Search Results (65)

The global effort to mitigate hazardous particulate matter (PM) emissions from diesel engines relies significantly on advances in separations technologies. The diesel particulate filter (DPF) is a critical component designed to trap soot and ash from diesel engine exhaust, ensuring cleaner emissions and compliance with environmental regulations. In the current paper, a gas-particle two-phase flow model in the microchannels of a DPF is developed. A novel statistical approach based on probability sampling is proposed aimed at generating a particle ensemble that adheres to the real-world soot particle size distribution (PSD). The Eulerian-Lagrangian approach is employed to model the soot-laden gas flow, where the gas phase flow field is solved in the Eulerian framework, while the particle phase motion is tracked in the Lagrangian framework. The results demonstrate that the through-wall velocity plays a predominant role in the overall deposition behavior of the mixed-sized particle group. Increasing upstream velocity shifts initial particle deposition positions further from the channel inlet and enhances mass accumulation at the channel’s terminal section. Reduced filtration wall permeability promotes the uniformity of soot deposition along the channel. A permeability of 5 × 10⁻¹³ m² is identified as the critical threshold, below which the soot deposition distribution approaches near-complete uniformity. Full article

Soot particle deposition is a common form of surface contamination in enclosed architectural environments and can significantly alter the optical appearance of painted surfaces. In the Zhaomiao temple halls of Inner Mongolia, long-term exposure to soot generated by butter lamps and incense burning has led to pronounced color darkening of mural pigments. To clarify the mechanisms by which soot deposition affects pigment optical behavior, this study investigates the surface deposition-induced color degradation of mineral pigment coatings, using Zhaomiao temple murals as a representative application context. Thirty-six typical mineral pigments were prepared as standardized coating specimens, and controlled soot deposition experiments were conducted to simulate progressive particulate accumulation on pigment surfaces. Variations in Commission Internationale de l’Éclairage (CIE) XYZ tristimulus values, luminance, and color difference (ΔE) were quantitatively analyzed under different soot-loading conditions. The results show systematic luminance attenuation and chromatic compression with increasing soot deposition, indicating that optical degradation is primarily governed by surface absorption and scattering effects introduced by carbonaceous particles. These results establish a quantitative framework based on measurable optical parameters—rather than a single absolute value—for evaluating particulate-induced optical degradation of pigment coatings. This study provides a quantitative basis for evaluating particulate-induced optical degradation of pigment coatings and supports surface condition assessment and digital reconstruction of soot-contaminated painted surfaces in architectural contexts such as the Zhaomiao temples. Full article

This paper investigates the flame behavior and smoke pattern characteristics of lithium-ion battery (LIB) fires using an integrated experimental and numerical simulation approach. Based on fire dynamics theory, a jet flame model for LIB thermal runaway (TR) is developed to analyze the flame height and dynamic characteristics. The results reveal two distinct regimes in LIB jet flames: momentum-controlled dominance in the early TR stage (lasting approximately 3 s) and buoyancy-controlled dominance in subsequent combustion. The jet flame shifts from a momentum-dominated regime (Fr > 5) to a buoyancy-dominated plume (Fr < 5) as the vent velocity decays below 12 m/s. The simulated flame heights align with experimental measurements and the Delichatsios model, validating the numerical approach. Furthermore, the distribution of flame components (e.g., H₂, CO, CO₂, CH₄, C₂H₄) is analyzed, highlighting the influence of multi-component gases on combustion heterogeneity. Smoke pattern analysis demonstrates that soot deposition varies significantly between momentum- and buoyancy-controlled stages, with the former producing darker, concentrated deposits and the latter yielding wider, lighter patterns. These findings provide a theoretical basis for forensic fire investigation (accident reconstruction) and targeted suppression strategies for different combustion stages. Full article

