Clarifying the influence law and mechanism of fuel particle size on the operational performance of circulating fluidized bed (CFB) boilers is important for enhancing the operational flexibility of CFB, strengthening low-NOx combustion, and improving combustion performance. In this study, a one-dimensional CFB mathematical model validated by field test data was employed to calculate a 170 t/h CFB boiler. The model input parameters were obtained through ash formation and attrition experiments. The simulation results under different fuel particle size conditions show that when the fuel particle size range is reduced to 0-1 mm from the conventional one, the bed material particle size decreases greatly and the material concentration in the dilute-phase zone increases, and the circulating flow rate increases by 28.5%; the reducing atmosphere in the furnace is enhanced, and the original emission concentration of NOx is reduced by about 17%; meanwhile, the combustion state in the furnace is improved, with the heat loss of incomplete solid combustion reduced by 26.3%. This research is conducive to optimizing the design and operation of CFB boilers.

Electrocatalytic CO2 reduction to ethanol in neutral electrolytes represents a promising pathway for carbon neutrality, yet the selectivity remains unsatisfactory due to inefficient C & horbar;C coupling and competitive hydrocarbon production. Herein, a copper oxide catalyst with enriched amorphous-crystalline interfaces (IR-CuOx) exhibits differential Cl- affinity, effectively steering the CO2 reduction pathway toward ethanol. The obtained IR-CuOx catalyst achieves a remarkable ethanol Faradaic efficiency (FE) of 56.77% at -1.1 V vs. reversible hydrogen electrode (RHE) in 0.1 m KCl electrolyte. Impressively, with IR-CuOx as the cathode, the integrated membrane electrode assembly (MEA) electrolyzer could stably operate for over 70 h under an industrial-level current density of 200 mA & centerdot;cm-2, with ethanol FE remaining above 45%. Experimental characterizations and theoretical calculations demonstrate that the differential Cl- affinity over amorphous-crystalline interfaces synergistically combines the *CO hydrogenation capability at weak Cl- affinity sites with the enhanced C & horbar;C coupling capability at strong Cl- affinity sites, favoring asymmetric *CO-*CHO coupling to generate the key *CHCOH intermediate. Additionally, the differential Cl- affinity further strengthens the C & horbar;O bond and weakens the Cu & horbar;C interaction, facilitating the hydrogenation of *CHCOH toward ethanol. This work offers fundamental understandings of surface anion adsorption behaviors for designing efficient electrocatalysts toward neutral CO2-to-ethanol conversion.

High-temperature superheater bends in circulating fluidized bed (CFB) boilers are subjected to coupled pressure–temperature variations under deep peak-regulation operation, which may induce local stress concentration and structural reliability risks. In this study, representative quasi-steady operating conditions were extracted from the peak-regulation process of a 300 MW CFB boiler, and local steady thermal-structural coupled models were established for high-temperature superheater bends. The thermal boundary conditions of the local models were determined by combining global and local thermal calculations based on practical operating data, while the support constraints were assigned according to the actual fixation arrangement. The results show that, within the investigated temperature variation range, the stress level of the bend structure is mainly associated with the working-fluid pressure, whereas temperature affects the material allowable stress and safety margin. During load reduction from 100% BMCR to 3% BMCR, the maximum stress of the original 90° single-bend structure decreased from 142.84 MPa to 81.46 MPa, with critical stress regions mainly located at the inlet support and bend section. Structural optimization indicated that increasing the single-bend angle could alleviate inlet stress concentration, although the overall stress reduction remained limited. By contrast, the optimized 45° double-bend configuration provided a more effective stress-relief mechanism, reducing the maximum stress from 142.84 MPa to 93.52 MPa under the high-load condition and decreasing the stress difference between representative operating conditions. A supplementary stress-range-based fatigue-damage indication further showed that the optimized structure reduced the relative fatigue-damage tendency by approximately 71.9%–94.8% when the fatigue exponent varied from 3 to 7. These findings provide a practical case-based reference for thermal-structural reliability assessment, structural optimization, and reduction in relative fatigue-damage tendency of high-temperature superheater bends in CFB boilers under flexible operating conditions.

