Taiheiyo Coal Mining Co.,Ltd. Kushiro Colliery (Taiheiyo Coal Mine) is Located on the southeastern part of Kushiro-city in Hokkaido prefecture, Japan. Taiheiyo Coal Mine, which is an underground coal mine, was established in 1920. The total output of clean coal during its 80 years of operation was more than 100 million tons. Its mining fields gradually expanded into sea beds in the Pacific Ocean from land areas; and since 1951 its entire mining fields have been under the sea bed. Currently, the main fields for mining are areas located 600 to 700 meters under sea level. The production of clean coal in 1998 was 2.13 million tons and R.O.M. was 4.08 million tons.
In order to survive under the several difficult conditions surrounding Japanese coal industry, Taiheiyo Coal Mine makes an effort towards mine safety, stable production and cost reduction. However, mining condition of Taiheiyo Coal Mine is extremely worse than American and Australian ones, so not only longwall techniques but also comprehensive technical development are demanded.
This paper describes the rationalization during these ten years and the productivity increase by comprehensive technical development of Taiheiyo Coal Mine.

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Nippon Mining & Metals has operated a hydrometallurgical process of copper anode slime treatment for two and half years. The process is based on the conception that was proposed by Mr. James E. Hoffmann. Nippon Mining & Metals modefied and advanced some stages of the original one to be suitable for producing precious metals in its acceptable qualities.
The original process treats copper anode slimes fully in aqueous solutions and has the main flow consisted of de-copperizing stage, wet chlorination stage, gold solvent extraction and reduction stages and silver chloride conversion and reduction stages. It also includes de-tellurizing stage and gold extraction raffinate treating stage.
Nippon Mining & Metals examined the original process and improved some stages with its former and recent experiment. The modefied process employs the aeration and the ferric leaching for de-copperizing instead of pressure leaching and pyrometallurgical processing of crude silver from silver chloride reduction with iron instead of silver chloride refining in aqueous solutions. The process is able to recover raw materials of platinum group metals, selenium and telurium, separately. Continuous operation of gold extraction stage is acheived with mixer-settlers and a further refining system for gold loading organic extractent.
The plant of the modefied process started in 1997 and has been succesfuly operated since then. The plant has its capacity of processing 172 t / M of copper anode slimes and producing 2,500 kg / M of gold, 32,000 kg / M of silver, 40 kg / M of platinum and 400 kg / M of palludium.

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We must consider that it is essential matter for every country to solve the global warming problem since maltilateral agreement of COP3. First of all, as the example, this paper focused Japanese steel industries attitude to the reduction of CO₂ emission. Under the CO₂ emission trading mechanism, environment cost is emerging to the market. It means the paradigm sift of material innovation.

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The emanation of radon from rock samples was detected using an imaging plate, which acts as a highly sensitive two-dimensional radiation sensor. Radon alpha-rays, including alpha disintegration of thoron and their daughter nuclides, are measurable using the imaging plate technique.
The semi-quantitative dose of alpha-rays from radon families is evaluated by counting the number of high level PSL spots within a region of interest (for the case of low level dose). The PSL value per unit area is appropriate for a high level dose, where the PSL has unique dose units and quantities in the imaging plate system. The main alpha radiation source for radon families, in the case for a short emanation pathway (i.e. close to the source), is considered to be thoron, but it is inferred to be predominantly radon if applying the imaging plate further from the rock sample.
Modification of this technique allows the two-dimensional measurement of radon alpha-rays emanating from a rock mass, and this may be applied to estimating radon emanation through fractures.

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A soil-recycling machine has been receiving considerable attentions in order to recycle the excavated soils at the construction site. Excavated soils are fed into this machine and they are mixed with the cement or slaked lime. But, the mixing process is very complicated because not only many mechanical factors such as paddle inclination angle, pitch and shaft rotation number, but also physical properties of soils affect the mixing process in the chamber.
In order to design the soil-recycling machine, the effect of these factors on the mixing process has to be fully investigated. However, an experimental investigation requires much cost, and this is not only uneconomical but also ineffective.
In this study, the simulation model to estimate the behavior of soils in the mixing chamber is developed by using Distinct Element Method (DEM) to assist the economical and effective design of the soil-recycling machine. A numerical simulation of the soil behavior was carried out based on this developed model. It was confirmed that the processing volume of the soils showed a maximum at 45 degrees of the paddle inclination angle.

