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By Michael Moats, Weston Hartzell

The stable domestic supply of gallium, indium, and germanium has been identified as a critical need for the USA. Electric arc furnace dusts processed to recover zinc produce a process residue that could be a potential source of these critical materials. An industrial zinc leach residue was characterized to determine the predominant mineral phases and leached with common mineral acids. Atmospheric agitated leaching using sulfuric acid and hydrochloric acid were examined to determine the extractions of gallium, indium, and germanium as a function of concentration, temperature, and time. Extractions of gallium were found to be similar to iron in all experiments. The maximum percentage of Ga, Ge, and In leached into solution were 82%, ~100%, and 89%, respectively.

Aug 8, 2023

By Dan Wang, Qiuju Li, Xiao Guo

The chemical states and ions interaction were significant interest to understanding columbite mineral/acid solution interface dissolution and reaction. The present research work was focus to explore the specific cations ( Nb5+, Fe2+, Fe3+) distribution near the ferrocolumbite mineral/acid solution interface, and determine these cations leaching sequence in sulfuric acid solution. X-ray photoelectron spectroscopy had the potential to provide detailed dissolution information by resolving chemical state and ion distribution of ferrocolumbite during sulfuric acid leaching process. The binding energy decreased in sequence as Nb5+- O < Fe2+- O < Fe3+- O, and increased in sequence as Fe3+- SO4 < Fe2+- SO4 < Nb5+- SO4 which revealed Nb in ferrocolumbite mineral more easily leached comparing to Fe. The ratio of Fe2+- O/Fe3+-O on leaching residue decreased, and Fe2+- SO4/Fe3+-SO4 ratio increased as sulfuric acid contraction increasing suggested that the Fe2+ oxidized to Fe3+ and released Nb from mineral and dissolved into leaching solution. The ratio of Nb/Fe was lower 0.07 with sulfuric acid contraction increasing which meant Nb dissolution promoted by oxidation of iron. The dissolution mechanism of Fe element in ferrocolumbite mineral was Fe2+- O broken and generated Fe2+. Fe2+ was oxidized to Fe3+ in concentrated sulfuric acid leaching solution. The dissolution mechanism of Nb in ferrocolumbite was that Nb5+- O was directly digested by H+, and the released Nb5+ complex with SO4 2− ion formed cation − anion pairs. The coordination of formation Nb5+- SO4 pairs and oxidation Fe2+ in mineral could promote ferrocolumbite dissolution.

Aug 5, 2023

By Yinan Zhang, Yi Luo

The widely used R70 method is modified to measure the self-heating propensity of low-rank coals. This modified R70 method enables the introduction of controlled amount of moist oxygen into the reaction vessel. Three coal lumps were collected from three different locations in a surface mine in the Powder River Basin. The coal samples were tested in oxygen flow with controlled moisture content under adiabatic condition. By measuring the relative humidity at the exhaust exit point of the testing setup, the flux and cumulative wetting heat that is consumed by coal samples can be determined. Through a better way of determining the coal’s specific heat, the total heat, including heat of wetting and coal’s oxidation heat, required to raise coal to a given temperature can be determined. Then, the contribution of heat of wetting at the different stages of the testing is quantified. The effects of evaporative heat through a group of tests have also been quantified. From this research, a better understanding of the effect of wetting heat on inducing low-rank coal’s spontaneous combustion can be acquired.

Nov 30, 2022

By Yingbao Yang, Jinyue Liu, Yonggang Wei, Bo Li

Due to the depletion of copper ore with high-grade and low impurity contents, the raw materials for copper smelting exhibit low copper contents and high impurities. High-impurity elements lead to the poor performance of the final copper product; thus, the removal of impurity elements during the oxygen-enriched copper smelting process is crucial. In this study, based on the production of high-grade matte, the occurrence states of impurity elements (such as As, Pb, and Zn) are analyzed in the input and output materials of the oxygen-enriched smelting process, and the phase transformation mechanisms of impurity elements are revealed during the oxygen-enriched smelting process. The effects of temperature, Fe/SiO2 ratio and oxygen concentration on the distribution behaviors of impurity elements in dust, slag and matte and the removal rates of impurity elements in matte are clarified. The results show that the impurity elements mainly exist as As4, As4S4, As2O3, Pb, PbS, PbO, Zn and ZnS in dust, as FeAsO4, As2O3, FeAsS, PbSiO3, Zn2SiO4 and ZnFe2O4 in slag, and as As, FeAsS, PbS, PbO and ZnS in matte. High smelting temperature, low Fe/SiO2 ratio and low oxygen concentration are beneficial for improving the matte grade and the removal rates of impurity elements Pb and Zn in matte. Low smelting temperature, low Fe/SiO2 ratio and high oxygen concentration are beneficial for removing impurity element As in matte.

