Acidifiction of steam condensate for incompatibility control during mixing with geothermal brine

A method of combining condensate of geothermally derived steam with a flow of geothermal liquid, comprising water and impurities, the condensate volatile impurities and having a basic pH, whereas the geothermal liquid has an acidic pH, said method comprising the steps of:

• (a) treating the steam condensate to reduce the pH thereof to no more than about 7;
• (b) outgassing the reduced pH steam condensate, to thereby reduce the concentration levels of said volatile impurities which react with impurities in the geothermal liquid to form suspended particulate matter, so as to reduce the formation of said matter when the condensate is combined with the geothermal liquid;
• and,
• (c) combining the outgassed steam condensate with the flow of geothermal liquid.

A method of combining condensate of geothermally derived steam with a flow of geothermal liquid, comprising water and impurities, from which said geothermal steam is extracted, said condensate having impurities including ammonia, hydrogen sulfide and carbonates and having a basic pH, said geothermal liquid having impurities including heavy metals, iron, calcium and silica and having an acid pH, said method comprising the steps of:

• (a) contacting the steam condensate with an acidifying agent so as to reduce the pH of said condensate to a level of between about 7 and about 5.5;
• (b) outgassing the reduced pH condensate to reduce the concentration levels of hydrogen sulfide and carbon dioxide to thereby reduce the amount of suspended particulate matter formed when the condensate is combined with the flow of geothermal liquid by the reacting of ammonia, hydrogen sulfide and carbonates in the condensate with heavy metals, calcium and iron in the geothermal liquid to form heavy metal sulfides, calcium carbonate and iron hydroxide, said ammonia being fixed in said condensate by the reduction of pH therein;
• and,
• (c) combining the outgassed steam condensate with the flow of geothermal liquid in a flash crystallization stage in which steam is extracted from said geothermal liquid and in which said geothermal liquid is contacted with seed material to cause removal of silica from said liquid.

A method of combining condensate of geothermally derived steam with a flow of silica-rich, acidic geothermal brine from which the steam is extracted by flashing the brine, said brine containing impurities in solution, said condensate having impurities carried over from the brine in the flashing process, and having a basic pH, said method comprising the steps of:

• (a) adding an amount of acidifying agent to the flow of condensate causing the pH thereof to be reduced to a level of between about 7 and about the pH level of the geothermal brine with which the condensate is being combined;
• (b) outgassing the reduced pH steam condensate to reduce the level of volatile impurities which react with impurities in the geothermal brine to form suspended particulate matter;
• (c) combining the outgassed steam condensate with the geothermal brine in a flash crystallization stage in which the flow of flashed brine is contacted with seed material onto which silica from the brine is crystallized to form a precipitate;
• and,
• (d) monitoring the size of particles in said precipitate and adjusting the amount of acidifying agent added to the steam condensate so as to maintain the mean size of said particles within a preselected range.

In a facility for producing steam from a flow of silica-rich, naturally pressurized geothermal brine having volatile impurities, including ammonia, hydrogen sulfide and carbon dioxide, and having non-volatile impurities, including heavy metals, iron and calcium, the facility having high and low pressure flash crystallizers in which some of the steam is converted to steam and in which the flashed brine is contacted with seed crystals onto which silica deposits from the brine as the flashed brine becomes supersaturated in silica, having a reactor-clarifier stage in which the deposited silica is separated from the brine, and having a filtering stage for filtering clarified brine discharged from the reactor-clarifier stage, a method for combining with the flashed brine condensate from said steam, the condensate being basic and containing some of said volatile impurities which tend to react with said non-volatile impurities in the flashed brine to form fine, insoluble particles which are difficult to separate from the brine in the reactor-clarifier stage, and which, therefore, flow with the brine into the filtering stage, the method of combining the condensate with the brine comprising:

• (a) reducing the pH of the steam condensate to between about 7 and about 5.5 by contacting the condensate with an acidifying agent;
• (b) permitting the reduced pH steam condensate to outgas so as to reduce the concentration levels of the volatile impurities, especially of hydrogen sulfide and carbon dioxide;
• and,
• (c) combining the reduced pH, outgassed steam condensate with the flashed brine in the low pressure flash crystallizer.