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In order to clarify the reaction mechanism of zeolite synthesis from coal fly ash, zeolite was synthesized by using various alkali solutions. Alkali solutions of single and two component systems of NaOH, Na₂CO₃ and KOH were used for zeolite synthesis. The surface structure of zeolites obtained under various conditions was evaluated, and the role of alkali solution on zeolite synthesis was investigated.
In the case of single component alkali solutions, zeolite P was produced from only NaOH solution under an ordinary synthesis condition (393 K reaction temperature, 3 hrs. reaction time and 2 mol / dm³ alkali concentration). It was confirmed that chabazite was synthesized by extending of reaction time in KOH solution. In the case of two component alkali solutions, zeolite was produced at the particular mixing composition. As the results, it was found that OH^- ion in alkali solution contributed to the dissolution of coal fly ash, and Na⁺ ion contributed to the crystallization of zeolite. Also, it was confirmed that the important factor to fasten the reaction rate of zeolite synthesis was Na⁺ ion in alkali solution. In this study, the reaction mechanism of zeolite synthesis from coal fly ash was clarified.

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The apparent vapour pressure of pure Sb₂S ₃ was measured using the transportation method in the temperature range between 800 and 1,050 °C. The apparent vapour pressures of Sb₂S₃ in the Cu₂S-Sb₂S₃ and FeS-Sb₂S ₃ binary systems were also measured at 1,050 °C using the same method. Activities of Cu₂S and Sb₂S ₃ in the Cu₂S-Sb₂S₃ system at 1,050 °C showed a negative deviation from the ideal behaviour and the activity coefficient at infinite dilution of Sb₂S₃ was estimated to be ϒ^o _Sb2S3 = 0.073. The activity of Sb₂S₃ in the FeS-Sb₂S₃ system at 1,050 °C showed a small negative deviation from the ideal behaviour for X _Sb2S3 higher than 0.36, and constant value of 0.31 for X _Sb2S3 less than 0.36.

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With the purpose of extracting rhenium from molybdenum concentrate, electrolysis of slurry, prepared by mixing molybdenum sulfide concentrate and 10 mass% NaCl aqueous solution, was carried out at 1 A, 313 K. The slurry was continuously circulated into a vertical type 10 stack bipolar electrolytic cell consisted of carbon electrode disks, and the concentrate was dissolved by electrochemically generated oxidizers. The current efficiency for molybdenum dissolution was 73 % after 10 hours electrolysis, and the leach solution was found to contain 0.2 mol / l of molybdenum and 4×10^-5 mol / l rhenium. This result shows the dissolution speed is more than 8 times faster than that obtained using a single cell at applied current of 1 A. Prior to rhenium separation from the leach solution, preliminary experiments for rhenium extraction by MEK (Methyl-ethyl-keton) were carried out using synthesized test solutions having similar composition. The behavior of molybdenum, rhenium, and sulfur was investigated for examining the extraction conditions and efficiency. The leach solution obtained by electro-oxidation was then subjected to a solvent extraction experiment, and rhenium present at several tens of mass ppm in the concentrate was enriched to more than 1,000 times, and recovered as sulfides. After rhenium separation, molybdenum was recovered by precipitation after changing pH of the solution.

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Thermal properties of AgNO₃, Ni(NO₃) ₂ 6H₂O and the mixed nitrates of Ag and Ni were investigated by using thermogravimetric analysis and differential thermal analysis. The composite powders of Ag-NiO were prepared from the nitrate solutions by spray pyrolysis. The spray pyrolysis experiments were carried out to prepare the composite powders with 90~10 % Ag-NiO composition, which was a useful material in electronic industry.
In thermal analysis of the mixed nitrates of AgNO₃ and Ni(NO₃)₂ 6H₂O, the melting point and the beginning temperature of the thermal decomposition were found to be lower than those temperatures of AgNO₃. When the reaction temperature in the spray pyrolysis was above 1,223 K, the produced composite powders became spherical particle with mean diameter of about 2 microns, while the products with rough surface were obtained at a lower reaction temperature. The products with different particle diameter could be prepared by spray pyrolysis under different spraying conditions. The composite powders became finer with an increase in temperature and with a decrease in Ag concentration.

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The electronic structure of BaTiS₃ was investigated using a discrete-variational Xα (DV-X α) method on the model cluster. In the calculation of [Ba₆Ti₃S₄₈]^72- cluster, the band gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) was 0.98 eV, which was much smaller than that of ionic crystal, BaTiO₃. In the valence band region, S 3p orbitals hybridized with Ti 3d orbitals, while not with atomic orbitals of Ba atom. Net charges calculated for the [Ba₆Ti₃S₄₈]^72- cluster were + 1.911 for Ba, + 0.750 for Ti and -0.682 for S, respectively. Furthermore, the bond overlap population of Ti-S bond was very large, compared with the Ti-Ti and Ba-S bonds. These results indicate that the covalent interaction between Ti and S atoms plays a dominant role on chemical bond of BaTiS₃ crystal.

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