Use of reducing agents to control scale deposition from high temperature brine

Claim 1

A method for treating an aqueous geothermal fluid having a pH between about 5 and about 7 and containing disolved ferric cations and siliceous material which tend to interact to form insoluble, iron-rich silicates, said method comprising adding to said fluid a reducing agent effective for substantally lowering the concentration of said dissolved ferric cations so as to substantially reduce the formation of said insoluble silicates which would otherwise form in the absence of adding the reducing agent while changing the pH of the geothermal fluid by less than about 0.1 pH unit, said reducing agent being selected from the group consisting of carbon monoxide, sodium formate, formaldehyde, starch, dextrose, sucrose, corn syrup, glyoxal, acetaldehyde, butyraldehyde, methanol, ethylene glycol, t-butanol, phenol, hydroquinone, potassium cyanide, urea, urea hydrochloride, formamide, formamide hydrochloride, ascorbic acid, formic acid, oxalic acid, potassium iodide, stannous chloride, iron wire, aluminum, hydrazine hydrochloride, arsenious acid, hydrogen, animal glue, glycine, carbon black, elemental zinc and elemental iron.

Claim 2

A method for treating an aqueous geothermal fluid having a pH between about 5 and about 7 and containing disolved ferric cations and siliceous material which tend to interact to form insoluble, iron-rich silicates, said method comprising adding to said fluid a reducing agent effective for substantally lowering the concentration of said dissolved ferric cations so as to substantially reduce the formation of said insoluble silicates which would otherwise form in the absence of adding the reducing agent while changing the pH of the geothermal fluid by less than about 0.1 pH unit, said reducing agent being selected from the group consisting of carbon monoxide, sodium formate, formaldehyde, starch, dextrose, sucrose, corn syrup, glyoxal, acetaldehyde, butyraldehyde, methanol, ethylene glycol, t-butanol, phenol, hydroquinone, potassium cyanide, urea, urea hydrochloride, formamide, formamide hydrochloride, ascorbic acid, formic acid, oxalic acid, potassium iodide, stannous chloride, iron wire, aluminum, hydrazine hydrochloride, arsenious acid, hydrogen, animal glue, glycine, carbon black, elemental zinc and elemental iron.

Claim 13

The method as defined in claim a wherein the reducing agent comprises dextrose.

Claim 31

A method for treating an aqueous geothermal fluid having a pH of less than about 5 and coantaining disolved ferric cations and siliceous material which tend to interact to form insoluble, iron-rich silicates, said method comprising adding to said aqueous geothermal fluid a reducing agent effective for substantially lowering the concentration of said disolved ferric cations so as to substantially reduce the formation of said insoluble silicates which would otherwise form in the absence of adding the reducing agent while changing the pH of the geothermal fluid by less than about 0.1 pH unit, said reducing agent being selected from the group consisting of stannous cloride, iron wire, aluminum, animal glue, glycine, carbon black, elemental iron and elemental zinc.

Claim 32

A method for treating an aqueous geothermal fluid having a pH of less than about 5 and coantaining disolved ferric cations and siliceous material which tend to interact to form insoluble, iron-rich silicates, said method comprising adding to said aqueous geothermal fluid a reducing agent effective for substantially lowering the concentration of said disolved ferric cations so as to substantially reduce the formation of said insoluble silicates which would otherwise form in the absence of adding the reducing agent while changing the pH of the geothermal fluid by less than about 0.1 pH unit, said reducing agent being selected from the group consisting of stannous cloride, iron wire, aluminum, animal glue, glycine, carbon black, elemental iron and elemental zinc.