Dissolution of Silica Glass in Supercritical Water and the Influence of Presence of Iron Plate.

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We investigated the dissolution behavier of silica glass under super-critical condition (400-500°C, 40-96 MPa, pure water) to simulate the deep geothermal reservoir. We focused on the dependence of pressure and temperature and presence of iron plate in the system.The results of experiment are as follows: (1) The silica glass dissolved at constant rate. The rate increased with pressure and temperature. Siconcentration was higher at lower temperature in 400-500°C, 60 MPa inverse of the rate. From calculated activation energy, the hydration of glass surface controled this system. (2) In the case of addition the iron plate in the system, the dissolution rate of silica glass increased at 500°C, 40-96 MPa than the case of without iron plate. In surface of iron plate, fayalite and magnetite were produced and Si concentration was same as the case of without iron plate. Therefore, increasing of dissolution rate of silica glass was due to consuming of aqueous silica by production of fayalite.
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