Method of producing mechanical energy from geothermal brine

Claim 1

A method for producing mechanical energy from geothermal brine, with comprises: producing hot geothermal brine from a subterranean geothermal reservoir; contacting said brine with a heat transfer fluid having a higher vapor pressure than said brine at the temperatures encountered; passing said heat transfer fluid and said brine cocurrently through a series of separate flash stages, wherein each successive stage is maintained at a lower pressure less than the vapor pressure of the fluids entering the stage so that at least a portion of the heat transfer fluid is flashed to vapor in each stage; countercurrently flowing a working fluid successively through said series of flash stages in indirect heat exchange with the vapor produced in each flash stage, whereby the vapor is condensed in each stage and said working fluid is progressively heated as it passes through said series of flash stages; and utilizing said working fluid in a heat engine to produce mechanical energy.

Claim 2

A method for producing mechanical energy from geothermal brine, with comprises: producing hot geothermal brine from a subterranean geothermal reservoir; contacting said brine with a heat transfer fluid having a higher vapor pressure than said brine at the temperatures encountered; passing said heat transfer fluid and said brine cocurrently through a series of separate flash stages, wherein each successive stage is maintained at a lower pressure less than the vapor pressure of the fluids entering the stage so that at least a portion of the heat transfer fluid is flashed to vapor in each stage; countercurrently flowing a working fluid successively through said series of flash stages in indirect heat exchange with the vapor produced in each flash stage, whereby the vapor is condensed in each stage and said working fluid is progressively heated as it passes through said series of flash stages; and utilizing said working fluid in a heat engine to produce mechanical energy.

Claim 16

A method for producing mechanical energy from geothermal brine, which comprises: producing hot geothermal brine from a subterranean geothermal reservoir; initially contacting said brine with a heat transfer fluid having a higher vapor pressure than said brine at the temperatures encountered and being substantially immiscible with said brine; passing said heat transfer fluid and said brine cocurrently through a series of separate flash stages, wherein each successive stage is maintained at a lower pressure less than the vapor pressure of the fluids entering the stage so that at least a portion of the heat transfer fluid is flashed to vapor in each stage; countercurrently flowing a working fluid successively through said series of flash stages in indirect heat exchange with the vapors produced in each flash stage, whereby the vapor is condensed in each stage and said working fluid is progressively heated as it passes through said series of stages; collecting the condensate produced in each stage to prevent the mixing of said condensate with said brine in the same stage; contacting said condensate from each stage with the brine entering the subsequent stage; utilizing said working fluid in a heat engine to produce mechanical energy; and recycling the heat transfer fluid from the last stage of said series of flash stages to said initial contacting step.

Claim 17

A method for producing mechanical energy from geothermal brine, which comprises: producing hot geothermal brine from a subterranean geothermal reservoir; initially contacting said brine with a heat transfer fluid having a higher vapor pressure than said brine at the temperatures encountered and being substantially immiscible with said brine; passing said heat transfer fluid and said brine cocurrently through a series of separate flash stages, wherein each successive stage is maintained at a lower pressure less than the vapor pressure of the fluids entering the stage so that at least a portion of the heat transfer fluid is flashed to vapor in each stage; countercurrently flowing a working fluid successively through said series of flash stages in indirect heat exchange with the vapors produced in each flash stage, whereby the vapor is condensed in each stage and said working fluid is progressively heated as it passes through said series of stages; collecting the condensate produced in each stage to prevent the mixing of said condensate with said brine in the same stage; contacting said condensate from each stage with the brine entering the subsequent stage; utilizing said working fluid in a heat engine to produce mechanical energy; and recycling the heat transfer fluid from the last stage of said series of flash stages to said initial contacting step.

Claim 26

A method for generating electrical power utilizing geothermal brine, which comprises: producing hot geothermal brine from a subterranean geothermal reservoir; partially flashing said brine to produce noncondensible gases and steam and residual brine; pressurizing said residual brine to a superatmospheric pressure above its vapor pressure to maintain said residual brine in the liquid state; initially contacting said residual brine with a heat transfer fluid comprising a saturated hydrocarbon having between about 3 and about 6 carbon atoms, wherein said heat transfer fluid is selected such that its vapor pressure is at least about eight times the vapor pressure of said residual brine at all temperatures encountered; passing said heat transfer fluid and said residual brine cocurrently through a series of flash stages, wherein each successive stage is maintained at a lower pressure less than the vapor pressure of the fluids entering the stage, so that at least a portion of the heat transfer fluid is flashed to vapor in each stage and so that the brine is cooled by not more than about 35° F. per flash stage; countercurrently flowing a multicomponent fluid successively through said series of flash stages in indirect heat exchange with the vapors produced in each flash stage, whereby the vapor is condensed in each stage and said multicomponent fluid is progressively heated and at least partially vaporized as it passes through said series of stages; collecting the condensate produced in each stage to prevent the mixing of said condensate with said brine in the same stage; contacting said condensate from each stage with the brine entering the next stage; further heating said multicomponent fluid after its exit from said series of flash stages by indirect heat exchange with said steam produced during said partial flashing of said brine, thereby condensing said steam to steam condensate; utilizing said multicomponent fluid to drive a turbine for generation of electrical power; and recycling the heat transfer fluid condensate from the last stage of said series of flash stages to said initial contacting step.

Claim 27

A method for generating electrical power utilizing geothermal brine, which comprises: producing hot geothermal brine from a subterranean geothermal reservoir; partially flashing said brine to produce noncondensible gases and steam and residual brine; pressurizing said residual brine to a superatmospheric pressure above its vapor pressure to maintain said residual brine in the liquid state; initially contacting said residual brine with a heat transfer fluid comprising a saturated hydrocarbon having between about 3 and about 6 carbon atoms, wherein said heat transfer fluid is selected such that its vapor pressure is at least about eight times the vapor pressure of said residual brine at all temperatures encountered; passing said heat transfer fluid and said residual brine cocurrently through a series of flash stages, wherein each successive stage is maintained at a lower pressure less than the vapor pressure of the fluids entering the stage, so that at least a portion of the heat transfer fluid is flashed to vapor in each stage and so that the brine is cooled by not more than about 35° F. per flash stage; countercurrently flowing a multicomponent fluid successively through said series of flash stages in indirect heat exchange with the vapors produced in each flash stage, whereby the vapor is condensed in each stage and said multicomponent fluid is progressively heated and at least partially vaporized as it passes through said series of stages; collecting the condensate produced in each stage to prevent the mixing of said condensate with said brine in the same stage; contacting said condensate from each stage with the brine entering the next stage; further heating said multicomponent fluid after its exit from said series of flash stages by indirect heat exchange with said steam produced during said partial flashing of said brine, thereby condensing said steam to steam condensate; utilizing said multicomponent fluid to drive a turbine for generation of electrical power; and recycling the heat transfer fluid condensate from the last stage of said series of flash stages to said initial contacting step.