Life cycle assessment (LCA) is a methodology for assessing the environmental aspects and potential impacts associated with a product or service during its life cycle. The methodology of LCA is now being standardized as ISO 14040 series. According to ISO 14040, LCA framework consists of 4 elements：1)Goal and Scope definition, 2)Inventory analysis, 3)Impact assessment, 4)Interpretation. First, the goal and scope of an LCA study shall be clearly defined and consistent with the intended application. In inventory analysis, carried out the compilation and quantification of inputs and outputs are for a given product system throughout its life cycle. Impact assessment is a phase aimed at understanding and evaluating the magnitude and significance of the potential environmental impacts of a product system. In interpretation, the findings of either the inventory analysis or the impact assessment, or both, are combined consistent with the defined goal and scope in order to reach conclusions and recommendations. It is recognized that LCA is still at an early stage of development. Some phases of the LCA technique, such as impact assessment, are still in relative infancy. Considerable work remains to be done and practical experience gained in order to develop the level of LCA practice further. The current status and futute tasks on LCA are reviwed in this paper.

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The uncertainty included in metal price is a very serious problem in the metal industry. Under uncertainty, extracting firms must decide when a mine should be developed, when it should be closed, or when its productive capacity should be expanded. Such decisionmakings as development, closure, and capacity expansion depend on the critical prices. For example, a mine should be developed only when the metal price rise up to the critical level. In this paper, we discuss analytical solutions for the critical prices in some cases, and then examine the effects of the lifetime of a mine and the size of uncertainty included in the metal price on the critical prices for development, closure, and capacity expansion. We conclude the results as follows. First, all critical prices are decreasing functions of the lifetime of the mine. Secondly, the critical prices for development and capacity expansion are increasing functions of the size of uncertainty, but the one for closure is a decreasing function of the size of uncertainty.

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It is known qualitatively that spilled heavy oil on the sea becomes highly viscous；however, studies on quantitative determination of the viscosity are scarce. In this paper, results of laboratory test on the viscosity increase of emulsion made by fuel oil C and water were shown with varying volume fraction of water and temperature. The viscosity of the emulsion was higher than that of the initial fuel oil with increasing the fraction of water. The maximum viscosity reached up to about six hundred times compared with the viscosity of the initial heavy oil at a water fraction of 0.75. The emulsion is so stable W/O (water in oil) type that separation of oil from the emulsion is necessary for disposal. Results of several attempts to separate the emulsion showed that heating or applying high shear stress was an effective way. Spreading velocity of fuel oil C on the sea is important information to estimate contaminated area. Measured spreading velocity of an oil droplet on rest water was 3.5 cm/s and the velocity was very sensitive to the contamination of the water surface.

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It is widely accepted in the area of hydrometallurgy that certain microorganisms play a major role in the leaching of base and precious metals from sulfide minerals. Most studies of bioleaching have dealt with the acidophilic mesophilic Thiobacillus species, which grow optimally at around 30 °C and low pH 1 ∼ 2. However, the acidophilic thermophiles, which have temperature optima for activity at 60 ∼ 70 °C, are also candidate microbes for accomplishing metal recovery from mineral resources. Little reports have appeared concerning the bioleaching of sulfides by the thermophilic bacteria at elevated temperatures. This paper describes the bioleaching of high-grade chalcopyrite concentrate (38 ∼ 53 μm) by the acidophilic thermophilic bacterium, Acidianus brierleyi, in a batch stirred reactor. The chalcopyrite leaching was markedly accelerated in the presence of A. brierleyi, and greater than 90 % leaching of copper in the concentrate was achieved at 65 °C within 10 days. However, the chalcopyrite concentrate was scarcely dissolved when the common leaching mesophile, Thiobacillus ferrooxidans, was used at 30 °C. Thus, the thermophile A. brierleyi could solubilize chalcopyrite much faster than the mesophile T. ferrooxidans. The rate of chalcopyrite leaching with A. brierleyi was unaffected by the initial concentration of ferric iron in leach solution, even when the rate of chemical leaching was dependent on the ferric iron concentration. This indicates that the bioleaching of chalcopyrite takes place with a direct microbial attack, the chemical leaching of chalcopyrite by ferric iron being insignificant. Leaching experiments with A. brierleyi were used to examine the dependence of leaching rate on three process parameters, such as solution pH (pH 1.0 ∼ 1.5), temperature (50 ∼ 75 °C), and initial concentrate-liquid loading ratio (2 ∼ 20 kg/m3). The chalcopyrite bioleaching in the batch reactor was carried out most satisfactorily at pH 1.2, 60 ∼ 65 °C, and initial chalcopyrite amount of 20 kg/m3.

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A previous paper described the fundamental reaction conditions for recycling waste polyethylene (PE) into oils. With a reaction temperature of 425 °C, reaction time of 120 min, water fill rate of 30 % and a 1：5 PE/water ratio, PE was effectively converted into light fuel oil with a yield of over 90 wt %. This paper investigates a suitable PE/water ratio, the potential to re-circulate the solvent (water) and the influence of the oxygen gas existing in the reaction system. These are prime issues when putting a waste plastic recycling system into practical use. The possibility of high-speed conversion of PE into oils was also examined in cracking experiments at high temperature over a short period of time. (1)A high yield of oil was produced regardless of the PE/water ratio. (2)Re-use of the water as a solvent showed a slight increase in the yield of the oil products and (3)Oxygen gas existing in the reaction system had no effect on the oil yield. In each case, the quality of the oil products was stable. Oxygenated compounds were not detected in the oil products. At a reaction temperature of 500 °C, light oils with a number-average molecular weight of 147 were produced two minutes. The light oils can be used as fuel corresponding to n-decane on a straight-chain hydrocarbon basis. There was no observed coke production, which indicates the possibility of a high-speed oil conversion process for waste plastic.