Aug 8, 2023

By Dewa Putu Agus Sudarmaja, Widi Astuti, Januarti Jaya Eka Putri, Yayat Iman Supriyatna, Himawan Tri Bayu Murti Petrus, I Wayan Warmada, Siti Nurul Aisyiyah Jenie, Ferian Anggara, Anisa Maulidia, Vincent Sutresno Hadi Sujoto, Sutijan

With the rapid development of renewable energy technology, such as electricity reserves, to store energy for electric or electric vehicles, environmentally friendly energy sources are expected to continue to be fulfilled according to mobility and stationary energy needs. Lithium is the most attractive candidate for energy storage development. The presence of lithium in Indonesia in the Sidoarjo mud content is interesting to be used as an alternative source of raw materials. During the research, sulfuric acid acted as a solvent, and hydrogen peroxide acted as an oxidation agent. Lithium recovery will be studied using a leaching process at various temperatures (30, 45, and 60 °C) and sulfuric acid concentrations (0.5, 1, 2, 3, 4, and 6 mol/L). The increasing temperature, sulfuric acid concentration, and hydrogen peroxide concentration will directly affect the lithium recovery. An increase in sulfuric acid concentration will be directly proportional to the recovery of lithium in the solution. Optimum conditions were obtained at varying 6 mol/L sulfuric acid concentrations and 60 °C temperature variations. The shrinking core model (SCM) studied leaching kinetics, and ash layer diffusion acted as a rate-controlling process. The activation energy of the leaching process was obtained at 38.90 kJ/mol.

Jul 25, 2023

By Yueyue Ding, Yuanhui Li, Zhengrong Li, Pengfei Yu, Kunmeng Li, Zhipeng Xiong

The stress evolution and failure characteristics of overburden were studied during multi-stope mining for a gently inclined thin orebody. Firstly, an indoor physical experiment was conducted on the excavation of a multi-stope mine with an orebody dip angle of 20°. The results show that the vertical stress concentration area gradually shifts to deep-buried rock mass with the mining from shallow to deep buried stopes, resulting in shear failure originating from high stress. On the contrary, the pressure relief zone presents an asymmetric distribution characteristic that is biased towards the upper part of the goaf, resulting in large subsidence and tensile failure of the stope #1 and #2 roofs. Secondly, the numerical simulation model under the same geological condition was established to measure the roof deformation at different stages of mining. The numerical simulation results are in good agreement with the physical test results; the roof displacement is largest in stope #2, second-largest in stope #1, and smallest in stope #3. Finally, the evolution of deviator stress concentration, displacement field and potential failure zone of overburden under different orebody dip angles were studied. As the dip angle of the orebody increase, the deep-buried stope roof changes from deviator stress release to deviator stress concentration in different stages of mining, and shear failure is most likely to be induced when the orebody dip angle is 30°. Meanwhile, the closure displacement of the stope roof decreases gradually, while the tangential displacement increases, so the anti-sliding ability of the support bodies in the stope should be improved. The potential tensile failure zone gradually shifts from the center of the goaf to the upper part, and the deep-buried stope roof evolves from tensile failure to shear failure. Results of this research expected to provide guiding significance for stope support design to control roof deformation and failure, to ensure the safety of the stope.

