Search Results (4,674)

This study presents an experimental evaluation of the bioenergy potential of Enterolobium cyclocarpum (“orejero”) fruit peel residue, an underutilized agroforestry by-product in tropical America. Although the species is widely used for shade and fodder in livestock systems, its fruit peel has not yet been characterized for energy recovery purposes. Fruit samples were collected in rural areas of Tesalia (Huila, Colombia), and the peel fraction was analyzed in certified laboratories. The moisture content of the peel was determined as 11 wt%, and the lower heating value was measured as 0.015 TJ/t following ASTM E711-06. Elemental analysis according to ASTM D5373-16 yielded (dry basis): 37.2 wt% C, 4.09 wt% H, 0.45 wt% N and 0.13 wt% S. Based on Colombian cultivation and production data, the theoretical energy potential was estimated as 3.6 TJ/year per hectare. The technical energy potential reached 0.18 and 0.21 TJ/year per hectare for combustion and gasification, respectively. CO₂-equivalent emissions were also estimated for both conversion routes, revealing a trade-off between the higher energy yield and higher specific emissions associated with gasification. Overall, the results show that E. cyclocarpum fruit peel residue has a calorific value comparable to widely used agri-food residues in Colombia (e.g., sugarcane bagasse and oil palm fiber), but with a substantially higher per-hectare energy potential due to its large residue fraction. Its high availability, favorable fuel properties, and compatibility with decentralized combustion and gasification technologies support its use as a promising feedstock for bioenergy generation in rural or off-grid areas, in line with circular economy and sustainable energy transition strategies. Full article

This paper presents a numerical study on the deployment of Overfire Air (OFA) technology in coal-fired thermal power plants in Kazakhstan to reduce harmful emissions. The simulation utilized a digital model of the combustion chamber of the BKZ-75 boiler at Shakhtinsk thermal power plant, which utilizes high-ash Karaganda coal containing 35.10% ash. During the development of two-stage combustion technology, different methods of supplying extra air via OFA injectors were examined. Various positions within the combustion chamber were evaluated for their placement: at heights of h = 0.165 m; 0.75 m; 1.375 m; 2.25 m; 2.5 m; 8 m; 9.4 m; 10 m; 11 m; and 12 m. The baseline combustion mode (OFA = 0%) and several additional air injector settings were analyzed, including OFA levels of 5%, 10%, 15%, 18%, 20%, 25%, and 30% of the total air volume. Numerical simulations generated temperature distributions along with carbon monoxide (CO) and nitrogen (NO) concentration fields, both inside and outside the combustion chamber outlet. Research indicates that the most effective reduction in pollutant emissions happens when OFA injectors are positioned at 9.4 m and supply supplementary air at an OFA rate of 18%. Under these settings, the carbon monoxide concentration at the combustion chamber outlet decreases by approximately 36%, while nitrogen oxide levels drop by 25%, compared to the baseline condition (OFA = 0%). These insights can be utilized to upgrade boiler units, promoting cleaner fuel combustion in coal-fired thermal power plants. Full article

Under the influence of multiple factors such as climate change and human activities, the frequency, intensity, and destructiveness of forest fires are increasing, which may trigger multiple ecological crises. Forest fires can be scientifically prevented, and their risks can be mitigated through specific approaches, particularly by managing forest combustible materials. Common methods include mechanical clearance, prescribed burning, and the establishment of biological firebreak belts, along with the application of grazing to regulate forest fuels. This paper presents a review of studies on grazing and fire risk, both domestically and internationally. Research indicates that livestock grazing has complex effects on forest fire risk: appropriate grazing can manage fuels and modify ecosystem structure to reduce fire hazards—for instance, by decreasing the accumulation of surface flammable materials and promoting the regeneration of fire-resistant tree species. Conversely, overgrazing may disrupt ecological balance and increase fire risk, such as by exacerbating soil erosion and encouraging the invasion of flammable weed species. Case studies from different ecological regions worldwide demonstrate varied effects of grazing on fire prevention, though research in this area exhibits geographical disparities. Adaptive management should integrate targeted grazing, prescribed burning, and mechanical treatments in a synergistic manner. Future efforts should prioritize cross-scale studies, investigate the mechanisms of woody fuel modulation, and refine fire ecology models to enhance the precision and global applicability of grazing-based fire management. Full article