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The precipitation stripping phenomena of cobalt oxalate from cobalt-loaded D2EHPA solution were investigated with and without ultrasound irradiation. Morphological variation of precipitated cobalt oxalate was examined with processing factors such as pH value and C2H2O4 concentration under three kinds of mixing modes encountered in crystallization operation ; 1) precipitation synthesis of cobalt oxalate in aqueous solution mixed with an impeller, 2) precipitation stripping from cobalt-loaded organic solution and 3) precipitation stripping from cobalt-loaded organic solution under ultrasound irradiation. The shape of precipitate was rod-like and not significantly influenced by any mixing mode. The size of cobalt oxalate particles obtained without ultrasound irradiation was at most 10μm in major axis. The aspect ratio of rod-like particles, moreover, tended to increase with increasing in H+ and C2H2O4 concentrations in the stripping solutions. Meanwhile, the ultrasound irradiation significantly decreased particle size of cobalt oxalate. It was less than 1μm in major axis, when the [C2H2O4]a concentration was lower. On the other hand, ultrasound irradiation induced fibriform precipitation when the [C2H2O4]a concentration was higher.

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Siliceous nickel ore, raw material of Fe-Ni smelting, is composed of minerals such as garnierite, serpentine, goethite and admixture like quartz, olivine and so on. Ni concentrates in garnierite and serpentine, while Fe does in goethite. Reduction behavior of garnierite, goethite and mixture of both minerals was investigated by X-ray diffraction method to clarify how these minerals react each other to form Fe-Ni alloys as well as slag in the process. The following results were obtained. (1) Nickel recovery from the silicates is very difficult due to less reducibility and poor agglomeration of the metal. (2) When goethite exists with silicates in a reducing atmosphere, FeO in goethite replaces NiO in silicates to form (Fe, Mg)2SiO4 during re-crystallization of the silicates. (3) Molten phase of (Fe, Mg)2SiO4 with low melting point appears in the materials above 1,473 K. It assists the direct reduction of free NiO along with FeO and simultaneously the agglomeration of reduced metals.

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A recovery method of iron component as metallic phase from bauxite residue (red mud) discharged from Bayer process was examined. Tablets prepared with fine mixtures of red mud and carbonaceous materials were heated up to various temperatures to reduce iron oxides in the red mud. The effect of CaCO3 addition was also examined to promote the coalescence/cohesion of formed metallic iron grains. The reduced samples were crushed and then subjected to sieving for the separation of metallic iron bearing particles. When CaCO3 was added, iron yield of more than 90 mass % was attained in the upper size fraction. It was due to formation of large metallic iron particles having size greater than 0.3 mm.

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Fine composite particles containing yttrium and iron were prepared from homogeneous solution using urea as a precipitant generator. The ratio of yttrium to iron in the precipitate could be controlled by adjusting the concentration of the starting materials in the initial solution. These composite particles were considered to be amorphous. Shapes and morphology of the precipitated particles were influenced by the difference of the reaction conditions. Particles obtained from the solution containing 1.88 mmol dm-3 FeCl3 H2O, 3.13 mmol dm-3 YCl3 H2O and 500 mmol dm-3 urea at 97 °C were almost spherical and mono-dispersed. Particles precipitated on the condition as mentioned above converted from amorphous into monophasic garnet (Y3Fe5O12) by calcining at 1,200 °C for 5 hours. After calcination, particle changed its color from brown to medium olive and indicated marked magnetic character.

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An experimental study was carried out on some additive elements for Nd-Fe-B alloy powder produced by reduction-diffusion method (R-D) using metallic Ca as reductant. Pr, Dy, Ni, Co, V, and Mo were selected as additive elements. Pr and Dy replaced Nd in Nd2Fe14B. However, DyFe3 appeared as the Dy content increased. Ni and Co replaced Fe in Nd2Fe14B and Nd rich phase, and improved the corrosion resistance of Nd-Fe-B alloy powder. V and Mo were able to be dispersed in Nd-Fe-B alloy powder by using atomized Fe powder including V or Mo as raw material. The grain growth in the sintered magnet material produced by using Mo-dispersed Nd-Fe-B alloy powder was able to be resisted.

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This paper describes, at first, a bilinear (nonlinear) system in mineral processing. The authors have showed two examples of the bilinear system, one is that of flotation and the other of ore-grinding process. The obtained bilinear concentration regulation system is based on back-mixing model. Then, the authors have studied dynamical characteristics of the bilinear system as a control object. The results are as follows： 1. Nonlinearity (a) In the case of small variance of manipulated variable, the plant can be linearized, but the process gain and the mean residence time depend on equilibrium points. (b) In the case of stepwise change of manipulated variable, the process gain and the mean residence time depend on manipulated variable.

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