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To control acid mine drainage (AMD) from the source, a new environmentally and green passivator (biochar) has been introduced to passivate pyrite. To reduce the difficulty of biochar preparation and cost, and improve its production scale, in-situ pyrolysis of applewood by smoldering to produce biochar. Here, particle size, moisture content and gas flow rate were selected to prepare biochar by smoldering through orthogonal combination, and the pyrite was passivated with different conditions and biochar concentrations (2 g/L, 3 g/L, 4 g/L). The results revealed that when the particle size is 200 mm×200 mm×20 mm, the water content is 20–30%, and the gas flow rate is 0.4 L/m3, the biochar yield is the highest. Biochar promotes the formation of passivating layer (jarosite), inhibits the release of metal ions. Increasing biochar concentration can promote the formation of jarosite and enhance the passivation effect on pyrite. [ABSTRACT FROM AUTHOR]

Enhancing soil organic matter characteristics, ameliorating physical structure, mitigating heavy metal toxicity, and hastening mineral weathering processes are crucial approaches to accomplish the transition of tailings substrate to a soil-like substrate. The incorporation of biomass co-pyrolysis and plant colonization has been established to be a significant factor in soil substrate formation and soil pollutant remediation. Despite this, there is presently an absence of research efforts aimed at synergistically utilizing these two technologies to expedite the process of mining tailings soil substrate formation. The current study aimed to investigate the underlying mechanism of geochemical changes and rapid mineral weathering during the process of transforming tailings substrate into a soil-like substrate, under the combined effects of biomass co-smoldering pyrolysis and plant colonization. The findings of this study suggest that the incorporation of smoldering pyrolysis and plant colonization induces a high-temperature effect and biological effects, which enhance the physical and chemical properties of tailings, while simultaneously accelerating the rate of mineral weathering. Notable improvements include the amelioration of extreme pH levels, nutrient enrichment, the formation of aggregates, and an increase in enzyme activity, all of which collectively demonstrate the successful attainment of tailings substrate reconstruction. Evidence of the accelerated weathering was verified by phase and surface morphology analysis using X-ray diffraction and scanning electron microscopy. Discovered corrosion and fragmentation on the surface of minerals. The weathering resulted in corrosion and fragmentation of the surface of the treated mineral. This study confirms that co-smoldering pyrolysis of biomass, combined with plant colonization, can effectively promote the transformation of tailings into soil-like substrates. This method has can effectively address the key challenges that have previously hindered sustainable development of the mining industry and provides a novel approach for ecological restoration of tailings deposits. [Display omitted] [ABSTRACT FROM AUTHOR]

Autoignition and smoldering of coal dust have gained great safety concern in both industry and mining due to their high susceptibility to heating. To better understand their controlling mechanism, autoignition and smoldering of bituminous coal particles (1-mm diameter) and coal powders (0.1-mm diameter) in the form of bulk layer heated by 4–45 kW m−2 thermal radiation levels were systematically studied. The results showed that the critical heat flux was between 4 and 5 kW m−2 for both samples. Under 5 kW m−2, no morphology change was detected on surface, but internal ignition and smoldering occurred. Partial oxidation and intense glowing ignition were observed under heat fluxes of 10 and 15–45 kW m−2, respectively. The average glowing temperature was 782.4 ± 19.6 K, while the maximum temperature during smoldering changed in 976–1206 K. Smoldering spread rate of powder sample was larger than that of particle sample due to emerged cracks during heating and larger specific surface area, and both spread rates linearly depended on heat flux. The linear dependency of ignition time to the power of − 0.5 on heat flux in classical ignition theory was found still valid for glowing ignition of both samples, and apparent thermal inertia and critical heat fluxes were quantitatively estimated. In all smoldering tests, mass loss rates exhibited a bimodal feature, with first peak charactering moisture evaporation, while the second peak indicating coal-oxygen reaction. Under 35 and 45 kW m−2 heat fluxes, a unique faint blue flame appeared which depended more on surface temperature than on mass flux of pyrolyzates. This contribution may deliver useful reference for evaluation of coal fire risk and help mitigate hazard of smoldering in practical applications. [ABSTRACT FROM AUTHOR]

Smouldering has recently been developed as a cost effective and energy efficient technology for challenging wastes. These systems are often used to eliminate environmental liabilities, and only minimal work has explored their use for generating useful by-products. This study addressed this research gap and demonstrated that applied smouldering systems can be tuned to favour hydrogen production. Calcium oxide and steam were added to the smouldering system, which completely treated woody biomass and coal tar, while producing hydrogen. The maximum hydrogen concentration achieved in the smouldering system was 33.7%, resulting in a net energy positive syngas. Results suggest that both heterogenous gasification and the water gas shift were key mechanisms behind hydrogen formation. These results indicate that smouldering systems can be used as a new method to sustainably produce hydrogen-rich syngas from challenging wastes. [Display omitted] • Experimental study produced up to 34% H 2 from smouldering combustion. • Experiments used different fuels, porous media, steam, and CaO amendments. • New methodology to drive net-energy-positive H 2 -rich syngas from smouldering. • Optimum steam/carbon ratio was found to be between 2 and 3 to maximize H 2 yield. • Heterogenous gasification and the water gas shift were key H 2 production mechanisms. [ABSTRACT FROM AUTHOR]

Loose-fill thermal composite insulation produced from surface-modified wood scobs has been explored as a potential fire-resistant material for building envelopes. This work involves fire resistance behavior comparisons between four coating systems consisting of liquid glass, liquid glass-tung oil, liquid glass-expandable graphite, and liquid glass-tung oil-expandable graphite. The techniques of thermogravimetric and differential thermogravimetric analyses, gross heat combustion via a calorimetric bomb, cone calorimetry, SEM imaging of char residues, and energy dispersive spectrometry for elemental analysis, as well as propensity to undergo continuous smoldering, were implemented. The coating technique resulted in greater thermal stability at a higher temperature range (500–650 °C) of the resulting loose-fill thermal composite insulation, reduced flame-damaged area heights after the exposure of samples at 45° for 15 s and 30 s, with a maximum of 49% decreased gross heat combustion, reduced heat release and total smoke release rates, improved char residue layer formation during combustion and changed smoldering behavior due to the formation of homogeneous and dense carbon layers. The results showed that the highest positive impact was obtained using the liquid glass and liquid glass-expandable graphite system because of the ability of the liquid glass to cover the wood scob particle surface and form a stable and strong expanding carbon layer. [ABSTRACT FROM AUTHOR]

