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Considering the extensive application of wood materials in the construction and manufacturing, waste wood has potential of converting into new natural energy sources. In this study, cypress, pine and fir woods commonly used in China, as well as old samples for above each species (more than 200 years old) have been used to study the aging and species effects on their thermal stability and combustion models. To obtain the kinetic triplets of the pyrolysis process, all samples have been heated in a nitrogen atmosphere with heating rates of 5, 10, 15, and 20 K min−1. The kinetics parameters of pyrolysis throughout the conversion process were then calculated using isoconversional method, Coats-Redfern (CR), and masterplots methods. The reconstructed theoretical models have been then adjusted using the accommodation functions. The results of this study contribute to an increased understanding of the fire mechanism of waste woods, and implications concerning to provide scientific theoretical guidance for its feasibility as a new energy fuel more efficiently. [ABSTRACT FROM AUTHOR]

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Torrefaction has been one of the most significant steps to improve the biomass-based fuel quality. Rice husk has been widely used as typical agricultural biomass, due to a large annual yield in China. It is of great significance to explore the effect of dry/wet torrefaction on biomass pyrolysis and combustion reaction characteristics. In this study, the dry/wet torrefaction pretreatment of rice husk was carried out at various temperatures (200, 250, and 300 ; 180, 200, and 220 ) in ℃ ℃ the fixed bed and high-pressure reactor, where the starting temperature was room temperature, and the heating rate was 10 /min. The proximate and ultimate analysis of samples was then conducted by the infrared fast coal quality analyzer ℃ (5E-MAG6700) and element analyzer (Vario MACRO), respectively. The Thermogravimetric Analyzer (TGA) was selected for the non-isothermal (room temperature to 800, 20 /min) combustion of rice husk, rice husk torrefied char, and rice ℃ ℃ husk hydrochar. Moreover, the kinetics analysis of pyrolysis and combustion of samples were also conducted with the Coats−Redfern method and three common gas-solid reaction mechanism models (first-order model O1, phase boundary controlled reaction model R2 and R3). An evaluation was made on the effects of dry/wet torrefaction on the pyrolysis and combustion characteristics of rice husk. The results show that the dry/wet torrefaction increased the ash, fixed carbon, and carbon content of raw materials, while decreasing the volatile, hydrogen, and oxygen content. van Krevelen diagram displayed that the dry/wet torrefaction pretreatment behaved essentially like the process of dehydration and decarboxylation of raw materials, where the rice husk torrefied char at 300 (RT ℃ -300) was the most significant. Both pretreatments dominated the pyrolysis and combustion reaction parameters of rice husk, leading to the reduction in the pyrolysis reactivity. Dry torrefaction improved the combustion reactivity of rice husk, particularly with the temperature (200-300 ) rising. But the wet torrefaction ℃ slightly reduced the combustion reactivity of rice husk. The rice husk torrefied char presented a higher temperature of initial weight loss, a lower maximum rate of weight loss, the corresponding temperature and reactivity than the rice husk hydrochar during pyrolysis at 200 . More ℃ over, the rice husk torrefied char behaved with the lower final temperature of combustion and the maximum rate of weight loss corresponding to temperature, while the higher maximum rate of weight loss and reactivity, compared with the rice husk hydrochar. Interestingly, the linear regression index of model O1 was higher than that of the other two models for the pyrolysis and combustion reactivity of rice husk, rice husk torrefied char and rice husk hydrochar (the regression indexes were all above 0.95). The dry/wet torrefaction increased the pyrolysis activation energy of rice husk, whereas, the wet torrefaction decreased the combustion activation energy. Moreover, the pre-exponential factor of the samples in the two stages increased with an outstanding linear relationship, as the activation energy increased, indicating the kinetic compensation effect between pre-exponential factor and activation energy during combustion. The rice husk torrefied char had a lower pyrolysis activation energy and a higher pre-exponential factor than the rice husk hydrochar at the pretreatment temperature of 200 . In addition, the higher activation energy of combustion and the lower pre ℃ -exponential factor were achieved in the rice husk torrefied char, compared with the rice husk hydrochar. [ABSTRACT FROM AUTHOR]

