SCRUBBING LINES IN GEOTHERMAL POWER GENERATION SYSTEMS

Abstract

Geothermal steam-water separators are not 100% efficient (Zarrouk and Purnanto, 2015), this result in liquid carry over into the geothermal steam turbines. In addition to the liquid carry over, there will be steam condensates forming inside the pipeline due to loss of heat (thermal power) through the insulated pipeline.
Since low and semi volatile contaminants dissolves in liquid, any water entrainment could cause severe damage to the turbine blades, casing and nozzles reducing turbine’s performance. The combined carry over and the steam condensates is discharged from the steam pipeline using steam traps in the form of drain pot in a process known as scrubbing. If the scrubbing line has enough length, it will allow the carried over droplets to settle down at the bottom of the pipe. In this case nominal design conditions for steam turbines with just below the saturation point with a quality ? 99% can be achieved.
This paper reviews the main parameters that have an impact on the scrubbing line performance including drain pot design. A mathematical model was proposed for setting the pipeline geometry (diameter and length). The mathematical approach is based on the gravity settling theory.
Data from Wairakei field testing are presented in this work as comparison. It shows that that; at an average steam velocity scrubbing line performance decreases as pipeline diameter increases.