Mar 2, 2023

By Xiaochao Shu, Kun Wang, Fanwei Meng, Rui Tao

Rapidly searching for carbonatite-related rare earth element (REE) mineralized systems is of paramount importance to explorers, because these systems provide the world’s most significant supply of REE. Biotite and barite are suitable indicator minerals that can offer reliable elemental geochemical information used for REE exploration. In this study, we provided an elemental geochemical dataset of biotite and barite from Cenozoic REE deposits in the eastern Tibetan Plateau, and compared the obtained data to those of biotite and barite forming in other geological settings. The F (i.e., fluorine) contents in carbonatite-hosted biotites are highly variable, with biotites from mineralized carbonatite complexes having much higher values (1.05–2.37 apfu, where apfu = atoms per formula unit) than their counterparts from barren carbonatite complexes (≤ 1 apfu). It is therefore believed that the presence of high-F biotites can be regarded as a sign for predicting REE reservoirs. Barites in REE mineralized systems contain much higher (even one or to orders of magnitude) total REE contents (ΣREE >100 μg/g) relative to those species forming in carbonate-hosted fluorite-barite deposits and open marine environments. This means that the high ΣREE concentration of barite can serve as an effective index for REE exploration. The above information is integrated into a REE exploration program in which the areas with strong local tectonism along cratonic edges are priority exploration targets, and high-F biotites and REE-rich barites can serve as direct indices for rapidly identifying carbonatiterelated REE mineralized systems at a strategic distance from other geological settings.

Jun 9, 2023

By Zong‑yu Li, Shao‑jian Ma, Xiao‑jing Yang, Jin‑lin Yang, Xing‑nan Huo, Heng‑jun Li

Optimizing and adjusting the particle size composition of grinding products is of great significance for improving economic benefits and resource recovery and utilization. In this study, grinding contribution and quantitative separation of impact and grinding mechanism in cylindrical mill were creatively researched, and the grinding technical efficiency of impact and grinding was coupled to the grinding technical efficiency of grinding in drop-off mode. The results showed that the contribution rate of impact and grinding in grinding in drop-off mode varied with the grinding time. On the whole, the contribution rate of impact action increases with the grinding time and gradually becomes stable, and the contribution rate of grinding effect was just the opposite. Under the experimental conditions, the main contribution of the grinding process is impact action, and the contribution of grinding action is auxiliary. In addition, the contribution rate of impact and grinding effect in grinding in drop-off mode was also related to the feed particle size. The contribution rate of impact effect decreased with the decrease of feed particle size, while the contribution rate of grinding increased inversely.

Aug 3, 2023

By Baolin Qu, Jingxin Wang, Cuncang Xu, Bing Wu, Mingyu Zhong

With the development of the coal mine regulation regime, the situation of coal mine safety production in China has continued to improve. However, coal mine accidents have not been fundamentally eliminated; constantly learning from historical accidents can make mining work safer. Therefore, to better understand the coal mine accident characteristics, this study analyzes the tendency of coal mine safety accidents from multiple perspectives, among which all accidents after the establishment of the State Administration of Coal Mine Safety in 1999 are the top priority. The results show that strict national policy, technological progress, and reasonable coal prices are conducive to the safe development of mines. On the contrary, high-intensity centralized production will lead to frequent accidents in the peak season of coal production. In addition, the type of coal mine ownership will have an indirect impact on the occurrence of coal mine accidents. The research results not only play a positive role in the prevention and control of coal mine accidents in China but also have reference meanings for the safety production of coal mines in other countries in the world.

Dec 28, 2022

By A. Dell’Era, E. Ciro, C. Lupi

The indium recovery via electrowinning from sulfate baths has recently gained significant attention as it does not present toxic emissions, hermetically sealed system requirements, human health, and environmental hazards. Following previous works related to the optimization process for AISI 316L and Ni cathode, it was observed significant importance of the metal supports on the input and output parameters of the indium electrowinning process from sulfate solutions. Thus, comparing input and output parameters in both cases seems very interesting. Particularly, regarding the input parameters, the attention has been focused on the electrolyte composition, current density, and temperature, while productivity, morphology, and structure have been considered regarding the output parameters. Considering the productivity as the optimal output, the findings for Ni cathode were better than that for AISI 316L in most of the selected conditions studied. In the case of morphology, indium grains appear rounded and dendritic on the AISI 316L, while those on the Ni cathode show stratified lamellar grains. Anyway, the indium deposit obtained on Ni cathode shows bigger grains independently from the used operative conditions with respect to that on AISI 316L. Regarding the structure, it is clearly tetragonal, but preferential orientation, crystallinity, and deformation of the structure strongly depend on the metal support.

