TURBINE SCALING

Abstract

Scaling, or mineral deposition, in geothermal turbines is an industry-wide problem. It is caused by the superheating of mineralised wet steam as it passes through the turbine nozzles. The superheat conditions result from the normal turbine operating process and cannot be eliminated without significant detrimental effects to performance. The steam supply has a small fraction of water carryover from separator breakdown. This is normally removed by pipeline scrubbing or demisters but these are not totally effective. Low drainpot efficiency exacerbates the problem. A sample of wet steam collected by isokinetic probes is rarely representative of the total impurities. The authors propose a more effective practical standard to assess geothermal steam cleanliness.