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Testing corrosion on H2S Abatement system of geothermal plant in Iceland

Hellisheidi geothermal power plant, Iceland (source: ThinkGeoEnergy)
Alexander Richter 4 May 2017

Legislation in Iceland requires geothermal plants to decrease the emission of hydrogen sulfide from operations, for which a gas abatement plant is used. A new paper is looking into the corrosion effects of such activities.

Geothermal energy plays an important role in the energy supply of Iceland, and while generally a renewable and green power source, geothermal steam contains some non-condensable gases.

These are gases that are not easily condensed by cooling and include carbon dioxide (CO2), hydrogen sulfide (H2S), nitrogen (N2), methane (CH4), and argon (AR). These gases can be considred greenhouse, corrosive or toxic gases. A regulation in Iceland therefore set stricter guidelines on the atmospheric concentration of hydrogen sulfide, which took effect in 2014. This has forced the country’s geothermal industry to take actions into reducing hydrogen sulfide emissions into the air.

In an article of Materials Performance, a collaboration of universities and Icelandic power companies is described that is implementing an injection abatement project, CarbFix-SulFix, at the Hellisheidi geothermal power plant operated by ON Power (Reykjavík, Iceland), a subsidiary of Reykjavík Energy.

The Hellisheidi geothermal plant is one of the largest geothermal power plants in the world with a production capacity of 303 MW of electricity and 133 MW of thermal energy. It is located in one of Iceland´s biggest geothermal zones, the Hengill area, which is linked to three volcanic systems.

The project captures CO2 and H2S emissions from the Hellisheidi power plant in a gas abatement plant that separates them from the non-condensable gas stream using a simple scrubbing process, and then re-injects them in water into reactive basaltic rock at a depth of around 800 m or greater. If these gases were not captured and reinjected, the Hellisheiði power plant would emit ~40,000 tons of CO2 and ~12,000 tons of H2S.

To evaluate the corrosion resistance of the absorption tower, which is in contact with high concentrations of H2S, Sigrún Nanna Karlsdóttir, associate professor in the Industrial Engineering, Mechanical Engineering, and Computer Science Department at the University of Iceland and her colleagues at the University of Iceland and the Innovation Center Iceland conducted a study on the corrosion behavior of UNS S31603 while being exposed to the H2S cleaning process in the absorption tower.

More information on the study can be found in the CORROSION 2016 paper, “Corrosion Testing in H2S Abatement System at Hellisheidi Geothermal Power Plant in Iceland,” by S.N. Karlsdóttir, S.M. Hjaltason, and K.R. Ragnarsdottir.

Source: Materials Performance