Jun 14, 2023

By Brendan Donnelly, Lasitha Piyathilaka, Jung‑Hoon Sul, Sanghyun Jeong, Benjamin Probyn

Premature failure of armoured face conveyor (AFC) chains due to corrosion is a significant proportion of the unplanned downtime experienced on longwall equipment. The AFC chains are constantly in contact with water and wet coal. The premature failure issue of AFC chains has become more prominent since the introduction of longwall top-coal caving with its additional AFC. Reverse osmosis (RO) is a popular water treatment method for reducing salinity and dissolved solids, but its impact on the corrosion of the AFC chains is unclear. This study has been commissioned to investigate the direct effects of RO water on the corrosion of AFC chains. An immersion test was carried out using AFC chain steel submerged in two water samples: untreated dam water and treated water from an RO treatment plant. Elemental analysis was conducted for both water samples, and four corrosion indices were measured for both water samples. The RO water more vigorously dissolves calcium carbonate scales leading to increased corrosion of the AFC chains although the dam water has much higher levels of calcium, chloride, sulphate, sodium, and magnesium. Bicarbonate ions are the main alkaline factor of water that provides the buffering capacity to acids. Decreased alkalinity without balancing other ions in water causes high corrosivity and decreased scaling tendencies.

Oct 16, 2023

By Xiaohong He, Qing Yu, Kaixiang Zhang, Rui Guo, Minghua Lin, Haoyu Miao

With the increasing depth of coal mining, the coal mine shaft traverses’ strata conditions become more and more complex. Shafts are often located in deep thick strata with unstable aquifers, and coal mining requires short-term rapid drainage of aquifers; the additional stress caused by aquifer water drainage is the direct cause of the shaft-lining failure. Over the years, many experts have conducted research on the shaft-lining damage caused by the consolidation and subsidence of the soil layer induced by the long-term drainage of the aquifer. On this basis, this paper conducts an in-depth study of the dynamic change of the pore water pressure of the aquifer in the short-term drainage and its influence on the response of shaft-lining strain and surface subsidence. The result shows that the Mandel effect of pore water pressure around the shaft-lining is obvious at the beginning of drainage, and the pore water pressure suddenly increases; the increase is independent of the drainage rate, which leads to the sudden increase of the shaft-lining strain value unrelated to the drainage rate. The result also shows that with the gradual dissipation of pore water pressure, the increase of shaft-lining strain is positively related to the drainage rate and negatively related to the drainage distance, and the variation trend of horizontal strain is greater than that of vertical strain, which appoints the main cause of shaft-lining damage.

Mar 16, 2023

By Yunxing Cao, Xinsheng Zhang, Bingbing Meng, Shuaifang Guo, Li Wang, Junsheng Zhang

During the initial process of mining a longwall working face, it is often found that the roof will not collapse readily, which increases the risk of later roof collapse disasters. Explosive and hydraulic fracturing are common roof weakening techniques; however, they have certain limitations. In the present study, CO2 fracturing was used for roof weakening during the initial mining phase in the Changcun coal mine, China, which is a novel strategy. First, by analyzing the lithological characteristics of the working face and applying combined beam theory, the breaking spans of the top coal, immediate roof, and main roof were determined before weakening. An F-35 CO2 fracturing device with a rated pressure of 270 MPa was used, which provides fracturing energy equivalent to 0.968 kg of TNT. The fracture radius of the main roof was studied by ANSYS/ LS-DYNA combined with the hanging roof-breaking theory to determine the optimal layout of CO2 fracturing drills. The results show that the breaking spans of the top coal, immediate roof, and main roof were reduced by 3.99 m, 7.66 m, and 22.03 m, respectively. The main roof collapsed as the working face advanced, eliminating the chance of later roof collapse disasters. Compared with hydraulic fracturing and explosives, CO2 fracturing is safer and more practical, giving it significant application potential.

Nov 23, 2023

By Erik Sundström, Magnus Nygren

Having seen significant improvements to accident rates in the last 40 years, companies in the Swedish mining industry now show a greater focus on the development of safety cultures throughout their organisations and workplaces. However, there is a lack of research examining the different safety initiatives and strategies practiced in the industry today. This study explores the potential influence and consequences such initiatives may have on the development of safety cultures in the Swedish mining industry. Twelve interviews with experts on safety initiatives from four different Swedish mining organisations were conducted and analysed in a process based on qualitative thematic analysis to identify notable connections to safety culture development. The results of these interviews highlight proclivities in the implementation and use of safety initiatives such as subjects of focus, methods and desired effects. This enables the interpretation of the conceptualisation and methods for the development of safety culture in these organisations based on their approaches to safety development. We believe the results of this study can serve as support for discussions on safety culture development in the Swedish mining industry, and be of interest for international mining industries, in addition to approaches to research in this field. However, we also believe it is important to emphasise the opportunities to approach safety culture in mining from different perspectives than those common today.

