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.

In an electrolysis tank where electrorefining or electrowinning is performed, differences in the local density of the electrolyte due to variations in ion concentration bring about natural convection near each electrode. This natural convection affects the supply of metal ions from the bulk solution to the cathode surface and the movement of ionic species generated at the anode surface. This paper describes calculation methods that are based on boundary layer theory and have been proposed in the past to analyze natural convection caused by the ion concentration distribution in an electrolyte. The boundary layer theory makes it possible to understand the diffusion-limited current density at the cathode by linking it to the concentration of metal ions in the electrolytic bath and the physical properties of the electrolyte. First, we introduce a method of converting the boundary layer equations from partial differential equations into ordinary differential equations using similarity variables, and then derive theoretical formula for the flow velocity of natural convection and the diffusion-limited current density at the cathode with the help of numerical calculations. Furthermore, we derive a formula for estimating the diffusion-limiting current density from the size of the electrode and the physical properties of the electrolyte using dimensional analysis, which is widely used in fluid mechanics. Next, we will explain the von Kármán-Pohlhausen integration method as another approach for analyzing the flow velocity of natural convection and current density distribution. Experimental methods for observing the boundary layer and a calculation model improved for application to electrolysis at current densities below the diffusion limit are also presented.

In recent years, there has been an increase in cases where new tunnels are excavated parallel to existing tunnels along highways and major national roads. Although separation distances are secured in the planning and design phases to avoid interference between the tunnels, there can still be impacts on existing tunnels in poor ground conditions. In areas with poor ground stability, the excavation of a new tunnel can still lead to unanticipated impacts on the structural integrity of nearby, pre-existing tunnels. Previous research has documented measurement results and numerical analyses of factors such as existing tunnel lining stress and the behavior of the intermediate ground. However, few studies have sufficiently compared and discussed measurement results after the completion of new tunnel excavation with predicted analysis results. This study aims to analyze measurement data from an actual parallel tunnel construction project and examine the behavior of both the existing and new tunnels through numerical back-analyses based on these measurements, assessing the validity of these numerical predictions. From the measurements of ground displacement, lining stress, and crack displacement in the existing tunnel, it was observed that the loosening loads initially acting during the excavation of the existing tunnel were reactivated by the excavation of the new tunnel, indicating the effects of close-proximity construction. The back-analysis results showed discrepancies between measured and predicted values of crown settlement and inner displacement when using a standard stress release rate for the ground properties and lateral earth pressure coefficient of the existing tunnel in the new tunnel excavation analysis. Adjusting the stress release rate brought the displacement predictions closer to the measured values, and aligning the displacements allowed the lining stress to be reasonably predicted. Consequently, this approach to back-analysis demonstrates that it is possible to estimate the impact on the existing tunnel during new tunnel excavation.

Efficient removal of oxygen (O) impurities from titanium (Ti) scrap is necessary to accelerate the recycling of Ti scrap. However, deoxidation of Ti is extremely difficult, both thermodynamically and technically. In this study, we developed a deoxidation technique that uses Yb (a rare earth metal with high vapor pressure at elevated temperatures) to directly remove O dissolved in solid Ti. Experimental results showed that deoxidation using Yb in halide salt fluxes such as LiCl and LiF produced Ti with O concentrations of 520-1400 mass ppm. The O concentration in deoxidized Ti samples was reduced to a level lower than that in Ti under the Yb/Yb2O3 equilibrium, probably owing to the decrease in the activity of Yb2O3, which was the deoxidation product, caused by its dissolution in the fluxes. In contrast, when vapor of Yb metal and halide salts were supplied to Ti samples via a gas phase, the Ti samples were deoxidized to the same O concentration as that under the Yb/Yb2O3 equilibrium. This deoxidation limit was controlled by the Yb/Yb2O3 equilibrium. The supply of halide salt vapor did not affect the deoxidation limit. The proposed deoxidation method is expected to help scale up the recycling of Ti scrap and ensure efficient utilization of resources.

To provide more reliable data, liquidus lines and solidus lines of the Ni-Co-Cu system in the temperature range from 1400 to 1750K were determined by Thermogravimetry-Differential Thermal Analysis (TG-DTA). The liquidus lines and the solidus lines were determined for low Cu and high Ni compositions, for which data were lacking in previous studies. The obtained results can be used to determine the temperature required to melt the metal obtained by reducing waste lithium-ion batteries (LIBs) in the high-temperature metallurgical process of metal recycling from waste LIBs.

