Union Oil Company of California

Jessie P Reverente

John L Featherstone

Darrell L Gallup

Philip H Messer

Allen W Doty

Morton M Wong

Charles F Wong

Gregory A Gritters

Geothermal brine is passed through a zone containing a packing metal so as to reduce its tendency to deposit iron/silica scale, reduce corrosivity of the brine, and/or remove and recover metals from the brine. The method polishes the geothermal brine by contacting the brine with a packing metal higher in the electromotive series than silver for a time sufficient for a precious metals to precipitate onto the packing at brine temperature and pH conditions which inhibit iron-rich silica scale. Most preferably, the contacting is accomplished near an injection well at the end of a heat extraction process and the packing comprises coiled zinc-galvanized steel chicken wire mesh packed in a sufficient density to also act as a filter for suspended particles. Alternatively, contacting is also accomplished near the production well. Dissolving the packing in a suitable acid leaves a precious metal-rich residue behind for subsequent recovery. When the brine is treated in accordance with this method, the useful life of injection wells used to return cooled brine back to the geothermal field is extended by at least about 3 time as compared to that observed with untreated brine. Further the contacted brine is less corrosive than it was before contacting.

Brine treatment

Geothermal brine is passed through a zone containing a packing metal so as to reduce its tendency to deposit iron/silica scale, reduce corrosivity of the brine, and/or remove and recover metals from the brine. The method polished the geothermal brine by contacting the brine with a packing metal higher in the electromotive series than silver for a time sufficient for a precious metals to precipitate onto the packing at brine temperature and pH conditions which inhibit iron-rich silica scale. Most preferably, the contacting is accomplished near an injection well at the end of a heat extraction process and the packing comprises coiled zinc-galvanized steel chicken wire mesh packed in a sufficient density to also act as a filter for suspended particles. Alternatively, contacting is also accomplished near the production well. Dissolving the packing in a suitable acid leaves a precious metal-rich residue behind for subsequent recovery. When the brine is treated in accordance with this method, the useful life of injection wells used to return cooled brine back to the geothermal field is extended by at least about 3 time as compared to that observed with untreated brine. Further the contacted brine is less corrosive than it was before contacting.

A method is disclosed for polishing geothermal brines containing iron-rich silica scale and silica particles suspended therein while removing and recovering copper, silver and other precious metals dissolved therein. The method comprises passing brine having a pH just below about 5.0 through a conduit packed with a metal higher in the electromotive series than silver for a time sufficient for a substantial portion of the copper and silver therein to precipitate onto the packing. Preferably, the packing comprises coiled zinc-galvanized steel chicken wire mesh packed in a sufficient density to act as a filter for said suspended particles. Dissolving the packing in a suitable acid will leave a precious metal-rich residue behind for subsequent recovery. When the brine is treated in accordance with this method, the useful life of injection wells used to return cooled brine back to the geothermal field is extended by at least about 3 time as compared to that observed with untreated brine. Further the treated brine is less corrosive than it was before treatment.

Treatment of brine

A method is disclosed for polishing geothermal brines containing iron-rich silica scale and silica particles suspended therein while removing and recovering copper, silver and other precious metals dissolved therein. The method comprises passing brine having a pH just below about 5.0 through a conduit packed with a metal higher in the electromotive series than silver for a time to sufficient for substantially all of the silver and other precious metals therein to precipitate onto the packing. Preferably, the packing comprises coiled zinc-galvanized steel chicken wire mesh packed in a sufficient density to act as a filter for said suspended particles. Dissolving the packing in a suitable acid will leave a precious metal-rich residue behind for subsequent recovery. When the brine is treated this process, the useful life of injection wells used to return cooled brine back to the geothrmal field is extended by at least about 3 times as compared to that observed with untreated brine.

Recovery of precious metals from aqueous media

A process for treating hot, pressurized geothermal brine in a liquid-vapor phase separator comprises contacting the brine in the separator with between about 0.2 and about 1.5 parts per million of a defoaming agent so as to substantially reduce the amount of foaming in the separator caused, in part, by steam bubbling through the brine. The preferred defoaming agents are polyglycols having molecular weights between about 1000 and about 2500, those agents having molecular weights below about 1000 being too volatile and those above about 2500 being too difficult to solubilize in the brine. If the separator comprises a draft tube-type flash crystallizer in which silica-rich geothermal brine is contacted with a seed material onto which silica from the brine deposits, the process additionally includes establishing and maintaining a brine level in the crystallizer causing circulation of the brine at a rate substantially reducing the rate of silicious scaling of inner walls of the crystallizer which would result in the absence of brine circulation, the established and maintained brine level being such that in the absence of the defoaming agent, excessive amounts of brine in the form of foam would be carried over into steam discharged from the crystallizer. In preexisting separators in which a design steam production rate cannot be attained because of brine foaming, the addition of a defoaming agent by the present process may enable steam production at a rate greater than the design rate.

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El Centro, CA, United States of America

Jessie P Reverente