Review of H2S abatement in geothermal plants and laboratory scale design of tray plate distillation tower

• Main Author: Esteban Rodríguez 1987-
• Other Authors: Háskólinn í Reykjavík
• Format: Thesis
• Language: English
• Published: 2014
• Subjects: Orkuverkfræði; Orkuver; Jarðhiti; Tækni- og verkfræðideild; Meistaraprófsritgerðir; Sustainable energy engineering; Geothermal energy; Power plants; School of Science and Engineering; Reykjavík; Iceland
• Online Access: http://hdl.handle.net/1946/17344

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 even potentially using these gases to generate value for use in industrial processes. A literature research was performed in order to review the most common abatement methods, their characteristics, advantages and limitations. The key variables identified during the literature research are the economics of the process, the ratio of ammonia-to-hydrogen sulfide in the geothermal brine and the condenser design. By using the criteria described in the work, some processes, or combination of processes are proposed. All of the methods suggested are considered effective, achieving over 90% removal of H2S entering the geothermal field. The methods that presented the most advantages included scrubbing with alkali, liquid redox methods, reinjection of NCG, Selectox, Dow-Spec RT-2 and BIOX. Although many H2S abatement methods are available and used in different geothermal plants across the world, few, if any, were economically feasible for Reykjavík Energy to operate in Iceland. However, it appears that using distillation as a method of abating H2S emissions is potentially possible and perhaps economically beneficial in the particular context of Iceland. This process may lead to a system with relatively little equipment required but a relatively complex operation. Special care must be placed in material selection and prevention of gas hydrates forming inside the equipment. Overall, it is recommended that this laboratory scale tower be built using modular design. This way, different materials can be tested at different operating conditions and the overall performance of the distillation tower can be evaluated.