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Air samples were collected at the Lianhu (urban) and Yanta (semi-urban) regions between January 2020 and December 2023 to determine the concentrations of polycyclic aromatic hydrocarbons (PAHs) in Xi’an, which is an important tourist city in China. The concentration of PAHs was ascertained using liquid chromatography. The concentration of Σ16PAHs in Xi’an was 0.13–105.02 ng/m3, while the concentration of Σ16PAHs for the sampling regions at Lianhu and Yanta were 0.13–105.02 ng/m3 and 0.34–82.64 ng/m3, respectively. PAHs with 4–5 rings were the predominant PAHs pollutants in Xi’an, mainly from coal combustion and automobile exhaust. Risks through inhalation to three groups, adult males, adult females, and children, were estimated. The incremental lifetime cancer risk (ILCR) value for local adults and children were less than 10−6, considered to be at a safe level. However, the ILCR is relatively close to the minimum risk threshold (10−6), and it still needs to be highly valued. [ABSTRACT FROM AUTHOR]

Dietary uptake is the main pathway of exposure to polycyclic aromatic hydrocarbons (PAHs). However, there is no data regarding the pollution and health risks posed by PAHs in Lilium davidii var. unicolor. We measured the concentrations of 16 PAHs in lily bulbs from Lanzhou; analyzed the bioaccumulation, sources, and pollution pathways of PAHs; assessed the influence of baking on PAH pollution in the bulb; and assessed the cancer risks associated with PAH exposure via lily consumption. The total PAH concentrations in raw bulbs were 30.39–206.55 μg kg-1. The bioconcentration factors of total PAHs ranged widely from 0.92 to 5.71, with a median value of 2.25. Pearson correlation analysis revealed that the octanol-water partition coefficients and water solubility values played important roles in the bioaccumulation of naphthalene, fluorene, phenanthrene, pyrene, and fluoranthene in the raw bulb by influencing PAH availability in soil. Correlation analysis and principal component analysis with multivariate linear regression indicated that biomass and wood burning, coal combustion, diesel combustion, and petroleum leakage were the major sources of PAHs in the raw bulbs. The paired t-test showed that the PAH concentrations in the baked bulbs were higher than those in the raw bulbs. PAH compositions in lily bulb changed during the baking process. Baked bulbs exhibited a higher cancer risk than raw bulbs. Local adults had low carcinogenic risks from consuming lily bulbs. This study fills the knowledge gap about PAH pollution and the related health risks of PAHs in the Lanzhou lily. [ABSTRACT FROM AUTHOR]

The complex disaster of gas and coal spontaneous combustion is a major challenge in coal gob, especially under conditions of three-dimensional extraction. Taking the 15,101 mining face in Shigang Mine as the field background, COMSOL Multiphysics software was employed to construct models of airflow, methane migration, and stress distribution in gob under the stereo extraction method of "U+high-low level roadway." The range of oxidation zone was divided by combining the oxygen concentration and wind velocity field. The results showed that the methane can be discharged through the low-level airway and the return airway, and most of the methane at the top area in gob can also be discharged from the high-level roadway, indicating that the stereo ventilation was beneficial for methane dilution at both the upper and lower region. However, the oxidation zone in the middle of gob was the widest and closed to the mining face, it on the return side was narrower than intake side, and its distribution range was closer to the mining face. And finally, the range of the oxidation zone expanded with the increase in height in the vertical direction. These indicate the dangerous area for preventing gas and coal spontaneous combustion disasters in gob. [ABSTRACT FROM AUTHOR]

Pyrolysis is highly regarded as a means to produce smokeless briquettes. This study investigated the effects of torrefaction and fast pyrolysis on the physicochemical and combustion characteristics of coal and biocoal briquettes. Biocoal briquettes were prepared with coal dust and rice husks using cassava starch gel as a binder, whereas no biomass was used for coal briquettes. The feedstocks were compacted in a briquetting machine and then dried in a solar dryer before pyrolysis in a muffle furnace fitted with a vacuum system. The proximate compositions were derived from thermogravimetric analysis (TGA), and the calorific values were calculated. The combustion characteristics were determined through thermogravimetry (TG-DTG) analysis. The functional groups were analyzed via Fourier transform infrared (FTIR) spectroscopy. The results revealed that biocoal briquettes with coal-to-rice husk ratios of 50:50 and 60:40, which were subjected to torrefaction for 30 min at 200°C, had the same volatile matter content (12%), but differed in other properties. The pyrolyzed coal briquette exhibited the highest flammability and combustion indices. Furthermore, some transmittance peaks shifted to lower or higher frequencies. This study demonstrates that the the properties of pyrolyzed briquettes are influenced by the pyrolysis temperature, feedstock and blending ratio. [ABSTRACT FROM AUTHOR]

To study the micro-morphological characteristics of PM2.5 and its effect on ambient air quality, a 7500F scanning electron microscope (SEM) was utilized in this study to examine the micromorphology and elemental composition of PM2.5 and its impact on ambient air quality during heavily polluted weather in Yining City in the winter of 2018–2019. The results revealed the presence of numerous large solid shapes, small strip shapes, and a few irregular shapes. Additionally, the quantity of PM2.5 particles adsorbed on the glass fiber filter membrane was high, indicating a significant impact of PM2.5 particles on the urban area. Based on the analysis of particulate matter, heating time, and environmental conditions of samples during the winter heating season, it was concluded that the PM2.5 sample is rich in N, S, P, C, Na, Ge, Rb, Zn, Fe, Mg, Al, Mo, Pt, and Pb. The findings suggest that the urban area is predominantly influenced by industrial dust, road dust, construction cement dust, vehicle exhaust dust, and coal combustion during winter heating. The analysis and evaluation of the sample data indicate that PM2.5 in the urban area is influenced by human activities. [ABSTRACT FROM AUTHOR]

