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Coal fly ash (CF) is used in coal pyrolysis or gasification as a result of the high content of oxide metals. However, CaSO 4 and SiO 2 in CF inhibited catalytic activity. Herein, the application of acid-base modified CF to steam gasification of coal (CA). It was found that the order of acid-alkali modification had different effects on the H 2 production. NaOH–HF (A-E) modified CF, there was no CaSO 4 present on the surface of CF, and the surface SiO 2 shell structure was destroyed, releasing more α-Fe and α-Fe 2 O 3. A new Fe active phase (Fe x F y) had been formed. Meanwhile, the functional groups on the surface of modified CF changed, resulting in more C–H bonds, which provided more H sources for gasification. The α-Fe and α-Fe 2 O 3 in NaOH–HF modified CF were in full contact with coal and steam, breaking the O–H bonds in the H 2 O, the aliphatic side-chain hydrocarbons and C–H bonds in the coal to produce more H 2. α-Fe 2 O 3 and α-Fe undergoes mutual transformation at the action of H 2 , providing more Fe to increasing H 2 production. When the gasification temperature was 900 °C, the steam flow rate was 1 mL/min and the heating rate was 10 °C/min, the H 2 yield increased from 915.97 mL/g -(E-A) to 1539.72 mL/g -(A-E) , the carbon conversion of coal gasification was 99.68%. [Display omitted] • Release of catalytic activity of fly ash itself using NaOH–HF modification method. • The NaOH–HF modification method was used to reduce the content of CaSO 4 in CF. • The NaOH–HF modification method was used to change the original structure of the CF. • α-Fe and α-Fe 2 O 3 promotes the fracture of O–H bonds in H 2 O and C–H bonds in coal. • The modified fly ash enhances the generation of H 2 in coal under steam. [ABSTRACT FROM AUTHOR]

A wide range of wastes can potentially be used to generate thermal and electrical energy. The co-combustion of several types of waste as part of water-containing waste-derived fuels is a promising method for their recovery. In this research, we use thermogravimetric analysis and differential scanning calorimetry to study the thermal behavior and kinetics of coal slime, biomass, waste oils, and blends on their basis. We also analyze the concentrations of gaseous emissions. The results show that biomass, oils, and coal slime significantly affect each other in the course of their co-combustion when added to slurry fuels. The preparation of coal-water slurry based on slime and water reduced the ignition and burnout temperature by up to 16%. Adding biomass and waste oils additionally stimulated the slurry ignition and burnout, which occurred at lower temperatures. Relative to dry coal slime, threshold ignition temperatures and burnout temperatures decreased by 6%–9% and 17%–25%, respectively. Also, the use of biomass and waste oils as part of slurries inhibited NO х and SO 2 emission by 2.75 times. According to the kinetic analysis, added biomass and waste turbine oil provide a 28%–51% reduction in the activation energy as compared to a coal-water slurry without additives. [Display omitted] [ABSTRACT FROM AUTHOR]

Thermal power plants are pivotal in meeting global energy demands, yet enhancing their efficiency and sustainability remains an enduring challenge. While previous studies have scrutinized energy and exergy analyses of distinct plant components, there's a scarcity of comprehensive reviews integrating findings across diverse plant types. This paper bridges this gap by presenting a comprehensive synthesis of recent advancements in energy and exergy studies across coal, gas, biomass, oil, and combined cycle plants. The review focuses on critical aspects: optimizing operations through modeling and advanced controls, economic evaluations encompassing costs and revenue, and assessing environmental impacts such as emissions and water use. Achieving a balance between performance, cost-effectiveness, and environmental responsibility is crucial for sustainable thermal power generation worldwide. It requires an integrated approach that considers technical, economic, and environmental factors to ensure efficiency, profitability, and minimal adverse effects on health and climate. Key findings emphasize that, in most cases, the boiler emerges as the primary source of exergy destruction, accounting for over 50% of losses across varied plant configurations. Turbines and condensers also significantly contribute to energy losses. Supercritical and ultra-supercritical power plants exhibit higher efficiencies compared to subcritical counterparts. Integrating waste-to-energy technologies with coal plants holds promise, offering efficiency improvements and reduced environmental impact. Optimizing parameters such as pressure and temperature, along with component advancements, shows potential in curbing losses. These optimization endeavors have showcased a notable up to 6% enhancement in exergy efficiency. This review underscores the critical role of ongoing thermodynamic modeling and assessments in steering towards more sustainable thermal power generation. In summary, this paper delivers valuable insights into performance benchmarks and delineates effective strategies for augmenting thermal power plant efficiency through exhaustive energy and exergy analyses. [Display omitted] • Exergy analysis provides a broader perspective than energy analysis alone. • Boiler subsystem is a major source of exergy destruction (52-85% of total losses). • Supercritical and ultra-supercritical plants display higher efficiencies than subcritical ones. • Optimization of parameters like temperature and pressure can boost exergy efficiency by up to 6%. • Advanced combined cycles achieved over 50% efficiency, indicating potential for lower CO2/kWh. [ABSTRACT FROM AUTHOR]

Improving the quality of syngas from fine coal waste using the sorption-enhanced gasification process is a novel technology in the production of H 2. The effect of CaO on CO 2 absorption and H 2 increase in the steam fine coal gasification process was determined in a fixed bed gasifier. The steam gasification process took place at 650 °C using bentonite and CaO as catalysts and absorbents. Steam increased the H 2 concentration in the syngas to 58 vol%. In-situ CO 2 absorption is more effective with the addition of CaO. The maximum percentage of CO 2 was absorbed when the Ca/C ratio 2 was 78.33 %. The H 2 content in the syngas after the CO 2 was absorbed increased rapidly to 75.80 vol% at a Ca-to-carbon-mole ratio (Ca/C) of 1.5 and a steam-to-feedstock ratio (S/F) of 1.5. CaO did not produce significant results for low heating value (LHV) or cold gas efficiency (CGE), with results of 12 MJ/Nm3 and 44.53 %. The dominant water gas shift reaction due to the influence of steam and CaO increased H 2 /CO up to 9.11, which made the syngas from this work suitable for Fischer–Tropsch synthesis. [ABSTRACT FROM AUTHOR]

To reach the worldwide decarbonisation and the corresponding climate change mitigation, low-carbon energy sources must be used in the near-term and the role of the nuclear energy in pathways to produce net zero emissions is outstanding. This is not only because nuclear energy produces carbon-free energy, but also because it can supply high-temperature process heat to industrial applications such as the hydrogen production. Hydrogen is presently considered as the energy vector of the future to attain these environmental goals. In this paper, the possible use of a nuclear-assisted steam coal gasification process for hydrogen production is investigated in deep. As a modern High Temperature Gas Cooled Reactor (HTGR) is able to produce a gas outlet temperature of 950 °C, the nuclear heat can be transferred to a steam coal gasification plant via an intermediate helium circuit for providing the high-temperature process heat required by the endothermic gasification reactions between the steam and the carbonaceous matter. The nuclear-assisted gasification technology is considered to be attractive for the processing of an Argentine orthoasphaltite that is extracted from a minefield located in Neuquén province. The present research comprises both theoretical and experimental studies, which were addressed to get the necessary information about the optimal conditions for the hydrogen production though the steam gasification process using the Argentine orthoasphaltite as feedstock. A conceptual design of an energy complex for nuclear hydrogen, electricity and liquid fuels production is also proposed. In this conceptual design, the steam coal gasification reactor consists of two concentric vessels specially designed to separate the pyrolysis step occurring at low temperature and the char gasification step that takes place at higher temperatures. In this way, it is possible to give a full use to the volatile compounds that are present in the feedstock and are identified and characterized in this work. [Display omitted] • Thermodynamically-favourable conditions for H 2 production though steam gasification of carbonaceous matter were determined. • The use of a HTGR for providing the nuclear process heat for indirect heating of the gasification reactor was considered. • A technical feasibility analysis for processing an Argentine orthoasfaltite for nuclear hydrogen production was presented. • Operating conditions in the steam gasification process for producing a hydrogen-rich synthesis gas were optimized. • A dual-concept for the gasification reactor by separating pyrolysis and gasification steps was proposed. [ABSTRACT FROM AUTHOR]

The new process 'coal gangue/fly ash – HNO 3 pressure leaching (NAPL) –low-temperature pyrolysis' was proposed by our team, which aimed to achieve the transformation of coal-based solid wastes from harmless to Al resource. For cost control, the regeneration of HNO 3 at a low cost was crucial for the process. Following NAPL of coal gangue and fly ash, massive amounts of Al(NO 3) 3 ·9 H 2 O were collected, with a decomposition temperature as low as 523 K. The energy consumption for low-temperature pyrolysis could be supplied by the combustion of residual carbon (6.96 wt%) during the thermal activity of coal gangue, allowing HNO 3 to be regenerated and recycled without extra heat supply. However, little research has been done on the pyrolysis behavior and kinetics of Al(NO 3) 3 ·9 H 2 O, which was examined in this study. The pyrolysis characteristics of Al(NO 3) 3 ·9 H 2 O were assessed by TG-DSC analysis. Further experiments and XRD/FTIR/MS analysis revealed that phase evolution of Al(NO 3) 3 ·9 H 2 O followed the sequence of Al(NO 3) 3 ·9 H 2 O→ Al(NO 3) 3 ·nH 2 O→ Al(NO 3) 3 ·3Al(OH) 3 ·5/2 H 2 O→ AlOOH→ Al 2 O 3. Subsequently, the thermodynamic (∆ G , ∆ H , ∆ S) and kinetic (E a , A) parameters were calculated based on the thermogravimetric data by the iso-conversional methods. And the mechanism models and functions were identified via the Malek method. Finally, the economic evaluation of pyrolysis indicated that 5.04 × 10–3 Nm3 of natural gas was consumed during pyrolysis of one mole Al(NO 3) 3 ·9 H 2 O, equivalent to 44.33 $ per ton of Al 2 O 3. As a basic research of Al(NO 3) 3 ·9 H 2 O pyrolysis, this paper enhances related theories of the NAPL process. [Display omitted] [ABSTRACT FROM AUTHOR]

