Tsutomu Yanagase

The properties of scales and methods to prevent them

Abstract The productive wells of Otake geothermal power plant together produce a total of 400 t/h of hot water mixture. This mixture is transported to the water reservoir of a hydro power plant through an underground pipe line, in order to avoid thermal and chemical pollution of the Kusu river. The rate of deposition was so high that the pipe line was blocked by the deposit, which consists of siliceous matter. The output of the power plant was thus reduced. The chief ingredient of the scale at well No. 6 was calcium carbonate, and so three sectional valves were installed for chemical cleaning of the pipeline, but unfortunately the scales from wells No. 7 to No. 10 were siliceous deposits. Various chemical and mechanical methods of scale removal were tried, but without success. The power production at Otake was restricted from the summer of 1967. Finally the open duct with a cross sectional area of 1.1 m 2 was installed in the middle of September of 1969. Therefore, Otake is now generating 12 MW. To prevent the adhesion of scales to hot water pipeline, physical and chemical analyses of scales (siliceous deposits) and hot water were conducted, and at the same time, there was an attempt to widen the knowledge about scale deposition in hot water under various conditions, using test equipment. After examining the results collectively, the authors have discovered that the deposit of scales is fastest immediately after the spout of hot water, and slows down as time passes. As a preventive measure utilizing this result, a means was invented by which hot water was retained for about an hour and then flowed into the pipeline: for the purpose of this experiment a retaining tank was built. Furthermore, by agitating the hot water flowing into the tank, the effect could be improved. Based on these results, a practical plant was erected to retain all of Otakes hot water for an hour, and satisfactory results have been obtained since its use in September, 1969.

Studies on solid state reactions in a NiOMgOSiO2 system

Abstract The solid-solid reactions among MgO, NiO and SiO 2 have been studied by differential thermal analysis with the aid of X-ray diffraction analysis and infrared absorption spectra as a basic research for the treatment of laterite or garnierite. The main reactions involved in this system are as follows: 1. (1) MgO+SiO 2 →Mg 2 SiO 4 (olivine) and MgSiO 3 (pyroxene) 2. (2) MgO+MgSiO 3 →Mg 2 SiO 4 3. (3) Mg 2 SiO 4 +SiO 2 →MgSiO 3 4. (4) Mg 2 SiO 4 +NiO→(Mg,Ni) 2 SiO 4 (Mg,Ni-olivine) 5. (5) MgSiO 3 +NiO→(Mg,Ni) 2 SiO 4 It was found that the Mg 2 SiO 4 appeared at the beginning of the reaction, followed by the formation of (Mg 1− x Ni x ) 2 SiO 4 through the replacement of MgO with NiO. It may be considered that MgO behaves like a catalyst in the solid phase reactions in the MgO-NiO-SiO 2 system. The activation energy required for diffusion of MgO and NiO in the silicate (Mg,Ni) 2 SiO 4 was determined to be about 42 and 56 kcal./mol, respectively.

Structure and magnetic properties of Fe2O3 based glasses

Abstract BaOFe 2 O 3 binary glasses have been prepared by the splat quenching method. The structural change of the glassy state during the crystallization has been studied by means of Mossbauer spectroscopy and high voltage electron microscopy. The magnetic properties of these crystallized glasses have been measured by the vibrating-sample magnetometer and have been discussed in terms of the particle size of precipitated BaO·6Fe 2 O 3 . The crystallized glass, having 800A of BaO·6Fe 2 O 3 particles, showed the maximum coercive force, that is, 6.2kOe which is three times than that of commercial BaO·6Fe 2 O 3 .