Ingvi Gunnarsson, R&D, Reykjavik Energy Iceland Geothermal Conference 2013 March 5-8, 2013, Harpa, Reykjavík

1. Disposal of geothermal
gases
Iceland Geothermal Conference 2013
Ingvi Gunnarsson
Research and Development

2. 2
• Emission of geothermal gases is an
inevitable part of high temperature
geothermal utilization
• Major gases in geothermal fluids
• CO2, H2S, H2, N2, CH4, NH3
• Some of the gases are environmentally
important
• Greenhouse gases
• Corrosive
• Toxic
• Flammable
• Bad smell
• Concentration depends on:
• Temperature
• Composition of fluid
• Geological settings
• Origin
• Magmatic
• Meteoric
• From water-rock reactions
Geothermal gases

3. • Reservoir temperature between 250-
320°C.
• Concentrated in the steam phase during
separation of the geothermal fluid.
• Concentration of gases in the steam
phase is around 0,4%
• From condensers of the turbines of the
power plants they are pumped to
atmosphere using vacuum pumps
• Released to atmosphere on top of
cooling towers to secure better
distribution
Gas emission from Hellisheiði
and Nesjavellir power plants,
SW Iceland
24.3.2013
Hellisheiði
Power plant
Hellisheiði and Nesjavellir power plants
• Located on the Hengill central volcano 20-25 km from
Reykjavík
• Nesjavellir commissioned in 1990 and Hellisheiði in 2006
• Installed capacity
- Hellisheiði - Nesjavellir
- 303 MWe - 120 MWe
- 133 MWth - 290 MWth
Nesjavellir
power plant

4. 4
• Gas emission has been gradually increasing
• Total emission from both power plants was
62000 tons CO2 and 28000 tons H2S in 2012
• 5-6% of CO2 emission of fossil fuel power
plants of comparable size.
Composition of gas
and total emission

5. 5
H2S concentration in air
• Theoretical modeling of
distribution of H2S
indicates that the air
quality of a large area is
affected by Nesjavellir
and Hellisheiði power
plants

6. • New Icelandic regulation on
atmospheric H2S concentration
− Valid in 2014
− Stricter than WHO guidelines
− Puts high demands on the
geothermal industry in Iceland to
reduce H2S emissions
Concentration of H2S in atmosphere

7. 3.9.2012 CPTDC visit to OR headquarters
Experimental project to lower gas emission
from Hellisheiði power plant
Three experimental projects at OR
aim at developing new methods
and technology:
1. Gas separation station:
Capturing CO2 and H2S emitted
from Hellisheiði power plant
2. SulFix – reinjection of H2S into
the geothermal system
3. CarbFix – Reinjection of CO2
into basaltic formation

8. 8
• Geothermal gases have variable
solubility in water
• Gas treatment necessary before
dissolution and reinjection
• Gas treatment in the gas separation
station involves
• Separation of soluble gases from
insoluble
• Distillation to separate CO2 from H2S
• Geothermal gas separated into
streams of
• H2S
• CO2
• H2, N2, CH4, Ar
Gas separation
station

9. SulFix and CarbFix
• Experimental projects that aim at to develop and test
necessary technic to dissolve geothermal gases in water and
re-inject them into the subsurface.
• Increase understanding of the fate of CO2 and H2S injected into
the subsurface
• Use natural processes in sequestering geothermal gases
•

10. • Gas: 64% CO2, 35% H2S, 1% H2
from gas separation station.
• Dissolved at 8 bar in separated
geothermal water at 100°C or
condensate water at 40°C
• 100 tons gas injected in 2012
• Formation temperature 260-
270°C
• Geochemical monitoring and
modeling and tracer test on
injection site
• Injection of dissolved
geothermal gases does not clog
the injection well
SulFix
250-270°C

11. • Industrial/academic collaborative
project. OR, HI, CNRS, Columbia
University NY, UCPH and Amphos 21.
• Pure CO2 injection 175 tons
completed
• Injection of 1000 tons geothermal
gas mixture from gas separation
station (75% CO2, 24% H2S, 1% H2)
in 2013
• Gases are dissolved 20°C water at
23-25 bars 300-350 m in the
injection hole.
• Formation temperature 30-80°C
• Laboratory experiments, geochemical
modeling, tracer tests and extensive
monitoring of injection site.
CarbFix

12. After injection – Solubility and
mineral storage
Photo: J. Alean
Basalt CO2 dissolved in water Carbonates
Photo: H. Sigurdardottir
Photo: J. Alean
Basalt H2S dissolved in water Metal Sulfides

13. H2S sequestration
H2S is a reactive element and
equilibrates with its environment
• There is a strong temperature
control on the concentration of H2S
in Hellisheiði geothermal system.
• Concentration of H2S in the injected
fluid exceeds the equilibrium
concentration in the system.
• Theoretical modeling and
equilibrium thermodynamic
calculations indicate that the same
processes that govern H2S
concentration in Hellisheiði
geothermal system will mineralize
majority of the injected H2S.
-5
-4,5
-4
-3,5
-3
-2,5
-2
-1,5
-1
-0,5
0
50 100 150 200 250 300 350
logC(H2S)
Temperature (°C)

14. The aim of SulFix is to develop a method to lower H2S
emission from high temperature power plants that has
lower operational cost and is more environmentally
friendly than current H2S cleaning methods
Returning H2S back into the geothermal system on the
same form as it came out has to be considered a good
H2S abatement method
Why dissolution and reinjection of H2S?

15. • Next step to lower gas emission from Hellisheiði
power plant is to build a adsorption tower to clean
out 15-20% of H2S from the power plant and
inject it back into the geothermal reservoir (2014)
• If successful, amine unit will be installed to
selectively remove H2S from the geothermal gas
stream and dissolved in the effluent water. 50%
removal of H2S (2016)
• Additional amine unit installed if needed to meet
the Icelandic regulation on atmospheric H2S
concentration.
• Parallel to this OR will continue looking at
conventional H2S abatement solutions (oxidation)
• And leave open possible collaboration with
companies aiming at producing valuables from the
gas
• Carbon Recycling (Methanol)
• Prokatín (single cell proteins)
• CO2 for green houses
• Sulfuric acid
From pilot to
industrial scale

16. 16
• Emission of geothermal gases is an inevitable part of
high temperature geothermal utilization
• Annually OR power plants emit 62000 tons CO2 and
28000 tons H2S
• New regulation on H2S concentration in air puts high
demands on the geothermal industry to reduce H2S
emissions
• Experimental projects on gas treatment and reinjection
carried out since 2007. To date 350 tons injected. 1000
tons more in 2013.
• From pilot to industrial scale in 2014. 15-20% of the
gas from Hellisheiði power plant dissolved in effluent
waters and re-injected into the geothermal reservoir.
Summary