Recovery Rate Of Resources Research Articles

Study on pyrolysis process and mechanism of organic coating of waste polyesterimide enameled wire based on density functional theory

The pyrolysis treatment of waste polyesterimide enameled wire offers significant advantages such as continuous processing, non-hazardous nature, and high resource recovery rate. However, research on its pyrolysis process and mechanism remains insufficiently explored. In this study, techniques including thermogravimetry (TG), Fourier transform infrared spectroscopy(FT-IR), pyrolysis–gas chromatography-mass spectrometry(Py-GC/MS) were employed to investigate pyrolysis temperature, weight loss rate, pyrolysis and kinetic parameters, composition and distribution of pyrolysis products, and changes in functional groups under different temperatures and heating rates. The pyrolysis of polyesterimide enameled wire can be divided into three stages: volatilization of specific components (314.8 °C,1.6 %), rapid decomposition of polyesterimide (435.2 °C, 44.7 %), and generation of small organic molecules with the fixation of pyrolytic carbon (750 °C, 9.0 %). The main components of the pyrolysis gas products include aromatic compounds, ethers, aromatics, ketones, and carbon dioxide. At 400 °C, a substantial amount of pyrolysis gas products and free radicals are produced, with an increase in aromatic hydrocarbons. The carbon distribution in the pyrolysis products mainly focuses on C6-C10 and C11-C15, and many organic compounds such as benzoic acid, phenol, and aniline are generated. Based on density functional theory, the bond dissociation energies in the polyesterimide were calculated. This clarified the possible thermal decomposition pathways of the polyesterimide and provided the energy barrier values, elucidating the generation mechanism of pyrolysis products during thermal decomposition. The copper atom in specific location reduces the negative ESP of O and increases the positive ESP of H in EPI, which makes H more likely to attach to O. The presence of Cu increases the ESP range and promote the pyrolysis process. This study provides a theoretical basis for the high-value recycling of waste polyesterimide enamelled wire.

Deformation mechanism and control technology of gob-side entry retaining with roadside backfilling: a numerical analysis and field investigation

The technology of gob-side entry retaining (GER) has the advantages in terms of higher resource recovery rate and lower drivage ratio. In this study, the GER implementation in N1217 panel in Ningtiaota Coal Mine, to verify the adaptability of the gob-side entry retaining with roadside backfilling, the FLAC3D numerical model was established, the stress evolution law and plastic zone distribution of the roadway surrounding rock were analyzed, the deformation characteristics of the roadway during the mining period were revealed, the roadway surrounding rock control technology was proposed, and the development of roof cracks was analyzed. The numerical results show that during the mining of the working face, the roadside backfill body and gangue are jointly loaded, the peak stress of the surrounding rock is transferred from the mining side to the solid coal side, the plastic zone of the roof and the solid coal side increases significantly, and the tensile and shear mixed failure occurs. Based on the evolution characteristics of the stress and plastic zone of the surrounding rock during the mining period of the working face, a collaborative control technology of the surrounding rock based on gangue retaining bracket + roadside backfill + bolt (cable) is proposed, and the borehole peep shows that the roadway is affected by roof fracture rotation and subsidence, which leads to the development of roadway overburden cracks and failures to the depth. The monitoring results indicate that the control measures are highly effective, with minimal roadway convergence observed and stable bolt (cable) supporting forces recorded. Additionally, hydraulic support resistance monitoring confirms that the roadway remains stable. It can ensure the safe mining of the working face of the Ningtiaota coal mine and other similar roadways.

Energy dissipation damage constitutive relation of CFRP passively confined coal sample

