between neighboring electrodes. [ABSTRACT FROM AUTHOR]

High-temperature ESPs are proposed to improve energy efficiency and avoid damage to downstream equipment in integrated gasification combined cycle and pressurized fluidized-bed combustion. In this study, the effects of temperature and pressure on negative corona discharge characteristics were compared. Gas temperature varied from 373 K to 1073 K, and pressure varied from 30 kPa to 100 kPa to achieve the same gas density. The additional corona current Δ I t induced by high temperature was calculated, and the additional ion current Δ I i and electron current Δ I e were studied. A wire-type electrode, a spiral electrode, a ribbon electrode, and four gas compositions (N 2 /CO 2 /SO 2 /air) were investigated in the plate-type discharge configuration. Results show that corona current increases more rapidly with increasing gas temperature than that with decreasing pressure at the same gas density. The current density is 0.87 mA/m at 973 K and atmosphere pressure, which is higher than 0.45 mA/m at 30.9 kPa and room temperature. An additional temperature effect on corona discharge is proposed apart from the decrease of gas density as temperature increases. Δ I t increases with increasing temperature because of enhanced molecule kinetic energy and ionization rate. The electron-carried current is important at temperatures above 873 K. Δ I e /Δ I t increases from 0 to 0.941 when temperature increases from 773 K to 973 K. Compared with the Δ I t of wire and spiral electrodes, the Δ I t of ribbon electrode is significantly larger because of the enhanced electron avalanche and secondary electron emission. Negative corona discharge does not occur in N 2 , and corona onset voltages are in the following sequence: CO 2 > SO 2 (6000 ppm) > air, which is determined by gas molecule ionization energy. Δ I t / I P is smaller in gas atmosphere with strong electronegativity. [ABSTRACT FROM AUTHOR]

A plasma–catalyst reactor was used for the adsorption of elemental mercury at low temperatures. SiO 2 , TiO 2 and SiO 2 or TiO 2 supported transition metal oxide catalysts were packed in the plasma discharge zone for adsorption enhancement. The results indicated that non-thermal plasma could induce the adsorption of elemental mercury effectively by catalysts. TiO 2 displays much higher adsorption efficiency than SiO 2 does. The adsorption efficiency is greatly improved by loading transition metal oxides on TiO 2 . Mn/TiO 2 is the most efficient catalyst, and ~ 99% of Hg 0 adsorption efficiency can be obtained under a SED of 2.3 ± 0.3 J L − 1 . The interaction between the plasma and catalyst was also investigated. The chemical properties of the catalyst, such as the active sites and electron transfer capacity, are key factors that affect adsorption efficiency. The mercury adsorption in plasma–catalyst reactor results primarily from the interaction between weakly adsorbed mercury and activated oxygen on catalyst surface induced by plasma. In addition, the effect of the O 2 concentration and HCl on mercury adsorption efficiency was investigated. The adsorption efficiency has a logarithmic correlation with O 2 concentration in the gas flow. [ABSTRACT FROM AUTHOR]

High-temperature electrostatic precipitators for removing dust from fuel or flue gases were proposed to improve energy efficiency or to avoid damaging downstream equipment. This paper attempts to provide a comprehensive understanding of negative DC corona discharges and find ways to increase corona stability at high temperatures. The characteristics of corona discharges were studied in a wire–plate discharge configuration under different discharge gaps and electrode geometries at temperatures ranging from 293 K to 1173 K. The V – I characteristics were analyzed, including corona onset/spark voltages, operating voltage ranges, and corona current compositions. The discharge current density increases as the temperature increases, and the electron-carried current becomes significant at high temperatures. For example, the electron-carried current makes up ∼40% of the total discharge current at 1073 K under an applied voltage of 10 kV. The applied voltage range decreases as the temperature increases. The corona discharges become unstable, and localized breakdowns occur frequently when the temperature exceeds 1073 K and the discharge gap is less than 50 mm, because the ionization coefficient and the number of electrons greatly increase. The operating voltage range increases from 8.2 kV to 13.6 kV at 1073 K when the discharge gap increases from 30 mm to 70 mm. Compared with the wire and spiral electrodes, the ribbon electrodes produce sparks more easily. The wire diameter has little influence on the spark voltage and corona stability at high temperatures. [ABSTRACT FROM AUTHOR]

