Most serious problem concerning municipal waste is the limitation of final disposal site. Even though recycling is one of the most important countermeasures, it is very difficult to promote it mainly for economical reasons. The purpose of this research is to propose the model evaluating the effect of recycling, both on the reduction of final waste and the domestic economy, and to show a guideline for the optimum allocation of municipal waste recycling among industries under some selection criteria. The effects of recycling were calculated by a newly developed simulation model, which was consisted of characteristic sub-models and based on the Input-Output table analysis evaluating the repercussion effects of recycling costs and the distribution of material. A recycling cost function and a domestic consumer demand function for several sectors are also estimated. Following criteria were introduced to allocate the additional amount of recycling among sectors : (1) Minimize the GDP decrease per unit of reduced final waste (2) Minimize total GDP decrease (3) Maximize the reduction of final waste Adopting Criterion (2), the model indicates that recycling allocation should be started from the industries whose repercussion effects on the domestic economy are relatively low. Under criterion (3), recycling should be promoted firstly by the industries whose products mainly consist of materials with high ash content ratio. The result of simulation under criterion (1) is more efficient than the other criteria in terms of cost effect.

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It is anticipated that the dynamical responses to changes of air supply and solid supply become more complicated in an air-lift pump for lifting deep-sea mineral resources. Then it is inevitable to grasp unsteady flow characteristics in air-lift pumps for safety operations of the systems. Therefore, the purpose of this study is to obtain safety operational conditions for air-lift pumps of lifting marine mineral resources such as manganese nodules from deep-sea floor to a mining ship. The numerical method was applied to an air-lift pump of 5, 000 m depth. In this paper, we discuss the unsteady flow characteristics of gas-liquid-solid three-phase flow in beginning and stopping of solid supply, in increasing and reducing of back-pressure, in fluctuating of solid supply, and reducing and returning of air supply from the viewpoint of practical techniques.

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This report presents findings on the enhanced removal of heavy metals (As, Se, Cd, Cr, Pb and Hg) from high sulfur coal by the flotation, which was conducted with bacteria to reject metals coexisting with pyrite. Pittsburgh, Tenfu and Heisaku coal were divided into five specific gravity fractions using heavy liquid separation, then analyzed. The low-gravity fractions (<1.4) contained large amount of organic matter and little heavy metals. The metals were mainly found in the high-gravity fractions (>3.0) containing large amounts of pyrite. A clear relationship was observed between pyrite contents and the amount of heavy metals in all fractions (Correlation coefficient : r> 0.96), while the relationship between ash content and the amount of heavy metals was not as clear (r = 0.47 ～ 0.86). Heavy metals were distributed with pyrite, but not with ash. This result shows that for the removal of heavy metals from coal, the separation of pyrite from organic matters is important. In order to enhance the pyrite removal from coal, bacterial treatment was applied to coal flotation to reduce heavy metal contents in froth. By the addition of bacteria to the flotation, the pyrite rejection of Pittsburgh, Tenfu and Heisaku coal increased from 11.8 (without bacteria) to 48.9% (with bacteria), from 36.2 to 61.2%, and from 55.5 to 64.0%, respectively. Under these conditions, the rejection of each heavy metal, except mercury, from all coals increased from 12.9 ～ 69.1% to 31.1 ～ 84.2%. These results clearly show that the use of bacteria could enhance the removal of heavy metals from coal in flotation as result of an increase in pyrite removal.

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Zeolites have been synthesized through hydrothermal reaction of coal fly ash with alkaline solutions in order to facilitate effective use of the fly ash generated from the coal power stations. The properties of synthesized zeolite were examined by X-ray diffraction, and characterized by cation exchange capacity (CEC) and specific surface area. Each of NaOH solution or Na₂CO₃ solution was applied to test the effects of alkali type on hydrothermal reaction. The reaction conditions established in the present work ware the ratio of solid and liquid, 1 : 4 and reaction temperature, 393 K for the favored synthesis of zeolite in only few hours without any pretreatment. Only zeolite P was synthesized when 0.5 ～ 3.0 mol/dm³ NaOH was used, whereas both zeolite P and hydroxysodalite were produced in the case of NaOH solution of 4.0 mol/dm³. CEC value of 350 meq/100 g of the zeolite P synthesized with 2.0 mol/dm³ NaOH was sufficient for a cation exchanger. SEM photographs showed the growth of zeolite on the surface of the undissolved fly ash, resulting texture of amorphous fly ash covered with the crystallized zeolite. Sodium carbonate solution of 1.0 mol/dm³ alone failed the synthesis reaction of zeolite, whereas addition of more than 15% of NaOH proceeded the reaction. The thickness of zeolite layer depended on the amount of NaOH.

