EDZ (Excavatin Damaged Zone) may appear around underground repositories. Permeability of rock mass in EDZ would be greater than that of surrounding rock mass and sealability of rock mass would be deteriorated. Countermeasures for the sealability deterioration would induce increase in construction and maintenance costs. However, if sealability recovers with time under pressure, the costs would be reduced. The objective of this study is to clarify whether sealability recovery of clastic rocks exists or not. To accomplish the objective, Kimach sandstone, Toyotomi siliceous mudstone and Inada granite were fractured under triaxial compressive stress state and consolidated in the residual strength state. Hydraulic conductivity increased with failure and decreased by the consolidation to 0.3-0.6 times that just after failure or 0.9-1.5 times that before axial loading for Kimachi sandstone. Similar results were obtained for Toyotomi siliceous mudstone where the ratios were 0.4 and 0.6. Ratios for Inada granite were 0.2 and 16. These results mean that a strong sealability recovery was confirmed for the clastic rocks and a weak sealability recovery for Inada granite.
In order to develop the “Bio-filter”, silicon nitride porous bodies with micro-macro complex pore structure were fabricated using the tape casting process. Since the size of micro-pore must be larger than the one of microbes (about 1 micron) , methods for controlling the pore diameter were investigated. The effect of the mean particle size of the raw alpha-silicon nitride powder and sintering condition on the size of micro-pore of silicon nitride porous body was investigated using various commercial raw powders. The peaks of pore size distributions of all sintered bodies fabricated in this work were much smaller than 1 micron. It was difficult to enlarge the size of micro-pore by extending the sintering duration. To enhance the driving force for grain growth, a small amount of beta-silicon nitride ‘seed’ particles were added to the raw alpha-silicon nitride powders, and sintered at 1850°C for 4∼16h. After sintering for 16h, the peak of pore size distribution reached about 1 micron. Thus, it was confirmed that the ‘seed’ addition was effective to control the size of micro-pore.
Coal is one of the world’s most important resources of energy, generating almost 40% of electricity worldwide. The World consumption of coal can have a significant impact on the environment. Minimizing the negative impacts of human activities-including coal utilization- is a key global priority. Essentials to continue the clean use of coal that is economically efficient and stable supply. It is also important to evaluate non-conventional type resources such as low rank coal and Coal Bed Methane/Coal Mine Methane, to raise an increase of the amount of the resources and the resources recovery rate. The trade volume is less than one billion tonnes though production is about seven billion tonnes a year. This report gives an overview and trends of world’s major coal companies and other leading companies. The structure, consolidation and investment trends of the coal industry including companies from emerging countries were summarized. It was observed that major companies of coal owned mining rights mainly in export markets in Australia and so on. Coal companies from emerging countries eagerly expand their business into these regions, even if the huge infrastructure investment is required. Venture companies also seek to obtain mining rights in speculative areas. Thus, enterprises in emerging countries may increase their share in coal exporting market.
As the global supply-demand balance of petroleum, natural gas and coal is becoming extremely tight due to increasing consumption of these natural resources in Asian and other regions, Japan faces a pressing need to train professionals on resource development in its effort to enhance the country’s energy security. Fewer young professionals have been trained in Japan in the field of resource development because of the aging of the population as well as a result of the ongoing consolidation of university programs and faculties specialized in resource development. At the same time, the industry has started to seek resource professionals with new knowledge and skills, including global perspectives and management expertise. In response, Japan Coal Energy Center (JCOAL) is working to develop a program to train professional human resources for the coal industry for international coal resources development with contents and methods that meet the needs of the industry through the collaboration of industry and university. Furthermore, it will lead to producing resource development professionals and enhancing the energy security of Japan. The Mining Education Program is intended for young people in the workforce and university. Its primary purposes are to provide them with opportunities to acquire knowledge relating to coal resources development and to make a career in coal resources development more attractive. Reflecting these backgrounds, this article provides an overview and summary of the Mining Education Program and the efforts being made to ensure the continuity of the program into the future. The development of mining education program for students in the field of international coal resources development is a project commissioned by the Ministry of Economy, Trade and Industry.