Highlights: [•] The NOx absorption and nitrite/nitrate formation in limestone slurry was studied. [•] The NOx compositions and SO2 significantly affects NOx absorption rates. [•] The mechanism of NOx absorption and conversion in limestone slurry was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A field-scale demonstration setup was used to investigate particle growth and removal. • Particle size in actual flue gas was analyzed. • 80.05% particle removal efficiency could be achieved by heat exchanger. • The strategy of temperature management to control the pollutants was obtained. Flue gas generated from coal combustion is the primary source of air pollution. Temperature is an essential parameter for the treatment process of flue gas pollutants. In this study, a field-scale demonstration setup was used to investigate the effect of temperature on particle growth and removal by using actual flue gas. The ionic migration in heat exchanger was also studied, and a temperature management method was established. Results showed that the temperature had a substantial influence on particle growth and removal, the outlet particle median diameter increased from 0.116 µm to 0.155 µm, and the outlet particle mass concentration decreased from 7.05 mg/Nm3 to 4.49 mg/Nm3 when the flue gas temperature difference was 2.9–4.6 K. Changing the boiler load from 100% to 65% led to the increase in the particle removal efficiency from 78.06% to 80.33%. This increment was mainly related to the changes in temperature. In addition, when the temperature difference increased from 2.9 K to 4.6 K, the concentration of the ions in the sample significantly increased, and the removal amount of mercury was enhanced by 2.57 times. The pollutant in the flue gas was effectively removed by the temperature management installation between the wet flue gas desulfurization and wet electrostatic precipitator. [ABSTRACT FROM AUTHOR]

OH radicals play an important role in pollutant removal in nonthermal plasmas. It is crucial to clarify the behavior of OH radicals in this process. A time-resolved 2-D OH radial distribution was investigated in a pulsed corona discharge by planar laser-induced fluorescence at atmospheric pressure and room temperature. The OH evolutions under different gas components were studied, and the evolution process was simulated. The OH decay processes were found to be divided into two periods: a fast decay period and a slow decay period. The O, N, and \HO2 are dominant radicals for OH generation and decay. The OH radicals are mainly generated near a nozzle electrode. The concentration variations of \O2, NO, and \H2\O in the background gas led to different OH density evolutions. The OH distribution zones were different as gas components varied. The maximum area of OH radical distribution after discharge decreased by 20\% as \O2 increased from 5\% to 8 \%, and it decreased by 69 \% as NO (150 ppm) was added into the background gas. [ABSTRACT FROM PUBLISHER]

Abstract: A reciprocal flow porous burner with an external heat source in the middle section was studied numerically to access the reactor efficiency for synthesis gas generation. The temperature and species profiles were predicted using a two temperature model with a detailed chemical mechanism. The effect of the variation of the power of the external heat source on the hydrogen and carbon monoxide yields was studied. The energy conversion efficiencies of the system with various power levels of the external heat source were evaluated. It is found that H2 and CO yields increase significantly with the addition of the external heat source due to the temperature increase in the middle section of the burner. The CO2 emissions remain small. The methane conversion ratio increases with increase of the power of the external heat source reaching 97%. The H2 and CO conversion ratios yields are nearly doubled as the power of the external heat source increases from 0 to 750W. The cold gas energy conversion efficiency decreases as the power of the external heat source increases. At the same time, the syngas energy conversion efficiency increases from 41% to 70%, while hydrogen energy conversion efficiency increases from 28% to 46%. [Copyright &y& Elsevier]

Abstract: Inclinational instability developing during propagation of a filtration combustion wave in an inert porous medium is studied using two-dimensional numerical model. Stable and unstable combustion waves are generated by varying combustion parameters such as pressure, equivalence ratio, filtration velocity, effective conductivity of porous media, pellet diameter and combustor scale. The wave propagation velocity of inclinational flame is studied and compared with flat flame. The growth and reduction of inclinational instability are analyzed at different conditions. The numerical results show that a development of inclinational instability causes essential flow non-uniformity and can result in a separation of the flame front in the multiple flame zones. The limited conductive and radiant heat transfer in the solid phase, small pellet diameter of packed bed, high inlet velocity, large combustor scale and low equivalence ratio promote the instability growth. The inclinational instability is suppressed in a reciprocal combustor. [Copyright &y& Elsevier]

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]