The construction of a predictive model that accurately reflects the spontaneous combustion temperature of coal in goaf is fundamental to monitoring and early warning systems for thermodynamic disasters, including coal spontaneous combustion and gas explosions. In this paper, on the basis of programming temperature experiment and industrial analysis, 381 data sets of 9 coal types are established, and feature selection was executed through the utilization of the Pearson correlation coefficient, ultimately identifying O2, CO, CO2, C2H4, C3H8, C3H8/CH4, C2H4/CH4, C2H4/C3H8, CO2/CO, and CO/O2 as input indicators for the prediction model. The chosen indicator data were divided into training and testing sets in a 4:1 ratio, the Particle Swarm Optimization (PSO) methodology was applied to optimize the parameters of the XGBoost regressor, and a universal PSO-XGBoost prediction model is proposed. A tenfold cross-validation method was employed to assess performance of PSO-XGBoost, PSO-RF, PSO-SVR, XGBoost, RF, and SVR models separately, the results underscored the superior predictive accuracy, robustness, fault tolerance, and universality of the PSO-XGBoost model. [ABSTRACT FROM AUTHOR]

Coal spontaneous combustion is a complex physicochemical process that can cause financial losses and fatalities. Because of this, scholars from all around the world have thoroughly examined its projections, procedures, and preventative measures. In order to better utilize coal resources and systematically understand the state of research and frontier trends in this area, this study thoroughly examines and analyzes 2,172 papers using bibliometric methodologies, CiteSpace, and VOSviewer software. The results demonstrate that research on coal spontaneous combustion has progressed through three stages: data accumulation, stable development, and rapid advancement, with increasing influence over time. The US, Australia, and China are the three countries that conduct the most research. The primary areas of study in this topic include environmental safety, chemical mechanisms, and energy utilization. The primary knowledge domain includes preventative techniques, microscopic mechanics of spontaneous combustion, and coal oxidation reactions. Current research hotspots are centered on low-temperature oxidation of coal, prediction of spontaneous combustion processes, and prevention and control strategies. Research is steadily moving toward more in-depth investigation at the microscopic level and the creation of new materials, particularly in fields like coal oxidation, microscopic mechanisms of spontaneous combustion, and the creation and enhancement of novel inhibitors. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) foam ceramics demonstrate excellent filtration efficiency as filter supports due to their complex pore network and chemical stability. However, their fabrication demands high sintering temperatures (above 2100 °C), resulting in substantial energy consumption and production costs, which restricts their wider use in separation and purification application processes. To address this, we utilized fly ash, a by-product of coal combustion rich in inorganic Al₂O₃, as a sintering aid to develop a porous silicon carbide–alumina foam ceramic (SAFC) and investigated the effects of Al₂O₃ on its performance. Additionally, we introduced SAFC as an adsorbent material, synthesizing the fluoride adsorbent (La@SAFC) and evaluating its fluoride removal efficacy through batch experiments. Results indicate that Al₂O₃, as a sintering aid, promotes the sintering process by forming a liquid phase that enhances Si and C diffusion at lower sintering temperatures. SAFC containing 16 wt% Al₂O₃ achieved optimal porosity, low bulk density, and compressive strength at a sintering temperature of 1150 °C. The addition of Al₂O₃ also facilitated mullite formation, significantly enhancing the ceramic's mechanical properties. However, excess Al₂O₃ can produce an overabundant liquid phase and gas release, potentially compromising the mechanical integrity of SAFC. Batch experiments revealed that La@SAFC exhibited strong fluoride removal from water containing competing ions across a pH range of 3–7, achieving effluent within strict discharge standards. Mechanism analysis suggested fluoride removal via ion exchange and electrostatic interaction. La@SAFC maintained high fluoride removal efficiency across five regeneration cycles, underscoring its promise for practical applications. [ABSTRACT FROM AUTHOR]

As the global population grows, there is an increase in municipal solid waste (MSW) generation. This makes MSW gasification for hydrogen production increasingly important. This paper describes an innovative system that integrates MSW and coal power plant through gasification and pulverization to convert them into electrical energy and hydrogen. The effect of injecting hydrogen produced from MSW gasification into a coal combustion chamber as extra fuel has been analyzed. The produced hydrogen is divided, 60% of the hydrogen is utilized to reduce CO emissions in a coal boiler, while the remaining 40% is stored for different applications. The difference between the flue gas from a coal combustion chamber with hydrogen injection (MSWHCPP) and without hydrogen injection (CPPWH) is explored through sensitivity analysis with Aspen plus. The effect of injected hydrogen percent on the content of components of flue gas such as: CO, CO 2 , H 2 , H 2 S, SO 3 and SO 2 concentrations is investigated. The results show that increasing hydrogen injection under the same conditions leads to a decrease in CO, H 2 S, and SO 2 concentrations in the flue gas, while the concentrations of SO 3 and CO 2 increase. Following MSW gasification, 16093.9 kg/h of hydrogen is produced. Consequently, this leads to a reduction in the CO flow rate from 2947 kg/h to 761.5826 kg/h. Hydrogen injection positively impacts the combustion chamber conditions. [Display omitted] • Produce hydrogen from municipal solid waste gasification and water gas shift reaction. • Inject hydrogen into a combustion chamber of coal power plant. • Roles of hydrogen blending on flue gas components (CO) investigated. • Compare various coal type with different ultimate and proximate analysis. • The energy and exergy efficiency of the whole system are 55.2 % and 50.38 %. [ABSTRACT FROM AUTHOR]

