Combustion Of Solid Fuels Research Articles

Time evolution of sulphur dioxide concentration generated by solid fuel combustion systems during the cold periods of the year

About 99% of sulphur dioxide present in the atmosphere comes from anthropogenic activities, the main source being industrial activity that processes sulphur materials, including burning fuels (coal, oil or gas), thus releasing sulphur dioxide into the air. The purpose of this paper is to monitor the concentration of sulphur dioxide during two seasons, in the ambient air of Petroșani, with the aim of highlighting the possible atmospheric pollution caused by thermal power plants that use solid fuel during the winter period. The monitoring periods were distributed over a period of 6 months (three in summer and three in winter), namely the summer months (May, June, July of 2022), the winter months of December (2022), January and February of 2023. The main objective of the measurements is to identify if there is an increase in sulphur dioxide concentration in the atmosphere, resulting from the burning of solid fuels from household activities during the winter period. Results indicate that there is a higher degree of SO2 pollution in the winter period, but the recorded values are far below the limits set by national legislation. The paper presents some measures to limit sulphur dioxide pollution in the context of climate change.

Polytetrafluoroethylene (PTFE) burn characteristics and toxicant formation in an oxidizer cross-flow via laser absorption tomography

A two-dimensional solid-fuel combustion experiment for fire-resistant polymers under forced convective cross-flow was developed to assess burn characteristics and toxicant formation using advanced laser absorption diagnostics that enable in situ species and temperature measurements near the fuel surface. The method was used to examine the thermochemical flow-field structure near the surface of polytetrafluoroethylene (PTFE) exposed to a well-defined solid-fuel pilot flame burning polymethyl methacrylate (PMMA). Infrared diode and quantum cascade lasers were used to probe rovibrational absorption transitions of hydrogen fluoride (HF) and carbon monoxide (CO), respectively, at the exit plane of a heterogeneous cylindrical fuel grain from which temperature and mole fraction could be inferred. A laser absorption tomography (LAT) technique with a Tikhonov-regularized Abel inversion was applied to reconstruct radially-resolved profiles in the axisymmetric reacting flow which, when compiled across a range of fuel lengths, provided a two-dimensional image of the near-surface reaction layer. Thermochemical data and reaction rate parameters from existing fluorocarbon chemistry models were used to generate high-temperature simulations of product species concentrations and temperature as a function of oxidizer-to-fuel ratio to elucidate observed trends and identify key reactions relevant to the novel dataset. The geometry and scale of the composite fuel experiments is intended to be tractable for reactive multi-physics models, enabling quantitative comparison of combustion characteristics and ultimately improved predictive capability of toxicant quantities resulting from fluoropolymer combustion in fire environments.

Source Profiles of Particle‐Bound Phenolic Compounds and Aromatic Acids From Fresh and Aged Solid Fuel Combustion: Implication for the Aging Mechanism and Newly Proposed Source Tracers

AbstractPhenolic compounds and aromatic acids, as oxygenated aromatic compounds, can participate in photochemical reactions to form secondary organic aerosols (SOAs), and thus strongly impact climate and human health. In the present study, on‐site combustion experiments were conducted to determine primary emissions and secondary formation of phenolic compounds and aromatic acids released from burning of a variety of solid fuels using a potential aerosol mass‐oxidation flow reactor (PAM‐OFR). Emission factors (EFs) of phenolic compounds and aromatic acids from aged samples were 1.04 to 4.04 and 0.90 to 2.80 times those in the fresh PM2.5, respectively, implying significant amounts of these compounds produced from atmospheric aging processes. Substantially different emission profiles of phenolic compounds were observed between coal and biomass burning, with coal combustion mainly released single‐ring species (82%–86% in primary and 86%–89% in secondary emissions), while biomass burning released more two‐, three‐, and four‐ring species (59%–69% in primary and 50%–58% in secondary emissions). Aromatic acids emission profiles from coal and biomass burning also differed considerably, with biomass burning producing significantly higher (>2 times) abundance of dibasic acids than coal combustion, suggesting higher potential of producing additional ‐COOH group from biomass burning. Benzenediol, cresol, dimethylphenol, 1‐pyrenol, phenanthrenol, and hydroxylbenzonic acid were identified as SOA as they were mainly formed during simulated aging processes. Benzenediol acid/phenanthrenol was much lower from biomass (3.70 ± 1.29) than coal (62.7 ± 9.61), and these values remained stable after aging, suggesting this ratio being suitable as tracer for distinguishing different fuels combustion in source apportionment analysis.

