Union Oil Company of California

Manuel E Obando

Darrell L Gallup

Donald M Fenton

Kevin R Kitz

Dennis L Saunders

Brian J Kelly

Paul A Peaden

An integrated system of non-condensable gas (NCG) and condensate treatment allows geothermal power plant condensate and non-condensable gas effluent streams containing H.sub.2 S and ammonia to be commercially useful for more than for cooling tower makeup. In the preferred embodiment, the pH of the condensate is increased by adding ammonia and the pH increased stream is contacted with NCG to scrub and oxidize the H.sub.2 S constituent of the NCG. By reducing the pH, the condensate or aqueous stream mixture can also be used to further transfer ammonia from the non-condensable gas stream to the aqueous stream, enriching the stream for use as a fertilizer/irrigation water mixture. If other commercial uses are desired for the mixture and/or oxidized NCG streams, they can be resin treated to remove the ammonia constituent. With the ammonia and H.sub.2 S constituents decreased, the condensate may be used for a variety of applications and the NCG can be injected or used as a commercial feed stream. Rejuvenation of the resin may be accomplished by recycling and purging with the treated NCG. The effluent purge gas may be used to further enrich irrigation waters. A nearly total elimination of all emissions from the geothermal power is thereby made possible.

Method to treat geothermal fluid streams

Soluble salts are prevented from precipitating from a brine concentrate produced from the flashing a geothermal brine by diluting the brine concentrate with preconditioned condensate. The pH of the condensate is first adjusted to within two pH units of brine concentrate. Then concentration of sulfide ion is reduced by oxidizing sulfide to sulfate by exposure to air for a period of time sufficient to oxidize a substantial portion of the sulfide, but short enough to prevent a substantial concentration of oxygen from dissolving in the condensate. The preconditioned condensate is then mixed with the brine concentrate to form an injection stream. The injection stream is then injected into the earth.

Control of salt precipitation from geothermal brine

In the processing of a geothermal brine and the recovery of heat therefrom, there are produced a non-condensable gas stream containing hydrogen sulfide and carbon dioxide and a liquid stream comprising a condensate of steam derived from the brine. In accordance with the present invention, the noncondensable gases are introduced into the condensate in the presence of an oxidizing agent to form a gas-liquid mixture. The mixture is maintained at an alkaline pH for a time sufficient for a substantial portion of the hydrogen sulfide to be oxidized. Thereafter, the mixture is introduced into a gas-liquid separation zone for separate recovery of a gas stream comprising a major amount of carbon dioxide and substantially free of hydrogen sulfide. Advantageously, the recovered gas stream is recycled to the geothermal brine process to reduce the pH of the brine and its scaling potential.

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Whittier, CA, United States of America

Manuel E Obando