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The reduction-diffusion process using Ca as reducing agent has been practiced industrially in the production of the SmCo₅ type, the Nd-Fe-B type and the Td-Fe-Co type magnetic materials. The advantages of the R-D process are the generally high yield of rare earth metals and the single-stage conversion of mixture of oxides and metal powders into a product of rare earth alloy powders. On the other hand, its disadvantages are the slightly high contents of O and Ca. These disadvantages are remarkable in the Nd-Fe-B type. An experimental study was carried out on oxygen and calcium reduction technique for Nd-Fe-B alloy powders produced by reduction-diffusion method using metallic Ca as reductant. One technique is to dope Co or Ni into the raw powders, and another is to reduce Nd content from the atomic ratio of Nd₁₅Fe₇₇B₈. These alloy powders are suitable for the production of Nd-Fe-B sintered magnets and are expected higher magnetic properties.

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Synthesis of precursor fine particle of Eu³⁺-doped yttrium oxide phosphor (Y₂O₃ : Eu) from homogeneous solution using urea as a precipitant generator with and without addition of nucleus fine particle and effect of solution temperature for the size and shape of precipitated particle was investigated. Particle size and shape were influenced by the solution temperature on precipitation reaction. The average size of spherical particle changed from 280 nm with decreasing in solution temperature from 77°C to 97°C on nucleation stage of precipitation reaction. At the low temperature of 74～84°C, non-spherical (plate-like) particle was precipitate with spherical particle, while spherical particle was only precipitated at the high temperature of 97°C. By adjusting an addition of fine colloidal particle to a stock solution as nucleus of the precipitation, it is possible to control the number and size of the final products. The average size of spherical particle changed from 523 nm to 968 nm with decreasing in quantity of nucleus particle.

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The fractal distribution of the logitudinal primary surface cracks has shown the presence of secondary growth which yields longer cracks. To illustrate the secondary growth, a model which consists of two processes is considered ; one is the foregoing probability process for generation of the crack growth, and the subsequent growth process concerning the degree of growth : δ.Variations in distribution and integral functions and also in interval and cumulative frequencies for the secondary cracks and the residual primary cracks is given as a function of the dimensionless length, the ratio of crack length : L to the critical length : L_c at which the probability is assumed to be 1. Three data sets were analysed and calculated distributions for the grown secondary cracks and the residual primary cracks were in good accordance with those expected from the model. The correlation between L_c and δ suggested that there were two types of the growth process. One type showed the product of L_c and δ being constant in the range L = 1 to 2 m ; this type included data of the lower face of two slabs. The other showed δ being constant at about 2, regardless of L_c ; this type included data of the upper face.

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Coal provides the mainstay of alternative energy sources replacing oil, because of its great supply stability and economic advantages Japan depends on coal for 16% of its primary energy supply. In the Asian region, coal accounts for 45% of primary energy, which is considerably higher than the world average of 30%. Coal is an essential energy source for the sustainable economic development of the Asian region. To ensure stable supply of coal for Japan, it is necessary to increase supply of coal to respond to the increase in demand for coal, mainly in the Asia-Pacific region. To respond to the need to ensure stable supply of coal and the environmental problems such as the global warming issue, expectation is placed on Japan to effectively employ its advanced coal-related technologies. In August this year, the Coal Mining Council which is an advisory committee for the Minister of the Ministry of International Trade and Industry, made the final report “Suggested Ways of Completing the Present Japanese Coal Policy Smoothly”. The report pointed out that the global coal supply and demand situation is expected to become more strained in the future, and that Japan is the world's largest coal importer, accounting for nearly 30% of the total global coal trade. Because of this particular status of our country, securing stable supply of coal on an international scale still remains one of the top priorities for Japan to undertake, and that the domestic coal mines have an important role to transfer their advanced coal mining technologies to coal producing countries such as China and Indonesia, in order to secure stable supply of coal. This paper describes the outline of the report of the Coal Mining Council and reviews the future direction of Japan's Coal Policy from a viewpoint of energy policy based on the current situation and future global energy supply and demand.

