Coal Extraction Research Articles

Exploration and application of microbial method to enhance the effect of hydraulic fracturing on coal seam permeability enhancement and gas extraction

The efficient extraction of gas from low-permeability coal seams is an urgent problem in coal mine safety production. The traditional gas extraction technology generally suffers from problems that limited penetration enhancement or extraction effect, low construction efficiency, large workload, etc. Thus, it is especially urgent and important to explore the new technology applicable to efficient underground gas extraction. In this paper, based on the principle of hydraulic fracturing to increase permeability, we innovatively propose a technique to enhance the effect of hydraulic fracturing to increase permeability and further improve the efficiency of gas extraction using the gas desorption activity of native microorganisms in coal seams. Herein, the composition of the primary microbial community of a coal seam in Xinji No.2 mine was analyzed by bacterial and archaeal 16SrDNA amplicon sequencing, the community structure of the main functional microorganisms was clarified, the optimal combination of functional microorganisms for organic matter degradation in coal seam under anaerobic culture conditions was obtained. Besides the Biolog microplate technology was used to screen the nutrients of the excitation carbon source to stimulate the rapid decomposition of coal organic matter by microorganisms and to define the optimal ratio of the excitation carbon source to microorganisms. Finally, the effect of this technology on the application of coal seam fracturing and gas extraction was tested through field industrial tests, revealing that the extraction effect of this technology was more significant than that of the common coal seam perforation extraction technology. The results of this paper provide a new technical idea for gas extraction from low permeability coal seams, which is an important reference value for subsequent similar studies.

Assessment of dimethyl sulphide odorous emissions during coal extraction process in Coal Mine Velenje

Underground coal extraction at Coal Mine Velenje occasionally gives rise to odour complaints from local residents. This manuscript describes a robust quantification of odorous emissions of mine sources and a model-based analysis aimed to establish a better understanding of the sources, concentrations, dispersion, and possible control of odorous compounds during coal extraction process. Major odour sources during underground mining are released volatile sulphur compounds from coal seam that have characteristic malodours at extremely low concentrations at micrograms per cubic metre (μg/m3) levels. Analysis of 1028 gas samples taken over a 6-year period (2008–2013) reveals that dimethyl sulphide ((CH3)2S) is the major odour active compound present in the mine, being detected on 679 occasions throughout the mine, while hydrogen sulphide (H2S) and sulphur dioxide (SO2) were detected 5 and 26 times. Analysis of gas samples has shown that main DMS sources in the mine are coal extraction locations at longwall faces and development headings and that DMS is releasing during transport from main coal transport system. The dispersion simulations of odour sources in the mine have shown that the concentrations of DMS at median levels can represent relatively modest odour nuisance. While at peak levels, the concentration of DMS remained sufficiently high to create an odour problem both in the mine and on the surface. Overall, dispersion simulations have shown that ventilation regulation on its own is not sufficient as an odour abatement measure.

Numerical modeling on strain energy evolution in rock system interaction with energy-absorbing prop and rock bolt

The interaction mechanism between coal and rock masses with supporting materials is significant in roadway control, especially in deep underground mining situations where dynamic hazards frequently happened due to high geo-stress and strong disturbed effects. This paper is to investigate the strain energy evolution in the interaction between coal and rock masses with self-designed energy-absorbing props and rock bolts by numerical modeling with the finite difference method. The interaction between rock and rock bolt/prop is accomplished by the cables element and the interface between the inner and outer props. Roadway excavation and coal extraction conditions in deep mining are numerically employed to investigate deformation, plastic zone ranges, strain energy input, accumulation, dissipation, and release. The effect on strain energy input, accumulation, dissipation, and release with rock deformation, and the plastic zone is addressed. A ratio of strain energy accumulation, dissipation, and release with energy input α, β, γ is to assess the dynamic hazards. The effects on roadway excavation and coal extraction steps of α, β, γ are discussed. The results show that: (1) In deep high geo-stress roadways, the energy-absorbing support system plays a dual role in resisting deformation and reducing the scope of plastic zones in surrounding rock, as well as absorbing energy release in the surrounding rock, especially in the coal extraction state to mitigate disturbed effects. (2) The strain energy input, accumulation is dependent on roadway deformation, the strain energy dissipation is relied on plastic zone area and disturbed effects, and strain energy release density is the difference among the three. The function of energy-absorbing rock bolts and props play a key role to mitigate strain energy release density and amount, especially in coal extraction condition, with a peak density value from 4×104 to 1×104 J/m3, and amount value from 3.57×108 to 1.90×106 J. (3) When mining is advanced in small steps, the strain energy accumulation is dominated. While in a large step, the released energy is dominant, thus a more dynamic hazards proneness. The energy-absorbing rock bolt and prop can reduce three times strain energy release amount, thus reducing the dynamic hazards. The results suggest that energy-absorbing props and rock bolts can effectively reduce the strain energy in the coal and rock masses, and prevent rock bursts and other hazards. The numerical model developed in this study can also be used to optimize the design of energy-absorbing props and rock bolts for specific mining conditions.