This study delves into the environmentally responsible application of bottom ash (BA), a prevalent waste product from coal combustion in power plants, which constitutes 15% - 25% of total coal ash in Malaysia. The improper disposal of BA is a significant environmental hazard, with the potential to contaminate groundwater and soil, thereby affecting biodiversity and land usability. This study focuses on the novel application of BA in high early strength-self compacting brick (HESSCB), known for its rapid strength development and satisfactory flow properties, eliminating the requirement for mechanical vibration during placement. The research meticulously evaluates the substitution of BA for sand in HES-SCB, with a special focus on its influence on the fresh and physico-mechanical characteristics of the bricks. Among various mixes, the 20% BA replacement level emerged as the most significant, demonstrating a superior balance of rheological and physico-mechanical properties, thereby underscoring BA's viability as a sustainable fine aggregate substitute in HES-SCB production. This mix is designated as HES-SCB due to its distinct properties: achieving high early strength essential for rapid construction processes and exhibiting selfcompacting qualities that ensure ease of use and uniformity in application. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the efficiency and energy release characteristics of different types of coal in pulse detonation engines (PDE) to advance the development of deep coal fluidization detonation technology, achieving more efficient and cleaner coal utilization. Using a custom PDE setup, experiments were conducted with four coal types at mass flow rates from 30 to 120 g/s. High-frequency pressure sensors assessed pressure dynamics and detonation wave propagation, complemented by numerical simulations for accuracy. Results show that the maximum detonation pressure (Pmax) increases linearly with coal mass flow, with anthracite reaching 1.52 MPa at 120 g/s. A consistent linear relationship between Pmax and maximum temperature (Tmax) was observed. Detonation combustion efficiency (ηDCE) improved with mass flow, with peat rising from 52.3% to 83.7%. These findings provide a foundation for advancing deep coal fluidized detonation technology, contributing to more efficient and cleaner coal utilization. [ABSTRACT FROM AUTHOR]

Xinjiang is a region of China that suffers severe energy resource loss and air pollution resulting from long-term coalfield fires in near-surface inclined coal seams. Beneath these fire areas, abandoned mined-out goaf is common. Accidents easily occur during the treatment of such fire areas owing to the instability of strata overlying the goaf. Here, we carried out non-destructive exploration of the goaf below a fire area using the airborne transient electromagnetic method, accurately identifying the locations and sizes of 21 goaf areas. We then established a stratigraphic model using the thermal-solid coupling function in UDEC software. Our simulations showed that under the combined action of high temperature generated by coal combustion and high pressure generated by fire-fighting machinery, the maximum displacement and vertical stress in strata overlying the goaf were 1.42 m and 36 MPa, respectively. Such large displacement and stress values inevitably lead to the destabilization of overlying strata via turning, sliding, and tipping, seriously threatening the safety of mining personnel and machinery. In the field, the rock layer above the goaf was first accurately blasted, and then fire extinguishing was carried out after the overlying rock had collapsed and compacted. [ABSTRACT FROM AUTHOR]

Atmospheric elements can cause harmful effects on air quality and human health. Despite extensive research on PM2.5, there remains a limited understanding of the seasonal variations, origins, and associated health risks of specific elements in urban areas of the North China Plain. PM2.5 samples across four seasons were collected to investigate the seasonal variations, provenance, and health risks of 18 elements in urban Liaocheng. The concentrations of PM2.5 and total detected elements (TDEs) exhibited distinct seasonal patterns, with the biggest values occurring in winter, followed by spring, autumn, and summer. Fe, Ca, Al, and K were the most plentiful elements throughout the campaign, contributing 72.2% of TDEs. The enhanced concentrations of crustal elements were due to frequent dust storms in spring. Results from positive matrix factorization suggested that the dust source was only identified in spring, accounting for the largest percentage (37.0%), while secondary oxidation made the most significant contribution (34.6%) in summer, facilitated by higher temperatures and stronger sunshine. The relative abundance (41.6%) of biomass burning was highest in autumn, ascribed to intensified agricultural waste burning during the autumn harvest, especially in October. The contribution of coal combustion in cold seasons was substantially greater than in warm seasons, highlighting the role of increased coal burning for house heating in deteriorating air quality. Potential source function analysis showed that elements in Liaocheng originated from local and neighboring regions. The carcinogenic risk from the selected elements was notably stronger for adult males than for adult females and children, while the non-carcinogenic risk was stronger for children than for adults. Overall, these findings provide ponderable insights into the contamination characteristics and sources of elements, which are useful to inform effective measures for improving air quality and aerosol modeling. [ABSTRACT FROM AUTHOR]

Investigation of the critical metal elements in coal and coal-bearing strata has become one of the hottest research topics in coal geology and coal industry. Coal-hosted Ga-Al-Li-REE deposits have been discovered in the Jungar and Daqingshan Coalfields of Inner Mongolia, China. Gallium, Al, and Li in the Jungar coals have been successfully extracted and utilized. This paper reviews the discovery history of coal-hosted Ga-Al-Li-REE deposits, including contents, modes of occurrence, and enrichment origin of critical metals in each coal mine, including Heidaigou, Harewusu, and Guanbanwusu Mines in the Jungar Coalfield and the Adaohai Coal Mine in the Daqingshan Coalfield, as well as the recently reported Lao Sangou Mine. Gallium and Al in the coals investigated mainly occur in kaolinite, boehmite, diaspore, and gorceixite; REEs are mainly hosted by gorceixite and kaolinite; and Li is mainly hosted by cholorite. Gallium, Al, and REEs are mainly derived from the sediment-source region, i.e., weathered bauxite in the Benxi Formation. In addition, REE enrichment is also attributed to the intra-seam parting leaching by groundwater. Lithium enrichment in the coals is of hydrothermal fluid input. The content of Al2O3 and Ga in coal combustions (e.g., fly ash) is higher than 50% and ~100 µg/g, respectively; concentrations of Li in these coals also reach the cut-off grade for industrial recovery (for example, Li concentration in the Haerwusu coals is ~116 µg/g). Investigations of the content, distribution, and mineralization of critical elements in coal not only provide important references for the potential discovery of similar deposits but also offer significant coal geochemical and coal mineralogical evidence for revealing the geological genesis of coal seams, coal seam correlation, the formation and post-depositional modification of coal basins, regional geological evolution, and geological events. Meanwhile, such investigation also has an important practical significance for the economic circular development of the coal industry, environmental protection during coal utilization, and the security of critical metal resources. [ABSTRACT FROM AUTHOR]