Inhalation exposure to plastic incineration emissions (PIEs) is a problem of increasing human relevance, as plastic production and waste creation have drastically increased since mainstream integration during the 20th century. We investigated the effects of PIEs on human nasal epithelial cells (HNECs) to understand if such exposures cause damage and dysfunction to respiratory epithelia. Primary HNECs from male and female donors were cultured at air–liquid interface (ALI), and 16HBE cells were cultured on coverslips. Smoke condensates were generated from incineration of plastic at flaming (640°C) and smoldering (500°C) temperatures, and cells were subsequently exposed to these materials at 5–50 μg/cm2 concentrations. HNECs were assessed for mitochondrial dysfunction and 16HBE cells for glutathione oxidation in real-time analyses. HNEC culture supernatants and total RNA were collected at 4-h postexposure for cytokine and gene expression analysis, and results show that PIEs can acutely induce inflammation, oxidative stress, and mitochondrial dysfunction in HNECs, and that incineration temperature modifies biological responses. Specifically, condensates from flaming and smoldering PIEs significantly increased HNEC secretion of cytokines IL-8, IL-1β, and IL-13, as well as expression of xenobiotic metabolism pathways and genes such as CYP1A1 and CYP1B1 at 5 and 20 μg/cm2 concentrations. Only 50 μg/cm2 flaming PIEs significantly increased glutathione oxidation in 16HBEs, and decreased respiration and ATP production in HNEC mitochondria. Impact Statement: Our data reveal the impact of incineration temperatures on biological outcomes associated with PIE exposures, emphasizing the importance of temperature as a factor when evaluating respiratory disease associated with PIEs exposure. [ABSTRACT FROM AUTHOR]

Developing environmentally friendly building materials with low environmental impacts is receiving more attention nowadays to face the global challenges of climate change; building insulation materials made from agricultural waste can be used for their low environmental impact and to generate responsible supplies that utilize natural resources adequately. The study aims to assess a panel made from rice husk using the pulping method. An experimental design established the proportion of rice husk, the percentage of additive (NaOH concentration), boiling time and blending time. Taguchi's method was applied to investigate the effect on density and thermal conductivity; the final panel with optimum conditions was morphologically analyzed using scanning electron microscopy (SEM); the thermal behavior was studied by thermogravimetric analysis (TGA); fire reaction and smoldering behavior were analyzed; and characterization in water absorption and acoustic absorption performances were established. The results show thermal conductivity values between 0.037 and 0.042 W/mK, a smoldering velocity of 3.40 mm/min, and a good acoustic absorption coefficient in octave frequency bands between 125 Hz and 4 kHz greater than 0.7. These characteristics are competitive with other insulating bio-based materials available on the market. This study employed chemicals utilized by other biomaterials for the pulping process and in flame retardants. However, it is important to investigate natural treatments or those with a diminished environmental impact. [ABSTRACT FROM AUTHOR]

Understanding how the size of fuel particles influences the initiation and spread of smoldering fronts is an important consideration in the spread of wildfires. Natural fuels often consist of layers of organic materials of varying sizes, yet the influence of the size of the particle on the burning behavior is not well understood. Changes in the size of particles can influence how readily oxygen transports to the reaction zone, how particles heat and burn, and how much heat transfers between particles. With this background, the objective of this study was to identify sensitivities of smoldering behavior to the size of particles and elucidate changes in heat transfer and oxygen transport in causing observed sensitivities. To achieve this objective, experiments were conducted where fuel beds of granulated Douglas-fir wood pellets of varying particle sizes were put in contact with an ignition source. The propensity to sustain horizontal and downward smoldering combustion and the resulting propagation rates and temperatures were quantified. Tests of homogenous and mixed particle sizes were investigated. In general, particle sizes with characteristic diameters (d) > 1.27 mm did not transition to self-sustained smoldering, while particle sizes with d < 1.27 mm transitioned to self-sustained smoldering, irrespective of the ignition temperature. Increasing the size of particles reduced the spread rate and surface temperature, despite having lower overall densities. Larger particles could sustain smoldering if sufficient concentrations of smaller particles were present in the pores. Fuel beds with increased porosity and permeability (i.e., larger particles) had reduced propensity to sustain smoldering showing that how readily oxygen can be transported to the reaction zone is not a limiting condition for particles of this size when burns are near the surface. A simplified heat transfer analysis was conducted to consider the contributions of conduction, convection, and radiation in transferring heat between particles. Increasing particle size decreases the heat transfer rate between particles as a result of greater heat loss due to convection. Additionally, smaller particles have similar Biot numbers resulting in increased heating rate, ignitability and spread rates. The results from this work provide insights into the important influences that the size of the fuel particles can play in smoldering near surfaces (i.e., up to 8 cm evaluated). [ABSTRACT FROM AUTHOR]

Large and downed woody fuels remaining behind a wildfire's flame front tend to burn in a smoldering regime, producing large quantities of toxic gases and particulate emissions, which deteriorates air quality and compromises human health. Smoldering burning rates are affected by fuel type and size, the amount of oxygen reaching the surface, and heat losses to the surroundings. An external wind has the dual effects of bringing fresh oxidizer to the fuel surface and porous interior, while at the same time enhancing convective cooling. In this work, a series of experiments were conducted on single and adjacent poplar dowels to investigate the effect of fuel geometry and wind speed on smoldering of woody fuels, including its burning rate and combustion products. Dowels had variable thickness (19.1 and 25.4 mm), aspect ratios, and arrangement (number of dowels and spacing between them). Using measurement of mass loss, CO, and HC production as indicators of the smoldering intensity, the results indicate that the arrangement of smoldering objects significantly affects burning rates and emissions. Specifically, spacings of 1/8 and 1/4 of the dowel thickness enhanced the smoldering process. The smoldering intensity was also enhanced by increased external wind (ranging between 0.3 m/s and 1.5 m/s), but its effect was dependent upon the spacing between the dowels. The convective losses associated with the spacing were further investigated with a simplified computational model. The simulations show that the wind significantly increases convective losses from the smoldering surfaces, which in turn may offset the increase in smoldering intensity related to the higher oxygen flux at higher wind speeds. [ABSTRACT FROM AUTHOR]