Detecting hydrogen leaks remains a pivotal challenge demanding robust solutions. Among diverse detection techniques, the fiber-optic method distinguishes itself through unique benefits, such as its distributed measurement properties. The adoption of hydrogen-sensitive materials coated on fibers has gained significant traction in research circles, credited to its operational simplicity and exceptional adaptability across varied conditions. This manuscript offers an exhaustive investigation into hydrogen-sensitive materials and their incorporation into fiber-optic hydrogen sensors. The research profoundly analyzes the sensor architectures, performance indicators, and the spectrum of sensing materials. A detailed understanding of these sensors' potentials and constraints emerges through rigorous examination, juxtaposition, and holistic discourse. Furthermore, this analysis judiciously assesses the inherent challenges tied to these systems, simultaneously highlighting potential pathways for future innovation. By spotlighting the hurdles and opportunities, this paper furnishes a view on hydrogen sensing technology, particularly related to optical fiber-based applications. [ABSTRACT FROM AUTHOR]

• A temperature-controlled experimental system was designed to study dust layer. • The role of dust layer on discharge characteristics was studied. • Criterions for migration velocity deterioration was first proposed. • Strategies to enhance discharge stability and particle migration were proposed. Charged particles were deposited on collection plates to form a dust layer in electrostatic precipitator (ESP). In turn, the dust layer could affect the performance of ESP strongly. In this work, the effect of the dust layer on the discharge characteristics and space electric strength was investigated under the different discharge gaps, thickness, and resistivity of the dust layer at temperatures that ranges of 50 °C to 400 °C. Results indicate that an abnormal discharge called back corona was observed as the voltage increased, and its onset voltage would decrease under thick dust layer, short discharge gap, and high temperature and resistivity of the dust layer. When voltage was lower than the onset voltage of the back corona, the discharge current of the stable discharge would increase with temperature but decrease as discharge gap, resistivity, and thickness of dust layer increased. Moreover, the space electric strength of stable discharge was significantly higher than that of the back corona. Space electric strength was strongly correlated with the resistivity of the dust layer. When resistivity increased, a region where the space electric strength reduced rapidly was observed. When resistivity increased from 6.27 × 109 Ω·cm to 8.45 × 1010 Ω·cm, the space electric strength decreased by 33.8% at 50 °C under voltage between electrodes of 22 kV. These variations in space electric strength support the possible decrease in migration velocity as resistivity increased, especially at high resistivity. The criteria for migration velocity deterioration were proposed for instructing ESP design and operation. [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]

Recycling of valuable metals from spent catalysts in a green way is gaining extensive interest for economic and environment reasons. In this study, we developed novel hydrophobic deep eutectic solvents to extract Mo from spent catalysts. The hydrophobic DESs have been designed and synthesized by mixing one molar of the quaternary ammonium salt and two molars of various saturated fatty acids with different carbon chain lengths. The extraction ability and extraction mechanism of these DESs were studied, some factors influencing the extraction efficiency, including the structure of hydrogen bond acceptors and hydrogen bond donors, initial aqueous pH, reaction time and temperature, phase ratios were investigated. It is found that the synthesized hydrophobic DESs exhibit excellent extraction performance toward Mo, where the Mo distribution ratio is more than 2200 in the presence of other metals, corresponding to an extraction efficiency of 99% at optimal reaction conditions. This work reveals a distinct class of materials, guiding an effective and green way for spent catalyst treatment. Implications: Novel hydrophobic deep eutectic solvents have been developed to extract Mo from spent catalysts, the synthesized hydrophobic DESs possess several advantages, such as green, low price, low toxicity, and biodegradability. It exhibits excellent extraction performance under an optimized extraction condition. This work reveals a distinct class of materials, guiding a promising way for green and economical utilization of spent catalysts. [ABSTRACT FROM AUTHOR]

Ships and other mobile pollution sources emitted massive ultrafine and low-resistivity particles containing black carbon (BC), which were harmful to human health and were difficult to capture by conventional electrostatic precipitators (ESPs). In this study, nanoscale carbon black was adopted as simulated particles (SP) with similar physicochemical properties for black carbon emitted from ships (SP-BC) to investigate the feasibility of using an ESP with square-grooved collecting plates for the removal of SP-BC at low backpressures. The increased applied voltage significantly improved the total collection of SP-BC whereas may also promote the conversion of relatively larger particle size SP-BC into nano-size below 20 nm. The outlet number concentration of SP-BC under 27 kV at 130°C was three times that of the inlet. While the reduction of the flow rate could strengthen the capture of SP-BC below 20 nm, and under the combined action of low flow rate and maximum applied voltage, the collection efficiency of 20-100 nm SP-BC could exceed 90%. In addition, the escape and capture characteristics of SP-BC under long-term rapping were revealed. The square-grooved collecting plate could effectively restrain the re-entrainment of collected SP-BC generated by rapping, and the nanoscale SP-BC was trapped in the grooves after rapping. The results could provide insights into the profound removal of massive nanoscale black carbon emissions from mobile sources. [ABSTRACT FROM AUTHOR]