In boreal regions, the frequency of forest fires is increasing. In this study, thermogravimetric analysis was used to analyze the pyrolysis kinetics of dead surface combustibles in different forest types within the Daxing'an Mountains, China. The results show that the combustible material load of forest types, the Larix forest (LG) is relatively high. Base on the E of kinetic parameters, the LG, and Quercus forest (QM) forest types had relatively high combustibility values and comprehensive combustibility values for 1-, 10-, and 100-h time lags. According to the obtained P values, the pyrolysis of dead surface fuels with 1-, 10-, and 100-h time lags is relatively difficult in the Larix / Betula mixed forest (L-B) and QM forest types. Therefore, mixed forests of the LG, L-B, and QM tree species can be established as fire-resistant forests to establish a fire barrier, reduce the combustibility of forest stands, and reduce the possibility of forest fires. [ABSTRACT FROM AUTHOR]

In order to study the effects of formation thickness and structural dip on in situ combustion and the combustion performance in the 1/4 of inverted nine-spot injection pattern, the scaled experimental system was developed based upon the ISC scaling law. The laboratory results show that within 1/4 of inverted nine-spot injection pattern the main combustion zone was swept completely with the oil recovery of 75%, leaving 5–15% oil saturation in the cracking/vaporization zone. Gas override and early breakthrough became more and more serious when the formation thickness increased, and oil recovery in the reservoir with structural dip was much lower than that in the 0° structural dip reservoir under same operating conditions. Conclusions have been drawn that employing nine inverted nine-spot injection pattern ISC can achieve a good oil recovery in G3-6-18 reservoir of Liaohe Oilfield in China. However, the formation thickness and the structural dip shall be taken into account when a project is designed as they play a major role on the sweeping efficiency. The sweeping efficiency can be enhanced by optimizing the operational parameters. [ABSTRACT FROM AUTHOR]

With the exhaustion and deterioration of coal resource, a lot of research has been focused on improving the combustion efficiency all over the world, especially in China, in recent years. In this study, several industrial waste slags, which can decrease the ignition temperature, including the gasification slag, deactivated methanol catalyst and furnace slag, are reused as catalysts to improve the combustion efficiency of high-sulfur coal. The kinetic analysis of combustion reaction using Coats-Redfern's model indicates that the industrial waste slags could efficiently reduce the activation energy of coal ignition. By comparing and analyzing the composition of the waste slags with TG-DTG, XRD and XRF, the efficiency of combustion-supporting of the waste slags was confirmed and optimized. • Three kinds of industrial waste slags are reused as catalysts of coal combustion. • The kinetic analysis indicates the activation energy of coal ignition reduces. • The combustion efficiency of high-sulfur coal can be improved by the waste slags. • Gasification slag is verified that the effect of combustion-supporting is the best. [ABSTRACT FROM AUTHOR]

Due to the huge reserves and great commercial potential of No. A group coal seam, the study on its thermal properties and combustion kinetics have attracted much attention. Via thermogravimetric (TG) analysis, the combustion characteristics and kinetics of No. A 3 coal were studied with three types of coal samples, with the grain diameter less than 200 meshes, 200~100 meshes, 100~60meshes, seperately. Under three characteristic temperatures such as T t , T p and T b , the whole combustion process could be roughly divided into 4 stages. Combined with the T max and T i , these five characteristic temperatures increase with elevating heating rates. The Kissinger-Akahira-Sunose (KAS) method and Flynn-Wall-Ozawa (FWO) method as reliable methods were used to verify the results of activation energy ( E a ) determined by of model-fitting methods. As complementary, the Coats-Redfern method was used to calculate the pre-exponential factor ( A ) and the correlation coefficient ( R 2 ). According to the evaluation criteria of E a and R 2 , D1 mechanism was the most probable model to depict the combustion kinetics. [ABSTRACT FROM AUTHOR]