With the steadily increasing production of Municipal Solid Waste (MSW) and the growing emphasis on its resource recovery, pyrolysis technology is attracting increasing attention due to its scalability, high reliability, and low emissions. Nevertheless, the influence of pressure and oxygen concentration on pyrolysis mechanisms remains inadequately understood. This study employed a pressurized thermogravimetry-mass spectrometry (TG-MS) system to investigate mass loss behavior and gaseous product evolution from three typical MSW components-rice, sawdust, and plastic pellets-under varied pressures and oxygen levels. Results indicated that rice and sawdust pyrolysis occurs in three distinct stages: drying, dry distillation, and gas generation, while plastics exhibit single-stage decomposition within a narrow range of 410-510 degrees C. Analysis of gas evolution peak temperatures revealed that CO2 release precedes that of H2 and CH4 in biomass, whereas plastic pyrolysis generates H2 at significantly higher temperatures. Under an anoxic atmosphere, increasing pressure is unfavorable for the pyrolysis of all three waste types. As pressure increases, the mass loss rates of the three materials decreases, and the calorific value of the volatile gas generally shows a downward trend. Elevated pressure increased the peak release temperatures of gaseous products, suppressing primary decomposition and shifting reaction pathways. Under an oxygen-containing atmosphere, increasing oxygen volume fraction promotes the pyrolysis conversion of all three types of waste, lowered the peak temperatures of combustible gases, and raising the mass loss rates and calorific value (delta h, the combustion heat of combustible gases per unit mass of the sample). However, when the total pressure increased under constant oxygen partial pressure (altering the oxygen volume fraction), the peak release temperatures of gaseous products from all three wastes increased, indicating that oxygen partial pressure is not the dominant factor in waste pyrolysis characteristics. This work provides fundamental insights essential for optimizing thermal treatment of mixed waste.

Structure of return leg has significant effects on the solid circulation performance as well as the particle residence time of the circulating fluidized bed (CFB) reactor. This study introduces a novel concept for the return leg to achieve reaction decoupling. Five novel designs (named as N = 1-5) are proposed and evaluated. To assess their performance, a CPFD model is developed and subsequently validated through single-particle and group-particle experiments. The results demonstrate that all five new return leg designs can modify the particle average residence times (ARTs) and residence time distributions (RTDs) to varying degrees. Among them, design N = 5 is identified as the optimal configuration due to its unique circuitous design, which enhances its effectiveness in altering particle flow dynamics. Utilizing this configuration, this study investigates the effects of return leg geometrical configurations, particle size distributions (PSDs), and auxiliary fluid inlet velocities on gas-solid flow dynamics and particle residence time. The pilot-scale simulation confirms the feasibility of the return leg for achieving reaction decoupling, with the particle residence time ranging approximately from 10 s to 110 sand an ART of 22.7 s. This research provides valuable insights into the design and optimization of return legs in CFB reactors for enhanced reaction decoupling and particle flow control, highlighting the potential of the proposed configurations for practical engineering applications.

Clarifying the influence law and mechanism of fuel particle size on the operational performance of circulating fluidized bed (CFB) boilers is important for enhancing the operational flexibility of CFB, strengthening low-NOx combustion, and improving combustion performance. In this study, a one-dimensional CFB mathematical model validated by field test data was employed to calculate a 170 t/h CFB boiler. The model input parameters were obtained through ash formation and attrition experiments. The simulation results under different fuel particle size conditions show that when the fuel particle size range is reduced to 0–1 mm from the conventional one, the bed material particle size decreases greatly and the material concentration in the dilute-phase zone increases, and the circulating flow rate increases by 28.5%; the reducing atmosphere in the furnace is enhanced, and the original emission concentration of NOx is reduced by about 17%; meanwhile, the combustion state in the furnace is improved, with the heat loss of incomplete solid combustion reduced by 26.3%. This research is conducive to optimizing the design and operation of CFB boilers.

