Process and system for recovery of energy from geothermal brines and

Abstract

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.