Combustion is the most advanced and proven method on the market for using agricultural by-product residues and waste from the agri-food industry. Currently, a wide range of combustion technologies is used to produce heat and electricity in low-power heating devices (>50 kW) using various types of biofuels from biomass (woody biomass, herbaceous biomass, waste and residues from the agri-food industry). Combustion of biomass fuels, especially those of wood origin, causes lower carbon dioxide (CO2) and sulfur oxides (SOx) emissions into the atmosphere compared to coal combustion. The growing interest in solid biofuels has contributed to intensive activities on improving the combustion process and energy devices enabling effective and economic conversion of chemical energy contained in biomass into other usable forms such as heat, electricity. Having good quality fuel, it is necessary to ensure an appropriate, clean combustion technique, which allows to achieve the highest thermal efficiency of the heating device and at the same time the lowest emission of pollutants. The article presents issues related to the theory, characteristics of the combustion process and problems related to the formation of harmful chemical compounds nitrogen oxides (NOx), SOx, carbon monoxide (CO), particulate matter (PM) emitted to the atmosphere during the combustion process in low-power heating devices. The analysis indicates the possibility of minimizing undesirable phenomena during the combustion of these biofuels related to ash sintering, the formation of deposits, corrosion and improving the amount of condensable solid particles formed and therefore reducing the emission of gaseous products to the environment. [ABSTRACT FROM AUTHOR]

Global coal consumption is continuously increasing. It is still the primary fuel used in power plants. Despite policies in the European Union aimed at reducing coal consumption, there are countries in the world where coal use continues to rise (China and India are the largest consumers of coal). Coal combustion produces waste, 70% of which is fly ash. It consists mainly of SiO2 and Al2O3. Fly ash also includes Fe2O3, TiO2, MgO, K2O, and CaO. This article describes various methods of using fly ash. Fly ash can be used in the cement industry, as a filler in materials, in zeolite synthesis, in cenosphere separation, in agriculture, in water purification, in road construction as an asphalt filler, and in mine backfilling. An interesting method of using fly ash as a filler in the production of rigid polyurethane foam was also described. The article concerns potential uses in accordance with the principles of a Circular Economy. The environmental, energy, and material aspects are discussed. [ABSTRACT FROM AUTHOR]

To study the co-combustion characteristics of coal and Salix, thermogravimetric analysis is adopted to evaluate their co-combustion performance. The effect of blending ratios and synergistic are investigated in detail. Furthermore, kinetic analysis is performed. The results show that the incorporation of Salix into coal enhances combustion performance, with significant improvements observed at higher blending ratios. The ignition temperature decreases notably from 444 °C to 393 °C, highlighting an improvement in ignition properties. The primary weight loss peak shifts from 490 °C at a 15% biomass blend to approximately 320 °C at a 100% blend. Co-combustion demonstrates synergistic effects, with a 15% biomass blend optimizing combustion between 400 °C and 530 °C, while a 30% blend inhibits it. Additionally, temperatures above 600 °C exhibit an inhibitory effect. The activation energy is reduced to 25.38 kJ mol−1 at a 30% blend ratio and further to 23.06 kJ mol−1 at a 15% blend ratio at a heating rate of 30 K min−1. Increasing the biomass blend ratio and heating rate lowers the activation energy, which means facilitating the reaction process. [ABSTRACT FROM AUTHOR]

In this work, the coprecipitation approach was successfully used to create Mg-Al hydrotalcite-like inhibitors modified with varying amounts of Zn, and their characteristics were assessed. The findings indicate that the flame retardancy of Mg-Al hydrotalcite (MgAl-LDHs) is not significantly affected by Zn content. By adding MgAl-LDHs, the temperature at which the exothermic reaction started to occur was raised from 146.2 °C to 193.6 °C, according to the test of spontaneous combustion tendency. In the excavation route, the utility model can serve as a temporary fire prevention and extinguishment tool. Furthermore, the analysis of the functional group changes during the reaction was conducted using FTIR. After applying MgAl-LDHs, the oxidation of organic groups on the coal surface was clearly prevented, indicating that the inhibitor had a substantial flame-retardant effect on coal. In conclusion, this work creates a material that resembles hydrotalcite and is easy to use, inexpensive, and effective in preventing coal from spontaneously combusting. [ABSTRACT FROM AUTHOR]

Human activities such as mineral mining and coal combustion cause a large amount of antimony to enter into environmental soil. Exploring the adsorption deposition behavior of antimony on typical soil minerals is important for predicting the environmental fate of antimony and preventing its pollution. Thus, six kinds of commonly found metal hydroxides and clay minerals in soil (namely hematite, goethite, ferrihydrite, aluminum oxide, ramsdellite, and kaolinite) were selected to investigate the adsorption thermodynamic and kinetic behavior of Sb(III) and Sb(V) on their surfaces, and speculate the adsorption mechanism. The order of adsorption capacities (mg/g) of six soil minerals for Sb(III)/Sb(V) were as follows: ferrihydrite (101.4, 55.9)>ramsdellite (16.52, 7.58)>goethite (13.30, 5.67)>hematite (5.13, 3.70)>aluminum oxide (1.66, 1.69)>kaolinite (0.27, 0.51). Affected by the speciation of antimony and the surface potential of minerals, acidic conditions were favorable for the adsorption of Sb(V), while the adsorption of Sb(III) was less affected by pH. The Sb2O3 formed after deposition was characterized in situ by Raman spectroscopy. Sb(V) adsorbed on the mineral by adsorption at different concentrations, while Sb(III) deposits on the mineral surface at higher concentrations. [ABSTRACT FROM AUTHOR]

This study investigated the ash reduction and quality improvement effects of four types of ionic liquids on Zhundong high-alkali coal, focusing on the evolution laws of coal ash melting and combustion performance under the ionic liquid system, which provided a theoretical basis for the subsequent utilization of high-alkali coal. Ionic liquids can effectively reduce inorganic mineral content and volatile matter yield, increase fixed carbon and oxygen content in coal, and reduce hydrogen and sulfur content. The silicon-aluminum ratio of coal ash increased, and the content of low-melting minerals in coal ash decreased, while the content of refractory minerals increased, leading to an increase in the melting temperature of coal ash. Ionic liquids can inhibit the oxidation reaction of coal, which is beneficial for suppressing spontaneous combustion of coal and improving safety during storage and transportation. [ABSTRACT FROM AUTHOR]

