Heat transfer process and system

Abstract

Direct contact heat transfer process and system for recovery of energy from geothermal brines or other hot aqueous solutions of a non-volatile solute, or for desalination, using staged evaporator-condenser units operating with a low boiling water-immiscible liquid hydrocarbon. Each stage comprises a closed vessel divided into two compartments, an evaporator and a condenser, by a bubble cap tray similar in construction to those used in distillation. In one embodiment, hot geothermal brine or other hot aqueous liquid is introduced into the liquid hydrocarbon contained in the lower compartment of each stage, causing boiling of the hydrocarbon. Hydrocarbon vapors pass from the evaporator compartment through the bubble caps to the upper condenser compartment where they are condensed in contact with a cooler water stream. The heated water stream under substantial pressure is fed to an expander or turbine to produce work. In another embodiment using the same staged heat transfer system for desalination, relatively hot fresh water is introduced into the liquid hydrocarbon contained in the lower compartment of each stage, causing boiling of the hydrocarbon, and the hydrocarbon vapors pass from the evaporator compartment to the upper condenser compartment where they are condensed in contact with a colder saline stream. The heated saline stream is flash evaporated and the vapors are condensed with a portion of this condensed stream taken off as product.