Laser modification of heating surfaces: A new approach to reduce boiler slagging

Slagging and fouling of boilers are typical technological problems in the combustion of solid fuels (especially coal and biomass). This study proposes a novel approach based on laser texturing of the near-surface layer of steel used to make heating surfaces of coal-fired boilers. This approach is aimed at improving the resistance of metal surfaces to slagging. The formation of slag deposits on the surfaces of AISI 310 S steel modified by laser radiation has been experimentally studied. The formation of slag melt was analyzed on the surface of modified and polished steel plates during heating to 1400 °C. High-temperature heating and interaction with slag led to a change in the chemical composition of the steel. A significant increase in the chromium content (up to 47%) of the steel surface and the transformation of its texture with the formation of grains up to 2.5 µm in size were established. Laser surface treatment significantly increased the resistance of the steel to such changes and also reduced the grain size to 1.5 µm. As a result of laser modification of surfaces, the temperature of slag formation shifts to higher values (higher by 60–75 °C compared to the unmodified polished surface). The anisotropic texture (cauliflower type) contributed to a decrease in the size of the slag spreading front, and also had by self-cleaning properties from the mineral melt. The latter allows to increase the reliability and energy efficiency of boiler equipment.

Identification and Parametrization of Key Factors Affecting Levoglucosan Emission During Solid Fuel Burning.

Levoglucosan (LG) is a pyrolysis product of cellulose and hemicellulose at low combustion temperatures. However, LG release cannot be determined only by considering the contents of cellulose and hemicellulose exclusively due to the complexity of combustion processes and the physical-chemical properties of the fuel. This study detected the emission factors (EFs) of LG from 22 different solid fuel samples (including coal and biomass) by considering 18 different fuel properties and five combustion parameters. The average LGEFs during solid fuel burning varied in a range of 0.03-136 mg kg-1, with a magnitude difference of 1-4 orders. While the variations in cellulose (59.5-368 mg g-1) and hemicellulose (73.5-165 mg g-1) contents of fuel samples were only one- to 6-fold. A short combustion duration (<150 min) and a medium combustion temperature (200-400 °C) influenced by volatile and ash contents are crucial for the generation and accumulation of LG. A random forest coupled with the Akaike information criterion stepwise regression model successfully explained 96% of the total LG emission variation using three variables (ash content, cellulose content, and modified combustion efficiency). The ash content promoted coke formation and LG chain cracking by increasing the pyrolysis temperature and is considered the most important factor. The alkali metal in ash can reduce the energy barrier of intramolecular ring contraction reactions and inhibit the dehydration reactions, which led to additional heat being utilized by the competitive pathways of LG formation. This study provided a method to address the parametrization and release mechanisms of combustion source emissions.

Study on the Temporal and Spatial Release Behavior of Alkali Metals during the Combustion of Different Solid Fuels

Study on the Temporal and Spatial Release Behavior of Alkali Metals during the Combustion of Different Solid Fuels

Low-Temperature-Solid Combustion Technology of Biomass for Pollution Reduction: Potentials and Necessary Fundamentals.

The high temperature of solid combustion in modern combustors leads to serious pollution in the combustion of biomass and solid wastes. The broad demands of relatively small-scale combustion of solid fuels and the imposition of increasingly strict emission limits require more economical methods for pollution reduction. Based on literature and our own work, low-temperature-solid combustion technology, which applies low temperature for solids but normal temperature for gas during combustion, was introduced in this paper. The potential of this technology in pollution reduction was analyzed, and necessary fundamentals for equipment design/operation were discussed. It showed that, for straws, more than 60% of deposit and particle emission can be reduced and 100% of ash can be recycled when the solid temperature is <600 °C. Fundamentals on rates of inorganic release, char oxidation, phase transformation in the condensed phase, and NOx/SOx release are necessary for better application of the technology.