The gliding arc plasma technique (glidarc) was used for the precipitation and deposition of Mn or Fe oxides on zirconia fibers. Two types of fibers were used: commercial (Fib Zr(C)) and biomorphic (Fib Zr(B)) ZrO₂ fibers, the latter produced using cotton as a biotemplate. Both series of supported catalysts were characterized physicochemically and morphologically. Scanning Electron Microscopy (SEM) analyses showed that Fib Zr(B) largely retained the morphology of cotton. Fib Zr(B) presented the tetragonal phase (t-ZrO₂), while Fib Zr(C) exhibited the monoclinic phase (m-ZrO₂). Using X-ray Diffraction (XRD), the cryptomelane phase (K_xMn₈O₁₆) was identified only for Mn-Fib Zr(B). In the case of Fe-supported samples, the α-Fe₂O₃ phase appeared clearly in both biomorphic and commercial fibers. SEM and Transmission Electron Microscopy (TEM) images revealed that the precipitated iron oxides appeared to be better distributed than the manganese oxides, covering the outer surface of the fibrous supports more homogeneously. X-ray Photoelectron Spectroscopy (XPS) confirmed that Mn has an average oxidation state between 3+ and 4+, consistent with the cryptomelane phase detected by XRD. The synthesized supported systems were tested as catalysts in soot and CO oxidation, with the Mn-supported fibers proving to be more active than their Fe-containing counterparts in both reactions. Full article

This study primarily focuses on the development and optimization of a high-efficiency catalyst for biodiesel production. Potassium carbonate-supported solid catalysts were synthesized using soot as the support material via an equal-volume impregnation method. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses confirmed the successful deposition of potassium carbonate onto the soot surface, resulting in uniformly dispersed spherical nanoparticles on the catalyst. The catalytic performance was evaluated through single-factor experiments, assessing the effects of catalyst loading, alcohol-to-oil molar ratio, reaction temperature, and reaction time on the transesterification reaction. The maximum biodiesel yield obtained from the Single-factor experiments was 95.29% under the optimal conditions of 6 wt% catalyst loading (relative to oil), alcohol-to-oil molar ratio of 14:1, reaction temperature of 60 °C, and reaction time of 3 h. Furthermore, response surface methodology (RSM) using a four-factor, three-level Box–Behnken design (BBD) was employed to systematically analyze the interaction effects of these variables on the biodiesel yield. The optimized conditions identified by RSM were 61.1 °C, 3.3 h, alcohol-to-oil molar ratio of 14.2:1, and 6.1 wt% catalyst dosage, yielding 95.37% biodiesel conversion. These findings demonstrate that the soot-supported potassium carbonate catalyst developed in this study exhibits excellent catalytic activity, offering a novel catalyst system for industrial biodiesel production with significant academic and practical potential. Full article

Introduction: Charred bodies represents a significant challenge for forensic pathologists due to the destructive effects of fire on human remains. Although most fire-related deaths are accidental, cases of suicide and homicide are not uncommon. Case Report: We report a peculiar case of a severely burned body discovered inside a torched vehicle. Under judicial investigation, a full autopsy was performed, including macroscopic and microscopic examination of key anatomical structures: the inspection of oral cavity revealed no soot deposits; a foreign object (a chestnut) was found anterior to the epiglottis, though not lodged within the glottis; no thermal injuries or soot were observed in the upper or lower airways. Histological analysis excluded thermal damage at the alveolar–capillary interface. Alveolar spaces appeared both hyperinflated and ectatic, likely due to septal rupture, suggestive of acute pulmonary emphysema and multiorgan congestion. Carboxyhemoglobin levels were below 5%, indicating a low level which did not support intravital inhalation of combustion gases. Based on the comprehensive medico-legal findings, the cause of death was attributed to an asphyxial mechanism. It was further demonstrated that the burning of the body occurred post-mortem. DNA extraction from two dental specimens enabled positive identification of the victim. Subsequent investigations confirmed the case to be a femicide. The perpetrator, following a domestic altercation over jealousy, suffocated his young wife and attempted to simulate accidental choking by placing a chestnut in her mouth. He then staged a vehicular fire to mimic a fatal accident. Conclusions: The case underlines that a multidisciplinary forensic approach is essential, and must integrate different methodologies and the analysis of both circumstantial evidence and scene investigation. Full article