With the continuous deepening of green power production and supply and the increasing proportion of new energy power generation, thermal power units are transitioning to a role that emphasizes both basic security and system regulation. Supercritical circulating fluidized bed (CFB) boilers, due to their unique flexibility advantages, need to undertake deep peak regulation tasks. Therefore, based on the Computational Particle Flow Dynamics (CPFD) method, a 350 MW supercritical CFB boiler was taken as the research object, and detailed simulation studies on the gas-solid flow, combustion, and heat transfer characteristics in the furnace were carried out under wide load conditions ranging from 30% to 90%. The three-dimensional particle mass concentration distribution, the flow uniformity of parallel multi-loop systems, the three-dimensional temperature distribution, and the distribution law of heat transfer coefficients on water-wall heating surfaces under different loads were specifically analyzed, and the NOx formation and emission characteristics were discussed. The results show that as the boiler load increases, the circulating flow rate increases, the particle mass concentration in the upper part of the furnace increases, and the axial S-shaped solid mass concentration distribution tends to be gentler. At the same time, the temperature difference between the upper and lower parts of the furnace decreases, the uniformity of temperature distribution is enhanced, and the axial attenuation rate of the heat transfer coefficient decreases. In the depth direction of the furnace, the particle mass concentration at the rear wall is higher than that at the front wall, the temperature is lower than that at the front wall, and the heat transfer coefficient is higher than that at the front wall. Moreover, the higher the load, the greater the mass concentration difference between the side-wall and central regions. In the width direction, the distributions of particle mass concentration and temperature show obvious symmetry, but in the middle and upper parts of the furnace, affected by suspended heating surfaces such as water-cooling screens and superheaters, each parameter shows a wave-like distribution. Notably, the gas-solid mass flow rate of the middle separator is lower than that of the side separators, and the “one-to-two” structure of the return valve leads to a reduction in the flow uniformity of the parallel loops. Under low-load conditions, the uniformity of particle flow among the parallel multi-loops is improved, but the deviation of heat transfer coefficients on each wall of the water-wall further increases. In addition, along the height direction of the furnace, the NOx mass concentration shows a trend of first increasing and then decreasing. As the load decreases, the original NOx emission mass concentration shows a characteristic of first decreasing and then increasing, with the inflection point occurring at approximately 50% load.

Circulating fluidized bed (CFB) combustion provides a promising approach for utilizing low-grade solid fuels such as coal gangue (CG) and lignite. However, the complex interactions during co-combustion and ash melting remain insufficiently understood. The co-combustion characteristics and ash melting behavior of CG, lignite, and their blends were investigated. Blending lignite significantly enhanced combustion performance of CG. Thermogravimetric analysis revealed that the ignition temperature of CG decreased from 648 degrees C to 276 degrees C, while the peak combustion rate increased from 5.49%/min to 21.25%/min at 50% lignite ratios. The comprehensive combustion index increased by over two orders of magnitude. Kinetic analysis demonstrated a reduction in apparent activation energy decreased from 137.88 kJ/mol (pure CG) to 39.09 kJ/mol (80% lignite), indicating synergistic effects. Thermomechanical analysis revealed that CG exhibited high ash melting temperatures, while lignite showed significantly lower values. The 25% displacement temperature exceeded 863 degrees C for CG but was only 705 degrees C for lignite. Lignite addition led to a noticeable decline in ash melting temperatures and induced significant changes in ash chemistry by promoting the formation of low-melting leucite (KAlSi2O6), as confirmed by X-ray diffraction and thermodynamic modeling. These findings provide valuable guidance for optimizing the utilization of low-grade fuels in CFB combustors.

Lake sediment is a high moisture solid waste that carries a large amount of water pollutants, significantly impacting the environment and urban landscape. The efficient management of lake sediment has emerged as a critical challenge requiring immediate attention. This paper focuses on the characteristics of co-combustion and its pollutant emissions. The combustion characteristics of mixed combustion of lake sediment and coal in different proportions were obtained by the thermogravimetric method. Experiments elucidated the influence of diverse factors on the variability of NO and SO2 concentrations. The remaining bottom residue of the reaction and the reasons for the changes in emission concentration are analysed from a microscopic perspective. Results indicate that the appropriate proportion (<20 %) of mixed lake sediment promotes coal combustion. NO and SO2 decrease with increased bed temperature, lake sediment mixing ratio (5 %-15 %), and particle size. As the bed temperature increases, the particle surface melts, reducing the pore structure and reaction sites, thereby reducing the generation of pollutants. When the mixing ratio exceeds 15 %, NO increases while SO2 decreases. Calcium based substances have little catalytic effect on NO, but are still effective for SO2. Larger particles will promote the decomposition of NO on their surface.

