Language：Japanese   Publisher：THE GEOTHERMAL RESEARCH SOCIETY OF JAPAN  

To prevent the formation of silica scales at the geothermal power plants, a simultaneous precipitation test of silicic acid and aluminum by addition of cethyltrimethylammonium (CTA⁺) bromide (Br^–), which is an organic ammonium salt, was carried out using a sodium silicate solution (400 ppm Si) containing aluminum (5 ppm Al). The concentration of CTA⁺ added was in the range of 10^–6 ～ 10^–3 mol dm^–3. During the polymerization of silicic acid, aluminum combined to polysilicic acid particle. The negative charge density for the polysilicic acid particle with aluminum was higher than that for pure polysilicic acid particle, suggesting that Al³⁺ may be substituted with Si⁴⁺ in the pure polysilicic acid. It was clearly found that silicic acid and aluminum can be simultaneously precipitated from aqueous solution by the electrostatic interaction between CTA⁺ and polysilicic acid particle with aluminum. However, the precipitation of polysilicic acid particle significantly depended on the aging effect (time after the polymerization started) of polysilicic acid particles. In spite of the CTA⁺ concentration, more than 90 % of the aluminum was precipitated even at 10^–6 mol dm^–3.

DOI： 10.11367/grsj.44.147

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Language：Japanese   Publisher：THE GEOTHERMAL RESEARCH SOCIETY OF JAPAN  

To elucidate the effect of polyacrylic acid (PAA) on the formation of silica scales from geothermal water at geothermal power plants, two different experiments were carried out using geothermal water supplied from a production well, TP-2, at the Takigami geothermal power plant in Oita Prefecture, Japan. Polymerization of silicic acid in geothermal water and adsorption of silicic acid and aluminum on the surface of silica gel powder as a model compound of pre-formed silica scale were investigated in the presence and absence of PAA around 90℃. The polymerization of silicic acid which causes changes in monosilicic acid concentration with time and in hydrodynamic size of polysilicic acid particles was not affected by PAA. On the other hand, the adsorption behavior of aluminum was considerably different in cases between the absence and presence of PAA. Only a small amount of aluminum was adsorbed in the absence of PAA, but most of aluminum was adsorbed in the presence of PAA. The amount of silicic acid adsorbed in the presence of PAA was significantly larger than that in the absence of PAA. Consequently, the Al-PAA complex may accelerate the formation of silica scales from geothermal water.

DOI： 10.11367/grsj.39.181

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CiNii Books

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Language：Japanese   Publisher：日本地熱学会  

CiNii Article

CiNii Books

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-23760794/

Language：English   Presentation type：Poster presentation  

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Language：English   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Poster presentation  

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Applicant：AGCエスアイテック株式会社

Application no：特願2018-034997  Date applied：2018.2.28

Announcement no：特開2018-150226  Date announced：2018.9.27

Patent/Registration no：特許第6964017号  Date registered：2021.10.20 

J-GLOBAL

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Applicant：AGCエスアイテック株式会社

Application no：特願2018-034997  Date applied：2018.2.28

Announcement no：特開2018-150226  Date announced：2018.9.27

J-GLOBAL

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