Effects of imidazole ionic liquid on macroparameters and microstructure of bituminous coal during low-temperature oxidation

Deng, Jun; Bai, Zujin; Shu, Chi‐Min; Laiwang, Bin

doi:10.1016/j.fuel.2019.02.066

Cited by 64 publications

(10 citation statements)

References 27 publications

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“…Table 5 lists the functional groups detected through the in situ infrared analysis of coal samples 19 . Figure 6 a,b show the spectra of the samples with different particle sizes and of a sample heated to different temperatures, respectively.…”

Section: Resultsmentioning

confidence: 99%

Investigation of the kinetics of spontaneous combustion of the major coal seam in Dahuangshan mining area of the Southern Junggar coalfield, Xinjiang, China

Zeng

2021

Sci Rep

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In the present paper, with using diverse methods (including the SEM, the XRD, the TPO, the FTIR, and the TGA) , the authors analysed samples of the major coal seam in Dahuangshan Mining area with different particle sizes and with different heated temperatures (from 50 to 800 °C at regular intervals of 50 °C). The results from SEM and XRD showed that high temperature and high number of pores, fissures, and hierarchical structures in the coal samples could facilitate oxidation reactions and spontaneous combustion. A higher degree of graphitization and much greater number of aromatic microcrystalline structures facilitated spontaneous combustion. The results from TPO showed that the oxygen consumption rate of the coal samples increased exponentially with increasing temperature. The generation rates of different gases indicated that temperatures of 90 °C or 130 °C could accelerate coal oxidation. With increasing temperature, the coal oxidation rate increased, and the release of gaseous products was accelerated. The FTIR results showed that the amount of hydroxide radicals and oxygen-containing functional groups increased with the decline in particle size, indicating that a smaller particle size may facilitate the oxidation reaction and spontaneous combustion of coal. The absorbance and the functional group areas at different particle sizes were consistent with those of the heated coal samples, which decreased as the temperature rose. The results from TGA showed that the characteristic temperature T3 declined with decreasing particle size. After the sample with 0.15–0.18 mm particle size was heated, its carbon content decreased, and its mineral content increased, inhibiting coal oxidation. This result also shows that the activation energy of the heated samples tended to increase at the stage of high-temperature combustion with increasing heating temperature.

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Section: Resultsmentioning

confidence: 99%

Investigation of the kinetics of spontaneous combustion of the major coal seam in Dahuangshan mining area of the Southern Junggar coalfield, Xinjiang, China

Zeng

2021

Sci Rep

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“…A vibrating screen is used to screen the coal samples with different crushing degrees, and coal samples with particle sizes between 0.1 and 0.15 mm are selected for the experiment. A temperature-programmed device was used to oxidize raw coal and details of the device can be found in a previous study. , The mass of the coal sample was 100 g, the heating rate was 1 °C/min, the flow rate of the experimental gas was 50 mL/min, and the gas composition was dry air, that is, the volume fraction of oxygen was 21%. The gas produced by oxidation in the coal sample tank was extracted at 10 °C intervals and the composition and content of the gas were analyzed through gas chromatography.…”

Section: Samples and Experimentsmentioning

confidence: 99%

Study on the Variations of Key Groups and Thermal Characteristic Parameters during Coal Secondary Spontaneous Combustion

2023

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To investigate the effect of preoxidation on the secondary spontaneous combustion of coal, the changes in the key groups and thermal characteristic parameters in coal after preoxidation were investigated through Fourier transform infrared spectroscopy (FTIR), laser thermal conductivity, and thermogravimetric experiments. Results showed that the aromatic hydrocarbons in coal gradually decrease with the rise in the preoxidation temperature, the aliphatic hydrocarbons increase and then decrease, the −C–O– group gradually decreases, and the −CO and −COO– group content slowly increases. Preoxidation promotes the breakdown of aromatic hydrocarbons and the oxidation of oxygen-containing functional groups in coal. Meanwhile, the thermal diffusivity of coal decreases after preoxidation, while the specific heat capacity and thermal conductivity increase and then decrease. The results of the thermogravimetric analysis indicate that preoxidation changes the characteristic temperature, but it does not change the process of spontaneous combustion. The spontaneous combustion process of raw and preoxidized coals can be divided into three stages: water evaporation, oxygen adsorption, and combustion. Further, the apparent activation energy increases and then decreases with a rise in the preoxidation temperature during the moisture evaporation stage, increases during the oxygen adsorption stage, and decreases during the combustion stage.

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“…In further research on the inhibiting effect of ILs on CSC, it was shown that the inhibiting effect of different ILs on coal was variable. In addition, through experimental comparison, it was further demonstrated that [BMIM][BF 4 ] with a content of 5% had the strongest CSC inhibitory effect, and that those effects differed according to coal grade [35][36][37].…”

Section: Introductionmentioning

confidence: 99%

Testing inhibitory effects of a panel of ionic liquids on differing phases of coal spontaneous combustion

Xiao

Zhang

et al. 2021

J Therm Anal Calorim

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Coal spontaneous combustion (CSC) is a major safety concern affecting not just miners and businesses, but of industry in China generally. Chemical methods are already widely applied in the field of CSC prevention and plays a vital role in suppressing its negative effects. Ionic liquids (ILs) are novel and environmentally friendly solvents that have shown possible inhibitory effects on CSC through controlling the reactive groups in coal's molecular structure. To study the effects of various ILs on CSC more thoroughly, this paper examined several types of IL that had been pre-treated for different periods and examined how they performed during different phases of the combustion process. A long flame coal type was selected and immersed in four ILs [BMIM][BF 4 ], [BMIM][NO 3 ], [BMIM][I], and [EMIM][BF 4 ]. Immersion periods were 2 days, 3 months, and 6 months; a raw coal sample was retained as a control. LFA 457 laser-flash apparatus determined the thermophysical properties of the samples between 30 and 300 °C. The kinetic process of the samples (30-800 °C) was deduced by thermogravimetric-differential scanning calorimetry thermal at various heating rates (2, 5, 10, and 15 °C min −1 ), and the thermal effect parameters were obtained. Results from this paper show that immersion treatment using ILs has an inhibitory effect on CSC, and the reliability of the thermophysical parameters was verified by uncertainty analysis. The pre-treated samples characteristics and exothermic peak temperature with different degrees of hysteresis were recorded, and statistical analysis verified the conclusions from the thermal physics experiments. The pre-treated sample with the greatest lag over various stages was found, and the apparent activation energy (E a ) of its rapid oxidation stage was calculated by Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods. Meanwhile, the two kinetic methods confirm each other and come to a conclusion after joint verification. The greatest E a found here was for a 6-month immersion coal sample using the IL [BMIM][BF 4 ].

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Effects of imidazole ionic liquid on macroparameters and microstructure of bituminous coal during low-temperature oxidation

Cited by 64 publications

References 27 publications

Investigation of the kinetics of spontaneous combustion of the major coal seam in Dahuangshan mining area of the Southern Junggar coalfield, Xinjiang, China

Investigation of the kinetics of spontaneous combustion of the major coal seam in Dahuangshan mining area of the Southern Junggar coalfield, Xinjiang, China

Study on the Variations of Key Groups and Thermal Characteristic Parameters during Coal Secondary Spontaneous Combustion

Testing inhibitory effects of a panel of ionic liquids on differing phases of coal spontaneous combustion

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