In view of the stability problem of coal pillars left over during coal resource mining, (Carbon Fiber Reinforced Polymer) CFRP sheet is applied in coal pillar reinforcement. Uniaxial compression tests of CFRP passively confined coal samples are carried out to explore the mechanical response mechanism of passively confined coal samples under different layers, and the energy dissipation damage constitutive relationship of CFRP passively confined coal samples is established based on the energy dissipation principle. The conclusions are: As CFRP layers increased, the local damage of coal samples before the peak evolved from a 'cliff-like jagged' to a 'capillary jagged', with post-peak instability marked by a shift to more 'cliff-like' characteristics. The tests revealed improvements in peak strength and elastic modulus, with a defined functional relationship between these properties and CFRP layers. The energy storage capacity of passively confined coal samples improved with CFRP layers, requiring less axial deformation to achieve equivalent energy levels. The energy dissipation rate showed an initial decrease followed by an increase, with a minimum inflection point, the elastic energy consumption ratio tends to decrease slowly and then rapidly during post-peak instability. A damage constitutive relationship and evolution equation were developed, highlighting that the CFRP sheet significantly inhibits damage, with diminishing effectiveness beyond two layers. The study concludes that three-layer CFRP sheets provide optimal confinement, offering a novel strategy for the reinforcement of coal pillars and the prevention and control of rock burst, without considering the actual coal pillar dimensions and shape. To sum up, the use of CFRP sheet to strengthen coal pillar has considerable potential research value in strengthening coal pillar and improving the recovery rate of coal resources.

The way out for urban household solid waste classification in China: From the perspective of multi-agent based behavior simulation

Rapid industrialization and urbanization drive China's massive urban household solid waste (HSW) generation. Classification and resource recycling of HSW is an effective way to address the “garbage-sieged city” dilemma and promote “urban mineral resources” exploitation. Despite efforts since 2000, HSW sorting and recycling remain at 30%. This study develops a multi-agent based behavior simulation model for HSW classification and recycling, incorporating the interactions and decision-making of key agents, including residents, enterprises, and the government. Taking Suzhou, China as a case study, field surveys were conducted, and behavioral decision-making functions were constructed to simulate micro-behavioral responses and macro-system evolution under different policy incentives, and to predict the implementation effect of domestic waste management approaches, provides the basis for decision-making. The results demonstrate that a combination of waste metering charges, recycling subsidies, and enhanced education program can effectively regulate agent behavior and optimize the system. One year after the implementation of the simulation, the number of “unclassification” residents has dropped from 1.85 million to 250,000 decreased by 86%; the number of “classification deposition” residents has declined from 1.28 million to 1.08 million, reduced by 16%; the number of “selling after classification” residents has risen from 1.05 million to 2.81 million, increased by 63%; the daily waste output per capita has decreased from 1.21 kg to 1.04 kg, reduced by 14%; the recovery rate of resources has been raised from 33.4% to 66.5%. The implementation effects of other policy scenarios are ranked as follows: the metering charge > the recycling subsides > the enhanced education program. The findings provide a basis for decision-making in HSW management. Concerning the metering charge and the recycling subsidies, they can benefit positive interactions encouraged by such economic stimulus. At the same time, it is suggested to strengthen classification and recycling infrastructure, and push forward the integration of HSW classification recycling.

Failure Characteristics and Cooperative Control Strategies for Gob-Side Entry Driving near an Advancing Working Face: A Case Study

Gob-side entry driving near an advancing working face can improve the recovery rate of coal resources and keep the balance between mining and development. However, the large displacement of the gob-side entry caused by the mining dynamics of abutment pressure challenges the safety and processes of coal mining. This article takes the 15102 tailentry of Xizhang Coal Mine in Changzhi City, Shanxi Province, as an example to study the stability of the coal pillar and the failure characteristics of the surrounding rock and proposes cooperative control strategies of surrounding rock stability. Field tests indicated that when the coal pillar width was 15 m, the displacements of the entry floor, roof, coal pillar side, and solid coal side were 1121 mm, 601 mm, 783 mm, and 237 mm, respectively. A meticulously validated numerical model, incorporating a double-yield model for the gob materials and calibrated parameters, was developed to investigate the stress changes and yield zone distribution across the coal pillar with different sizes. The results of the simulation indicate that the influence range of the dynamic abutment pressure caused by mining in the upper section of gob-side entry driving is 30 m ahead and 70 m behind. When the coal pillar width increases from 7 m to 20 m, the internal stress of the coal pillar increases continuously, while the internal stress of the solid coal decreases continuously. It is estimated that the reasonable coal pillar width should be 7 m, which is subjected to a lower load. The cooperative control strategies comprising a narrow coal pillar, hydraulic fracturing roof cutting for pressure relief, and entry dynamic support were proposed and applied in the 15103 tailentry. The final displacements of the floor, roof, coal pillar side, and solid coal side were 66.01%, 62.06%, 61.05%, and 63.30% lower than that of the 15102 tailentry in the same period, respectively, which effectively controlled the stability of surrounding rock. In addition, this finding for the gob-side entry driving near an advancing working face in this study can potentially be applied to other similar projects.