Preservation, diagenetic transformation and paleoecological significance of fungal saccharides from lignites and fossil wood

Fungi are a common component of terrestrial ecosystems, although their preservation as molecular fossils is relatively rare. Saccharides, such as arabitol, mannitol and trehalose, are important in biochemical processes, and are the dominant compounds in fungi, lichens and yeasts. Here we present gas chromatography–mass spectrometry (GC–MS) analysis of fungal saccharides in brown coal extracts and compare their distribution to extant white, brown, and soft-rot fungi. Distribution differs depending on the type of decay in modern and fossil wood-decomposing fungi. An arabitol/(arabitol + trehalose) ratio higher than 0.6 for extant and fossil fungi is diagnostic for soft and brown rot, while values below 0.4 are characteristic of white rot fungi. Values between 0.4 and 0.6 suggest a mixed origin of fungal saccharides. The observed differences may shed light on the type of fungal activity, in particular relatated to climatic conditions of the Cenozoic.We conclude that saccharides can be good indicators, sensitive to climate change, of wood degradation by fungi in thermally immature organic matter. As a case study, early Cenozoic lignites were formed on low latitudes in the tropics during or near the Paleocene/Eocene thermal maximum, as extant soft rot fungi can withstand extremes of temperature and humidity. The presence of these fungi is confirmed by the dominance of arabitol over trehalose in most of the Lower Cenozoic lignites and arabitol/(arabitol + trehalose) ratio values higher than 0.6. In contrast, Miocene detritic coals, which were formed in temperate to subtropical climates, contain saccharides derived from a mixture of different fungi with white rot predominance.

Study on the Stress Distribution and Stability Control of Surrounding Rock of Reserved Roadway with Hard Roof

According to field observation and theoretical analysis, the failure of the 1523103 reserved roadway is mainly affected by the lateral support pressure, rock mass strength, and support mode. With the mining of the 152309 working face, the lateral pressure of coal pillars on both sides of the reserved roadway increases, and since the lithology of the two sides and the floor of the roadway is weak, the reserved roadway experiences spalling and floor heave. Through numerical simulation, the distribution law of surrounding rock stress and the displacement of surrounding rock are obtained after the roof cutting and pressure relief of the reserved roadway with hard roof. According to the cause of surrounding rock failure of a reserved roadway, the combined control technology of roof cutting and pressure relief, grouting anchor cable support, and bolt support is put forward. After cutting the roof and releasing the pressure on the working face, the lateral support pressure of the two sides of the roadway is significantly reduced, the deformation of the two sides of the roadway is small, the maximum shrinkage rate of the section is reduced from 70% to 11%, and the deformation of the surrounding rock of the 1523103 reserved roadway is effectively controlled. The successful control of the surrounding rock in the 1523103 tunnel reduces the number of coal pillars to be installed, improves the coal extraction rate, and is conducive to the sustainable utilization of limited natural resources and the sustainable development of the coal industry.