A computer simulation program which calculates chemical equilibrium state of CO, CO2, O2, H2O, H2, CH4 and N2 under arbitral temperature and pressure was made. It shows that CH4 component is large when the temperature is low. On the contrary CO and H2 components are large when the temperature is high. Pressure also gives a certain effect on the gas composition, but it is not so significant compared to the temperature. Then another computer simulation program which calculates the change of the gas components of the flow through the cavity of underground coal gasification (UCG) was made. It shows that the component of the produced gas changes widely according to the thermal condition of UCG cavity. The calculated product gas showed almost same calorific value with the reported calorific value of actual UCG product gas.
We developed a novel two-phase micro flow meter for high-precision unsteady-state measurement of relative permeability, which is one of the most important parameter to forecast the gas injection production processes. The flow meter consists of a small clear tube and several beam sensors that can distinguish gas and liquid. Two-phase mixture coming from a core is led to the tube and separated gas-liquid two-phase flows through the tube. Transit time of a phase through between the two beam sensors can be calculated by cross correlation analyses of signal waveforms outputted from receivers of the beam sensors that were installed beside the tube. Components of the flow meter such as the sensor type, distance between the sensors, and inner diameter of the tube were optimized to improve the flow meter accuracy. The results suggested that the transmissive-type beam sensors should be installed in a distance that the gas/liquid boundary could transit within 2.3 seconds beside the tube whose inner diameter should be the smallest and also larger than the beam diameter. Gas-water relative permeability in water-saturated sandstone cores was measured using both the conventional flow meter and the flow meter developed in this study. Flow meter developed in this study could measure precisely two-phase relative permeability in both a Berea sandstone core and a Kimachi sandstone core whose absolute permeability was high (4.0×10-14 m2) and low (4.0×10-16 m2) respectively while the conventional flow meter could measure that in the Berea sandstone core but the Kimachi sandstone core. These results indicate that the flow meter developed in this study is useful to measure precisely the relative permeability in not only standard sandstone cores but also extremely low permeability cores and the cores including fractures such as coal.
Ventilation measurements were carried out at a shallow underground quarry with relatively large internal volume of 14,600 m3 in order to evaluate its effective ventilation characteristics. From velocity measurements with an ultrasonic anemometer at the exit airway connected to the underground space, the space was ventilated by natural wind flow with direction changes intermittently. It was difficult to measure the ventilation flow with usual method on flow quantity provided from inlet portal, because the space volume was too big and the flow was unsteady to measure flow velocity in the space. In present study, a tracer gas method was applied to evaluate ventilation characteristics of the space. A photo-acoustic gas monitor, that has high sensitivity of 10 ppb resolution for SF6 used as the tracer gas, was set in the space to measure air exchange rate based on the gas concentration-time decay curves. The seasonal change was investigated based on 13 times of measurements during Sept. 30, 1996 to Dec. 21, 1997. Dust concentrations were also measured at the same time in the space. The relationships between ventilation, thermal environment of the space and dust concentration were discussed. It has been analyzed that the reason of seasonal changes in ventilation and dust concentration comes from mainly temperature difference between air of outer atmosphere and internal air or rock surface in the space. Especially, the reason why lower ventilation flow and higher dust concentration generate in summer season was discussed and concluded as that internal air with lower temperature is stable due to its larger density compared with outer atmosphere, then the natural ventilation flow was restrained.
In order to clarify whether we should reduce anthropogenic carbon dioxide emission or not, interaction between 5 potential problems to survival of human, namely, water shortage, food crises, exhaustion of energy and mineral resources, global warming and population increase were investigated. Population increase was the origin of the 5 problems and increase in ODA for women education etc. to accelerate population stabilization was proposed. Unreasonable reduction of carbon dioxide is harmful to human future and should be stopped. Instead, it was suggested not to increase carbon dioxide by accelerating population stabilization and improving efficiency of coal power plants in US, India and China. Prevention of population decrease, increase in self-sufficiency ratio of foods, secure energy and mineral resources, development of such domestic energy resources as underground coal gasification, coal bed methane, deep coal, methane hydrate and sea uranium, and reduction of earthquake damage were proposed as the key points to a better future of Japan.