An Arsenic Removal Technology and Its Application in Arsenic-Containing Copper

The usage of copper (Cu) ores containing low or no arsenic (As) has reduced, and Cu ores containing high levels of As have emerged as vital mineral resources for Cu extraction and processing. The quality of the Cu ores has decreased from 1.6% to approximately 1.0%. The proportion of As to Cu in 15% of Cu resources currently reaches 1:5. However, during the extraction and processing of Cu ores, As presents significant environmental harm. Hence, safely and effectively removing As is paramount in Cu smelting and processing, holding substantial importance in fostering environmentally sustainable practices within the Cu extraction and processing industry. This article consolidates the resource distribution of As-containing Cu (ACC) ores, comprehensively and systematically evaluates the present advancements in extracting techniques for these minerals, and identifies the challenges inherent in pyrometallurgical and wet processes for treating ACC deposits. Pyrometallurgy is a simple primary roasting technique and has widespread applicability in the treatment of various ACC minerals. Its disadvantages are the emission of exhaust gas and the high treatment costs associated with it. The wet arsenic removal method boasts advantages including minimal air pollution and a high resource recovery rate, significantly aiding in Cu concentrate recovery; its major drawback is the production of As-containing wastewater. The hydrometallurgical removal of As from ACC mines involves extracting As through leaching. Recently, biometallurgy has presented innovative solutions using specialized microorganisms to bioleach or bioabsorb As, but large-scale industrial applications still lack specific practical implementation. This review explores the underlying causes of the challenges encountered in processing ACC minerals. Additionally, it highlights pyrometallurgical roasting coupled with high-temperature filtration as a pivotal advancement in the extraction and processing of ACC ores.

Optimization design method of 2D + 3D slope shape for landslide prevention in open-pit coal mine

In order to improve the stability of the slope and prevent the occurrence of landslide disasters, taking the east slope of the first mining area of Zhundong Open-pit Coal Mine as the engineering background, a combination of the 2-Dimensional (2D) limit equilibrium method and 3-Dimensional (3D) numerical simulation is used to optimize the shape of the east slope. By selecting a typical calculation profile based on the Bishop method and the residual thrust method in the 2D rigid body limit equilibrium method, the stability analysis of the profile slope is carried out, and the slope shape of the profile position meeting the requirements of the safety reserve coefficient and stripping ratio is preliminarily designed. Based on the 3D finite element strength reduction method, aiming at the slope shape that does not meet the requirements of safety reserve coefficient and stripping ratio, the width of the transport plate is reasonably changed, and a 3D numerical simulation model of various schemes is established. The influence of different tracking distances and slope angles on slope stability is studied. The 3D stability of the slope under different spatial forms is calculated, and the optimal tracking distance and optimal slope angle are determined. The slope stability and stripping ratio are further optimized. The results show that when the width of the transport plate of the DBS3 section slope is 8 ​m, it does not meet the requirements of safety reserve coefficient 1.2. When the width of the transport plate is set to 24 ​m, it meets the requirements of a safety reserve coefficient of 1.2 and an economic stripping ratio of not more than 8.0 ​m3/t. The 3D numerical simulation results show that the optimal tracking distance on the east side is 50 ​m, and the optimal slope angle is 35°. After the optimization design of a 2D and 3D slope shape, 2.456 million tons of coal resources were mined, creating a profit of about 21.1268 million yuan. While preventing landslide disasters, the recovery rate of coal resources was further improved.

Research on overburden structural characteristics and support adaptability in cooperative mining of sectional coal pillar and bottom coal seam

In the mining process of the II1 coal seam at Zhaogu No. 2 coal mine, a method of stratified mining is employed, leaving relatively wide coal pillars in sections. To enhance the resource recovery rate, the mine carries out the cooperative mining of the sectional coal pillars and the lower layer coal seam. The 14,022 cooperative working face of fully-mechanized and fully-mechanized top-coal caving at Zhaogu No. 2 coal mine is taken as the research object. Through numerical simulation, theoretical calculations, and on-site industrial trials, a comprehensive analysis of the overburden structural characteristics and the support adaptability at the working face is conducted. It is clarified that a stress arch bearing structure can be formed above the sectional coal pillars during cooperative mining, and this structure is controlled by key strata. The formation of a stress arch bearing structure in the overburden above the sectional coal pillars provides protection for the underlying mining area. A formula for calculating the working resistance of hydraulic supports under the stress arch in sectional coal pillar is derived. Based on these results, the working resistance of hydraulic supports in the coal pillar area is calculated and selected. Field application shows that the working resistance of the support is 10,000 kN in the fully-mechanized top-coal caving working face, and is 9000 kN in fully-mechanized working face, meeting the support requirements and ensuring safe mining at the working face. This study provides a valuable engineering reference for achieving cooperative mining of abandoned sectional coal pillars and lower layer coal seam in stratified mining method.

