地熱発電システムにおける高温好酸微生物バイオリアクターでの硫酸生成

抄録

Silica scale deposition often causes serious problems in geothermal power stations. It has already been well recognized that silica scale deposition can be prevented by keeping the pH of waste geothermal brine acidic. On the other hand, several countries make regulations for mitigation of H₂S emission from geothermal power stations. From these backgrounds, H₂SO₄ production is proposed of using H₂S in the gas exhausted from geothermal power stations. The applicability is then investigated of the usage of thermo-acidophilic bacteria (Sulfolobus sp. Strain 7) for the H₂SO₄ production process for scale prevention. The Hs production experiments are conducted both in bench scale and pilot scale. The experimental results confirmed that the bioreactor with cultured Sulfolobus sp. Strain 7 can produce acidic solution containing H₂SO₄ continuously and the H₂SO₄ production rate of the bioreactor is 0.06 kg·m^-3·h^-1. For practical application of this methods to the Hatchobaru geothermal power station that discharges 1400 m³/h of waste geothermal brine, the following conditions are necessary to keep the pH of the waste brine acidic : 180 m³ of the bioreactor and 252 Nm³/h of the exhaust gas.