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The characteristics of gas seepage in broken coal and rock composed of different particle sizes and grades were investigated in this study. On the basis of Darcy's law and non‐Darcy seepage theory, equations of gas permeability in the nonlinear seepage of broken coal and rock, as well as the porosity of broken coal and rock, under triaxial compression were determined. The stress loading path of gas seepage in broken coal and rock was developed. The characteristics of gas seepage in broken coal and rock composed of different particle sizes and grades were analyzed, and the results showed that the gas permeability after compression was proportional to the particle size of the broken coal and rock. Under triaxial compression, the gas permeability of the broken coal and rock composed of graded‐particle sizes was lower than that of the broken coal and rock composed of different single‐particle sizes. The gas permeability of the broken coal was lower than that of the broken rock mass, and the gas permeability and porosity of the broken coal and rock can be described by the exponential decay function. At a constant porosity, the gas permeability of the broken coal and rock was proportional to the size grading index under triaxial compression. The coefficient of viscosity and gravity of the flow are key factors influencing the flow permeability in broken coal and rock. This study provides a reference for on‐site practice such as the efficient extraction of gas in goafs. [ABSTRACT FROM AUTHOR]

The evolution characteristics of pores and fractures in coal after liquid carbon dioxide (CO2) phase change are important factors that determine the permeability increase effect. Therefore, it is critical to correctly understand the influences of liquid CO2 phase change on pores and fractures in coal. The changes of adsorption and desorption isotherm, pore size, pore volume, and specific surface area of fractured coal and fractured coal were compared by low temperature liquid nitrogen adsorption experiment. In addition, a scanning electron microscope was adopted to observe fracture characteristics of fractured and unfractured coal samples and analyze changes in the connectivity and fracture development. Experimental results show that the fractured coal samples exhibit better hysteresis loops and a larger proportion of gas desorption than the unfractured ones. Fractured coal samples contain more developed pores and fractures compared with unfractured ones, and their fragmentation degree, pore diameter, fracture width, and connectivity of pores and fractures are also better. Besides, the closer the samples from the fracturing boreholes are, the better the fracturing effect. This indicates that liquid CO2 phase change can effectively enhance the gas transport capacity in pores and fractures in coal. The research results provide a solid basis for the better application of liquid CO2 phase‐change fracturing to the prevention of coal and gas outburst disasters and the realization of efficient gas extraction in deep coal seams. [ABSTRACT FROM AUTHOR]

Zinc‐based sorbents with ordered mesoporous structure were modified with aluminium and the key factors in the preparation were optimized based on the results of desulphurization tests performed in a fixed‐bed reactor with simulated coal gas. It was shown that the sorbents for hydrogen sulphide removal reached an optimum sulphur capacity of 9.14% when prepared under conditions of 10.0 crystalline pH, 30:1 Si:Al molar ratio, 0.32:1 Zn:Si molar ratio, and 1:3 Zn:TAA molar ratio. The sorbent without aluminium was synthesized synchronously as a comparison sample to investigate the effect of aluminium addition on the desulphurization properties. The surface acidity of the sorbents is enhanced by the addition of aluminium, and the sulphur capacity of the aluminium‐doped sorbent is consequently lower compared to that of aluminium‐free sorbent. Nevertheless, the aluminium‐doped sorbent shows a significant advantage in stability of performance over multiple desulphurization–regeneration cycles and reaches an 81% retention rate of sulphur capacity after five desulphurization, while the aluminium‐free sorbent is only 51% in contrast. The characterization results manifest that aluminium enters the carrier skeleton and increases the wall thickness, which alleviates the collapse of the carrier pore channels and the agglomeration of the active components during the desulphurization process. Stable pore structures and highly dispersed active components facilitate the mass transfer in the reaction process after multiple desulphurization. As a result, the aluminium‐doped sorbent exhibits better performance stability in high temperature coal gas desulphurization. [ABSTRACT FROM AUTHOR]

Saturation characteristics of water and capillary pressure are important for hydrofracturing or water flooding, which is widely adopted in dust suppression, methane displacement, and gas and coal outburst elimination. In this paper, we have studied the water saturation characteristics of coal samples with different coal ranks and their effect on capillary pressure. It was found that the isothermal adsorption of water vapor from coal samples can be divided into three processes: monolayer adsorption, multilayer adsorption, and capillary condensation. The dent isothermal adsorption model can well describe water vapor adsorption of coal samples, indicating water molecules were first adsorbed on the first‐order adsorption site of pore surfaces at low relative humidity and then on the second‐order adsorption site with increasing relative humidity. An obvious hysteresis occurred in the process of water imbibition and drainage. A capillary pressure of ~325 MPa or even larger was required to displace the water from the coal. Besides, micro‐ and mesopores play a more important role in capillary pressure. The capillary pressure of coal samples was positively correlated with wettability at lower water saturation, but it is not significant at higher capillary pressures. Therefore, the article's results provide a new direction for solving the water‐locking effect in coal seams. [ABSTRACT FROM AUTHOR]

With the application of new technologies for coal mine gas control, it has been increasingly urgent to apply the fixed‐point closed sampling (FPCS) technology for accurate measurement of coal seam gas content. In this study, gas desorption during FPCS was analyzed. In addition, gas desorption experiments and COMSOL simulations were conducted on coal particles. Furthermore, the gas desorption law during FPCS was compared with that under atmospheric pressure. The results show that Sun's formula can effectively characterize the gas desorption law during FPCS, and the i value remains unchanged when the gas desorption curve is fitted with Sun's formula. On this basis, a specific method for calculating gas loss during FPCS by using Sun's formula was proposed. The research findings are expected to provide a theoretical basis for accurate measurement of coal seam gas content by means of FPCS. [ABSTRACT FROM AUTHOR]

As coal mining depth increases, there is a corresponding increase in both ground stress and gas pressure, leading to a higher incidence of coal and gas outburst accidents. To investigate the stress distribution law and gas release degree of the adjacent coal body within the goaf of the outburst coal seam, and to acquire an understanding of the impact range of the large mining face goaf on the stress of the coal seam, this study employed theoretical analysis and numerical simulation to analyze the impact and scope of the goaf on the adjacent coal body, and measured the gas content of the coal seam. The findings indicated that following the completion of mining on the working face, there was a redistribution of stress in the coal and rock layers within 40 m of the goaf, with the stress concentration phenomenon observed at a distance of 2.6 m from the goaf. Affected by the stress relief effect of mining, the stress, gas content, and other related factors have been studied in detail by researchers. Affected by the stress relief effect of mining, the stress, gas content, and gas pressure of the surrounding rock near the goaf in the coal seam are significantly reduced. The research results verify that tunneling along the goaf is an effective method to prevent coal and gas outbursts and improve stoping efficiency. [ABSTRACT FROM AUTHOR]

