A composite strong-acid cation exchanger was developed for use in high-flow-rate metal recovery systems by coating a porous silica support with a styrene-divinylbenzene copolymer and subsequently introducing sulfonic acid groups. The purpose of this study was to clarify how structural factors of the composite exchanger affect adsorption-desorption performance under dynamic flow conditions relevant to compact and high-throughput recovery processes. A series of samples with different crosslinking ratios, sulfonation feed ratios, and particle sizes was prepared, and their adsorption properties were evaluated using Ni(II) and Cu(II) as model metal ions. Batch adsorption tests were carried out to examine adsorption rates and distribution behavior, while column experiments were performed to investigate breakthrough behavior, elution characteristics, recovery efficiency, scale-up performance, and cyclic stability. The results showed that the sample prepared with a crosslinking ratio of 15%, a sulfonation feed ratio of 2 equiv., and a particle size of 250-500 μm exhibited the most favorable overall performance among the materials examined. This sample showed rapid adsorption, sharp breakthrough and elution behavior, high recovery rates for both metal ions, and stable operation in scale-up and repeated adsorption-elution cycle tests. In addition, under high-flow-rate conditions, the optimized composite exchanger exhibited superior recovery behavior compared with the reference commercial resin. These findings demonstrate that systematic optimization of the resin structure and particle size is essential for maintaining efficient ion-exchange performance at high flow rates, and that the developed composite cation exchanger is a promising separation material for compact metal recovery systems.
This study examines the effects of rock spalling on support elements in order to prevent cracking and to ensure the integrity of the support system and safety during shaft sinking. When the ventilation shaft at the Horonobe Underground Research Center reached a depth of more than 250 m, severe rock spalling occurred, and cracks developed in the concrete lining immediately above the spalling zone. Therefore, a three-dimensional numerical analysis of the shaft was conducted to estimate changes in the stress distribution within the concrete lining caused by the spalling. The simulation results indicated that the vertical tensile stress in the concrete lining increased as the spalling progressed. By integrating the analytical results with field observations and considering various support patterns to prevent further rock spalling, a flowchart for selecting the optimal support pattern was developed. Shaft sinking was subsequently completed to a depth of 500 m without significant damage to the concrete lining or excessive spalling. The flowchart developed in this study will contribute to the selection of optimal support patterns for future shaft sinking projects.
Rock excavators equipped with cutting functions, such as roadheaders, surface miners, and various coal mining machinery, are widely used in civil engineering and mine operations. In the design and development of these machines, numerous researchers have conducted theoretical, experimental, and numerical studies to understand the rock cutting mechanisms using bits. This review article summarized research trends and future challenges concerning rock cutting mechanisms, focusing on theoretical and experimental studies. First, the technical terminology for cutting processes of a chisel bit or a point attack bit was introduced, and various equations for calculating cutting resistance based on the two- or three-dimensional cutting theory were described in detail, including their background, derivation processes, and relationships. Then, recent experimental studies on the factors affecting cutting resistance of a point attack bit were reviewed while mentioning key achievements with a chisel bit. The law of similarity and the cutting processes of multi bits mounted on a rotating drum were also explained since they are essential for the design and development of actual rock excavators. Studies on cutting hard rocks and mining deep seafloor mineral resources are ongoing, and hence it will be necessary to clarify the rock cutting mechanisms under these complicated severe conditions with utilizing accumulated knowledge introduced in this review article.