Coal injection is an important way to reduce the coke ratio in the blast furnace. The combustion of pulverized coal in tuyere and raceway directly affects the production efficiency of smelting. Based on the design and production data of a 2000 m3 blast furnace, a three‐dimensional mathematical model of pulverized coal combustion in tuyere and raceway is established. The lower part of the blast furnace consisting of blowpipe‐coal lance‐tuyere‐raceway and coke bed is numerically simulated to study the influence of blast rate and oxygen on pulverized coal combustion under a certain coal injection ratio and a certain coal particle size distribution. The simulation results show that the pulverized coal burnout decreases from 69.2% to 67.4% when the blast velocity is increased by 20 m s−1, and the oxygen content increases from 23% to 27%, which can improve the pulverized coal burnout and increase the temperature in the raceway. A new direction is proposed to increase the pulverized coal burnout by optimizing the particle size selection and increasing the injection ratio of small particle size below 50 μm. The research provides theoretical and data support for increasing pulverized coal burnout. [ABSTRACT FROM AUTHOR]

This study examines the effect of sintering mean residence time (MRT) on the engineering properties and morphological structure of lightweight aggregates (LWA) manufactured from waste coal combustion ash (W‐CCA). A thermodynamics‐based framework was used to tune LWA manufacturing processes. A minimum 35% liquid phase (by mass) and a lower bound viscosity of 100 Pa·s of molten material were found necessary to successfully produce LWA. Using W‐CCA's chemical composition and FactSage thermodynamic modeling, the sintering temperature for LWA was set to 1075°C. Green spherical pellets made using a pelletizer were sintered at MRT of 5.1, 14.8, and 25.9 min to test LWA physical‐mechanical properties including, unit weight, specific gravity, water absorption, and compressive strength. Results indicated that unit weight ranged from 752 to 800 kg/m3, providing desirable lightweight properties. Oven dry specific gravity ranged from 1.24 to 1.43, complying with ENI13055 specification for LWA. Water absorption capacity decreased as MRT extended from 5.1 to 14.8 min and then increased as MRT proceeded from 14.8 to 25.9 min, achieving an average absorption capacity of 26% ± 1.5%. The inverse effect was noticed for compressive strength as LWA sintered with an MRT of 14.8 min demonstrated the highest compressive strength of 14.7 ± 1.8 MPa. The initial decrease in water absorption and increase in compressive strength are attributed to the efficient sintering of the LWA's internal structure. The inverse effect observed as MRT proceeded from 14.8 to 25.9 min was believed to be a result of thermal cracking due to extensive heat exposure. MRT of 14.8 min is recommended for LWA production using the coal ash utilized in this study for its buoyancy characteristics, sufficient absorption capability, and higher compressive strength. [ABSTRACT FROM AUTHOR]

The sedimentation process of coal slurry water is influenced by numerous factors and has complex mechanisms. Its nonlinear and large hysteresis characteristics pose great challenges to process optimization control, making it a current research hotspot. This paper takes the typical slime water treatment process of a coal preparation plant as the object, and, on the basis of selecting raw coal quantity, flocculation dosage, coagulation dosage, overflow turbidity, raw coal ash content, underflow concentration, and slime quantity as the key variables, establishes a quality control method for process detection data consisting of data acquisition → data anomaly detection → data filling and noise reduction; subsequently, different machine-learning algorithms are used to predict the performance of coal-slurry-settling agents. It was found that Long Short-Term Memory shows the highest prediction accuracy for coagulants, with corresponding root mean square errors of 2.72% and 6.23%. Finally, using iFix software (version 5.5), an intelligent control system for the settling process of coal slurry water was constructed, which reduced the usage of coagulants by 31.56% and 37.21%. [ABSTRACT FROM AUTHOR]

This study aims to investigate the characteristics of ash accumulation and slagging in boilers during low- and medium-load operation and to analyse the migration pattern of alkali metals in high-alkali coal. In this paper, the ash accumulation characteristics and slagging trend of the furnace interior under a 500 MW load were investigated using numerical simulation by comparing the ash accumulation and slagging characteristics under two different burner configurations, and analysing the slagging trend of the furnace with upper burner arrangement and lower burner arrangement by taking the deposition location on the furnace wall and the deposition rate and the temperature of the furnace wall as the indices. The existing formation of sodium in Jundong coal at different temperatures was investigated using computational methods; SiO2, Al2O3, and kaolin were doped separately; and the migration and transformation characteristics of their different additives on the sodium-based compounds in Jundong coal were explored. The results showed that, under a 500 MW load, the size of the tangent circle formed in the furnace by commissioning the upper burner condition was larger than the lower burner, and the main combustion zone was larger than the lower burner. The ash accumulation of coal ash particles in the boiler was mainly concentrated in the hearth region, and the deposition rate was higher at the height regions of 10 m and 25 m in the hearth. The solid-phase NaCl transition temperature was reduced to 350 °C after the doping of SiO2 in Jundong coal, and the doping of Al2O3 inhibited the transition of solid-phase NaCl, promoted the generation of gas-phase NaCl, and had certain inhibitory effects on the generation of sodium-based silica–aluminium compounds, the content of which at all temperatures was inversely proportional to the proportion of doping. The doping of kaolin promotes the transformation of solid-phase NaCl and inhibits the generation of gas-phase NaCl. [ABSTRACT FROM AUTHOR]

This work sought to conduct the chemical association of a toxic metal (cadmium) in coal samples of various origins in Pakistan. For that purpose, a sequential extraction scheme recommended by the Community Bureau of Reference (BCR) has been carried out to know the chemical fractionation of Cd in different coal samples. Simultaneously a time saving vortex-assisted single-step extraction (VA-SSE) via the same experimental parameters conditions used in each fraction steps of BCR sequential extraction procedure (BCR-SE). The coal samples were collected from Thar coal (TCF) and Lakhra coal fields (LCF) of Sindh, Pakistan. The validity of BCR-SE and VA-SSE were checked by applying spiking standard addition procedure on real coal samples. The BCR-SE and VA-SSE were completed in 51 h and 1.0–2.0 min, respectively. In second phase determined the combustion behaviour of Cd or/amount of Cd in coal samples volatilise after heating in an electric furnace in laboratory at three temperature interim (200°C, 400°C and 900°C). The coal ash obtained at 900°C was put to three step sequential extraction method. The evaluated result showed that the total values of Cd in coal samples of block II of Thar coal field (TCF), Site I and Site II of Lakhra coal field (LCF) were found in the range of 3.42–4.43, 2.02–2.82 and 2.91–3.92 mg/kg, correspondingly. The final result indicated that the major chemical fraction of Cd was bound with organic phase of coal samples of both origins (about 40%). The evaluated data showed that 60–71% of Cd in coal samples was found in first three fractions, whilst about 29–40% of Cd was observed in residual. The extracted Cd concentrations in various chemical fractions of coal samples obtained through VA-SSE were 1.6–2.6%, higher than those values gained via BCR-SE (p < 0.04). The resulted data indicated that, after burning of coal samples at 900°C, about 63–69% of total Cd in coal samples of both mining areas was found in residual ash, while 31–34% was vaporised/volatilised out into the atmosphere. [ABSTRACT FROM AUTHOR]

