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Abstract Comprehensive information about the concentrations, distribution, and modes of occurrence of elements in coal are important from the environmental and economic point of view. Although a great number of previous studies have investigated the geology of coalbed methane in the Qinshui Basin, only a few studies focused on the inorganic constituents in coal. More specifically, the mode of occurrences of valuable element Li in the No. 3 Coal is still unclear, although Li was found enriched. In this study, we present mineral characteristics, as well as multi-element data on the Permian No. 3 Coal from the Sucun and Gaohe Mines, Changzhi City, southern Qinshui Basin. The studied coals are characterized by low- to medium-ash yield (Ad = 5.72%- 28.18%, 12.34% on average), low volatile matter yield (Vdaf = 8.49–15.17%, 10.96% on average), suggesting a low volatile bituminous coal to semi-anthracite. NH4-illite and kaolinite are the main minerals in the coals detected by XRD, and trace amount of minerals calcite, dolomite, quartz, pyrite and diaspore can also be found. The major elements of the studied No. 3 coals are dominated by SiO2 and Al2O3, ranging 2.49–16.45 wt% and 2.13–12.9 wt% (on a whole-coal basis), respectively. Li is enriched in the No. 3 coals (5

Abstract In this study, we investigate coal matrix swelling during the process of gas diffusion from cleats and its impact on the evolution of strain. We inject helium into both jacketed and unjacketed coal samples within a pressurized core holder. In the unjacketed experiment, the coal sample was exposed to hydrostatic gas pressure. In the jacketed experiment, the coal sample was constrained by fixed displacement at the two ends and by constant confining pressure laterally. In both experiments, strains were measured continuously both parallel/perpendicular to the bedding plane of the coal as internal pressure of helium is increased. For the unjacketed test the initial rapid compactive deformation of the sample rebounds to dilative at long term — attributed to the gas diffusion-induced swelling of the coal matrix. For the jacketed test both axial and circumferential coal strains are first dilative due to the decrease in effective stress with subsequent changes of coal strain induced by the gas diffusion closely associated with the specific boundary conditions. For a constant stress boundary, the circumferential strain first remains unchanged for some time and then gradually increases to steady state. Such a phenomenon suggests that when gas diffuses from the cleat to the matrix, the coal matrix-cleat system probably undergoes a transition from local swelling to macroswelling. In contrast, for a fixed displacement boundary, the axial strain first decreases and then reaches a steady state. It also indicates that the swelling of the matrix not only decreases the aperture of the fracture, but also expands the circumferential profile of the coal sample due to the Poisson effect. In addition, helium diffusion in the matrix is estimated by using the bidisperse diffusion model. The calculated effective diffusivity increases with pore pressure. This suggested that the gas diffusion coefficient is a pore pressure-dependent parameter. These results demonstrate that gas diffusion from the cleat to the matrix can cause the swelling of the coal matrix, change the aperture of the cleat, and in turn impact the evolution of the coal permeability.

Abstract A “permeability equilibration time” is typically assumed in interpreting permeability measurements – indicating that equilibration has been reached and both sorption-induced changes in deformation and their impact on permeability evolution have ceased. However, for extremely low matrix permeability (tight) dual porosity rocks, this “permeability equilibration time” may easily exceed the time interval between two consecutive permeability measurements – invalidating the interpretation of a steady permeability if the non-steady state conditions are not correctly accommodated. This is especially important where pressure diffusion from fracture to matrix results in a non-monotonic and non-asymptotic approach to a steady permeability, but instead contains multiple stages, plateaus and permeability reversals. We validated this hypothesis through experiments and analysis. Experiments measured the non-monotonic and scale-dependent deformations of fracture and matrix and linked these directly to the dynamic evolution of reservoir permeability. These laboratory strain measurements were integrated with numerical analyses to explore how mass and stresses transferred between matrix and fracture and were coupled under conditions of constant confining pressure. Strain gauges were distributed to directly measure stress transfer between matrix and fracture and interrogated deformation at different scales and at different proximities to control fractures. The prismatic sample of coal was tested under freely expanding boundary conditions. Optical microscopy and X-ray CT imaging were used to define the fracture distribution throughout the sample with mercury intrusion (capillary) porosimetry (MICP) constraining the pore size distribution and enabling independent estimation of matrix permeability. A numerical model was built and verified by matching measured strains and then applying this to model the evolution coal permeability from initial to ultimate equilibrium. Both the experimental and numerical results show that the final equilibrium state (pressure, stress and mass contents) for the matrix system extends to months rather than hours and suggests that some current permeability data may therefore reflect a non-equilibrium permeability state. Results also show that during this non-equilibrium condition, the swelling of the matrix near the fracture will cause not only compaction and narrowing of the fracture, but also shrinkage of the matrix that is distant from the fracture under constant confining pressure condition. Both experimental and numerical results demonstrate that the evolution of non-equilibrium strain/permeability is determined by the matrix-fracture interactions, including sorption-induced swelling/shrinking, through transient stresses in matrix and fractures. And that these non-equilibrium stress transfers determine the dynamic permeability evolution during gas extraction (e.g., CH4) or injection (e.g., CO2) at reservoir scale for tight dual porosity rocks (e.g., coal and shale).