This paper provided an overview of recent advances in simulation technologies for comminution processes, focusing on analysis techniques based on the Discrete Element Method (DEM), categorized into grinding media behavior and material particle behavior. Regarding the simulation of grinding media behavior, we explained that engineering-important physical quantities such as power consumption, grinding rate, mechanochemical reaction rate, and wear amount have strong correlations with indicators calculable from simulations, such as dissipated energy and collision energy. This indicates that a part of the design of comminution processes, which has long relied on experience and intuition, is transitioning toward theory-based design. Additionally, regarding the simulation of material particle behavior, we explained the remarkable evolution of fracture models, in addition to the analysis of grinding and agglomeration mechanisms through coupled analysis with fluids. In particular, addressing the conventional challenge of arbitrariness in parameter determination, the establishment of methods that link experimentally measurable physical quantities with model parameters represents a significant step forward in enhancing the practical utility of simulations. This enables the reproduction of real phenomena in virtual space, even for comminution processes involving complex fracture phenomena, and is expected to contribute to eliminating the black box nature of grinding. In the future, larger-scale and more detailed simulations are anticipated to become possible with further improvements in computational capabilities. Furthermore, by integrating such advanced simulation technologies with AI (Artificial Intelligence) and IoT (Internet of Things) technologies, the digital twinning of comminution processes is expected to accelerate. If systems can be constructed that instantaneously search for optimal operating conditions in virtual space and provide feedback for autonomous control of actual equipment, maximization of energy efficiency and realization of nano-level precision grinding can be reasonably expected. We hope this paper serves as a useful resource for understanding the technological progress in comminution and the current state of simulation technologies.
In secured landfill sites, accurate prediction of leachate volume is essential for stable operation and environmental management purposes. In this study, a tank model was developed using meteorological and operational data to predict seasonal variation in leachate volume. To improve estimation accuracy, the model also incorporates snow accumulation and snowmelt processes. Although the tank model is relatively simple, it demonstrates good performance in simulating leachate volume trends based on weather data. By incorporating snow-related hydrological processes, the correlation coefficient between the estimated and measured leachate volumes during winter and early spring improved significantly, from 0.15 to 0.72. The annual leachate volumes estimated using the model showed over 90% agreement with the measured values, confirming the model’s validity. The results also indicate that refining the estimation of evapotranspiration could further enhance prediction accuracy. This approach provides a practical and accessible tool for the daily management of landfill operations under varying climatic conditions.
To promote the recycling of lithium-ion batteries, it is essential to develop pretreatment technologies that can efficiently delaminate and recover electrode layers containing active materials. In this study, we investigated the applicability of an underwater ultrasonic delamination technique, proposed by the authors, to used cells and commercial batteries. Ni–Co–Mn (NCM) ternary oxide cathodes were used to compare delamination behavior before and after charge/discharge cycles. After cycling, delamination was facilitated by the formation of aluminum fluoride (AlF3) at the interface between the aluminum (Al) current collector and the cathode material. Furthermore, underwater ultrasonic treatment was applied to cathodes from four types of commercial cylindrical cells. While some electrodes were difficult to delaminate by ultrasonic treatment alone, delamination rates exceeding 95% were achieved when combined with a preheating step at 200–400°C. Analysis of the polyvinylidene fluoride (PVdF) binder content and cutting strength of the cathode material revealed that preheating reduced binder adhesion strength. Under these conditions, cavitation impacts generated during ultrasonic treatment effectively acted on both the internal structure of the cathode material and the cathode material/Al foil interface, thereby promoting separation and delamination. Overall, these results demonstrate that underwater ultrasonic treatment, when combined with appropriate pretreatment conditions, can be applied to various commercial spent electrodes with different structures, materials, and degradation states. The technique is expected to offer high adaptability in actual recycling processes, contributing to the expansion of applicability and improved efficiency of the overall recycling workflow.
Carbon dioxide capture and storage (CCS) is expected to be a key decarbonization technology for achieving carbon neutrality. Sensitivity analyses using an energy system model on CCS costs and storage capacity indicate that increasing domestic CO2 storage capacity is economically rational. To increase CO2 storage capacity, we have devised a method of subseafloor CO2 storage using clathrate hydrates (hereinafter referred to as CO2 hydrate storage). CO2 hydrate storage is a method of storing CO2 by forming an artificial hydrate seal within the subseafloor strata, utilizing the property of CO2 to generate hydrates under the low-temperature and high-pressure conditions of the deep-sea around Japan. Numerical simulations of CO2 hydrate generation show that more than half of the injected liquid CO2 dissolves into formation water, while the remainder is ultimately stored in the formation by the hydrate seal. Regarding storage costs, estimation performed with QUE$TOR 2020 indicates that CO2 hydrate storage is less expensive than aquifer storage, because even though the depth from sea-surface is greater, the injection location beneath the seafloor is shallower, resulting in lower well drilling costs.
