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Developing a Process for Commercial Silica Production from Geothermal Brines.

DE200515013307

Publication Date	2001
Personal Author	Bourcier, W.; Martin, S.; Viani, B.; Bruton, C.
Page Count	16
Abstract	Useful mineral by-products can be produced from geothermal brines. Although silica has many commercial uses, problems remain in producing a marketable product. We are conducting laboratory and modeling studies aimed at optimizing for rubber additive use, the properties of silica precipitates from Salton Sea and Coso-like geothermal fluids, Our goal is to develop a robust technique for producing silicas that have desirable physical and chemical properties for commercial use, while developing a generic understanding of silica precipitation that will allow extraction to be extended to additional fluid types, and to be easily modified to produce new types of marketable silica. Our experiments start with an acidified geothermal fluid similar to those treated by pH modification technology. Silica precipitation is induced by adding base and/or adding Mg or Ca salts to affect the nature of the precipitate. For the analog Salton Sea fluids, adding base alone caused silica to precipitate fairly rapidly. To date, we have characterized precipitates from experiments in which the final pH varied from 4 to 8, where NaOH and Na2C03 were added as bases, and CaClz and MgClz were added as salts. SEM photos of the silica precipitates from the Salton Sea and Cos0 fluids show that the silica particles are clusters of smaller silica particles down to the resolution of the SEM (about 80-100 nm in diameter). The particle sizes and surface areas of silicas from the Salton Sea and Cos0 analog brines are similar to the properties of the Degussa silica commonly used as a rubber additive. An evaluation of the strength of the silica-organic bond as tested by dispersion in oil (polybutadiene) was inconclusive. Neither the Degussa materials nor our laboratory precipitates dispersed readily in nor dispersed down to the fundamental particle size. Preliminary NMR data indicates that the Degussa silica has a smaller degree of silica polymerization (a slightly smaller average number of Si-0 bonds per silica tetrahedron) than the synthetic samples, but a comparable degree of hydrogen bonding of the surface silanol sites.
Keywords	Geothermal power plants Scaling Brines Byproducts Silica Waste product utilization Elastomers Additives Precipitation(Chemistry) pH Calcium carbonates Salts Salton sea geothermal field
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Lawrence Livermore National Lab., CA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200603

Developing a Process for Commercial Silica Production from Geothermal Brines.

Developing a Process for Commercial Silica Production from Geothermal Brines.
DE200515013307

Publication Date	2001
Personal Author	Bourcier, W.; Martin, S.; Viani, B.; Bruton, C.
Page Count	16
Abstract	Useful mineral by-products can be produced from geothermal brines. Although silica has many commercial uses, problems remain in producing a marketable product. We are conducting laboratory and modeling studies aimed at optimizing for rubber additive use, the properties of silica precipitates from Salton Sea and Coso-like geothermal fluids, Our goal is to develop a robust technique for producing silicas that have desirable physical and chemical properties for commercial use, while developing a generic understanding of silica precipitation that will allow extraction to be extended to additional fluid types, and to be easily modified to produce new types of marketable silica. Our experiments start with an acidified geothermal fluid similar to those treated by pH modification technology. Silica precipitation is induced by adding base and/or adding Mg or Ca salts to affect the nature of the precipitate. For the analog Salton Sea fluids, adding base alone caused silica to precipitate fairly rapidly. To date, we have characterized precipitates from experiments in which the final pH varied from 4 to 8, where NaOH and Na2C03 were added as bases, and CaClz and MgClz were added as salts. SEM photos of the silica precipitates from the Salton Sea and Cos0 fluids show that the silica particles are clusters of smaller silica particles down to the resolution of the SEM (about 80-100 nm in diameter). The particle sizes and surface areas of silicas from the Salton Sea and Cos0 analog brines are similar to the properties of the Degussa silica commonly used as a rubber additive. An evaluation of the strength of the silica-organic bond as tested by dispersion in oil (polybutadiene) was inconclusive. Neither the Degussa materials nor our laboratory precipitates dispersed readily in nor dispersed down to the fundamental particle size. Preliminary NMR data indicates that the Degussa silica has a smaller degree of silica polymerization (a slightly smaller average number of Si-0 bonds per silica tetrahedron) than the synthetic samples, but a comparable degree of hydrogen bonding of the surface silanol sites.
Keywords	Geothermal power plants Scaling Brines Byproducts Silica Waste product utilization Elastomers Additives Precipitation(Chemistry) pH Calcium carbonates Salts Salton sea geothermal field
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Lawrence Livermore National Lab., CA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200603