We present a mathematical model for the slow combustion (smoldering) of a two-dimensional sheet of paper. We describe the evolution of the char region, and we investigate the effects of an orthogonal air flow on the shape of the combustion front. The mathematical formulation consists in a set of two nonlinear PDEs for the temperature and the oxygen concentrations coupled with one ODE for the cellulose concentration. The (dimensionless) problem is solved numerically by means of a spectral collocation scheme based on Chebyshev polynomials. Our results show that the Péclet and the Lewis number strongly influence the shape of the ignition front and that the advancement of the combustion front does not occur if advection and diffusion are neglected (zero Péclet and Lewis numbers). In particular we observe that the burning region and the ignition front are strongly influenced by the velocity of the airflow and by the mass and heat transport phenomena due to diffusion and advection. We shall see that the increasing of the ratio between the convective and diffusive characteristic times (Péclet number) and the decreasing of the ratio between the mass and heat diffusive characteristic times (Lewis number) have a "flattening effect" on the combustion front. [ABSTRACT FROM AUTHOR]

Developing environmentally friendly building materials with low environmental impacts is receiving more attention nowadays to face the global challenges of climate change; building insulation materials made from agricultural waste can be used for their low environmental impact and to generate responsible supplies that utilize natural resources adequately. The study aims to assess a panel made from rice husk using the pulping method. An experimental design established the proportion of rice husk, the percentage of additive (NaOH concentration), boiling time and blending time. Taguchi’s method was applied to investigate the effect on density and thermal conductivity; the final panel with optimum conditions was morphologically analyzed using scanning electron microscopy (SEM); the thermal behavior was studied by thermogravimetric analysis (TGA); fire reaction and smoldering behavior were analyzed; and characterization in water absorption and acoustic absorption performances were established. The results show thermal conductivity values between 0.037 and 0.042 W/mK, a smoldering velocity of 3.40 mm/min, and a good acoustic absorption coefficient in octave frequency bands between 125 Hz and 4 kHz greater than 0.7. These characteristics are competitive with other insulating bio-based materials available on the market. This study employed chemicals utilized by other biomaterials for the pulping process and in flame retardants. However, it is important to investigate natural treatments or those with a diminished environmental impact.

The current study presents a series of experiments investigating the smoldering behavior of woody fuel arrays at various porosities under the influence of wind. Wildland fuels are simulated using wooden cribs burned inside a bench scale wind tunnel. Smoldering behavior was characterized using measurements of both mass loss and emissions. Results showed that the mean burning rate increased with wind speed for all cases. In high porosity cases, increases in burning rate between 18% and 54% were observed as wind speed increased. For low porosity cases an increase of about 170% in burning rate was observed between 0.5 and 0.75 m/s. The ratio of CO/CO2 emissions decreased with wind speed. Thus, wind likely served to promote smoldering combustion as indicated by the decrease of CO/CO2 which is a marker of combustion efficiency. A theoretical analysis was conducted to assess the exponential decay behavior in the time-resolved mass loss data. Mass and heat transfer models were applied to assess whether oxygen supply or heat losses can solely explain the observed exponential decay. The analysis showed that neither mass transfer nor heat transfer alone can explain the exponential decay, but likely a combination thereof is needed. [ABSTRACT FROM AUTHOR]

The goal of this work is to develop a material model for Norway spruce and Scots pine woods for use in performance-based fire safety design to predict char front progress and heat release in burning timber. For both woods a set of two different models is estimated: one that assumes wood as a single component and another that considers the pyrolysis of wood principal components independently (single and parallel reactions models, respectively). The material models are calibrated using cone calorimeter experiments. The models are intended for a number of different fire scenarios, such as fully developed fire with only little oxygen in the compartment, or the decay period after flaming with exposed char still smoldering. For both spruce and pine, the single and parallel reactions models are able to predict the experiments in the scale of cone calorimeter with near-equal accuracy. Hence, the single reaction model emerges as the preferable level of complexity when modelling charring and heat release, avoiding the increased uncertainty associated with the additional parameters of the parallel reactions model. When scaling up to the simulations of large scale fire tests, the models can predict the char front progress, but the final temperature profile differs from the experimental. The effects of crack forming in the char layer is one of the likely causes, but its mechanisms are not sufficiently known. Therefore, we suggest a closer study on crack formation in wood under fire as future research. [ABSTRACT FROM AUTHOR]

Adult T cell leukemia/lymphoma (ATLL) is a rare, extremely aggressive malignancy with four different clinical variants, all of which are associated with human T cell lymphotropic virus type 1. Antiretrovirals have been recognized as an effective therapy after study in clinical trials around the world. However, oncologists traditionally wait for asymptomatic patients with ATLL to reach a more severe stage of disease before treatment is initiated. We describe a patient with Fitzpatrick Skin Type V who presented with asymptomatic dyschromia of her neck, breast, and jaw. Her clinical, laboratory, and histological findings were consistent with smoldering type-ATLL. We teamed up with her oncologist to successfully treat her cutaneous symptoms with interferon-alpha/zidovudine. This report demonstrates efficacy with the employment of antiretroviral therapy immediately following a diagnosis of smoldering type ATLL.

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Peat fires can persistently last for an extended period after being ignited, despite rainfall and firefighting efforts. The difficulty of peat fire suppression is mainly due to the smoldering spreading through the subsurface layer. This paper reports laboratory experiments of peat fire suppression by means of water injection directly to the subsurface hotspot. Natural peat samples (from Papua and Jambi, Indonesia) were used in this study. The experimental results show that water injection is more efficient than the water spray technique based on both suppression duration and water usage in extinguishing hotspot areas. The suppression duration of water injection is about half of those of water spray. To fully suppress the fire, Papuan peat required 4.22 ± 0.26 L of water per 1 kg of peat (L/kg-peat), while Jambi peat required 3.81 ± 0.03 L/kg-peat. This study contributes to a better understanding of the suppression dynamic of the water injection technique and proposes its implementation for early peat fire mitigation in the field.

