The influence of mining factors on seismic activity during longwall mining of a coal seam

In this article an attempt to determine the influence of mining factors on the seismic activity during the longwall mining of the upper layer of coal seam no. 405/2 in one of the Polish hard coal mines in the Upper Silesian Coal Basin was conducted. Two longwall panels were mined in analogous geological conditions and based on the same mining system and technology. However, there was significant difference with regards to the mining factors, which was reflected in the observed seismic activity. Some tools used in mining seismology were applied to illustrate the aforementioned influence of mining factors, e.g. the frequency-energy distribution, the frequency-magnitude distribution, the 2 D distribution of released seismic energy, the relationship between released seismic energy and the volume of mined coal, the Benioff strain release, and the Gutenberg-Richter(GR) b coefficient distribution(b is the proportion between high and low energy tremors). Concerning the Benioff strain release, a new solution, based on the slope of a fitted line in a moving time window, is proposed.     

Scaling analysis of hydrogen flow with carbon dioxide cushion gas in subsurface heterogeneous porous media

Subsurface hydrogen (H₂) storage in geological formations is of growing interest for decarbonization. However, there is a knowledge gap in understanding the multiphase flow involved in this process, which can have a significant impact on the recovery performance of H₂. Therefore, a full-compositional modeling study was conducted to analyze potential issues and to understand the fundamental hydrodynamic mechanisms of H₂ storage. We performed a range of 2D vertical simulations at the decametre scale with a very fine cell size (0.1 m) to observe the detailed flow behaviour of H₂ with carbon dioxide (CO₂) as cushion gas in various flow regimes. Issues such as viscous instability, capillary bypassing, gas trapping and gravity segregation are analysed here. To generalize our calculations, we have validated and applied the scaling theory in the context of subsurface H₂ storage. Since this study is focused on the hydrodynamic behaviour, three dimensionless groups, including aspect factor, capillary/viscous ratio and gravity/viscous ratio were identified to correlate recovery performance between various scales in a fixed heterogeneous system. It was found that H₂ could infiltrate the cushion gas in the proximity of the injectors, meaning that CO₂ is not displaced away from the injectors in a piston-like fashion. As a result, the purity of the back produced H₂ is much degraded, particularly in a viscous-dominated scenario. On the other hand, the injected H₂ mostly accumulates at the top forming a highly restricted mixing zone with CO₂ in the gravity-dominated case. The recovery performance is therefore much improved in this case. Although the gas distribution can be significantly altered by capillary forces leading to bypassed zones, the recovery performance of H₂ is hardly influenced. This is because the back-produced H₂ recovery is not dependent on the sweep efficiency of the gas. H₂ can be back produced following the same paths which were formed during injection.     

Hydrogen wettability in carbonate reservoirs: Implication for underground hydrogen storage from geochemical perspective

Hydrogen has been considered as a promising renewable source to replace fossil fuels to meet energy demand and achieve net-zero carbon emission target. Underground hydrogen storage attracts more interest as it shows potential to store hydrogen at large-scale safely and economically. Meanwhile, wettability is one of the most important formation parameters which can affect hydrogen injection rate, reproduction efficiency and storage capacity. However, current knowledge is still very limited on how fluid-rock interactions affect formation wettability at in-situ conditions. In this study, we thus performed geochemical modelling to interpret our previous brine contact angle measurements of H₂-brine-calcite system. The calcite surface potential at various temperatures, pressures and salinities was calculated to predict disjoining pressure. Moreover, the surface species concentrations of calcite and organic stearic acid were estimated to characterize calcite-organic acid electrostatic attractions and thus hydrogen wettability. The results of the study showed that increasing temperature increases the disjoining pressure on calcite surface, which intensifies the repulsion force of H₂ against calcite and increases the hydrophilicity. Increasing salinity decreases the disjoining pressure, leading to more H₂-wet and contact angle increment. Besides, increasing stearic acid concentration remarkably strengthens the adhesion force between calcite and organic acid, which leads to more hydrophobic and H₂-wet. In general, the results from geochemical modelling are consistent with experimental observations that decreasing temperature and increasing salinity and organic acid concentration increase water contact angle. This work also demonstrates the importance of involving geochemical modelling on H₂ wettability assessment during underground hydrogen storage.     