The increase of coal seam mining depth leads to the increase of ground temperature stress, which affects the fracture development and spontaneous combustion characteristics of coal samples. Taking anthracite as the research object, scanning electron microscopy, low-temperature N2 adsorption, temperature- programmed experiments and infrared spectroscopy tests were carried out to analyze the mechanism of the influence of pore structure and the number of oxygen-containing functional groups on the spontaneous combustion characteristics of coal samples from the physical and chemical perspectives. The results show that the connection between pores and fractures is enhanced and the scale of micro-fractures is also increased after the thermal and mechanical coupling. After treatment, the oxidation of the coal sample was enhanced, and the overall production rate of the three iconic gases increased. The thermal and mechanical coupling results in the increase of the content of aromatic hydrocarbon, oxygen-containing functional group and aliphatic hydrocarbon in coal. The thermal and mechanical coupling effects promote the occurrence and development of coal spontaneous combustion by changing the structure, temperature and stress state of coal and affecting the reaction process of coal and oxygen. The research results have laid a theoretical foundation for the prevention and control of multi-field coupling CSC. [ABSTRACT FROM AUTHOR]

In this study, the concentration of thirteen non-volatile elements in coal fly ash samples obtained from the Kangal coal-fired thermal power plant located in Sivas province of Turkey was determined using an energy dispersive X-ray fluorescence (EDXRF) spectrometer. Non-volatile elements in coal fly ash samples were analysed in three groups: major (Al, Si, and Ca), rare earth (Y, La, Ce, Pr, and Nd), and other trace elements (Ga, Rb, Mo, Ba, and Hf). The average concentrations of Ca, Si and Al were found as 22.8, 10.9 and 5.4%, respectively. The average concentrations of Pr, Y and, Nd were found as 23.9, 19.1 and 78.2, respectively. La and Ce were observed below the detection limit of 2 mg/kg, except for two samples. The average concentrations of Ga, Rb, Mo, Ba and Hf were found as 18.6, 51.1, 177.3, 993.5 and 3.9 mg/kg, respectively. According to the average values of enrichment factor estimated for elements analysed in fly ash samples, Mo is found extremely enriched while Ca and Hf are significantly enriched. [ABSTRACT FROM AUTHOR]

Although the global focus is shifting towards clean energy to replace coal, an immediate technological transition is not yet feasible due to the widespread prevalence of the existing coal combustion technology. The main objective of the present work is to investigate the characteristics of pulverized coal combustion by using Ansys Fluent. This study describes the fluid flow and combustion reactions in the 2D axisymmetric computational fluid dynamics (CFD) model for the 300 kW cylindrical swirl pulverized coal burner. The study was conducted to analyze the combustion process including the volatilization and char combustion models, while varying the ratio of air inlet velocity, and examining the effect of swirl number on pulverized coal combustion. The numerical modeling results for burner′s operating conditions are validated with the steady‐state temperature measurement in the burner. The significant outcome of the associated parameters found that the flame in the burner formed a spiral before converging into the flame line in the main combustion chamber. As a result, increasing the primary airflow rate led to a decrease in the axial temperature in the preliminary combustion chamber and decreasing the primary airflow showed the highest temperature in all three cases. While the secondary airflow increases, the swirling flow will be induced inside the chamber, which affects the highest temperature profile in the preliminary combustion chamber. Changing the tertiary airflow rate did not significantly affect the combustion. However, increasing the tertiary airflow rate improved the completeness of combustion. The swirl numbers also influenced the phenomena of combustion, the volatile released, and combustion reactions which could occur more rapidly with a higher swirl number due to a higher concentration of vortex region. Similarly, the highest swirl numbers resulted in the lowest excess O2 at the exit and the least amount of CO formation. [ABSTRACT FROM AUTHOR]

Insufficient handling of spontaneous combustion in coal piles arises from the influence of natural wind during the piling process, resulting in the displacement of the heat source. To investigate the impact of wind flow on heat source movement in simulated coal piles under varying wind velocities, an experimental stage was established. The research findings elucidate that both normal and tangential winds exert an influence on the heat source position, with normal winds exhibiting a greater effect than tangential winds. The relationship between heat source position speed and wind speed magnitude follows a common fitting function under both wind conditions. Specifically, the speed of the heat source at the edge position demonstrates a linear correlation with the magnitude of wind speed, while the speed of the heat source at the center position conforms to a quadratic function with the wind speed magnitude. The heat source moves at a distance of 0.8 cm to 5.3 cm on the Y = 0 tangent, corresponding to a moving speed of 0.03 cm/min to 0.18 cm/min. On theY = −20 tangent, the heat source moves at a distance of 2.1 cm to 8.1 cm, corresponding to a moving speed of 0.07 cm/min to 0.27 cm/min. Moreover, the study reveals that the influence on heat source movement at the center of the simulated coal pile diminishes as wind speed decreases under both wind conditions. These research findings provide a theoretical foundation for managing spontaneous combustion in coal piles and offer insights into precise management of heat source positions within coal piles. [ABSTRACT FROM AUTHOR]