Smoldering diverticulitis is a form of chronic uncomplicated diverticulitis with continuous non-resolving abdominal pain that commonly requires surgical intervention. In this study, we aimed to evaluate post-operative outcomes in patients undergoing colon resection for smoldering diverticular disease. We performed a single tertiary historical records review including all patients operated for diverticular disease of the sigmoid between January 2009 and January 2020. Only patients with smoldering diverticulitis were included in the final analysis. Demographic, peri-operative, and post-operative outcomes were collected from patient medical charts and analyzed. We reviewed the data of 3124 patients that were hospitalized due to diverticulitis during 2009–2020. Overall, 184 patients were operated due to diverticular disease. Of those, 18 patients (9.78%) were operated for smoldering diverticulitis. Eight (42%) patients were men; mean patient age was 62 SD 11 years. Median Charlson's comorbidity score was 1 (0–3). Ten patients were operated laparoscopically (55.56%), with a conversion rate of 40% ( n = 4 ). Three patients (16.67%) underwent primary stoma formation. Post-operative complications were seen in 6 (33%) patients with a median Clavien-Dindo score of 3 (1–4) and 2 patients underwent re-operation (11.11%). Median length of stay was 8 days (range 4–26). Five (27.78%) patients required an unplanned re-admission following their surgical procedure. Median follow-up time was 5.3 months (1–127). Thirteen (72.22%) patients were free of symptoms at the last follow-up. Quality of life questionnaire demonstrated significant improvement after surgery ( P < 0.01 ) that lasts during follow-up time ( P = 0.52 ). Length of stay was correlated with age ( P < 0.01 , Pearson's coefficient = 1) and serum white blood counts (< 0.01, 0.79). Smoldering diverticulitis is a fairly rare surgical condition with unneglectable risk for post-operative complications. However, most patients report improvement of symptoms after surgery and both short-term and long-term surveillance. [ABSTRACT FROM AUTHOR]

Summary: Obviously, the use of insulation materials from renewable resources in buildings could provide benefits regarding environmental protection and sustainable management. Nevertheless, their market share in Germany is estimated to be about 7% because of a partial lack of knowledge about their properties, and therefore, of construction certifications. This work was intended to close a knowledge gap concerning emissions during pyrolysis, smoldering, and combustion of commercial insulating materials made from wood, cellulose, meadow grass, hemp, jute, cork, and seaweed as well as polystyrene for comparison reasons. Laboratory‐scale experiments were conducted and the measurement of thermal decomposition products was done with gas chromatography combined with mass spectrometry (GC/MS). It was realized that almost all the products could be assigned to the following eight substance classes: carbohydrates, aldehydes/ketones, carbonic acids/esters, substituted phenols, furans, aliphatic hydrocarbons, substituted benzenes, and polycyclic aromatic hydrocarbons. Substance spectra were generated that showed certain conformities, especially between the insulating materials made from wood, cellulose, and meadow grass as well as hemp and jute. Comparisons of the sum of peak areas in the GC/MS‐chromatograms provided indications of the relative extent of thermal decomposition product emissions. Calculations according to (∑peak areas renewable material)/(∑peak areas polystyrene) revealed factors between 0.18 (wood, cork) and 0.028 (meadow grass). In the thermal emissions, defined hazardous substances or substance groups were frequently measured. These were included in a toxicity evaluation by which, inter alia, advantages of the natural products compared to polystyrene could be demonstrated. [ABSTRACT FROM AUTHOR]

Peat fires can persistently last for an extended period after being ignited, despite rainfall and firefighting efforts. The difficulty of peat fire suppression is mainly due to the smoldering spreading through the subsurface layer. This paper reports laboratory experiments of peat fire suppression by means of water injection directly to the subsurface hotspot. Natural peat samples (from Papua and Jambi, Indonesia) were used in this study. The experimental results show that water injection is more efficient than the water spray technique based on both suppression duration and water usage in extinguishing hotspot areas. The suppression duration of water injection is about half of those of water spray. To fully suppress the fire, Papuan peat required 4.22 ± 0.26 L of water per 1 kg of peat (L/kg-peat), while Jambi peat required 3.81 ± 0.03 L/kg-peat. This study contributes to a better understanding of the suppression dynamic of the water injection technique and proposes its implementation for early peat fire mitigation in the field. [ABSTRACT FROM AUTHOR]

Physicochemical and toxicological properties of biomass burning are of great importance for the assessment of the impacts of wildfires on the environment. However, the data on Siberian wildfires are limited. The composition of aerosols originating during Siberian biomass burning is studied in the Large Aerosol Chamber (LAC) of the Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk. In this work, we study the composition of organic compounds in Siberian pine and forest debris smoke produced during smoldering and flaming phases and aging with the use of FTIR spectroscopy, gas chromatography-mass spectrometry, and liquid chromatography. Markers which allow identifying the combustion conditions and biomass type are suggested, namely, characteristic absorption bands, ratios of carboxyl and aliphatic functionalities, and diagnostic ratios of polycyclic aromatic hydrocarbons (PAHs). Emission factors and carcinogenic risk of smoke PAHs are estimated. [ABSTRACT FROM AUTHOR]

Smoldering is a flameless combustion mode occurring on the surface of charring fuels, such as wood and cigarettes. Although the smoldering process is slow and has a low temperature compared to flaming, it is easy to be initiated by a weak heat source and persists under poor oxygen conditions. Extensive work has been done for flame extinction to develop scaling models to predict the limiting oxygen concentration (LOC), but limited work is available for the smoldering extinction. This study develops a reduced analytical model to predict the extinction limits of smoldering. The model simultaneously solves smoldering propagation rate, surface temperature, and surface oxygen mass fraction as part of the solutions. The extinction limit is determined as the critical condition where solutions satisfying all governing equations cease to exist. The model provides a qualitative description and captures the essential characteristics of a previous experiment. The smoldering rate decreases with increasing fuel diameter, and a larger-diameter fuel is easier to extinguish. The mechanisms of the extinction process are investigated, showing the dominant role of radiative heat loss in the smothering limit at low airflow velocities and convective heat loss near the blowoff limit at high airflow velocities. Further analysis of the effect of oxygen concentration shows an increasing trend of LOC with fuel diameter, and the smothering branch cannot be predicted without considering the heat loss through radiation from the solid surface. The novelty of this research is the prediction of smoldering propagation rates and extinction limits across various fuel diameters using a reduced analytical model. The model is modified to accommodate a thin fuel configuration and high airflow velocity condition, where convective heat and mass transfer play a more important role. The model's significance is that it not only provides essential insights into the mechanisms but also has the capability to simultaneously determine key parameters such as spread rate, reaction temperatures, and surface oxygen concentration as part of the solutions. Additionally, this study demonstrates the model's ability to reproduce the limit conditions, including smothering/blowoff limits and limiting oxygen concentration (LOC). [ABSTRACT FROM AUTHOR]