Cooking as an organic aerosol source leading to urban air quality degradation

Air quality degradation events in the urban environment are often attributed to anthropogenic aerosol sources related to combustion of liquid or solid fuels in various activities. The effects of massive cooking emissions during Greek nationwide traditional festivities were investigated by a combined characterization of particulate matter (PM) levels and organic aerosol (OA) sources. Focus was centered on periods around two major festivities, namely “Fat Thursday” and Easter Sunday along six different years. OA sources were apportioned through Positive Matrix Factorization (PMF) on Aerosol Chemical Speciation Monitor (ACSM) mass spectra, while the spatial characteristics of the episodes were assessed through a low-cost, sensor-based PM2.5 monitoring network operating in Athens and other Greek cities. Contrasts were examined by considering a 15-day period around each event, while the effect of the 2020–2021 mobility restrictions, related to COVID-19, was also assessed. An episode-specific cooking organic aerosol (COA) spectral profile was delineated, and can be considered as a reference for ambient COA from meat grilling. Severe pollution episodes that affected the entire Athens basin were recorded, with PM2.5 concentrations exceeding 300 μg m−3 on occasions. COA contributions dominated primary organic aerosol (POA) and made up almost half of OA concentrations. During “Fat Thursday” COA concentrations and contributions peaked during night-time (23.2 μg m−3 and 46 %, respectively) while for Easter Sunday COA maxima were recorded in the early afternoon (27.4 μg m−3 and 39 %). Analyzing a full-year OA source dataset, revealed a pronounced recreational cooking pattern in central Athens, with COA concentrations rising towards the weekend, reflecting the impact of the food service sector. In view of the upcoming review of the EU air quality directive, foreseeing stricter annual PM2.5 limits as well as 24-h limit values and related alerts, the mitigation of cooking emissions appears as a potent instrument for achieving tangible air quality benefits.

Improved Comprehensive Mechanism for Initial Deposit Formation: The Role of Thermophoresis and Glue Effect in Solid Fuel Combustion

Improved Comprehensive Mechanism for Initial Deposit Formation: The Role of Thermophoresis and Glue Effect in Solid Fuel Combustion

Insight into the Primary and Secondary Particle-Bound Methoxyphenols and Nitroaromatic Compound Emissions from Solid Fuel Combustion and the Updated Source Tracers.

Methoxyphenols and nitroaromatic compounds (NACs) have strong atmospheric radiative forcing effects and adverse effects on human health. They are emitted from the incomplete combustion of solid fuels and are secondarily formed through photochemical reactions. Here, an on-site study was conducted to determine the primary emission and secondary formation of particulate phase products from a variety of solid fuels through a potential aerosol mass-oxidation flow reactor. Emission factors for total quantified methoxyphenols and NACs (i.e., EF∑Methoxyphenols and EF∑NACs) varied by 2 orders of magnitude among different fuels, which were greatly influenced by volatile matter, incomplete combustibility, flame intensity, and combustion temperature. Guaiacol and 4-nitro-2-vinylphenol were used as tracers for primary organic aerosol due to the low aged-to-fresh ratios (0.21-0.97), while 4-methyl-guaiacol, 4-ethyl-guaiacol, eugenol, 4-methyl-syringol, isoeugenol, acetovanillone, syringaldehyde, homovanillin acid, vanillin acid, and syringic acid were identified as secondary organic aerosol (SOA) (aged-to-fresh ratios between 1.90 and 4.20). During simulated aging, the -CHO group reacted with the hydroxyl radical (•OH) to form the -COOH group, but there was no correlation between syringol and 4-nitrosyringol, implying that •OH is the main reactant rather than the nitriate radical (•NO3) in the atmospheric aging processes of methoxyphenols. Aging caused substantially different emission profiles due to variable photochemical reaction properties. The fresh EFs for guaiacol emitted from the biomass burning ranged from 3.80 ± 0.44 to 26.2 ± 5.40 mg·kg-1, which were much higher than those in coal combustions (of 0.03 ± 0.01 to 1.42 ± 0.28 mg·kg-1). However, the aged EFs (EFaged) for guaiacol was 1.02 ± 0.06 to 1.61 ± 0.11 mg·kg-1 in most biomass combustions, which were comparable with those of the bituminous chunk (1.20 ± 0.16 mg·kg-1). Therefore, guaiacol, a traditional biomass marker, is not an ideal tracer for aged PM2.5 emitted from biomass burning. Indeed, the syringol/guaiacol and syringol/4-nitrosyringol ratios were found to be more suitable and efficient to be used in source characterization.

