Corrosion and Scaling Deposits in the BerlÌn Geothermal Field

Abstract

A complete analysis of the solid materials found in the surface equipment in the Berlin Geothermal Field is undertaken during the shutdown of the power plant. Samples are collected from these equipment to evaluate the deposition process in order to minimize and prevent its deposition.

Results of analysis in September 2003 shutdown showed that a) cyclone separators contain mostly rock fragments from Unit IV formation, b) water tank with rock fragments and scaling deposits mostly amorphous silica, c) valves (ball and bypass valves) with scaling deposits (silica and halite) and few corrosion products d) steam pipeline with corrosion products (mostly magnetite, hematite and goethite) e) water pipeline with scaling deposits (amorphous silica and calcite) and corrosion products, f) two-phase pipeline with both corrosion and scaling products, g) water pump for the condenser with sulfur and h) turbine blades with few corrosion products mostly magnetite.

Corrosion in BerlÌn geothermal field is influenced mainly by the condensate, presence of abundant O2 and H2S, and solid particles.

An attempt to construct a Pourbaix diagram (Fe/S/H2O system with the pH and Eh values) was undertaken at a temperature of 170?C. Deposits in the separator system and pipelines are found in the area of magnetite, few hematite, pyrite and pyrrhotite.