Based on the maintenance data of open pit haulage machines, dump trucks and tire shovels, an optimumoperation planning for these machines was discussed.
Considering the total investment of machine consists of the machine value purchased, overhaul cost andmaintenance cost, Total investment=machine value purchased+overhaul cost+maintenance cost was formulated as the fundamental equation.
Then, the analysis of these costs were performed and simulations were carried out by introducing aninflation effect and D. C. F. concept. And conclusively, optimum replacement time of machine to new machine was decided and abenefit of employment of larger size machines was discussed.

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On the basis of findings by Howard and Essenhigh a newmodel for coal dust explosion propagation was developed to simulate theignition and combustion phenomena of single particles at the early stage of theinitiation of explosion near the lower explosion limitcondition. The ignition energy is given to a particle and ignition occurs by the heterogeneous reaction. It is defined that explosion occurs when the adjacent particles are ignited by the heat from the burningparticle. Thermal ignition theory was used to define the heterogeneous ignition of the adjacen tparticles.
Lower explosion limit concentrations of coal dusts were also measured: Anapparatus used to generate uniform dust clouds was the one developed by Ishihama (Fig.2). That is a tapping sieve Inethod. Results are shown in Fig.3.
Comparison of calculated and experimental results showed very good agreementas shown in Fig4. The adequency of the model was discussed as well.

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This paper deals with the problem of gas drainage by a borehole within a bounded rectangular area under consideration of absorbed methane gas. The gas pressure distribution at dimensionless-time, T, which is calculated by the Finite Element Method, shows the combined pattern of radial flow near the borehole and linear flow in the outer area.
The approximate expression method by use of the gas pressure gradient function C is useful enough for the rectangular area problem like for the circular area problem shown in the first report. That is, the C for the equivalent radius R', defined from the same area with the rectangular area, is adapted in both the case of central borehole and eccentric borehole within a bounded area, and the gas pressure distribution is calculated by eq.(12) and the gas flow rate by eq.(9).

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In the application of the Toms' effect to hydraulic transportation of solids in pipelines, it is a very important problem to evaluate the pressure loss in pipe bends.
In this paper we describe an experimental study of the pressure loss in a vertical pipe bend flow. The fluids used in this test are fresh water, PEO solution, sand-water mixture and sand-water-PEO mixture. The radii of curvature of 90° pipe bend are 70mm and 140mm. The straight pipe connected with these bends has an internal diameter of 25mm.
The results obtained are summarized as follows:(1) The distance, which is necessary before the pressure gradient in downstream of the bend becomes constant, for the mixture flows dissolved PEO was longer than that for the mixture flows not dissolved PEO.
(2) An empirical equation for the bend-loss coefficient of the PEO solutions was obtained as Eq.(6).
(3) The correlations on the additional bend-loss coefficient of the sand-water mixture flows were obtained as Eq.(21) and Eq.(24), and those of the sand-water-PEO mixture flows were obtained as Eq.(23) and Eq.(24).

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The size reduction of waste polymer and composite materials has become an important subject in the field of waste reclamation. And then energy consumptions by size reduction of waste polymers and composite as GFRP are very large.
Therefore, the effect of boiling water corrosion on the decreasing fracture energy for polymer (unsaturated polyester) and GFRP (Glass Fibre Reinforced Plastics) has been investigated experimentally as a fundamental study of industrial pulverizing operation.
The results obtained are as follows:(1) The impact fracture energy for polymer decreased with increasing immersion time in boiling water.
(2) Interlaminar shear strength (ILSS) for GFRP decreased with increasing immersion time in boiling water.
(3) It was found that total fracture energy for GFRP displaied a maximum at a critical value of immersion time (after about 12hr from start).

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Arsenic-containing precipitates obtained from waste water may be redissolved in accordance with their stockpiling condition and therefore, should be stabilized for stockpiling safely without contamination of the environment for a long time. The stabilization of precipitates as calcium arsenate, calcium arsenite and ferric arsenate has been examined. Calcium arsenate precipitate was formed very insoluble Ca₃(AsO₄)₂ by calcining above 700°C without evaporation of arsenic. Calcium arsenite precipitate was changed to very insoluble Ca₃(AsO₄)₂ by calcining in air above 700°C without evaporation of arsenic, too. Ferric arsenate precipitate was formed insoluble ferric arsenate by calcining above 600°C, but decomposed to form valatile arsenic trioxide above 900°C. The precipitate was formed very insoluble one with an increase in the Fe III/As (V) molar ratio in precipitate. Accordingly, it is better for stabilization to maintain the Fe (III)/As (V) molar ratio in precipitate more than 2.
The flowsheet for removing arsenic from waste water with calcium hydroxide was proposed on the basis of our experimental results that arsenic was removed remarkably by adding a large excess of calcium hydroxide to waste water at a level of less than 10mg/l and that calcium arsenate and arsenite were formed very insoluble Ca₃(AsO₄)₂ by calcining in air above 700°C. The flowsheet consists of two steps of nutralization for removing arsenic and calcination for stabilizing precipitates.

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The mechanism on the formation of Zn₂SnO₄ was investigated as a fundamental study for zinc recovery from the reverberatory furnace dust in tin smelting process. The formation of Zn₂SnO₄ from ZnO and SnO₂ was observed at the temperature higher than 1000°C. The formation yield increases rapidly with increasing the reaction temperature. The experimental results indicate that the formation of Zn₂SnO₄ occurs on the surface of SnO₂ with the diffusion of ZnO. The excess SnO₂, therefore, raises the formation yield of Zn₂SnO₄ and excess ZnO does not affect on it. Heat treatment of ZnO and SnO₂ before the formation reaction gives no influence upon the formation yield of Zn₂SnO₄ unless the reaction temperature is lower than the temperature of heat treatment. It is also revealed that the SiO₂ tends to lower the formation yield of Zn₂SnO₄ because it combines with ZnO preferentially.

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Experimental studies have been carried out to clarify the possibility of adsorption removal of malodorant gases such as ammonia, hydrogen sulfide and methylmercaptan from various environments by zeolite tuffs. The test was conducted by the Colomun method using pellets of Clinoptilolite and Mordenite. Various binding agents, i. e. magnesium silicate, sodium silicate, etc., were added for pelletizing the powder zeolite tuffs. The results of the experiments are as follows: The adsorbing capacity of these pellets for malodorant gases depended upon the molecular diameter of these gases. When the malodorant gases adsorbed were ranked according to their quantities, from the largest to the smallest, then their order was 1) ammonia, 2) hydrogen sulfide, 3) methylmercaptan. Mordenite has a larger void diameter than that of Clinoptilolite and showed a higher adsorbing capacity for these gases. The pellets of Mordenite which were added on 2-10% of magnesium silicate showed the highest adsorption capacity for these gases. The compressive strength of the Mordenite pellets became maximum when they were calcined at 200°C-500°C. After malodorant gases were adsorbed, these pellets were perfectly desorbed at 100°C. The experimental results showed that these tests can be applied for practical use. The observed adsorption velocity for malodorant gases by zeolite tuff agreed with Langmuir's equation In V_e/(V_e-V) =ψ·t. It was assumed that the adsorption mechanism in this case was a physical one.

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