Union Oil Company of California

John W Jost

Darrell L Gallup

Mohammad H Ghandehari

William C Lieffers

Olin D Whitescarver

The deposition of metal-containing scale, such as iron silicate scale, from a hot aqueous geothermal brine, or the like, is controlled by blending into the brine sufficient reducing agent effective for reducing trivalent iron and manganese cations in a high temperature brine solution to divalent ions to cause an overall decrease in scale deposition, especially of iron silicate scale. Preferably, from 2 to 7 times the stoichiometric amount of reducing agent is used to effect a 70 to 90 percent reduction in the formation of iron silicate scale.

Use of reducing agents to control scale deposition from high temperature

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.

Recovery of silver-containing scales from aqueous media

A method for inhibiting corrosion of metal in an electrolytic environment comprises electrically interconnecting the metal with an anode consisting essentially of an alloy of aluminum with a rare earth metal or mixture of rare earth metals, optionally also including zinc, and placing the anode into the environment.

Corrosion protection with sacrificial anodes

Control of metal-containing scale deposition from high temperature brine

A method for inhibiting the precipitation of a scale, such as an iron silicate scale, from a hot aqueous brine solution, such as a geothermal brine, during production and handling of the brine wherein there is injected into the brine a brine-soluble acid in an amount sufficient to lower the pH of the brine from 0.1 to 0.3 pH units.

Inhibiting scale precipitation from high temperature brine

A process for stabilizing silica-rich geothermal brine to prevent silica scaling comprises selectively providing a supply of ferric ions, allowing the silica-rich brine to combine with the ferric ions to form insoluble, iron-rich siliceous material and separating the insoluble siliceous material from the brine to form a brine having a silica content which is reduced below the saturation level required for substantially scale-free handling of the brine. In one embodiment of the process in which the brine contains sufficient dissolved ferrous ions, the process comprises selectively contacting the brine with an oxidizing agent, preferably by aerating the brine, to oxidize a selected portion of the ferrous ions to ferric ions, which then combine with silica to form the insoluble iron-rich siliceous material. The ferric ion content of an iron-deficient brine may be augmented by adding ferric and/or ferrous ions to the brine. Steam released by flashing the untreated brine may be used to heat the stabilized brine before disposal thereof, so as to increase the silica solubility and reduce the amount of silica required to be removed to prevent scaling.

Process for stabilizing silica-rich geothermal brine to prevent silica

A method for preventing the deposition of sulfide and/or sulfate scale during the production of a hot two-phase geothermal fluid which contains hydrogen sulfide, barium heavy and/or transition metals, and at least a critical minimum amount of calcium in solution. Gaseous oxygen is injected into the geothermal fluid at a critical rate to selectively oxidize the hydrogen sulfide to intermediate sulfide oxidation products, such as thiosulfates. Thereafter the geothermal fluid is separated into gaseous and liquid phases. Where iron is present in the geothermal fluid, the degree of turbulence induced during the oxidation step is selectively controlled in order to prevent the deposition of iron pyrites.

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Santa Ana, CA, United States of America

John W Jost