Household air pollution (HAP) from indoor combustion of solid fuel is a global health burden linked to lung cancer. In Xuanwei, China, lung cancer rate for nonsmoking women is among the highest in the world and largely attributed to high levels of polycyclic aromatic hydrocarbons (PAHs) that are produced from combustion of smoky (bituminous) coal used for cooking and heating. Epigenetic age acceleration (EAA), a DNA methylation-based biomarker of aging, has been shown to be highly correlated with biological processes underlying the susceptibility of age-related diseases. We aim to assess the association between HAP exposure and EAA. We analyzed data from 106 never-smoking women from Xuanwei, China. Information on fuel type was collected using a questionnaire, and validated exposure models were used to predict levels of 43 HAP constituents. Exposure clusters were identified using hierarchical clustering. EAA was derived for five epigenetic clocks defined as the residuals resulting from regressing each clock on chronological age. We used generalized estimating equations to test associations between exposure clusters derived from predicted levels of HAP exposure, ambient 5-methylchrysene (5-MC), a PAH previously found to be associated with risk of lung cancer, and EAA, while accounting for repeated-measurements and confounders. We observed an increase in GrimAge EAA for clusters with 31 and 33 PAHs reflecting current (β = 0.77 y per standard deviation (SD) increase, 95 % CI:0.36,1.19) and childhood (β = 0.92 y per SD, 95 % CI:0.40,1.45) exposure, respectively. 5-MC (ng/m3-year) was found to be associated with GrimAge EAA for current (β = 0.15 y, 95 % CI:0.05,0.25) and childhood (β = 0.30 y, 95 % CI:0.13,0.47) exposure. Our findings suggest that exposure to PAHs from indoor smoky coal combustion, particularly 5-MC, is associated with GrimAge EAA, a biomarker of mortality. [ABSTRACT FROM AUTHOR]

Because nitrogen isotopes (δ15N) of emitted nitric oxide (e-NO) from combustion-related sources (mainly fossil fuels and biomasses) remain unknown, the δ15N values of emitted N oxides (e-NO x , the sum of emitted N dioxide (e-NO 2) and e-NO) have long been employed in the isotopic tracing of nitrate (NO 3 −) in the atmosphere, causing substantial uncertainties in the isotope differentiation of source contributions. Here we measured concentrations and δ15N values of e-NO x and NO 3 − from the burning of four biomass materials (corn, wheat, poplar, and pine) in northern China, based on which we calculated concentrations and δ15N values of the corresponding e-NO, e-NO 2 , initially produced NO (i-NO) and NO 2 (i-NO 2) before emissions and oxidizations. We found that 58 ± 12% of i-NO emitted as e-NO and 42 ± 10% was oxidized to i-NO 2 , 77 ± 7% of i-NO 2 emitted as e-NO 2 and 23 ± 3% was oxidized to NO 3 −, and the mean δ15N e-NO (−10.2 ± 6.0‰) was distinctly lower than the δ15N e-NOx (−2.3 ± 3.9‰) and δ15N e-NO2 (11.8 ± 3.6‰). Based on the δ15N i – NO (−0.2 ± 3.2‰) and δ15N i – NO2 (13.5 ± 3.8‰), we obtained the theoretical N isotope fractionations for the transformations from i-NO to i-NO 2 (23.8 ± 14.3‰) and from i-NO 2 to NO 3 − (8.0 ± 11.3‰) during biomass burning. These results filled the long-standing knowledge gap of species-specific δ15N signatures of NO x produced by biomass burning, expanded the understanding of N isotope fractionations of N oxidization under burning processes, and provided critical parameters for isotope source apportionment of NO x and NO 3 − in the atmosphere. [Display omitted] • δ15N of nitrate and NO x from biomass burning were measured in northern China. • δ15N of nitrate and NO x averaged 19.5 ± 4.1‰ and −2.3 ± 3.9‰, respectively. • δ15N of NO and NO 2 were first calculated as −10.2 ± 6.0‰ and 11.8 ± 3.6‰, respectively. • N isotope fractionations of the NO oxidation to NO 2 averaged 23.8 ± 14.3‰. • N isotope fractionations of the NO 2 oxidation to nitrate averaged 8.0 ± 11.3‰. [ABSTRACT FROM AUTHOR]

