地熱熱水輸送用炭素鋼管に付着するスケール形成過程のモデル化

抄録

 The microstructure of scale adhered to the inner wall of elbow steel pipe, in which the gushing hot spring water was flowed for 3.5 months at a geothermal plant in Obama-cho, Unzen-shi, Nagasaki, Japan, was analyzed. The adhesion substance consisted of four layers, that were amorphous magnesium silicate, aragonite, amorphous magnesium silicate and corrosion product of iron on the carbon steel from top to bottom. The corrosion product fully covered the steel surface. The magnesium silicate with the thickness of 1-2 mm was initially generated as adhesion substance on the corrosion product. The layer thickness of aragonite, orthorhombic calcium carbonate (λ-CaCO₃), was 15-70 mm. The elements of calcium carbonate such as carbon, oxygen and calcium were solved in the magnesium silicate, and the calcium carbonate with massive and/or stratiform was precipitated there. The chemical contents in the magnesium silicate layers on both the top side and the bottom one were the almost the same. Therefore, the precipitation of aragonite and its growth in the magnesium silicate may form the aragonite layer which showed a columnar structure along the heat flux direction.