The heat of wetting and its effect on coal spontaneous combustion

Pan, Rongkun; Hu, Daimin; Chao, Jiangkun; Wang, Liang; Ma, Junwei; Jia, Hailin

doi:10.1016/j.tca.2020.178711

Cited by 38 publications

(12 citation statements)

References 27 publications

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“…Wettability is an important physical parameter defined as “the tendency of one fluid to spread on or adhere to a solid surface in the presence of other immiscible fluids”. − Experimental methods for measuring the wettability of reservoirs include contact angle (CA) measurements, the Amott wettability index, the USBM wettability index, the spontaneous imbibition (SI) rate/volume, and NMR . However, with the development of modern analytical techniques, calorimetry can be applied to study the rock wettability, and the wetting heat can be used as an evaluation index of rock wettability. − The principle of the calorimetry experiment is to evaluate the wettability based on the value of heat released or absorbed due to the change in energy in the process of rock being wetted by water or oil, which has a higher accuracy and certain feasibility . When the value of wetting heat is greater than zero, it represents exothermic heat and shows a positive wetting effect; otherwise, it means endothermic heat and shows a negative wetting effect.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Measurement of Shale Wettability Using Calorimetry: Experimental Results and Model

Chen

Zhang

et al. 2021

Energy Fuels

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Wettability affects the occurrence and exploitation of gas and oil in shale matrices; however, conventional methods for shale wettability evaluation (i.e., contact angle testing, imbibition method, flotation testing, surface tension method, and so forth) have limitations, which, in turn, lead to ambiguous or even contradictory results. Thus, in this paper, the calorimetry method is introduced to evaluate the wettability of shale, and the feasibility of the calorimetry method is discussed. The results show that transitional shale can be classified as mixed wet or more water wet in the southern North China Basin, and the calorimetry method exhibits higher accuracy and applicability. By considering the influence of the interaction between different factors on wettability, a geological prediction model of transitional shale wettability is established, which is helpful for the wettability evaluation of transitional shale and provides theoretical support for the exploitation of unconventional gas and oil. Oil wetting is mainly affected by pyrite and mixed layer illite−smectite (strongly positive influence), whereas water wetting is mainly affected by pyrite (negative influence), dolomite, and siderite (positive influence). The relative wettability index, wetting heat, heat flow rate, and other parameters derived from the calorimetric experiments can be used to evaluate wettability, which can provide theoretical support for the exploitation of unconventional gas and oil.

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Section: Introductionmentioning

confidence: 99%

“…Wang et al (2017) used a C80 calorimeter to reveal the complex contribution of the surface hydrophilicity of oxygen functional groups that influence the wetting heat from the wetting process of highly volatile bituminous coal. Pan et al (2020) found that the wetting heat increased as the temperature and particle size decreased.…”

Section: Introductionmentioning

confidence: 99%

Measurement of Shale Wettability Using Calorimetry: Experimental Results and Model

Chen

Zhang

et al. 2021

Energy Fuels

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“… 23 − 25 Pan et al found that the influence of moisture on spontaneous coal combustion is primarily reflected by changes in oxygen-containing functional groups. 26 …”

Section: Introductionmentioning

confidence: 99%

Effect of Water Evaporation on the Inhibition of Spontaneous Coal Combustion

et al. 2022

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Spontaneous coal combustion is the primary cause of coal mine fires. During the production process, spontaneous coal combustion in the goaf is often affected by air leakage, which weakens or annuls the effect of inhibitors and leads to secondary oxidation. However, the action mechanism of inhibitors on secondary oxidation spontaneous coal combustion remains unclear. Thus, this study analyzes the influence of moisture evaporation on the performance of a high-water-content physical inhibitor (HWPI) using the Carbolite temperature-programmed experiment, differential scanning calorimetry, scanning electron microscopy, and a MINI MR test. The results demonstrate that as the moisture content of the inhibitor decreased, after being treated with the HWPI and drying for 24 h, the concentrations of O 2 , CO, and CO 2 were found to be lower than the gas concentration of raw coal, which showed that although the moisture content is reduced, the treated coal sample still has a lower spontaneous combustion tendency than the raw coal. The apparent activation energy was reduced, and the heat absorption per unit time decreased, which eventually weakened or annulled the effect of the HWPI. Future research should further improve existing inhibitor types to reduce the impact of secondary oxidation on spontaneous coal combustion caused by water evaporation.

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“… 31 − 33 With the decrease in the particle size, the moisture content, the heat of wetting release, and the risk of spontaneous combustion increase. 34 Therefore, it is insufficient to use noncoal reference samples in the experiments of low-rank coal, especially for high-moisture-content coal. 35 , 36 …”

Section: Introductionmentioning

confidence: 99%

“…As is well-known, coal has a complex amorphous structure, and the amorphous structure is significantly affected by water immersion or loss. The change of the structure will significantly change the spontaneous combustion characteristics of coal. − With the decrease in the particle size, the moisture content, the heat of wetting release, and the risk of spontaneous combustion increase . Therefore, it is insufficient to use noncoal reference samples in the experiments of low-rank coal, especially for high-moisture-content coal. , …”

Section: Introductionmentioning

confidence: 99%

Rapid Contrastive Experimental Study on the Adiabatic Spontaneous Combustion Period of Loose Lignite

et al. 2021

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The adiabatic spontaneous combustion period of coal is an important index for the macroscopic characterization of coal spontaneous combustion, and it is affected by many internal and external factors. There are several methods to study it, but there are various shortcomings to these methods. Some require too much time, while others have too many interfering factors. To quickly obtain the accurate adiabatic spontaneous combustion period of coal, a rapid contrastive experimental method was designed. In this method, the coal samples of the experimental and control groups were the same, and air and nitrogen were used as control atmospheres. A theoretical calculation method for the adiabatic spontaneous combustion period based on this method is proposed. The experimental results showed that during the temperature-programmed coal spontaneous combustion experiment, the increase in the coal temperature was due to physical and chemical heating. Physical heating is the heating effect of the temperature-programmed furnace body and the heated gas on the coal sample. Chemical heating includes oxidative exothermic heating promoted by physical and adiabatic oxidation heating. The adiabatic oxidative heat release can be determined by the oxidation heat release in the air atmosphere minus the oxidation heat release corresponding to the coal sample temperature in the nitrogen environment at the same period. The adiabatic spontaneous combustion period of coal can be calculated from the adiabatic oxidation heat release. Our results provide a rapid contrastive experimental method to quickly obtain the accurate adiabatic spontaneous combustion period of coal.

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The heat of wetting and its effect on coal spontaneous combustion

Cited by 38 publications

References 27 publications

Measurement of Shale Wettability Using Calorimetry: Experimental Results and Model

Measurement of Shale Wettability Using Calorimetry: Experimental Results and Model

Effect of Water Evaporation on the Inhibition of Spontaneous Coal Combustion

Rapid Contrastive Experimental Study on the Adiabatic Spontaneous Combustion Period of Loose Lignite

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