The seeding method using silica gel particles has been suggested as a prevention method of silica scale. In this study, in order to be effectively utilized the seeding method, the reactor with the silica gel fluidized bed is suggested as the apparatus for the silicic acid removal. The seeding method was applied to a heat exchanger and the results of some preliminary experiments are reported Firstly the height of fluidized bed of the silica gel seeds against the superficial velocity of the liquid was examined experimentally and theoretically. As the results, in the case of using the silica gel seeds as fluidized particles, it is found the appropriate superficial velocity is in the range from 0.05×10-3 to 3.7×10-3m·s-1. Next the experiments on the silicic acid removal were carried out using the sodium silicate solution as a supersaturated silicic acid solution. The removal quantity of silicic acid increased with seed quantity and was in inverse proportion to the superficial velocity of the liquid. The removal ratio of silicic acid was in proportion to the temperature of the effluent but the removal quantity of silicic acid did not be apparently affected by the temperature of the effluent. Therefore it is considered that the prevention of silica scale formation is achieved as the temperature of the effluent is higher. The using the seed quantity per unit of flow rate is possible to be relatively estimated the data on the silicic acid removal in the different seed quantity and superficial velocity.
Fission-track dating method using zircon was performed on three pyroclastic rock specimens of the Torageyama Formation obtained from the N8-AY-2 well drilled in the Akinomiya geothermal area, Northeast Japan. All of the zircons suitable for dating were measured and statistically analyzed in detail, using x2 test, finite mixture model, track length analysis and forward modeling calculation. All of the three samples contained of (20-100 Ma) and slightly old (3-4 Ma) detrital zircons, and essential zircons of 1 Ma. The old detrital zircons should have derived from granitic basements and the slightly old ones from Pliocene igneous rocks. Although the volcanic activity of the Torageyama Formation was previously considered to be 3-6 Ma, the obtained results revealed that it lasted as recently as 1 Ma.
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