The global climate crisis has entered a critical phase where mitigation strategies have become imperative for sustainable development. This paper examines the pivotal role of Carbon dioxide Capture and Storage (CCS) technology in achieving carbon neutrality by 2050, following the IPCC’s Sixth Assessment Report that conclusively attributes global warming to human activities. CCS technology represents a vital mitigation strategy, especially for hard-to-abate sectors such as steel and cement production where it may be the only viable decarbonization option. The International Energy Agency projects CCS will contribute to 7.6 billion tonnes of CO2 reduction annually by 2050, requiring a 190-fold increase from current implementation levels. Despite utilizing technologies developed in the petroleum industry, CCS differs fundamentally in its purpose and approach to geological formations, valuing reservoirs as secure storage containers rather than extraction targets. Property variations of CO2 under different temperature and pressure conditions within storage reservoirs present unique technical challenges that distinguish CCS operations from conventional petroleum development. Various implementation models have emerged globally, shaped by different policy approaches. The technology-push approach exemplified by the U.S. 45Q tax credit system has enabled diverse market participants, including smaller local companies, to establish independent CCS operations. Meanwhile, Europe’s market-pull approach, driven by carbon pricing mechanisms, has fostered service-oriented businesses where major oil companies provide integrated CO2 transportation and storage services. Japan’s unique collaborative approach features manufacturing companies, power utilities, oil companies, trading firms, and engineering companies working together under the recently enacted CCS Business Act (2024), which establishes a comprehensive legal framework addressing liability allocation and long-term management structures. The paper concludes that CCS will fundamentally transform the fossil fuel industry’s value proposition, with future energy markets valuing processing efficiency and carbon management capabilities as critical competitive factors rather than traditional calorific values.
The Ofunato Mine mines approximately 2,300 thousand tons of limestone annually. Of this amount, approximately 2,200 thousand tons are supplied to the Ofunato plant of Taiheiyo Cement Corporation (hereinafter “Ofunato plant”) as raw material for cement, and approximately 100 thousand tons are supplied to the local area as aggregate and other materials. For the cement raw materials, mined ore is crushed through various crushing systems, transported by long-distance conveyor belts (BC) to the Ishibashi area, stockpiled once, and then transported by rail to the Ofunato plant. The Ofunato Mine previously mined limestone in two areas, the Sakamotozawa area in Ofunato city, and the Odaira area in Sumita town, Kesen county. (Both are in Iwate prefecture.) However, as the remaining reserves in both areas were decreasing, a development project in the Horoshi area in Sumita town was undertaken to ensure a long-term stable supply of cement raw materials for the Ofunato plant. The planning for this development began around FY2000, and various environmental assessment studies were started since FY 2007. The development work was then carried out over approximately 4.5 years from the second half of FY 2016 to the end of FY 2020. For the Ofunato plant, which resumed production promptly after the great east japan earthquake and has continued stable operations since then, this development has secured enough ore for approximately 100 years of cement raw materials at the significant milestone of 10 years after the earthquake. After the completion of the development work, the mining in the Horoshi area began in FY2021 in parallel with the removal of topsoil, and by FY2023, approximately 3,900,000 tons had been mined (Including topsoil). This report provides the overview of the Horoshi area development project, the initiatives aimed at harmonizing development with ecosystems, and the measures taken during construction to consider the surrounding environment.
Numerical simulations are widely used to analyze the mass transfer in a cell with the aim of improving the efficiency of electrolysis processes. In this study, galvanostatic electrolysis with CuSO4–H2SO4 aqueous solution as the electrolyte and pure copper as the anode in laboratory scale was modeled in order to examine how to simulate the transport phenomenon of ions in the copper electrorefining. A galvanostatic electrolysis test using an electrolysis apparatus with similar dimensions to the model was also performed, and the measured cell voltage was compared with that estimated by the simulation. In the simulation, Cu2+, H+, HSO4− and SO42− were assumed to move according to the Nernst–Planck equation while satisfying the electrical neutrality condition in the electrolyte, and the local equilibrium for the dissociation of HSO4− was also taken into account. The dependence of the diffusion coefficient and mobility of ions on the electrolyte composition was also incorporated into the calculations, aiming to obtain the potential gradient and ion concentration distribution that are close to the actual values.