The Effect of Wetting–Drying Cycles on the Deterioration of the Physical and Mechanical Properties of Cemented Paste Backfill in Open-Pit Coal Mines

To promote the sustainable exploitation of open-pit coal resources, waste is used as backfill material to realize the comprehensive utilization of solid waste mine resources. We proposed a mining method that is a combination of the highwall mining and filling mining methods. Cemented paste backfill (CPB) samples were prepared with high-clay-mineral-content marl particles as aggregate and normal Portland cement, sulfoaluminate cement and gypsum as cementing materials. The physical and mechanical properties and microstructural evolution of CPB with different binder ratios under wetting–drying cycles were measured. The results showed that the CPB with 0–3 wetting–drying cycles underwent shear and tensile coalescence, and that with 4–10 cycles underwent shear coalescence. The unconfined compressive strength (UCS) and elastic modulus (EM) decreased exponentially with increasing number of wetting–drying cycles but decreased exponentially and cubically with increasing porosity, respectively. The EM is more sensitive to gypsum content than the UCS. CPB deterioration was divided into an initial deterioration stage and a secondary deterioration stage. The evolution curve of the total damage variable presents an ‘S’ shape, with an initial damage stage, an accelerated damage expansion stage, a decelerated damage expansion stage and an end damage stage. The research results provide a basis for improving the recovery rate of resources under highwall conditions, and the extensive utilization of stripping materials, and promote the coordinated development of coal resource exploitation and environmental protection.

Comprehensive Assessment and Empirical Research on Green and Low-Carbon Technologies in the Steel Industry

The iron and steel industry is the leading industry supporting China’s industrial sector. Currently, there is less assessment work on green and low-carbon technologies for the iron and steel industry. This study clarifies the overall strategy of technology assessment by researching the relevant theories and methods of technology assessment. The study further establishes a scientific and reasonable comprehensive assessment index system of green and low-carbon technologies for the iron and steel industry from the aspects of technology index, economy and promotion, and application, including factors such as 11 indexes, the amount of energy saving, carbon dioxide emission reduction, and the resource recovery rate by utilising analytical and comprehensive methods and combining with the characteristics of the technologies. By analysing and comparing the advantages and disadvantages of the commonly used assessment methods, the entropy weighting method, grey correlation analysis method, and TOPSIS (technique for order preference by similarity to an ideal solution) method are combined and optimised to construct a comprehensive assessment model. The Latin hypercube sampling method is also introduced to analyse the technical parameters in combination with the evaluation model. Finally, fourteen iron and steel green and low-carbon technologies were selected for case assessment and uncertainty analysis of technical parameters, and it was found that the comprehensive assessment result of gas combined cycle power generation technology was optimal. After determining the weights of each assessment indicator through the entropy weighting method, it is concluded that the technical performance indicator > economic indicator > promotional indicator. A comparative analysis of the results under the three preference decisions concludes that technical performance is the main obstacle to improving the comprehensive assessment score of the technology, followed by the economics of the technology. Finally, the uncertainty analysis of the technical parameters shows that the fluctuation of the technical parameters not only affects the performance of the technology, but also affects the weights of the indicators and the comprehensive evaluation results of the technology.

