Process and system for recovery of energy from geothermal brines and

Abstract

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.