In recent years, abnormal CO gas overruns have often occurred in coal mining workings. CO overruns were thought to be caused by the underground blasting work or spontaneous combustion of coal seams; however, minimal attention has been given to the causes of the desorption and release of adsorbed CO in the coal seams. Additionally, insufficient research has been conducted on the generation, distribution and adsorption and desorption characteristics of protogenetic CO in coal seams. Therefore, a self-built comprehensive testing system for coal seam adsorption and desorption was used to study the characteristics of the depressurization desorption and thermal desorption of coal with different degrees of metamorphism during coal seam mining. The results showed that under isothermal conditions, the amount of CO adsorption and desorption of coal samples increased with increasing pressure; under temperature rise conditions, the gas adsorption-desorption was in a dynamic equilibrium process under certain conditions. When the temperature increased, the equilibrium was beneficial to the desorption direction. The initial temperature range of CO production at different equilibrium pressures was 45–55°C. With increasing pressure, the initial temperature point of CO gas production moves forward and was significantly lower than the initial temperature of coal spontaneous combustion. Our research results further supplement the source of underground protogenetic CO gas and provide theoretical support for the accurate prediction of CO coal spontaneous combustion. [ABSTRACT FROM AUTHOR]

The shallow coal seam resources are gradually reduced, the depth of coal seam mining is increased, and the underground temperature is increased, which makes the risk of residual coal fire increase year by year. In order to explore the transformation path of functional groups during oxidation and the caloric release characteristics of residual coal in deep coal mine, the microcosmic changes of coal oxidation process in deep mine were analyzed by in situ diffuse reflectance (In situ FTIR) and electron spin resonance (EPR) experiments, and macroscopic characteristics such as characteristic temperature of residual coal were tested by synchronous thermal analysis experiment. In FTIR results, it is observed that hydroxyl groups, active aliphatic hydrocarbon structures, and active oxygen-containing groups are key chemical structures involved in the oxidation process of residual coal, displaying a strong correlation transformation phenomenon. This can be described as follows: oxygen absorption led to a negative correlation between aliphatic hydrocarbon structures and hydroxyl groups, while the conversion of aliphatic hydrocarbon structures into carboxyl and aldehyde groups resulted in a negative correlation between aliphatic hydrocarbons, carboxyl groups, and aldehyde groups. Active oxygen-containing functional groups showed a positive correlation. With the increased of free radical concentration, the type of free radicals increased and the linewidth (ΔH) increased. The high-temperature environment intensified thermal behavior tendencies, increased the number of active structures, and raised the risk of spontaneous combustion. The research results provided a theoretical basis for understanding the process of coal spontaneous combustion, and had important reference value for ensuring the safe mining of deep coal seams and implementing effective disaster prevention measures. [ABSTRACT FROM AUTHOR]

Given the shortcomings of existing fire-extinguishing materials, a new type of fire-retarding foam material with composite foaming agents and antioxidants as raw materials was developed. The formula of the composite foaming agent was determined by screening and compounding surfactants. Then, the inhibition characteristics of different antioxidants were tested using a cone calorimeter to determine the best antioxidant. Next, the inhibition characteristics and fire-extinguishing and cooling characteristics of fire-retarding foam were measured by a temperature programmed apparatus and a fire-extinguishing test bench. Results show that the prepared fire-retarding foam achieves the best performance when the mass ratio of the surfactants CAB-35 and MES is 2:3, the mass concentration is 0.4%, and the mass concentration of the tea polyphenols is 1%. In the aspect of low-temperature inhibition, the cross-point temperature of the fire-retarding foam increases from 119.4°C of raw coal to 142.7°C, which is 15.4°C and 6.5°C higher than that of ordinary foam and MgCl2 solution, respectively. At 180°C, the CO concentration is only 1613 ppm, which is about 67.3% of that of raw coal, 78.3% of that of coal treated with ordinary foam, and 85.8% of that of coal treated with MgCl2 solution. The fire-extinguishing times of common foam, MgCl2 solution, and fire-retarding foam are 1780 s, 1350 s, and 820 s, respectively, indicating that fire-retarding foam has the highest fire-extinguishing efficiency. [ABSTRACT FROM AUTHOR]

Conveyor belt fires are the most serious fires that occur exogenous mine fires. To study the thermal characteristics of the PVC conveyor belt during the fire process, the softening characteristics of the conveyor belt underground in the mine were simulated by using the temperature rise oxidation system. Based on the C600 microcalorimeter, the oxidation heat release law of the PVC conveyor belt and pulverized coal with different softening temperatures was studied at an environmental range of 40–500°C, and the combustion law, heat release and heat absorption, HRR,combustion stages and activation energy were analyzed. The results show that with increasing softening temperature, the law of heat absorption and heat release of the PVC conveyor belt in the initial stage of the independent reaction is opposite, while the heat absorption and heat release in the coupling with pulverized coal increase gradually, and 106% and 107% more heat is released in the rapid development state than in the independent reaction state. The change rule of the heat release acceleration of the PVC conveyor belt remains basically the same whether it is alone or coupled with pulverized coal. The maximum difference in heat release acceleration increases with increasing softening temperature. According to the division of the combustion stages of the conveyor belt according to the heat flow value, when the PVC conveyor belt reacts alone, the temperature range of the heated softening zone is approximately 140°C smaller than when it is coupled with pulverized coal, and the temperature range of the melting pyrolysis zone is expanded by 100°C.It shows that when the conveyor belt is coupled with pulverized coal, fire is more likely to occur and the fire risk is greater. The average HRR at the softening temperature of 100°C is the largest, the ignition time is the shortest, and the danger is the greatest. The activation energy decreases with increasing softening temperature when it is coupled with pulverized coal, indicating that the higher the softening temperature is, the more likely an oxidation reaction will occur. The heat release characteristics and combustion stages division of the conveyor belt proposed in this paper have certain guiding significance for the replacement and maintenance of mine conveyor belts and the prevention and control of mine fires. [ABSTRACT FROM AUTHOR]

