Comparison of Direct Contact and Kettle Reboilers to Reduce Non-Condensables in Geothermal Steam

Abstract

The economics of energy recovery from high gas content geothermal steam is generally improved if the gas content of the steam can be reduced before it is admitted to the power recovery turbines. This gas reinjection has normally been accomplished by heat exchange where the energy of the high gas content steam is used to generate a lower pressure but lower gas content motive steam. The exchange of heat can be carried out using standard surface heat (indirect contact) exchange devices or by direct contact between the geothermal steam and a cooler water stream. This paper presents a comparison of the two types of heat exchange and shows that direct contact heat exchange is more cost effective than surface heat exchange for a resource steam containing 20 weight percent gas.