We had developed new process to treat fly ash generated from municipal incinerators by employing the nonferrous metals refining technology. We clarified the removal mechanism of heavy metals such as lead and cadmium and optimized the conditions based on thermodynamics and metallurgical approaches. We demonstrated by the pilot plant facility with the designed capacity of 100kg/hr that harmful heavy metals like lead are safely removed to trace levels which satisfy the Japanese soil environmental standards. Furthermore, the fly ash treated by this new technology also has passed leaching tests at pH 4 simulating typical acid rain circumstances, so that it can be recycled, for example, as artificial lightweight aggregate. It was also found that volatilized metals collected as secondary ash can be recycled as smelting resources. We could verify at the same time new technology was very conformable as industrial process with developing technologies for materials and equipment. New process will be very useful to fly ash treatment and recycling in the future, as the general technology to treat many types of ashes.

View full abstract

The Japan Oil, Gas and Metals National Corporation (JOGMEC), which is the former Metal Mining Agency of Japan (MMAJ), has developed the deep-sea Boring Machine System (BMS) to detect vertical distributions of hydrothermal deposits and cobalt-rich manganese crusts for better understanding of the occurrence of deep-sea mineral resources.
From 1999, the BMS, a unique cabled remote control submarine multi corer, was installed on the R/V Hakurei-maru No.2 and utilized for the deep-sea mineral exploration. Since then, continuous improvement of the BMS and systematic operation with other survey equipment by the engineers of JOGMEC, Deep Ocean Resources Development Co., Ltd., (DORD) and Ocean Engineering & Development Co., Ltd., (OED) has achieved remarkable progress of submarine exploration technologies, which will contribute to estimate ore reserves of deep-sea minerals deposits as well as to accumulate scientific knowledge.
The role of the BMS will become more important, because it is supposed to be the only one sampling device in the world that can recover in-situ samples, which is indispensable for an effective application of expansion of Japanese continental shelf to the UN.

View full abstract

In order to make realize long-term stability of rock mass, it is necessary to study the time-dependent fracture problem in rocks.
Subcritical crack growth due to stress corrosion is considered to be one of the key factors of the time-dependent behaviors in rocks. It is known that subcritical crack growth is affected by the environmental condition. Thus, it is important to research the dependence of subcritical crack growth in rocks on the environmental condition. Especially, water is known to be a corrosive agent of stress corrosion in rocks.
In this study, Double Torsion (DT) test was carried out by using granite and andesite under various temperature and relative humidity, and the dependence of subcritical crack growth on water vapor pressure was investigated quantitatively.
It was shown that subcritical crack growth in rocks was facilitated as water vapor pressure became large. For andesite, activation energy was estimated from the experimental results, and crack velocities under various temperature and water vapor pressure were calculated. The theoretical values of crack velocity agreed well with observed values.
For granite, considering the dependence of subcritical crack growth on the crack density of pre-existing microcracks as well as the dependence of water vapor pressure, crack velocities were calculated theoretically. The theoretical values were consistent with observed values very well. It is concluded that crack velocity can be predicted by considering the environmental condition and the crack density of pre-existing microcracks.

View full abstract

As a continuation of our study on the recovery of nickel from spent electroless nickel plating baths by solvent extraction, an acceleration of the extraction and stripping by additive addition to the organic phase has been investigated for the 20 vol%LIX84I-Ni(II) system. The vigorous shaking-out test showed that the rates of the extraction from a weakly acidic solution and the stripping with 1 kmol m^-3 sulfuric acid were markedly improved by adding a commercial acidic organophosphorous extractant such as D2EHPA, PC88A, and Cyanex272 in the orders: D2EHPA∼PC88A > Cyanex272 and D2EHPA > PC88A > Cyanex272, respectively. For example, 2 vol%D2EHPA increased the extraction and stripping rates, respectively, by 6.5 and over 30 times in comparison with no additive. This acceleration effect was enhanced by increasing the additive concentration in the range from 0 to 8 vol% although the enhancement becomes slight during stripping when the additive concentration was greater than 2 vol%. At equilibrium, the addition of D2EHPA reversed the selectivity of nickel over iron and zinc with little affecting the nickel distribution at pHs over 4.6. The durability test that repeats the extraction and stripping revealed that the nickel extraction ability of the organic phase containing 20 vol%LIX84I and the 2 vol% acidic organophosphorous extractant did not change during 10 repetitions. Possible roles of the acidic organophosphorous extractants as a phase-transfer catalyst and dispersant were suggested in order to explain the acceleration effect.

View full abstract

Nano-size Y₂O₃ : Eu³⁺ powders were prepared via the thermal decomposition of yttrium carbonate coprecipitate precursors doped with europium. The carbonate precursor, which was synthesized with aging and milling, was fired at 800 °C in air. Consequently, the powder with average diameter of 36 nm was obtained. The relative fluorescence intensity due to the ⁵D₀→⁷F₂ transition of Eu³⁺ in Y₂O₃ sample with average diameter of 36 nm shows about 40% compared with that of commercial Y₂O₃ : Eu³⁺ phosphor with average particle diameter of 3.7 μm. The effect of ball-milling treatment during the aging of carbonate coprecipitated precursor on the preparation of nano-size Y₂O₃ : Eu³⁺ powders was discussed. Also, the effect of average diameter on the fluorescence intensity in nano-size Y₂O₃ : Eu³⁺ phosphor was discussed.

