Control of metal-containing scale deposition from high temperature brine
AssigneeUnion Oil Company of California
InventorsDarrell L. Gallup, John W. Jost
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Abstract
A method is disclosed for controlling the deposition of metal-containing scales, such as iron silicate scale, from a hot, aqueous, geothermal brine or the like, without substantial corrosion of brine handling equipment. The brine is contacted with (1) an amount of an acid sufficient to reduce the pH of the brine between 0.1 and 0.5 unit and (2) a greater than stoichiometric amount of a reducing agent for reducing trivalent iron and manganese cations in a high temperature brine solution to divalent ions. An overall decrease in scale deposition, especially of iron silicate scale, is achieved while a silver-rich scale can be recovered from silver-containing brines.
Claims21
A method for treating an aqueous geothermal fluid containing scale-forming constituents, said method comprising reducing formation of scale by adding to said fluid a reducing agent and an acid or acid precursor such that the pH of the fluid is reduced by 0.1 to 0.5 pH unit.
A method for inhibiting the precipitation of scale from a hot predominately aqueous geothermal fluid stream containing trivalent iron or manganese cations and further containing scale-forming salts including silicates, said method comprising adding to said stream (1) an amount of a water-soluble acid sufficient to lower the pH of the stream by between about 0.1 and 0.5 pH unit and (2) a greater than stoichiometric amount of a reducing agent for transforming trivalent iron and manganese cations to divalent cations.
A method for inhibiting precipitation of scale upon internal surfaces of liquid handling equipment from a pressurized, hot, predominately aqueous geothermal fluid stream containing trivalent iron or manganese cations and further containing dissolved scale-forming salts, including silicates, said method comprising (A) adding to the stream (1) an amount of a water-soluble acid sufficient to lower the pH of the aqueous stream by between about 0.1 and 0.5 pH unit to form a pH modified stream, and (2) a greater than stoichiometric amount of a reducing agent compatible with said pH modified stream for transforming trivalent iron and manganese cations to divalent cations so as to decrease precipitation of scale-forming salts and to dissolve scale containing said salts previously formed, and (B) subjecting said stream to sudden pressure reduction so that at least a portion of the aqueous stream flashes to produce steam.
A method for inhibiting the precipitation of iron silicate scales from a hot, pressurized stream of geothermal brine containing dissolved iron and silicon components and further containing trivalent iron or manganese cations, said method comprising (A) adding to the brine stream before pressure reduction (1) an amount of a water-soluble acid sufficient to lower the pH of the stream by between about 0.1 and 0.5 pH unit to form a pH modified stream, and (2) a greater than stoichiometric amount of a reducing agent compatible with the pH modified stream for reducing the trivalent cations of iron and manganese contained therein to divalent ions so as to decrease precipitation of iron silicate containing scales and to dissolve any previously formed iron silicate containing scales while inhibiting corrosion to liquid handling equipment that confines and contains the stream, and (B) subjecting said stream to sudden pressure reduction so that at least a portion of the stream flashes to produce steam.
Dependencies are inferred from the claim text.