Jul 19, 2023

By Jian Wang, Xiaoming Sun, Ming Jiang, Fuxin Shen, Chengyu Miao, Wenchao Zhao, Yong Zhang

The increased thickness of the coal seam leads to higher goaf roof collapse height. In contrast, the dynamic pressure from the mining of ultra-thick coal seams generates higher abutment pressures around the mined area and may affect the stability of roadways servicing these panels. To mitigate the deformation and damage issues in the roadways during the extraction of ultra-thick coal seams under a high depth of cover, researchers have proposed combining high prestress constant resistance support and roof-cutting technology (HPCR-RC). The deformation and failure mechanisms of the roadways during the extraction of ultra-thick coal seams under a high depth of cover, along with the mechanisms and field control effects of the combined support system, have been analyzed through theoretical analysis, numerical simulation, and field experiments. The research findings reveal that the high in situ stress, initial excavation disturbance, rotation, and subsidence of the fractured roof of the extra-thick coal seam led to significant deformation and damage in the roadways. High prestress constant resistance support compensates for the initial stress loss, reduces initial stress concentration, and absorbs deformation energy. Moreover, the roof-cutting technology severs the connection between the goaf roof and the roadway roof, disrupts the path of stress transfer, raises the level of roof backfilling in the goaf, and provides support to the roof, effectively alleviating the pressure on the coal pillar ahead and adjacent to the working face. Field experiments have confirmed the effectiveness of HPCR-RC, as indicated by a substantial decrease in surrounding rock deformation and support pressure within the roadways.

Sep 25, 2023

By Ronald C. W. Webber‑Youngman, Philani Larrance Ngwenyama

Entrapments are a huge risk in underground mines. This happens when miners (or any other persons who have entered underground) survive the initial event of an accident, become trapped or lost in unknown and life-threatening locations after evacuation, and remain unaccounted for. At this point, every second counts, and emergency response is highly desired for any chances of saving survivors. The survival chances of the missing persons depend on how quickly they can be located. Rescue teams are often deployed to search for the missing persons underground. However, the rescue teams are forced to search in random and presumed areas of the mine. This is due to the unavailability of information pertaining to the whereabouts of the missing persons. Not only the provision of accurate locations, but various other types of information such as post-accident two-way communication can enhance the survival chances of the missing persons. This information can be provided by a fit-for-purpose missing person locator system. A wide variety of missing person locator systems are already commercially available, some are in testing phases and others in prototype and development phases. This includes tracking, tracing, location detectors and post-accident two-way communication systems. These systems have unique functionalities, capabilities and limitations; making it difficult for mines to select the most effective, applicable and suitable system specific to their mine. In this study, the user requirements for a fit-for-purpose missing person locator system were developed. The purpose of the user requirements was to provide a guideline to facilitate the system selection process. The user requirements can also be used as a tool to measure and evaluate the performance of the selected missing person locator system. The user requirements were also used to predict the success of the selected system under different missing person incident scenarios. The development of the user requirements showed a potential for many other benefits for missing person locator systems.