The research on the mechanism of coal and gas outburst is still in the hypothesis stage, and exploration of the outburst mechanism fro m an energy perspective often focuses on the calculation of coal rock elastic energy and gas expansion energy. There are some studies on elastic energy and gas expansion energy of coal rock caused by added water during outburst, although hydr aulic measures not only improve the permeability of coal seam, but also increase the water content. For calculating the gas expansion energy, the atmospheric gas desorption characteristic is generally utilized, while the gas desorption is completed on the condition of dropping pressure in outburst, and the expansion energy research, based on that law, inevitably brings about errors, thus affecting the objectivity of the potential research. In this study, uniaxial cyclic loading experiments were carried out on briquette coal samples with water content of 0%, 1%, 2% and 4%, whose elastic energy density was analyzed, in addition to examining how the added water affected the mechanical properties and the elastic energy of coal. The pressure drop gradient of the experiment is set 2.5 –2 MPa, 1.5 –1 MPa, 0.5 MPa‐0 Pa. By stepwise depressurization desorption of coal samples after water injection, the gas expansion energy in different moisture is measured in each pressure drop stage, and the influence of moisture on gas expansion energy is quantitatively explored. Research has shown that the higher the water content, the lower the elastic energy density, while the higher the stress, the greater the elastic energy of coal. The gas expansion energy grows linearly with the increase of adsorption equilibrium pressure and diminishes in negative exponential law with the increasing moisture. Under the experimental conditions, the expansion energy decreases by 7%–9% and the elastic energy by 9.7% on average for every 1% increase in added water, and the influence gradually weakens when the moisture exceeds the critical value. This study innovatively simulates the pressure swing desorption when a coal and gas outburst occurs in the laboratory, confirms the critical moisture that affects the outburst potential, and is a useful exploration in the coal and gas outburst mechanism. Significantly the research results can guide the engineering practice when using hydraulic measures to prevent and control outburst disasters. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Acidithiobacillus ferrooxidans are beneficial bacteria for bioleaching in the mining industry to extract useful fractions from tons of waste. These bacteria are able to oxidize ferrous iron (Fe2+) to ferric iron (Fe3+) and use the released energy to assimilate carbon from carbon dioxide or carbonates, and can be used in the desulfurization of coal and gas. In this regard, activators of the growth of these bacteria may be useful. During the experiments on these bacterial strains, an unexpected effect of growth activation was revealed. This gives rise to further research in this direction and the identification of patterns of "structure‐activity" derivatives of ferrocene and porphyrins in relation to A. ferrooxidans. [ABSTRACT FROM AUTHOR]

At present, the coordinated exploitation of coal measures‐associated resources is facing many problems, such as wide range, complex technology, and lack of in‐depth theoretical research. To study and solve the coordinated exploitation of coal and oil‐type gas‐associated superimposed resources, taking Huangling No.2 mine in Ordos Basin as an example, a fluid–solid coupling finite element model for coal mining in associated mines is constructed, and the variation laws of axial stress, displacement, stability and oil‐type gas pressure of each gas reservoir at different advancing distances of coal face are numerically simulated and the disturbance characteristics of the mining coal seam to the gas reservoir are obtained. The fluid–solid coupling finite element model of associated mine extraction is constructed, and the variation laws of axial stress, displacement, stability, and oil‐type gas pressure of the gas reservoir and coal seam when extracted from different gas reservoirs are numerically simulated. The disturbance characteristics of the surface‐extracted gas reservoir to the coal seam are obtained. The study results show that the larger the interval between the gas reservoir and the mining coal seam, the smaller the degree of disturbance, and the pressure relief effect of the oil‐type gas in the gas reservoir is positively related to its displacement; the surface drilling extract oil‐type gas, the oil‐type gas in the underlying gas reservoir will migrate and supplement to the extracted layer, and the plastic area around the extraction well basically appears in the mudstone layer and coal seam, and the gas reservoir near the coal seam has good pressure relief effect. Combined with the mutual disturbance characteristics between gas reservoir extraction and coal seam extraction and the field practice, disturbance control strategies for coordinated exploitation of superimposed resources of coal and oil‐type gas in Ordos Basin are proposed. [ABSTRACT FROM AUTHOR]

Fossil fuel divestment movements have gained momentum since 2011, aimed at ending fossil fuel use and a move toward a cleaner, affordable, and sustainable energy system, for business and society. The present study investigates the direct impact of fossil fuel divestment announcements on stock prices of firms listed on the United States' stock exchanges. Using an event study and guided by the United Nation's sustainable development goals (SDGs), we test the effects of 116 divestments announcements between 2014 and 2019 on 51 publicly traded fossil fuel companies. Our results suggest that there is a negative effect of these announcements on fossil fuel firm stock prices. Also, we find that the type of fossil fuel firm (coal or oil and gas), the type of divestment (partial, coal only, or full), the timing of the announcement, and the size of the divesting investor have some explanatory power in relation to the (cumulative) abnormal returns following the divestment announcements. While the negative impact on stock prices is not surprising, the reaction from the divested firms after such large divestitures is not consistent with what may be expected, given past reactions to divestitures seeking to achieve different social goals. Given the SDGs, it seems clear why investors are divesting themselves from fossil fuel firms, but why has the reaction to the 116 divestments led to very little change in the way these publicly traded fossil fuel firms do business given their direct and growing impacts on society? We conclude the study with some suggestions for future research. [ABSTRACT FROM AUTHOR]

The Ukraine war has increased coal and gas prices during 2022. Consequently, spot prices in Australia's National Electricity Market rose from $75 to $225/MWh, year‐on‐year. Households are shielded from spot prices, but as energy retailer hedge contracts mature, they are replaced by higher cost contracts, and end‐use retail tariffs will then rise. In this article, fuel poverty levels in Queensland are analysed. Model results forecast that fuel poverty rises from 6.8 per cent to 10.5 per cent of households. However, changes to energy concessions policy in 2016‒2017 materially enhanced horizontal and vertical efficiency, with successful targeting rising from 51 per cent to 69 per cent of vulnerable households. [ABSTRACT FROM AUTHOR]

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India's stated goals to more than double steelmaking production capacity by 2030 merit consideration of new technical pathways for productivity gains and emission reduction. Already the second‐largest steel producer globally, India primarily relies on coal‐based technologies for ironmaking, with heavy reliance on imported metallurgical‐grade coal. This study develops an integrated thermodynamic modeling approach by iteratively coupling the raceway adiabatic flame temperature (RAFT) and Rist models to explore the ability to consider various hydrocarbon injectants through the tuyeres of a blast furnace. Based on the thermodynamic criteria set in the modeling framework, optimal coinjection rates for natural gas (as a low‐carbon feed) are identified along with pulverized coal injection as a function of various operating parameters, including top gas temperature, RAFT temperature, and ore processing (pelletization). The potential for productivity gains and CO2 emission reduction in the blast furnace process is discussed. While the study bears specificity to Indian operating conditions related to raw material composition and blast furnace process parameters, the learnings may be applicable to other studies in the global context, with potential extension to deeper decarbonization pathways, such as increased use of hydrogen. [ABSTRACT FROM AUTHOR]

Summary: Hydrogen is a clean alternative to fossil fuels. It has applications for electricity generation and transportation and is used for the manufacturing of ammonia and steel. However, today, H2 is almost exclusively produced from coal and natural gas. As such, methods to produce H2 that do not use fossil fuels need to be developed and adopted. The biological manufacturing of H2 may be one promising solution as this process is clean and renewable. Hydrogen is produced biologically via enzymes called hydrogenases. There are three classes of hydrogenases namely [FeFe], [NiFe] and [Fe] hydrogenases. The [FeFe] hydrogenase HydA1 from the model unicellular algae Chlamydomonas reinhardtii has been studied extensively and belongs to the A1 subclass of [FeFe] hydrogenases that have the highest turnover frequencies amongst hydrogenases (21,000 ± 12,000 H2 s−1 for CaHydA from Clostridium acetobutyliticum). Yet to date, limitations in C. reinhardtii H2 production pathways have hampered commercial scale implementation, in part due to O2 sensitivity of hydrogenases and competing metabolic pathways, resulting in low H2 production efficiency. Here, we describe key processes in the biogenesis of HydA1 and H2 production pathways in C. reinhardtii. We also summarize recent advancements of algal H2 production using synthetic biology and describe valuable tools such as high‐throughput screening (HTS) assays to accelerate the process of engineering algae for commercial biological H2 production. [ABSTRACT FROM AUTHOR]