In firebrand deposition scenarios, there are a few possible outcomes: no ignition, smoldering, and flaming ignition. The criteria for determining smoldering or flaming ignition is generally qualitative in nature. Experiments were conducted to determine a quantitative ignition criterion. Firebrands were deposited on cellulose insulation fuel beds under an impinging air jet at two different velocities while thermocouple measurements were taken in the fuel bed and cameras recorded the tests in the visible and IR spectrum. The firebrand temperature and the temperatures within the fuel bed were insufficient to predict the ignition of the fuel bed. However, using the IR camera to monitor the growth of the reacting area in the fuel bed, a quantitative definition of ignition was found. Over the course of a test, different growth rates, representing different phases in the ignition process, were apparent in the non-dimensional reacting area. The initial phase, right after deposition, increased as 0.003 1/s, and the final phase average growth rate was 0.18 1/s. The time to the final growth rate matched well with the flaming ignition times recorded in the visible videos. The average error between the observed and predicted time to flaming ignition was 12%. This non-dimensional reacting area analysis provides a framework for determining ignition in a quantitative way. [ABSTRACT FROM AUTHOR]

Pyrolysis is a promising process for the valorization of plastic waste (PW). However, traditional pyrolysis processes have high energy consumption. On the other hand, smoldering has been proven as an effective and economic process to treat waste, becoming an attractive application for developing countries. Therefore, a reactor for PW pyrolysis driven by char smoldering was investigated in this study. A proof-of-concept was the development of a multidimensional mathematical model to verify the proposed reactor's feasibility and evaluate its performance. It was found that PW was pyrolyzed stably driven by a self-sustaining char smoldering front. The model suggested that the air inlet velocity and char concentration determined the duration of the PW pyrolysis process and tar and gas yields by regulating the front velocity and the peak temperature. The carrier gas inlet velocity controlled the tar's residence time in the PW pyrolysis chamber and further affected the tar and gas yields. • A numerical model for the smoldering-driven pyrolysis reactor was developed. • Air inlet velocity and char concentration determined the pyrolysis duration. • Carrier gas inlet velocity could regulate the tar and gas yields. [ABSTRACT FROM AUTHOR]

This article summarizes the current situation of oil pollution site repair. Extensive applications in practical engineering are in-situ repair techniques which has many advantages such as simple operation and lower environmental impact. Application of in-situ repair technology in petroleum soil pollution repair will become the core of the future research. Then some popular oil in-situ restoration technologies in recent years were introduced including in-situ thermal desorption, in situ chemical oxidation, soil vapor extraction (SVE), in situ bioventing and self-sustaining treatment for active remediation(STAR), and their global research progression also have been analyzed systematically. Overall, we proposed that STAR will be the future development direction of petroleum pollution areas management and restoration. [ABSTRACT FROM AUTHOR]

Peatland wildfire frequency and severity are increasing globally owing to climate change. The direct risk of elevated greenhouse gas emissions from peat burning receives much attention, yet the risks to vegetation composition or peat decomposition from alkaline ash inputs are poorly understood. We explored whether ash produced during smoldering increases peatland topsoil (~0-25 cm) pH through field observations and laboratory experiments. We assessed spatial patterns of smoldering and ash presence, and measured soil and ash pH after a peatland wildfire in the Netherlands. Additionally, a peat smoldering experiment was conducted to compare freshly produced ash pH with aged ash pH collected 2 months following the wildfire. Additionally, we assessed the amount of ash needed to increase soil pH. Results showed that ash inputs at the field site were insufficient to increase pH of the acidic peatland after the wildfire. Incubation experiments showed that a ≥3 cm ash layer (ash load 163 t ha-1) would be required to increase soil pH by at least 1 unit. Given that aged ash was slightly acidic and fresh ash was alkaline, leaching and neutralisation of ash after wildfire is likely, suggesting that elevated soil pH from ash input may be transient rather than long term. [ABSTRACT FROM AUTHOR]

Summary: The development of fire prevention and mitigation technologies with a benign toxicological and environmental profile has become of particular interest in the USA due to the recent adoption of state regulations that severely restrict the use of flame retardants in certain products, like residential upholstered furniture (RUF). Herein, the effectiveness of a backcoating technology in RUF is demonstrated. The backcoating is a silicone‐based elastomer, filled with vinyl‐silane modified aluminum‐hydroxide that was applied to the back side of an upholstery fabric to generate a flexible and effective fire barrier. Chair mock‐ups were assembled using either an uncoated cotton fabric (UCF) or a backcoated cotton fabric (BCF) as cover fabric. The fire performance of the chair mock‐ups incorporating the UCF and BCF was compared in an open‐burning calorimeter after exposure to either a flaming ignition source or a smoldering ignition source. In the flaming ignition tests, the chair mock‐ups with BCF showed a reduction in the peak heat release rate and the total heat released by factors of about 6 and 45, respectively, as compared to the chair mock‐ups with UCF. In the smoldering ignition tests, the chair mock‐ups with UCF showed intense smoldering, which eventually transitioned to open flaming, whereas, the BCF chair mock‐ups showed no sign of foam or fabric smoldering. The backcoating also offered a durable fire protection solution, with an abrasion resistance of BCF roughly doubled compared to UCF. Ultimately, the backcoating provided an unusual combination of smoldering and flaming ignition resistance while complying with several recently enacted or pending U.S. state regulations. [ABSTRACT FROM AUTHOR]

In order to control the extremely complex +1 030 m horizontal fourth mining fire area with a wide spread concealed smoldering state at 4238 working face of Huashan Mine, combine active fire-fighting with partition isolation and fire control as the basic idea, comprehensive fire-fighting techniques, such as remote sealing after shrinkage, inorganic material filling, liquid carbon dioxide cooling, nitrogen injection inerting, flyash slurry filling in the roadway and filling in the surrounding roadway in smoldering fire areas, have been successively adopted for treatment. The results show that the fire in 4238 working face has been extinguished, after a long time of high intensity treatment, the fire has been gradually extinguished, the concentration of carbon monoxide gas is controlled below 1×10-5, at present, the management of the fire area is at the end stage.