Since the mineral distribution of the crushed powdered coal (0-1 mm) differs from that of the sieved powdered coal (0-1 mm), the traditional ash formation characterization method may not apply to the powdered coal-fired circulating fluidized bed (PC-CFB) boiler. Traditional ash formation and powdered coal ash formation experiments were carried out respectively. Results show that the primary ash particle size distribution of the crushed powdered coal is quite different from that of sieved powdered coal. Additionally, the attrition characteristics are related to raw coal size before crushing. The test of physical and chemical properties of ash indicates that the above phenomena can be attributed to the large discrepancy in chemical composition and mineral phases between the two kinds of powdered coal. Finally, the analysis method and data on ash formation and attrition characteristics applicable to PC-CFB boilers are proposed, which facilitate the mathematical modeling of this novel CFB combustion technology.

Coal-derived sludge, a solid waste produced by the coal industry, offers potential opportunities for resource recovery due to its high organic matter. However, its products face challenges related to low utilization efficiency and economic value. Effective and clean treatment of coal-derived sludge is essential for sustainable development. Herein, we studied the co-pyrolysis treatment of coal-derived sludge and low-rank coal at different temperatures (500 degrees C-900 degrees C) and pretreatment methods (mechanical mixing and hydrothermal co-treatment). The co-pyrolysis of sludge and coal could increase the pyrolysis char yield and H2 yield, as well as reduce CO2 emissions. The hydrothermal co-treatment significantly improved the cleanliness of the co-pyrolysis treatment. Then we conducted a comprehensive analysis of the properties of the pyrolysis char using different characterization techniques. In order to better evaluate the distribution of co-pyrolysis product yield, six machine learning models were developed to predice co-pyrolysis char yield. The best model-predicted values showed excellent predictive performance when compared to the experimental values at high pyrolysis temperatures (>= 700 degrees C). This study provided a new perspective on the resource utilization of coal-derived sludge and low-rank coal.

Operation safety, combustion efficiency, and pollutant emissions of circulating fluidized bed (CFB) boilers are significantly affected by the lateral gas-solid flow uniformity, which can be featured by the voidage (epsilon g) as well as particle lateral movement velocity (up). To obtain abundant data to support quantitative analysis and modeling, the gas-solid flow details in a 170 t/h CFB boiler were numerically simulated using the computational particle fluid dynamics (CPFD) method, which has been validated by field test data. Based on the original simulation data set, simple models for the prediction of lateral profiles of epsilon g and up were developed. In addition, both theoretical model and genetic algorithm-back propagation (GA-BP) neural network were applied to predict the lateral solids movement behavior. Results show that both two models exhibit excellent prediction accuracy with the coefficient of determination (R2) exceeding 0.99. While the theoretical model derived from physical equations is relatively simple and has a clear physical meaning. All the simple models developed in this paper can be embedded into the overall CFB mathematical model framework, facilitating the comprehensive analysis of the operational characteristics for large-scale industrial CFB boilers.

W-flame boilers are widely used to burn low-volatile coals such as anthracite but often face high nitrogen oxides (NOx) emissions due to intense combustion near the lower furnace. This study investigates NO(x )formation in a 660 MW supercritical W-flame boiler using validated high-fidelity simulations, with a focus on how secondary air injection beneath the arch influences combustion behavior. A key outcome of this work is the development of a quantitative and reliable control method based on the dimensionless height of the peak-temperature zone (h). This parameter captures the spatial position of the high-temperature region and shows a strong correlation with NOx emissions. Lower or negative h values, indicating a shift of peak-temperature zone below the throat, result in more uniform combustion and lower NO(x )formation. The study further demonstrates that adjusting the Y-direction momentum, especially through sub-arch airflow and injection angle, provides a practical means to control h, linking airflow regulation with emission outcomes. Together, these insights form a physics-based control tool that bridges operational parameters and combustion dynamics. It offers a structured, real-time approach for optimizing flame structure and reducing NOx, enabling more efficient and cleaner operation of W-flame boilers.

