Abstract
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.