• A high efficiency parallel detailed mechanism based solution for knock prediction in 1D simulation. • A re-calibrated gasoline surrogate for China local commercial gasoline. • Predicted burn rate model and CCV model were introduced in knock model validation. • Relationship between auto-ignition in simulation and MAPO in experiment was built. • Validations were carried out with 645 cases on 3 engines, average error is below 2°CA. In this paper, a new engineering application method for gasoline engine knock prediction in a quasi-dimensional combustion model using a large-scale reaction mechanism is explored. First, an accelerated calculation strategy coupled with 1D calculation and large-scale reaction kinetics mechanism was developed to meet the needs of rapid automatic simulation in engineering. Secondly, a gasoline surrogate was created according to the test results of China 92# gasoline. The motor octane number (MON) and the research octane number (RON) values, which were closely related to knock, were calibrated using the detailed reaction mechanism. Then, the prediction of auto-ignition of unburned region was carried out combined with predicted burn rate model and cycle to cycle variation (CCV) model. The relationship between the experimental in-cylinder pressure oscillation and the simulated auto-ignition in the unburned region was established. The multi-conditions verification results of three engines with different displacement, compression ratio and combustion system arrangement show that the average errors of predicted knock CA50 are 1.6°CA, 1.8°CA and 1.9°CA respectively. [ABSTRACT FROM AUTHOR]

Due to the effective control of SO 2 emissions in China, nitrate becomes a key component in atmospheric aerosols, especially in haze episodes. Therefore, it is important to elucidate the formation pathways and sources of ambient NO 3 −. In this study, size-segregated particles were collected in Xiamen urban area from August 2019 to February 2021. Water-soluble inorganic ions and the dual isotope compositions (δ15N and δ18O) of NO 3 − were measured. A Bayesian isotope mixing model was used to investigate the formation pathways and contributions of different NO x sources to NO 3 −. The results showed that NO 3 − exhibited pronounced seasonal variations in concentrations and size distributions. The δ15N–NO 3 - and δ18O–NO 3 - values in different modes were lower in the warm season (May to November) than in the cold season (December to Feburary), attributing largely to the source and formation pathway changes. Bayesian model indicated that the contribution of the NO 2 + ⋅OH pathway in the warm season was higher than in the cold season, and the contribution decreased with the increase of particle size. However, opposite seasonal trends were observed for N 2 O 5 + H 2 O, N 2 O 5 + Cl− and NO 3 + HC pathways. The size distribution of δ15N–NO 3 - values was more influenced by the formation pathway than the isotopic fractionation. Results also indicated that the average contribution of soil emission (13.5%) to ambient NO 3 − was significantly lower than that of coal combustion (30.4%), ship emission (26.6%) and vehicle exhaust (29.6%). The contribution of soil emisison was almost double in warm season (17.7%) compared to cold season (9.3%) whereas coal combustion and vehicle exhaust decreased and ship emission remained relatively stable. Our results highlight the influence of formation pathways on the size distribution of δ15N–NO 3 - and the importance of after emission treatment of ship exhaust in reducing particle pollution in port cities. [Display omitted] • Size distributions of NO 3 − were strongly influenced by temperature in urban Xiamen. • Distinct seasonal variations of δ15N–NO 3 - and δ18O–NO 3 - were observed. • N 2 O 5 + Cl− pathway was prone to occur in coarse particles. • Ship engine exhaust contributed appreciably to NO 3 − aerosols. [ABSTRACT FROM AUTHOR]