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Recently, coal demand in Japan has been consistently on the increase. Coal is ranked as the core alternative energy source to oil. Therefore, we should positively address the problems of maintaining a stable supply and overcoming the environmental issues caused by coal use. Our attention also should be drawn to the fact that only the disadvantages of coal use are emphasized and that the future prospect for the coal situation is too optimistic based on the current oversupply Nothing is more uncertain and unstable than energy supply and demand, and coal is no exception. Energy issues also constantly need to be viewed from the standpoint of security. In view of the energy-supply structure peculiar to Japan where most of its energy sources depend on supply from abroad, our international contribution is essential. Summarizing today's coal-related problems, it is obvious that a stable coal supply and environmental preservation are indispensable. To solve these problems, development of triangular relationship mutually-linking source (supply), utilization (demand) and anti-pollution, should be sought. Our organization, Japan Coal Energy Center (JCOAL), is open to both domestic and international parties interested in coal-related issues. We wish to become a world-wide coal center by making efforts to provide substantial information on coal resources and by playing central role in the coal-related industry by acting as a go-between for parties concerned both in Japan and abroad.

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Embalut Coal Mine is located in the north of Samarinda City, East Kalimantan, Indonesia. The mine started coal production in 1983. Coal production consists of U/G and O/P. 5 longwall panels are working in 3 underground pits, and coal is transported to the surface using mine cars by winders, then is carried about 6 km by dump trucks to the washing plant whichi is located at the east riverside of Mahakam River. An adequate quality coal for market is made by mixing the high caloric coal from U/Gwith low caloric coal from O/C at the washing plant. Clean coal is shipped to barges (2, 500～8, 000) by the loading facility (500 tons/hr), coal for domestic users is derectly carried to destination by barge and coal for export istransshipped to adepot ship on the opensea or Balikpapan Coal Terminal. Mitsui Mining Engineering Co., Ltd., had dispatced 3 engineers as mine managers and 4 engineers as vice mine managers from 1990 to 1997, and after that Indonesian mine manager has been engaged in. The improvements of the mine furing our stay in the mine were made by as follows; (1) introduction of retreat longwall mining system using hydraulic props & link bars, (2) introduction of endlesse wired transportation system at a each level road. At some extraction panels where wood have to be used, room & pillar system shich was using a traditional wooden props was replaced by a longwall system using combination of relatively strong and weak wooden chock at the early stage, but finally all the panels were improved to hydraulic props & link bars system. Furthermore, for the purpose of smooth mine car transpotation, the road maintenance system was improved. The results of those improvements of the mine, mining recovery ratio increased drastically, and the double level of U/G production has been reached compared with the period before under control of Mitui Mining Engineering

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Ikeshima coal preparation plant was started operation from 1959. This plant has been conducting many renovations of equipment for 40 years to fit the various demands and changes of markets and also to correspond a number of legal controls. This time, we report about 3 construction work in recent years. At first, in order to increase the capacity and obtain higher accuracy of separation, the main Baum jig (capacity : 300 t/h) has been converted into a VARI=WAVE jig, which has been developed to create a desired wave pattern of pulsation. Secondly, we introduced the Filter Press in order to recover the low grade of fine coal. Finally, we renewed the dust collector because of the handling of the dust which was influenced by the increase moisture content in raw coal.

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It is important to obtain information about geostructure of roof rock for effective rock bolting at the roadway in underground coal mine. Information on the variation in rock types and the distribution of discontinuities, such as layer boundaries, separation of strata and cracks, is especially important. For in situ evaluation of roof rock, we developed a measurement-while-drilling (MWD) system using mechanical data obtained from a drilling machine. The hardware of this system detects the torque, thrust, revolution and stroke of the machine as the mechanical data, and the software analyzes the mechanical data log and displays the locations of discontinuities by Neural Network techniques. This system also enables estimation of the 3-D geostructure of roof rock with regard to the change in rock types and distribution of discontinuities in the case of an array arrangement of drill holes. For displaying images inside the 3-D geostructure, animation consisted of slicing images and/or a 3-D model describing the boundary plane of layers by VRML(virtual reality modeling language) in virtual space are employed. We conducted some feasibility studies of this system using a pneumatic and a hydraulic drilling machine in roadways of Taiheiyo Coal Mine, Japan. The results of feasibility studies confirmed that the 3-D geostructure, including the distribution of crack density, can be reconstructed by the analysis system. Animation and display by VRML for the 3-D geostructure were useful for understanding inner structure of rocks.

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