Developments in geothermal energy in Mexico—part twenty-nine: Scaling studies at the Cerro Prieto geothermal field

Abstract

The high silica content (over 900 p.p.m.) of Cerro Prieto geothermal brine causes problems of scaling at the electric power facility. The scaling tendency is a direct function of the silica saturation ratio. Scaling rates of 1–10 mm per year were experienced at low saturation ratios (SR) < 2 and scaling rates of 100–400 mm per year at (SR) > 3. Pilor plant tests satisfactorily predict scaling rates in commercial equipment. Amorphous silica deposited in process equipment can be dissolved by NaOH, KOH and NH 4HF 2. The use of chemical products to remove scale from well liners is a good method of control. The removal of colloidal silica by using 20–30 p.p.m. of lime has been developed.