Nov 2, 2023

By Hakan Uyguçgil, Beril Bayraktar, Adnan Konuk

Mining is one of the industries with the highest risk of occupational accidents in Turkey and globally. The most important feature that distinguishes the mining industry from other sectors is the constantly changing working conditions. The risk of accidents is very high, especially in underground mining, and can happen for several reasons. Therefore, it is essential to carry out all necessary measures in coordination with other disciplines to adapt to changing workplace conditions. The dangers that might occur underground must be determined in advance, controlled at their source, or eliminated since it is critical to take the necessary precautions before the accident. Accident prevention will protect miners’ living conditions by contributing to the country’s economy through reduced labour and production losses. In this research, the data from 13,653 accidents reported in the Karadon Hard Coal Enterprise between 2000 and 2011 were analysed and compared using the Life Table and the Kaplan-Meier methods. Accident records were classified and analysed into four categories: environmentalrelated accidents, equipment-related accidents, person-related accidents, and other accidents. Findings in terms of survival time indicate that environment-related and person-related accidents had the highest risk in Karadon, with equipment-related accidents having the lowest. This study established the reliability of using survival analysis methods to investigate occupational accidents in the mining sector. Given that environment-related and person-related accidents occur in a relatively short period, such as 1 year after starting work, it has been recommended that research be done to improve workplace and occupational safety measures and broaden the training given to miners. Additionally, it has been determined that increasing the use of automation and mechanisation in underground coal mines, combined with developing a thorough equipment safety training programme to raise awareness of the danger, can help prevent person-related occupational accidents caused by the interaction between equipment.

Aug 5, 2023

By Simón Díaz‑Quezada, Ernesto Arancibia, HUMBERTO ESTAY, Tomás Vargas

In situ leaching (ISL) is an attractive technique that enables copper recovery from copper oxide ores that are either low-grade or located at depths too great to be economically exploited through conventional methods. At present, in situ leaching (ISL) has been applied to intact copper oxide ores, in particular, those which (i) present a good natural permeability and (ii) do not require preconditioning. Many copper oxide ores present low natural permeability. These are located above the water table and need preconditioning for the ISL application. The present work shows an economic assessment of the application of ISL to this type of copper ores. The preconditioning technique considered here involves the application of partial mining by sublevel stoping by removing a small fraction of the ore. This technique results in forming an ore bed with good permeability and good solution collection at the stope base. The economic assessment of this approach suggests that it can be implemented with positive net present values to copper oxide ores located at depths in the 100–300 m range, with copper grades above 0.4%. The maximum acid consumption values are below 52.5 kg/t, with blasting procedures designed to produce an ore bed with an average particle size below 6″. The breakdown of operational costs indicates that the mining cost is still very high, accounting for up to 60% of the total operating costs. Therefore, optimizing mining procedures is still necessary for improving the economic outlook of this approach and thus expanding the application field of ISL.

Feb 4, 2023

By Ehab Gomaa, K. A. El‑Nagdy

Backfilling material such as tailing (mine wastes) mixing with cement or gypsum has grown throughout the world’s underground mines. However, despite their growing popularity, the typical hydraulic and mechanical fill types utilized in many mines still exist. Deep underground mining has increased due to the lack of commercial minerals nearby. Mine wastes were considered the main part of backfilling to prevent environmental pollution, ground subsidence after mine abandonment, and mine collapse during deeper extraction phases. The cemented backfill technique is the principal technique used in underground mines, which include cement with fly ash and/or filter dust, cement with tailing material and fly ash, gypsum with fly ash, and synthetic anhydrite with fly ash and have been reviewed. It has concluded that a backfilling material must be selected based on further goals, available material near the mine site, and economic factors. This paper analyzes different backfill material mixtures to create a technique that will increase safety in underground mining conditions and foresees an appropriate formula that gives high uniaxial compressive strength. The multiple linear regression (MLR) on the collected data from the experimental works to construct the relationship between the uniaxial compressive strength (UCS) of the mixture and the components of the backfilling and the prediction formula for expected compressive strength was obtained. The results revealed that the predicted regression equation was robust and reliable to predict the (UCS) for the new components of the filling (cement (CE), filter dust (FD), water content (WC), and time (T)).

Oct 3, 2023

By Maral Malekian, Pat Bellett, Eranda Tennakoon, Fernanda Carrea, Moe Momayez

Slope instabilities in open-pit mines pose a safety risk to workers and a financial burden on production. The direct impact of slope stability on safety and production makes slope failure predictions one of the important challenges in the mining industry. Predicting the precise time of slope failure has been the subject of much research in conjunction with the development of innovative monitoring technology designed to prevent sudden failures. This paper investigates the use of AutoRegressive Integrated Moving Average (ARIMA) model to predict the time of slope failure. Input data such as inverse velocity (IV) and dimensionless inverse velocity (DIV) from 20 slope failures were used to train the model predict the failure time. For comparison purposes, the time of slope failure using the traditional inverse velocity method is also provided. We show that ARIMA provides 90% more accurate predictions than the TIV approach.

Jul 12, 2023