Pressure treated wood (PTW) and wood-plastic composite (Trex®) were exposed to glowing firebrand piles in a bench-scale wind tunnel. The air flow velocity was 0.9–2.7 m s−1, the firebrand coverage densities were 0.06 and 0.16 g cm−2, and the pile footprint was 5 × 10 cm2 with either the 10-cm or 5-cm sides perpendicular to the incident air flow. Several types of flaming ignition events were observed including flames attached to the substrate surface in front of the pile (preleading zone ignition), and flames attached to the pile that sometimes spread onto the substrate downstream of the pile (downstream ignition). The most frequent and long-lasting flaming combustion occurred in experiments performed at 2.4–2.7 m s−1 using 0.16 g cm−2 firebrand coverage density piles with 10-cm sides perpendicular to the air flow. Trex® was less prone to preleading zone ignition but was more prone to downstream ignition. Unlike Trex®, PTW exhibited a propensity for sustained smoldering for a wide range of air flows. • Several types of ignition events were observed. • Ignition probability increased with increasing air flow and firebrand coverage density. • Ignition probability increased with increasing air flow facing pile dimension. • Wood-plastic composite was more prone to flaming ignitions downstream of the pile. • Pressure treated wood was more prone to sustained smoldering. [ABSTRACT FROM AUTHOR]

Smoldering combustion during wildfires contributes significantly to emissions of pollutants, can burn for days or months, may damage roots and soil, and can transition to flaming combustion. Mitigating these hazards requires an understanding of how physical parameters control smoldering combustion, such as the chemical composition of the fuel. The main organic constituents of biomass are cellulose, hemicellulose, and lignin. Understanding how these constituents influence smoldering is an important step in further developing physics-based models and developing understanding that applies across multiple fuel sources. Previous experimental studies have investigated how varying the amount of cellulose and hemicellulose in fuel influences smoldering behavior, but have not considered the impacts of varying the lignin content. The objective of this study was to identify the influence of lignin on smoldering behavior. This objective was achieved by experimentally and numerically studying the smoldering behavior of various concentrations of lignin in mixtures of cellulose and hemicellulose. These were tested at densities of 200 and 300 kg/m3. An infrared camera and thermocouples were used to determine the propagation of the smoldering front in the horizontal and vertical directions, respectively. A one-dimensional reactive porous media model with global chemistry was used to simulate downward smoldering propagation. The horizontal and downward smoldering propagation velocities decrease when more lignin is present due to the slower pyrolysis rates and higher activation energy of lignin. Additionally, results from simulations match this trend for downward propagation. At higher lignin contents, the effect of the mass percentage of cellulose and hemicellulose on downward and horizontal smoldering decreases, indicating that lignin content has the largest impact on smoldering velocities of the three constituents. Increasing the density decreases both the horizontal and vertical propagation velocities due to lower oxygen diffusion and the additional mass being consumed. [ABSTRACT FROM AUTHOR]

Biomass burning is a coupled exothermic/endothermic system that transfers carbon in several forms to the atmosphere, ultimately leaving mineral ash. The exothermic phases include flaming and smoldering, which produce the heat that drives the endothermic processes. The endothermic components include pre-heating and pyrolysis, which produce the fuel consumed by flaming and smoldering. These components can be broadly distinguished from each other based on temperature. For several years, we have researched the subpixel analysis of two temperature phases present in fire pixels detected in nighttime VIIRS data. Here, we present the flaming subtractive method, with which we have successfully derived temperatures and source areas for two infrared (IR) emitters and a cooler background. This is developed as an add-on to the existing VIIRS nightfire algorithm version 3 (VNF v.3) which uses Planck curve fitting to calculate temperatures and source areas for a single IR emitter and background. The flaming subtractive method works with data collected in four spectral ranges: near-infrared (NIR), short-wave infrared (SWIR), mid-wave infrared (MWIR) and long-wave infrared (LWIR). With sunlight eliminated, the NIR and SWIR radiances can be fully attributed to the primary IR emitter. The analysis begins with Planck curve modeling for the primary emitter based on the NIR and SWIR radiances, yielding temperature, source area and primary emitter radiances in all spectral bands. The primary emitter radiances are subtracted from each spectral band and then the residual radiance is analyzed for a secondary IR emitter and the background. Spurious results are obtained in pixels lacking a discernable secondary emitter. These misfit pixels revert back to the single IR emitter analysis of VNF v.3. In tests run for two California megafires, we found that the primary emitters straddle the temperature ranges for flaming and smoldering, the exothermic portions of biomass burning, which are apparently commingled on the ground. The secondary emitter temperatures span 350-750 K, corresponding to pre-heating and slow pyrolysis. The natural gas flare test case had few numbers of successful secondary emitter retrievals and a wide range of secondary emitter temperatures. The flaming subtractive analysis is the key addition to VNF version 4, which will commence production later in 2021. In 2022, we will seek validation of the VNF v.4 from nighttime Landsat and other data sources. [ABSTRACT FROM AUTHOR]

In many actual industrial scenes, the coal body and coal dust are not always in the tiled state, but in the inclined situation. A two – dimensional transient numerical model of coal oxidation reaction was established to study the self–ignition and smoldering characteristics of coal dust layers in the presence of inclination angle. The effects of gravity and thermal buoyancy were considered to solve the coupling problem of coal oxidation reaction and air flow. The results show that the growth coefficients of minimum ignition temperature of coal dust with thicknesses of 6.4 mm, 12.7 mm, 19.1 mm and 25.4 mm are 0.117 °C/°, 0.0467 °C/°, 0.033 °C/° and 0.033 °C/°, respectively. With the increase of hot plate temperature, the inclination of coal dust can greatly shorten the ignition delay time (IDT). The ΔIDT of coal dust inclination of 60° is 128 s/°C greater than that of 0°. The movement of high temperature point of coal dust in self–heating development stage is from the inside to the outside, and that in decaying stage is from the outside to the inside. In addition, some interesting phenomena in the process of coal self–ignition and smoldering have also been found. The influence of coal dust inclination on its self–heating is mainly reflected in the location of high temperature points and the spread of smoldering. This study is helpful to understand the characteristics of coal dust self–ignition and smoldering spread in inclined situation, and can guide the prevention of coal dust self–ignition. [ABSTRACT FROM AUTHOR]