Ash deposition on economizer heating surfaces degrades convective heat transfer efficiency and compromises boiler operational stability in coal-fired power plants. Conventional time-scheduled soot blowing strategies partially mitigate this issue but often cause excessive steam/energy consumption, conflicting with enterprise cost-saving and efficiency-enhancement goals. This study introduces an integrated framework combining real-time ash monitoring, dynamic process modeling, and predictive optimization to address these challenges. A modified soot blowing protocol was developed using combustion process parameters to quantify heating surface cleanliness via a cleanliness factor (CF) dataset. A comprehensive model of the attenuation of heat transfer efficiency was constructed by analyzing the full-cycle interaction between ash accumulation, blowing operations, and post-blowing refouling, incorporating steam consumption during blowing phases. An optimized subtraction-based mean value algorithm was applied to minimize the cumulative attenuation of heat transfer efficiency by determining optimal blowing initiation/cessation thresholds. Furthermore, a bidirectional gated recurrent unit network with quantile regression (BiGRU-QR) was implemented for probabilistic blowing time prediction, capturing data distribution characteristics and prediction uncertainties. Validation on a 300 MW supercritical boiler in Guizhou demonstrated a 3.96% energy efficiency improvement, providing a practical solution for sustainable coal-fired power generation operations. Full article

One of the key challenges in commercializing proton exchange membrane (PEM) electrolyzer technology is reducing the production costs while maintaining high efficiency and operational stability. Significant contributors to the overall cost of the device are the electrode catalysts with IrO₂ and Pt/C. Due to the high cost and limited availability of noble metals, there is growing interest in developing alternative, low-cost catalytic materials. In recent years, two-dimensional transition metal dichalcogenides (2D TMDCs), such as molybdenum disulfide (MoS₂) and rhenium disulfide (ReS₂), have attracted considerable attention due to their promising electrochemical properties for hydrogen evolution reactions (HERs). These materials exhibit unique properties, such as a high surface area or catalytic activity localized at the edges of the layered structure, which can be further enhanced through defect engineering or phase modulation. To increase the catalytically active surface area, the investigated materials were deposited on a carbon-based support—Vulcan XC-72R—selected for its high electrical conductivity and large specific surface area. This study investigated the physicochemical and electrochemical properties of six catalyst samples with varying MoS₂ and ReS₂ to carbon support ratios. Among the composites analyzed, the best sample on MoS₂ (containing the most carbon soot) and the best sample on ReS₂ (containing the least carbon soot) were selected. These were then used as cathode catalysts in an experimental PEM electrolyzer setup. The results confirmed satisfactory catalytic activity of the tested materials, indicating their potential as alternatives to conventional noble metal-based catalysts and providing a foundation for further research in this area. Full article

Submicron soot particles (with an aerodynamic diameter of less than 1.0 μm) are found to be one of the major factors resulting in global warming and health burdens. However, research on the biomonitoring of submicron soot particles and their associated sources using tree leaves has not been comprehensively conducted. This study investigated the seasonal trends of submicron soot particles on the leaves of seven tree types collected from four individual seasons across two years in Nanjing, in the Yangtze River Delta region of China, and performed source apportionment using stable carbon isotope analysis. Significant seasonal variations in submicron soot particles were observed on tree leaves of seven tree types, with average levels of 0.3 to 0.5 mg m⁻² during summer and 0.5 to 1.3 mg m⁻² during winter. The levels of submicron soot particles varied significantly across various tree types. In contrast, the levels of δ¹³C were not found to change significantly across different types. The levels of δ¹³C ranged from −26.3‰ to −20.9‰ in winter and from −24.0‰ to −18.1‰ in summer, with fossil fuels accounting for 56% and 78% of submicron soot in winter and summer on average, respectively. These results demonstrate that tree leaves can serve as a low-cost and effective biomonitoring tool for assessing the source status of submicron soot. Full article