Deep mining will increase the likelihood of coal and gas outburst accidents and do harm to the safety of coal mining. In this study, a coal and gas outburst experiment under deep high‐stress conditions was carried out and stress–gas pressure–temperature response laws in coal and rock surrounding the burst hole were evaluated. The experimental results showed that the stress response around the burst hole was intense and stress variation decreased as distance from the position to burst port increased. The gas pressure in the coal decreased sharply and oscillated several times during the burst process. The maximum rebound range was 0.05 MPa during this process. The decreasing rate of gas pressure reduced with the increase of the position‐burst port distance. The temperature response near the burst port was stronger than peripheral area. The gas internal energy was still the main energy source of coal and gas outbursts, accounting for 75% of the total energy, and played a key role in the burst process. The contribution of elastic potential energy was 22% under deep high‐stress conditions in this study. Based on the analysis of burst energy, the gas and stress were key factors of an outburst. [ABSTRACT FROM AUTHOR]

The acetylene‐terminated polyisoimide oligomers introducing 2,2′‐bis (trifluoromethyl)benzidine (TFMB) or 3,4′‐oxydiphthalic anhydride (3,4′‐ODA) as the diamine were synthesized, and short quartz fiber reinforced polyisoimide composites were prepared. The structure, processability, and thermal properties of polyisoimide oligomers were characterized. The mechanical properties and ablation protection performances of the composites were tested. The effects of TFMB on the processability and thermal properties of polyisoimides were studied. The application properties of short quartz fiber reinforced polyisoimide composites as thermal protection materials were evaluated by coal gas/oxygen ablation test system. These results showed that the introduction of TFMB into the polyisoimide structure can improve its solubility and heat resistance, as well as the ablation protection performances of the composites. The above results showed its potential application in the field of thermal protection materials. This makes it possible for polyisoimide composites to be used in the field of ablation protection. [ABSTRACT FROM AUTHOR]

By‐product gas is used as an alternative energy for steel mills to relieve the pressure of the fossil fuel crisis. In order to study the influence of blending by‐product gas on boiler operation, the multi‐fuel combustion experiments on the mixture of coke oven gas (COG), blast furnace gas (BFG), and lean coal were carried out in a 75t/h multi‐fuel combustion boiler so as to determine the most balanced fuel formula. The results indicated that the mixed combustion of COG and lean coal could improve the boiler efficiency. However, the balance of by‐product gas utilization in steel mills was destroyed for not using BFG. Although mixed combustion of BFG and COG improved the boiler efficiency, the boiler could only be operated under low load because of lower furnace temperature. After applying the most balanced flue ratio of BFG, COG, and lean coal, with heat value rations of 35%, 35%, and 30%, respectively, the efficiency of the boiler became 77.21%. The flue gas temperature lowered 4.5°C and the carbon content of fly ash and boiler slag were reduced by 1.06% and 1.09%, respectively. As a result, the stand coal consumption of the boiler decreased by 226.1 kg/h with the ratio of coal saving being 3.3%. [ABSTRACT FROM AUTHOR]

Coalbed methane (CBM) is an important resource of energy. For CBM recovery, sorption‐induced coal deformation can cause significant reservoir permeability change. Moisture content and coal pore morphology affect the gas adsorption capacity and can alter the coal deformation of the coal seam. Therefore, it is crucial to establish a coal gas moisture‐coupled model for CBM production prediction. However, there are currently insufficient data available for quantitative analyses. In this paper, a series of typical sorption‐induced strain experiments were carried out during methane adsorption and desorption on coal samples with different metamorphic degrees and moisture content. The pore morphology and adsorption capacity of coals were measured to analyze the reason for different deformation of coals with various pore structures and moisture. Results show that the adsorption capacity and deformation is corresponding to the specific surface area of micropore, which first decreases and then increases with coal ranks. The deformation and adsorption gas content of dried coals is greater than that of natural moisture coals, which means that moisture can reduce the sorption capacity of coals, resulting in the decrease of gas adsorption‐induced coal deformation. There is also residual deformation of coal samples after gas desorption caused by the residual adsorbed gas in coals. This paper quantitatively investigates the effects of pore characteristics and moisture on coal deformation and the internal mechanism. This work will provide essential information for building out a fully cross‐coupled model of coal gas‐moisture relationships for CBM production prediction. [ABSTRACT FROM AUTHOR]

Any disturbance in the ventilation system of a mine during a coal and gas outburst can lead to secondary disasters. This is because, on the one hand, the expansion power of the outburst source makes the airflow in the ventilation system countercurrent, causing the gas in this system to exceed the allowable limit. On the other hand, the airflow density changes because of the outburst and the consequent airflow mixing in the mine roadway, thereby changing the natural wind pressure. From this, the concept of natural gas wind pressure is proposed, and a calculation method for this pressure in a 3D model mine ventilation system is derived. For the "11.10" major coal and gas outburst that occurred in Shizhuang Coal Mine in Qujing, Yunnan Province, the entire process of the counter flow and gas dispersion flow in the main and auxiliary shafts is analyzed using the TF1M 3D simulation program, including the dynamic change in the natural wind pressure in the mine in each stage. The simulation shows that during the gas outburst period, the natural gas pressure of the countercurrent circuit is greater than that of the main fan. Between 140 s and 225 s following the outburst, the natural wind pressure once overcomes the fan pressure and reverses the airflow in the 1824 transport roadway, and the gas is withdrawn from the 1727 service point. Evidently, the natural pressure of the gas produced by the outburst affects the mine ventilation system. In the event of a coal and gas outburst in a private village coal mine, if the natural gas wind pressure can be reasonably utilized and the main fan stopped or the entire mine reversed in time, casualties may be minimized. Scholars studying coal and gas outburst mines should pay attention to mine airflow disorder due to the varying natural gas wind pressure when an outburst occurs and perform simulation drills of the outburst beforehand. Thus, a scientific emergency management plan for mine disaster prevention and reduction can be formulated. [ABSTRACT FROM AUTHOR]

The study analysed how carbon dynamics were influenced by the transition from coal or natural gas to forest biomass on a number of district heat and combined heat and power plants in Denmark. For 10 plants, we calculated the cumulative net carbon emissions over time (t) from the fuel transition (CCE(t)) and carbon payback time (CPT), a measure of the time it takes for a fuel transition to biomass to reduce the amount of carbon emitted to the atmosphere relative to a continuation of using fossil fuels. Subsequently, we derived the relative cumulative net carbon emissions (RCCE(t)), as a measure of the carbon emission savings/costs induced by the fuel transition. Finally, we performed sensitivity analyses of key parameters, with special focus on emissions from indirect/market mediated effects. For fuel transitions from coal to biomass, CPT ranged from 0 to 13 years indicating that carbon emission benefits were achieved at the latest after 13 years. Relative cumulative net carbon emissions 30 years after the fuel transition (RCCE(30)) ranged from 0.29 to 0.85 corresponding to emission savings of 15–71% relative to continued use of coal. For fuel transitions from natural gas to biomass, CPT ranged from 9 to 34 years and RCCE(30) from 0.81 to 1.03. Sensitivity analyses showed that the use of truly residual biomass (harvest residues or industrial residues with no alternative use), biomass harvest from productive forests and short transport distances are instrumental in achieving a short carbon payback time and large emission savings. The quantification of indirect or market mediated GHG emissions is controversial and uncertain. We analysed additional carbon emissions related to indirect land use change (iLUC), indirect wood use change (iWUC) and indirect fuel use change (iFUC). Including iLUC added 1–4 years, iWUC added 1–3 years and iFUC added 1 year to the mean CPT. [ABSTRACT FROM AUTHOR]