Numerical investigation of the in situ gas explosion fracturing and the enhancement of the penetration in coal seam boreholes

AbstractPermeability enhancement of low permeability coal seams is a key tool in coal mine gas extraction and utilization. Numerical investigations are used to analyze the geometric parameters of the drilled gas cavity and the effect of initial pressure on explosion parameters to explore the potential of original gas blasting in enhancing crack penetration in coal seams. On the basis of these analyses, the changes in characteristic parameters of the coal body under blasting pressure are examined. The results show that the maximum explosion pressure tends to be close to the theoretical explosion maximum when the L/Φ is 1.67–2.5, and the mechanical effect of the explosion pressure and surge velocity on the wall reaches the optimum in the experimental group when the L/Φ is 1.67. The initial pressure and the maximum explosion pressure demonstrate a linear positive correlation, and increasing the former can effectively enhance the force applied to the hole wall. During the gas explosion pressurization stage, the cracking range of coal under pressure is 0.05 m, but the duration of peak pressure can extend the range of cracking. The combined effect of the stress and pressure fields causes elastic energy storage in the coal body to fail in the radial region of the hole wall, but regains elastic energy storage as the pressure increases. The effect of fracturing on the radial coal seam permeability of the borehole wall before and after the fracturing effect is expanded by 19.6 times, proving that in situ gas explosion in boreholes can effectively improve the gas seepage characteristics of coal seams and increase the gas recovery rate. The simulations indicate that the application of in situ gas explosion fracturing and permeation technology is limited by the increase in maximum explosion pressure and the cumulative effect time of the peak pressure. This provides a theoretical basis for understanding the constraints of gas explosion fracturing and permeation technology.

Thermal extraction of coal and derivatives to prepare hot-pressed coal briquette for COREX application

In this study, the thermal extraction of various coal and derivatives by N-methylpyrrolidone was systematically compared and the extract was used as binder to prepare hot-pressed coal briquettes (HPCBs). The results demonstrate the effectiveness of thermal extraction in converting coal to HyperCoal, and the conversion yields varied from 12 to 71%. While the extraction tends to have a linear relationship with hydrogen-carbon ratio of raw coals, this relationship was not directly observed for derivatives due to inherent changes occurring during production. Proximate analysis of the extract reveals a reduction in ash content to below 1% while an increase in volatile matter by more than 8%. XPS and FTIR spectra demonstrate the high efficiency of thermal extraction in extracting hydrocarbons, but poor for compounds such as alcohols, phenols, ethers, and carboxylic acids. The extracts, rich in hydrocarbons, exhibited excellent thermoplasticity, making them suitable binders for HPCBs preparation. Among the extracts, coal derivatives exhibited higher compressive strength compared to coals. Consequently, the extract derived from direct coal liquefaction residue with the highest compressive strength was selected for preparing HPCB. Furthermore, we investigated the application characteristics of the HPCB and identified its great potential for use in COREX melting-reduction ironmaking. The preparation of HPCB is vital for expanding the utilization of bituminous coals while reducing dependence on lump coal and coking coal resources.

Characteristics of overlying strata and mechanisms of arch beam failure in shallowly buried thick bedrock coal seams: A case study in western China

AbstractThe Yangjiacun coal mine, located in western China, exhibits distinctive characteristics, such as its shallow depth, thick bedrock, thin loose layer, and unique roof strata breaking movement. In this research, a comprehensive analysis of previous exploration data, subsequent mechanical testing, key stratum theory, natural equilibrium arch theory, and simulation tests and numerical simulations has been conducted to investigate the failure behavior of the overlying rock strata in the Yangjiacun Coal Mine. Specifically, the load‐bearing capacity of the key stratum structure in the bedrock and the morphological properties of the arch‐beam structure have been thoroughly examined. A mechanical model of the roof rock arch‐beam structure has been established, and an analytical formula for the limit size and stability criterion of the arch‐beam structure has been derived. The mining‐induced rock arch‐beam structure plays a crucial role in transferring the load of the upper strata to the surrounding goaf, thereby preventing subsidence and deformation of the overlying strata. However, the arch‐beam structure periodically experiences instability during the advancement of the working face, gradually progressing towards the upper layer until the main key stratum is breached and the arch‐beam structure collapses. Based on the characteristics of weathered rock and the arch‐beam failure model in the Yangjiacun Coal Mine, quantitative backfilling mining methods have been proposed to either compensate for the mining void created by coal extraction or limit the size of exposed key strata through strip mining, ensuring the stability of the R6 key stratum. This study represents a significant contribution to understanding the intricate failure behavior of overlying rock strata in coal mines and provides a valuable framework for the responsible and efficient extraction of coal resources in similar environments.

