Inhibiting Deposition of Siliceous Scale

Lawrence Livermore Laboratory is developing the TOTAL FLOW process for efficient utilization of the thermal energy stored in high temperature-high salinity brines from the Salton Sea Geothermal Field (SSGF) for electric power production. Energy conversion is accomplished by flowing brine through mixed phase expanders and directing the high velocity exhaust jets onto the blades of an impulse turbine. Previous field experience, however, at the Sinclair No. 4 site in the SSGF indicated that deposition of siliceous scale (heavy metal sulfides and iron-rich amorphous silica) in nozzles and on turbine blades would be a serious problem when hypersaline brine is flash evaporated. An experimental program, therefore, was established to develop scale control techniques. Preliminary results indicate that scaling is a pH-dependent process that can be inhibited when brine is acidified with hydrochloric acid.