Chemistry of silica in Cerro Prieto brines

Conference · Fri Feb 01 04:00:00 EST 1980

OSTI ID:5321768

Weres, O; Tsao, L

The precipitation of amorphous silica from synthetic geothermal brines that resemble the flashed brine at Cerro Prieto was studied. It was found that part of the dissolved silica quickly polymerizes to form suspended colloidal silica. The colloidal silica flocculates and settles slowly at unmodified brine pH values near 7.35. Raising the pH of the brine to about 7.8 by adding base and stirring for a few minutes causes rapid and complete flocculation and settling. These results have been confirmed in the field using actual Cerro Prieto brine. Several commercially available flocculating agents were also tested. Both in the laboratory and in the field, it was found quaternary amines to be effective with some brine compositions but not with others. Polyacrylamides do not work at all. These results suggest the following simple preinjection brine treatment process: age the brine for 10 to 20 minutes in a covered holding tank, add 20 to 30 ppm lime (CaO), stir for 5 minutes, and separate the flocculated silica from the brine using a conventional clarifier. The brine coming out of such a process will be almost completely free of suspended solids. The pilot plant tests needed to reduce this conceptual process to practice are discussed. In a separate study, the rate of deposition of silica scale from synthetic brines was researched. It was found that a modest decrease in pH could significantly reduce the scaling rate at a reasonable cost.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5321768
• Report Number(s): LBL-10166(Rev.); CONF-7910166-6(Rev.)
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150302* -- Geothermal Exploration & Exploration Technology-- Geochemical Techniques & Surveys
150903 -- Geothermal Engineering-- Corrosion
Scaling & Materials Development
BRINES
CERRO PRIETO GEOTHERMAL FIELD
CHALCOGENIDES
CHEMICAL COMPOSITION
DEPOSITION
EVAPORATION
FLASHING
FLOCCULATION
FLUIDS
GEOTHERMAL FIELDS
GEOTHERMAL FLUIDS
MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PRECIPITATION
SEPARATION PROCESSES
SILICA
SILICON COMPOUNDS
SILICON OXIDES