A SIMPLE METHOD TO COMPUTE HYDROGEN-CHLORIDE ABATEMENT IN GEOTHERMAL POWER-PLANTS

One of the most important problems affecting geothermal fields is the abatement of hydrogen chloride contained in the vapor phase. If the ch loride concentration exceeds a few ppm(W), steam scrubbing must be pro vided in order to prevent corrosion of the gathering system and turbin e failure. In some fields at Larderello, one of the most important geo thermal areas in Italy, steam scrubbing is performed by injecting a ca ustic solution directly into the steam pipeline. In particular, the ab atement system depends on absorption with chemical reaction of hydroge n chloride by a sodium hydroxide solution. This paper describes some o f the Larderello power plant abatement systems and presents analyses o f the different solutions adopted for this purpose. Finally, some simp lified models for computing abatement efficiency in sprays, pipelines, static mixers, cyclones and vane type demisters-the equipment general ly used in these plants-are proposed. The proposed models are able to predict the data measured in these power plants with good accuracy, an d so they can be regarded as useful tools for designing new abatement systems or optimizing the existing ones.