An NH 3 slip detection device and system were designed and developed. The system includes sampling, absorption, detection, dosing, cleaning, and control components. The problems accompanying low NH 3 slip, easy adsorption and instability, can be effectively overcome by the developed device. Furthermore, an online accurate measurement of NH 3 slip was realized. Meanwhile, the online calibration function of the device addresses the drawbacks of existing online NH 3 slip monitoring devices. The reliability and stability of the detection data were improved, whereas the sampling time, flow rate, gas concentration, and pH, which affect the NH 3 measurement results, were experimentally investigated. The main sampling parameters were optimized by orthogonal experiments, and the measurement error of the detection device was obtained according to experimental results. A correction model for measured values was then established, which further improved the accuracy of the measured data. The device has the advantages of high efficiency, stability, high accuracy, online calibration ability, and high integration compared with existing NH 3 slip detection devices for denitration systems. The developed device can be utilized for online detection of NH 3 slip in the denitration equipment of coal-fired power plants. [ABSTRACT FROM AUTHOR]

Regenerative thermal oxidizers (RTO) serve as pivotal equipment for the treatment of volatile organic compounds (VOCs). However, a diversity of faults of the RTO system may threaten personnel safety and lead to unscheduled downtime. In this work, we develop a traceability inference method based on dynamic uncertain causality graph (DUCG) to identify root fault cause of RTO at early anomaly alarm. A general expert knowledge base for the fault diagnosis of RTO system is constructed. And the anomaly alarm thresholds are modified according to historical data with n-sigma rules to improve the diagnostic accuracy. Results on different cases show advantages in both triggering early anomaly alarms and avoiding invalid alarms, which is crucial to improve the fault inference accuracy. By applying our method to 35 fault cases of a real RTO for pharmaceutical VOCs treatment, the fault detection rate reaches 94.29%, and the fault inference accuracy is 82.86%. The two scores are 3% and 21% higher than those with the conventional DUCG (with fixed alarms), respectively. This remarkable improvement underlines the significance of our proposed method for RTO maintenance, and it is expected to assure the system's operational stability and reliability. [Display omitted] [ABSTRACT FROM AUTHOR]

Disposal of spent catalyst in an economical and green way has become a great concern for industrial production. We developed a process including acid leaching, solvent extraction and stripping in order to recycle spent catalyst. In this study, we conducted selective recovery of molybdenum through focus on finding an optimized extraction and stripping process by comparing different extractants and stripping agents. To separate molybdenum from other metals efficiently and figure out the mechanism of extraction process, the five different extractants of methyl trioctyl ammonium chloride, tri-n-octylamine, tris (2-ethylhexyl) amine, bis (2-ethylhexyl) phosphate, and tributyl phosphate with different functional groups were examined; the extraction ability and extraction mechanism of these five extractants were systematically studied under the same system for the first time. It was found that more than 98% of the molybdenum could be extracted with an organic phase consisting of tri-n-octylamine or methyl trioctyl ammonium chloride under the optimal conditions. The result indicated that the tri-n-octylamine and methyl trioctyl ammonium chloride possess excellent molybdenum extraction ability, the extraction capacity of the rest extractants was in the order of bis (2-ethylhexyl) phosphate > tris (2-ethylhexyl) amine > tributyl phosphate. In the stripping process, NH4OH, NaOH, and H2SO4 were chosen as stripping agent to strip the molybdenum from the loaded tri-n-octylamine organic phase. The stripping ability of the three studied stripping agents was in the order NaOH > NH4OH > H2SO4. The Fourier transform infrared (FTIR) spectra showed that the structure of the tri-n-octylamine organic phase was stable during the extraction and stripping process. Results showed that molybdenum could be highly and efficiently recovered by optimized extraction and stripping process. Implications: A series of different extractants and stripping agent have been systematically studied in order to compare their extraction and stripping ability under the same system. Based on the obtained results, an optimized extraction and stripping process was proposed to recycle molybdenum from spent catalyst efficiently. It is possible to dispose spent catalysts in an economic and environmental way by this developed metal recovery process. [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]