Titanium dioxide-based photocatalysts have garnered significant attention for CO2 reduction reactions (CO2RR) toward fuel production, with noble metal incorporation markedly enhancing photocatalytic efficiency. However, the development of cost-effective alternatives to expensive metals (e.g., Au, Ag) remains a critical challenge. Herein, amorphous copper nanoparticles (a-Cu NPs) were successfully anchored onto anatase TiO2 via a chemical reduction method using Cu(NO3)23H2O as the precursor. The optimized 4 wt % a-Cu/TiO2 catalyst (4CT) demonstrated remarkable activity, achieving methane and CO production rates of 3.0 and 18.4 mu molg-1h-1, respectively, corresponding to 10.0-fold and 7.3-fold enhancements over pristine TiO2. CO2-TPD revealed that the high surface disorder of a-Cu NPs significantly strengthened CO2 chemisorption. In situ Fourier transform infrared spectroscopy (FTIR) further indicated that a-Cu loading enabled preferential CO2 adsorption over H2O on TiO2 surfaces while accelerating the formation of the key intermediate *COOH. This work proposes a synergistic strategy integrating nonprecious metal modification with interfacial engineering, offering a cost-effective pathway to develop high-performance photocatalysts for sustainable CO2 conversion.

[Purposes] The content of Al2O3 in the fly ash and slag after combustion of Zhungeer coal is over 45%, which has important value of comprehensive utilization of resources. In order to solve the problems of poor fly ash activity and low Al2O3 extraction efficiency when using Zhungeer coal in conventional circulating fluidized bed boilers, a coal water slurry circulating fluidized bed combustion method was proposed to improve the ash characteristics. [Methods] The effects of feed mode, operating oxygen content, bed temperature, and primary air rate on unburned combustible in fly ash were studied by using a 3 MW circulating fluidized bed combustion test facility, the composition and micro-morphology of fly ash with different particle sizes were analyzed by using specific surface area and pore diameter analysis apparatus, scanning electron microscope, X-ray fluorescence spetrometer, and X-ray diffractometer (XRD). [Findings] The results show that the unburned combustible content in fly ash decreases with the increase of bed temperature, operating oxygen content, and primary air rate, and the unburned combustible content in fly ash in coal water slurry granulated combustion is obviously lower than that in ungranulated combustion. The combustibles in fly ash are mainly below 40 μm, and the unburned combustible content increases with the decrease of fly ash particle size. Most of small fly ash particles were composed of undeveloped pore structure particles with high combustible content. The BET specific surface area and total pore volume decrease with the increase of fly ash particle size, while the average pore size increases gradually, and the total pore volume and the average pore size of the slack coal slurry are smaller than those of the clean coal slurry. It can be found that the content of Al2O3 increases with the decrease of particle size, and the content of Al2O3 in fly ash with particle size less than 15 μm is 51.77%. Acctording to the phase retrieval and semi-quantitative analysis of ash samples, the γ-Al2O3 peak with higher activity is gradually weakened with the increase of particle size, the mullite content is gradually increased with the increase of particle size, and the aluminum extraction efficiency of fly ash decreases. As a whole, in fly ash with particle size less than 50 μm, the content of Al2O3 is higher and the content of mullite is lower, making it more suitable to be used as raw material for aluminum extraction process.