One of the global state tasks, contributing to the implementation of the goal of developing the energy sector of the Russian Federation and given in the Energy Strategy of the Russian Federation for the period until 2035, is to reduce the negative impact of the fuel and energy complex industries on the environment. In this regard, special attention is paid to the coal ash handling problem, which is intensified by tightening of the environmental legislation with the transition to the principles of the best available technologies, greening of the coal power, depletion of the capacity of the coal ash disposal sites, etc. Disposal of ash, slag, ash-and-slag mixtures, formed at combustion of coal, peat and shale, is one of the main problems of the modern solid-fuel thermal power plants in Russia, the number of which makes 172. The average age of the coal-fired TPPs is about 50 years that significantly affects the technical and environmental performance of the ash removal system of TPPs. At the Russian TPPs for the ash and slag conveying hydraulic ash removal systems are the most common, used in the vast majority of cases being technically outdated, uneconomical and ecologically not friendly. Annually 25 ... 30 million tons of ash and slag are formed at the coal-fired power plants of the Russian Federation. Currently more than 1.5 billion tons of ash and slag are accumulated at the ash disposal sites of thermal power plants, and every year these figures are growing. About 2/3 of all ash and slag disposals are close to the design filling or are already overfilled. Elimination of objects of the accumulated environmental damage, representing ash disposals of the coal-fired power plants, is one of the conditions for Russia's transition to the standards of "green" economy. The problem of coal-fired power plants in terms of elimination of the accumulated environmental damage can be solved only by implementing the large-scale projects of integrated coal ash processing, obtaining required products. The article provides statistical data for the 2019 relating to the volumes of the coal ash generation and utilization in various countries of the world. An overview of the various applications of the coal combustion by-products, the main of which are ash and slag, in Russia, India, China, EU countries, etc. is presented. The article contains data on the applicability of the coal ash for various technologies of its use according to the Russian Ministry of Energy. A review of scientific and technical information sources on the prospects of using coal ash in hydrogen power engineering for hydrogen sorption and storage is given, as well as a review of traditional methods of hydrogen storage. Terminology in the field of coal ash handling found in scientific and technical information sources is considered, and a classification of coal combustion by-products in Russia and abroad is given. The main recommendations of the author, contributing to the increase in the use of coal ash in Russia, are given. [ABSTRACT FROM AUTHOR]

Spent cathode carbon block (SCCB) is a hazardous waste produced by the electrolytic aluminum industry. Collaborative treatment of the SCCB in pulverized coal boilers is a potentially valuable technology. Pilot experiments were carried out on a 240 t/h pulverized coal boiler and its supporting flue gas treatment measures as a function of the mixing ratio of SCCB to verify the feasibility of coal collaborative disposal of SCCB. The thermal conversion characteristics of fluoride after mixing SCCB with coal were studied. A continuous emission monitoring system was used to monitor the impact on SO 2 , NO x and particulate matter in real time. The effectiveness of existing flue gas control measures was evaluated, and optimization suggestions of the flue gas control measures were postulated. The content of heavy metals (Hg, Cd, Ni, Pb, As, Se) in solid waste from co-combustion and the physical phase of solid waste were investigated. In addition, the transformation of heavy metals such as Hg, Cd, Ni, Pb, Cr, As and fluoride in defluorination wastewater during flue gas treatment were analyzed. The results show that it is feasible to use a pulverized coal boiler to dispose SCCB. The existing flue gas treatment measures proved to be appropriate, and desulfurization wastewater can achieve the discharge standards. Defluorination gypsum, fly ash and slag are not hazardous waste. When the mixing ratio of SCCB is increased, the existing neutralization and flocculation precipitation processes of the desulfurization wastewater are affected. It is suggested to add Al 2 O 3 for the defluorination process before the desulfurization tower. [Display omitted] [ABSTRACT FROM AUTHOR]

Molten carbonate direct carbon fuel cells (MC-DCFCs) allow the efficient and clean use of coal. In this study, a novel anode structure is designed, and the performances of six coal-based fuels are investigated in MC-DCFC. The mechanisms of performance differences are investigated, as well as the effect of operating temperature on performance. The results reveal the fuel cell performance in the following order: meagre coal (109.8) ≈ bituminous coal (108.7) > bituminous coal char (98.1) > lignite coal (83.7) > lignite coal char (71.3) > meagre coal char (53.2) in mW cm−2. Coal performs better because of its high carbon content, high volatile content, rich oxygen-containing functional groups, larger specific surface area, stronger thermal reactivity, and other factors. The electrochemical reactivity of coal fuel increased with higher reaction temperatures and varied throughout the temperature ranges. This study implies that using coal fuel to commercialize MC-DCFC could be a realistic alternative. [Display omitted] • Performance of six coal fuels are investigated in an MC-DCFC with a new anode. • Maximum peak power density of 109.8 mW cm−2 is obtained with a meagre coal. • Mechanism of their performance differences is analyzed. • Their performance stability are discussed. • Effect of operating temperature on the performance is explored. [ABSTRACT FROM AUTHOR]

The critical metal germanium (Ge) is recovered as a by-product of mining other commodities, such as zinc and thermal coal. We investigated the Ge incorporation mechanism in sphalerite synthesized under hydrothermal conditions like those of sediment-hosted Zn-Pb deposits. Sphalerite ± galena ± barite formed via reactions of Ge ± Fe ± Cu ± Ba-bearing brine with calcite and reduced sulfur at 200 °C and water vapor-saturated pressure. The products were examined using backscattered electron (BSE) imaging, electron probe microanalysis (EPMA), electron backscattered diffraction (EBSD), synchrotron X-ray fluorescence (SXRF) and micro-X-ray absorption near-edge structure (μ-XANES). We show that Ge(IV) is incorporated into sphalerite and bonded with reduced sulfur, both in the experimental sphalerite and in natural zinc ore samples from the MacArthur River Zn-Pb-Ag deposits, Australia. Copper K-edge XANES spectra show that copper occurs as Cu(I) in the experimental sphalerite, consistent with previous studies on Cu in natural sphalerite. The experiments reveal that Ge(IV) substitution in sphalerite occurs with and without the presence of other metal ions (e.g., Cu(I)), indicating that Ge(IV) substitution can be accommodated via charge balance by vacancies as well as by coupled substitution in the synthesized sphalerite. Ab initio quantum chemical simulations confirm that sphalerite can readily accommodate Ge, with the crystal structure and average Zn-S, Zn-Zn, S-S distances retained when replacing > 3 mol% of the Zn sites with Ge(IV), Ge(II), Cu(I) or Fe(II), demonstrating the resilience and flexibility of the sphalerite crystal structure. These Ge incorporation mechanisms explain the previous observations of multiple ways of Ge incorporation in natural sphalerite. The study provides experimental and molecular simulation insights for understanding the processes related to the formation and extraction of Ge in zinc ores. [ABSTRACT FROM AUTHOR]

The biggest challenge facing the energy sector today is how to achieve a faster transition from fossil fuel economy to sustainable energy sources. Hydrogen is a clean chemical element that can be associated to high-efficiency fuel cells. However, most industrial H2 production processes are obtained from thermochemical processes that generate large amounts of CO2, such as natural gas (NG) steam reforming and coal gasification. An option to CO2-free H2 production is by water electrolysis based on renewable electricity, however it has technical-economic limitations that make its wide use difficult. This article presents a new plasma reformer as an alternative for H2 production that uses NG with CO2 or biogas as feedstock. Conversions of 90% of NG were experimentally obtained, producing H2, CO and reduced graphene oxide in a single pass through the reactor, without catalysts or heat regeneration. The Energy Conversion Efficiency of the prototype presented values close to 50%, without regard the energy of the carbonaceous nanomaterials obtained and depending on the losses between the power supply and the plasma torch. The proposed technology contributes to the transition from fossil fuel to renewable sources, suggesting the production of H2 in a decentralized way for fuel cell electric vehicles. • Experimental results of a catalyst-free plasma dry reforming with 90% NG conversion. • New plasma technology to produce syngas and reduced graphene oxide at large scale. • H2 and graphene-based materials production by CO2 thermal plasma reactor. • Use of CO2 as plasma gas to assist H2 as vehicular fuel from NG and CO2 or biogas. • Prototype results with nearly 48% of Energy Conversion Efficiency in syngas production. [ABSTRACT FROM AUTHOR]

Catalyst characteristics such as specific surface area, porosity and active site play an essential role in catalyst design. Understanding of the characteristic functions in controlling catalyst activity is necessary for considering the catalyst application, especially the Ni-loaded lignite char catalyst, employed in catalytic steam gasification. In this work, the unmodified and five modified catalysts were used to study the effect of catalyst characteristics on their performance for catalytic steam gasification of coal in the two-stage fixed-bed reactor. The findings indicated that the fresh acid modified catalysts increased specific surface area and micropore formation, including the smaller Ni metal crystallite size, the decreasing of Ni metal nanoparticle size and the well-dispersed of Ni metal nanoparticles. Meanwhile, the fresh modified catalysts by the alkali and the combined alkali-acid treatments promoted mesopore formation. Enhancing catalytic steam gasification of coal, it was found that the mesoporosity of catalyst was the considerable initial characteristic for controlling the catalyst activity. The total gas yields of the mesoporous catalysts were in the range of 50.65–77.70 mmol/g VM,feed , while the total gas yields of the microporous catalysts were 43.82–55.34 mmol/g VM,feed. After catalyst testings, the specific surface areas and number of mesopores in the spent catalysts were increased by steam. Remarkably, these changing pore sizes affected the transformations of the isotherms (type I + II to type II) and the hysteresis loops (type H4 to type H3). Also, steam influenced the conversion of Ni metals to NiO, Ni(OH) 2 and Ni 2 O 3. For thermal property, all spent catalysts had high thermal stability. The modified catalysts could decrease carbon deposition more than the unmodified catalyst, which was an upside for catalyst reusability. [Display omitted] • Catalyst modifications affected their characteristics, especially pore size. • Mesoporosity of catalysts was the key factor in controlling catalyst activities. • Catalytic steam gasification affected isotherms and hysteresis loops of catalysts. • Modified catalysts could prevent carbon deposition in the coal gasification process. [ABSTRACT FROM AUTHOR]