Abstract Unconventional natural gas, including coalbed methane and shale gas, has become important natural gas resources. Coal and shale reservoirs are characterised by low porosity and low permeability and difficult for gas production. These reservoirs are also considered as fractured reservoirs, i.e. the natural fracture/cleat system in coals and bedding direction microfractures in shales. Permeabilities of these reservoirs are sensitive to stress change. During gas production, the pressure drawdown significantly increases effective stress, and thus decreases the absolute permeability. The relationship between permeability and stress is characterised by fracture compressibility, which is difficult and costly to be obtained from the field, but can be acquired easily from laboratory measurement. In this review article, the laboratory methods to obtain fracture compressibility were reviewed. Literature data on fracture compressibility for coals and shales were collated and the relationships between fracture compressibility and pressure, stress and rock properties were discussed. It is found that fracture compressibility is higher for coals than for shales, and the fracture compressibility for proppant supported fracture is even lower than that for the same shale or coal. Moreover, fracture compressibility is variable depending on gas type, gas pressure, and stress. Fracture compressibility has no correlation with absolute permeability in general, but has a weak positive correlation for the same sample.

AbstractAnchoring groups are extremely important in controlling the performance of dye‐sensitized solar cells (DSCs). The design and characterization of sensitizers with new anchoring groups, in particular non‐carboxylic acid groups, has become a recent focus of DSC research. Herein, new donorπacceptor zincporphyrin dyes with a pyridine ring as an anchoring group have been designed and synthesized for applications in DSCs. Photophysical and electrochemical investigations demonstrated that the pyridine ring worked effectively as an anchoring group for the porphyrin sensitizers. DSCs that were based on these new porphyrins showed an overall power‐conversion efficiency of about 4.0 % under full sunlight (AM 1.5G, 100 mW cm−2).

Enrichment of waterways with nitrogen (N) and phosphorus (P) has accelerated eutrophication and promoted cyanobacterial blooms worldwide. An understanding of whether cyanobacteria maintain their dominance under accelerated eutrophication will help predict trends and provide rational control measures. A mesocosm experiment was conducted under natural light and temperature conditions in Lake Taihu, China. It revealed that only N added to lake water promoted growth of colonial and filamentous cyanobacteria (Microcystis, Pseudoanabaena and Planktothrix) and single-cell green algae (Cosmarium, Chlorella, and Scenedesmus). Adding P alone promoted neither cyanobacteria nor green algae significantly. N plus P additions promoted cyanobacteria and green algae growth greatly. The higher growth rates of green algae vs. cyanobacteria in N plus P additions resulted in the biomass of green algae exceeding that of cyanobacteria. This indicates that further enrichment with N plus P in eutrophic water will enhance green algae over cyanobacterial dominance. However, it does not mean that eutrophication problems will cease. On the contrary, the risk will increase due to increasing total phytoplankton biomass.

Abstract Food waste has become an issue of great public concern because of its environmental impacts and strategic significance of food security worldwide. In the context of ecological civilization construction and circular economy development in China food waste recycling faces critical theoretical and practice obstacles in reality. As China's urban population grows and the restaurant industry expands, the food waste generated by restaurants increases. Therefore restaurant owners’ attitude and behavior towards food waste recycling plays a pivotal role. As a stakeholder, the awareness of restaurant owners affects their attitudes and behavior towards the environment. In this paper, 1,050 restaurant owners from six cities of Gansu province in northwestern China were surveyed to study their awareness of food waste recycling. Using the awareness assessment model, the awareness level of 1,050 restaurant owners were calculated. The results show that 37.33% of respondents has a high awareness and 62.67% of them has a low awareness of food waste recycling. This indicates that the restaurant owners have a low level of overall awareness. Logistic regression model was used to examine factors that affect the awareness level of restaurant owners. Compared with the male restaurant owner, the female one has a lower awareness. The younger restaurant owner has a higher awareness than the older one. In addition, factors, including the educational level of restaurant owner, restaurant scale, amount of daily restaurant food waste, the way of food waste treatment, and the macroeconomic development of city where restaurants located, have positive effects on the awareness.

Abstract The alternative energy plays a crucial role in the sustainable energy development. The alternative energy related literature had attracted a growing attention with the research outputs expanding substantially. Based on the Science Citation Index-Expanded (SCI-E) and the Social Sciences Citation Index (SSCI), a bibliometric analysis of the research output was carried out to depict existing research activities on alternative energy and future directions. The article was the main type of publications with the English as the dominate language to explain their results. With the publications increasing rapidly since 2008, the researches mostly focused on the fields of Energy & Fuels and Environmental Sciences. Energy Policy was the journal that published the largest number of research articles on the alternative energy. The bioenergy and solar energy were popular items in the commonly used 20 journals. Among the countries, the USA was leading on alternative energy related research, publishing the largest number of articles (TP=2368) and being the most influent ( h -index=90). The USA played a key role in the academic collaborations with China, UK, Canada, Germany, Italy, South Korea and Spain. The National Renewable Energy Lab (the USA) contributed most in the alternative energy field and more specially, the School of Electrical & Computer Engineering (TP=36) was the most productive subordinate in the National Technology University of Athens. It was interesting to note that more attention was paid to solar or wind energy during the first 5 or 10 years, then turned to bioenergy subsequently except for Spain, Canada and Australia. In addition, bioenergy received the most attention in the 7 types of alternative energy. The forest/wood biomass, energy crops and switchgrass were the main bioenergy resources and fermentation was the commonly used conversion technology. The production of biogas, biodiesel and bioethanol was most popular in the bioenergy related studies. Wind energy and solar energy related researches were mainly on the energy utilization approaches such as the wind generation, wind farm, photovoltaic and solar thermal. The conversion devices such as the wind turbine and solar cell were paid most attention in order to improve the production efficiency. The most cited article, published in Desalination in 2009 with 1562 citations until 2013, was about wind power utilization in the reverse osmosis desalination plant.