Study on pore structure change and lean oxygen re-ignition characteristics of high-temperature oxidized water-immersed coal

Bu, Yunchuan; Niu, Haijun; Wang, Haiyan; Li, Shuo-peng; Yang, Yanxiao; Qiu, Tian; Wang, Gang

doi:10.1016/j.fuel.2022.124346

Cited by 22 publications

(5 citation statements)

References 20 publications

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“…Coal inevitably undergoes various changes in its physical structure and surface morphology during LTO 21 , which affects the heat and mass transfer efficiency when oxidizing coal at low temperatures 22 . To illustrate, the micropores of the coal affect the maximum heat release and the initial heat release of LTO 23 . During the LTO of coal, many mesoporous channels are formed.…”

Section: Introductionmentioning

confidence: 99%

Influence of mudstone on coal spontaneous combustion characteristics and oxidation kinetics analysis

Zhang,

Zou,

et al. 2024

Sci Rep

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To explore the spontaneous combustion characteristics and hazards of the low-temperature oxidation (LTO) stage in the process of spontaneous combustion of coal and mudstone, the pore structure, spontaneous combustion characteristic parameters, and exothermic characteristics of coal and mudstone were tested and studied, and the oxidation kinetic parameters were calculated. The results show that mudstone has a larger specific surface area and pore volume than coal. From the fractal characteristics, the pore structure of mudstone is more complex than that of coal. According to the comparison of theoretical and actual gas generation and oxygen consumption rate curves, it is found that there is an interaction between coal and mudstone in the LTO process. With the increase of mudstone mass ratio, gas production, and its oxygen consumption rate increase. Among them, CM-4 (Coal:Mudstone = 1:1) has the highest exothermic intensity and the exothermic factor (A) and fire coefficient (K) increase with the increase of mudstone content. The apparent activation energy of the mudstone sample is lower than that of the raw coal, indicating that the sample after adding mudstone is more likely to have spontaneous combustion in the LTO stage.

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Section: Introductionmentioning

confidence: 99%

Influence of mudstone on coal spontaneous combustion characteristics and oxidation kinetics analysis

Zhang,

Zou,

et al. 2024

Sci Rep

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“…This threatens the lives and health of workers and can lead to huge economic losses. 4 Recently, the phenomenon of secondary oxidation spontaneous combustion of oxidized coal samples, such as re-ignition in old empty areas and unsealed and re-ignition in fire areas, has gradually increased, 5,6 making it more difficult to prevent coal spontaneous combustion (CSC). Therefore, it is particularly important to study the prevention of secondary oxidation and re-ignition of pre-oxidized coal samples.…”

Section: Introductionmentioning

confidence: 99%

DL‐malic acid for inhibiting the re‐ignition of long‐flame coal and its micro‐reaction mechanism

Bu,

Niu,

Wang

et al. 2024

Asia-Pacific J Chem Eng

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To study the metal ion chelating agent (DL‐malic acid) inhibiting oxidation characteristics of residual coal in goaf, the microscopic thermal transformation characteristics of the treated coal samples were obtained using apparent morphology, infrared spectroscopy, free radical testing, and thermal analysis. The results demonstrate that after the addition of malic acid, the sphericity and roundness of the coal samples decrease, and the small fractured particles accumulate in the pores of the oxidized coal samples and, thereby, reduce the number of coal–oxygen contact sites. The addition of 10% malic acid promotes the conversion of functional groups (FG) and free radicals in pre‐oxidized coal, inhibits the catalytic effect of metal ions, generates more active sites, and increases the total heat release during the combustion process. There are strong endothermic points in the malic acid‐treated coal samples, and the free water evaporation blocked by small particles in the holes delays the initial heat release temperature of the coal samples. Pre‐oxidation can promote changes in the valence state of metal ions in coal, increase the adhesion between broken pre‐oxidized coal particles via malic acid chelation, and lose the catalytic effect of metal ions; this inhibits the process of oxidative re‐ignition of coal samples.

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“…18 Bu et al compared preoxidized and watersoaked coal samples with raw coal based on SEM, nitrogen adsorption, and other experiments and found that the ratio of mesopores and macropores in the high-temperature-oxidized water-soaked coal sample increased, and the augmentation of coal's oxygen interaction sites fostered its oxidation process. 19 Bu et al found that water-soaked coal samples exhibit a more developed pore structure when oxidized at 300 °C. 20 According to Zhong et al, upon air-drying a water-immersed coal specimen to its critical moisture level, where spontaneous combustion is most probable, the presence of hydroxyl and aliphatic group associations surpasses that of the original coal.…”

Section: Introductionmentioning

confidence: 99%

Study on Spontaneous Combustion Characteristics and Microstructure of Bituminous Coal under Water Immersion

Fan,

Li,

Zhang

et al. 2024

ACS Omega

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The stagnant water above the coal seam flows into the goaf, causing the goaf coal to be soaked by water for a long time. Compared with dry raw coal, water-soaked coal has a stronger tendency for spontaneous combustion, which poses a serious threat to mining operators. To unravel the impact of water immersion on coal's self-heating properties, an investigation was conducted employing techniques such as simultaneous thermogravimetric analysis/differential scanning calorimetry (TG/DSC), scanning electron microscopy (SEM), low-temperature nitrogen adsorption based on the BET theory, and Fourier transform infrared spectroscopy (FTIR). The variations in the characteristic temperature, microphysical structure, and active functional groups of bituminous coal with water immersion degrees of 10, 30, 50, and 100% were studied, and the experimental results showed that (1) during the initial stage of coal self-ignition oxidation, moisture can cause a delay in the characteristic temperature points of bituminous coal. When the degree of water saturation in bituminous coal reaches 100%, both the critical temperature (T 1 ) and the cracking temperature (T 2 ) peak at 48.14 and 205.06 °C, respectively. However, after the water evaporation phase is complete, water soaking promotes the spontaneous combustion of bituminous coal. (2) The number of pores and fractures in bituminous coal is positively correlated with the amount of water soaked, with the average pore diameter increasing from 10.124 nm in raw coal to 15.547 nm in the A 4 coal sample. Moreover, when the degree of water immersion reaches 100%, the proportion of mesopores and macropores increases to 38.89 and 19.95%, respectively. (3) Compared to untreated coal, the number of functional groups in watersoaked coal samples increases. With the increase in water immersion, the hydroxyl (−OH) content of raw coal and four kinds of bituminous coal with different degrees of immersion was 40.8, 41.3, 42, 43.9, and 42.9%, respectively, showing a trend of increasing first and then decreasing. When the degree of water immersion of bituminous coal is 50%, the natural tendency is the strongest. These findings contribute to elucidating the underlying mechanism of water immersion's impact on coal self-ignition, thereby holding significant implications for enhancing fire safety measures in mine working areas.

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Study on pore structure change and lean oxygen re-ignition characteristics of high-temperature oxidized water-immersed coal

Cited by 22 publications

References 20 publications

Influence of mudstone on coal spontaneous combustion characteristics and oxidation kinetics analysis

Influence of mudstone on coal spontaneous combustion characteristics and oxidation kinetics analysis

DL‐malic acid for inhibiting the re‐ignition of long‐flame coal and its micro‐reaction mechanism

Study on Spontaneous Combustion Characteristics and Microstructure of Bituminous Coal under Water Immersion

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