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Zhao JY, Chi ZL, Song JJ, Lu SP, Zhang YN, Lei CK, Shu CM. Study on the thermal behaviour of spontaneous combustion of open-pit minerals. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 929:172477. [PMID: 38621544 DOI: 10.1016/j.scitotenv.2024.172477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 03/28/2024] [Accepted: 04/12/2024] [Indexed: 04/17/2024]
Abstract
To study thermal behaviour during spontaneous combustion of an open-pit coal mine, mixed slag (coal, oil shale, and coal gangue) was taken as the research object. Laser thermal conductivity analyser and differential scanning calorimetry were used to test thermophysical parameters and heat release characteristics of the minerals. The parameters can be employed to calculate the apparent activation energy using the Arrhenius equation and evaluate the thermal behaviour of open-pit mixed slag. The results indicate that thermophysical parameters have stage characteristics. Thermal diffusivity and thermal conductivity of minerals, especially mixed slag, have a strong correlation with temperature. Heat flow of minerals exhibits five characteristic stages, and heat flow of the samples is consistent with the change in heating rate. During the heating process, thermal diffusivity and heat flow of the mixed slag are between those of a single mineral. Except for the mixed slag at 15 and 20 °C/min, the initial exothermic temperature of the other samples is mainly concentrated at 50-80 °C. Thermal energy release of the sample is mainly concentrated in the accelerated exothermic stage and rapid exothermic stage. Thermal energy release of mixed slag in rapid exothermic stage is always greater than that in accelerated exothermic stage, and the proportion of thermal energy release in these two stages exceeds 98 %. The apparent activation energy during the accelerated exothermic stage is lower, making it easier to release heat, and rapid exothermic stage is relatively high, which can readily lead to heat accumulation. Thermal analysis reveals that the thermal behaviour of mixed slag is significantly different from that of a single mineral. Its unique exothermic characteristics can provide a more accurate theoretical basis for the prevention and control of environmental pollution caused by slag spontaneous combustion.
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Affiliation(s)
- Jing-Yu Zhao
- School of Safety Science and Engineering, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China; Shaanxi Key Laboratory of Prevention and Control of Coal Fire, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China
| | - Zhao-Long Chi
- School of Safety Science and Engineering, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China; Shaanxi Key Laboratory of Prevention and Control of Coal Fire, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China
| | - Jia-Jia Song
- School of Safety Science and Engineering, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China; Shaanxi Key Laboratory of Prevention and Control of Coal Fire, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China.
| | - Shi-Ping Lu
- School of Safety Science and Engineering, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China; Shaanxi Key Laboratory of Prevention and Control of Coal Fire, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China
| | - Yan-Ni Zhang
- School of Safety Science and Engineering, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China; Shaanxi Key Laboratory of Prevention and Control of Coal Fire, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China
| | - Chang-Kui Lei
- School of Safety and Emergency Management Engineering, Taiyuan University of Technology, No. 79, Yingze West Street, Taiyuan, Shanxi 030024, PR China
| | - Chi-Min Shu
- Department of Safety, Health, and Environmental Engineering, National Yunlin University of Science and Technology, 123, University Rd., Sec. 3, Douliou, Yunlin 64002, Taiwan
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Yang X, Chu T, Wang L, Li H, Wang J, Yu M. Mechanochemical evolution of coal microscopic groups: A new pathway for mechanical forces acting on coal spontaneous combustion. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 925:171471. [PMID: 38458468 DOI: 10.1016/j.scitotenv.2024.171471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Revised: 02/29/2024] [Accepted: 03/02/2024] [Indexed: 03/10/2024]
Abstract
Coal spontaneous combustion (CSC) remains a significant threat to regional ecological environments. As coal mining operations extend deeper into the earth, the increasingly complex mechanical force conditions in deep-seated mines escalate the potential risk of CSC. Mechanical forces such as ground stress and mechanical cutting are traditionally believed to be linked to CSC through the following pathway: mechanical forces act → mechanical energy is input → mechanical crushing and pulverization occur → coal-oxygen contact area increases → CSC accelerates. Noteworthily, these forces do more than just physically break coal; they also trigger a mechanochemical effect (MCE) that alters coal's microscopic chemistry. However, an independent evaluation of its influence on CSC was lacking. This study characterized coal's microscopic chemical group responses to the MCE. It was found that the MCE led to the degradation of aliphatic side chains while enhancing the polycondensation of aromatic ring structures, indicating a synergistic effect. Additionally, an increase in oxygen-containing functional groups, such as alkyl/aryl ethers, suggested enhanced interactions of the coal microscopic groups with oxygen due to mechanical forces. Based on these findings, an MCE-modified coal macromolecular model was developed and molecular quantum mechanical calculations were conducted. The results indicated that the MCE boosted coal macromolecule reactivity, thus facilitating easier activation. These conclusions were validated through modern thermal analysis tests. Finally, this study proposed a new pathway of mechanical forces acting on CSC: mechanical forces act → mechanical energy is input → the MCE occurs → evolutions of the microscopic groups within coal are induced → Activity of coal molecules is enhanced → CSC accelerates.
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Affiliation(s)
- Xinlei Yang
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
| | - Tingxiang Chu
- School of Mine Safety, North China Institute of Science and Technology, Sanhe, Hebei 065201, China.
| | - Liang Wang
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
| | - Haitao Li
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
| | - Jiachen Wang
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
| | - Minggao Yu
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China.