REE-rich mud and polymetallic nodules located under the seabed at water depth of 5500–5700 m around Minamitorishima island are highly attractive for exploration and development, given the recent paradigm shift towards renewable energies based on green technologies. A numerical analysis was conducted to investigate the flow characteristics and lifting performance of hybrid mining, which involves transporting both REE-rich mud and polymetallic nodules using an air-lift pump for a commercial production system and a pilot test-scale system in the deep sea around Minamitorishima island. The one-dimensional drift-flux model was adopted for analyzing the gas–liquid–solid three-phase flow and gas–liquid two-phase flow in the system. A new scheme, called “the multi solid-phase scheme”, was also developed and devised in the program to account for the particle size distribution of transported ores, such as degraded polymetallic nodules. The results revealed that the program and the scheme could simulate the flow characteristics and the lifting performance of hybrid mining using the air-lift pump well. From the parametric studies regarding the dimensions and operational conditions of the systems, they could also derive useful information and know-how. Further information, such as degradation of polymetallic nodules during the practical operation, is required.
Consider the scenario where carbon dioxide (CO2), a greenhouse gas, is utilized for hydraulic fracturing of high-temperature dry rock, replacing the conventional use of water, and is also employed for heat extraction. In this context, excess CO2 can be sequestered within the high-temperature rock, thereby enabling simultaneous CO2 sequestration and geothermal power generation. However, the characteristics of hydraulic fracturing using CO2 are not yet fully understood. The authors conducted acoustic emission (AE) measurements during a small-scale field experiment involving hydraulic fracturing with both CO2 and water. They compared the effects on existing fractures, the extent of the fractured area, and the degree of permeability enhancement achieved with CO2 and water. The findings have been published in two international journal articles (Ishida et al. 2021 and 2023). This paper presents a Japanese-language summary of those two studies to support ongoing Enhanced Geothermal System projects and other related initiatives currently underway in Japan.
Bitumen extracted from oil sand has garnered increasing attention as an alternative energy source for fossil resources. Since oil sand consist of a mixture of bitumen (10-15 wt. %), water (4 wt. %), and sand (80 wt. %), the separation and recovery of bitumen from oil sand are essential for their utilization. Hot alkaline conditions enhance bitumen separation from sand, but they are unfavorable for the traditional bitumen flotation method using air, as the bitumen surface becomes hydrophilic under alkaline conditions. CO2 has been shown to effectively attach to bitumen droplets under alkaline conditions, but the injection of CO2 decreases solution pH and inhibits bitumen separation. This study applied CO2 desorption of a CO2-loaded amine solution for high-efficiency bitumen recovery. The amine solution remained alkaline even after CO2 loading and maintained a high pH during CO2 desorption, which is beneficial for bitumen separation. Furthermore, the desorbed CO2 bubbles formed evenly in the solution, increasing the opportunity for bubble-bitumen attachment and enhancing bitumen flotation. Pretreatment of oil sand using an amine solution of the same concentration was also conducted for more effective separation of bitumen and sand before flotation. As a result, high purity of 0.92 and a recovery ratio of 0.85 bitumen were achieved using the proposed method on real Canadian oil sand at 95 °C and 1 atm. Additionally, considering the integration of the CO2 desorption stage in the CCS process with the proposed method, a significant amount of energy for heating hot water for bitumen separation could be saved, which could reduce greenhouse gas emissions.
