Corrosion Behaviour of Materials in H2S Abatement System for Geothermal Power Plants

117 Pages·2015·18.46 MB·English

Corrosion Behaviour of Materials in
H S Abatement System for Geothermal
2
Power Plants
Sölvi Már Hjaltason
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CORROSION BEHAVIOUR OF MATERIALS IN H S
2
ABATEMENT SYSTEM FOR GEOTHERMAL POWER
PLANTS
Sölvi Már Hjaltason
60 ECTS thesis submitted in partial fulfillment of a
Magister Scientiarum degree in Mechanical Engineering
Advisor
Sigrún Nanna Karlsdóttir
Kolbrún Ragna Ragnarsdóttir
External Examiner
Geir Þórólfsson
Faculty of Industrial Engineering,
Mechanical Engineering and Computer Science
School of Engineering and Natural Sciences
University of Iceland
Reykjavik, October 2015
Corrosion Behaviour of Materials in H S Abatement System for Geothermal Power Plants
2
Corrosion experiments in H S abatement
2
60 ECTS thesis submitted in partial fulfillment of a M.Sc. degree in Mechanical Engineering
Copyright (cid:13)c 2015 Sölvi Már Hjaltason
All rights reserved
Faculty of Industrial Engineering,
Mechanical Engineering and Computer Science
School of Engineering and Natural Sciences
University of Iceland
Hjarðarhagi 6
107, Reykjavik, Reykjavik
Iceland
Telephone: [phone]
Bibliographic information:
Sölvi Már Hjaltason, 2015, Corrosion Behaviour of Materials in H S Abatement System for
2
Geothermal Power Plants, M.Sc. thesis, Faculty of Industrial Engineering,
Mechanical Engineering and Computer Science, University of Iceland.
Printing: Háskólaprent, Fálkagata 2, 107 Reykjavík
Reykjavik, Iceland, October 2015
To my family

Abstract
Geothermal energy is a sustainable and clean energy source. Among renewable energy
sources geothermal energy is environmentally attractive since the resource can be utilized
continuously and is not dependent on weather conditions. When utilized, however, gases
such as carbon dioxide (CO ) and hydrogen sulfide (H S) are emitted to the atmosphere,
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these emissionsare consideredto be one ofthe main environmental, safety and healthcon-
cerns of geothermal utilization. Recently Icelandic power companies started re-injecting
H S and CO back into the ground in a research project called SulFix to decrease H S
2 2 2
emission from Icelandic geothermal power plants. The gases are dissolved in condensate
at 25◦C and 5 bars in a newly constructed air cleaning station at Hellisheiði Power Plant.
In this study the corrosion behaviour of various materials including the ones chosen for
the absorption tower in the cleaning station are studied in the H S cleaning process. Cor-
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rosion experiments were done over two time periods, 4 and 12 weeks. The specimens were
installed into the absorption tower where H S and CO are dissolved in condensate. The
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susceptibility to stress corrosion cracking (SCC) of the austenitic stainless steels 304L,
316L was investigated and corrosion rates were calculated for the carbon steel S235, and
the stainless steels 316L and SAF 2205 for the two time periods. The results show that
the material selection for the absorption tower is sufficient. 316L and SAF 2205 showed
no signs of corrosion damages for all experiments while 304L experienced SCC. Results for
the carbon steel S235 showed that the steel was severely damaged by hydrogen induced
cracking (HIC) and had a poor performance in the tower.
v

Útdráttur
Jarðvarmaorka er sjálfbær og hrein orka. Á meðal endurnýjanlegra orkugjafa er jarðvar-
maorka aðlaðandi þar sem hægt er að nýta hana stanlaust óháð veðurskilyrðum. Samt
sem áður, við nýtingu, er gösum á borð við koldíoxíð (CO ) og brennisteinsvetni (H S)
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hleypt út í andrúmsloftið, þessi útblástursefni eru talin vera helsta ógn við umhverfi,
öryggi og heilbrigði af völdum jarðvarma nýtingarinnar. Nýlega fóru íslensk orkufyrirtæki
að dæla niður H S og CO aftur ofan í jörðina í tilraunaverkefni sem kallast SulFix til þess
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að minnka losun H S frá íslenskum jarðvarmaverum. Gösin eru leyst upp í þéttivatni við
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25◦C og 5 bör í nýuppsettri lofthreinsistöð við Hellisheiðarvirkjun. í þessari rannsókn er
tæringarhegðun nokkurra málma þar á meðal þess sem valin var fyrir lofthreinsiturn stöð-
varinnar rannsökuð í H S hreinsunarferlinu. Tæringar tilraunir voru gerðar með tveimur
2
tímabilum, 4 og 12 vikur. Sýnin voru sett inn í lofthreinsiturninn þar sem leysni H S
2
og CO á sér stað í þéttivatninu. Næmni spennutæringar (SCC) fyrir austenísku ryðfríu
2
stálin 304L og 316L voru rannsökuð og tæringarhraðar reiknaðir fyrir svart stál S235, og
ryðfríu stálin 316L og SAF 2205 fyrir bæði tímabilin. Niðurstöðurnar sýna að efnisvalið
fyrir lofthreinsiturninn sé nægjanlegt. 316L og SAF 2205 sýndu engin merki um tæringu
fyrir allar tilraunir á meðan 304L varð fyrir SCC. Niðurstöður fyrir svarta stálið sýndu
að það var alvarlega skemmt af völdum vetnisskemmda (HIC) og hafði laka frammistöðu
í turninum.
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