Experimental results of the influence of thermal preparation of coal-water slurries on their rheological properties and spraying characteristics are presented. The slurry density was found to increase by 14% at a temperature of 293 K with the substitution of water in coal-water fuel with a similar by weight amount of pyrogenetic water (no more than 25%). Preliminary thermal preparation of coal-water slurries up to 333 K reduces its density by 7%. The experimental results showed that the greatest influence of thermal preparation of the studied slurries on their dynamic viscosity is characteristic of the temperature range from 293 to 323 K. At such temperature values, a decrease in the slurry viscosity is by 17–20% in comparison with two-component coal-water fuel. Preheating of slurries before spraying, in the temperature range from 293 to 333 K, makes it possible to increase the jet spraying angle by 21–29% compared to conventional two-component coal-water fuel at a temperature of 293 K. The velocity of droplets of the investigated coal-water fuels in the range of changes in their initial temperature from 293 to 333 K varies slightly. The difference is no more than 5%. Increase in the pyrogenetic water concentration in coal-water fuel of more than 25% by weight is impractical for lignite due to the dramatic increase in its viscosity. In the studied range of the third component concentration of the slurry, increase in the average size of fuel droplets is about 8%. Preheating of CWF before spraying can significantly reduce the average size of the droplets. The changes are 5–9% in comparison with coal-water slurry at a temperature of 293 K. Thermal preparation of slurries, according to the results of thermal imaging studies of coal-water fuel jet, affects the thermal contour of the jet and the geometry of its temperature zones. [Display omitted] • slurry viscosity was found to increase with PW addition (no more than 25%). • heating such CWS to 323 K reduces the viscosity by 17–20%. • increase in PW concentration more than 25% is impractical for such coal grade. • CWF preheating before spraying can significantly reduce the average size droplets. [ABSTRACT FROM AUTHOR]

• A dual-cylinder open calorimeter of online coal calorific value measurement. • New structural design of combustion chamber and calorimetric model. • Reduced measurement time and increased stability. • Analysis of influencing factors and performance of this method. • Prerequisites for the development of an online instrument for measuring the calorific value of coal. This paper introduces a dual-cylinder open calorimeter in which the dual-cylinder structure functions as the combustion chamber shell to preheat the oxygen and isolate the external environment. Designed for swift online measurement, it utilizes a stepper actuator to introduce the coal sample into the calorimeter from the bottom, achieving efficient combustion at atmospheric pressure. According to the heat transfer process of the calorimeter, we developed a calorimetric model and identified the moment when the first derivative of the fin temperature reaches its minimum as the measurement endpoint. The calorimetric model was calibrated with the Chinese national standard calorific value coal. Subsequently, we conducted experiments to analyze the effects of oxygen supply flow rate on CO 2 and CO generation curves in the flue gas, unburned rate of coal, and measurement time. The results indicated a significant reduction in CO generation, achieving a burnout rate of 96 % for the thermal coal species, and effectively shortening the measurement duration at the oxygen supply flow rate of 7.50 L/min. Finally, the verification analysis of 8 thermal coal species with the mass of about 1 g demonstrates that the calorimeter achieves the measurement time within 15 min and error within 5 %. The proposed calorimeter shows promising potential for practical applications in online measurement of the coal calorific value. [ABSTRACT FROM AUTHOR]

Asphalt mastic, an important raw material in asphalt pavement, is a mixture of asphalt binder and mineral filler. This study utilized coal gangue (CG) as alternative of natural filler in asphalt mastic, which has benefits to recycling solid waste and saving non-renewable resource. In order to achieve performance improvement of CG asphalt mastic (CGAM), thermal activation approach was applied to treat CG particles from 450 ℃ to 900 ℃. Before and after treatment, the surface morphology, mineral components and size distribution were characterized via scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF) and laser particle size analyzer. Meanwhile, the dynamic shear rheometer (DSR) and bending beam rheometer (BBR) experiments were conducted to compare the rheological responses of CGAM at high and low temperatures. Further, the interfacial behavior between asphalt binder and CG filler is simulated by molecular dynamic (MD) method, aiming to explore the interaction mechanism at atomistic scale. Results show that the activated CG possesses a smaller particle size and a rougher surface by comparison in virgin one (i.e., unactivated CG). And the calcination process results in the crystal phase transition of CG and the proportion increase of alkali minerals, contributing to the stronger interaction ability and higher adhesion energy with asphalt binder. Owing to the positive changes of CG during calcination process, the corresponding CGAM exhibits superior deformation resistance property under recycling loads at high temperature and flexural creep ability at low temperature, especially when the calcination temperature rises to 750 ℃. • Particle size distribution and morphology of activated CG are closely related to calcination temperature. • Thermal activation process on CG triggered to changes of mineral compositions. • 750℃ is suggested calcination temperature considering both of high and low-temperature properties of CGAM. • The adhesion energy of asphalt binder with activated CG increased with the ever-rising calcination temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • The thermal properties of coal at cryogenic conditions (−100 to 0 °C) is investigated. • The thermal diffusivity of coal increases by 121.4 % with decreasing temperature. • The specific heat capacity of coal decreases by 57.9–65.9 % with decreasing temperature. • The volatile matter and carbon content in coal have the highest correlation with thermal properties (∼0.9). • The thermal diffusivity of coal increases with increasing volatile matter content but decreases with increasing carbon content. The thermal properties of coal are important factors that influence the heat and mass transfer during the pyrolysis process. Therefore, thermal properties were investigated for two tar-rich coal under cryogenic temperature and pyrolysis condition using laser flash analyzer. Gray correlation analysis and chemical composition analysis are combined to analyze the impact of chemical properties on thermal properties. With decreasing temperature, the thermal diffusivity of coal experiences a significant increase by 108.9–121.4 %, while the specific heat capacity decreases by 57.9–65.9 %. The volatile matter and fixed carbon content in tar-rich coal have the highest correlation with thermal properties (∼0.9), followed by moisture content (∼0.62), while the ash content has the lowest correlation with thermal properties (∼0.5). The thermal diffusivity of tar-rich coal increases with increasing volatile matter content. Furthermore, within the range of −100 °C to 300 °C, the thermal diffusivity of tar-rich coal decreases with increasing carbon content, while the specific heat capacity increases with increasing carbon content. The results indicate that under low-temperature cryogenic conditions, the internal heat transfer capability of tar-rich coal is significantly improved. [ABSTRACT FROM AUTHOR]

• Coal-breaking using water jets at different reservoir temperatures was studied. • When temperatures exceed 75.0 °C, the depth of pit increases by 81.0 %, the specific energy consumption decreases by 52.4 %. • The threshold fracturing pressure presenting an exponential trend as coal temperature increases. • Coal-breaking shifts from a "water wedge" dominated mode to a "water wedge-thermal fracture" as temperature increases. The development of abundant deep coalbed methane (CBM) resources has attracted significant attention due to their commercial development potential. However, developing such resources presents many challenges due to their generation in complex geological environments governed by high temperatures and stresses. Thus, this work investigated coal fragmentation using water jets at different reservoir temperatures. The results show that compared with room temperature conditions, under water jet impact, the threshold fracturing pressure of high-temperature coal is lower, the rock-breaking volume is larger, and thermal stress leads to intensified dynamic damage. Indeed, when the temperature exceeds 75.0 °C, the coal undergoes volume fragmentation, and the depth of water jet-breaking coal increases by 81.0 %, while the specific energy consumption decreases by 52.4 %. The threshold fracturing pressure rapidly decreases as temperature increases and stabilizes, presenting an exponential trend. When the temperature exceeds 75.0 °C, the threshold fracturing pressure is maintained at around 10.0 MPa and no longer decreases with the temperature increase. In addition, three-dimensional (3D) damage field analysis highlights that the coal breaking mode shifts from a "water wedge" dominated mode to a "water wedge-thermal fracture" mode as temperature increases. Finally, the dynamic fracturing mechanism of coal under high-temperature conditions of water jet impact has been revealed. The research results of this paper provide a theoretical basis for the hydraulic permeability enhancement design of deep coal seams. [ABSTRACT FROM AUTHOR]

• Pyrolysis of bituminous coal under high-temperature thermal shock is studied. • Relationship between pyrolytic gas product and particle morphology was analyzed. • Carbon matrix purification is a successive process linear with temperature rise. • Graphitization of coal carbon structure was found to exist an abrupt temperature. The current investigation aims to reveal the pyrolysis characteristics and particle microstructure evolution of bituminous coal under the high-temperature thermal shock. In the experimental temperatures, the purification of carbon matrix in the coal char is a successive process linear on temperature. In contrast, the graphitization process of carbon structure existed a transition temperature (1600 ℃). Specifically, the range of 1000–1500 ℃ is critical for the transformation of amorphous carbon to disordered graphite, but the growth of graphite microcrystals was minimally affected. While the range of 1600–1900 ℃ is critical for the formation of the graphite-like carbon structure. It is characterized by the release of defective structures such as oxygen-containing functional groups, and a significant increase in crystal size. Although beneficial for the subsequent study of carbon materials, the ordered graphite transformation led to the deactivation of char. The pyrolysis behavior study under thermal shock insight into the thermal behavior of coal char in high-temperature furnaces, as well as a new idea for the clean utilization of coal resources. [ABSTRACT FROM AUTHOR]

