Abstract
In the transportation pipe of the hot water at geothermal power station, the silica scale is precipitated as amorphous silica. It is aggregate of the opal ranging 0.05-1.0 μm in size, accompanied by the small amounts of quartz, pyrite, colloform magnetite and others. The chemical compositions of the hot water and chemical and mineralogical properties of the silica scale are studied to clarify the precipitation process of the silica. Also, the experiments of the artificial silica formation from the hot water using autoclave and glass loop were carried out in the laboratory. From these studies the amount of silica scale is independent of the colloidal silica in the hot water. The amount of silica scale has the close relation with the concentration of supersaturated soluble silica in the hot water. The amount of silica scale from the hot solution supersaturated with the soluble silica reaches the maximum at pH 8 in the range of 6-9.