Intensification of the Process of Coal Ignition by Adding Biomass Under Flame Combustion Conditions

The characteristics of thermal decomposition and combustion processes on the heating of fine particles (100–200 m) of Chernogorsky coal, larch wood, and mixtures based on them, including the concentrations of the main components of flue gases (CO, CO2, NOx, and H2S + SO2), were determined using moderntechniques, analytical instrumentation, and experimental equipment. The biomass contents of the fuel mixtures based on coal were 10, 20, and 30 wt %. The temperatures at which the ignition of the coke residue occurred and the combustion process was completed were established using the synchronous thermal analysis of individual solid fuels and their mixtures. Larch sawdust was more reactive than Chernogorsky coal due to the lowest temperature at which the carbon residue was ignited; therefore, the addition of even 10% biomass to coal had a positive effect on the reactivity of the mixture. Under conditions of fuel heating in a flow of air at temperatures of 500–800C, the ignition delay times were determined using a hardware–software complex for high-speed video recording of fast processes. Based on the results of the experimental studies, it was found that the ignition delay times of the test fuels in a flow of heated air varied in a range from 0.02 to 0.22 s, and the addition of 10–30 wt % biomass to coal shortened the ignition delay times of fuel mixtures by up to 50%. The analysis of flue gases upon the combustion of solid fuels made it possible to establish the concentrations of the main anthropogenic emissions; the use of biomass as an additive to coal reduced the emissions of carbondioxide, nitrogen oxides, and sulfur compounds (H2S + SO2) by 2.2–13.5, 6.2–28.9, and 18.2–33.3%, respectively.

Biomarkers for polycyclic aromatic hydrocarbons in human excreta: recent advances in analytical techniques-a review.

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants that are generated by the incomplete combustion of organic materials. The main anthropogenic sources of PAHs are the combustion of solid fuels for heating purposes, illegal waste incineration, road transport and industries based on fossil fuels. PAHs can easily enter the body because they are present in all elements of the environment, including water, soil, air, and food. Due to their ubiquitous presence, PAHs, may exert a harmful effect on human health. Assessing PAH exposure through biomonitoring mostly involve techniques to measure the concentration of 1-hydroxypyrene in human urine. Nevertheless, through recent progress in analytical techniques, other common metabolites of PAHs in human biospecimens can be detected. A scientific literature search was conducted to determine which hydroxy derivatives of PAHs are markers of PAHs exposure and to reveal the leading sources of these compounds. Techniques for analyzing biological samples to identify OH-PAHs are also discussed. The most frequently determined OH-PAH in human urine is 1-hydroxypyrene, the concentration of which reaches up to a dozen ng/L in urine. Apart from this compound, the most frequently determined biomarkers were naphthalene and fluorene metabolites. The highest concentrations of 1- and 2-hydroxynaphthalene, as well as 2-hydroxyfluorene, are associated with occupational exposure and reach approximately 30ng/L in urine. High molecular weight PAH metabolites have been identified in only a few studies. To date, PAH metabolites in feces have been analyzed only in animal models for PAH exposure. The most frequently used analytical method is HPLC-FLD. However, compared to liquid chromatography, the LOD for gas chromatography methods is at least one order of magnitude lower. The hydroxy derivatives naphthalene and fluorene may also serve as indicators of PAH exposure.