Graphical abstract Highlights • Hg0 adsorption on MoS 2 nanosheet was investigated using ab initio calculation. • Influence of different types of defects on Hg0 adsorption was studied. • S vacancy in the MoS 2 nanosheets exhibited outstanding potential in Hg0 adsorption. • Novel approach was developed in this study to synthesize MoS 2 under controlled manner. • The adsorption of Hg0 on MoS 2 nanosheets is found to be non-activated chemisorption. Abstract In this research, ab initio calculations and experimental approach were adopted to reveal the mechanism of Hg0 adsorption on MoS 2 nanosheets that contain various types of defects. The ab initio calculation showed that, among different structural defects, S vacancies (Vs) in the MoS 2 nanosheets exhibited outstanding potential to strongly adsorb Hg0. The MoS 2 material was then prepared in a controlled manner under conditions, such as temperature, concentration of precursors, etc., that were determined by adopting the new method developed in this study. Characterisation confirmed that the MoS 2 material is of graphene-like layered structure with abundant structural defects. The integrated dynamic and steady state (IDSS) testing demonstrated that the Vs-rich nanosheets showed excellent Hg0 adsorption capability. In addition, ab initial calculation on charge density difference, PDOS, and adsorption pathways revealed that the adsorption of Hg0 on the Vs-rich MoS 2 surface is non-activated chemisorption. [ABSTRACT FROM AUTHOR]

Abstract Seriously stringent emission regulations are applied in the coal-fired power sector in China. GB13223-2011 standards and ultra-low emission limits are promulgated to improve the application of pollutant abatement systems and reduce emissions, respectively. However, the accompanying problem of additional economic burden may affect the operation of power units and sectors. This study proposed a cost estimate model of multi-pollutant control and designed several scenarios to evaluate the total cost of different emission standards in China's coal-fired power sector. The operating costs of NO x , SO 2 , and PM control of a typical 300 MW unit were 6.9, 11.7, and 4.3 CNY/MWh, respectively, when meeting the GB13223-2011 emission standard and 8.2, 13.8, and 7.9 CNY/MWh, respectively, when meeting the ultra-low emission limits. Investment, energy consumption, and catalyst greatly influenced the operating cost. The scenarios analysis suggested that the total costs of multi-pollutant control under the GB13223-2011 standards and ultra-low emission limits were approximately 141.79–170.28 and 186.35–221.67 billion CNY per year, respectively. Feasible cost reduction strategies were analyzed on the basis of operation management and sector planning. The economic influence of the application of pollutant abatement systems on coal-fired power units should be evaluated comprehensively. Highlights • The additional cost of emission control in coal-fired power sector is acceptable. • High investment and energy and resource consumptions are the main barriers. • Regional costs of different scenarios are estimated at different standards. • Operation management can achieve the cost reduction. • Installing the pollutants abatement system in small capacity unit will cost more. [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]

[Display omitted] The pretreatment of cathode material before leaching is crucial in the spent lithium-ion battery hydro-metallurgical recycling. Here research demonstrates that in-situ reduction pretreatment could dramatically improve the leaching efficiencies for valuable metals from cathodes. Specifically, calcination under 600 °C without oxygen using alkali treated cathode can induce in-situ reduction and collapse of oxygen framework, which is ascribed to the carbon inherently contained in the sample and promote the following efficient leaching without external reductants. The leaching efficiencies of Li, Mn, Co and Ni can remarkably reach 100%, 98.13%, 97.27% and 97.37% respectively. Characterization methods, such as XRD, XPS and SEM-EDS, were employed and revealed that during in-situ reduction, high valence metals such as Ni3+, Co3+, Mn4+ can be effectively reduced to lower valence states, conducive to subsequent leaching reactions. Moreover, leaching processes of Ni, Co and Mn fit well with the film diffusion control model, and the reaction barrier is in accordance with the order of Ni, Co and Mn. In comparison, it is observed that Li was leached with higher efficiency regardless of the various pretreatments. Lastly, an integral recovery process has been proposed and economic assessment demonstrates that in-situ reduction pretreatment increases the benefit with a negligible cost increase. [ABSTRACT FROM AUTHOR]

