Gunung Salak Geothermal Power Plant Experience of Scaling/Deposit: Analysis, Root Cause and Prevention

Abstract

The INDONESIA POWER Gunung Salak Geothermal Power Plant had successfully upgraded their plant in 2005. This upgraded activity was expected to produce an extra 15 MWe of electricity power according to enhancement design calculations. However, problems occurred that resulted in de-rating after the enhancement project.

Based on the root cause analysis, one of the causes of the below optimal behavior was the conveyance of solid particles in the additional geothermal steam. Some of the solid particles were of types commonly observed in geothermal systems, such as silica. In addition to silica, results of laboratory tests showed that there was also a large amount of ferrous iron particles.

Further material testing by SEM and EDS showed that deposition of this material was not caused by turbine blade corrosion. Deposits were found in the shape of layers, and each layer had a different morphology and composition. This finding clearly shows that the turbine was not corroded. Instead, this condition happened as the result of steam-carried particles. The result of an XRD test indicated low scrubber efficiency, which is also indicated by the location of the deposit downstream of the scrubber.

Some preventative measures have been carried out in order to handle the effect of these ferrous iron particles. Monitoring the chloride content, modification of the steam strainer and future installation of a non-oxygenated turbine wash system hopefully will solve the problem of ferrous iron particles.