Understanding the molecular mechanism underlying coal's thermal gravimetric behavior is crucial for advancing efficient and clean coal utilization technology, a task that remains challenging to address experimentally. ReaxFF molecular dynamic simulation has been widely applied across various systems and materials, particularly excelling in simulating combustion and pyrolysis processes with complex coal models. It is necessary to establish more connections between simulation and experiment, and to analyze and discuss the differences between them. This will lay the foundation for the reliability of simulation results in revealing experimental phenomena. In this study, coal was divided into four components using a full component classification method: the dense medium component, loose medium component, heavy component, and light component. The connections of the simulated and experimental thermal gravimetric behaviors of the coal group component skeletons were conducted, and founding the inconsistencies in the later stages of the curves. To understand these discrepancies, the test environments were analyzed, identifying the behavior of tar free radicals generated during pyrolysis as a key factor influencing the thermo-gravimetric curve. To mitigate the influence of tar free radicals and reduce the observed differences, a correction coefficient was introduced into the calculation formula for the yield of non-volatile products, achieving an improved alignment between the simulated and experimental thermo-gravimetric curves. This study significantly advances the application of ReaxFF molecular dynamics simulation in elucidating the mechanisms of coal pyrolysis. • The behavior of tar free radicals is main influencing the thermogravimetric curve. • The formula for the yield of non-volatile products could introduce a correction factor. • The correction factor varies depending on the type of coal used. [ABSTRACT FROM AUTHOR]

Oily sludge (OS) is a solid waste generated from oil industry activities that can threaten the ecological environment and human health if not properly treated or disposed of. In this paper, the thermal behavior and emission of gas products during the co-combustion of rice straw (R) modified OS (OS 5 -R 5) and coal (C) were investigated using an automatic calorimeter and model analysis. The effect of combustion atmosphere and additives on the gas products emission during the co-combustion of C, R, OS 5 -R 5, and mixed fuels were investigated. The results show that as the content of OS 5 -R 5 increased in mixed fuels, the performance of mixed fuels worsened gradually. When the mass content of OS 5 -R 5 is 30 %, the lower heating value (LHV) was about 20 MJ/kg, which is about 16 % lower than that of C, but the comprehensive combustion index had no significant decrease. The additives could control the emission of pollutant gases. The increase of heating rate from 5 °C/min to 20 °C/min resulted in an increase of the overall combustion performance of the mixed fuel by 5.07-time. Similarly, increasing the oxygen concentration from 10 % to 100 % led to a 3.09-time increase in the combustion index of the mixed fuel. The adsorption of polar molecules by montmorillonite was conducive to reducing the emission of pollutant gases. BaO and CaO do not affect NO and NO 2 emission control but reduce H 2 S and SO 2 emissions because BaO and CaO could react with H 2 S and SO 2 to form sulfate resulting in reduced emission. The research provides a theoretical basis for OS's safe disposal and efficient resource utilization. [ABSTRACT FROM AUTHOR]

• The image intensifier is firstly adopted to get the image of particles in gasifier. • Coal particles in the gasifier are reclassified according to particle temperature. • Thermal behavior of particles at different temperature is comparatively studied. • The in-situ temperature diagnosis of particles during char oxidation is obtained. • Char oxidation is divided into three reaction stages as per temperature and area. The thermal behaviors of high-temperature particle (HTP) and low-temperature particle (LTP) are investigated based on the bench-scale impinging entrained-flow coal-water slurry (CWS) gasification experimental platform with a modified visualization system. The size and velocity distribution of both particles, and the evolution of HTP are analyzed through the algorithmic and precise processing of the image sequences. In addition, in-situ temperature diagnosis of the particles during the reaction process were realized. The typical evolution process and the temperature of HTP in char oxidation stage are obtained. The results show that the concentration of HTP in the gasifier is greater than LTP, but the particle size is relatively small. Particles moving at the low speed (0–2 m/s) account for the largest proportion of both HTP and LTP. The char oxidation process lasts over 300 ms and can be divided into three reaction stages. During the reaction, the peak temperature at the center of the particle can reach more than 2000 K. The average temperature of the particles gradually increased, reaching a peak in reaction stage II (1500 K) followed by a gradual decrease. The particle temperature is affected by O/C and is prone to experience swelling and bubbling phenomena during char oxidation. [ABSTRACT FROM AUTHOR]

Clarifying the microscale reaction mechanism of macerals is crucial for achieving efficient thermal utilization of coals. Herein, we analysed the chemical structures of two coals used in coking for their macerals employing 13C NMR, FTIR, and XPS to build molecules. The pyrolysis behaviours of coals and their macerals were accessed through molecular dynamics of calculating chemical bond characteristics. Results show that inertinite with higher maturity is rich in aromatic, vitrinite with stronger thermal-reactivity is rich in aliphatic, and macerals of coking and gas coal have more advantages in hydrocarbon generation and branch-chain development, respectively. Based on the validated and optimized molecules containing C, H, O, and N elements, it is found that not only the bond lengths of the longest and shortest in macerals from gas coal are greater than those from coking coal, but the thermal response of heteroatom bonds in the former is almost twice that of the later. Moreover, vitrinite and inertinite of coking coal have N–H cleavage to produce active hydrogen in the late stage of bond dissociation, while gas coal lacks this feature. These explain why the pyrolytic properties of different coals and their macerals have variability, guiding the rational selection of coal-based feedstock for industry. [Display omitted] • Molecular differences between vitrinite and inertinite of various coals are elucidated by characterizations and simulations. • Complex carbon-based molecules are constructed by a strategy that prioritizes the structure of trace heteroatoms. • Differences in thermal conversion of coals are revealed by changes in bond lengths of maceral molecules. [ABSTRACT FROM AUTHOR]

Current work presents salient insights from energy audit of a 1050 MW thermal power plant by BEE Certified Energy Auditors. It provides insights into grassroot level data instead of relying only on theoretical calculations, unlike previously published literature. Arresting the air leakages in air-preheater has given total saving of 10.72 million kWh/year, saved 398,978.97 kJ/year, thus saving of 25,322.80 MT of coal/year. Upgradation of insulation resulted in total saving of 6632.208 Million kJ/year, i.e. saving of 510 MT/year of coal. Replacing cooling tower blades material proposed saving of 15,242.4 kWh/year. Installation of Variable Speed Drives for pumps provided saving of 274,836 kWh/year. Replacement of old inefficient pumps with energy efficient pumps has saving potential of 739,632 kWh/year. Pressure reduction in compressors has given saving of 344,794 kWh/year. Thus, in total, this energy audit helped to conserve 12.098 Million kWh & 25,832.80 MT coal/year and consequently, 104,243 tCO 2 /year. Such savings not only help the plant management/decision makers on the monetary front but also identify the avenues for improvement and channelize the resources such time and investment, prudently. Consequently, it has been established that energy audit is a pragmatic tool to achieve energy conservation at grassroot level. [Display omitted] • Energy audit of coal fired thermal power plant to identify significant energy saving potential with minimum investment. • Novel effort to provide fresh insights into air preheater leakage arrest as substantial energy saving avenue. • Saving of 12, 098, 293.30 kWh electricity/year. • Saving of 25,832.80 MT of coal/year. • Saving of 104,243 tCO 2 /year without hefty investment. [ABSTRACT FROM AUTHOR]

Alkali metals and alkaline earth metals (AAEM) are important factors to be considered in coal gasification process, and understanding the release behavior of AAEM under the interaction of volatile-char is the key to realize efficient thermal conversion of coal. In this study, four typical O-containing functional groups (—COOH,—OH, C O,—OCH 3) were used to react with coal char in a fixed-bed reactor, the reaction temperature was set up at 750，800，850，900 ℃ to survey the release characteristics of Ca by different oxygen functional groups during the interaction of volatile-char at different temperatures from a quantitative point of view. The result show that the Ca release rate of coal char is not high in the whole reaction temperature range, and the interaction of O-containing compounds-coal char at lower temperature will increase the O content (C—O and C O) of coal char, the content of Ca in interactive coal chars was higher than that of the coal char. At lower temperature, the order of compounds inhibiting Ca release ability is: C 6 H 5 CHO≈C 6 H 5 COOH > C 10 H 8 O 2 > C 6 H 5 OCH 3. In addition, it also seems that O-containing compounds (except C 6 H 5 COOH) can obviously promote the conversion of ammonium acetate-soluble Ca to water-soluble Ca during the interaction with char. As the temperature increases, the change trend of O-containing functional groups on the surface of sample after interaction is completely opposite to that at lower temperature, the O-containing model compounds undergo de-oxidation, cracking and polymerization in the effect of coal char and AAEM, causing the formation of polycyclic aromatic hydrocarbon on the surface of the char, which hinders the diffusion of Ca from the char to the gas phase. This work is good for enriching and developing the study on the release characteristics of alkali earth metals during the interaction of volatile-char, and provides a theoretical basis for the development of related industries. • The effects of O-containing functional groups on Ca release during volatile-char interaction was studied. • O-containing species inhibit Ca release follows the order: C 6 H 5 CHO ≈ C 6 H 5 COOH > C 10 H 8 O 2 > C 6 H 5 OCH 3. • The possible mechanism of O-containing compounds-char interaction induced Ca release was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Established the relationship between molecular properties and electrode performance. • Biomass is used to realize the value of energy storage. • The carbon source unsaturation is obtained from the double bond equivalent diagram. Porous carbon materials have been considered a kind of promising materials for supercapacitors due to high specific surface area and excellent electronic conductivity. Soluble portions (SPs) acquired from thermal dissolution of carbon-based raw materials have been used as the carbon source for hierarchical porous carbons (HPC). In this work, mixtures of rice straw and coal at different mass ratios were selected as the raw materials for co-thermal dissolution to obtain SP X. The variation of soluble proportions and subsequent impacts on the electrochemical properties of HPC X were investigated. During thermal dissolution, the addition of rice straw increased the content of nitrogen-containing compounds in SP X. Therefore, the specific capacitance of HPC 1/4 is 355 F/g. The specific capacitance of activated carbon material without rice straw is only 299 F/g. The relationship between the molecular characteristics of carbon source and the performance of supercapacitors has been determined. In addition to oxygen-containing compounds, the presence of nitrogen-containing compounds can also lead to a higher electrochemical property for porous carbon materials. [ABSTRACT FROM AUTHOR]

