油圧システムは小型で高出力パワーであるため，産業界では大型加工機械や土木機械として様々な現場で活躍している。しかし，災害現場，海底調査，宇宙空間の作業など，人間が立ち入るには危険な作業では遠隔操作を導入することが重要であるが，遠隔操作での課題として，作業状態の確認といった知覚情報や作動部の位置, 奥行の把握等の空間把握が困難である。また，作業現場にいる周囲の作業者が誤って稼働中の建機の危険エリアに進入してしまい，巻き込まれて事故を起こす可能性がある。よって，オペレータは作業環境の状況を把握しながら作業をしなければならず、その結果，搭乗操作による施工に比べて作業の品質の劣化や作業効率の低下を引き起こしてしまう。それゆえ，遠隔操作での作業効率を高めるためには上記の問題解決が極めて重要である。

本研究では，TCP/IPを油圧シリンダの遠隔制御に適用することで遠隔操作を行うとともに，作業中における突然の危険エリアへの人物進入に対し，機械学習を用いた画像処理手法に警告音を使って識別させる情報提示システムを新たに提案し，自由視線映像の取得が可能な360°カメラによる周囲環境の情報提示とを比較することで，危険領域に進入する人物の認知，遠隔操作時の作業精度，NASA Task Load Index （NASA-TLX）によるオペレータの精神的負担度を評価した。以上の結果より，機械学習に警告音を組み合わせた情報提示の手法は，NASA-TLXによるWeighted Workload（WWL）得点を減少させ，かつ危険領域に進入する人物の早期発見と作業精度の向上の点で優位であることを明らかにした。

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.

オイルサンドは，ビチューメン（10-15 wt. %），水（4 wt. %），砂（80 wt. %）の混合物であるため，オイルサンドからビチューメンの分離回収はビチューメンの利用に不可欠である。高温アルカリ条件はビチューメンと砂の分離を促進できるが，ビチューメン表面が親水性になるため，空気を利用した従来のビチューメンの浮上分離法は気泡がビチューメンに付着しにくい課題を有する。CO₂はアルカリ条件下においてもビチューメン油滴に容易に付着できるが，CO₂の流入は溶液のpHを低下させ，ビチューメンの分離を阻害する可能性がある。本研究では，CO₂を吸収したアミン水溶液のCO₂脱離過程の利用に着目した。アミン水溶液はCO₂脱離中にも高pHを維持できるため，ビチューメンの分離に有利である。さらに，脱離するCO₂気泡はビチューメン表面に均一に付着し，気泡とビチューメンの付着機会が増加する。本研究によって，カナダ産のオイルサンドを利用95℃，1大気圧の条件下純度0.92，回収率0.85でビチューメンを分離回収できた。さらに，CCS過程でCO₂を吸収したアミンはオイルサンドからビチューメンの分離へ応用できる可能性が示唆された。

メタンハイドレート（以下MH）は，新たなエネルギー資源として国際的に注目されている。わが国においても，排他的経済水域内の海底下に賦存するMHを商業的に利用するための研究・技術開発が進められている。本研究では，ガスリフトポンプを用いた表層型MHの輸送システムについて，数値解析により内部の気液固三相流れを検討し，システムの性能推定を試みた。混相流の解析には1次元ドリフトフラックスモデルを用い，流動中のMH-水・メタンガスの分解（相変化）モデルと泥水の特性を組み込んだ。その結果，輸送管中のMH粒子群やメタンガスの体積割合や温度の分布は，相変化の影響を受けて変化した。システムの性能として，管長940 m，水深900 m，ガス吹込水深300 m，輸送管径0.4（吹込水深下），0.5 m（上）の寸法諸元で，ガス吹込量4-8 kg/s，背圧0.2 MPa（G），泥水中の泥体積濃度5%の運転条件で，MH生産量が6912 t/d，MHの体積濃度16.8-12.5%，スラリー流束4.17-5.58 m/s，所要動力1240-2390 kWと推定した。本研究で使用したプログラムは，ガスリフトポンプを用いた表層型MH輸送システム内の気液固三相流の流動特性をよくあわらし，システムの設計・製作や実際の操業時に有用な情報を事前に提供することが可能である。

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.

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.

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 μg/L, but decreased at above 10 μg/L. When both organic additives and 5 μg/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 μg/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).

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.

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.

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.

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.

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.