The study of combustion characteristics and kinetic parameters plays an important role in the determination of the coal fire combustion regime. Four Chinese coals from the Jurassic and Carboniferous-Permian periods were selected to study the influence of the geological time on the coal combustion characteristics. The thermogravimetry and differential scanning calorimetry with different heating rates were employed to identify the combustion characteristics and oxidation reaction kinetics of coal samples. It was found that a high heating rate could boost the characteristic temperatures of coal, and the curves characteristics of thermogravimetry and differential scanning calorimetry of all coal samples were the same. The ignition temperatures of coals from the Carboniferous-Permian period were lower than that of coals from the Jurassic period. During the coal combustion stage, the heat release of the Carboniferous-Permian coal samples was 166.86–2423.84 J/g, higher than that of the Jurassic coal samples. By Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, and Starink methods, it was found that the activation energy required for combustion reaction of Carboniferous-Permian coals was 37.18–88.95 kJ/mol, lower than that of Jurassic coals, revealing that the combustion performance of Carboniferous-Permian coals was superior to that of Jurassic coals. [Display omitted] • Effect of geological time on the combustion characteristics of coal was investigated. • The oxidation kinetics of Jurassic and Carboniferous-Permian coals were verified by multiple methods. • The spontaneous combustibility of Jurassic and Carboniferous-Permian coals was compared by combustion characteristics. • A high heating rate increases the characteristic temperature of coal in the high-temperature phase substantially. [ABSTRACT FROM AUTHOR]

The combustion kinetics of waste capsicum stalk (WCS) in Western China is investigated through thermogravimetric analysis compared with sawdust and coal, and co-combustion of WCS with coal is also investigated. Results show that the ignition characteristics of WCS is better than that of sawdust and coal, and the activation energy E of WCS-volatile combustion and WCS-char combustion are 78.55 kJ mol and 44.59 kJ mol. However, integrating the characteristics of ignition and burnout, the combustion characteristic factor ( S) of WCS is lower than that of sawdust. With the increasing in the heating rate, the ignition of WCS is delayed. Oxygen concentration $$ C_{{{\text{O}}_{2} }} $$ affects E and k of volatile combustion largely under rich-oxygen condition, when $$ C_{{{\text{O}}_{2} }} $$ increases from 0.2 to 0.8, E has increased threefold and k also intensively increases from 10 to 10-10. Oppositely, effect of $$ C_{{{\text{O}}_{2} }} $$ on the E and k of char combustion is little, and there is an exponential relationship $$ S_{\text{N}} = 7. 1 2 8 \times 10^{ - 9} \times { \exp }(C_{{{\text{O}}_{2} }} /0. 3 6 8) - 6. 1 2 6 \times 10^{ - 9} $$ between S and $$ C_{{{\text{O}}_{2} }} $$. For the tests of co-combustion, all the experimental and weighted-average curves coincide well, and there is no remarkable synergistic effect. With the increase of mixing ratio that WCS added, E and k of volatile combustion increase, but correspondingly E and k of char combustion decrease. [ABSTRACT FROM AUTHOR]