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Liu Y, Qi X, Luo D, Zhang Y, Qin J. Detection of Spontaneous Combustion Areas of Coal Gangue Dumps and Comprehensive Governance Technologies: A Case Study. ACS OMEGA 2023; 8:47690-47700. [PMID: 38144064 PMCID: PMC10733915 DOI: 10.1021/acsomega.3c05942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/12/2023] [Revised: 11/16/2023] [Accepted: 11/24/2023] [Indexed: 12/26/2023]
Abstract
Spontaneous combustion of coal gangue dumps not only releases toxic and harmful gases, polluting the environment, but also leads to explosion accidents and casualties due to improper handling. This paper focuses on delineating the fire area, constructing a comprehensive fire prevention and extinguishing system, and restoring the ecological environment. Infrared thermal imaging was used to detect the shallow fire area, while intensive drilling was conducted to detect the deep fire area. The stability of the coal gangue dump was enhanced by perfusing three-phase foam for cooling and using a curing material to fill the cracks. Land reclamation was then performed to restore the ecological environment. The results indicate that spontaneous combustion of coal gangue dumps can trigger the spread of the fire area from the outside to the inside, gradually expanding due to the 'stack effect'. The sources of spontaneous combustion in gangue fire areas are mainly located 3-5 m below the flat surface, and the shallow and deep fire areas are interconnected, posing a significant danger. These research findings can serve as a reference for detecting fire areas in coal gangue dumps and controlling environmental pollution.
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Affiliation(s)
- Yang Liu
- School
of Safety Engineering, China University
of Mining and Technology, Xuzhou 221116, China
- School
of Resources and Security, Chongqing Vocational
Institute of Engineering, Chongqing 402260, China
| | - Xuyao Qi
- School
of Safety Engineering, China University
of Mining and Technology, Xuzhou 221116, China
| | - Dayong Luo
- School
of Resources and Security, Chongqing Vocational
Institute of Engineering, Chongqing 402260, China
| | - Yongqing Zhang
- School
of Resources and Security, Chongqing Vocational
Institute of Engineering, Chongqing 402260, China
| | - Jiangtao Qin
- School
of Resources and Security, Chongqing Vocational
Institute of Engineering, Chongqing 402260, China
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Pan R, Hu D, Chao J, Han X, Jia H, Li C. Oxidation and exothermic properties of long flame coal spontaneous combustion under solid-liquid-gas coexistence and its microscopic mechanism analysis. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 895:165206. [PMID: 37391137 DOI: 10.1016/j.scitotenv.2023.165206] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 06/26/2023] [Accepted: 06/27/2023] [Indexed: 07/02/2023]
Abstract
Coal spontaneous combustion (CSC) wastes valuable resources and does great damage to the environment. To study the oxidation and exothermic properties of CSC under solid-liquid-gas coexistence conditions, a C600 microcalorimeter was used to analyze the heat released by the oxidation of raw coal (RC) and water immersion coal (WIC) under different air leakage (AL) conditions. The experimental results showed that the AL was negatively correlated with the heat release intensity (HRI) in the initial stages of coal oxidation, but as the oxidation proceeded, the AL and the HRI gradually showed positive correlations. The HRI of the WIC was lower than that of the RC under the same AL conditions. However, since water participated in the generation and transfer of free radicals in the coal oxidation reaction and promoted the development of coal pores, the HRI growth rate of the WIC was higher than that of the RC during the rapid oxidation period, and the self-heating risk was higher. The heat flow curves for the RC and WIC in the rapid oxidation exothermic stage could be fitted with quadratic functions. The experimental results provide an important theoretical basis for the prevention of CSC.
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Affiliation(s)
- Rongkun Pan
- School of Safety Science & Engineering, Henan Polytechnic University, Jiaozuo 454003, China; Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization, Henan Polytechnic University, Jiaozuo 454003, China; Henan key laboratory of prevention and cure of mine methane & fires, Jiaozuo 454003, China.
| | - Daimin Hu
- School of Safety Science & Engineering, Henan Polytechnic University, Jiaozuo 454003, China
| | - Jiangkun Chao
- School of Safety Science & Engineering, Henan Polytechnic University, Jiaozuo 454003, China
| | - Xuefeng Han
- School of Safety Science & Engineering, Henan Polytechnic University, Jiaozuo 454003, China
| | - Hailin Jia
- School of Safety Science & Engineering, Henan Polytechnic University, Jiaozuo 454003, China; Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization, Henan Polytechnic University, Jiaozuo 454003, China; Henan key laboratory of prevention and cure of mine methane & fires, Jiaozuo 454003, China
| | - Cong Li
- School of Safety Science & Engineering, Henan Polytechnic University, Jiaozuo 454003, China
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Guo J, Zhang T, Pan H. Study on the Variations of Key Groups and Thermal Characteristic Parameters during Coal Secondary Spontaneous Combustion. ACS OMEGA 2023; 8:4176-4186. [PMID: 36743016 PMCID: PMC9893756 DOI: 10.1021/acsomega.2c07281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Accepted: 12/30/2022] [Indexed: 06/18/2023]
Abstract
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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Affiliation(s)
- Jiangbo Guo
- College
of Safety Science and Engineering, Xi’an
University of Science and Technology, Xi’an710054, China
- Key
Laboratory of Western Mine Exploitation and Hazard Prevention of the
Ministry of Education, Xi’an710054, China
| | - Tianjun Zhang
- College
of Safety Science and Engineering, Xi’an
University of Science and Technology, Xi’an710054, China
- Key
Laboratory of Western Mine Exploitation and Hazard Prevention of the
Ministry of Education, Xi’an710054, China
| | - Hongyu Pan
- College
of Safety Science and Engineering, Xi’an
University of Science and Technology, Xi’an710054, China
- Key
Laboratory of Western Mine Exploitation and Hazard Prevention of the
Ministry of Education, Xi’an710054, China
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