A fire originated inside the chase1 (a vertical enclosure, usually constructed of wood, that houses and conceals a chimney) surrounding a modular fireplace system of a new residence, ultimately spreading and destroying the home. A lawsuit by the homeowner's insurance company was later filed against the general contractor and framing subcontractor, alleging that improper clearances between the fireplace and chase framing caused the fire. The author was retained to perform a forensic engineering analysis of the origin and cause of the fire. An exemplar modular fireplace system and chase were constructed and instrumented, and more than 30 test burns were performed. Additional testing evaluated gas migration from the fireplace log lighter into flexible combustion make-up air ducting and the burning propensity of the ducting. The testing and analysis concluded that the cause of the fire was not improper clearances to the chase framing but improper installation of the combustion air kit facilitating a mediation of the case. [ABSTRACT FROM AUTHOR]

The article addresses the issues of the particular terminology for fire forensic investigations. Definitions for the basic parameters of a fire hazardous area, determining its susceptibility to ignition, and their relationship to the impulses initiating such areas’ combustion are analyzed.Two main tasks of forensic fire examinations are reviewed: establishing the technical cause of a fire, its organizational cause, and consequences. The author gives definitions for these tasks and the term “ignition source”.The paper’s relevance stems from the need to prevent mistakes in terminology when conducting a forensic fire investigation. The article may be of use for practicing experts and specialists in fire forensics’ theory and practice.

Background: Gray matter pathology plays a central role in the progression of multiple sclerosis (MS). The occurrence of synaptic loss appears to be important but, to date, still poorly investigated aspect of MS pathology. In this systematic review, we drew from the recent knowledge about synaptic loss in human post-mortem studies. Methods: We conducted a systematic search with PubMed to identify relevant publications. Publications available from15 June 2021 were taken into account. We selected human post-mortem studies that quantitatively assessed the synapse number in MS tissue. Results: We identified 14 relevant publications out of which 9 reported synaptic loss in at least one investigated subregion. The most commonly used synaptic marker was synaptophysin; non-etheless, we found substantial differences in the methodology and the selection of reference tissue. Investigated regions included the cortex, the hippocampus, the cerebellum, the thalamus, and the spinal cord. Conclusion: Synaptic loss seems to take place throughout the entire central nervous system. However, the results are inconsistent, probably due to differences in the methodology. Moreover, synaptic loss appears to be a dynamic process, and thus the nature of this pathology might be captured using in vivo synaptic density measurements. [ABSTRACT FROM AUTHOR]

Fire performance of insulating materials made from renewable resources – Part 2: Investigations on the use as compartment filling in timber panel constructions In the previous article on the research project "more than just insulation – additional benefits of insulating materials made from renewable resources", the experimental investigations on the initiation, process and extinguishing behavior of smoldering processes, the effect of flame retardants and the emissions released in the combustion process were presented. In this paper, the investigations on the structural use of renewable insulation materials, instead of the previously required non‐combustible insulation, is presented in the context of wood panel construction. First, the final large‐scale fire test on the natural fire behavior of wood panel building components with renewable insulation materials is presented. Then, the development of analytical and numerical models for the separating function is illustrated. The paper concludes with an outlook on the research project "PyroProBiD", in which advanced transport and reaction models are being developed. [ABSTRACT FROM AUTHOR]

Abstract The effects of peat burning on organic‐rich agricultural soils of the Mezzano Lowland (NE Italy) were evaluated on soil profiles variously affected by smoldering. Profiles were investigated for pH, electrical conductivity, bulk density, elemental and isotopic composition of distinct carbon (and nitrogen) fractions. The results suggest that the horizons affected by carbon loss lie at depths 10–70 cm, where the highest temperatures are developed. We suggest that the exothermal oxidation of methane (mediated by biological activity) plays a significant role in the triggering mechanism. In the interested soils we estimated a potential loss of Soil Organic Carbon of approximately 110 kg m−2 within the first meter, corresponding to 580 kg CO2 m−3. The released greenhouse gas is coupled with a loss of soil structure and nutrients. Moreover, the process plausibly triggers mobility of metals bound in organometallic complexes. All these consequences negatively affect the environment, the agricultural activities and possibly also health of the local people.

Fire performance of insulating materials made from renewable resources – Part 1: Experimental investigations of smouldering processes and emissions In the research project "more than just insulation – additional benefits of insulating materials made from renewable resources", several sub‐projects investigated the moisture protection, thermal protection, noise insulation and fire protection as well as the sustainability and emission effect of insulating materials made from renewable resources. The primary goal of the research network was to significantly increase the applicability of renewable insulating materials and to eliminate obstacles to their use. In the field of fire protection behavior, the smoldering and burning of renewable insulation materials was analyzed and application limits defined in the context of multi‐storey buildings. The presented article deals with the experimental investigations on initiation, process and extinguishing behavior of smoldering, the effect of flame retardants and the emissions released in the combustion process. In the following article, the structural use of renewable insulation materials, instead of the previously required non‐combustible insulation, is presented in the context of wood panel construction. [ABSTRACT FROM AUTHOR]