The gas-phase delivery of lignin into the hot zone of cw-CO₂ laser-powered homogeneous pyrolysis (LPHP) reactor under “wall-less” conditions led to the breakdown of lignin macromolecules into neutral oligomers and paramagnetic fragments deposited onto the reactor cell walls. The formation of PAHs was observed during the defragmentation of lignin, accelerated with increased laser power. Remarkably, no phenolic compounds were detected among lignin fragments—intermediate radicals and neutral oligomers. It is concluded that the PAH and soot-like conjugated particulates are formed in the hot zone of the LPHP reactor, resembling the high-temperature combustion processes. The key role of the resonantly stabilized radicals in the formation of low-molecular-weight PAHs is outlined. An alternative pathway is proposed for the generation of PAH involving the formation of cyclopentadienyl radical precursors (CPDa) that are adsorbed onto or trapped within lignin macromolecules. Full article

This study investigates the composition, abundance, and vertical export of polycyclic aromatic hydrocarbons (PAHs) across three deep basins of the northeastern Mediterranean Sea (NEMS) over one year. Sinking particles were collected using sediment traps, and PAH analysis was conducted via gas chromatography-mass spectrometry. PAH fluxes varied significantly, peaking in the north Aegean Sea due to mesotrophic conditions, nutrient-rich riverine and Black Sea water inflows, and maritime anthropogenic inputs. The fluxes were highest in winter and lowest in fall. In the Cretan Sea, petrogenic sources (~70%) dominated, driven by currents, with fluxes highest in spring and lowest in winter. The Ionian Sea exhibited lower fluxes, peaking in summer and decreasing in fall. Atmospheric deposition seems to be the main transport pathway of pyrolytic PAHs in this site, while its high-water column depth (4300 m) compared to the other sites presumably enables extended degradation of organic constituents during particle settling. The positive matrix factorization (PMF) and principal component analysis (PCA) results reveal complementary insights into PAH sources and transport mechanisms. PMF analysis identified combustion (61%) and petrogenic (22%) sources, while PCA highlighted biogenic fluxes (57.7%) and atmospheric deposition. Seasonal productivity, riverine inputs, and water circulation shaped PAH variability, linking combustion-related PAHs to atmospheric soot and petrogenic PAHs to organic-rich particles. Full article

This article reports on field tests devoted to the emissions of particles from gas turbines (GT) and more particularly to the formation of soot and its suppression by fuel additives. These field tests involved four heavy-duty gas turbines used as power generators and equipped with air atomization systems. These machines were running on natural gas, No. 2 distillate oil, heavy crude oil and heavy fuel oil, respectively. The GT running on natural gas produced no soot or ash and its upstream air filtration system in fact allowed lower concentrations of exhaust particles than those found in ambient air. Soot emitted when burning the three liquid fuels (No. 2 distillate; heavy crude oil; and heavy oil) was effectively reduced using fuel additives based on iron(III), cerium(III) and cerium(IV). Cerium was found to be very effective as a soot suppressant and gave rise to two surprising effects: cerium(III) performed better than cerium(IV) and a “memory effect” was observed in the presence of heat recovery boilers due to the deposition of active cerium species. All of the reported results, both regarding natural gas emissions and soot reduction, are original. A review of the soot formation mechanisms and a detailed interpretation of the test results are provided. Full article

