Return carbon dioxide to flashed geothermal brine to control scale deposition in a geothermal power plant

Abstract

Geothermal brine always contains some carbon dioxide in solution. Separating steam from geothermal brine removes the carbon dioxide, sharply increasing the pH of the brine and causing precipitation of pH sensitive minerals, including calcium carbonate, magnesium silicate and other metal silicates, clays, and metal sulfides. The binary heat exchanger in a steam-binary hybrid geothermal power plant is especially sensitive to scale deposition from flashed geothermal brine, and application of expensive scale inhibitors is required. Deposition of scale in the binary heat exchanger can be controlled by separating a small amount of gas-rich vapor from the brine before the main stage of steam separation, and combining this gas rich vapor with the flashed brine before in enters the binary heat exchanger. The carbon dioxide thus added to the brine will decrease pH, decreasing or completely blocking precipitation and deposition of pH sensitive minerals as scale.