Conversion of ethanol to hydrocarbons by porous zeolite ZSM‐5 is a sustainable alternative compared to crude oil, gas or coal conversion. A quantification and description of micro‐ and macroscopic deactivation kinetics with basic transport and reactor models reveals deeper insight into the dynamics of coking and product formation at varying contact time. A new first order deactivation model helps to separate linear deactivation and autocatalytic acceleration of catalyst decay. A deeper look into product formation reveals a change in selectivity during initiation and deactivation phase from bigger build‐up C5+ to smaller cracking products C3 after formation of coke precursors, which does not coincide with site‐loss and reduction of contact time alone. Thereby, deactivation and switching selectivity in the hydrocarbon pool concept become more deterministic, which paves the way to more selective ethanol conversion processes. [ABSTRACT FROM AUTHOR]

As an important indicator, permeability can predict the gas drainage yield and prevent the mine gas disasters. We first reviewed our previous inversion method to investigate permeability coefficient of gas in coal particles; however, the relationship between permeability and adsorption pressure had not been summarized and explained theoretically. Here, a permeability evolution model including two crucial parameters of initial permeability and deformation coefficient was developed. The inversion gas permeability coefficients were converted into permeability, and then, the permeability of the same coal sample was fitted according to the evolution model. The results show that (i) the modeled results are matched reasonably well with the inversion permeability data, and thus, this model has been validated; and (ii) as volatile matter content increases, the initial permeability decreases exponentially, but the deformation coefficient basically grows in a linear trend. These two parameters are coupling to lead to a negative exponential decrease in permeability as gas pressure rises. [ABSTRACT FROM AUTHOR]

Aiming at the problem that common flame arresters can only extinguish deflagration flame, but cannot effectively extinguish detonation flame in large pipelines, this paper proposes a novel structure of detonation arrester based on heat transfer theory to improve the detonation flame extinguishing efficiency. The flame arresting element is composed of a large disk with long triangular slits and is used as the quenching part of detonation arrester in a monolithic structure. Compared with common flame arrester consists of several small fires retarding elements, the proposed monolithic structure is safer due to its integrity. In addition, this paper explores the relationship between flame extinguishing ability, detonation pressure, and temperature change. This investigation determined that the diameter of the quenching part and the parameters(length and height) of the long triangular slits were the key factors affecting the quenching characteristics, and as the diameter and porosity increase, the detonation pressure at the front of the flame arrester will decrease. Finally, the rationality and applicability of the structure are verified by simulation experiments. These preliminary conclusions are helpful to reveal the nature of the proposed structure and solve the technical problem of preventing detonation flame propagation of coal mine gas in large pipelines. [ABSTRACT FROM AUTHOR]

Realizing ultra‐low NOx emissions during coal combustion is currently a development trend and technical bottleneck of coal combustion technology. To further exploit the low‐nitrogen potentialities in preheating combustion technology, the preheating characteristics, combustion characteristics, and NOx emission characteristics of pulverized coal, after changing operating parameters such as the air equivalence ratio of circulating fluidized bed, preheating temperature, combustion temperature, and air equivalence ratio in the reduction zone, are explored. The experimental results show that changing the operating parameters has a great impact on the composition of high‐temperature coal gas, the particle size, apparent morphology, and specific surface area of the high‐temperature preheated char after preheating. Properly adjusting the operating parameters can effectively reduce NOx emissions. Based on the explored principle, experiments were designed, and the goal of reducing the initial NOx emissions from coal combustion to less than 50 mg/m3 (the average emissions were 46 mg/m3 [@ 6% O2]) was successfully achieved. The research of this paper provides the most basic experimental guidance and theoretical support for achieving ultra‐low NOx emissions during the engineering pulverized coal combustion. [ABSTRACT FROM AUTHOR]

The Dongpu Depression is one of the major petroliferous structures in the Bohai Bay Basin of eastern China. The Shahejie Formation is the key target unit for petroleum exploration in the Dongpu Depression. The current studies on this fossiliferous structure mainly focus on the northern depression, and the detailed study on the southern part of the depression is still scarce. To further study on the southeast subsag located in the southern part of this depression, we examined the geochemical characteristics and origin of petroleum using stable carbon isotopes, components of crude oil and natural gas, micro Fourier transform infrared spectroscopy (FT‐IS), gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS). Fluid inclusions and 1D model were employed to reconstruct the burial and thermal history and indicate the timing of hydrocarbon generation. Finally, the petroleum exploration in this region is guided based on the combination of geochemical results and geological setting. The result of geochemical characteristics of crude oils indicates the oil was from the combination of algal and terrestrial plants, deposited in reducing to sub‐oxic and fresh to marginally brackish environment. Furthermore, the oil in the northeastern part could be traced to the Haitongji subsag and has relatively lower thermal maturity than that in the central part. Stable carbon isotope data suggest that natural gas is a mixed oil‐type and coal‐type gas. The equation estimated indicates that natural gas in the northeast is mainly oil‐type gas, with an average ratio of 80.0%, whereas coal‐type gas is dominant in the central part (average percentage: 74.3%). Geochemical characteristics of hydrocarbon indicate that the Changyuan Fault was a migration pathway for the northeastern petroleum, whereas it gradually changed to be sealed towards the central part. [ABSTRACT FROM AUTHOR]

Hydraulic methods have been extensively employed to improve the production rate of commercially viable coalbed methane and prevent potential mining disasters resulting from the production of this methane by increasing the permeability of coal seams. In this paper, an experimental system with a stirrer was utilized to study the effects of water injection on the gas desorption characteristics of coal seams. Pressure‐released desorption values and total gas desorption values under conditions of different adsorption equilibrium pressures and water contents were determined. The results show that both the free gas and the adsorbed gas could be replaced by the injected water, causing the system pressure to increase significantly. When releasing the system pressure, the gas desorption value of the water‐injected coal sample was reduced. After water injection, the total desorption value of the coal was increased. Thus, water injection could help to promote coal gas desorption. [ABSTRACT FROM AUTHOR]

