Influencing patterns of low-temperature nitrogen on the pore structure and oxidation characteristics of lignite
ObjectiveDuring fire prevention and extinguishment for mines, injecting normal-temperature nitrogen into goaves can only play an inerting role. Meanwhile, the preparation of liquid nitrogen is complicated and costly. Therefore, in the Wudong Coal Mine in Xinjiang, low-temperature gaseous nitrogen of...
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Editorial Office of Coal Geology & Exploration
2025-06-01
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| Series: | Meitian dizhi yu kantan |
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| author | Shuliang XIE Gang WANG Qingdong QU Hao LIU Lulu SUN |
| author_facet | Shuliang XIE Gang WANG Qingdong QU Hao LIU Lulu SUN |
| author_sort | Shuliang XIE |
| collection | DOAJ |
| description | ObjectiveDuring fire prevention and extinguishment for mines, injecting normal-temperature nitrogen into goaves can only play an inerting role. Meanwhile, the preparation of liquid nitrogen is complicated and costly. Therefore, in the Wudong Coal Mine in Xinjiang, low-temperature gaseous nitrogen of −40 ℃ was prepared using nitrogen cooling devices and then injected into goaves to prevent the spontaneous combustion of residual coals. However, the influencing patterns of low-temperature nitrogen on the pore structures and oxidation characteristics of residual coals in goaves remain poorly understood. This tends to affect the prediction and forecast of the secondary oxidation of residual coals in goaves after low-temperature nitrogen injection ends. MethodsUsing experiments with an ultra-depth 3D digital microscope and a confocal laser scanning microscope (CLSM), nitrogen adsorption experiments, and temperature-programmed heating experiments, this study examined the surface morphologies, pore structures, and oxidation characteristic parameters of coals following sample processing using low-temperature nitrogen. Results and Conclusions After being processed using low-temperature nitrogen, the surface structures of coal samples were destroyed. With an increase in the processing time, the coal samples exhibited more developed reticular pore structures, and coal sample surfaces displayed distinct undulations. The arithmetic mean height of various points on the surfaces gradually increased from 9.562 1 μm to 21.904 5 μm, with an increase of 1.29 times. Concurrently, the average height difference of all undulations rose from 81.321 0 μm to 193.146 5 μm, representing an increase of 1.36 times. Low-temperature nitrogen primarily affected the distribution of micropores and mesopores in the coal samples, especially 2-4 nm mesopores. With an increase in the sample processing time, micropores in the samples trended upward and then downward, while mesopores therein showed an opposite trend. As a result, the total pore volume increased by 0.004 3 cm3/g, with the 2-10 nm mesopores identified as the largest contributor, and the specific surface area of coal samples determined using the Brunauer–Emmett–Teller (BET) theory increased by 0.049 3 m2/g. After sample processing using low-temperature nitrogen, the CO production, heat release intensity, and oxygen consumption rates significantly increased during coal sample oxidation. Notably, their increments increased with the sample processing time. Specifically, the CO production, oxygen consumption rate, and maximum heat release intensity increased by 5.02×104 μL/L at maximum, 2.33×10−8 mol/(cm3·s), and 2.25×10−2 J/(cm3·s), respectively. Additionally, the characteristic temperature of oxidation reactions in the coal samples decreased. The results of this study reveal that low-temperature nitrogen can destroy the pore structures of coals and enhance their oxidation performance. In the case where low-temperature nitrogen of −40 ℃ is injected into a goaf, its macroscopic dominant effect of inerting and cooling can effectively suppress the spontaneous combustion of coals. When oxygen is restored after nitrogen injection ends, coals show a higher tendency for spontaneous combustion after being treated due to the microscopic side effect of low-temperature nitrogen, enhancing the secondary oxidation intensity. |
| format | Article |
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| institution | Kabale University |
| issn | 1001-1986 |
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| publishDate | 2025-06-01 |
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| spelling | doaj-art-b46ab1d4640d4669953d3c3eccfadacf2025-08-20T03:27:02ZzhoEditorial Office of Coal Geology & ExplorationMeitian dizhi yu kantan1001-19862025-06-0153616918010.12363/issn.1001-1986.25.03.018125-03-0181-Xie-ShuliangInfluencing patterns of low-temperature nitrogen on the pore structure and oxidation characteristics of ligniteShuliang XIE0Gang WANG1Qingdong QU2Hao LIU3Lulu SUN4College of Safety and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Safety and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaThe Commonwealth Scientific and Industrial Research Organisation, Queensland 4069, AustraliaCollege of Safety and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Safety and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaObjectiveDuring fire prevention and extinguishment for mines, injecting