Multiscale thermal behavioral characterization of spontaneous combustion of pre-oxidized coal with different air exposure time

Wang, Kai; Hu, Lihong; Deng, Jun; Zhang, Yanni

doi:10.1016/j.energy.2022.125397

Cited by 55 publications

(8 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…According to previous studies, 24 − 26 the quantity of aromatic rings in the molecular structure of coal has no effect on the formation of gaseous products. The coal–oxygen recombination reaction occurs between active groups and oxygen molecules and the main active sites in coal are located within aliphatic groups.…”

Section: Quantum Chemical Calculationsmentioning

confidence: 92%

Study on the Formation Mechanism of Acetaldehyde during the Low-Temperature Oxidation of Coal

Wang

Zhou

et al. 2022

ACS Omega

View full text Add to dashboard Cite

The threshold dilution ratio of acetaldehyde is much larger than those of other odor compounds generated during the spontaneous combustion process and so it is the most important odorant. Studying the mechanism by which acetaldehyde is generated can provide the necessary theoretical support for acetaldehyde-based odor analysis. In the present work, the release of acetaldehyde was monitored while heating lignite, long-flame coal, and coking coal specimens under either air or nitrogen. The data show that acetaldehyde was primarily produced by the oxidation of active sites in the coal rather than by the pyrolysis of oxygen-containing functional groups. Based on quantum chemistry and coal−oxygen reaction theory, the transition state approach was used to further study the formation of acetaldehyde during the low-temperature oxidation of coal. Using density functional theory, three different coal molecule structures were modeled and optimized structures for acetaldehyde formation and the energies, bond lengths, and virtual frequencies of each reaction stagnation point were obtained at the B3LYP-D3/6-311G** and M062X-D3/Def2-TZVP levels. The results indicate that the low-temperature oxidation of coal to generate acetaldehyde involves the capture of H atoms from aliphatic side chains to generate peroxy radicals. These radicals then attack unsaturated C atoms through complex inversions to generate peroxides. In the third step of this process, the O−O single bonds in the peroxides break in response to thermal energy to form carbonyl groups. Finally, specific C−C or C−O bonds on the aliphatic side chains are thermally cleaved to generate acetaldehyde.

show abstract

Section: Quantum Chemical Calculationsmentioning

confidence: 92%

Study on the Formation Mechanism of Acetaldehyde during the Low-Temperature Oxidation of Coal

Wang

Zhou

et al. 2022

ACS Omega

View full text Add to dashboard Cite

show abstract

“…After soaking in water, the volume of the original coal sample expands, the cracks and pores become more developed in the drying process, and the oxygen absorption is greater than that of the dry coal sample [11]. After soaking and drying, the pore volume and the specific surface area of the mesopore and micropore decrease, while the pore volume and the specific surface area of the mesopore and macropore increase, and the average pore size increases greatly, leading to the development of pore channels in coal, enhanced connectivity, enhanced oxygen adsorption and circulation capacity, enhanced oxidation capacity, and an increased risk of spontaneous combustion [12][13][14].…”

Section: Introductionmentioning

confidence: 96%

Study of the Effect of Drying on the Pore Structure and Rate of Oxygen Consumption and Heat Release of Immersed Lignite

et al. 2023

View full text Add to dashboard Cite

To reveal the influence mechanism of the drying process of immersed coal on the spontaneous combustion characteristics, we measured the pore structure of coal with low-field nuclear magnetic resonance and conducted the temperature-programmed spontaneous combustion experiment. The results showed that the pore volume content of the pores with pore sizes of less than 100 nm was significantly reduced. The diameter range of 100–1000 nm was gradually generated after 8 h of coal drying, and the proportion of large pores and cracks larger than 1000 nm increased significantly during the drying process of the immersed coal. The oxygen consumption rate and the heat release rate were significantly affected by the degree of dryness and the temperature of coal samples in the temperature-programmed process. The turning point temperature was 140°C; below the turning point temperature, the raw coal had the fastest oxygen consumption and maximum heat release. When the coal temperature was higher than 140°C, the oxygen consumption rate and the heat release rate of the coal sample that was dried for 24 h were higher than those for the raw coal, followed by the samples that were dried for 8 h and dried for 48 h. The main reason is that the water content of the coal sample decreases to 11.4% and the porosity increases to 16.5% after drying for 24 h, while the proportion of pores or cracks larger than 1000 nm increases significantly to 87.17%, the largest increase range and the pore connectivity will reach the maximum.