Steam reforming of medium-low temperature coal tar (SRT) to produce H 2 is important for addressing the energy crisis and challenges of global climate change. However, current catalysts still suffer from low H 2 selectivity, low tar conversion and poor long-term stability due to the complex composition of real coal tar. Herein, a series of Ni-Ca/H-Al catalysts were prepared by different methods. The results showed that the acid pretreatment effectively removed the hydroxyl groups on the surface of γ-Al 2 O 3 to form oxygen vacancies (Ov), and the NiO was mainly anchored in the Ov. The cit-Ni-2Ca/H-Al catalyst prepared by citric acid-assisted impregnation exhibited the highest H 2 yield (152.74 mmol/g -tar), while CO 2 was only 22.11 mmol/g -tar. Characterization showed that the addition of CaO improved the dispersion of NiO and increased the Ov concentration. The increase in Ov weakened the Ni O bonds in NiO and facilitated the low-temperature reduction of NiO. The cit-Ni-2Ca/H-Al catalysts prepared by the citric acid-assisted impregnation method had better dispersion and strong basic sites compared with the impregnation and precipitation methods, leading to more active sites for CO 2 and H 2 O adsorption, and improving the carbon build-up resistance and reusability of the catalysts. Py-GC/MS results showed the cit-Ni-2Ca/H-Al had excellent tar deoxidation ability and effectively promoted the breakage of C C bonds in furans, benzene ring branches, and C O bonds in aliphatic hydrocarbons. The cit-Ni-2Ca/H-Al catalyst exhibited high tar conversion (90.96%) and H 2 yield (146.27 mmol/g -tar) without any treatment for at least 8 cycles. Interestingly, the H 2 yield reached 151.58 mmol/g -tar by the simple regeneration of cit-Ni-2Ca/H-Al. This study provides a theoretical basis for efficient steam reforming of real coal tar for H 2 production and catalyst preparation. [Display omitted] • The acid wash pretreatment increased the oxygen vacancies on the γ-Al 2 O 3 surface. • The oxygen vacancies provided defect sites for NiO anchoring. • CaO improved the dispersion and strong basic sites of the catalyst. • Cit-Ni-2Ca/H-Al showed high H 2 yield (152.74 mmol/g) and low CO yield (22.11 mmol/g). • Cit-Ni-2Ca/H-Al catalyst showed excellent reuse and regeneration performance. [ABSTRACT FROM AUTHOR]

Biomass/coal co-combustion presents a promising avenue for reducing carbon dioxide emissions. However, the mechanism of NO generation during co-combustion in pulverized coal-fired furnaces remains unclear. Herein, this study investigates NO emission characteristics at elevated temperatures, emphasizing mechanistic understanding. The experiments and simulations were conducted across temperatures ranging from 1000 °C to 1600 °C. In addition to exploring how fundamental conditions (temperature, oxygen concentration, and biomass blending ratio (BBR)) affect NO generation, the study also investigates the interactions between biomass and coal, as well as between fuel NO and thermal NO. The results indicate that the change in NO production with increasing temperature is non-monotonic, attributable to the combined contribution of fuel NO and thermal NO. Moreover, the interaction between biomass and coal manifests predominantly during the char combustion stage, owing to the disparate combustion characteristics and reactivity of biomass char and coal char. Numerical simulations were highly consistent with the experimental findings, underscoring a reduction in the rate of production (ROP) for major elementary reactions leading to NO formation as the BBR increased, consequently mitigating NO emissions. By integrating experimental insights with reaction kinetics calculations, this study proposes pathways for fuel NO and thermal NO generation during co-combustion at high temperatures, involving precursors such as NCO, HNO, and NH. These findings offer a deeper understanding of the mechanism of fuel NO and thermal NO emission during co-combustion at high temperatures. [Display omitted] • NO emission characteristics at 1000–1600 °C of co-combustion were investigated. • Biomass-coal interaction on NO emission was explored using PCA and deviation analysis. • Non-monotonic change in NO emission with temperature, due to thermal NO formation. • Temperature increase affected the conversion pathways of NH and HNO. • Proposed thermal NO and fuel NO generation paths at high temperatures. [ABSTRACT FROM AUTHOR]

Coal smouldering fires are global disasters and notoriously challenging to characterize. To better understand combustion and chemistry within these coal fires, TG-DSC experiments were carried out in two different coal samples in nitrogen and oxygen-limited (including ambient air) atmospheres. A mechanism with 8-step reactions simulating coal combustion was proposed, including one drying, two pyrolysis, two oxygen adsorption, and three high-temperature oxidations. The kinetic parameters were optimized via a Genetic Algorithm (GA). It was found that this 8-step mechanism created unnecessary overfitting to the TGA data. Therefore, two alternative schemes were developed with 5- and 4-step, which included and neglected oxygen adsorption, respectively. To compare the two schemes, GA and Gaussian multi-modal fitting were used to quantify the mass change rates in each step and their thermal effects as functions of oxygen concentrations. Moreover, the heat flow rates of coal samples were calculated and compared with measured DSC curves. The results indicated that oxygen adsorption could play a critical role in the transition from water evaporation to high-temperature combustion, and the 5-step scheme could reflect coal's intrinsic oxygen-limited combustion characteristics more accurately. Altogether, this study provides novel insight into coal smouldering under oxygen-limited conditions. • A multi-step scheme governs coal combustion in various oxygen-limited atmospheres. • Only dried coal adsorbs oxygen, while semi-coke oxidation occurs in rapid combustion. • Secondary oxidation of semi-coke creates unnecessary overfitting of TGA data. • Polycondensation and its products' oxidation are prevented by competition in O 2. • Oxygen adsorption is critical to balance overall heat released from coal smouldering. [ABSTRACT FROM AUTHOR]

Colombia is a country rich in coal deposits; however, there are few published studies characterizing these coals in detail from a scientific perspective. This study investigates the thermal maturity and depositional environment of a coal seam from the Guaduas formation (Maastrichtian-Paleocene) of the Eastern Colombian Cordillera Basin, providing insight into burial and temperature history and changes in the depositional environment over time. This three-meter-thick hard coal seam reflects about 20 m of former peat deposition, representing a period of roughly 10.000 years. Five large, fresh samples (A to E) were collected from the seam every thirty centimeters and divided into seventeen sub-samples analyzed using organic petrological methods, Rock-Eval pyrolysis and organic geochemistry. Different thermal maturity- and depositional environment-related parameters have been determined. Results reveal a maturity of approximately 0.9% vitrinite reflectance, and relatively high HI values (kerogen type II-III). Correspondingly, high values of νCHx over γCH indicate a high relative abundance of aromatic rings over aliphatic groups. Moreover, high CH 2 /CH 3 ratios suggest long and simple aliphatic chain structures. Molecular data indicate a balanced odd- over even n -alkane distribution and a high amount of long-chain n -alkanes. High Pr/Ph ratios and hopanoid biomarkers reveal an oxidizing depositional environment. The coal seam investigated in this study is characterized by low ash yields and low sulfur contents particularly in the central part of the seam, while percentages of inertinite are high (up to 54 Vol.-%). This data supports a low water table and oligotrophic, raised bog conditions during deposition in a humid, tropical climate which is consistent with the almost equatorial position of the study area during deposition of the Guaduas Formation. Water was mainly supplied via rainfall leading to overall low ash yields. In contrast, the top of the coal seam is strongly enriched in sulfur revealing that rapid marine flooding ultimately ceased peat accumulation leading to authigenic pyrite formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The raceway behaviours of a slow-moving packed bed solid fuel gasifier are studied mathematically. • The model considers multi-fluid flow, coupled with heat transfer and heterogenous reactions inside and around all the raceways of such a gasifier. • Probability theory and statistics are used to quantitatively analyse the raceway results. The moving-bed gasifier of solid fuels (e.g., coal or biomass) is a key chemical reactor to convert coal or biomass to clean fuel, where the profile of the raceway cavity and its flow-thermal-chemical behaviours can affect the performance of the gasifier, however, they are not well understood because of the process complexity and modelling challenge. In this study, an advanced 3D multi-fluid model, based on the Eulerian-Eulerian method, coupled with heat transfer and heterogenous reactions, is developed to describe the reacting flow behaviours inside and around the raceways. It is found that raceways inside the slow-moving packed bed gasifier are of balloon-like shapes; they are built in just a few seconds after issuing the jet from gas entry, and then both the average velocity for gas and particle are relatively stable. The gauge pressure conditions are not isobaric, and high temperatures, small gas densities and high reaction rates are observed near the raceway "shell". Besides, it is found the raceway behaviours on horizontal cross-section feature more symmetry compared to those on other directions. In addition, probability theory and statistics are used to analyse the quantitative raceway results, and possibilities related to the distributions of gas properties, momentum and species are discussed. This model provides an effective tool to systematically study and optimise raceway behaviours inside a slow-moving packed bed solid fuel gasifier. [ABSTRACT FROM AUTHOR]