Using deposition observations from precipitation samples collected by the National Atmospheric Deposition Program at 125 sites across the United States, we show that the mean wet deposition flux of non‐sea‐salt chloride (NSS Cl−) has decreased by 83% throughout the eastern United States between 1998 and 2018. We find that 30% of the sites switch from having excess Cl− to being depleted in Cl−. We attribute the observed decreases in NSS Cl− deposition to a 95% decrease in U.S. anthropogenic HCl emissions since 1998. We propose that industry emission controls that remove HCl as a cobenefit of NOx and SO2 have caused significant decreases in NSS Cl− deposition throughout the eastern United States, in addition to shifts from coal to natural gas and to coal with lower Cl− content. Our analysis implies that the lower tropospheric reactive inorganic chlorine burden was larger over the United States in the past than it is today. Plain Language Summary: Comparing the relative ratio of sodium and chloride that is deposited in rainwater, it is possible to separate out whether that chloride is from anthropogenic sources, like burning coal, or from natural sources, like seawater. Using rainwater samples collected at 125 sites by the National Atmospheric Deposition Program between 1998 and 2018, we show that the amount of chloride deposited in rainwater from anthropogenic sources has decreased by 83% across the eastern United States. Power plant scrubbers designed to reduce emissions of SO2 and NOx, which lead to acid rain and smog, also remove emissions of HCl from burning coal, as a cobenefit. The widespread installation of these emission control technologies, together with a switch from coal to natural gas and to coal with lower chloride content, has resulted in a decrease in emissions of anthropogenic HCl by 95% in the last 21 years. We show that these anthropogenic HCl emission decreases are closely correlated with decreases of non‐sea‐salt sources of chloride in rainwater. Our results suggest that the impacts of chlorine on air quality and climate were significantly larger in the past over the United States than they are today. Key Points: Wet deposition of non‐sea‐salt chloride has decreased 83% on average since 1998 across the eastern United States at sites with significant trendsDecreases in deposition of non‐sea‐salt chloride are well correlated with changes in sulfate deposition as well as decreasing HCl emissionsIn the southeastern United States, chlorine wet deposition patterns suggest weaker anthropogenically driven displacement of chloride from sea salt [ABSTRACT FROM AUTHOR]

This Essay outlines the life path and scientific achievements of Nikolai Zelinsky to testify to his contributions to organic chemistry, catalysis, and petrochemistry. His legacy includes four name reactions (the Hell–Volhard–Zelinsky reaction, 1887; the Zelinsky–Stadnikov reaction, 1906; Zelinsky irreversible catalysis, 1911; the Zelinsky–Kazansky acetylene trimerization, 1924), pioneering contributions to the main oil‐refining processes (thermal cracking, catalytic cracking, hydrodesulfurization, reforming, and oxidative regeneration of coked catalysts), the coal gas mask, Pd/C and other supported catalysts, and a very large scientific school. [ABSTRACT FROM AUTHOR]

This study evaluates the optimal expansion of the electricity sector of the BBIN (Bangladesh, Bhutan, India, and Nepal) sub‐region with a detailed analysis of unevenly distributed resources and electricity demand, by developing a multi‐regional dynamic power sector optimization model, characterized by 27 nodes, 45 fuel transport lines, and 63 transmission lines in hourly temporal resolution. Scenarios developed in this paper assess the impact of 2 °C Paris agreement on production, transportation, and consumption of indigenous resources like coal and gas, the share of renewables and nuclear in the power generation mix, the utilization of huge untapped hydro resources through an expansion of cross‐border transmission lines. The simulation results show that hydro, wind, nuclear, and PV will be the dominant power sources, thus reducing the current share of coal, under carbon regulation scenario. The requirements of PV exceed its estimated commercially exploitable potential in most of the nodes in the nuclear‐restricted scenario. Expanding cross‐border transmission capacity will be an effective way to exploit untapped hydro resources so that Bangladesh and India can import power from Bhutan and Nepal. Although there is a slight increase in coal demand in the future, capacity expansion of fuel networks is not economical under adopted emission levels. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

With the increase of mining depth, the occurrence mechanism of coal and gas outburst becomes more complex, and stress‐dominated outburst disaster has become one of the major safety problems in deep coal mines. Therefore, stress relief of coal seam has become an urgent technical demand for outburst prevention method in deep mines. In this study, based on zonal disintegration characteristics of deep surrounding rock, a regional strip outburst prevention method, called strip stress relief combined with gas extraction through stress‐relief floor roadway, was proposed, and relevant in‐site investigations were carried out in the Qujiang coal mine in China. Our results show that the zonal disintegration phenomenon occurs in the high‐stress surrounding rock at great depths, and induces the stress‐relief effect on the upper coal seam, in which the permeability and extraction radius of boreholes are increased greatly. The results of deformation and failure of surrounding rock of floor roadway show that from the surface to deep regions, fractured and nonfractured zones were alternatively distributed in the surrounding rock of deep floor roadways, the damage degree of surrounding rock was gradually weakened, and the width of fractured area was gradually reduced. The displacement of surrounding rock also presented the characteristics of alternative distribution of wave peak and trough. Moreover, the deformation and failure of surrounding rock presented a time‐dependent rheological behavior. In the stress‐relief zone, the coal seam permeability was enhanced significantly, with the maximum value being 43 times larger than that of the original coal seam. The effective gas extraction radius of the borehole was improved by 15%‐45%. During the driving period of coal roadways, the outburst risk prediction indexes K1 and S of the working face were lower than the critical value, and the driving speed of the coal roadway improved from 40 m per month to 100 m per month. This indicates that the proposed strip regional outburst prevention method can simultaneously reduce the ground stress and the gas content, and can effectively eliminate the outburst risk of coal roadway in deep mines. [ABSTRACT FROM AUTHOR]

The high‐pressure gas expansion‐induced deformation and dynamic fracture of coal are important parts of coal and gas outburst. To better understand the law of this process, laboratory experiments and numerical simulation are used to study the law of damage. A cavity with different pressures of CH4 or N2 was destroyed by a jack to achieve the rapid expansion of the gas and coal fracture inside. The particle size distribution of the coal particles before and after the experiment was measured, and the breakage ratio and the newly added surface area were calculated. The experimental results indicate that during the gas expansion process, the breakage ratio of coal and the newly added surface area clearly increase with the increase in gas pressure. Finally, a numerical model based on peridynamic theory was developed to simulate crack generation and the propagation of coal induced by the expansion of gases at different pressures. The numerical simulation results show that the higher the initial gas pressure is, the higher the number of failure units. Moreover, only when the gas pressure is large enough will the coal crack in various directions at the same time. [ABSTRACT FROM AUTHOR]

Protective coal layer (PCL) mining is a preferred regional method for preventing coal and gas outbursts; stress‐relief of PCL mining is the prerequisite of pressure‐relief gas drainage. In order to study the stress‐relief effect of PCL mining on protected coal seams and determine the protection scope of PCL mining under different inclinations, this paper uses physical simulations to study the stress‐relief law and deformation characteristics of the strata during upper PCL mining with a gentle inclination (25°), an intermediate inclination (45°), and a steep inclination (65°). The results show that as the coal seam dip increases, the degree of deformation and failure of the overburden strata gradually decreases, the severe subsidence and expansion area of the overburden strata tends to gradually develop in the uphill direction of the working face, and the floor strata underlying the protective seam significantly expand toward the goaf. However, the absolute value of the upward movement of the floor strata is much smaller than that of the roof strata; and the greater the dip angle, the greater the ratio of floor displacement to roof subsidence. The stress‐relief curve of the protected layer is approximately U‐shaped. As the inclination of the coal seam increases, the stress‐relief range decreases gradually. The maximum relief‐stress and the stress release coefficient of the protected layer initially increase and then decrease. The stress concentration coefficient of the protected coal seam initially increases first and then decreases in both uphill and downhill of the working face in the PCL. As the inclination increases, the stress‐relief angle of the downhill boundary initially increases and then decreases, while the stress‐relief angle of the uphill boundary decreases gradually. Our research results provide guidance for the delimitation of the protected scope of PCLs with different dip angles. [ABSTRACT FROM AUTHOR]