MILD Combustion of Solid Fuels: Its Definition, Establishment, Characteristics, and Emissions

MILD Combustion of Solid Fuels: Its Definition, Establishment, Characteristics, and Emissions

Operational experiences of chemical-looping combustion with 18 manganese ores in a 300W unit

Chemical-looping combustion is a novel combustion technology with inherent CO2 capture. The process uses oxygen carriers in the form of metal oxide particles to transfer oxygen from air to fuel. The particles make up the bed material in two fluidized-bed reactors, the air reactor and the fuel reactor, and circulate between the two reactors. Natural minerals of low cost are attractive as oxygen carriers in chemical-looping combustion (CLC), in particular when used for combustion of solid fuels. The presence of ash can restrict the effective lifetime of the oxygen carrier either by loss of bed material associated with the ash removal or by direct reactions between ash and oxygen carrier that impair its reactivity. Independent of the presence of ash, the oxygen carrier lifetime can be limited by attrition leading to loss of fines.Ores considered and used in chemical-looping combustion include ilmenite, iron ore and manganese ore. Manganese ore is the least tested of these, although several studies suggest manganese ores often have higher reactivity as compared to the other two. The present study compares data from operation of 18 different manganese ores in a 300 W chemical-looping combustor, involving 329 h of operation with fuel. Results for 10 of these, involving 148 h of operation, have previously not been published. Some of these manganese ores have also been used in larger pilots, as well as in a 10 MW circulating fluidized-bed boiler.Operational results indicate significant differences between the ores with respect to performance, with syngas conversion ranging between 80 and 100% and methane conversion ranging between 17 and 59% and attrition rates ranging from very high to as low as 0.05%/h. For a few ores formation of fines led to operational failure after only a short period with fuel and for one of the ores agglomeration led to failure.The correlation between performance data and oxygen-carrier characteristics, including elementary analysis, was assessed. Gas conversion for both syngas and methane were correlated to gas conversion in lab testing. However, neither jet cup attrition data nor crushing strength was correlated to attrition in 300 W. This suggests that the mechanisms causing attrition are different at hot conditions and with reactions taking place, which emphasizes the need for pilot testing in the screening of manganese ore oxygen carriers.Fortunately, the correlation between gas conversion and attrition was weak. Thus, high reactivity is not necessarily associated with low attrition assistance and vice versa and several ores show high reactivity in combination with low or moderate attrition. Consequently, screening of manganese ores is well worth while, in order to find materials that can give both high conversion and long life-time. The best four ores were the Chinese Guizhou, South-African UMK, Elwaleed B, and Sibelco´s Braunite having syngas conversion(%)/attrition rate(%/h) of 98.3/0.05, 100/0.33 100/0.5 and 96.7/0.12, respectively.

Successes and challenges to implementing the Fondo de Inclusión Social Energético LPG access program in Peru: Novel insights from front-end implementers

BackgroundHousehold air pollution due to the burning of solid fuels is one of the leading risk factors for disease and mortality worldwide, resulting in an estimated three million deaths annually. Peru's national LPG access program, FISE, aims to reduce the use of biomass fuels and increase access to cleaner fuels for cooking in low-income Peruvian households through public-private partnerships. Perspectives from front-end program implementers are needed to better understand barriers and facilitators to program implementation and to identify strategies to strengthen program reach, uptake, and health impact. MethodsWe conducted fourteen 30–60-minute, semi-structured interviews with FISE-authorized LPG vendors (also known as agents) in Puno, Peru from November to December of 2019. Questions focused on barriers and facilitators to program enrollment and participation as an LPG agent, and agents' motivations for participating in the program. ResultsOverall, agents expressed satisfaction with the FISE program and a willingness to continue participating in the program. Distance from main cities and the homes of program participants, knowledge of FISE and LPG stoves among community members, cell service, and lack of communication with FISE authorities were cited as barriers to implementation and LPG distribution. Agents' previous experience selling LPG, as well as their social networks and understanding of the health impacts of household air pollution, aided agents in more effectively navigating the system of FISE rules and regulations and in better serving their clients. Many agents were motivated to participate in FISE because they saw it as a service to their community and found ways to prioritize the needs of beneficiaries. ConclusionThe FISE program provides an example of how a large-scale national program can successfully partner with local private enterprises for program implementation. Building upon the strengths of community-based LPG agents, educating community members on the use and benefits of LPG, incentivizing and supporting delivery services, and improving communication will be key for increasing program utilization and exclusive use of LPG, and improving health outcomes among Peru's most vulnerable populations.

