Calcite Scaling Field Experiments to 120?C at Wairakei

Abstract

Preliminary field experiments were undertaken at Wairakei Geothermal Field to measure calcite scaling between 50 and 120?C. The geothermal fluid was saturated with respect to calcite by injecting sodium bicarbonate solutions into the base of a lm long, 50mm diameter fluidized bed reactor. The reactor was filled with 1.5 kg of calcite with a BET specific surface area of 0.0695 m2/g. The experimental technique, with high turbulence, high ratio of volume over surface area, and high supersaturation should have resulted in maximum deposition rates. However, the deposition appeared to be inhibited at lower temperature and thermodynamic calculations overestimated the propensity for scaling.