High gas mines and outburst mines contribute to more than 30% of the coal production capacity in China. In view of this, coordinating the development and use of coal and gas has become an urgent concern for China's coal industry. After years of efforts, the concept of a co‐mining mode for coal and gas in China has gone through many stages, including theoretical discussion, engineering application, and assumption of concepts. Three modes have been gradually developed: the Huainan mode, based on pressure relief co‐mining of a protective layer; the Jincheng mode, based on directional long borehole co‐mining; and the YangQuan/SongZao mode, based on cross‐layer borehole co‐mining. These modes provide strong direction and the impetus to solve current predicaments and challenges of coal mining in China. Under the concept of "green" extraction and the corresponding urgent needs for environmental protection, high efficiency, and energy‐saving extraction, experts and scholars in the coal industry are also exploring development trends for coal in the future. For example, researchers have suggested idealized mining methods for replacing traditional mining methods, including fluidized mining technology, intelligent unmanned mining technology, precision mining technology, green development of abandoned mines technology, and mining based on other technical means. [ABSTRACT FROM AUTHOR]

The gas permeability of a coal seam was the main factor determining the efficiency of gas extraction from the mines and was closely related to the coal damages. In this paper, a triaxial compression failure test of the raw coal was carried out in the gas seepage state using the MTS 815 rock mechanics testing system. The damage evolution law of the coal containing gas under triaxial compression was studied based on acoustic emission characteristics. The damage evolution parameters were determined using acoustic emission signals, and the relationship between the permeability and damage evolution of the coal containing gas was quantitatively analyzed. The results demonstrated that the acoustic emission signals could reflect the development of the damage and failure inside the coal, and the turning point of the acoustic emission characteristic curve marked different damage development stages. The periodic changes in the permeability of the coal samples were consistent with the damage change law, and some lag existed in permeability changes compared with damage evolution. The permeability of the coal containing gas saw a stepwise exponential growth with the damage development. The piecewise exponential function better reflected the relationship between the gas permeability and damage variables. [ABSTRACT FROM AUTHOR]

Summary: To reduce the pressure on underlying coal seam and maximize the mining efficiency of coal resource, narrow coal pillar mining technology is often used. However, for coal mines with high gas and spontaneous combustion, this technology can cause gas and coal spontaneous combustion composite disaster easily. In this paper, we adopted a new type of inorganic fire‐extinguishing material (IFEM) to prevent and control gas and coal spontaneous combustion composite disaster. The result shows that the destruction of narrow pillar caused by stress extrusion and mining disturbance is the internal cause of gas and coal spontaneous combustion composite disaster. IFEM can go deep into the cracks of coal mass to seal up the cracks and reduce gas exchange between roadway and adjacent goaf. Meanwhile, it is full of moisture in the interior, which can reduce the temperature of coal mass through evaporation and heat absorption. The IFEM has the characteristics of high water retention, strong fluidity, and strong flame retardant, which can inhibit the generation of free radicals in coal mass at both physical and chemical levels, prevent the spontaneous combustion of coal mass, and reduce the occurrence of composite disasters of gas and coal spontaneous combustion. Highlights: The crack inside the narrow coal pillar develops, and the gas permeability is good.The combined disaster in the narrow coal pillar working face is serious.IFEM can seal cracks and increase the strength of narrow coal pillars.IFEM can inhibit the generation of free radicals in coal and prevent coal from contact with oxygen. [ABSTRACT FROM AUTHOR]

Zn‐based MCM‐41 supporter sorbents were prepared using the microwave in‐situ oxidation method. Other sorbents were heated using a conventional heating method to contrast the performance for H2S removal. The sorbents were tested at 500°C in fixed reactor and dried simulated Texaco coal gas was employed for the sulphurized atmosphere. The results show that sorbents prepared by microwave oxidation had a better toleration for the adsorption of H2S. A 13.2% improvement occurred in the sulphur capacity of the sorbents heated by the microwave method. XRD, SEM with EDS‐element mapping, TEM, N2 adsorption, and XPS were used to characterize the properties of the sorbents. Due to the selective heating of the microwave and the superiority of the in‐situ oxidation method, the sorbents heated by microwave exhibited more appropriate structures for sulphurization. Meanwhile, the even heating environment supplied by the microwave resulted in a more uniform distribution of the active component. The microwave also had an effect on the chemical bond and reduced the binding energy of the active component, which enhanced the reactivity between the H2S and the sorbents. The preferable features generated by microwave in‐situ oxidation accelerate the replacement of S to O, and therefore the Zn‐based MCM‐41 sorbents prepared by the microwave method have an increased capability for H2S removal in high temperature coal gas. [ABSTRACT FROM AUTHOR]

Coal preheating combustion technology was adopted to achieve stable combustion and low NO emission of Shenmu semicoke, and an air‐staging method was also used to further reduce NO emission. A series of experiments have been launched on a 30‐kW coal preheating combustion test rig with a coaxial jet triple channel nozzle. In the study, coal preheated characteristics, combustion behavior, and the formation and destruction mechanisms of NO were discussed. Shenmu semicoke could be preheated up to a temperature above 840°C, and stable combustion was easily established; ~63% of the volatile and 59% of carbon were released and converted into coal gas in the self‐preheating burner. Flame images along the axis of the down‐fired combustor were gained, and the images was dark red without obvious flame fronts. The initial generation of NO in the near field of the preheated fuel nozzle exit had impacts on the NO emission, and lower initial NO generation might result in lower NO emission. By decreasing the inner secondary gas (air), increasing the external secondary air and adding CO2 in the secondary gas, the initial NO could be inhibited effectively, which finally controlled the NO emission. However, the CO emission might increase in turn generally. In the research, the NOX emissions were <180 mg/m3 (@6% O2) with the lowest <80 mg/m3. To achieve an optimal scheme of NO emission and CO emission, some adjustment methods need to be applied synchronously. [ABSTRACT FROM AUTHOR]

In this study, an indicator model and system for coal and gas outburst prediction are identified and established based on gas geological anomalies, mining stress, and gas emission characteristics. In this regard, the coal and gas outburst prevention techniques and mine rules in China are taken into account. In addition, using this model, an online integrated system and database for coal and gas outburst prediction were built for Xinjing Mine in Shanxi Province. The application results of the prediction system indicate that the system software and hardware can guarantee early warning of coal and gas outburst. The system is continuous and stable, and the early warning results are issued in a timely and accurate manner. The accuracy of the early warning results is high and consistent with the actual risk of the mine. [ABSTRACT FROM AUTHOR]

Predrainage of gas by cross‐boreholes is an important method to prevent coal and gas outbursts in the process of a coal roadway excavation. Limitations of technologies and poor effects of preventing coal and gas outbursts occur in the coal seam with a soft layer. In this study, a new hydraulic caving technology for cross‐boreholes has been proposed to solve this problem. A CT equipment was used to observe the development of coal fissures around cross‐boreholes in the coal seam with a soft layer. The plastic zone range and permeability distribution of ordinary hydraulic slotting technologies and the new hydraulic caving technology also were compared by numerical simulation. The field test of hydraulic caving was taken in the Xuehu Mine (China). The results show that the fracture development degree of soft coal is greater than that of hard coal at the same distance from cross‐boreholes. The fracture development degree in the plastic zone is greater than that in the elastic zone. The hydraulic caving technique can achieve the same effect as the ordinary hydraulic slotting with less workload. The mass of coal discharged from a cross‐borehole was 1.15 t/m and the average methane concentration of single drainage borehole increased by 1.09‐4.1 times, and the average methane extraction amount of single drainage borehole increased by 6.06 times. Elimination of coal and gas outburst had been completed after 110 days of extraction in the area of hydraulic caving, and Q and S values are lower than the critical value during roadway excavation. It is conclusion that hydraulic caving technique can effectively improve the permeability and rapidly eliminate coal and gas outburst in the coal seam with a soft layer. [ABSTRACT FROM AUTHOR]