Oxy-fuel biomass combustion in a circulating fluidized bed is a clean and sustainable biomass utilization technology. Woody forest biomass is considered a promising source of renewable energy because of its widespread availability across the globe. However, effective biomass utilization in thermal power plants is largely limited by severe ash deposition and corrosion of heat transfer surfaces due to alkali metal and chlorine emissions during biomass combustion. In this study, laser-induced breakdown spectroscopy (LIBS) was applied to detect in-situ gas phase sodium (Na) emission during single particle combustion of widely available forest biomass, namely, beech wood. The operating conditions simulate the thermo-chemical conditions relevant to a fluidized bed combustor system, where the operating temperature varies between 1073K–1273K. This work aims to investigate the effect of O 2 concentration, CO 2 (oxyfuel environment), and particle size on the emission of sodium during the combustion of a single beech wood particle. The unresolved sodium doublet was used as the LIBS signal to quantify sodium emission concentration.Oxygen concentration is the most critical parameter affecting Na emissions, and an increase in O 2 concentration led to higher Na emissions. It is observed that there is a significant reduction in the emission of Na in an O 2 /CO 2 environment as compared to an O 2 /N 2 environment. It is hypothesized that this drop in Na emissions in O 2 /CO 2 environment could be due to lower particle temperatures caused by the lower diffusivity of O 2 in CO 2 as well as the endothermic gasification reaction in high CO 2 environments. In addition, it is reported that the dissociation of sodium carboxylates and carbonates in the biomass matrix to release gaseous Na due to thermal decomposition is retarded at higher CO 2 concentrations which could explain the drop in Na emissions. The effect of biomass particle size is pronounced mainly at lower concentration of O 2 where, larger particles keep Na trapped in its matrix, however, at higher O 2 concentrations (30%), the effect of particle size on Na emission is negligible. [Display omitted] • LIBS used for quantitative sodium(Na) detection from oxyfuel biomass combustion. • Effect of particle size, O 2 concentration, and oxyfuel environment has been studied. • Oxygen concentration is the most important parameter affecting Na emissions. • Chemical effect of CO 2 is prominent in reducing Na emissions. • Lower Normalized Na emitted for a larger particle size at lower O 2 concentrations. [ABSTRACT FROM AUTHOR]

Microwave-assisted coalbed methane (CBM) development is a very promising technology for engineering applications. The mechanism of the macro and micro thermal fracture of coal must be further discussed because of the thermal inhomogeneity of microwave caused by the heterogeneity and structural complexity of coal. In this study, the temperature, weight and P-wave velocity of anthracite were tested under low-energy microwave irradiation. The characteristics of fracture initiation, extension, and connectivity in coal after microwave irradiation were extracted from macroscopic and microscopic observations. Then the mechanisms of microwave thermal fracturing in anthracite were analyzed. The results showed that the temperature of anthracite under low-energy microwave irradiation varies asynchronously. The temperature distributions with high and low temperature partitions exhibit obvious bedding effects. The coal mass loss varies in stages with microwave irradiation time, first increasing slowly and then increasing dramatically above 500 °C. The P-wave velocity presents a decreasing trend with the increase of input microwave energy. Coal generates a complex fracture network at the micro and macro scales, with fractures expanding outwards in a divergent pattern. The nonuniformity of the temperature distribution promotes fracture development. It is related to the asynchronous heating caused by the mineral composition, water content, pore fracture structure, and electromagnetic field in coal. It is of great significance to improve the thermal fracturing efficiency by using the nonuniformity of microwave heat in the application of microwave-assisted CBM development. [ABSTRACT FROM AUTHOR]

• The changes of coal microstructure after microbial treatment were measured. • Effect of microorganisms on oxidation characteristics of coal was mastered. • Mechanism of microbial inhibition of coal spontaneous combustion was revealed. The inhibition of coal spontaneous combustion (CSC) by microorganisms presents an environmentally friendly method to reduce coal oxidation rates in mines and delay natural ignition. In this study, XRD, FTIR, and TG-DTG-DSC experiments were employed to analyze the inhibitory effect of microorganisms on CSC from both microstructural and macroscopic oxidation perspectives. The results indicated that microorganisms enhanced the ordering and graphitization of coal's microcrystalline structure, reduced the number of functional groups, and disrupted aliphatic hydrocarbons and oxygen-containing groups. The average microcrystalline diameter and the number of effectively stacked aromatic layers decreased by 32.04 % and 27.22 %, respectively, while the total area of aliphatic hydrocarbon peaks decreased by 55.56 %. The characteristic temperature points shifted to higher zones, with the maximum weight loss rate temperature and burnout temperature exhibiting significant increases of 67.87℃ and 138.67℃, respectively. The thermal effect of coal oxidation was diminished, with total heat release decreasing by 77.8 J/mg. Additionally, the apparent activation energy (E a) increased by 1.45 times, and the pre-exponential factor (ln A) reduced to 61.05 % of that of raw coal. This study establishes a foundation for future microbial inhibition of CSC. [ABSTRACT FROM AUTHOR]

The crossing-point temperature measurement is a classical thermal test method for ranking the propensity of coal towards self-heating and spontaneous combustion. Despite its longstanding use, it is still considered an empirical approach due to a lack of understanding on its working mechanism, preventing its wide use and standardization globally. In this paper, efforts were exerted to investigate the formation mechanism of the crossing-point temperature (CPT) and the impact of experimental settings on this parameter, aiming at the consolidation of the physical basis of this test method and paving the way for its further development. In light of the principles of heat and mass transfer, the thermal response of a coal sample stored in a cylindrical reactor exposed to linear heating environment was monitored. Fine coal particles were prepared and packed in the reactor with very thin wall, while the moisture content of a sample varied between 5 % and 20 %. The traced temperature histories are in agreement with the available experimental data. Observations indicated that the volume element at the sample center heats up by offsetting the heat sink term resulting from water evaporation. When the central temperature of the sample catches up with the environmental temperature, the heat sink term from water evaporation disappears, and the direction of heat flow via conduction is reversed, indicating the development of a self-heating domain. The impact of sample attributes and experimental settings on the measurement process is the actual reflection of the self-heating performance of a coal sample with specific physical properties and under defined environmental conditions. During the CPT measurement, the status of zero conductive heat flow at the central volume element can be monitored simultaneously, thereby extracting the apparent kinetic parameters of the sample oxidation at the same time. The established understanding sheds light on the broader application of this test method. • Physical nature of the designed thermal system was explored theoretically for the first time. • It was observed that the central volume element of a sample heats up by offsetting the heat sink term. • Heat flow of the central volume goes reverse at the CPT, indicating the self-heating domain. • CPTs are affected by sample attributes and experimental settings, highlighting the practical events. • Kinetic data of sample oxidation can be extracted simultaneously through updated configurations. [ABSTRACT FROM AUTHOR]

[Display omitted] • An evaluation coefficient is established to characterize preheated fuel activity. • Minimum loads for different coal ranks from lignite to anthracite are 25 %–40 %. • Variable load rate tends to decrease with higher coal rank. • Transient surges of CO emissions may occur in the initial phase of load changes. • Dynamic NO x emissions from different coal ranks are less than 335 mg/m3 (@6 % O 2). With the large-scale integration of renewable energy into the power grid, coal-fired power plants shoulder an enormous burden of peak shaving. In this study, the variable load characteristics of different coal ranks were extensively investigated on a 40 kW th down-fired test platform. Moreover, the preheating modification of fuel at ultra-low loads was investigated. A comprehensive evaluation coefficient (E ph) was established to characterize the reactivity of different coal ranks at wide loads. The determination criterion of combustion stability for variable load processes was modified. The results show that the preheating modification of different coal ranks was significant, especially for lower-activity coals such as anthracite and lean coals. The minimum loads after modification were 25 %, 25 %, 35 % and 40 % for ARG (lignite), SM (bituminous), RG (lean coal) and SH (anthracite), respectively. Furthermore, the preheating modification had a positive effect on increasing the variable load rate, which was positively correlated with E ph for different coal ranks. The maximum variable load rates after modification for ARG, SM, RG and SH were 2.78 %/min, 3.13 %/min, 1.79 %/min and 1.15 %/min, which corresponded to the optimum load steps of 25–30 %. The response rate of NO and N 2 O with time in the low-rank coal is faster than that in the high-rank coal during the variable load process, which is consistent with the trend of the variable load rate. In addition, the conversion of nitrogen oxides decreases and then increases with load, and the inflection points corresponding to AGB, SM, RG and SH are 40 %, 38 %, 70 % and 80 %, respectively. The NO x emissions were less than 335 mg/m3 (@6 % O 2) for the different coal ranks during load changes. [ABSTRACT FROM AUTHOR]

