| Title | Experimental geothermal condensate mixing into the Mývatn District Heating System, NE-Iceland to eliminate oxygen content and risk of iron sulfide scaling |
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| Authors | Helgi A. Alfredsson, Teitur Hinrichsen, Julia L. Reimer, Karl E. Sveinsson, Lárus Björnsson, Vordís S. Eiríksdóttir |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | The Mývatn District Heating System is owned and operated by the local community. It has provided 60-90°C water to the general public at the Lake Mývatn District for over half a century. The hot water is produced at the Landsvirkjun’s geothermal powerplant located in Bjarnarflag geothermal field, NE-Iceland. Cold groundwater is heated up to 80°C in a heat exchanger with geothermal brine. This 80°C water is directed into the District Heating Station where low pressure excess steam heats the water further to 99°C with a set of heat exchangers. There, gathering tanks release vapor which allows most of the dissolved oxygen to be released from the hot water. The main stream pipe from the tanks has a small dose steam injection system. For the past decades, low pressure steam has been slowly released into the hot water with a set of orifices to dope the water with H2S gas. This has maintained no oxygen in the system in the past, due to its reducing chemistry, where H2S is partially oxidized into SO4 until the water has no oxygen level. This system has resulted in unstable H2S content, sometimes causing scaling problems of sulfur bearing minerals. Here we report the findings of a successful experiment, where the condensate from the steam filled heat exchangers was released into the hot water system instead of the low pressure steam, to maintain stable low concentration of H2S and no detected dissolved oxygen within the district heating water over the experimental period. |