We report laboratory experiments to investigate the dynamic failure characteristics of outburst‐prone coal using a split Hopkinson pressure bar (SHPB). For comparison, two groups of experiments are completed on contrasting coals—the first outburst‐prone and the second outburst‐resistant. The dynamic mechanical properties, failure processes, and energy dissipation of both outburst‐prone and outburst‐resistant coals are comparatively analyzed according to the obtained dynamic compressive and tensile stress‐strain curves. Results show that the dynamic stress‐strain response of both outburst‐prone and outburst‐resistant coal specimens comprises stages of compression, linear elastic deformation, then microfracture evolution, followed by unstable fracture propagation culminating in rapid unloading. The mechanical properties of both outburst‐prone and outburst‐resistant coal specimens exhibit similar features: The uniaxial compressive strength and indirect tensile strength increase linearly with the applied strain rate, and the peak strain increases nonlinearly with the strain rate, whereas the elastic modulus does not exhibit any clear strain rate dependency. Differences in the dynamic failure characteristics between outburst‐prone and outburst‐resistant coals also exist. The hardening effect of strain rate on outburst‐prone coal is more apparent than on outburst‐resistant coal, which is reflected in the dynamic increase factor at the same strain rate. However, the dynamic strength of outburst‐prone coals is still lower than that of outburst‐resistant coals due to its low quasi‐static strength. The dissipated energy of outburst‐prone coal is smaller than that of outburst‐resistant coal. Therefore, the outburst‐prone coal, characterized by low strength, high deformability, and small energy dissipation when dynamically loaded to failure, is more favorably disposed to the triggering and propagation of gas outbursts. [ABSTRACT FROM AUTHOR]

Coal measure source rocks, located in the Xihu Sag of the East China Sea Shelf Basin, were analyzed to define the hydrocarbon generation potential, organic geochemistry/petrology characteristics, and coal preservation conditions. The Pinghu source rocks in the Xihu Sag are mainly gas‐prone accompany with condensate oil generation. The coals and shales of the Pinghu Formation are classified from "fair" to "excellent" source rocks with total organic carbon (TOC) contents ranging from 25.2% to 77.2% and 1.29% to 20.9%, respectively. The coals are richer in TOC and S1+S2 than the shales, indicating that the coals have more generation potential per unit mass. Moreover, the kerogen type of the organic matter consists of types II‐III and III, which the maturity Ro ranges from 0.59% to 0.83%. Petrographically, the coals and shales are dominated by vitrinite macerals (69.1%–96.8%) with minor proportions of liptinite (2.5%–17.55%) and inertinite (0.2%–6.2%). The correlation between maceral composition and S1+S2 indicates that the main contributor to the generation potential is vitrinite. Therefore, the coals and shales of the Pinghu Formation has good hydrocarbon generation potential, which provided a good foundation for coal measure gas accumulation. Furthermore, coal facies models indicates that the Pinghu coal was deposited in limno‐telmatic environment under high water levels, with low tree density (mainly herbaceous) and with low‐moderate nutrient supply. Fluctuating water levels and intermittent flooding during the deposition of peat resulted in the inter‐layering of coal, shale and sandstone, which potentially providing favorable preservation conditions for coal measure gas. [ABSTRACT FROM AUTHOR]

Coal‐bearing strata are widespread in the western Great Khingan Mountains. Abundant coal resources have been found in the Jurassic Alatanheli Groups, the Cretaceous Bayanhua Groups, the Damoguaihe Formation and the Yimin Formation. The organic geochemical characteristics were analyzed in combination with hydrocarbon source rock evaluation and molecular organic geochemistry experiments, and the coal gas potential of coal seams was evaluated. The source rock evaluation results indicated that the Mesozoic coal samples have the characteristics of high organic matter abundance (TOC>30%), low maturity (Ro values of approximately 0.6%), and type III composition. The hydrocarbon generation potentials of the Alatanheli Groups and Bayanhua Groups are high, while the generation potentials of the Damoguaihe Formation and the Yimin Formation are low. The results of geochemistry show that the depositional environment of the coal seam was a lacustrine, oxidizing environment with a low salinity, and the source of the organic matter was mainly higher plants. Affected by weak degradation, the coal seams mainly formed low‐maturity gas of thermal catalytic origin. The Cretaceous coal seams contain a large amount of phytoplankton groups deposited in a low‐stability environment affected by a transgression event, and the potential range varied widely. For the Jurassic coal seams, the depositional environment was more stable, and the coal seams feature a higher coal‐forming gas potential. [ABSTRACT FROM AUTHOR]

Creep behavior is one of the most important mechanical behaviors of coal. In the present study, we systematically carried out a series of creep experiments of briquette samples under triaxial compression and gas pressure. The experimental results showed that the creep deformation characteristics of coal were related to deviatoric stress and gas pressure. The accelerating creep stage initiated when the deviatoric stress reached or exceeded the yield stress until failure took place. In contrast, when the deviatoric stress was less than the yield strength, only transient and steady creep stage occurred. Besides, gas pressure played a positive role in the creep process of coal. The axial strain of coal slightly increased with gas pressure (range from 0.13 to 0.40 MPa) when the effective triaxial stress remained constant. For example, in the steady creep stage (σ1 = 9 MPa, p = 0.13 MPa), the axial strain of sample S1 is 2.710% and that of sample S2 is 3.361%, that is, coal samples with high gas pressure have higher axial strain. Moreover, gas pressure has two main effects on the mechanical behavior of coal. One is that the coal adsorbs gas molecules resulting in swelling strain and swelling stress, and the other is that the gas pressure may compress the coal particles. Considering the swelling stress and gas pressure, we intensively studied the effective stress formula of coal containing gas. Then, the effective stress was taken into consideration in the nonlinear Nishihara creep model. Furthermore, the tertiary creep factor n was introduced in the nonlinear model to control the creep deformation evolution with time so that the nonlinear model could accurately describe the full creep stage of coal. In contrast, due to the lack of such a controlling parameter, the Nishihara model failed to reproduce the accelerating creep stage. [ABSTRACT FROM AUTHOR]

To explore practical approaches for the evaluation of favorable shale gas areas, a structural decomposition analysis with respect to the index system, evaluation criteria, weight determination, and evaluation methods was carried out. Five types of indexes were determined from 25 subindexes that formed the index system, and improved whitenization weight functions are proposed to establish evaluation criteria. The index weights calculated using entropy weight and Euclidean distance methods are consistent, whereas the weights determined by gray relational analysis are significantly affected by the relative number of indexes and evaluation objects, selected mother factor, and resolution coefficient. The significant linear positive correlation between the relative approach degree values calculated using TOPSIS and the scores obtained using fuzzy comprehensive evaluation (FCE) is indicative of a consistent evaluation result, but it should be noted that extreme indicator values can have strong effects on the evaluation using the fuzzy similarity method. Finally, an exploration strategy for China's shale gas is suggested: Areas with weak reformation and relatively low maturity are expected to be favorable for marine shale production in South China, and continental and transitional shale‐bearing basins are promising for the prospecting multiple‐origin shale gas and coal measure gas, respectively. [ABSTRACT FROM AUTHOR]