For thermal energy storage reactors with gas-solid bubbling fluidized bed, the bubbles have important effects on the heat and mass transfer capabilities as well as temperature homogeneity. Therefore, it is necessary to investigate the bubble dynamic behaviors, which is affected importantly by the particle size, for the design, and operation of bubbling fluidized bed reactors. In the present work, four particles with narrow size were sieved as the bed materials to study the effects of particle size on bubble dynamic behaviors at superficial gas velocity of 0.56 m & sdot;s- 1 in a quasi-two-dimensional (quasi-2D) fluidized bed. The bubble dynamic behaviors, including bubble equivalent diameter, bubble size distribution, average bubble density, bubble aspect ratio, bubble holdup, bed expansion ratio, bubble velocity, and bubble rising angle, at full bubbling fluidization were derived by digital image analysis (DIA) post-processing technique. The results shown that the bubble equivalent diameter increased with the increasing of particle size. For four particles, the bubble size distributions shown the similar distribution features, which indicated that the particle size had rare effects on it. Near the air distributor and freeboard, with increasing particle size, the average bubble density increased. The modes of bubble aspect ratio were all lower than 1, indicating that most of bubbles were vertically oblong ellipse. Additionally, the mode of the bubble aspect ratio tended to increase with the increasing of the particle size. Both time-averaged bed expansion ratio and bubble hold-up increased with increasing particle size. Bed fluctuation of smaller particles was more intense, but it was converse for the bubble hold-up. Inside the fluidized bed, two uniform "coreannular" flows were formed, and there was no evident difference in the radial distribution among four particles. Additionally, the particle size had little effects on the bubble rising velocity, which increased with increasing bubble equivalent diameter only, and proposed correlation with velocity coefficients of 1.09 was in line with the correlation coefficients in the literatures. Depending on the bubble rising angle, the bubble movement from the biased random movement to the main upward movement was dominant. Mastering the effects of particle size on bubble dynamic behaviors comprehensively is beneficial for the design, operation, and optimization of thermal energy storage reactors with gas-solid bubbling fluidized bed

In order to explore the combustion characteristics of the biomass vibrating grate furnace and realize the control and optimization of the unit combustion process,the mechanism model of the grate combustion process was established through the analysis of the biomass fuel characteristics and combustion mechanism.Moreover,the dynamic change of the grate fuel amount was studied,and the key parameters such as furnace temperature and flue gas oxygen content were predicted.The influence of periodic vibration of grate on combustion state in furnace was discussed.The results show that the amount of fuel in the grate is related to the current feed rate and fuel burning rate.The fuel has a large storage capacity on the grate,which leads to a large delay between the fuel burning and the current feeding.The predicted values of furnace temperature and flue gas oxygen content can follow the measured values well,and their changes are in accord with the combustion characteristics.The periodic vibration of the grate will cause the periodic change of the combustion state in the furnace.When the grate vibrates,the fuel combustion speed,furnace temperature,furnace pressure will increase,and the oxygen content of the flue gas will be reduced.As the vibration of the grate stops,these parameters return to the steady state level.

Bubble dynamics properties play a crucial and significant role in the design and optimization of gas-solid fluidized beds. In this study, the bubble dynamics properties of four B-particles were investigated in a quasi-two-dimensional (quasi-2D) fluidized bed, including bubble equivalent diameter, bubble size distribution, average bubble density, bubble aspect ratio, bubble hold-up, bed expansion ratio, bubble radial position, and bubble velocity. The studies were performed by computational particle fluid dynamics (CPFD) numerical simulation and post-processed with digital image analysis (DIA) technique, at superficial gas velocities ranging from 2umf to 7umf. The simulated results shown that the CPFD simulation combining with DIA technique post-processing could be used as a reliable method for simulating bubble dynamics properties in quasi-2D gas-solid fluidized beds. However, it seemed not desirable for the simulation of bubble motion near the air distributor at higher superficial gas velocity from the simulated average bubble density distribution. The superficial gas velocity significantly affected the bubble equivalent diameter and evolution, while it had little influence on bubble size distribution and bubble aspect ratio distribution for the same particles. Both time-averaged bubble hold-up and bed expansion ratio increased with the increase of superficial gas velocity. Two core-annular flow structures could be found in the fluidized bed for all cases. The average bubble rising velocity increased with the increasing bubble equivalent diameter. For bubble lateral movement, the smaller bubbles might be more susceptible, and superficial gas velocity had a little influence on the absolute lateral velocity of bubbles. The simulated results presented a valuable and novel approach for studying bubble dynamics properties. The comprehensive understanding of bubble dynamics behaviors in quasi-2D gas-solid fluidized beds would provide support in the design, operation, and optimization of gas-solid fluidized bed reactors.