The ash deposition is a general problem that needs to be solved effectively for the rotary air preheater of the coal-fired boiler. Taking the rotary air preheater of a 600 MW power station as the object, the mesh model of the flue gas side of the air preheater, considering the influences of steam soot blowing, is established using the Gambit 2.4.6 software. Based on the SIMPLE algorithm, the velocity field and the temperature field in the air preheater under varied working conditions are simulated using the software of Ansys Fluent 2021R1, and the influences of the boiler load, the operation parameters of the steam soot blower, and the running and outage of the soot blower on the flue gas velocity distribution in the depth direction of the corrugated plates, the soot-blowing coverage area, the inlet flue gas velocity, and the inlet flue gas temperature of the corrugated plates are analyzed. Under the base working condition, the flue gas velocity on the axis of the steam nozzle first decreases rapidly with increasing the corrugated plate depth (Z < 1.0 m), and then it decreases slowly with an almost equal slope. The longitudinal flue gas velocity has a positive correlation with the boiler load. The longitudinal flue gas velocity obviously decreases when the boiler load is decreased, and its reduction increases as the corrugated plate depth increases. It is one reason that the ash deposition is prone to occur on the cold end surface of corrugated plates under the condition of low boiler load. The longitudinal flue gas velocity increases with the soot-blowing steam velocity increasing when the corrugated plate depth is less than 1.5 m, but after that, it is almost not affected by the change in soot-blowing steam velocity. The soot-blowing coverage area has a negative correlation with the boiler load but a slight positive correlation with the steam velocity of the soot blower on the whole. The inlet flue gas velocity of the corrugated plates has a positive correlation with the boiler load and the inlet steam velocity of the soot blower. The average inlet flue gas velocity decreases by 21.7% when the boiler load is reduced by 50%. For every 5 m/s variation in the inlet steam velocity, the inlet flue gas velocity changes by about 10–14% whether the steam soot blower is put into operation or not, which has an obvious effect on the inlet gas velocity of the corrugated plates. The inlet flue gas temperature of the corrugated plates is, respectively, positively correlated with the boiler load and the inlet steam temperature of the soot blower. When the boiler load is reduced from 100% BMCR to 50% BMCR, the average inlet flue gas temperature of the corrugated plates is reduced by 44.2 K; however, when the soot-blowing steam temperature varies by 20 K, the average inlet flue gas temperature of the corrugated plates varies by only about 1.8 K. It means that it is difficult to enhance the cold end flue gas temperature of the corrugated plates only by raising the soot-blowing steam temperature at low boiler load. Adding a soot blower using high-temperature steam or hot air at the outlet of the corrugated plates may be an option to solve the ash deposition of the corrugated plates. Full article

This study investigates the thermal–hydraulic behavior and deposition characteristics of a shell and tube exhaust heat exchanger using a CFD-based predictive model of soot deposition. Firstly, considering the influences of thermophoretic, wall shear stress, and other deposition and removal mechanisms, a predictive model is developed for long-term performance of heat exchangers under soot deposition. Then, the variations in exhaust heat exchanger performance during a 4 h deposition period are simulated based on the model. Subsequently, the variation of deposition distribution and different deposition velocities are also evaluated. Finally, an analysis of the long-term performance of the exhaust heat exchanger under varying gas velocities and temperature gradients is conducted, revealing the performance variations under all engine-operating conditions. Results show that the deterioration in normalized relative ${j/f}^{1/2}$ varies from 5.26% to 24.91% under different work conditions, and the exhaust heat exchanger with high gas velocity and low temperature gradient exhibits optimal long-term performance. Full article

Fire deaths present several diagnostic challenges for the forensic examiner, the most significant of which is the identification of the cause of death and the evaluation of the morphological consequences of heat injuries in the ante-mortem and post-mortem periods. Here, we describe the case of two young lovers found dead inside a travelling carousel destroyed by a fire. Circumstantial evidence of disputes between families running the town fair raised the suspicion of intentional arson. Comparative analysis of crime scene investigation, radiological, autoptic, histological, and toxicological findings revealed signs of vitality (i.e., presence of soot deposits inside the respiratory and digestive tracts, heat damage to the respiratory mucosa) and identified fatal asphyxia from haemorrhagic pulmonary oedema as the cause of death. Since the experimental burning of plastic samples collected from a similar carousel demonstrated the significant production of phosgene, the death of the two lovers was attributed to the probable inhalation of this gas. The case presented here underlines the importance of a multidisciplinary approach of any fire-related death, providing an insight into circumstantial and forensic (autopsy, toxicological, and immunohistopathological) elements useful in raising suspicion of possible toxic gas inhalation. In the presence of high levels of PVC materials at the fire scene and pulmonary oedema at the autopsy, with no alternative causes of death, the forensic pathologist must suspect a fatal exposure to phosgene. Full article