To address the environmentally friendly issue of fire prevention and extinguishing materials in coal mines, a new biomass gel material was prepared using sodium carboxymethyl cellulose (CMC) as the matrix, ferro aluminum citrate (Fe-AlCit) as the cross-linking agent, and gluconic acid-δ-lactone (GDL) as the pH modifier. Through performance tests of gel micromorphology, thermal stability, viscoelasticity and yield stress, it was found that the CMC-3 gel material with a ratio of 2.5% CMC + 4% Fe-AlCit +2% GDL had a dense surface structure, good thermal stability and moderate viscosity, which was the most suitable for pipeline transport. A metal coordination bond favorable to the stability of CMC-3 gel is formed by the carboxylate ion in CMC and the double high-valent metal ions Fe3+ and Al3+ dissociated by Fe-AlCit. CMC-3 gel exhibits excellent fire prevention and extinguishing properties. The results of the programmed warming experiments showed that the inhibition rate of the coal sample treated with CMC-3 gel against CO and C2H4 gases reached 44.84% and 46.57% at 220°C, respectively, and the growth rate of the activation energy in the first and second stage reached 17.63% and 22.68%, respectively, which plays a significant inhibitory role. The infrared spectroscopy test showed that after adding CMC-3 gel, the content of -OH and Ar-C-O in the coal samples was reduced by 49.58% and 40.82%, respectively, and the content of stable C=C in the aromatics was increased by 6.14%, which effectively blocked the coal-oxygen chain reaction and reduced the tendency of coal spontaneous combustion. The thermogravimetric test showed that the characteristic temperature points of the coal sample treated with CMC-3 gel were all increased to different degrees. The fire extinguishing test showed that CMC-3 gel could significantly reduce the temperature of coal sample and extinguish the coal fire quickly. Moreover, the CMC-3 gel material also has excellent self-healing properties, which can self-repair the damaged network through the abundant reversible hydrogen and ionic bonds inside the gel in only 90 s. The study has certain guiding significance for the development of efficient and environmentally friendly self-healing mining fire prevention and extinguishing materials. [ABSTRACT FROM AUTHOR]

In this study, sequential feeding method was conducted due to some coal-fired power plants not being equipped by coal blending facility. Its effect on ash-related problem was investigated using drop tube furnace combustion test and ash particle observation method. AUS coal (low-slagging risk sample) and KT coal (high-slagging risk sample) were used to obtain AK-1 coal and AK-2 coal. AK-1 coal was a coal sample of out-furnace blending method, while AK-2 coal was coal sample of sequential feeding method. AK-1 probe tended to be more similar to AUS coal with only a small spot of ash attached on the probe surface. Meanwhile, AK-2 probe had more ash attached on the probe surface, indicating more severe slagging than AK-1 probe. According to ash morphology, the result indicated that the upper layer of slag tended to be more similar to AUS coal ash, while initial layer of slag of AK-2 coal contained more KT coal ash. Based on ash mineralogy, sodium in AK-2 coal was distributed evenly which was different with AK-1 coal. This result shows that sequential feeding method is not applicable to reduce slagging and fouling risk of KT coal. [ABSTRACT FROM AUTHOR]

The regulation of oxygen concentration in underground coal mines is an efficient method to prevent coal spontaneous combustion. The screening and development of efficient oxygen-consuming microbial flora is a fundamental prerequisite for the application of biotechnology in preventing coal spontaneous combustion. For the initial screening, activated sludge obtained from Qinglong Coal Mine in China was utilized as an inoculum source to cultivate a group of Aerobic microbiota (AMS) with a relatively stable community structure. Afterward, the community structure of AMS was analyzed using 16SrRNA gene sequencing technology. Subsequently, single-factor experiments were conducted to optimize culture conditions (carbon source concentration, pH, inoculum amount) based on the growth characteristics of dominant strains. Finally, the oxygen consumption characteristics of AMS were investigated using a range of indicators, including oxygen consumption rate, CO2 generation and growth concentration (OD) as measured by AMS. The results indicated that the growth activity of AMS was most robust when the carbon source concentration was 1%, pH was 7, and the inoculation amount was 10%, with an oxygen consumption rate of 94.83%. The experiment observed a significant increase in the concentration of CO2, which rose from 0.096% to 30.272%. This gas is the primary product of AMS. Interestingly, growth was possible in environments with O2 concentrations ranging from 5% to 29%, indicating that AMS is adaptable and can survive in environments with significant changes in O2 concentrations. In addition, the combined effect of reducing O2 concentration and inerting the mining zone made AMS more effective in suppressing spontaneous combustion of relict coal. [ABSTRACT FROM AUTHOR]

To overcome the problem of poor biocompatibility of inorganic gel foam, a biomass gel foam was prepared using carboxymethyl chitosan, tannic acid, and ammonium ferric citrate as raw materials. The results indicated that the gel foam exhibited optimal comprehensive performance when the mass concentrations of foaming agent, stabilizer, gelling agent, and crosslinking agent were 0.8, 0.2, 0.9, and 0.6 wt%, respectively. At this point, the foaming multiple was up to 8 and the half-life was 7.79 days. Compared to pure foam, the gel foam demonstrated excellent water retention and film-forming properties. After continuous heating at 80°C for 10 hours, its water retention rate remained as high as 49.34%. The foam film formed after 120 hours of room temperature drying reached a thickness of 1 cm without any liquid separation phenomenon. The gel foam exhibited a good inhibition effect on the spontaneous combustion and oxidation process of coal. The CO inhibition rate reached 67.43% at 100°C, and the cross-point temperature was effectively delayed by 18.2°C. Moreover, the gel foam exhibited excellent burn resistance properties. [ABSTRACT FROM AUTHOR]

An efficient, environmentally friendly, and economical polyphosphate/nitrogen-containing composite inhibitor (APNI) has been developed to prevent coal spontaneous combustion (CSC) disasters. Using temperature rise experiments during coal spontaneous combustion, mercury pressure experiments, and Fourier transform infrared spectroscopy (FTIR), the samples treated with the APNI were compared with those treated with MgCl2 and NH4H2PO4 inhibitors, and the inhibitory effects of the three inhibitors on CSC were studied. The results showed that the APNI effectively limited the reactions between the coal and oxygen, reduced the amount of CO gas generated, sealed most of the cracks, large pores and mesopores in the coal, and reduced the number of active functional groups in the coal. The APNI was more effective in preventing CSC than MgCl2 and NH4H2PO4. [ABSTRACT FROM AUTHOR]