This paper describes the evaluation of petrographic textures in char and activated carbon derived from coal, coal by-products and biomass, formed during carbonization and activation processes. This work represents the results of interlaboratory exercises from 2016 to 2022 of the Microscopy of Carbon Materials Working Group in Commission III of the International Committee for Coal and Organic Petrology. The interlaboratory exercises were run on photomicrograph samples. For textural characterization of carbon materials, the existing American Society for Testing and Materials (ASTM) classification system for metallurgical coke was applied. Morphological differences were evaluated in 29 carbon material types, including 22 char samples, and 7 activated carbon (AC) samples obtained experimentally using conventional direct/indirect and microwave heating technologies. This approach gives an extended view on the identification of microporous carbons, and how a certain heat treatment develops a certain optical texture and structure in a raw material. The requested evaluation of carbon materials was related to their porosity, origin, extent, and characteristics, which are particular to each carbon material type. Because carbon matrices can form a wide range of optical textures during heat treatment it is important to demonstrate which carbon occurrences will have a crucial role in industrial applications dominated by adsorption phenomena. The interlaboratory exercises included 17 participants from 14 laboratories. Four sets of digital black and white and colour photomicrographs were distributed, which in total comprised 184 fields of different types of carbon material. The results were evaluated based on four levels: (i) optical texture (isotropic/anisotropic), (ii) optical type and size (punctiform, mosaic, fiber, ribbon, domain), iii) morphology (porous, non-porous/massive), and (iv) particle origin (precursor type). The statistical method applied to evaluate the results was based on "raw agreement indices". Comparative analyses of the average values of the level of overall agreement showed homogeneity in the results, the mean value was 89%, with a minimum value of 87% and a maximum value of 91% for those who participated in at least three out of four exercises. • Char and activated carbon derived from coal and biomass are evaluated. • Classification of metallurgical coke optical texture is used for carbon materials. • Interlaboratory exercise results prove the homogeneity of participants' answers. • Results show a level of overall agreement mean value of 89%. • Optical microscopy can be used as a quality control method for carbon materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coal and amendments significantly increase methane production in incubation. • Machine learning help predict missing biogenic Δ12CH 2 D 2 data. • Clumped isotopes indicate differential reversibility and combinatorial effects. • Coal bioavailability rather than coal thermal maturity determine CH 4 production. Biogenic (microbial) methane is an imperative natural gas resource and plays an important role in the global carbon cycle. Determining isotope systematics in microbially enhanced coal bed methane (MECBM) informs methane biogeochemical processes and environmental impacts. Here, we conduct laboratory MECBM experiments using coal samples of differing maturities (from lignite to anthracite) and report analytical results of methane production, bulk and clumped isotopes (δ13C, δD, Δ13CH 3 D and Δ12CH 2 D 2). We reproduce the differential reversibility in methanogenic reactions, which exhibits a correlation with kinetic clumped isotope fractionation (Δ13CH 3 D from +0.17 ‰ to +4.04 ‰). The exogenous combinatorial effects play a greater role in determining the negative Δ12CH 2 D 2 (<–30 ‰). In the microcosm of MECBM, coal and amendments are suggested to significantly increase methane production (from 82.4 ± 17.1 to 344.6 ± 22.8 μmol CH 4 /g coal), with effects controlled by substrate coal bioavailability rather than coal thermal maturity. This suggests the possibility of MECBM attempts to utilize high thermal maturity coal. We perform machine learning models and improve the accuracy of biogenic 12CH 2 D 2 predictions, which help understand the mechanism of methane formation, and further provide new insights into clumped isotope effects among different biogenic methane sources. Our incubation experimental and compiled dataset (n = 275) better constrain biological participation in the methane formation process and potentially be used for methane sources tracing. [ABSTRACT FROM AUTHOR]

• Effective thermal conversion of coal slag through multiple reactions scheme. • Process was governed by variations in melt viscosity and by the composition gradient. • Successful SiO 2 dissolution was achieved over low activation energy catalytic pathway. • At T = T iso , conversion process is freed from dependence on temperature and pressure. • Enthalpy-entropy compensation effect was identified, with "tunnel effect" phenomenon. This study provides insight into benefits of thermo-chemical conversion of coal slag as recovery process into value-added products. This research involves kinetic analysis of process conducted through non-isothermal thermal analysis measurements, with additional raw material characterization. Kinetic results showed that decomposition proceeds through two consecutive reactions steps (first one, including anorthite P 1̅ → I 1̅ phase transition, and then production of incongruent melting product (ternary system: CaO·Al 2 O 3 ·2SiO 2 (CAS 2), where viscosity of slag changes), and second one including dehydration and formation of meta-muscovite, and subsequently, thermal disruption of muscovite de-hydroxylated phase, which proceeds with breaking of octahedral Al–O bonds), and one single-step reaction (attributed to CO-reduction of hematite to magnetite). Thermodynamic results showed an existence of physically meaningful isokinetic temperature (T iso), which corresponds to active vibrational frequency of surroundings of SiO 2 reaction site, manifested through Si‒O bond weakening by catalytic reaction of freed hydroxide ion (OH−). It was concluded that at temperature T = T iso , the course of process loses its dependence on temperature and pressure, regulating changes between thermodynamic parameters, through enthalpy-entropy compensation (EEC) effect. [Display omitted] [ABSTRACT FROM AUTHOR]

The phase-out of unabated coal power is crucial for meeting climate agreements in coal-dependent economies such as Indonesia and Vietnam. Despite both countries committing to the 2021 Global Coal to Clean Power Transition Statement, translating phase-out pledges into action poses considerable challenges. Drawing insights from interviews with government, civil society, and industry experts, this study identifies the key barriers hindering coal phase-out in each country. Concerns about potentially escalating electricity prices and power shortages loom large, with the former being more prominent in Indonesia and the latter more prominent in Vietnam. The obstacles appear particularly significant in Indonesia for reasons including its higher coal dependence. We conclude that prioritizing renewable energy growth, as well as halting the construction of new coal plants, would be the most practical and viable way forward for both countries rather than an oversized early focus on coal plant closures. The analysis is of high relevance to informing plans under the two countries' Just Energy Transition Partnerships. • Indonesia and Vietnam face significant challenges in coal power phase-out. • Prioritizing renewable energy uptake is crucial for both nations. • International support should emphasize renewable energy. • Vietnam's conducive investment environment positions it for faster progress. • Carbon pricing is highlighted as a key mechanism by Indonesian experts. [ABSTRACT FROM AUTHOR]

The aim of the work is to predict 100% decarbonization of power plant's flue gases; to recover carbon from CO 2 in in-situ mode; to extract valuable metals from ash; and to process ash and converter slag into stone casting. The novelty of the work is the development of a system for the integrated processing of coal in a smelter reactor by using high-temperature off gases in a boiler; carbon splitting according to the formula CO 2 + 2Zn = 2ZnO + C, with the return of "C" to the system; sublimation of Zn from ZnO using a highly efficient counter-impacting jet method. Experiments carried out in a smelter have shown, the degree of reduction of germanium and zinc from slags ∼70%. The specific energy consumption is 2–3 times lower than in an acting analog. In a pessimistic scenario, the net profit of the system will be sufficient to purchase the missing electricity for the distillation unit: for the 60% carbonization of CO 2 , at the cost of electricity from wind turbines $46.3/MWh; in order to fully decarbonize CO 2 - $31.8/MWh. The system's payback period will not exceed 6–8 years, with the expected net profit of $21,660,860/y. The operating principle of the proposed system is as follows (see Figure 1). Fluxed ash is processed in melting unit 1 with the release of a melt suitable for the production of construction products; high-temperature gases from reactor 1 produce steam in boiler 2; CO 2 gases from boiler 2 are split in decarbonization chamber 3 in a steam-zinc flow according to the reactions: Zn + H 2 O ZnO + H 2 ; Zn + CO 2 ZnO + CO; CO + H 2 C + H 2 O; (ZnO, C)-concentrate is captured in an electric precipitator and fed to a distiller to restore zinc and the process is repeated; the distiller is heated with electricity from wind turbines; residual Zn-contained slag is fed to melting unit; gases purified from CO 2 are released into the atmosphere.1-melting reactor, 2-boiler,3-decarbonization chamber, 4-electric precipitator, 5-distillerFigure 1. Simplified diagram of CO2 decarbonization of boiler gases. [Display omitted] • For high ash coal processing, a combination "smelter-boiler' is proposed. • In-situ method for carbon splitting from CO 2 -gases by Zn is developed. • A design for Zn sublimation and condensation in one apparatus is suggested. • A method of Zn sublimation in an arc by counter-colliding jets is developed. • A condition of 100% decarbonization of the boiler's gases is predicted. [ABSTRACT FROM AUTHOR]

[Display omitted] • The TGA and ReaxFF MD methods are coupled to evaluate covalent bonds behaviors. • Coal thermal decomposition is elucidated by conversion of covalent bonds abundance. • Coal structural transformation is studied using synchrotron radiation techniques. • Heating rate effects on coal conversion are clarified at micro- and meso- levels. The impact of pyrolysis reaction environment on coal coking behavior contributes to comprehensive understanding of coking mechanism and oriented regulation on coke-making process. The decomposition of coal molecule and the thermal cleavage of covalent bonds under various heating rates were analyzed using the Thermogravimetric Analysis (TGA) technique combined with the Reactive Force Field Molecular Dynamics (ReaxFF MD) method. The heating rate effects on micro-level structural evolution of coal macromolecule was revealed based on the abundance evolution of covalent bonds. Particularly, the evolutions of pore and carbon structures of coal particle during coking were in-situ investigated using the synchrotron radiation Small Angle X-ray Scattering (SAXS) in conjunction with Wide Angle X-ray Scattering (WAXS) techniques. The analyses reveal that the coal molecule is activated through decreasing the hydrogen bonds and van der Waals interactions and the H•and CH 3 • radicals are remained in coal during rapid heating before 400 °C. The high heating rate promotes the breakage of C al - C al /H and C ar - C al bonds while impends rupture of C al - O, C ar - O and C ar - C ar bonds, resulting in decreased total weight loss and developed fluid phase. The rapid pyrolysis affects the delicate equilibrium between disturbance of volatiles escape and orientation of aromatics flowing, determining nanopore and carbon crystal properties of semi-coke. This work is expected to demonstrate the rationality of "Structure Derivation Coking Mechanism" and offer scientific foundation for regulating the coking behavior in various coke ovens. [ABSTRACT FROM AUTHOR]