Direct injection in hydrogen engines enables flexible combustion control, improves engine efficiency, and reduces the risk of abnormal combustion. However, implementing this injection strategy is challenging due to the need to provide a relatively high volumetric fuel flow rate, achieve a specified degree of mixture stratification, and account for the functional and technological limitations of the injection system. These challenges highlight the relevance and objectives of the present study. The mathematical model of a turbocharged engine cycle has been refined to account for the influence of injection parameters on combustion kinetics. On the basis of mathematical modeling, the injection pressure and injector area were determined to ensure the specified injection conditions. For the late injection strategy, a method was proposed to select the start of injection based on a specified value of the “relative ignition timing” criterion. Engine operation was simulated across the full range of operating modes for both early and late injection strategies. The results show that the late injection strategy increases the maximum indicated thermal efficiency by approximately 2%, reduces peak in-cylinder pressure by about 1 MPa, lowers maximum nitrogen oxide emissions by a factor of 1.4, and ensures knock-free operation across all modes compared to early injection. Full article

Fluidized bed combustion of biomass requires maintaining stable properties of the inert bed material, which plays a key role in heat transfer, temperature stabilization and uniform fuel distribution in circulating fluidized bed (CFB) boilers. During long-term operation, quartz sand, i.e., the most commonly used inert material, undergoes physical and chemical degradation processes such as attrition, sintering and coating with alkali-rich ash, leading to changes in particle size distribution (PSD), deterioration of fluidization quality, temperature non-uniformities and an increased risk of bed agglomeration. This study analyzes quality management strategies for inert bed materials in biomass-fired CFB systems, with particular emphasis on the influence of PSD on boiler hydrodynamics and thermal behavior. Based on industrial operating data, sieve analyses and CFD simulations performed under representative operating conditions, a recommended mean particle diameter range of approximately 150–200 μm is identified as critical for maintaining stable circulation and uniform temperature fields. Numerical results demonstrate that deviations toward coarser bed materials significantly reduce solids circulation, promote segregation in the lower furnace region and lead to local temperature increases, thereby increasing agglomeration risk. The study further discusses practical approaches to bed material monitoring, regeneration and make-up management in relation to biomass type and ash characteristics. The results confirm that systematic control of inert bed material quality is an essential prerequisite for reliable, efficient and low-emission operation of biomass-fired CFB boilers. Full article

The energy transition in the transportation sector makes hydrogen a promising candidate as a fuel for internal combustion engines; however, its tendency to knock limits its use to lean mixtures, resulting in a reduction in performance. In this context, water injection represents a technical solution capable of reducing both the risk of knocking and the pollutant emissions of nitrogen oxide (NOx). Although several studies have been published on the benefits of water injection, its capacity to suppress high-intensity knocking phenomena was never investigated and is not traceable in the scientific literature. On account of this lack, the authors of the present paper experimentally evaluate the effectiveness of port water injection in suppressing high-intensity knock phenomena and its potential in terms of nitrogen oxide emission reduction. Differently from previous works, a highly reactive fuel (PRF60) was adopted to reproduce, as closely as possible, the knocking tendency of hydrogen. The tests were carried out on a single-cylinder CFR engine, suitably modified to allow port water injection, operating with stoichiometric air–fuel mixture (λ = 1) and at low engine speed, which constitutes the most critical condition, since it allows for heavy knocking and is less favorable for injected water evaporation. Moreover, aiming to assess the effect of spray atomization, the tests were repeated using three different water injection pressure levels. The study presented, however, is confined to the effects of port water injection on knock suppression and NOx emission reduction, while no engine performance or efficiency variation were considered. The results showed that port water injection, with water addition up to 40% by mass with respect to fuel, enables an almost complete suppression of high-intensity knocking phenomena, along with a significant reduction in NOx emissions (up to −62%). Full article

