Review of H2S Abatement Methods in Geothermal Plants

Abstract

Despite having significantly lower emissions in comparison to traditional fossil fuel plants, geothermal power plant emissions can still be substantial. In particular, dissolved non-condensable gases (NCG) such as CO2 and H2S within geothermal fluids have led to increased interest in developing methods for decreasing these emissions through abatement systems, or potentially using these gases to generate value for use in industrial processes. This paper discusses some of the H2S abatement methods available to the industry, such as liquid redox methods, reinjection, Selectox, Dow-Spec RT-2, BIOX, and others. Tools for screening suitable abatement methods for geothermal fields of different non-condensable gas characteristics are presented. The paper also presents technology being researched, but not yet widely applied commercially. The paper presents the most common abatement methods, their characteristics, advantages, and limitations. A simple decision tree is also provided as a screening tool for choosing appropriate abatement methods for different geothermal plant and geothermal steam compositions. It is a basic outline designed to provide a quick, graphical summary of the major considerations and constraints involved with choosing candidate methodologies, prior to more detailed consideration of preferred options given a plant’s site-specific characteristics. Finally, the paper discusses the legislative changes in Iceland that will lead to greater use of abatement systems for plants in that country, the screening considerations applicable to that setting, and research projects underway at the Hellisheidi field involving distillation and reinjection of CO2 and H2S into the geothermal reservoir