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The paper proposes a mathematical model, based on a one-dimensional nonhomogeneous diffusion equation, which enables the evaluation of methane emissions from extracted coal during its transportation through the haulage system of a coal mine longwall face and their contribution to spatiotemporal distribution patterns of mine atmospheric parameters characterizing the gas environment in the face area. The solution to the specified equation has been implemented using the Mathcad computational software package. The results of numerical experiments demonstrate potential applicability for enhancing operational efficiency in managing technological processes within the boundaries of the longwall face.

The heating rate of tar-rich coal is an essential factor in maximizing the underground heating method. The physical (pore-fracture) structure is the key oil and gas transportation channel from coal. In this work, the physical structure of coal under varying heating rates was reestablished to reveal the reason for the pore-fracture evolution. Notably, the heating rate affects the physical structure in this pyrolysis process for coal. The expansion and connectivity of the physical in tar-rich coal initially rise, followed by a decline at 1–16°C/min. Within the range of heating rates, the porosity of tar-rich coal exhibits an initial increase, followed by a subsequent decrease. The maximum number of visible fractures and the formation of an interconnected network of fractures occur at a heating rate of 4°C/min. Tar-rich coal’s porosity reaches a maximum of 53.16%. Guidelines for the use of underground coal heating technology are provided by the pore-fracture variation mechanism under varying heating rates.

Coal and gas outbursts are small-scale geological disasters controlled by tectonic movement, and tectonic coal is widespread in outburst zones. In this study, we compare tectonic and intact coal specimens to examine the basic properties of tectonic coal. We estimate the different energies and limits of the crushing work ratio of coal from five typical outburst cases using on-site outburst data, and discuss the relationship between outbursts and tectonic coal. The results show that tectonic coal is a product of tectonic movement and its original primary structure is destroyed during the tectonic process. Compared with intact coal, tectonic coal shows low strength properties and a crushing work ratio of 22.11 J/m2. The specific surface area and total pore volume of the minipores, mesopores, and macropores of the coal strongly increase under conditions of intense tectonism, which indicates that tectonic coal has a very high capacity for rapid initial gas desorption. An adequate supply of gas is required to transport outburst coal, such that the existence of coal particles smaller than the critical diameter is important. Our calculations indicate that the crushing work ratio of coal from the five outburst case ranges from 22.19 to 78.67 J/m2. Only the crushing work ratio of tectonic coal satisfies the requirement for these cases. Therefore, the properties of the tectonic coal and crushing work ratio for the five cases indicate that the widespread occurrence of tectonic coal plays a crucial role in outbursts.

Beijing has suffered from heavy local emissions as well as regional transport of air pollutants, resulting in severe atmospheric fine-particle (PM2.5) pollution. This study developed a combined method to investigate source types of PM2.5 and its source regions during winter 2016 in Beijing, which include the receptor model (positive matrix factorization, PMF), footprint and an air quality model. The PMF model was performed with high-time-resolution measurements of trace elements, water soluble ions, organic carbon and elemental carbon using online instruments during the wintertime campaign of the Air Pollution and Human Health in a Chinese Megacity – Beijing (APHH-Beijing) program in 2016. Source types and their contributions estimated by PMF model using online measurements were linked with source regions identified by the footprint model, and the regional transport contribution was estimated by an air quality model (the Nested Air Quality Prediction Model System, NAQPMS) to analyze the specific sources and source regions during haze episodes. Our results show that secondary and biomass-burning sources were dominated by regional transport, while the coal combustion source increased with local contribution, suggesting that strict control strategies for local coal combustion in Beijing and a reduction of biomass-burning and gaseous precursor emissions in surrounding areas were essential to improve air quality in Beijing. The combination of PMF with footprint results revealed that secondary sources were mainly associated with southern footprints (53 %). The northern footprint was characterized by a high dust source contribution (11 %), while industrial sources increased with the eastern footprint (10 %). The results demonstrated the power of combining receptor model-based source apportionment with other models in understanding the formation of haze episodes and identifying specific sources from different source regions affecting air quality in Beijing.

The Himalayas form a major atmospheric barrier between South Asia and Tibetan Plateau, yet cross‐barrier transport of anthropogenic metals remains poorly constrained. We use moss δ66Zn along a 750–4,100 m a.s.l. south‐north transect in Motuo to trace pollution sources and transport processes. On the southern slope, trace metals (Zn, Pb, As, Ni, Co) display pronounced altitudinal gradients, with low elevations showing high concentrations and light δ66Zn (−0.41‰ to −0.32‰) dominated by smelting (42%–50%). With increasing elevation, concentrations decrease and δ66Zn becomes heavier (0.20‰ to 0.29‰), reflecting greater coal combustion inputs (35%–50%). North of the crest, overall metal loads are lower, but high elevations (>3,500 m) show heavy δ66Zn (0.30‰ to 0.44‰) and strong coal contributions (43%–54%). Our results show that topography, anthropogenic emissions, and vegetation coverage regulate vertical pollutant distribution patterns, providing direct Zn isotopic evidence for transboundary transport of coal combustion emissions from South Asia to the Tibetan Plateau.