Iron powder represents a promising carbon-free, sustainable fuel, yet its practical utilisation in combustion has not yet been realised. Achieving stable, efficient iron-only flames is challenging, and the environmental impact of hybrid iron-hydrocarbon combustion, including particle emissions, is not fully understood. This study investigates hybrid methane–iron powder flames to assess iron’s role in modifying gas and particle phase emissions and its potential as a sustainable energy carrier. The combustion of iron was investigated at both the single particle and powder flow scales. Experimental diagnostics combined high-speed and microscopic imaging, ex situ particle sizing, in situ gas analysis, and aerosol measurements using an Aerodynamic Particle Sizer (APS™) and a Scanning Mobility Particle Sizer (SMPS™). For single particle combustion, high-speed imaging revealed rapid particle heating, oxide shell growth, cavity formation, micro-explosions, and nanoparticle release. For powder combustion, at 0.5 g/min and 1.26 g/min, the experiment yielded oxidation fractions of 15.15% and 23.43%, respectively, and increased CO₂ emissions by 0.22–0.35 vol% relative to methane–air flames, while NOx changes were negligible. Aerosol analysis showed a supermicron mode at ~2 µm and submicron ultrafine particles of 89% <100 nm with a modal diameter of ~56 nm. The observed ultrafine particle emissions highlight the need to evaluate health, material-loss, and fuel-recycling implications. Burner optimisation or premixed strategies could reduce CO₂ emissions while enhancing iron oxidation efficiency. Full article

Faced with the depletion of fossil resources and the need to promote a circular economy, lignocellulosic biomass represents a solution for energy transition and bioeconomy. However, wood sawdust, which contains bioactive compounds (secondary metabolites), is often burned in the open by many sawmills. This study aims to valorize Framiré wood sawdust by extracting its secondary metabolites through maceration and infusion, then converting the depleted residue into combustible briquettes. The yellowness index of the extracts ranged from 73.490 ± 0.021 (maceration) to 81.720 ± 0.014 (infusion). The total phenolic content varied from 0.097 ± 0.001 to 0.63 ± 0.049 gGAE/100 g dry matter for maceration and infusion, respectively. The extraction of bioactive compounds did not significantly affect the energy or mechanical properties of the fuels. Their higher heating value ranged from 26,153 ± 92 to 26,201 ± 90 kJ/kg for fuels with and without secondary metabolites, respectively. The Shock Resistance Index ranged from 139.33 ± 7.51% (without metabolites) to 153.00 ± 5.20% (with metabolites). A significant difference was observed in the specific consumption of the fuels, decreasing from 1.400 ± 0.100 to 0.861 ± 0.001 kg/L for fuels without and with secondary metabolites, respectively. These results open promising prospects, particularly for the use of Framiré extracts to develop flame-retardant products for wood and its derivatives. Full article

This study examines the high-temperature degradation of Hastelloy C276, a corrosion-resistant nickel-based alloy, during exposure to combustion products generated by methane and 99% cracked ammonia. Using a high-pressure optical combustor (HPOC) at 4 bar and exhaust temperatures of 815–860 °C, standard tensile specimens were exposed for five hours to fully developed post-flame exhaust gases, simulating real industrial turbine or burner conditions. The surfaces and subsurface regions of the samples were analysed using scanning electron microscopy (SEM; Zeiss Sigma HD FEG-SEM, Carl Zeiss, Oberkochen, Germany) and energy-dispersive X-ray spectroscopy (EDX; Oxford Instruments X-MaxN detectors, Oxford Instruments, Abingdon, United Kingdom), while mechanical properties were evaluated by tensile testing, and the gas-phase compositions were tracked in detail for each fuel blend. Results show that exposure to methane causes moderate oxidation and some grain boundary carburisation, with localised carbon enrichment detected by high-resolution EDX mapping. In contrast, 99% cracked ammonia resulted in much more aggressive selective oxidation, as evidenced by extensive surface roughening, significant chromium depletion, and higher oxygen incorporation, correlating with increased NO_x in the exhaust gas. Tensile testing reveals that methane exposure causes severe embrittlement (yield strength +41%, elongation −53%) through grain boundary carbide precipitation, while cracked ammonia exposure results in moderate degradation (yield strength +4%, elongation −24%) with fully preserved ultimate tensile strength (870 MPa), despite more aggressive surface oxidation. These counterintuitive findings demonstrate that grain boundary integrity is more critical than surface condition for mechanical reliability. These findings underscore the importance of evaluating material compatibility in low-carbon and hydrogen/ammonia-fuelled combustion systems and establish critical microstructural benchmarks for the anticipated mechanical testing in future work. Full article

