The Behaviour Of Hg In Some New Zealand Geothermal Reservoir And Production Environments

Jump to: navigation, search


OpenEI Reference LibraryAdd to library

Conference Paper: The Behaviour Of Hg In Some New Zealand Geothermal Reservoir And Production Environments

Abstract
Hg is present in the near-neutral chloride reservoir fluids of Kawerau, Ohaaki and Rotokawa geothermal systems principally as elemental mercury, Hg", but in quantities that are undersaturated with respect to Hg-bearing mineral phases. Thermodynamic modelling shows that conductive cooling of these fluids (without gas loss) leads to the precipitation of cinnabar, whereas adiabatic cooling strongly partitions Hg= into the vapour phase. Condensation of Hg bearing geothermal vapours into shallow (T = 100"C), oxygenated groundwaters is predicted to lead to near quantitative precipitation of Hg as cinnabar, whereas unhindered passage of the Hg(,, bearing vapours to the surface may result in condensation of Hg(,, to liquid Hg (quicksilver) at temperatures < 5°C. The modelled results are consistent with observed Hg enrichment in production well cuttings from the upper 100 m of the Kawerau reservoir. Hg" is highly volatile and partitions strongly into the vapour phase throughout geothermal production circuits. At Ohaaki, Hg is carried in the steam phase from wells, to separation plants and turbinekondenser units. It is only where Hg makes contact with oxygenated condenser and intercooler fluids that some of the Hg is co-precipitated as HgS, along with elemental sulfur. Whereas 99.5% of the Hg is discharged by gas exhausters to atmosphere, it may be possible within the present configuration to extract Hg from the vapour phase, but only if kinetic limitations can be overcom

Authors 
Bruce W. Christenson, Edward K. Mroczek and Sachihiro Taguch








Published 
GRC, 2002





DOI 
Not Provided
Check for DOI availability: http://crossref.org



 

Citation

Bruce W. Christenson,Edward K. Mroczek,Sachihiro Taguch. 2002. The Behaviour Of Hg In Some New Zealand Geothermal Reservoir And Production Environments. In: (!) ; (!) ; (!) . (!) : GRC; p. (!)