Tantalum (Ta), one of the rare metals, is mainly used for high-performance capacitors. While the increasing importance of Ta, its supply has many problems, e.g., imbalanced production and aspects such as conflict minerals. Recycling has a strong impact on the stable and responsible supply of materials, however, both hydro- and pyro-metallurgical procedures have many problems with the environmental impact and the operation cost. Considering the above situation, the authors have developed a novel recycling process of Ta using “dry aqua regia”. This is a molten salt consisting of ferric chloride (FeCl3) and potassium chloride (KCl) and has already been applied for the recycling of platinum group metals (PGMs) and rare earth elements (REEs). In this study, the authors chlorinated Ta using this dry aqua regia and recovered tantalum oxide by the hydrolysis of chlorinated Ta. As a result, we succeeded in the chlorination of Ta at 630 - 670 K, which is a relatively low temperature for the pyrometallurgical procedure. Chlorinated Ta was recovered as an oxide by hydrolysis with water or nitric acid leaching, with impurities consisting of iron oxide. The recovery rate of Ta was up to 77.5 %, and the loss was suggested as volatilization during the chlorination. These results suggest that the procedure using “dry aqua regia” can be an effective recovery process for Ta.
Because of their compact size and high output power, hydraulic systems are commonly used in various industries (e.g., in large machining tools and civil engineering equipment). Tele-operation of such systems has been introduced for dangerous tasks such as disaster site rescue, undersea surveys, and work in outer space. Workers at a work site may accidentally enter the danger area of operating construction equipment. Therefore, operators must keep track of the situation in their work environment, which prevents them from fully concentrating on the work, decreasing work efficiency. It is extremely important to solve the above problems to increase the efficiency of tele-operation. This study proposes a tele-operation system that uses TCP/IP communication for tele-control of hydraulic cylinders and a new information presentation system that emits a warning sound when a person enters a danger area during work, as detected using an image processing method based on machine learning. The proposed system is compared with a system that uses a 360-degree camera, which can acquire free-view images, to present information on the surrounding environment. In addition, recognition of a person entering a danger area, work accuracy during tele-operation, and the operator’s mental load are evaluated using the NASA Task Load Index. The results show that the proposed information presentation method is superior in terms of reducing the weighted workload score, early detection of persons entering the danger area, and improvement of work accuracy.
Methane Hydrate (MH) has attracted international attention as an alternative energy resource to traditional fossil fuels. Research on production technology has been conducted in Japan to enable private companies to commercialize gas production from the MH in the seabed of Japan’s Exclusive Economic Zone. In this study, a numerical analysis is conducted to examine the multi-phase flow characteristics in a shallow-type MH production system by a gas-lift pump, and to predict the performance of practical production systems. The one-dimensional drift flux model is employed in the program. A numerical model for phase change is devised. Further, the flow characteristics of mud water are implemented in the analysis. The simulation results revealed that slurry flow rate increases as the flow rate of MH particles increases, and the volume fractions and the temperature along the lifting pipe are affected by phase change. The MH production rate: 6912t/d, volume concentration of MH particles: 16.8 – 12.5 %, slurry flux: 4.17 – 5.58 m/s, power requirement: 1240 – 2390 kW are predicted under the dimensions; length and water depth of lifting pipe: 940 and 900 m, water depth at gas injection point: 300 m, pipe diameter below and above gas injection point: 0.4 and 0.5 m, respectively and operational conditions; back pressure: 0.2 MPa(G), volume concentration of mud in slurry: 5%, gas flow rate: 4 – 8 kg/s. We demonstrated that the program could simulate the flow in the MH production system using a gas-lift pump well, and it could derive useful information and know-how in advance for designing and operating the system.
The effects of organic additives and Sb(III) addition to the Zn electrowinning solutions on the current efficiency and crystal structure of zinc deposition were investigated. When only 1 mg/L of sodium lauryl sulfate (SLS), polyethylene glycol (PEG), or gelatin was added, the current efficiency for Zn deposition increased slightly regardless of the type of organic additives. The current efficiency was highest when the gelatin was added, indicating that the gelatin suppresses the hydrogen evolution more effectively than Zn deposition. When only Sb(III) was added into the solution, the current efficiency of Zn increased slightly at 5 mu g/L, but decreased at above 10 mu g/L. When both organic additives and 5 mu g/L of Sb(III) were added, the current efficiency of Zn was similar to that when the organic additive alone was added, showing no synergistic effect of organic additive and Sb. The large holes resulting from the foam mark of hydrogen evolution clearly decreased when PEG and gelatin were added. This is probably attributed to hydrogen gas being more easily desorbed from the cathode by addition of gelatin and PEG. The presence of 10 mu g/L Sb(III) in addition to gelatin and PEG further reduced the number of the holes on Zn deposits. The crystal orientation of Zn deposited from solutions containing both organic additives and Sb(III) showed a similar tendency to that deposited from solutions containing organic additive alone. However, the preferred orientation of a specific plane decreased when PEG and Sb(III) were added simultaneously. The crystal grain size of Zn decreased with the addition of Sb(III), despite the decrease in overpotential. Upon simultaneous addition of SLS or PEG with Sb(III), the grain size of Zn was clearly smaller than that deposited from the solutions added only with organic additive, indicating a synergistic effect of the addition of organic additives and Sb(III).