A new roof cutting technique to enhance the stability of underground tunnels and improve the recovery rate of coal resources: a case study

A new roof cutting technique to enhance the stability of underground tunnels and improve the recovery rate of coal resources: a case study

Migration behavior of germanium and its related elements in zinc hydrometallurgy process

Lead-zinc sulfide ore is one of the raw materials for the recovery of strategic germanium resources. Due to the complexity of its mineralization and the diversity of elements, the occurrence and migration of germanium and its related elements in the process of zinc hydrometallurgy is still a mystery. This leads to the recovery efficiency of germanium is always in a disappointing state, which seriously reduces the economic benefits and resource recovery rate in the process of germanium recovery, and limits the development of some cutting-edge industries. Therefore, in view of the above problems, based on the properties of germanium compounds in lead–zinc sulfide minerals, this study analyzed the occurrence state and quantity of germanium in the products of each stage in the process of zinc hydrometallurgy by ICP, XRD, FT-IR, SEM, XPS, Raman spectrum and TG, so as to reveal the reaction behavior and migration law of germanium compounds in the process of zinc hydrometallurgy. The results indicate show that the two roasting will lead to the mutual transformation of GeO2 crystal form between soluble and insoluble, especially in the process of reduction and volatilization of zinc leaching residue. The phenomenon of soluble GeO2 to insoluble GeO2 is particularly significant, and the germanium-containing silicate cannot be reacted in the whole process. In addition, zinc blende, zinc ferrite, tin dioxide and other substances that exhibit isomorphism with germanium compounds will carry germanium into lead slag due to their low solubility. Finally, in view of the problems existing in the current germanium recovery process, positive solutions are proposed to introduce green additives in the two roasting stages to improve the phase of germanium, and to add oxidants or reducing agents in the leaching stage.

Optimization of mining methods for deep orebody of large phosphate mines

Introduction: Taking Yunnan Phosphate Group Co., Ltd. Kunyang Phosphate Mine No. 2 as the engineering background, this study aims to explore mining methods for deep ore bodies in phosphorus mines. Three mining schemes, namely open-pit mining, open-pit deep concave mining, and underground mining, were carefully selected for optimization. This article thoroughly analyzes the three schemes from various perspectives, including technical, economic, safety, and other aspects.Methods: The assessment of these aspects was conducted using the entropy weighted TOPSIS method. The technical aspects focused on evaluating the mining methods employed in each scheme. The economic aspects considered factors such as initial investment, resource recovery rate, phosphate content, production scale, infrastructure, and mining costs. Safety aspects took into account transportation safety and production safety. Additionally, the analysis considered environmental impact as one of the key factors. In total, 10 indicators were quantified to provide a comprehensive evaluation. To assess the schemes, the positive and negative ideal distances (Di+, Di−) and the relative proximity (Ci) for open-pit mining, open-pit deep concave mining, and open-pit to underground mining were calculated. These calculations helped to determine the relative performance of each scheme.Results: The relative closeness values (Ci) for Scheme 1, Scheme 2, and Scheme 3 are determined as 1.00, 0.09, and 0.68, respectively.The evaluation results indicate that the relative closeness (Ci) for open-pit mining in Scheme 1 is 1.00, for open-pit deep concave mining in Scheme 2 is 0.09, and for underground mining in Scheme 3 is 0.68. Through comparison and analysis of these results, it can be concluded that open-pit mining is the most optimal method. However, considering the fact that the open-pit portion of Kunyang Phosphate Mine No. 2 has already been extensively mined, the study recommends underground mining as the best mining plan for the phosphate mine.Discussion: By applying the entropy weight TOPSIS method to underground mining, this study overcomes the challenge of transitioning from qualitative to quantitative analysis for selecting mining methods. The mathematical approach enables the presentation of optimal mining techniques in a more precise manner. Through comparison of relative closeness, an optimal solution can be selected. This method holds significant value not only for selecting suitable mining methods for phosphorus mines but also for choosing optimal solutions for underground mining methods, drainage, ventilation, and other relevant considerations.

Simulated Prediction of Roof Water Breakout for High-Intensity Mining under Reservoirs in Mining Areas in Western China

China is rich in coal resources under water bodies. However, the safety prediction of high-intensity mining under water bodies has long been one of the problems encountered by the coal industry. It is of great significance to realize safe mining under water bodies, improve the recovery rate of coal resources and protect reservoir resources. Therefore, this article takes the No. 5 coal seam and No. 11 mining area of the Wangwa Coal Mine as the research object, and integrates physical simulation, numerical simulation, theoretical analysis, and other methods to study the development height of water-conducting fracture zones in fully mechanized top coal caving mining. Solid–liquid coupling physical simulation tests reveal the failure characteristics of overlying strata in goaf and the seepage law of reservoir water under the influence of mining. By comparing the monitoring data of borehole leakage, the measured data obtained by borehole monitoring with the height data of the water-conducting fracture zone obtained by the traditional empirical formula of three-under standard, the error between the two is as high as −29.39%. In this case, the variance correction coefficient is used to correct the empirical formula, and on this basis, in order to effectively protect the surface water dam and water body, the mining height of the coal seam in the working face with limited height mining is inversely derived. The research results provide a basis for the safety prediction of high-intensity mining under the reservoir dam in the ecologically fragile areas of western China and a scientific guarantee for the formulation of safety measures under such conditions.

