• Energy Research

Studying the infrared radiation (IR) variation during the coal gas desorption (CGD) process is a critical aspect in understanding and controlling abnormal coal gas emissions, and preventing coal gas disasters and accidents, such coal and gas outburst. We conducted IR experiments on CGD to analyze the mechanisms and factors influencing changes in infrared radiation temperature (IRT), as well as to assess the multifractal characteristics. The results indicate that as gas desorption time increases, the average infrared radiation temperature difference (¿AIRT) of coal under varying adsorption equilibrium pressure (AEP) follows a double exponential downward trend. Concurrently, the differential infrared cloud image (DICI) transitions from a high temperature to a low temperature distribution state. The counts of infrared radiation temperature difference (¿IRT) in the DICI during CGD are normally distributed, with the classification count of ¿IRT in the interval showing an upward trend. The multifractal spectra of the DICI gradually change from a left hook to a right hook as gas desorption time increases, and its degree of opening increases when the CGD time and AEP are increased. Both multifractal spectral parameters ¿a and ¿f(a) increase with the rise in CGD time. The changes in IRT and its derivative parameters can effectively reflect the trend and distribution characteristics of the amount of CGD. These results provide a theoretical foundation for understanding the characteristics of CGD, real-time monitoring of abnormal changes in coal gas emission, and the prevention of coal and gas outbursts. Peer Reviewed

Transversal competences such as sustainability or critical thinking have become more important in the last decades in University teaching. The objective of this article is to assess the effectiveness of debate as a teaching method capable of fostering such competences in engineering students. To do this, a debate activity has been held facing two reasonable positions: Sustainable Development versus Degrowth. The research methodology consisted of performing this activity in the classroom (with 13 students in this particular case study), and conducting some tests before and after the debate that served as feedback to assess the effectiveness of the debate on the learning process. This feedback is composed of different documents, including a pre-post test, a specific survey about the debate, a pre-post knowledge survey and the Student Evaluation of Educational Quality (SEEQ) survey. A methodology for the organization of the debate is proposed and the answers of the students to these feedback documents are analyzed. As it can be inferred from the different surveys, the debate has been an efficient learning tool to acquire knowledge and to develop sustainability and critical thinking competences.

Longwall caving mining (LCM) can lead to many environmental problems that have drawn worldwide attention. A previous survey found that most scholars tend to analyze the two issues separately, that is, coal mining-induced subsidence and heavy metal pollution sources in the soil of the mining regions. Based on field monitoring as well as the collection and analysis of soil samples, a previous study estimated ground settlement and analyzed the surface subsidence law and spatial distribution characteristics of heavy metals in soils. Moreover, a geographic information system was combined with multivariate statistical analysis methods to analyze the heavy metal pollution sources in soils. At the same time, the mechanism of heavy metal accumulation in the subsidence area was analyzed. The study found that the most active subsidence of settlement was 137.5 m behind the workface and moved forward with the workface. LCM has already caused significant disturbance to the soils in the Hengyuan Mine. Moreover, the distribution pattern of eight heavy metals was consistent with the surface subsidence law. The sources of heavy metal pollution in the soils were also identified; namely, coal mining-induced subsidence (64.1%) and mixed transportation and wind-mediated spread (35.9%), offering a reinterpretation of the LCM's footprint.

As a major pillar of global energy production, coal mining requires continuous advancements in efficiency to contribute to the broader goal of energy sustainability, all the while the shift towards more sustainable energy sources is underway. Mechanized excavation systems employed in underground coal mines, particularly within the longwall mining method, enable high-tonnage coal production. The Longwall Top Coal Caving (LTCC) method, one of the longwall mining techniques, has been developed for the effective extraction of coal from thick coal seams. However, as mining operations delve deeper, various complex issues, such as gallery cross-sectional variation, emerge. Gallery cross-sectional variation can increase the risk of collapse by affecting the stress distribution in the rock mass, posing a threat to worker safety. This study centers on the numerical modeling and analysis of gallery cross-sectional variation in the Ömerler underground mine, operated by the Turkish Coal Enterprises (TKI), West Lignite Enterprise (GLI). To achieve this objective, an extensive database was established through field and laboratory rock mechanics studies. This database was then utilized in the Fast Lagrangian Analysis of Continua 3D (FLAC3D) (v6.0) program to simulate the cross-sectional variations of the A6 panel in the Ömerler underground mine. The numerical simulation results provide valuable insights into the secondary stress-deformation changes associated with gallery cross-sectional variation.