Experimental Study on the Effect of Freeze-Thaw Cycles on the Mechanical and Permeability Characteristics of Coal

The safe and efficient mining of coal seams with low porosity, low permeability, and high heterogeneity under complex geological conditions is a major challenge, with the permeability of coal seams playing a crucial role in coal mine gas extraction. The development of coal seam permeability enhancement technology can help coal mines produce safely and efficiently, while the extracted coal bed methane can be utilized as green energy. To study the effect of freezing and thawing on the evolution of the mechanical and permeability properties of coal, triaxial permeability tests were conducted on low-permeability coal under two different confining pressures. Simultaneously, dry, saturated, and freeze-thaw coal samples were set up for comparison, and the effects of water and freeze-thaw were isolated from each other. The triaxial mechanics and percolation laws of dry, saturated, and freeze-thaw coal rocks were obtained; the results show that saturated coal has the lowest initial permeability, while freeze-thawed coal has the highest initial permeability. Through analyzing the effects produced by water, freezing and thawing on coal specimens, the mechanism of the influence of freeze-thaw on the permeability evolution of coal was revealed. The research results can provide theoretical guidance for the development of gas extraction technology for low-permeability coal seams.

Investigation on the mechanism of solvothermal extraction of coals by macromolecular models

In this study, solvothermal extraction of two coals (Fangezhuang fat coal, FGZ; Sima lean coal, SM) were conducted by N-methylpyrrolidone (NMP); the molecular models of corresponding hypercoals (HPC) were firstly constructed besides that of coals to clarify the extractions mechanism, aiming to provide a technically feasible route to investigate the mechanism of other extraction processes. The structural parameters were obtained by means of proximate analysis, ultimate analysis, carbon-13 nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy and Fourier Transform infrared spectroscopy. The results showed that aromatic ring types of both raw coals were mainly naphthalene and anthracene, nitrogen atoms existed in pyrrole and pyridine whilst sulfur atoms in thiophene substantially, aliphatic carbons presented in the form of methyl and methylene groups while oxygen-containing functional groups mainly consisted of phenolic hydroxyl, carbonyl, carboxyl and a few ether bonds. Thus, the macromolecular structure models were constructed, with simulated molecular formulas were C168H136N2O12S, C135H74N2O12S, C166H136N2O6S and C128H82N2O11, respectively. After modifying the macromolecular models by Materials Studio for geometric optimization, annealing dynamics calculation, density simulation and analysis of chemical bonds, these four models reflected the macromolecular structural characteristics precisely. On the other hand, both models of raw coals changed significantly in functional groups, branched chain length and quantity pre and post thermal extraction, indicated that the thermal extraction process was mainly affected by swelling behavior and pyrolysis. This study provided new theoretical support in the development of coal extraction technology and understanding of HPC on the macromolecular level by a model basis.

Efektivitas kombinasi Pistia stratiotes L. dan Salvinia molesta Mitchell dalam fitoremediasi air asam tambang batubara

Open pit mining is a mining system that is commonly applied to coal extraction activities. Environmental problems in coal mining activities are generally related to acid mine drainage (AMD). Efforts to overcome the impact of AMD can be done by phytoremediation in constructed wetlands (CW). Plants that have the potential for AMD phytoremediation include Pistia stratiotes L (water lettuce) and Salvinia molesta Mitchell (giant Salvinia) , so it is necessary to conduct research on the effectiveness of the combination of P. stratiotes and S. molesta to be developed on CW vegetation. The experimental design used was a completely randomized design (CRD), with 3 treatments using P. Stratiotes, S. Molesta, Combination of P. stratiotes and S. molesta each 9 replications. The results showed the effectiveness of phytoremediation using plant vegetation of P. stratiotes and S. molesta in increasing pH by 40.04% and reducing sulfate levels by 41.72%. The effectiveness of the combination of P. stratiotes and S. molesta in reducing levels of Mn and Fe were 101.36% and 93.49%, respectively. The decrease in TSS levels is better done by the combination of P. stratiotes and S. Molesta vegetation compared to P. stratiotes or S. Molesta vegetation alone, but the better growth rate occurred in S. molesta vegetation only.

