Occidental Petroleum

Occidental Research Corporation

Samuel G Woinsky

Process and system for recovery of energy from geothermal brines and other hot water sources, which comprises direct contact heat exchange between the brine or hot water, and a hydrocarbon working fluid, e.g. n-butane, in a heat transfer column, the heat transfer column being operated at or above the critical pressure of the working fluid, and the hot brine or hot water feed being at a temperature at or above the critical temperature of the working fluid. The heated working fluid exiting the top of the heat transfer column is expanded through an expander to produce work. The discharge from the expander is cooled to condense working fluid which is separated in an accumulator, from condensed water vapor present in the working fluid, and the condensed working fluid is pressurized and fed back to the heat transfer column. Water from the accumulator can be fed to an H.sub.2 S removal system where good quality water can be recovered. Cooled brine or water from the bottom of the heat transfer column is fed to a flashing device such as a flash drum and the working fluid flashed off is compressed and returned to the cooler at the expander discharge, for condensation and recovery. Such cooled brine or water can be fed to one or more liquid expanders prior to flashing to produce additional work. Also, entrained liquid phase working fluid can be separated from the cooled brine or water prior to flashing, and returned to the system. Uncondensible gases plus some working fluid losses are vented from the accumulator and preferably the system can be operated under conditions to vent a minimum of uncondensible gas from the accumulator, and thereby reduce working fluid losses. Any accumulator vent gas can be fed to the H.sub.2 S removal system. Cold brine or water is discharged from the flash drum. Alternatively, if the flash drum is employed as a stripping column, a portion of the vent gas from the accumulator can be recycled as stripping gas to the stripping column for recovery of working fluids therefrom. Preferably, the uncondensible gases are removed from the feed brine or hot water prior to entry into the heat transfer column, such degassing preferably being carried out by a simple flash followed by energy recovery in a steam expander. The steam from the steam expander can be fed to the H.sub.2 S removal system.

Process and system for recovery of energy from geothermal brines and

Process and system for recovery of energy from geothermal brines and other hot water sources, which comprises direct contact heat exchange between the brine or hot water, and a hydrocarbon working fluid, e.g. n-butane, in a heat transfer column, the heat transfer column being operated at or above the critical pressure of the working fluid, and the hot brine or hot water feed being at a temperature at or above the critical temperature of the working fluid. The heated working fluid exiting the top of the heat transfer column is expanded through an expander to produce work. The discharge from the expander is cooled to condense working fluid which is separated in an accumulator, from condensed water vapor present in the working fluid, and the condensed working fluid is pressurized and fed back to the heat transfer column. Cooled brine or water from the bottom of the heat transfer column and water from the accumulator are fed to a flashing device such as a flash drum operated at a pressure less than that in the accumulator, and the working fluid flashed off is compressed and returned to the cooler at the expander discharge, for condensation and recovery. Uncondensible gases plus working fluid losses are vented from the accumulator. Cold brine or water is discharged from the flashing means such as the flash drum, and any scale formed in the heat transfer column is discharged from the bottom thereof. Alternatively, if the flash drum is employed as a stripping column, a portion of the vent gas from the accumulator can be recycled as stripping gas to the stripping column for recovery of working fluids therefrom. Preferably, the feed brine or hot water is degassed prior to entry into the heat transfer column, and such degassing combined with proper control of accumulator pressure provides an economic balance between energy recovery in the system and working fluid loss in the vent gas from the accumulator.

Process and system for recovery of energy from geothermal brines and other hot water sources by direct contact heat exchange between the brine or hot water, and a working fluid exiting the top of the heat transfer column is expanded through an expander to produce work. The discharge from the expander is cooled to condense working fluid which is separated in an accumulator from condensed water vapor present in the working fluid, and the condensed working fluid is pressurized and fed back to the heat transfer column. Uncondensible gas together with working fluid losses are vented from the accumulator. In order to decrease the amount of uncondensible vent gas from the accumulator, and the loss of working fluid therein, the hot water or brine feed to the heat transfer column is initially degassed as by flashing, the extent of degassing being controlled based on the concentration of uncondensibles in such hot water or brine feed. The steam and uncondensible gas resulting from flashing is expanded in a work expander to recovery energy. The working fluid can be a compound selected from the group of aromatics, paraffins, napthenes, olefins, and ethers. Where a single component working fluid does not have the desired critical properties for use with a particular brine and well, a preferred working fluid is a mixture of hydrocarbons of the type noted above.

Process and system for recovery of energy from geothermal brines and other water containing or hot water sources, which comprises direct contact heat exchange between the brine or hot water, and a working fluid, e.g. n-butane, in a heat transfer column, the heat transfer column being operated in the subcritical pressure region of the working fluid, preferably close to or approaching the apex of the saturated vapor curve for such working fluid on the Mollier enthalpy-entropy diagram for such fluid. The heated working fluid exiting the top of the heat transfer column is expanded through an expander to produce work. The discharge from the expander is cooled to condense working fluid which is separated in an accumulator, from condensed water vapor present in the working fluid, and the condensed working fluid is pressurized and fed back to the heat transfer column. Water from the accumulator can be fed to an H.sub.2 S removal system where good quality water can be recovered. Cooled brine or water from the bottom of the heat transfer column and water from the accumulator are fed to a flashing device such as a flash drum, and the working fluid flashed off is compressed and returned to the cooler at the expander discharge, for condensation and recovery. Also, entrained liquid phase working fluid can be separated from the cooled brine or water prior to flashing, and returned to the system. Uncondensible gases plus some working fluid losses are vented from the accumulator, and preferably the system can be operated under conditions to vent a minimum of uncondensible gases from the accumulator, and thereby reduce working fluid losses, Any accumulator vent gas can be fed to the H.sub.2 S removal system.

Process and system for recovery of energy from geothermal brines and other water containing or hot water sources, which comprises direct contact heat exchange between the brine or hot water, and a working fluid, e.g. n-butane, in a heat transfer column, the heat transfer column being operated in the subcritical pressure region of the working fluid, close to or approaching the apex of the saturated vapor curve for such working fluid on the Mollier enthalpy-entropy diagram for such fluid. The heated working fluid exiting the top of the heat transfer column is expanded through an expander to produce work. The discharge from the expander is cooled to condense working fluid which is separated in an accumulator, from condensed water vapor present in the working fluid, and the condensed working fluid is pressurized and fed back to the heat transfer column. Cooled brine or water from the bottom of the heat transfer column and water from the accumulator are fed to a flashing device such as a flash drum operated at a pressure less than that in the accumulator, and the working fluid flashed off is compressed and returned to the cooler at the expander discharge, for condensation and recovery. Uncondensible gases plus working fluid losses are vented from the accumulator. Cold brine or water is discharged from the flashing means such as the flash drum, and any scale formed in the heat transfer column is discharged from the bottom thereof.

The invention provides for an improved seal leg and method for transferring particulate solids in a non-fluidized condition from a first pressure zone to a second pressure zone while controlling the level of solids in the first pressure zone or in the seal leg. A relatively uniform pressure gradient is produced across the length of the seal leg by bleeding gas into or out of the seal leg along its length. Bleeding gas as aforesaid permits the use of a shorter seal leg and a smaller diameter seal leg for a given solids flow rate as compared to a seal leg not provided with means for bleeding gas in or out along its length. The pressure gradient along the length of a seal leg not provided with means for bleeding gas in or out along its length will be highly nonuniform resulting in retarded solids flow due to localized high pressure gradients and a low overall average pressure gradient resulting in a substantial length requirement for the seal leg to maintain a pressure seal.

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Irvine, CA, United States of America

Samuel G Woinsky