• Models of CO 2 capture by solid particles based on MgO adsorbent were established. • The shrinking-core model is implemented, and each particle was tracked individually. • The effects of solid sorbent particle size, inlet gas velocity, and inlet CO 2 mass fraction were investigated. • The decarbonization performance of fluidized bed and packed bed was compared. Given that carbon dioxide (CO 2) constitutes the predominant proportion of greenhouse gas emissions, its capture, utilization and storage have always been a subject of great concern. Gas-solid fluidized bed has become one of the commonly applied equipment for the removal of CO 2 from flue gases owing to its advantages such as exceptional mixing effect and substantial interfacial area between the phases. However, there is a lack of attention to the mechanism of CO 2 absorption by individually-tracked moving solid sorbents as well as their effects on the decarbonization performance in a gas–solid fluidized bed. In this study, CO 2 removal model by solid particles based on MgO adsorbent was established with the implementation of the shrinking-core model and each particle was tracked individually. Results validated the accuracy of the absorption model and revealed that smaller sizes of the solid absorbent, lower inlet gas velocities and larger inlet CO 2 mass fractions exhibit relatively high CO 2 removal efficiency. In addition, the decarbonization performance of fluidized and packed beds was compared. The packed bed exhibits more uniform gas flow and higher CO 2 removal efficiency, whereas the fluidized bed provides larger interphase contact area, which facilitates the heat transfer process. Through the analysis of a series of parameters, the results provide recommendations for improving the CO 2 removal efficiency and help to explore the optimal protocol for the design of bed reactors for CO 2 removal. [ABSTRACT FROM AUTHOR]

This study focused on promotional effect of Sb 2 O 5 and Nb 2 O 5 addition to V-SCR on decomposition of NH 4 HSO 4 , reactivity of NH 4 HSO 4 and NO, and sulfur resistance. Adding Sb 2 O 5 and Nb 2 O 5 increased the electron cloud density around the S atoms in SO 4 2− , which exerted a positive effect on the transformation of SO 4 2− to SO 2 in the lower temperature region. As a result, the decomposition behavior of NH 4 HSO 4 was obviously enhanced on the promoters-modified catalysts. Meanwhile, a high reactivity of NH 4 HSO 4 with NO was observed with the introduction of Sb 2 O 5 and Nb 2 O 5 , which could be explained by the increased amount of V 5+ and reactive electrophilic oxygen species on the Sb 2 O 5 - and Nb 2 O 5 -doped catalyst surfaces. Finally, the deactivation of catalysts by SO 2 and H 2 O was impeded in a certain extent through introducing Nb 2 O 5 and Sb 2 O 5 , suggesting that these promoters-modified catalysts might be typically used in the low-temperature SCR systems in the future. [ABSTRACT FROM AUTHOR]

Industrial development is an essential foundation of the national economy, but the industry is also the largest source of air pollution, of which power plants, iron and steel, building materials, and other industries emit large amounts of pollutants. Therefore, the Chinese government has promulgated a series of stringent emission regulations, and it is against this backdrop that research into air pollution control technologies for key industrial sectors is in full swing. In particular, during the 13th Five-Year Plan, breakthroughs have been made in pollution control technology for key industrial sectors. A multi-pollutant treatment technology system of desulfurization, denitrification, and dust collection, which applies to key industries such as power plants, steel, and building materials, has been developed. High-performance materials for the treatment of different pollutants, such as denitrification catalysts and desulfurization absorbers, were developed. At the same time, multi-pollutant synergistic removal technologies for flue gas in various industries have also become a hot research topic, with important breakthroughs in the synergistic removal of NO x , SO x , and Hg. Due to the increasingly stringent emission standards and regulations in China, there is still a need to work on the development of multi-pollutant synergistic technologies and further research and development of synergistic abatement technologies for CO 2 to meet the requirements of ultra-low emissions in industrial sectors. [Display omitted] [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]