Understanding the leaching mechanism of chalcopyrite from natural resources is important for expanding Cu production via hydrometallurgical processes. This understanding could be effectively achieved by investigating the reaction phenomena using synthetic chalcopyrite with controlled compositions and morphologies. In this study, we prepared bulk samples of synthetic chalcopyrite and investigated the effects of thermal pretreatment on its oxidative dissolution behavior in acidic ferric sulfate solutions. Dense chalcopyrite pellets with a stoichiometric composition (Cu_0.25Fe_0.25S_0.50) were prepared by subjecting the synthetic chalcopyrite powders to pulse current pressure sintering followed by annealing. Thermal pretreatment at 580°C in a vacuum-sealed quartz ampoule resulted in the precipitation of a small amount of pyrite and a slight compositional change in the chalcopyrite phase. Leaching tests in 0.1 M Fe(SO₄)_1.5–10^–4 M FeSO₄–0.18 M H₂SO₄ solution at 70°C revealed that thermal pretreatment increased the Cu extraction rate by approximately one order of magnitude and shifted the corrosion potential to a less noble value. Polarization measurements in 0.18M H₂SO₄ solution at 70°C showed that the anodic dissolution rate significantly increased after thermal pretreatment. We also prepared a nonstoichiometric and pyrite-free chalcopyrite sample and confirmed its high dissolution rate in the acidic ferric sulfate solution. Therefore, we conclude that the enhanced dissolution of chalcopyrite observed after thermal pretreatment is caused not by its galvanic interaction with the precipitated pyrite phase but by the change in its reactivity owing to small compositional changes.

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.

This study investigates the mineral diversity in placer platinum-group minerals (placer PGM) purportedly collected from the Onnebetsu area in Shibetsu City, Hokkaido. Placer particles consist primarily of native elements and alloys and can be broadly categorized into two groups, iridium-group and palladium-group. The iridium-group placer is predominantly composed of rutheniridosmine, osmium, ruthenium, and iridium, with each occurring as both primary and secondary phases. In contrast, the palladium-group placer consists primarily of isoferroplatinum as the primary phase, accompanied by tulameenite, tetraferroplatinum, and ferronickelplatinum as secondary phases. Notably, the iridium-group placer may also contain PGM typically associated with the palladium-group placer in subordinate amounts. In addition to the primary and secondary phases, other PGM occur as inclusions, within the outermost layers of particles, and in exsolution textures. A total of 41 PGM species were identified in this study, along with six unnamed species. The Onnebetsu area stands out as the region in Japan with the highest diversity of PGM discovered to date. This remarkable variety is largely attributed to the palladium-group placer, which is originated from cumulate rocks formed by partial melting of a mantle.

Extensive rainfall can lead to the discharge of untreated mine drainage from abandoned mines. The Ministry of Economy, Trade and Industry aims to promote environmental impact assessments in scenarios where untreated mine drainage discharges may occur due to extensive rainfall. This study aims to develop a risk assessment method for these events, focusing on 26 abandoned mine drainages without responsible parties. We estimated metal concentrations at discharge points under the assumption that untreated drainage is released. A tiered system was used for the risk assessment: Tier 0 evaluates risks using river flow rates during droughts, while Tier 1 uses simulated post-rainfall river flows via AIST-SHANEL.

In the Tier 0 assessment, two mine drainages (No. 5 and No. 8) exhibited Cd, Pb, As, Cu, Zn, Fe, and Mn concentrations below environmental standards, indicating that high dilution effect contributed to a low-risk discharge even after a certain period following extensive rainfall. In the Tier 1 assessment, even for mine drainages assessed as high-risk in the Tier 0 assessment, some mine drainages, which initially assessed as high-risk in Tier 0, showed metal concentrations below environmental standards for up to 7 days following peak rainfall, suggesting that high flow rates can mitigate discharge risks. For practical application, simulating river flow during extensive rainfall would allow predictions of heavy metal concentrations at discharge and water use points. Our approach would enable the setting of appropriate discharge periods and volumes, even in situations where untreated discharges are unavoidable, contributing to minimize environmental impacts downstream.

The objective of this study was to understand the instantaneous ignition and combustion reactions of CuFeS₂/silica mixture by preheated oxygen gas blowing. The ignition initiation position of CuFeS₂ was controlled by installing a coiled heater inside the reaction tube of the drop furnace, and the ignition and combustion reactions of the CuFeS₂/silica mixture were evaluated by blowing preheated oxygen gas. The sample was mixed at a mass ratio of Fe/SiO₂ = 1.1. The combustive sample was observed by a high-speed camera. The microstructure of reaction products in water-quenched samples was evaluated using scanning electron microscopy-energy dispersive spectroscopy. Based on particle temperature measurements by a two-color temperature method, bright particles observed by ignition and reaction were classified into the following four types: (1) ones with a surface temperature of at ≥2000℃, (2) ones including two different temperature regions of 1600 and 1900℃, (3) ones with a uniform temperature at around 1500°C, and (4) ones at lower temperatures of ≤1300°C. The microstructural analysis revealed that the Cu/S ratio of the matte phase had an average composition of 3.6 near Cu₂S. The ratios of Cu/S and Fe/SiO₂ had no change within experimental errors in all collected particles consisting of slag and matte phases.