Experimental Study of the Mechanical Properties of a Flexible Grid Filling Body

The fill mining method has become more widely used due to its advantages of a high resource recovery rate, reliability and safety, and reduced surface tailings storage. However, the mechanical properties of the cemented fillings in fill mining are similar to those of ultra-low strength plain concrete, and there are problems such as high brittleness, low bending and tensile strength, and sudden failure. Using a flexible grid as reinforcement material, uniaxial compression, tensile, and shear tests of a flexible grid filling body were carried out, and the results were compared with the mechanical properties of the filling body without the flexible grid. We drew the following main conclusions: the uniaxial compressive strength of the flexible grid filling body gradually increased with the decrease in the grid spacing (the increase in the grid density); the grid dimension had little effect on the uniaxial compressive strength of the flexible grid filling body. The uniaxial tensile strength and shear strength of the flexible grid filling body increased with the increase in the grid dimension; and they first increased and then decreased with the increase in the grid spacing, and there was an optimal grid spacing. From the perspective of the macroscopic failure mode, the flexible grid filling body specimen after the uniaxial compression test had a conjugate shear failure, forming a “dumbbell shape” with two large ends and a small middle. After the uniaxial tensile test, the macroscopic failure mode of the specimen was tensile failure. After the shear test, the macroscopic failure mode of the specimen was shear slip failure. It is proposed that the tensile strength, shear strength, cohesion, and internal friction angle strengthening coefficients of the flexible grid filling body with different dimensions and spacing are higher than the elastic modulus strengthening coefficients. The experimental results can provide a certain reference and guidance for mine filling.

A New Method of Regional Mining Subsidence Control for Sustainable Development in Coal Areas

Coordinated and sustainable development of production-living-ecological space (PLES) is directly related to the global energy security and quality of life in coal areas. However, the current surface subsidence control methods have some problems, such as low resource recovery rate, high cost, insufficient materials, which are difficult to meet the requirements for the PLES sustainable development in coal areas. Under this background, based on characteristics of surface subsidence and deformation due to sub-critical extraction, the large protection area, and high deformation tolerance in PLES of mining areas, the new method of regional mining subsidence control was proposed, with the combination of source control and ground rehabilitation. The effectiveness of the method was verified by numerical simulation results and practical applications, and the application principles and implementation methods were proposed. The research results could provide technical support for the sustainable development of coal areas in major coal producing countries of the world.

Material Flow and Waste Recovery in a Community-Based Waste Management System in Batu, Indonesia

Indonesian government has promoted to establish Community Based Waste Management (CBWM) in Indonesia to increase the resource recovery rate and to reduce the amount of landfilling waste in stead of conventional the waste management. In CBWM, recyclable materials are recovered by neighborhood communities and only the residual waste is landfilled. Although CBWM can contribute to the reduction of green house gas emission and conservation of resources, the effectiveness of CBWM on the reduction of waste is an clear due to a lack of detailed information about CBWM such as economic benefit, waste flow and its sustainability. The aims of this study are to identify the waste flow in common CBWM in Indonesia and to evaluate the effectiveness of CBWM for reduction of MSW carried to a landfill site. The TPS3R Dadaprejo Mandiri (DM-TPS) in Dadaprejo Village, Batu City, Indonesia was investigated as a case of CBWM. Waste composition was surveyed for 8 consecutive days on three separate occasions in 2021 and 2022. Each resource was weighed and measured at each step of the process to analyze waste flow. Monthly data summarizing the amount of each resource separated at DM-TPS was obtained from their records. Information about the amount of waste and resources collected by the 13 waste banks was obtained by interviewing the administrators of those waste banks. The amount of waste carried to DM-TPS during the first, second, and third surveys averaged 5.61, 6.65, and 5.40 t/day, respectively. Of the 9 categories of waste, the largest was the organic waste. Fruits and vegetables made up the largest percentage of resources followed by plastic bags. The average resource recovery rate was approximately 15.2%. However, the composition survey revealed that the potential resource recovery rate was approximately 39.5%. In order to increase of resource recovery rate, the corporation of households on simple source separation at home would be required.

