| Title | A systematic approach to decrease the oxygen gas concentration at Þeistareykir GPP |
|---|---|
| Authors | Alma Stefansdottir, Jon Arnar Emilsson |
| Year | 2023 |
| Conference | World Geothermal Congress |
| Keywords | Koldís, Þeistareykir, Iceland, gas scrubbing system, flammability, greenhouse gas, carbon dioxide, CO2, hydrogen sulfide, H2S, oxygen, O2. |
| Abstract | Electricity generation using geothermal resources can be challenging and requires responsible monitoring. An increasing demand of sustainability across the geothermal sector calls for lower greenhouse gas (GHG) emissions, thereby promoting the importance of CO2 removal from geothermal power plants (GPPs) by gas scrubbing and re-injection or utilization. Þeistareykir GPP, located in Northeast Iceland, has an installed capacity of 90 MWe and is the most recent power plant owned by Landsvirkjun, the National Power company of Iceland. The GPP has two turbines with a shell and tube type condensers, where the gas extraction system of each turbine is composed of four identical units, in total eight units. The non-condensable gas (NCG), including carbon dioxide (CO2), is currently led to cooling towers where it is released directly to the atmosphere. However, in a project named Koldís, Landsvirkjun aims to implement a gas scrubbing and re-injection system at Þeistareykir by the year 2025. Various factors influence the NCG composition, both geochemical and operational factors. For this reason, proper monitoring of the gas composition is fundamental for 1) the operation of Þeistareykir GPP and 2) the design, commissioning and operation of gas scrubbing systems. In regard to gas scrubbing, low oxygen (O2) gas concentration is required to limit the risk of technical complications and danger. The flammability of the treated gas is a common concern in the operation of gas scrubbing stations, including in the Koldís project at Þeistareykir GPP. A focused search was carried out to detect, quantify and prevent potential atmospheric leakages into the production process of Þeistareykir GPP. Gas samplings and chemical analysis was executed periodically prior to leak inspection. Real-time O2 measurements performed during the first phases of inspection. After the inspection, O2 concentration of all systems was below the maximum limit, ranging from 0.67-0.92 %vol O2. An overall average from both turbines, corresponding to the inlet gas flow to a gas scrubbing station, is 0.74 %vol. The treated gas from the scrubbing station should not be flammable, but in the case on O2 concentration increase to 1.32-2%vol, the concentration of fuels falls below the upper flammability limits (UFL) and into a flammable region. This paper outlines the background and motivation for the project, the methodology applied, and the initial and resulting final O2 gas concentration. The results will be discussed in regard to the operation of Þeistareykir GPP, the Koldís project and potential flammability. |