Ammonia is considered as a promising hydrogen carrier and a carbon-free fuel. Methods for improving ammonia combustion characteristics often involve its co-firing with more reactive fuels (natural gas, biofuels, etc.). Among the natural gas components, ethane is second most abundant. Therefore, the development of detailed chemical–kinetic mechanisms that accurately consider the interactions between ammonia and each component of natural gas is very important. Such mechanisms must be based on experimental data obtained under a wide range of conditions. In this work, NH₃/C₂H₆/O₂/Ar blends were studied in JSR (φ = 0.5–2.0, p = 1 atm, τ = 1 s, T = 800–1300 K) and in a shock tube (p = 7.3–8.6 atm, T = 1260–1590 K). Additionally, the structure of premixed flames was investigated (φ = 0.8–1.2, p = 1–5 atm). Eleven recently published detailed chemical–kinetic mechanisms were tested. The model Shrestha-2025 was updated to achieve better agreement with the entire set of experimental data. The effect of p and φ on intermediate species concentration was analyzed. Ammonia and ethane consumption pathways were also examined. Full article

Accurately predicting pollutant emission factors (EFs) from woody biomass fuels remains challenging because small-scale combustion tests are fuel-specific, time-consuming, and highly sensitive to operating conditions. This study combines controlled laboratory combustion experiments with a physics-informed artificial neural network (ANN–PINN) to estimate the emission factors of particulate matter (${\mathrm{EF}}_{PM}$), carbon monoxide (${\mathrm{EF}}_{CO}$), and nitrogen oxides (${\mathrm{EF}}_{NOx}$) using only laboratory-scale fuel characterization. Three pelletized woody biomass, Pinus radiata, Acacia dealbata, and Nothofagus obliqua, were analyzed through ultimate and proximate composition, lignin content, and TGA-derived parameters and tested in a residential pellet stove under identical control setpoints, resulting in a narrow and well-defined operating regime. A medium-depth ANN–PINN was constructed by integrating mechanistic constraints, monotonicity based on known emission trends and a weak carbon balance penalty, into a feed-forward neural network trained and evaluated using Leave-One-Out Cross-Validation. The model accurately reproduced the experimental behavior of ${\mathrm{EF}}_{CO}$ and captured structured variability in ${\mathrm{EF}}_{PM}$, while the limited nitrogen variability of the fuels restricted generalization for ${\mathrm{EF}}_{NOx}$. Sensitivities derived via automatic differentiation revealed physically coherent relationships, demonstrating that PM emissions depend jointly on fuel chemistry and aero-thermal conditions, CO emissions are dominated by mixing and temperature, and ${\mathrm{NO}}_x$ formation is primarily governed by fuel-bound nitrogen. When applied to external biomass fuels characterized independently in the literature, the ANN–PINN produced physically plausible predictions, highlighting its potential as a rapid, low-cost screening tool for assessing new biomass feedstocks and supporting cleaner residential heating technologies. The integrated experimental–PINN framework provides a physically consistent and data-efficient alternative to classical empirical correlations and purely data-driven ANN models. Full article