Micro-CT characterization on pore structure evolution of low-permeability sandstone under acid treatment

Permeability enhancement via acid has drawn broad attention in mining and oil industries to treat low-permeability formations to increase the resource recovery rate. In this study, experiments including static acid permeability enhancement tests, flooding acid permeability enhancement tests, and micro-CT scanning were conducted to investigate the mechanism of permeability enhancement and changes in pore structure during acid treatment. First, the extent of reaction between low-permeability sandstone samples and four different acids was evaluated by static tests. The hydrochloric and formic acids exhibited good performance to dissolve filling minerals during static tests. Second, acid flooding in sandstone cores was carried out under reservoir conditions. After acid flooding, the porosities of sandstone cores were significantly increased and a decrease in pressure difference was observed, demonstrating a permeability increase. The pressure difference of hydrochloric acids was lower than that of formic acids at the end of flooding, and the permeability results indicated that the percentage of permeability increase by hydrochloric acid treatment and formic acid treatment were 283% and 120%, respectively. Third, all samples were scanned by micro-CT before and after acid permeability enhancement tests, and CT images were analyzed to study changes in pores, pore throats, and coordination numbers using Avizo software. The mineral compositions and 2D micromorphology were characterized by SEM-EDS, XRD and ICP. After acid treatment, the number of interconnected pores, pore throats, and their equivalent radii all increased, leading to a higher permeability. The improved permeability was mainly due to the dissolution of dolomite, which was identified by SEM-EDS and ICP.

The Steady Seepage Line Equation of Ionic Rare Earth Ore (IREO) In Situ Leached with Long Strip Bare Feet and Its Application

Without a reliable design method for the leaching and seepage step of in situ leaching (ISL), problems such as low comprehensive resource recovery rate and frequent geological disasters such as landslides are prominent. This study established a simplified “liquid injection-collection” plane model of ISL with a linear barefoot type rare earth mine as the research object. The steady seepage line equation was derived based on groundwater dynamics and the Dupuit assumption. Then, engineering verification and calculation error analysis were performed. The seepage line equation is expressed as a piecewise function, where the seepage line in the liquid injection area is the upper half of the ellipse line, and the one in the non-liquid injection area is a parabola. The calculation error increases along the flow field direction. The seepage gradient, bedrock gradient, liquid injection range, and relative permeability coefficient have limited influence on the calculation error of the equation. The seepage line equation can be fairly applied in ISL. The seepage line equation can provide a theoretical basis for the “prior prediction (design)” of the “liquid injection/collection” leaching and seepage process in ISL.

Study of the response characteristics of the water–force coupling action of hard coal bodies in steeply inclined coal seams

Study of the pre-blast weakening of hard-top coal water injection is especially important to solve problems related to the low recovery rate of coal resources and frequent dynamic disasters due to the low degree of fragmentation of hard-top coal during high-stage fully mechanized top-coal caving in steeply inclined coal seams. With the application of rock mechanical tests and numerical simulations, this study carries out mechanical property testing on natural and water-saturated coal samples, investigates the effect of moisture on coal sample mechanical properties in meso-scale, and quantifies the degradation of coal samples under moisture due to mollification. It also reveals the interaction between water and acoustic emission signals based on the statistics of acoustic emission count and energy. A numerical model is established to analyze coal sample internal stress distribution features before and after water injection in macro-scale. Moreover, the detailed mitigating measures for top-coal water injection for engineering practice are designed. The results demonstrate that the mechanical properties of coal samples are significantly affected by moisture-induced degradation. The failure and collapse degrees of water-saturated samples are generally larger than those of natural samples. When the water content is higher, the acoustic emission count and energy of the coal sample are smaller—presenting a negative correlation. The internal stress of coal samples before and after water injection differs significantly. When subjected to water, the top-coal stress releases and transfers, and the peak value is significantly reduced. This study has verified in macro- and meso-scales that top coal can be fully weakened under water–force coupling. The findings of this study are of practical significance for safe and efficient mining and provide a reference for presplit weakening of hard-top coal during horizontal sublevel fully mechanized top-coal caving in steeply inclined coal seams.