Effects of pre-oxidation temperature on coal secondary spontaneous combustion

Wang, Kai; Liu, Xiangrong; Deng, Jun; Zhang, Yanni; Jiang, Shangrong

doi:10.1007/s10973-019-08138-3

Cited by 53 publications

(16 citation statements)

References 22 publications

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“…Through experimental studies, these authors also expressed that the thermal diffusion coefficient of the oxidized coal increased linearly with an increase in the pre-oxidation temperature. Wang et al , concluded that the pre-oxidation temperature exhibited a significant dual impact of first inhibition and then promotion of the secondary coal oxidation through a temperature-programmed experimental system and a C 80 microcalorimeter, which was consistent with the research result of Jo . Wang et al also discussed the influence of the pre-oxidation degree on the coal spontaneous combustion parameters, and their study revealed that the pre-oxidation process exhibited positive and inhibitive impact on the spontaneous combustion parameters during the initial and later stages of the coal–oxygen composite reaction, respectively.…”

Section: Introductionsupporting

confidence: 53%

Combustion Kinetics and Mechanism of Pre-Oxidized Coal with Different Oxygen Concentrations

et al. 2021

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The phenomenon of spontaneous combustion of “oxidized coal” is common in mining processes of goafs, thick coal seams, and unsealing of closed fire areas. In order to study the reburning characteristics of coal with different oxidation degrees, the oxygen concentration in the pre-oxidation process was selected as the key influencing factor. Thermogravimetric analysis (TGA) and in situ Fourier-transform infrared (FT-IR) spectroscopy were used to study the macro- and microcharacteristics of raw and oxidized coal during the combustion stage. The results showed that the pre-oxidation treatment exhibited a dual effect on promoting and inhibiting the weight loss characteristics of oxidized coal. The apparent activation energy, E a, of the combustion reaction for the utilized coal samples was calculated using the Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods, and it was found that the average apparent activation energy (E a̅) values of the oxidized coal samples were less in magnitude than that of the raw coal and that the coal sample with the pre-oxidized oxygen concentration of 15% was more prone to the combustion reaction. Using the correlation determination method of key active groups in the proposed coal combustion reaction, the key active groups affecting the weight change of the tested coal samples during the combustion stage were determined as −CH3 and C–O. The results can be helpful to prevent and control coal spontaneous combustion during re-mining and unsealing of closed fire areas.

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Section: Introductionsupporting

confidence: 53%

Combustion Kinetics and Mechanism of Pre-Oxidized Coal with Different Oxygen Concentrations

et al. 2021

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“…25 According to the change in the oxygen volume fraction at the outlet under each temperature gradient, the changes in the oxygen volume fraction and the oxygen consumption rate at the outlet of the briquettes under different axial compression strengths are shown in Figure 2 a,b. The formula for the oxygen consumption rate 26 is as follows …”

Section: Experimental Results and Analysismentioning

confidence: 99%

Characteristics for Oxygen-Lean Combustion and Residual Thermodynamics in Coalfield-Fire Zones within Axial Pressure

Chen

et al. 2020

ACS Omega

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Coalfield fires during coal mining have become a major problem in the world today. To effectively prevent such disasters, we established an experimental platform to measure the spontaneous combustion characteristics of large-scale pressurized coal; thermal analysis experiments and microscopic analysis of briquettes under different axial pressures were carried out. It can be seen from the results that when the axial pressure is 4 MPa, the heating rate of the oxidative combustion of coal samples is accelerated, the crossing point temperature is lower (reduced by 71.09 °C), the activation energy is reduced (the second stage is decreased by 21.3 kJ/mol), and the oxidative combustion is more intense. Simultaneously, the porosity evolution process of briquettes under different axial pressures is simulated. Through calculation, it can be seen that the porosity and thermal conductivity show a linear increasing trend. The basis for the increase in the internal oxygen supply channels and increase in oxygen consumption when the axial pressure is 4 MPa is given. Through thermogravimetric–differential scanning calorimetry analysis, it is found that the maximum mass loss rate and maximum mass growth rate of residual coal after combustion under an axial pressure of 4 MPa are low, the residual rate after combustion is large, and the flammability rate is low when reoxidized, while complete combustion oxidation releases more heat. The application of axial pressure will change the combustion characteristics of briquettes, and the promotion effect is more obvious at 4 MPa. Analyzing the laws of the coal–oxygen composite reaction under different axial pressures provides theoretical guidance for the prevention and control of multistress coupling fields in coalfield-fire areas.

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“…However, human entry into the goaf is particularly difficult, and both the source of the fire and the location of the hightemperature areas are well concealed. Current monitoring methods are unable to meet the requirements for the prevention of spontaneous coal combustion [4,5]; consequently, numerical simulations are used to realize the occurrence and development of this phenomenon. The relationship between the advancement of the working face and the risk distribution of the spontaneous combustion of coal within the goaf is analyzed to provide theoretical guidance for the prediction and control of the spontaneous combustion of coal within the goaf area.…”

Section: Introductionmentioning

confidence: 99%

Distribution law for the danger area for spontaneous coal combustion in a dynamic goaf with low air leakage speed

Zuo

Wang

2021

Therm sci

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This paper examines the relationship between the advancement of the working face and the distribution of spontaneous coal combustion under a low air leakage wind speed in a goaf. Based on the unsteady state simulation method, the process of spontaneous coal combustion was simulated in a fully mechanized coal mining face at different advancing speeds. The relationship between different advancing speeds and the distribution area of the oxidation zone of spontaneous coal combustion in a goaf was clarified. A safe advancing speed was determined. Furthermore, the advancement of the working face altered the area of spontaneous high temperature inside the goaf. An increase in the advancing speed increased the length of time of spontaneous combustion in the leftover coal. An exponential relationship was demonstrated between the spontaneous combustion area and the advancement of the fully mechanized mining face. When the oxygen concentration was used as a calculation indicator, the width of the oxidation zone was asymmetrical on the inlet and outlet, and the advancing distance of the working surface increased when the distance was shorter than 90 m and the return side was smaller than the inlet side. When the advancing distance was longer than 90 m, the width of the spontaneous combustion oxidation zone distribution remained unchanged. The study clarified the relationship between the distribution of the danger area for spontaneous coal combustion and advancing speed. This could provide a theoretical basis for the prevention and control technology of the spontaneous combustion of broken coal in a dynamic goaf.

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Effects of pre-oxidation temperature on coal secondary spontaneous combustion

Cited by 53 publications

References 22 publications

Combustion Kinetics and Mechanism of Pre-Oxidized Coal with Different Oxygen Concentrations

Combustion Kinetics and Mechanism of Pre-Oxidized Coal with Different Oxygen Concentrations

Characteristics for Oxygen-Lean Combustion and Residual Thermodynamics in Coalfield-Fire Zones within Axial Pressure

Distribution law for the danger area for spontaneous coal combustion in a dynamic goaf with low air leakage speed

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