To investigate the effect of structure difference of coals on its yield and characteristics of thermal dissolution extracts (TDEs), four Xinjiang low-rank coals were chosen for thermal dissolution extraction using 1-methylnaphthalene (1-MN) as the solvent at 380 °C. The low-rank coals were divided into TDEs consisting of deposit (DP) precipitated at room temperature in 1-MN and soluble (SL) dissolved in 1-MN, along with a minor proportion of liquid and gas products, as well as residue. The results showed that TDEs yields of Qidaowan (QDW), Heishan (HSC) and Runbei (RBC) coal samples increased with the increase of volatiles. However, almost the same TDEs yield was obtained for Hefeng coal (HFC) as RBC despite of higher volatiles content of the former. Further analysis suggested that both higher volatiles content and aromatic carbon ratio contributed to the formation of TDEs when 1-MN was used as the solvent. Besides, significant differences of carbon types for the above coal samples were observed, wherein, HFC possessed the lowest aromatic carbon of 45.59%, yet the value for all the DPs and SLs were above 60%, falling in the range of 60%-68% and 66%-71%, respectively. Furthermore, the aromatic ring cluster of DPs was composed of 2–3 rings, while that for SLs was 1–2 rings on average. Moreover, the TDEs obtained from coals with higher oxygen content were also characterized by a relatively higher oxygen content, and a higher content occurred on DPs. The molecular weight, polydispersity index and methylene chain length of DPs and SLs located in the range of 1000–1800 amu, 2.0–4.4, and 0.8–2.3, respectively. And it was found that good caking properties similar to coking coals occurred on the DPs and SLs, ranging from 88 to 97. Results also exhibited that there was a positive synergistic effect for caking index of DP & SL mixture. This work provides a theoretical basis for low-rank coal as an alternate to coke coal by thermal dissolution extraction. • High volatiles and aromatic contents in coals favor the formation of TDEs with 1-MN. • DPs and SLs primarily comprise 1–2 and 2–3 aromatic ring cluster, respectively. • Compared to DPs, SLs exhibit higher H/C ratios and dispersity indexes. • There exists positive synergistic effect for caking index of DP & SL mixture. [ABSTRACT FROM AUTHOR]

Coal is the primary fossil fuel in China's energy sector. As the amount of mining continues to increase, the high concentration of dust generated poses a severe threat to equipment and frontline workers. The coupling influence of HCl and temperature on the structure and wettability of coal were conducted by experiments. The phenomenon indicates that the contact angle between coal treated with HCl of different temperatures and water is reduced, the settling distance in an aqueous solution is longer, and the effect is significant with the increase of temperature, demonstrating the acid-thermal coupling solution improves the wettability of coal. Secondly, detailed analysis of coal functional groups and surface element, shows that the percentage of hydrophilic groups increased, such as OH⋯O, free –OH, and hydrophobic groups were destroyed, such as the asymmetric deformation vibration of adjacent H. The L, 'C' , and DOC show an increasing trend, while I first increase and then decrease by analyzing the trends of IR indices of coal. The conclusions prove that the degree of coal deterioration changed after treatment with acid-thermal coupling conditions. The influence mechanism of acid-thermal coupling solution on coal was explored to provide ideas for improving the wettability of coal from the source. • The effect of acid-thermal coupling on the wettability of coal was studied. • The influence of acid-thermal coupling on functional groups in coal was analyzed. • Acid-thermal coupling has an impact on the degree of coal metamorphism. • As The temperature increases, the acid-thermal coupling effect is significant. [ABSTRACT FROM AUTHOR]

Currently, lignite-fired boilers often feature low thermal efficiency, difficult coal pulverizing and poor combustion stability owing to lignite having high water content. A novel lignite-fired power generation process is proposed in this paper with using a superheated-steam-drying open-pulverizing-system boiler (SSD-OPSB) and a deep utilization of waste heat from the steam for coal drying. Through using an open pulverizing system, the problems of low furnace temperature and low boiler efficiency are resolved. Meanwhile, the operation safety of the coal pulverizing system is ensured by using superheated steam as the drying agent. This paper described the working principle and engineering feasibility of the SSD-OPSB process, and established analysis model for its thermo-economic performance. Energy savings and environmental benefits of applying the process were calculated and discussed based on an in-service 600 MW supercritical power unit firing lignite with water content of 39.5% at its turbine heat acceptance condition. The result shows that for the power unit, applying the SSD-OPSB process can decrease coal consumption by 6.86% under the same power supply, meanwhile recovering water by 132.2 t/h and reducing CO 2 emission by 27.78 t/h. It indicates that the SSD-OPSB process would significantly benefit lignite-fired power plants regarding energy-saving and environmental protection. • Lignite-fired boilers can benefit greatly from applying open coal pulverizing systems. • The benefits include marked coal-savings, enhanced coal combustion and water recovery. • A novel superheated-steam-drying open-pulverizing-system was proposed for applications. • Waste heat and water recovery system was designed to the new power generation process. • The model of analyzing thermo-economic performance of this process has been developed. [ABSTRACT FROM AUTHOR]

• Applicability of generalized fracture criteria on thermally treated rocks. • Rock fracture behaviour in granite and mudstone under thermal effect. • The effect of thermal treatment on fracture process zone (FPZ). • The effect of thermal treatment and loading mode on brittle-ductile transition of fractured rocks. Temperature and thermal damage have a major impact on the behaviour of fractures in the earth's crust. For deep earth engineering such as underground coal gasification, geothermal energy extraction, and nuclear waste repositories, developing fracture criteria governing the propagation of fractures under thermal effect is crucial. As a result, the ability of stress, energy, and strain-based fracture criteria to predict rock fracture behavior both before and after thermal treatment is assessed in this paper considering two rock types; granite, and mudstone, which are very different from one another in terms of their mineralogical composition and mechanical properties. The overall findings showed that the energy-based criterion was more effective in predicting fracture parameters both before and after thermal treatment than the stress and strain-based criteria. Specifically, after thermal treatment at 500 °C for the granite, and at any temperature for the mudstone, the strain-based criterion was no longer valid. It was found that the temperature and loading mode have a significant impact on the granite's transition from brittle to ductile, where this transition can occur at an approximated temperature of 460 °C. Meanwhile, an increase in brittleness with rising temperature was noted in mudstone. Moreover, the Fracture Process Zone (FPZ) size was predicted by the energy-based criterion to be greater than that predicted by stress and strain-based criteria. It was found that the FPZ size is proportional to the brittleness degree of the two rock types, which is considerably impacted by thermal treatment. In addition, this study discusses several critical areas in rock fracture mechanics in the presence of thermal effects including fracture envelopes under mixed mode loading I/II, fracture stress, and initial crack extension angle. All of these are of high importance in assessing the safety and stability of rock structures in the presence of thermal effects. [ABSTRACT FROM AUTHOR]

The paper presents the results of numerical experiments on the implementation of Over Fire Air (OFA) technology at a coal burning thermal power plant (TPP) in order to reduce emissions of harmful substances into the atmosphere. To implement the OFA technology, various options for supplying additional air through injectors in the upper part of the combustion chamber have been studied. For the first time, various heights (h = 8 m, 9 m, 10 m, 11 m, 12 m) of the location of OFA injectors in the combustion chamber at the kazakh TPP were studied. For the first time, different volumes of additional air supply through the injectors are simulated when OFA is 0% - this is the base case (traditional combustion) and when OFA is 5%, 10%, 15%, 18%, 20%, 25% and 30% of the total volume air required for complete combustion of the fuel. It is shown that at the optimal location height of OFA injectors (h = 9 m), an increase in the volume of additional air to 18% leads to a decrease in the concentrations of carbon monoxide CO by about 36%, and nitrogen dioxide NO 2 by 25% compared with the base case (OFA = 0%). • The effect of Over Fire Air (OFA) technology on furnace processes has been studied. • Found the optimal location of OFA-injectors in the combustion chamber. • Found the optimal amount of additional air flowing through the injectors. • OFA technologies optimize the combustion process and reduce harmful emissions. [ABSTRACT FROM AUTHOR]

The co-firing of the non-carbon fuel, ammonia, with pulverized coal, is an effective way to reduce CO 2 emissions in thermal power plants. However, the high nitrogen content of ammonia increases the risk of high NO x emissions during the co-firing process. To achieve low nitrogen combustion of ammonia-coal co-firing, it is necessary to study the impact of ammonia on the N migration and transformation characteristics, during the coal pyrolysis and combustion processes. In this work, the effects of ammonia on the release of N-containing products, during coal pyrolysis, were studied by quantum chemistry calculations and pyrolysis experiments. The theoretical calculation results showed that the mixing of hydrogen-rich ammonia fuel promoted the generation of HCN during coal pyrolysis and increased the energy consumption of HCN generation. Additionally, ammonia-N could be embedded into the coal char structure and exist in the form of N-6. The experimental results indicated that with the temperature increasing, the N content of the coal char and the pyridinic-N increased under the condition of ammonia-coal co-pyrolysis, confirming the microscopic mechanism of ammonia-N embedding into the coal char structure, as indicated by the theoretical calculations. Our work reveals the molecular paths of N migration and transformation and elaborates on the interaction mechanism of ammonia-N and coal-N during the ammonia-coal co-pyrolysis, which has a certain promoting effect on the development of ammonia-coal co-firing mechanism. [ABSTRACT FROM AUTHOR]

The reducing agents used for industrial silicon production often suffer from high coking and high consumption of coal, which is associated with high energy consumption, low efficiency, and low output. To overcome these issues, a mixture of biomass and soft coal (SC) was investigated as a new type of carbonaceous reducing agent for industrial silicon production. In this paper, TGA, SEM, XRD, and Raman spectroscopy were used to study the effects of the different proportions of banana peel (BP) and SC on the activity of carbon materials under different fermentation conditions and molding times. The results showed that the pyrolysis temperatures of fermented mixed carbon materials were decreased by 38–55 °C, and the activation energy was reduced by 68–74%. The pyrolysis temperature and activation energy of moldy mixed carbon materials decreased by 49–94 °C and 46–51%. There was a significant synergistic effect between the carbon materials, and the reactivity of SC was increased. The reduction of silica by fermented carbon materials was better than moldy carbon materials; therefore, the fermentation conditions were more conducive to the preparation of carbonaceous reducing agents for the production of industrial silicon. [ABSTRACT FROM AUTHOR]