Modification of perforated plate in fluidized-bed combustor chamber through computational fluid dynamics simulation

The combustion of solid fuels in a combustion chamber can be perfect if all the fuel included can burn out, and nothing remains. The combustion chamber requires sufficient air to burn all the fuel; therefore, meeting the air supply requires modifications with various considerations. The perforated plate modeled through computational fluid dynamics (CFD) was modified to investigate the excess air supply into the combustion chamber. The CFD simulation modeled in this study was used to validate the results of the experiments carried out with the previous fluidized-bed combustor technology. The simulation results show that the temperature increased for all fuels tested in geometry-2 compared with geometry-1. The best boiler efficiency from the simulation results is in geometry-1 for 45% oil palm midrib fuel with a mass flow rate of 7.78 kg/s. The maximum radiation was recorded from geometry-2 at a variation of 66.939 W/m2, with a heat loss level of 1.10 W/m2. Overall, the simulation was performed by modifying the fuel floor plate in geometry-2 to increase the temperature and radiation with lower heat loss.

Activation of the combustion of low-reactivity solid fuels with metal-rolling production waste

The effect of the addition of different amounts of metal-rolling production waste (metal scale in amount of 1–10 wt%) on combustion characteristics of low-reactive solid fuels (anthracite and semi-coke) was studied. XRD analysis of the metal scale identified Fe3O4 and Mn3O4 phases along with a cubic Fe phase. The characteristics of ignition and combustion of the samples were studied via thermal analysis and high-speed video recording at heating medium temperatures of 600–800 °C (with 100 °C step) using a combustion chamber. It was experimentally found that the addition of a metal scale, regardless of its weight content, increases the fuel reactivity, as evidenced by the drop in temperature of the onset of intense oxidation (ΔTi) by 2–32 °C and the decrease in the ignition delay time (Δτi) by 0.2–2.2 s. The metal scale additive also increases the fuel combustion rate, which was evidenced by the maximum rate of oxidation (Δwmax) increasing by 0.1–2.0 wt%/min and, hence, the temperature of the end of oxidation (ΔTf) reducing by 13–68 °C. Due to combustion intensification, the carbon content in ash decreased by 55 rel% on average. The amount of CO and NOx contained in gas-phase combustion products diminished as well.

ASSOCIATION BETWEEN HOUSEHOLD SOLID FUEL USE AND RISK OF SARCOPENIA: DATA FROM THE CHINA HEALTH AND RETIREMENT LONGITUDINAL STUDY