NO x is an important precursor of fine particulate matter (PM 2.5) and O 3 and its oxidation product NO 3 − may be the main driver of PM 2.5. In this study, 76 daily fine particle samples were collected from a site in South China, and the characteristics of NO 3 − were studied using an improved Bayesian mixing model based on δ15N–δ18O compositions and online trace gas analysis. NO 3 − concentrations ranged from 0.60 to 21.7 μg/m3, accounting for 6.0 ± 3.3% of total PM 2.5 on average. δ15N–NO 3 − values varied from −3.6 to 15.4‰ (average: 7.5 ± 3.3‰). Driven by changes in chemical pathways and environmental parameters, including equilibrium fractionation and thermodynamic effects, δ15N–NO 3 - values were lowest in spring and highest in winter. δ18O–NO 3 - values varied from 21.0 to 90.1‰ (average: 62.4 ± 14.0‰). In spring, the lowest δ18O–NO 3 - values were observed due to high proportions originating from ·HO 2 and ·OH reaction pathways, as well as changes in other parameters. In winter, the highest δ18O–NO 3 - values were observed due to cold and dry weather, along with the lowest proportion from the ·OH pathway. Moreover, the trace gases CO, O 3 , NO x , SO 2 , and N 2 O 5 were measured seasonally to determine the main drivers of seasonality in δ15N–δ18O composition. Monte Carlo simulation was used to estimate the relative contributions of the gas-phase reactions of NO 2 and ·OH radicals and the hydrolysis of N 2 O 5. The results showed that the ·OH generation pathway was predominant throughout the year, with relative contributions of 72 ± 18%, 76 ± 16%, 63 ± 17% and 39 ± 15% in spring, summer, fall and winter, respectively. Coal combustion (50.1 ± 13.8%) was the predominant source of NO 3 − identified using the Bayesian model, and originated from central and southern Guangdong Province, as indicated by potential source contribution function analysis. • Characteristics of NO 3 − were studied by analysis of δ15N-δ18O and trace gas in PRD. • Both of δ15N–NO 3 - and δ18O–NO 3 −values were low in spring and high in winter. • ·OH generation was predominant NO 3 − formation from Monte Carlo simulation. • Coal combustion was the predominant source of NO 3 − modeled by the Bayesian. [ABSTRACT FROM AUTHOR]

Due to the high negative effects on health and environment, volatile aromatic compounds (benzene, toluene, ethylbenzene and xylene, BTEX) have drawn more and more attention recently. BTEX samples of four emission sources (coal combustion, vehicle exhaust, gasoline volatilization and solvent evaporation) and ambient air from three sampling sites (rural, urban and suburban) were collected during winter in Taiyuan, northern China. Gas chromatography–mass spectrometry and thermal desorption–gas chromatography–isotope ratio mass spectrometry were employed to investigate the composition characteristics and stable carbon isotopic (δ 13C) analysis of BTEX, respectively. The results revealed that the δ 13C value of BTEX for coal combustion, with the range of −23.8‰ to −25.2‰, was higher than that for vehicle exhaust, gasoline volatilization and solvent evaporation, ranging from −25.5‰ to −27.6‰, −28.0‰ to −30.9‰ and −27.7‰ to −32.1‰, respectively. Atmospheric BTEX concentrations were the highest at the suburban site (41.5 μg/m3) and the lowest at the rural site (27.0 μg/m3). The δ 13C values of atmospheric BTEX at rural, urban and suburban sites ranged from −24.8‰ to −26.2‰ (average −25.3‰), −24.8‰ to −26.9‰ (average −26.0‰) and −23.9‰ to −25.4‰ (average −24.8‰), respectively, indicating that the suburban site was enriched in 13C relative to rural and urban sites. The B/T ratio results indicated that coal combustion was the primary source of atmospheric pollution in Taiyuan. The mean contribution of emission sources in all three sampling site were determined by adopting Isosource-based quantitative calculation. For rural, urban and suburban sites, coal combustion, as the major source, made mean contributions of 62.3%, 46.0% and 74.1%, while vehicle exhaust was responsible for 22.0%, 30.6% and 15.3%, respectively. Coal combustion and vehicle exhaust were the top two primary sources of BTEX in Taiyuan, especially coal combustion provided a half contribution to atmospheric BTEX. Therefore, implementing controls on coal combustion is crucial to reduce ambient volatile aromatic compound pollution, especially in areas with high coal consumption. Image 1 • TD-GC-IRMS was employed to examine δ 13C of BTEX from typical sources and ambient air. • δ 13C value of BTEX from coal combustion are greater than from other emission sources. • Isosource-based method were conducted to analyze the source of BTEX. • Coal combustion and vehicle exhaust were the two primary sources of BTEX in Taiyuan. [ABSTRACT FROM AUTHOR]