| Title | Silica Scalie Abatement System on the Uenotai Geothermal Steam Turbine |
|---|---|
| Authors | Kenji Takayama, Naori Komiyama, Yoshinobu Takahashi and Nobuhiko Shakunaga |
| Year | 2000 |
| Conference | World Geothermal Congress |
| Keywords | silica scaling, geothermal turbine |
| Abstract | As suspected from a continuous rise in the turbine inlet pressure, severe silica-rich scaling was found on the turbine nozzles during an inspection conducted after three months from the start of commercial operation. Careful investigation of the scaling mechanism revealed that, as a significant pressure rise occurred in the turbine housing, silica-rich scaling was formed by precipitation through evaporation, flashing and super-saturation of water droplets carried over from the production-well separators. The following systems, therefore, were added on the existing facility to reduce silica scaling. A very encouraging test result was obtained from the ìturbine water injection systemî which was installed immediately upstream of the turbine to de-superheat steam in the turbine chest by intermittently injecting condensate water into the steam line. This system was very successful in reducing the formation of silica scale and in washing out the scale deposits from the turbine nozzles. A ìscrubbing/mist-eliminator systemî was also installed upstream to improve the steam quality before the steam entered the turbine. The mechanism is to purify the steam by continuously injecting condensate water through a venturi tube, and to separate the mist by two separators (mist eliminators). Step-by-step field tests have been conducted to find out the most effective ìturbine water injectionî and ìscrubbing/misteliminationî operation procedure. Currently, a combination of the above systems is satisfactorily working to minimize silica scaling in the turbine. |