Objective: Few studies have examined the effects of air pollutants on the risk of sarcopenia, especially air pollution from indoor settings. We aimed to explore the cross-sectional and longitudinal associations of household solid fuel use for cooking and heating, separately and simultaneously, with risk of sarcopenia. Design and method: Cross-sectional and follow-up data from the China Health and Retirement Longitudinal Study (CHARLS) were used. Multivariable-adjusted generalized linear models and Cox proportional hazards regression models were performed to estimate the odds ratio (OR) and hazard ratio (HR) with 95% confidence intervals (CI), respectively. We also calculated the extent of interaction or joint relations of sociodemographic and behavioral factors and household fuel use with sarcopenia. Results: 11,494 (median age: 57.0 years; 47.4% males) and 7,483 (median age: 57.0 years; 46.9% males) participants were included in the cross-sectional and follow-up study, respectively. After fully adjusting for covariates, both using solid fuels for cooking and heating were positively associated with incident sarcopenia in the longitudinal analyses, with hazard ratio (HR) (95% CI) of 1.56 (1.28-1.89) and 1.26 (1.04-1.52), respectively. When comparing to those using clean fuels for both cooking and heating, participants using solid fuels for both cooking and heating were more likely to have incident sarcopenia [HR (95% CI):1.52 (1.19-1.93)]. In addition, compared with those persistently used clean fuel for cooking, significantly higher risk of new-onset sarcopenia was found in participants persistently used solid fuels [HR (95% CI):2.05 (1.55-2.71)]. Moreover, significant multiplicative and/or additive interactions were observed between age, smoking status and solid fuel use for cooking with risk of sarcopenia (all P for interaction &lt; 0.05). Similar results were found in the cross-sectional analyses. Conclusions: Household solid fuel use was significantly associated with higher risk of sarcopenia. In addition, ageing and smoking had synergetic effects with burning solid fuels for increasing the risk of sarcopenia. Our results highlighted the importance of taking multi-pronged measures from both aspects of air pollution and health behavior to prevent sarcopenia and promote healthy ageing.

Examination of long-time aging process on volatile organic compounds emitted from solid fuel combustion in a rural area of China

Volatile organic compounds (VOCs) emitted from solid fuels combustion (e.g., biomass and coal) are still the dominant precursors for the formation of tropospheric ozone (O3) and secondary organic aerosols (SOAs). Limited research focused on the evolution, as known as atmospheric aging, of VOCs emitted during long-timescale observations. Here, freshly emitted and aged VOCs from common residual solid fuel combustions were collected onto absorption tubes before and after passing through an oxidation flow reactor (OFR) system, respectively. The emission factor (EF) of freshly emitted total VOCs is in descending order of corn cob ≥ corn straw > firewood ≥ wheat straw > coals. Aromatic and oxygenated VOCs (OVOCs) are the two most abundant groups, accounting for >80% of the EF of total quantified VOCs (EFTVOCs). Briquette technology shows an effective reduction of the VOC emission, demonstrating a maximum 90.7% lower EFTVOCs in comparison to that of biomass fuels. In contrast, each VOC shows significantly different degradation in comparison to EF of freshly emitted and after 6- and 12-equivalent day aging (actual atmospheric aging days calculated from aging simulation). The largest degradations after 6-equivalent days of aging are observed on alkenes in the biomass group (60.9% on average) and aromatics in the coal group (50.6% on average), consistent with their relatively high reactivities toward oxidation with O3 and hydroxyl radical. The largest degraded compound is seen for acetone, followed by acrolein, benzene, and toluene. Furthermore, the results show that the distinction of VOC species based on long-timescale (12-equivalent day aging) observation is essential to further explore the effect of regional transport. The alkanes which have relatively lower reactivities but high EFs could be accumulated through long-distance transport. These results provide detailed data on fresh and aged VOCs emitted from residential fuels which could be used to explore the atmospheric reaction mechanism.

Flammability maps for microgravity burning of a small flat material in a quiescent ambient

A gas fuel supplied burner (BRE) was used to emulate burning of real solid and liquid fuels in microgravity to address the fire safety concerns of spacecrafts. The analytical solution of these flames was utilized to predict the steady flame temperature, and a critical temperature range of 1100–1200 K, was chosen to distinguish between self-extinguished and steady flames. Steady flames are examined on a flammability diagram composed of the emulated heat of combustion and heat of gasification. It is shown that for a given heat of combustion, there is an upper and a lower limit value of heat of gasification that will allow steady burning. The theory and the boundary of extinction experimental data support the limits. The upper limit is classed as radiation extinction with the lower like the fire-point in Earth gravity and is called small flame extinction limit. A theoretical prediction for steady burning is demonstrated to within 10% for a given atmospheric condition of pressure and oxygen, material diameter, and external radiative heat flux. The material properties of Δhc, heat of combustion; L, heat of gasification; and Tb, burning temperature allow for the prediction of burning in microgravity, and can serve as a method to evaluate fire safety of spacecrafts.