| Title | Ohaaki Power Station Cooling Water Chemistry - Predictions and Reality |
|---|---|
| Authors | Eddie Mroczek, Richard Glover and Jenny Webster |
| Year | 1995 |
| Conference | World Geothermal Congress |
| Keywords | power station chemistry, Ohaaki geothermal field |
| Abstract | The principal factors controlling the circuit chemistry in direct contact tower of the Ohaaki gcothermal powcr station had been identified by a comprehensive series of pilot plant studies and theoretical calculations (Dutton and Palmer 1980, Glover 1979). This work provided design recommendations as well as valuable pre-commissioning operation data for the power station. During the commissioning trials in 1989 the chemistry of incoming steam, off-gases, circuit water chemistry as wcll physical parameters such as temperatures and flows were monitored over one day. In this study we report the comparison of these results with the previous predictions. The main finding was that the total dissolved hydrogen sulphide and carbon dioxide in the condenser and the intercooler were undersaturated with respect to the calculated equilibrium concentrations. In the condenscr the measured and concentrations were 52% and 92% of the equilibrium values respectively and and 62% of the intercooler equilibrium concentrations. In the condenser the lower total dissolved concentration was most likely due to the precipitation of sulphur. Oxidation of 60% of the sulphide entering the hotwell could account for the dissolved levels of thiosulphate and The degree of oxidation was higher than previous predictions. |