Changing Law of Permeability of Coal Reservoirs under Variable Pressure Conditions and Its Influence on Extraction Efficiency of Coalbed Methane

Coal permeability data are critical in the prevention and control of coal and gas outbursts in mines and are an important reservoir parameter for the development of coalbed methane. The mechanism by which permeability is affected by gas pressure is complex. We used a self-developed true triaxial seepage experimental device that collects lignite and anthracite coal samples, sets fixed axial pressure and confining pressure, and changes gas pressure by changing the orientation of the coal seam to study the influence of the gas pressure on the permeability of the coal seam under the conditions of different coal types and different bedding orientations. Coal permeability decreased rapidly and then decreased slowly and tended to be stable with the increase in gas pressure. This conformed to the power exponential fitting relationship, and the fitting degree reached more than 99%. The comparison of the two anthracite coal samples showed that the sample’s permeability with a bedding plane vertical to the seepage direction was significantly lower than that of the bedding plane parallel to the seepage direction, indicating that gas seeped more easily along the bedding. The sensitivity coefficient of permeability with the change in gas pressure was calculated. The analysis showed that coal permeability was sensitive to changes in gas pressure during the low-pressure stage. When the gas pressure was greater than 0.8 MPa, the sensitivity coefficient was significantly reduced, which may have been related to the slow increase in the amount of gas absorbed by the coal seam in the high-pressure stage. A theoretical calculation model of coal seam permeability considering adsorption/desorption and seepage effects was proposed and then verified with experimental results showing that the theoretical model better reflected the permeability characteristics of coal and predicted its permeability. Using the finite element simulation software COMSOL, the extraction efficiency of the coal seam gas under different gas pressure conditions was simulated. The results showed that coal permeability and extraction efficiency decreased with an increase in gas pressure. In the low-pressure stage, the reduction in the extraction efficiency was more evident than that in the high-pressure stage.

An Overview of Soil Pollution and Remediation Strategies in Coal Mining Regions

Coal remains a very important source of energy for the global economy. Surface and underground coal mining are the two major methods of coal extraction, and both have benefits and drawbacks. Surface coal mining can have a variety of environmental impacts including ecosystem losses, landscape alteration, soil destruction, and changes to surface and groundwater quality and quantity. In addition, toxic compounds such as heavy metals, radioactive elements, polycyclic aromatic hydrocarbons (PAHs), and other organic contaminants are released in the environment, ultimately affecting the health of ecosystems and the general population. Underground mining has large impacts on underground water supplies and water quality, but generally has less visual surface impacts such as leaving waste and tailings on the surface and subsidence problems. In response to the concern about these environmental issues, many strategies have been developed by scientists and practitioners to minimize land degradation and soil pollution due to mining. Reclamation laws passed in numerous countries during the past 50 years have instituted practices to reduce the impacts of soil pollution including burying toxic materials, saving and replacing topsoil, and vegetating the land surface. While modern mining practices have decreased the environmental impacts, many sites are inadequately reclaimed and present long-lasting soil pollution problems. The current review summarizes progress in comprehending (1) coal mining impacts on soil pollution, (2) the potential risks of soil pollution associated with coal mining, and (3) different types of strategies for remediating these contaminated soils. Research and prospective directions of soil pollution in coal mining regions include refinements in assessing pollutant levels, the use of biochars and other amendments, phytoremediation of contaminated soils, and the release of toxic elements such as mercury and thallium.

Abandoned mine land program: Examining public participation in decision‐making

AbstractFor centuries, coal extraction and production provided low‐cost energy that powered the American economy. Currently, an estimated 5.5 million people in the Appalachian region live within one mile of an Abandoned Mine Land (AML) site. The site remediation has been funded and promoted by the AML program under the Surface Mining Control and Reclamation Act (SMCRA) of 1977, and public engagement has been required. However, little is known about the AML program and the public engagement requirement for site remediation decision‐making. Relying on State and Tribal Reclamation Plans and community surveys, we investigate how AML states and tribes engage the public and which barriers limit successful participation in the AML program. We found that AML states and tribes rely heavily on traditional methods of public engagement, such as public meetings, hearings, and comment periods, rather than nontraditional methods that could include more diverse stakeholders. We also found (1) lack of information on public participation opportunities and (2) unclear project selection and awards processes as key barriers limiting public engagement. Three recommendations specific to AML program are suggested.