Hydrogen wettability of clays: Implications for underground hydrogen storage

This study investigates the ability of hydrogen (H₂) to wet clay surfaces in the presence of brine, with implications for underground hydrogen storage in clay-containing reservoirs. Rather than measuring contact angles directly with hydrogen gas, a suite of other gases (carbon dioxide (CO₂), argon (Ar), nitrogen (N₂), and helium (He)) were employed in the gas-brine-clay system under storage conditions (moderate temperature (333 K) and high pressures (5, 10, 15, and 20 MPa)), characteristic of a subsurface environment with a shallow geothermal gradient. By virtue of analogies to H₂ and empirical correlations, wettabilities of hydrogen on three clay surfaces were mathematically derived and interpreted. The three clays were kaolinite, illite, and montmorillonite and represent 1:1, 2:1 non-expansive, and 2:1 expansive clay groups, respectively. All clays showed water-wetting behaviour with contact angles below 40° under all experimental set-ups. It follows that the presence of clays in the reservoir (or caprock) is conducive to capillary and/or residual trapping of the gas. Another positive inference is that any tested gas, particularly nitrogen, is suitable as cushion gas to maintain formation pressure during hydrogen storage because they all turned out to be more gas-wetting than hydrogen on the clay surfaces; this allows easier displacement and/or retrieval of hydrogen during injection/production. One downside of the predominant water wettability of the clays is the upstaged role of biogeochemical reactions at the wetted brine-clay/silicate interface and their potential to affect porosity and permeability. Water-wetting decreased from kaolinite as most water-wetting clay over illite to montmorillonite as most hydrogen-wetting clay. Their wetting behaviour is consistent with molecular dynamic modelling that establishes that the accessible basal plane of kaolinite's octahedral sheet is highly hydrophilic and enables strong hydrogen bonds whereas the same octahedral sheet in illite and montmorillonite is not accessible to the brine, rendering these clays less water-wetting.     

Reasons for breaking of chemical bonds of gas molecules during movement of explosion products in cracks formed in rock mass

The purpose of this study was to develop a physico-mathematical model and technique for estimation of chemical bond stability depending on electric field intensity of an external point charge. A hypothesis for a possible physico-chemical mechanism of the formation of additional harmful gases in the rock destruction by blasting was proposed. The theoretical basis of the hypothesis is the method of theretical evaluation of bond energy depending on the distance to a point charge, the third Coulomb centre. The quantum-mechanical model for calculating the electronic terms of molecules makes it possible to solve problems associated with the determination of parameters of molecules under the action of various physical fields on the system under consideration. The model was approved for some diatomic molecules. The discrepancy between the experimental data and calculated data did not exceed 14%, which proves accuracy of the obtained results. The model can be used in the field of research into the causes of gas-dynamic phenomena in underground coal mines, in studies of the degree of stability of nanostructured components of coal under physical influences, and in the theoretical design of new compounds and structures in the field of nanomaterial science and nanotechnology.     

Inhibition of hydrogen production reactions in the wet dust removal system using CeCl3 solutions

For treatment of aluminum dust, a wet dust removal system has been used worldwide. During treatment, aluminum dust is inhaled into a water tank of the dust collector. As hydrogen production reactions are likely to take place in the water tank, there exists a great risk of fire or explosion accidents associated with the wet dust removal system. Based on field research and laboratory experiments, Hydrogen Inhibition Method (HIM) by using CeCl₃ solutions was proved capable of inhibiting reactions between aluminum dust and water. When the concentration of CeCl₃ solutions reached 6.02 g/L, there was basically no hydrogen gas produced. SEM, EDS and XPS characterizations were used to assess the aluminum particles before and after being reacted with water or CeCl₃ solutions, respectively. Shrinking core model was utilized to identify the corresponding chemical reaction kinetics. Additionally, a physicochemical mechanism was established to explain these phenomena.     

消防法制建设与消防监督的相关性探究

文章从我国消防法制建设的现状出发,简要介绍了现行的消防法律法规,并详细解读了其现存问题,最后分别从消防法制建设与消防监督两个角度提出了发展对策,以期能为改善我国现阶段的消防法制建设和消防监督体系带来一定的参考意见.     

European legal framework related to underground mining and tunnelling concerning commission directive(EU) 2017/164, 31 January establishing a fourth list of indicative occupational exposure limit values

Directive(EU) 2017/164 establishes a fourth list of indicative occupational exposure limit values(IOELVs)to protect workers from risks of exposure to hazardous chemicals. It states that in underground mining and tunnelling, Member States may benefit from a transitional period regarding IOELVs for nitrogen monoxide, nitrogen dioxide, and carbon monoxide, during which the existing established IOELVs may be applied. The European Advisory Committee on Health and Safety at Work questions the technical feasibility of the proposed IOELVs in underground mining(CO, NO and NO_2) and tunnelling(NO and NO_2).Challenges arise concerning the availability of measurement methodologies for compliance with proposed IOELVs(NO_2) in underground mining and tunnelling environments.     

自动化立体仓库消防给水设施设计探讨

立体仓库采用智能化出入库管理,集自动入库、智能化储存和自动化出库于一体,物品高度集中,火灾负荷集中的建筑。立体仓库的消防给水设施是其中重要的消防设施之一,本文主要分析立体仓库消防水系统的设计及参数的选择。