Air pollutant emissions represent a critical challenge in the green development of the non-ferrous metallurgy industry. This work studied the emission characteristics, formation mechanisms, phase transformation and separation of typical air pollutants, such as heavy metal particles, mercury, sulfur oxides and fluoride, during non-ferrous smelting. A series of purification technologies, including optimization of the furnace throat and high-temperature discharge, were developed to collaboratively control and recover fine particles from the flue gas of heavy metal smelting processes, including copper, lead and zinc. Significant improvements have been realized in wet scrubbing technology for removing mercury, fluoride and SO 2 from flue gas. Gas-liquid sulfidation technology by applying H 2 S was invented to recycle the acid scrubbing wastewater more efficiently and in an eco-friendly manner. Based on digital technology, a source reduction method was designed for sulfur and fluoride control during the whole aluminum electrolysis process. New desulfurization technologies were developed for catalytic reduction of the sulfur content in petroleum coke at low temperature and catalytic reduction of SO 2 to elemental sulfur. This work has established the technology for coupling multi-pollutant control and resource recovery from the flue gas from non-ferrous metallurgy, which provides the scientific theoretical basis and application technology for the treatment of air pollutants in the non-ferrous metallurgy industry. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, an integrated numerical model is presented and validated to investigate the particle charging and transport behaviors in a wire-plate electrostatic precipitator (ESP). Calculations of gas flow, electrostatics field and particle motions are coupled in the model, and the influences of electro-hydrodynamics (EHD) flows are also taken into account. The dynamic charging process of particles was treated with separate field and diffusion charging rates, and the trajectories of particles in the ESP were tracked with a Lagrangian-type method. Numerical results show that electric field strengths and charging ion densities varied largely in the computational domain, and inlet particles were initially charged primarily by diffusion charging mechanism. The particles were then charged to a near-saturation state in the discharging zone, while their transverse velocities showed considerable fluctuations along the trajectories. Numerical results indicate that particles with diameter between 0.2 and 1 μm normally exhibited lowest average transverse velocities, and longer residential time could slightly improve the transverse velocities for all sizes of particles. Moreover, increasing voltages could greatly improve the acquired charges and collecting performances for particles larger than 1 μm, while higher ion current value was more effective in achieving higher collection efficiencies for sub-micron particles. [ABSTRACT FROM AUTHOR]

Wet flue gas desulfurization systems (WFGD) are the most popular method to remove the SO 2 from the flue gas in China's power plants. Most WFGD systems contain an oxidation subsystem, which is one of the most important subsystems. In this paper, a hybrid modeling and operating optimization method of oxidation process of WFGD system is proposed, verified and applied on the WFGD system of a typical 1000 MW unit. The influence of important parameters such as the diameter of droplets or bubbles, the liquid-gas ratio or the gas-gas ratio (the ratio of between oxidized air flow rate and flue gas flow rate) and the height of the natural oxidation zone or the slurry level on natural oxidation rate and forced oxidation rate are further explored. The application results show that the above method can significantly reduce the operating energy consumption of the oxidation fan by more than 25 %. Furthermore, field tests are also carried out on the WFGD systems of 130 t/h and 220 t/h circulating fluidized bed (CFB) units. The energy consumption can be reduced by 30.6 % and 37.5 %, respectively. The results will be helpful to reduce the auxiliary power consumption and additional CO 2 emission of WFGD. [Display omitted] • Hybrid modeling method for oxidation process of WFGD system. • Influence of important parameters on natural oxidation rate and forced oxidation rate. • Operating optimization strategy of oxidation process with or without VFD. • Application on typical 1000 MW unit and two circulating fluidized bed (CFB) units. [ABSTRACT FROM AUTHOR]

The demand for gases detection has promoted extensive research into gas sensors. Sensor arrays can be used as electronic olfaction units for complex gas detection and identification. However, the gas sensing properties are affected by various factors. The multi-dimensional nature of those interactions is crucial for creating a sensor array with diverse responses, but it is also challenging to fabricate an array considering all these parameters, particularly in miniaturization. In this paper, we present a framework that can take multiple factors into consideration and help to fabricate an optimal array for gas identification. 32 sensors including different MOS materials (SnO 2 , In 2 O 3 , WO 3), morphologies (microsphere, nanoparticle, nanoflake), doped/loaded metals (Pd, Pt, Ce, Ru, Rb), and operational temperatures (250℃∼370℃) are discussed. A material-temperature-analyte-response database was then established by storing their response characteristics towards low ppm concentrations of ammonia, ethyl acetate, toluene, methanol, ethanol, and acetone. An optimized array was then constructed out of 10,518,300 possible combinations of materials and operational temperatures. Results showed improvements in discrimination ability and the optimized array integrated into the chip can provide vector signals with high selectivity, completely recognizing all the 6 target gases and even for their multi-component mixture after linear discriminant analysis transformation. [Display omitted] • An on-chip microarray platform considering multiple factors. • An effective and operational method to reasonably optimize the array. • A highly selective array capable of distinguish different gases and mixtures. [ABSTRACT FROM AUTHOR]