View full abstract

Transparent pyrex glasses were obtained by sintering a green compact, which was fabricated by using CIP method for pyrex glass powder, in diverse atmosphere (air, Ar, He and vacuum (10^-2Pa)) at 973-1173K. Effects of sintering conditions (temperature and atmosphere) on transmittance of sintered glasses were investigated. Devitrification resulting from crystallization of cristobalite arose in all atmosphere at temperatures over 1023K. Optimum sintering condition for fabricating transparent sintered pyrex glass was at 1003 K for 1hour in a vacuum (10^-2 Pa) or He atmosphere in this work. The transparency was 15∼20% in visible region and was about 60% in infrared region. The relationship between transparency and condition of the sintered glasses was discussed in terms of permeation constant of gas species during sintering.

View full abstract

The mercury intrusion porosimetry method covers the determination of the pore volume and the pore size distributions of rock specimen with the range from 7.4μm to 0.0037μm. An apparatus, procedure and calculation are briefly explained and some observations in Shirahama sandstone are definitely introduced. Blank test for rigorous measurement is necessary to evaluate the precise pore distribution in rock specimen, experimental error of data acquisition and low reliability due to a defective dilatometer are reported here. The method which guess the hydraulic conductivity using the obtained pore size distributions and its examples are shown representatively. The calculated and the obtained experimentally hydraulic conductivity of Shirahama sandstone are in good harmony.

View full abstract

It has been clarified that coal seams have a significant ability of CO₂ adsorption more than CH₄ as approximately double based on some experiments reported. By utilizing this property, coal bed methane gas can be replaced with CO₂ injected and produced as a clean energy.
The demonstration project has already has been proceeded in North America, Europe and Japan. In Japan, coal seams, where mining is difficult economically, reserves about 18 billion ton, and it has been estimated that CO₂ sequestration into the coal seams has a potential of about 6 trillion m³ (Koide and Yamazaki⁶⁾).
In this study, measurements of CO₂ adsorption and gas permeabilities of coal specimens have been carried out in order to clarify sensitivities of coal specimen's size on CO₂ adsorption capacity and permeability. Furthermore, adsorption behaviors against saturated CO₂ water have been measured to simulate CO₂ adsorption in a coal seam with high water saturation.
Based on measurement results, it was found that the region of about 10∼15mm in depth from a surface where gas supplied abundantly may work for CO₂ adsorption, because the adsorption capacity of the core specimens show about 1 / 2 to 1 / 3 of ones of crushed samples 4mm in size. On the other hand, the adsorption capacity of 4mm crushed coal in the saturated soda water was around 80% of a coal specimen in dry CO₂ gas.

View full abstract

A large amount of flyash from the coal combustion is produced. About 55% of flyash in Japan is now utilized and the remains are dumped at disposal sites; however, the life of these sites is limited. Therefore, in this study, an effort was made to analyze the lining materials by applying flyash cement as a part of its recycle and utilization. When flyash is added to Portland cement, the same kinds of oxides as those of the cement are added. As an injection component, flyash acts, in part, as a fine aggregate which has similar function to fine debris materials of slake-prone rock and, in part, as a binding component.
From these points of view, in order to clarify to what degree the flyash content affects the properties of the lining materials, some different combinations of flyash, Portland cement and water were considered by means of several laboratory experiments, such as a fluidability test, unconfined compressive test, slaking index test and so on. Also, the utilization of flyash as backfilling materials in the mining engineering fields by means of laboratory testing and a numerical method was applied to analyzing the slake-prone rock slope stability when the mixtures are implemented as lining materials of the embankment.

View full abstract

Inflammable gas concentration monitoring is an important part of centralized monitoring system in coalmine. That assists safety mining operation without gas explosion or gas combustion in deeper gassy coal faces in Japanese coal mines. Experiencing serious inflammable gas related disasters, a lot of efforts had been paid on researches and developments of inflammable gas measurement systems. Considerable financial resources distributed to the installation of inflammable gas measurement system in underground coalmines. However, as Japanese mine safety management system has not employed probabilistic evaluation, the total effect of the measurement system and reliability had not been evaluated before.
Therefore, the question about excess of shortage of safety measure had caused. To derive the answer to the question, the authors investigated inflammable gas measurement system of a Japanese coalmine, and analyzed its reliability, especially in instantaneous failure rates.
The authors developed Fault Tree about gas explosion or combustion accidents in relation with detection failure of inflammable gases. Then, we identified failures of the measurement system using Failure Modes and Effective Analysis format.The authors collected failure frequency rates data by site measurements, interviews about error frequency, and questionnaires about humane errors.
As the result of those surveys and analysis, the authors obtained the following data; yearly drift error value and error rates of automatic inflammable gas alarms (detectors), error rates of the whole automatic methane detection system, human error rates of portable interferometer type methane detectors. Based on the data, the authors calculated the total instantaneous failure rates of whole automatic methane detection system. Then compare the present system with '60th and '80th system and discussed about potential surplus rule and over safety measurement devices installation in mines.

View full abstract

Methane gas (coal mine gas) emitted into the atmosphere due to coal mining is not only a problem for mine safety but also an undesired effect on global warming. Therefore, we will accelerate to diffuse technologies for coal mine gas recovery and its effective use through demonstration project at operating coal mines. The demonstration project for effective recovery and utilization of coal mine gas has been conducted for five years, from fiscal 1998 to 2002, at Tiefa Coal Mining Company, Liaoning Province in P.R.C. The purposes of the project are to prevent global warming, to improve mine safety and to use the coal mine gas effectively as a clean energy resource with its efficient recovery and effective use. The advanced gas drainage and utilization system have been introduced and at the same time the technology transfer has been conducted. Through the project, the coal mine gas has been recovered stably in high concentration and supplied as town gas.

View full abstract