A classification system based on a convolutional neural network was performed to recognize the different combustion patterns of Cu concentrate-SiO2 mixtures tablets under oxidation gas to estimate their combustion behavior and phase changes in flash smelting.A suspended-combustion-test method involving high-speed digital microscopy and thermal measurements was employed to characterize the combustion behavior of each sample.The time series images-based pattern recognition method enabled the calculation of the chemical composition of the blended concentrates by transforming the network output into a probability distribution.The combustion of the blended-concentrate tablet was different from that of each single-concentrate tablet in terms of the combustion pattern, such as the shape of the molten part, and the temperature change pattern.It is interpreted that the change in the free surface shape of a tablet is an important region for combustion pattern recognition.Thus, only when blended samples were used as training data as well as single samples, a good correlation could be obtained between the measured and predicted values of its chemical compositions.

For developing countries endowed with mineral resources, mineral resource development is often considereda short-term growth strategy compared to other industries. However, the exploration and economically viable extraction of mineral resources require substantial funds and advanced technology. Given the inability of developing countries to cover these costs independently, the involvement of foreign companies becomes crucial. Nevertheless, there are numerous challenges that must be addressed for foreign companies to enter the market, including the absence of legal and enforcement systems, inadequate infrastructure, and various risks. Moreover, even if foreign companies successfully enter the market, developing countries confront issues such as effective management of mining revenues and development investments, preparations for resource depletion, environmental and safety measures, and strategies for mine closures. To ensure the sustainable development of developing countries through the exploration and utilization of mineral resources, it is imperative to address a broad spectrum of issues, spanning from the establishment of robust legal systems to the implementation of comprehensive environmental measures. In this regard, support from developed countries is crucial. Japan boasts considerable expertise in the mining sector, and if the Japan International Cooperation Agency (JICA), tasked with aiding resource-rich developing nations, leverages Japan's knowledge to assist in the mining and economic development of these countries, it could pave the way for a sustainable and stable supply of mineral resources to the international market. This endeavor would also hold great significance for the revitalization of the domestic mining sector and the growth of other industries in Japan. For this reason, JICA initiated a project named “Shigen-no-Kizuna” = “Bond in Mineral Resource Field” (Human Resources Development Program in the Mining Sector) in fiscal year 2014.

We evaluated the absorption characteristics and phase state of a biphasic CO2 absorbent using 2-amino-2-methyl-1-propanol (AMP), diethylene glycol diethyl ether (DEGDEE), and water (H2O). We set the AMP concentration at 30 wt%, and adjusted the H2O and DEGDEE weight fractions. It was experimentally confirmed that phase separation of the absorbents occurred due to the progress of CO2 absorption. As the concentration of water decreased, it was separated into a lower phase, which consisted almost entirely of AMP, H2O and absorbed CO2, and an upper phase, which consisted of mostly DEGDEE. In the experiment, an absorbent composition of 30 : 20 : 50 wt.% (AMP:DEGDEE : H2O) was maintained in the liquid state at 313 K and a CO2 partial pressure of 0.1 atm in the absorption step and at ≥ 343 K and a CO2 partial pressure of 1.0 atm in the regeneration step. Under CO2 capture conditions, this adsorbent was separated into two-liquid states in the absorption step, whereas it exhibited a uniform single phase in the regeneration step. Therefore, it could operate under CO2 capture conditions as a biphasic absorbent. The amount of CO2 cyclic absorption of this absorbent was twice that of conventional monoethanolamine (MEA) absorbents when the regeneration temperature was set at 363 K.

Among the raw material production industries that use a large amount of limestone, the effectiveness of limestone usage in the steel production industry has been evaluated and the optimization of limestone addition ratio has been investigated. Based on the past research and development results concerning the CaO added basic sinter production technology, the phenomena of permeability deterioration caused by the excessive CaO addition and the actual operation tests, the multi-component calcium ferrites (SFCA) in sinter that have been currently intensively researched and developed have been evaluated. The reducibility of sinter in blast furnace has so far focused on the lumpy zone up to 1000 °C, but in the future research, it will be necessary focused on the reducibility and permeability in the cohesive zone up to 1000~1500 °C. The current chemical compositions of SFCA has the good reducibility and permeability in the cohesive zone, but the research and development are needed to maintain the appropriate range of CaO (CaO/SiO2 = 1.5~2.0) and further to improve the reducibility and permeability. The future progress of the research and development has been presented.