show abstract

“…Coal spontaneous combustion in goaf is one of the main hazards that affect the safety of mine production. , The temperature rise and oxidation of coal spontaneous combustion in goaf is the result of the heat generated by the physical and chemical reactions between the air leakage of the working face and the residual coal in goaf . In the process of mine production, it is the premise of effective prevention and control of coal spontaneous combustion to determine the location of the high-temperature area and points of coal spontaneous combustion in goaf timely and accurately.…”

Section: Introductionmentioning

confidence: 99%

Study on Multifield Migration and Evolution Law of the Oxidation Heating Process of Coal Spontaneous Combustion in Dynamic Goaf

Lei

Jiang

Bao³

et al. 2023

ACS Omega

View full text Add to dashboard Cite

To study the dynamic evolution law of the oxidation heating process of coal spontaneous combustion in the goaf during the advancing process of the working face, a dynamic model of oxidation heating of coal spontaneous combustion in the goaf was established on the basis of deformed geometry. Through numerical simulation research, the evolution and migration laws of seepage field, oxygen concentration field, temperature field, and high-temperature area of coal spontaneous combustion in the goaf during the advancement of the working face was obtained. The results indicate that the distribution of the bulking coefficient, porosity, and permeability of the falling coal and rock mass in the goaf is nonuniform. They are relatively large in the area near the working face and the inlet and return airway and remain relatively unchanged with the advancement of the working face, but they are constantly decreasing in the location of the gob in the middle and deep. The oxygen concentration in the goaf presents an asymmetrical distribution. The oxygen concentration distribution area on the inlet side is wider than that on the return air side. At the same depth of the goaf, the oxygen concentration gradually decreases from the inlet side to the return air side; after the advancement distance exceeds 200 m, the air leakage in the goaf basically disappears, and the oxygen concentration decreases to zero. The high-temperature area of coal spontaneous combustion oxidation in the goaf was mainly concentrated on the air inlet side and extended toward the return air side. The advancing speed has a significant effect on the oxidation heating process of coal spontaneous combustion in the dynamic goaf. Under the same propulsion distance, when the advancing speed is 6 m/day, the highest temperature in the goaf is about 40 °C, and when the advancing speed is 2 m/day, the highest temperature in the goaf is as high as 120 °C. The smaller the advancing speed, the higher the heating rate of the goaf and the closer the high-temperature area to the working surface. The higher the advancing speed, the lower the temperature of the high-temperature point of the goaf and the greater the depth of the high-temperature point of the high temperature area; when the advancing speed is 2 m/day, the highest temperature point in the goaf is 70 m away from the working face, whereas when the advancing speed is 6 m/day, it reaches 174.6 m.

show abstract

Multiscale thermal behavioral characterization of spontaneous combustion of pre-oxidized coal with different air exposure time

Cited by 55 publications

References 48 publications

Study on the Formation Mechanism of Acetaldehyde during the Low-Temperature Oxidation of Coal

Study on the Formation Mechanism of Acetaldehyde during the Low-Temperature Oxidation of Coal

Study of the Effect of Drying on the Pore Structure and Rate of Oxygen Consumption and Heat Release of Immersed Lignite

Study on Multifield Migration and Evolution Law of the Oxidation Heating Process of Coal Spontaneous Combustion in Dynamic Goaf

Contact Info

Product

Resources

About