Silica removal from Mokai, New Zealand, geothermal brine by treatment with lime and a cationic precipitant |
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Authors: | Akira Ueda Koichi Kato Katsumi Mogi Ed Mroczek Ian A Thain |
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Affiliation: | a Central Research Institute, Mitsubishi Materials Corp., 1-297 Kitabukuro, Saitama, Saitama 330-8508, Japan;b Wairakei Research Centre, Institute of Geological and Nuclear Sciences, State Highway 1, Wairakei, Private Bag 2000, Taupo, New Zealand;c Geothermal and Energy, Technical Services Ltd., 19 Cherry Lane, Acacia Bay, Taupo, New Zealand |
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Abstract: | Preliminary experiments using two chemicals (CaO, a quicklime, and a cationic nitrogen-bearing precipitant, EC-004) to remove silica from geothermal brine were undertaken at the Mokai geothermal plant, New Zealand. The brine was mixed with the reagent (CaO or EC-004). The reaction was studied from the start of the experiment (NRT, 0 min, no retaining time) and after 15 min (15RT) at 90 °C. The concentration of silica in the brine was initially 954 mg/l, and decreased linearly with increasing reagent concentration. When CaO is added, the silica concentration at 15RT was 200 mg/l lower than at NRT and became almost zero on addition of 1.5 g/l. In contrast, when EC-004 is added, the total silica concentration nearly reaches the solubility of amorphous silica at 90 °C. In order to prevent silica scaling in Mokai brines cooled to 90 °C, the CaO and EC-004 added should be individually adjusted to 0.5 g/l and 80 mg/l, respectively. |
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Keywords: | Silica Scale Removal CaO Mokai New Zealand |
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