Coal and gas outburst is a potentially fatal risk during the mining of gassy coal seams, which seriously threatens the safe mining of collieries. To understand the outburst mechanism and evolution rules, a new apparatus (LSTT) was developed to conduct simulated experiment. In the context of an outburst accident in Dingji coal mine, the authors launched an authentic outburst experiment to replay the outburst accident. Experimental apparatus, similar criterion, coal‐like materials and gas sources, and experimental design were discussed systematically in this paper. Experimentally, the study analyzed the geo‐stress has significant influence on the outburst evolution. At the driving face, the stress concentration possibly caused gas outburst, under the influence of mining‐induced stress. After the outburst occurred, the stress balance of the coal changed, resulting in the instability of the coal. Furthermore, the elastic energy, gas enthalpy, and gravitational potential energy were released rapidly. The experimental result stated that outburst coal has the sorting characteristics, in line with the field outburst law. The intensity prediction model has been built based on the energy model. Moreover, the factors that impact outburst intensity were analyzed. In the process of coal and gas outburst, the gas enthalpy of gas and the elastic potential of coal are the main energy sources. This study provides guidance for the development of the outburst mechanism and outburst mine management. [ABSTRACT FROM AUTHOR]

The Canadian regulations on carbon dioxide emissions from power plants aim to lower the emissions from coal‐fired units down to those of natural gas combined cycle (NGCC) units. Since coal is significantly more carbon intensive than natural gas, coal‐fired plants must operate at higher net efficiencies and implement carbon capture to meet the new regulations. Calcium looping (CaL) is a promising post‐combustion carbon capture (PCC) technology that, unlike other capture processes, generates additional power. By capturing carbon dioxide at elevated temperatures, the energy penalty that carbon capture technologies inherently impose on power plant efficiencies is significantly reduced. In this work, the CO2 capture performance of a calcium‐based sorbent is determined via thermogravimetric analysis under relatively high carbonation and low calcination temperatures. The results are used in an aspenONE™ simulation of a CaL process applied to a pressurized fluidized bed combustion (PFBC) system at thermodynamic equilibrium. The combustion of both natural gas and coal are considered for sorbent calcination in the CaL process. A sensitivity analysis on several process parameters, including sorbent feed rate and carbonator operating pressure, is undertaken. The energy penalty associated with the capture process ranges from 6.8–11.8 percentage points depending on fuel selection and operating conditions. The use of natural gas results in lower energy penalties and solids circulation rates, while operating the carbonator at 202 kPa(a) results in the lowest penalties and drops the solids circulations rates to below 1000 kg/s. [ABSTRACT FROM AUTHOR]

The water content distribution in a coal body is closely related to the gas distribution. It is difficult to directly determine the water content distribution in the process water imbibition. To retrieve the water content by the resistivity value and establish a relationship between the resistivity and water content, the response characteristics of the resistivity and water content of remolded coal formed under different loads are studied by a self‐designed resistivity experimental system. The results show that the resistivity of the remolded coal decreases over time during the imbibition process, including a rapidly decreasing stage and a slowly decreasing stage. The resistivity of the remolded coal is related to the water in the macropore in the rapidly decreasing stage. In the slowly decreasing stage, the resistivity is related to the contact between coal particles. The pressing load, imbibition range, and imbibition speed are negatively correlated with porosity. The resistivity of the steady state is also negatively correlated with the water content and pressing load. The relationship between the resistivity of the steady state and the water content fit a power function. This study reveals the law of resistivity and the water content during the imbibition process and provides an effective methodology to bridge the gap for measuring water content distribution during the imbibition process. [ABSTRACT FROM AUTHOR]

This paper proposes a coupled model of waterjet cutting coal containing gas with the Arbitrary Lagrange‐Euler algorithm assistance. The dynamic evolution of coal damage and the cutting performance under different jet conditions, including jet pattern (submerged/nonsubmerged state), jet velocity, nozzle diameter, and the initial standoff distance, are investigated by tracing the number of failure elements and the stress distribution. Afterward, the gas flow model is built to study interactions of the discharged coal amount and the effective drainage radius at different periods with COMSOL software. The numerical results show the coal cutting performance of nonsubmerged jets is much better than that of submerged jets. Under submerged conditions, the penetration length increases with jet velocity and nozzle diameter, but decreases with the initial standoff distance. Moreover, the effective drainage radius of nonsubmerged waterjet is substantially greater than that of submerged jet. The increasing trend of the effective drainage radius slows down after 3 months with gas flow attenuation. Under the special submerged circumstances, the difference of coal cutting performance caused by the two jet patterns should be fully considered in order to reasonably arrange the spacing of boreholes. [ABSTRACT FROM AUTHOR]

Summary: Around the world, several dozen deep sedimentary aquifers are being used for storage of natural gas. Ad hoc studies of the microbial ecology of some of them have suggested that sulfate reducing and methanogenic microorganisms play a key role in how these aquifers' communities function. Here, we investigate the influence of gas storage on these two metabolic groups by using high‐throughput sequencing and show the importance of sulfate‐reducing Desulfotomaculum and a new monophyletic methanogenic group. Aquifer microbial diversity was significantly related to the geological level. The distance to the stored natural gas affects the ratio of sulfate‐reducing Firmicutes to deltaproteobacteria. In only one aquifer, the methanogenic archaea dominate the sulfate‐reducers. This aquifer was used to store town gas (containing at least 50% H2) around 50 years ago. The observed decrease of sulfates in this aquifer could be related to stimulation of subsurface sulfate‐reducers. These results suggest that the composition of the microbial communities is impacted by decades old transient gas storage activity. The tremendous stability of these gas‐impacted deep subsurface microbial ecosystems suggests that in situ biotic methanation projects in geological reservoirs may be sustainable over time. [ABSTRACT FROM AUTHOR]

To further more deeply understand the influence of cyclic loading‐unloading on coal seams during mining and reduce the rock burst and coal and gas outburst disasters and ensure safety during coal mining, triaxial cyclic loading‐unloading tests were performed on coal samples. The permeability recovery rate, residual deformation, and dissipated energy ratio were defined to analyze the evolution in the characteristics of permeability, deformation, and energy observed during the triaxial cyclic loading‐unloading test. The results show as following: (a) The absolute permeability recovery rate first gradually decreases and then increases before failure, while the relative permeability recovery rate decreases sharply during the compaction stage, remains stable during the elastic phase, and gradually increases before failure; (b) The cumulative residual deformation increases with increase number of cyclic loading‐unloading, while relative residual deformation first decreases gradually, then stabilities, and then rises sharply before failure; (c) With increases in deviatoric stress, the total energy of coal samples increased as an exponential function. The dissipated energy ratio gradually decreased in the initial stages of cyclic loading‐unloading, then tended to stabilize in the elastic stage and then increase gradually before failure. This study provides precursor conditions for the early warning of rock burst and coal and gas outburst disasters, which has great importance for reducing coal mine dynamics disasters. [ABSTRACT FROM AUTHOR]