The effects of peat burning on organic‐rich agricultural soils of the Mezzano Lowland (NE Italy) were evaluated on soil profiles variously affected by smoldering. Profiles were investigated for pH, electrical conductivity, bulk density, elemental and isotopic composition of distinct carbon (and nitrogen) fractions. The results suggest that the horizons affected by carbon loss lie at depths 10–70 cm, where the highest temperatures are developed. We suggest that the exothermal oxidation of methane (mediated by biological activity) plays a significant role in the triggering mechanism. In the interested soils we estimated a potential loss of Soil Organic Carbon of approximately 110 kg m−2 within the first meter, corresponding to 580 kg CO2 m−3. The released greenhouse gas is coupled with a loss of soil structure and nutrients. Moreover, the process plausibly triggers mobility of metals bound in organometallic complexes. All these consequences negatively affect the environment, the agricultural activities and possibly also health of the local people. Plain Language Summary: Peat soils are formed by accumulation of organic matter and represent a carbon sink. Unfortunately, they are often affected by burning as the organic matter can fuel combustion for a long time, ultimately releasing carbon dioxide and other greenhouse gases, and particulate matter (PM). It is not clear how peat burning ignite and spread. This study investigates the trigger mechanisms and effects of peat burning in the Mezzano Lowland (NE Italy). For this purpose, pH, electrical conductivity, bulk density and carbon elemental and isotopic compositions of Mezzano soil profiles variously affected by peat burning have been investigated. The results suggest that the burning doesn't propagate from surface and that the horizons affected by carbon loss lie at depths 10–70 cm, with temperatures up to 750°C. The process appears spontaneous, probably due to multiple factors such as drying, biological activity and exothermal oxidations. We estimated a loss of soil carbon of approximately 110 kg for square meter, corresponding to a release of 580 kg of CO2 for cubic meter of burnt soil. This carbon loss and the consequent release of gas and PM negatively affect the environment, the agricultural activities and possibly also the health of the local people. Key Points: Peat burning in the Mezzano Lowland is a process active since wetland reclamation and variously affects the soil structure and carbon contentThe main carbon loss occurs in the depth interval 10–70 cm, where temperature up to 750°C is recordedThe process induces negative effects to surrounding environment, agriculture activities and possibly also human health [ABSTRACT FROM AUTHOR]

Smoldering of coal is a considerable source of danger in coal mines because it can lead to a gas explosion, which can cause heavy casualties. This work investigated the apparent smoldering reaction model of coal and its kinetic parameters, which are needed to study smoldering fire in a closed fire area of a coal mine. A series of thermogravimetric tests at different oxygen concentrations were performed, and the change in the pyrolysis and oxidation reaction with the oxygen concentration was analyzed. It is concluded that the apparent reaction model of smoldering coal should include a three-step pyrolysis reaction (i.e., drying, depolymerization, and polycondensation) and a five-step oxidation reaction (i.e., oxidation of coal, semi-coke, and three types of char). A genetic algorithm is used to identify the optimal kinetic parameters of the smoldering reaction. It is determined that in atmospheres with different oxygen concentrations, coal has different kinetic parameters. When studying smoldering fire in a closed fire area of a coal mine, it is suggested to adopt the kinetic parameters of the smoldering reaction in a 1% oxygen concentration atmosphere. [ABSTRACT FROM AUTHOR]

Smoldering coalfield fires generate greenhouse gases (GHGs) and their precursors, contributing to the intensification of global warming. The study on the contribution of GHGs from smoldering coal fires to climate warming has been a disputed topic. This work proposes a novel approach to estimating GHG emissions from coal smoldering by measuring CO 2 , CH 4 , and CO under different thermal environments (220, 240, 260, and 300 °C). Results indicate that the contribution of CO 2 produced by smoldering to the greenhouse effect decreased from 33.67 % to 23.52 % as thermal environments increased. The comprehensive effect of greenhouse effect induced by the precursors (CH 4 and CO) increased from 66.33 % to 76.48 %, showing that the impact of precursors on the greenhouse effect should not be ignored. Additionally, the study demonstrates that the greenhouse effect generated by smoldering accounts for 18.40 %–40.92 % of the equivalent emissions produced by the complete combustion of the same mass of coal. This suggests that not all combustibles undergo conversion into greenhouse gases during the smoldering process. The annual amount of GHG emissions from coal fires in China is estimated as 6.52–42.27 million tons. Importantly, this study calculates basin-specific emission factors based on coal smoldering, providing a more accurate approach for determining the GHG emissions from coal fires. [Display omitted] • Establishing GHG prediction equation for coal smoldering through experiments. • The CO 2-e contribution of CO generated by coal smoldering reached 31.58 %. • Equivalent GHG generated by smoldering was 18.40 %–40.92 % of complete combustion. • Assessment of greenhouse effect by precursors was crucial and should not be ignored. • GHG emissions from smoldering and complete combustion of coal were compared. [ABSTRACT FROM AUTHOR]

Wood fiber insulation boards, as many other wooden materials, are susceptible to smolder. This type of slow and flameless thermal degradation has three upmost important drawbacks. First, smoldering can develop unseen until damages are noticed; second, it does not need any external heat to keep progressing, thus behaving as a self-sustaining process; third, it may shift into flaming combustion. Although wooden insulation materials are very competitive as insulators, its use is not permitted in several countries beyond mid-rise buildings due to smoldering hazard. As measuring of physical parameters is difficult and expensive at high temperatures, the objective of this investigation was to develop a theoretical model that comprises most relevant physical phenomena in order to serve as a supportive tool for further development of fire-retardant substances. The constructed model presents the novelty that it can simulate the self-sustaining smoldering without needing any external radiation heat, but only the self-heating generated by its own exothermic reactions. The model was built based on a program of experimental testing that included thermo-gravimetric analyses and differential-scanning calorimetry, being able to predict particle degradation at different heating rates and oxygen concentrations with errors of about 7,5 %. The adequacy of the model was also compared at the structural scale against a non-standard cone calorimeter test with terminal switching off heat radiation to emulate self-sustaining smoldering, which was used as model validation showing fits of about 23 % in consideration of mass loss, mass-loss rate and temperature profile. A comprehensive sensitivity analysis comprising 60 distinct parameters permitted to thoroughly assess the influence of each model input parameter, which is being presented as a ranking from the most to the less influencing parameters that prevent or foster self-sustaining smoldering. Several unexpected conclusions raised, positioning species’ densities, capacities and reaction activation energies as the most important parameters. To the best knowledge of the authors, this is the first model that can simulate the self-sustaining smoldering of wooden insulation materials, so it is expected to contribute on further development of fire retardant compounds for wooden products.

Thermochemical transformations of potential precursors for nanoparticles of Mn, Cr, and V in the wave of flameless combustion (smoldering) of RDX in ballasted systems were explored. No full reduction to a metallic state was detected. In the wave of flameless combustion, manganese carbonate was found to yield manganese(II) oxide with a particle size of 0.1–0.5 μm; ammonium dichromate, chromium(III) oxide with a particle size of 0.2–0.3 μm; while ammonium vanadate, vanadium(III) oxide in the form of platelets 20–30 nm thick and 0.5–1.0 μm in size at a specific surface of 18.6 m2/g. [ABSTRACT FROM AUTHOR]