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Geothermal "mining" waste in Iceland -disposal and value creation
Sveinborg Hlíf Gunnarsdóttir1, Hjalti Franzson1, Vigdís
Harðardóttir1 and Bryndís G. Róbertsdóttir2.
1. ÍSOR, Iceland geosurvey
2. National energy authority
Introduction
− Geological context
− Geothermal mining waste in Iceland
− Waste water, gas and precipitates from geothermal power production.
− Some examples of disposal and value creation
Iceland‘s geological setting
Geological setting
Central volcanoes
Prospect areas and gold anomalies in Iceland
Formation of epithermal ore
The Þormóðsdalur prospect
− Quartz-adularia vein system with Au enrichment from <0.5 ppm to a maximum of 415 ppm.
− 3000 m from 41 cored wells.
− Mining would be underground.
− Mining waste would have to be taken good care of due to proximity to a river and a lake. Fortunately base metal concentrations are very low.
− ÍSOR is a part of the NORDMIN project WASCIOUS, Water conscious mining.
Mining waste in Iceland
− Waste from the use of our geothermal resources is our mining waste
− Three types of geothermal mining waste
− Waste water
− Gases
− Mineral precipitations from geothermal fluids
Waste water- Disposal and value creation
Blue lagoon - Svartsengi Gray lagoon - Reykjanes
Pictures: ÍSOR
Waste water - Reinjection
Picture: http://www.bgs.ac.uk/research/energy/geothermal/
Hellisheidi power plant
Electricity production 300 MW CO2 emission 40 000 t/yr Waste water 700kg/s
Thermal capacity 400 MWth H2S emission 12 000 t/yr Waste water 22 Mt/yr
Waste gas – Carbfix/Sulfix pilot project at Hellisheiði
− Goal of the project: Reduce CO2
and H2S emissions from the geothermal power plant
− CO2 and H2S separated from gas emissions and reinjected with waste water into the system to precipitate in the basaltic rocks as carbonates and sulfides.
Picture: Clark et al., 2016 in prep.
Basic theory of Carbfix/sulfix
Waste gases
• Carbon Recycling International• Operating next to the Svartsengi power plant.• Turning C02 into methanol fuel
Picture: http://www.carbonrecycling.is
Precipitation of minerals from geothermal fluids-
Scaling in Reykjanes
Wellhead RN9
Orifice plate
Gray Lagoon
Vent
house Separation
station
19 m
Upstream
Downstream
G.O.Fridleifsson
Precipitation of minerals from geothermal fluids-Scaling in Reykjanes
RN12, 314°C max in well, at wellhead
247°C; ΔP 15 bars, CuS
5µ
m
Cc
Bornite, sphalerite,
galena, chalcopyrite,
covellite
RN-12
Zn = 20%
Fe = 9%
Cu = 23%
Pb = 15%
S = 22%
570 ppm Au
9200 ppm Ag
Medium-pressure wells
Precipitation of minerals from geothermal fluids-Scaling in Reykjanes
Borehole – clogging – surface pipeline
330°C
260°C
267°C Sph, cpy, gn,
(bn, cv, py, Am
SiO2)
Zn: 48-43 wt%
Cu: 11-18 %
Fe: 3-4 %
Pb: 0.3-1%
SiO2: 3-2%
S: 30-28%
Ag: 890-
3500ppm
Au:110-80 ppm
Precipitation of minerals from geothermal fluid
The National Planning Agency
− State authority, under the Ministry for the Environment and Natural Resources
− Responsible for the administration and implementation of the Planning Act, the Environmental Impact Assessment Act (EIA) and the Strategic Environmental Assessment Act (SEA).
Final comments
− Iceland is a living example of the geological environment and processes which created some of the metallogenic provinces now hosting deposits which are being mined.
− There are no mines in Iceland but still we have to take care of the mining waste.
− Innovative solutions regarding waste water and gases might have some implications in a broader perspective of the mining industry.
− Need for expertise in Iceland if future gold mining prospect will be exploited.
− Nordmin is a great collaboration, learning and networking platform for Icelandic scientists and consultants.
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