normal-temperature nitrogen into goaves can only play an inerting role. Meanwhile, the preparation of liquid nitrogen is complicated and costly. Therefore, in the Wudong Coal Mine in Xinjiang, low-temperature gaseous nitrogen of −40 ℃ was prepared using nitrogen cooling devices and then injected into goaves to prevent the spontaneous combustion of residual coals. However, the influencing patterns of low-temperature nitrogen on the pore structures and oxidation characteristics of residual coals in goaves remain poorly understood. This tends to affect the prediction and forecast of the secondary oxidation of residual coals in goaves after low-temperature nitrogen injection ends. MethodsUsing experiments with an ultra-depth 3D digital microscope and a confocal laser scanning microscope (CLSM), nitrogen adsorption experiments, and temperature-programmed heating experiments, this study examined the surface morphologies, pore structures, and oxidation characteristic parameters of coals following sample processing using low-temperature nitrogen. Results and Conclusions After being processed using low-temperature nitrogen, the surface structures of coal samples were destroyed. With an increase in the processing time, the coal samples exhibited more developed reticular pore structures, and coal sample surfaces displayed distinct undulations. The arithmetic mean height of various points on the surfaces gradually increased from 9.562 1 μm to 21.904 5 μm, with an increase of 1.29 times. Concurrently, the average height difference of all undulations rose from 81.321 0 μm to 193.146 5 μm, representing an increase of 1.36 times. Low-temperature nitrogen primarily affected the distribution of micropores and mesopores in the coal samples, especially 2-4 nm mesopores. With an increase in the sample processing time, micropores in the samples trended upward and then downward, while mesopores therein showed an opposite trend. As a result, the total pore volume increased by 0.004 3 cm3/g, with the 2-10 nm mesopores identified as the largest contributor, and the specific surface area of coal samples determined using the Brunauer–Emmett–Teller (BET) theory increased by 0.049 3 m2/g. After sample processing using low-temperature nitrogen, the CO production, heat release intensity, and oxygen consumption rates significantly increased during coal sample oxidation. Notably, their increments increased with the sample processing time. Specifically, the CO production, oxygen consumption rate, and maximum heat release intensity increased by 5.02×104 μL/L at maximum, 2.33×10−8 mol/(cm3·s), and 2.25×10−2 J/(cm3·s), respectively. Additionally, the characteristic temperature of oxidation reactions in the coal samples decreased. The results of this study reveal that low-temperature nitrogen can destroy the pore structures of coals and enhance their oxidation performance. In the case where low-temperature nitrogen of −40 ℃ is injected into a goaf, its macroscopic dominant effect of inerting and cooling can effectively suppress the spontaneous combustion of coals. When oxygen is restored after nitrogen injection ends, coals show a higher tendency for spontaneous combustion after being treated due to the microscopic side effect of low-temperature nitrogen, enhancing the secondary oxidation intensity.http://www.mtdzykt.com/article/doi/10.12363/issn.1001-1986.25.03.0181coal spontaneous combustionlow-temperature nitrogensurface morphologypore structureoxidation characteristic |
| spellingShingle | Shuliang XIE Gang WANG Qingdong QU Hao LIU Lulu SUN Influencing patterns of low-temperature nitrogen on the pore structure and oxidation characteristics of lignite Meitian dizhi yu kantan coal spontaneous combustion low-temperature nitrogen surface morphology pore structure oxidation characteristic |
| title | Influencing patterns of low-temperature nitrogen on the pore structure and oxidation characteristics of lignite |
| title_full | Influencing patterns of low-temperature nitrogen on the pore structure and oxidation characteristics of lignite |
| title_fullStr | Influencing patterns of low-temperature nitrogen on the pore structure and oxidation characteristics of lignite |
| title_full_unstemmed | Influencing patterns of low-temperature nitrogen on the pore structure and oxidation characteristics of lignite |
| title_short | Influencing patterns of low-temperature nitrogen on the pore structure and oxidation characteristics of lignite |
| title_sort | influencing patterns of low temperature nitrogen on the pore structure and oxidation characteristics of lignite |
| topic | coal spontaneous combustion low-temperature nitrogen surface morphology pore structure oxidation characteristic |
| url | http://www.mtdzykt.com/article/doi/10.12363/issn.1001-1986.25.03.0181 |
| work_keys_str_mv | AT shuliangxie influencingpatternsoflowtemperaturenitrogenontheporestructureandoxidationcharacteristicsoflignite AT gangwang influencingpatternsoflowtemperaturenitrogenontheporestructureandoxidationcharacteristicsoflignite AT qingdongqu influencingpatternsoflowtemperaturenitrogenontheporestructureandoxidationcharacteristicsoflignite AT haoliu influencingpatternsoflowtemperaturenitrogenontheporestructureandoxidationcharacteristicsoflignite AT lulusun influencingpatternsoflowtemperaturenitrogenontheporestructureandoxidationcharacteristicsoflignite |