Importance

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Abstract

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.

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First Claim