Effect of extracts of petroleum ether, dichloromethane and methanol on thiophenic sulfur release during coal pyrolysis

The existing forms and thermal transformation of sulfur in high sulfur coal directly influence the efficiency of coal clean utilization by the staged pyrolysis conversion. Low molecular compounds distributed in coal are very different from the macromolecular structure of coal and play an important role during coal pyrolysis. In order to investigate the effects of low molecular compounds on the release of typical thiophenic sulfur species during coal pyrolysis by Py-GC/MS, petroleum ether, dichloromethane, and methanol were used for sequential ultrasonic extraction of Linfen coal (LFC). The compositions of extracts were detected by GC×GC/MS. Results show that three primary kinds of thiophenic sulfur species (2-methyl thiophene, benzothiophene, and dibenzothiophene) were released during coal pyrolysis and they are mainly derived from the cracking of macromolecular skeleton containing thiophenic sulfur in coal. The amounts of thiophenic sulfur released during raw coal and residues pyrolysis both increase with temperature. Besides, extracts with different compositions have different effects on the release of thiophenic sulfur during pyrolysis. In detail, the cyclization of aliphatic compounds could provide active hydrogen. On the one hand, the active hydrogen promotes the break of bridge bonds around thiophenic sulfur. On the other hand, active hydrogen may attack sulfur atoms of thiophenic sulfur, reducing the energy barriers of thiophenic sulfur decomposition. Aromatic compounds polymerize with sulfur-containing groups converting to benzothiophene and dibenzothiophene with larger molecular weight. In addition, thiophenic sulfur may be oxidized by esters to sulfones or sulfoxides, which further decompose, resulting in the inhibition effect on thiophenic sulfur formation during coal pyrolysis.

Experimental Study of Influencing Factors on Mechanical Properties for New Coal-Like Materials

Physical similarity simulation is one of the best methods for improving coal bed methane extraction efficiency, and the development of reasonable materials is important for improving physical similarity simulation testing results. This study aimed to investigate the mechanical properties of coal-like materials in a solid–gas coupled physical simulation test experiment. A new type of material with sand as aggregate, cement gypsum as cement, and silica gel as adsorbent was developed by an orthogonal design method. ANOVA and theoretical analysis were used to investigate the sensitivity and effects of different content ratios on the volumetric weight, uniaxial compressive strength, and elastic modulus of coal-like materials. The results of the investigation showed that the order of volumetric weight sensitivity ranging from large to small was the contents of silica gel, gypsum, and cement. The order of the sensitivity of uniaxial compressive strength and elastic modulus ranging from large to small was the ratio of the contents of silica gel, cement, and gypsum. Furthermore, the volumetric weight, uniaxial compressive strength, and elastic modulus of coal-like materials increased linearly and exponentially with the increase of cement and gypsum contents, respectively, whereas they decreased exponentially with the increase of silica content. Based on the results and analysis, a comprehensive model for the characteristic parameters of coal-like materials was established, and the prediction error was controllable to within 25%.

Imaging ‘Slow Violence’ in the Jharia Coalfields of India: Disrupting Energy Modernity through Photography

The paper contributes to the field of Energy Humanities from an often under-discussed Global South perspective, foregrounding cultural productions around coal extraction as a potential tool for disrupting energy modernity. Using photographs from the Jharia coalfields in Jharkhand, India, as primary sources, we examine coal extraction as a form of ‘slow violence’. The discursive ploy of energy modernity has been to make fossil fuels an emblem of socio-economic progress. The paper adds to critiques seeking to reframe this narrative and argues that the framework of slow violence reconfigures coal mining as a form of eco-social dispossession. The paper traces how the photography of Sebastian Sardi and Ronny Sen give visibility to those spaces—both somatic and geographical—which are not considered a legitimate part of the country’s development rhetoric but are nonetheless necessary for its creation and maintenance.

Research on Directional Hydraulic Coal Cutting and Outburst Prevention Technology in Soft and Hard Composite Coal Seams.