As an equipment failure that often occurs in coal production and transportation, belt conveyor failure usually requires many human and material resources to be identified and diagnosed. Therefore, it is urgent to improve the efficiency of fault identification, and this paper combines the internet of things (IoT) platform and the Light Gradient Boosting Machine (LGBM) model to establish a fault diagnosis system for the belt conveyor. Firstly, selecting and installing sensors for the belt conveyor to collect the running data. Secondly, connecting the sensor and the Aprus adapter and configuring the script language on the client side of the IoT platform. This step enables the collected data to be uploaded to the client side of the IoT platform, where the data can be counted and visualized. Finally, the LGBM model is built to diagnose the conveyor faults, and the evaluation index and K-fold cross-validation prove the model’s effectiveness. In addition, after the system was established and debugged, it was applied in practical mine engineering for three months. The field test results show: (1) The client of the IoT can well receive the data uploaded by the sensor and present the data in the form of a graph. (2) The LGBM model has a high accuracy. In the test, the model accurately detected faults, including belt deviation, belt slipping, and belt tearing, which happened twice, two times, one time and one time, respectively, as well as timely gaving warnings to the client and effectively avoiding subsequent accidents. This application shows that the fault diagnosis system of belt conveyors can accurately diagnose and identify belt conveyor failure in the coal production process and improve the intelligent management of coal mines.

Coal and rock mass constitute a type of porous medium. This study investigated the influence of temperature impact on the mechanical properties and acoustic emission (AE) characteristics of coal. A mechanism analysis was performed from the perspective of microstructure. The results show that the temperature impact causes the development of pores and cracks in the coal, which reduces the strength of coal. The elastic modulus of coal generally decreases with increasing temperature gradient. AE parameters increase with the increase in the load and reach the maximum value at the peak stress. AE parameters and cumulative parameters decrease with increasing temperature gradient. Not only does temperature impact change the fracture structure of the coal surface, but also the internal fracture structure of the coal is significantly affected. After temperature impact, the cracks expand and new cracks are initiated, and the fracture volume of the coal increases. Temperature impact causes the volume and specific surface area of small pores and meso-pores in coal to increase, and promotes the opening of the necking pores within the coal. The impact causes macro-pores to penetrate through to form cracks, which increases the transport of coal gas and significantly improves the permeability of coal. The thermal stress generated by coal under temperature impact is greater than its tensile strength, which promotes the cracking of coal, along with the initiation, widening, extension, and expansion of crack networks, which significantly change the fracture structure of coal. The research results lay a certain theoretical and experimental foundation for further study of mechanical properties of coal affected by liquid nitrogen.

Outburst energy is a major factor influencing coal and gas outbursts, albeit its estimation is difficult owing to the lack of amenable means for quantification of gas desorption. In the past decades, determining the mechanism of outbursts is one of the most challenging issues in rock mechanics. In this study, a triaxial coal and gas outburst simulation system was employed to perform simulated experiments using He (to rule out the influence from gas ad-desorption), N2, and CO2. This facilitated understanding of the energy principle underlying the said outbursts and evaluation of the effects of gas desorption on outburst development. Results of this study indicate that outburst energy and energy consumption are influenced by several factors, including outburst pressure, outburst intensity, ejection distance, and particle size of ejected coal. Among these, gas desorption demonstrates the greatest influence when performing controlled tests (using He). Considering the effects of gas desorption, the total outburst energy can be increased by 1.35–2.95 times, thereby causing an enormous increase in the destructive potential of outbursts. Additionally, values of the coal crushing and transport energies can be enhanced by the order of 118.9–206.6% and 157.8–406.6%, respectively, thereby resulting in a stronger conveying capacity of outburst coal–gas flow along with severe coal fragmentation. A further analysis of the energy distribution indicated that in the development stage, gas desorbed from coal acts as the force driving coal transport, whereas free gas energy is mainly consumed during coal crushing. Findings of this study highlight the importance of quantifying contributions of coal gas towards effective interpretation of outburst-causing mechanisms.

Liang, S.-Q., 2019. North-to-South transport service modes of power coal based on bi-level programming game model: A comparative study on inner Mongolia-Jiangxi railway and shipping services. In: Gong, D.; Zhu, H., and Liu, R. (eds.), Selected Topics in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 94, pp. 460–464. Coconut Creek (Florida), ISSN 0749-0208. The coal transport mode from North to South China is investigated to find out how the ocean shipping mode and the north-to-south coal transport are susceptible to the Inner Mongolia-Jiangxi railway based on the bi-level programming game model. This paper derives the following conclusions from the case analysis of the competitive behaviors for the Erdos-Wuhan transport service modes: (1) The inauguration of Inner Mongolia-Jiangxi Railway has obvious traffic transfer effect on the traditional sea-railway combined transport mode, and will lead the freight rate to further reducing; (2) the higher the value of time (VOT) in coal transport service, the more apparent the competition effect of Inner Mongolia-Jiangxi Railway on sea-railway combined transport service mode; (3) the upgrading of sea-railway combined transport service level, especially its rapidity and punctuality, has regulation effect on the competition of Inner Mongolia-Jiangxi Railway. In the end, this paper gives some policy advice on how to improve the transport efficiency of coal from north to south China subject to freight rate, service upgrading and marketing strategies.

In view of the requirements of dense underground water exploration and drainage holes, high hole forming accuracy, rapid drilling rig relocation and reduced labor intensity in coal mines with trackless transportation conditions, the application of rubber wheel directional drilling rigs can well meet the requirements and complete the drilling construction. Taking the representative ZDY3500JD rubber wheel directional drilling rig as an example, the composition and basic parameters of the drilling rig are introduced, and the field application is carried out in the Shendong coal mine of the National Energy Group. The completion of the relocation greatly reduces the labor intensity of workers and improves work efficiency. It has stable performance and high hit rate in the construction of water exploration and drainage holes, and various parameters meet the design requirements, which lays a good foundation for the construction of similar mine drilling.