Blasting operations associated with in-pit ramp construction in open-pit mines generate gaseous emissions originating from both explosive detonation and diesel-powered drilling and loading equipment. The research object of this study is the ramp construction process in an operating open-pit quarry, and the objective is to comparatively evaluate gaseous emissions across alternative blasting scenarios to support emission-aware operational decision-making. Five realistic blasting scenarios are assessed using a combined methodology that integrates laboratory fume index data for ANFO, emulsion explosives, and dynamite with diesel-emission estimates derived from non-road mobile machinery inventory factors. Laboratory detonation tests provide standardized upper-bound emission potentials for CO_x and NO_x, while drilling and loading emissions are quantified using a fuel-based inventory approach. The results show that the dominant contribution to total mass emissions arises from diesel combustion during drilling and loading, consistent with studies on real-world non-road mobile machinery inventory factors. Detonation fumes, although chemically concentrated and relevant for short-term exposure risk, represent a smaller share of the mass-based emission budget. Among the explosive types, bulk emulsions consistently exhibit lower toxic-gas emission indices than ANFO, attributable to their more uniform microstructure and a moderated reaction temperature. Dynamite demonstrates the lowest fume potential but is operationally less scalable for large open-pit patterns due to manual loading. Uncertainty analysis indicates that both laboratory-derived fume indices and diesel emission factors introduce systematic variability: laboratory tests tend to overestimate detonation fumes, while inventory-based diesel estimates may underestimate real-world NO_x and particulate emissions. Notwithstanding these limitations, the scenario-based framework developed here provides a robust basis for comparative evaluation of blasting strategies during ramp construction. The findings support increased use of emulsion explosives and emphasize the importance of moisture management, field-integrated gas monitoring, and improved characterization of diesel-equipment duty cycles. Full article

In this present study, sodium- and strontium-modified bismuth titanate—Bi_0.5Na_0.5TiO₃ (BNT) and Bi_0.5Sr_0.5TiO₃ (BST)—were synthesized using the auto-combustion technique with citric acid (C₆H₈O₇) and glycine (C₂H₅NO₂) as fuels in an optimized ratio of 1.5:1. The resulting powders were characterized using X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy, UV–Visible diffuse reflectance spectroscopy (DRS), and Fourier-transform infrared (FT-IR) spectroscopy. The electrical behavior of the samples was studied using an LCR meter. XRD analysis confirmed the formation of a single-phase perovskite structure with average crystallite sizes of 18.60 nm for BNT and 22.03 nm for BST, attributed to the difference in ionic radii between Na⁺ and Sr²⁺. An increase in crystallite size was accompanied by a corresponding increase in lattice parameters and unit-cell volume. The Williamson–Hall analysis further validated the strain-size contributions. EDX (Energy-Dispersive X-ray analysis) results confirmed successful incorporation of Na⁺ and Sr²⁺ without detectable impurity phases. Optical studies revealed distinct absorption peaks at 341 nm for BNT and 374 nm for BST, and the optical bandgap (E_g), calculated using Tauc’s relation, was found to be 2.6 eV and 2.0 eV, respectively. FT-IR spectra exhibited characteristic Ti-O vibrational bands in the range of 420–720 cm⁻¹, consistent with the perovskite structure. For electrical characterization, the powders were pelletized under 3-ton pressure and sintered at 1000 °C for 3 h. The dielectric constant (ε_r), dielectric loss (tan δ), and ac conductivity (σ) of both samples increased with frequency. The combined structural, optical, and electrical results indicate that the optimized compositions of BNT and BST possess properties suitable for use in capacitors and other energy-storage applications. Full article

Nitramines are nitrogen-containing organic compounds with the formula R¹R²N–NO₂. They are well-known as explosives and have been produced industrially for more than a century. A few nitramine-containing natural products have also been identified in recent years. Nitramines have also found their way into specific synthetic procedures, usually as intermediates, and for the last decades, the implementation of amine-based carbon capture and storage (CCS) technologies to mitigate CO₂ emissions from fossil fuel combustion is of particular concern since small amounts are produced. Both environmental and health implications are of particular interest, and little is known today. The need for efficient and safe synthetic procedures is, therefore, vital for further research in the field. The present review gives a detailed summary of published methods and research post-millennium. Many new as well as well-established methods are presented. Representative examples with basic conditions and yields are given. Finally, indications for future research are discussed. Full article