Affected by tectonics, soft and hard composite coal seams are widely distributed in China; the soft stratification in the soft and hard composite coal seam is the key to controlling the occurrence of coal and gas outburst accidents. Based on this, for soft and hard composite coal seams, in order to accurately extract soft layers, a directional hydraulic coal mining equipment has been developed, including a drilling rig pump truck system, a directional coal wireless measurement system, and a cutter drill pipe system. By constructing a mathematical model and conducting numerical simulations, it was found that the vertical stress, horizontal stress, and gas pressure of the coal body around the borehole after coal extraction decreased significantly compared to normal borehole conditions; the on-site test results indicate that the hydraulic coal extraction volume of directional hydraulic coal extraction boreholes reaches 0.25 m3 per meter. The total amount of coal extracted accounts for more than 3‰ of the total amount of coal within the coverage area. The average concentration of gas extraction in the coal extraction area is 80.15%, and the net amount of gas extraction from 100 m boreholes reaches 0.17 m3/(min·hm). After extraction, the measured residual gas content in the coal extraction and non-extraction areas decreased by 59.27 and 40.38%, respectively. Directional hydraulic coal mining technology can effectively solve the problem of coal and gas outburst prevention in soft and hard composite coal seams and has good application prospects.

Land Use Optimization and Carbon Storage Estimation in the Yellow River Basin, China

Urban development and coal extraction have caused conflicts regarding production, living, and ecological lands in the Yellow River basin. Here, a coupled genetic algorithm–patch generating land use simulation InVEST model was constructed to optimize land use/land cover (LULC) and simulate carbon storage changes. This study shows that the LULC changed dramatically from 2010 to 2020 in an area that accounts for 31.96% of the area of the Yellow River basin. Inappropriate land use conversion and encroachment have reduced carbon storage by 2.92 × 106 t, destroying the stability of the ecosystem. The development of cities has encroached on cultivated land, which may have affected the region’s food security. Following LULC optimization, ecological and cultivated lands are gradually being restored, and the transition between the different lands tends to be orderly, resulting in an increase of 24.84 × 106 t in carbon storage. The relationship between LULC and carbon storage shows that the high carbon intensity of woodland, grassland, and cultivated land is crucial to ensuring regional carbon balance. For the Yellow River basin, necessary environmental protection measures are the key to achieving high-quality economic development. This study can provide guidance for decision-makers in formulating ecosystem restoration plans.

A life cycle assessment of coal-fired thermal power plants with post-combustion control techniques: an India scenario.

In recent years, there has been a focus on clean power generation, and it is critical to assess the environmental impact of novel technologies used in pollution control in power generation. The study uses life cycle assessment (LCA) to assess the environmental impacts of coal-fired thermal power plants with different emission control techniques in an Indian scenario. As there are no such studies available in the Indian context, this work might provide a holistic view of the impacts of energy generation. A supercritical coal-fired plant with a capacity of 660 MW is considered in this study. The system boundary included coal extraction, transportation, power plant operation, and transmission losses of electricity with a functional unit of 1 kWh. It was observed that there was an energy penalty due to the power consumed in emission control devices, but the maximum energy penalty was due to the power used in the carbon capture system. The LCA is done from "cradle to gate", with impact indicators at the mid-point evaluated using the RECIPE (H) 2016 LCIA method. LCA results showed that power plant operation is the most significant contributor to environmental impact. Initially, in cases 1 and 2, climate change (CC) potential was a major impact category, but CC potential was reduced with carbon capture and storage, 0.27 kg CO2 eq. in case 3 with ESP, FGD, SCR, and carbon capture and storage (CCS) and 0.263 kg CO2 eq. in case 4 with ESP and CCS. But there was a considerable increase in the majority of the impact categories in case 4. Freshwater consumption potential increased from 3.98 E-03 m3 in base case 1 to 4.98 E-03 m3 in case 3 due to the amount of water used in chemical production during CCS, as CC potential is a major concern in power generation, However, compared to case 1, the potential for climate change increased in case 2, whilst in case 4, the potential for climate change is lower but has resulted in an increase in the majority of impact categories. Case 3 shows an optimal approach to reducing CO2 emissions compared to other cases. The combination of ESP, FGD, SCR, and CCS is favourable for cleaner energy generation.