Various chemical reactions are utilized in the metallurgical industry, such as electrorefining, ion-exchange, solvent extraction, and so on. Identifying the materials involved is essential for a proper understanding of chemical reactions. However, the distributions of metal complexes reported to date are unlikely to be accurate, and discrepancies have been observed between these distributions and their adsorption behaviors to ion exchangers. Hence, the optimization of thermodynamic models has been developed to obtain accurate chemical conditions of complexes. This method is based on the Lambert-Beer law and consists of the first derivative test to determine the number of complex species and optimizations of thermodynamic models to accurately reproduce a series of UV-Vis absorption spectra. The thermodynamic models to be optimized are built on complex formation reactions, mass balances, and electrical neutrality. Activity coefficients of charged and neutral species were estimated using the Debye-Hückel model and the Setchénow equation, respectively. The EQBRM code is employed to calculate concentrations of species. In addition, approaches for verifying the obtained results were investigated, such as ion exchange behaviors and complex structure analysis using X-ray absorption spectroscopy. In this manner, the thermodynamic model optimization method excludes subjectivity and preconceived notions, thereby enabling the derivation of a rational conclusion. This paper illustrates the procedure referring to the analysis of the distribution of cobalt chloro complexes in hydrochloric acid solutions as an example. “kbetar” is an analysis package developed in the R environment for reliable analysis.
Submerged crushing of the cells of lithium-ion batteries (LIBs) for hybrid electric vehicles and small home appliances in approximately 250 L of lime water, saturated calcium hydroxide (Ca(OH)2) solution, in inert N2 atmosphere has been investigated with an aim to establish a safe deactivation process of the spent LIBs even at the charged state. Analysis of hydrogen concentration just above the water surface and at the outlet of the equipment, observation of the crushing, and pH measurement of the lime water were conducted. In the crushing of LIBs for small home appliances, many viscous foams were generated on the water surface, and a large amount of white smoke was emitted as the foam broke up. A processing capacity about 20 kg/h for the LIB cells for hybrid electric vehicles and 200 kg/h for the mobile battery were achieved. Various issues for the industrialization were found through the tests.
Carbon capture and geological storage (CCS) has been widely recognized as an effective strategy that contributes to mitigate the global climate change. However, many reports and papers have pointed out that a large-scale CO2 leak from the reservoir could pose negative health, safety and environmental risks. Dissolution and swelling due to geochemical reactions between the injected CO2 and the rocks in the formation are potential factors that can induce leakage from the reservoir, and it is thought that CO2 may leak along physical leakage pathways such as imperfect cementing on the injection well or cracks in the formation. There is concern that the business risks associated with geological storage will make the evaluation of the economic feasibility of the entire CCS project unclear, hindering the active commercialization of CCS, and delaying the reduction of CO2 atmospheric emissions through CCS. However, to the authors’ knowledge, although there are many studies on risk assessment that are complex and include many factors, no objective and clear indicators to express risks of CO2 geological storage have yet been proposed. This article reviews CCS projects consisting of CO2 capture and transportation, and geological storage. It concludes that it is possible to estimate the project risks of CO2 capture and separation on land from examples of similar process industries. However, for offshore and onshore CO2 geological storage, it is necessary to take into account the risks of sealing failures around the wells that could become leakage routes near the injection wells due to increases in reservoir pressure during the injection and storage process, and the risk of reaching geological defects such as geological faults and cracks as the storage area expands. In this way, it is possible to propose an objective and quantitative risk index based on the cumulative injection volume and verify its validity.
