oxy-fuel combustion research at chalmers...fuel + combustion wet or dry flue gas recycle flue gas...
TRANSCRIPT
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Chalmers University of Technology
Oxy-fuel combustion research
at Chalmers
Daniel Kühnemuth and Daniel Fleig
Division of Energy Technology
Department of Energy and Environment
Contact:
Chalmers Energy Conference, 26-27.02.2011, Gothenburg, Sweden
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Chalmers University of Technology
Experimental research
in oxy-fuel combustion• Nitrogen Chemistry
»NO emissions»NOx - reburning
• Sulphur Chemistry: »Fate of Sulphur»SO2 emissions
• Radiative Heat Transfer»Radiation intensity
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Chalmers University of Technology
Combustion
experiments
• Cylindrical combustion chamber
(D = 800 mm, H = 2400 mm)
• Top-fired burner, swirling, non-premixed
• Dry or wet flue gas recycle• Dry or wet flue gas recycle
• 100 kWth propane or
pulverized lignite
• Controlled feed gas concentration of
oxygen (O2) and nitric oxide (NO)
• Possibility for staged combustion
• In-furnace measurements
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Chalmers University of Technology
NOx and SOxemissions in oxy-fuel
Importance of research:
– Emissions from the combustion process can lead to hardly controllable acid formation in the CO2compression and cleaning part (corrosion)
– NOx and SOx concentrations might be elevated in the vent stream from the CO2 cleaning (stack)
– The level of permitted NOx and SOx concentrations in the liquid CO2 is not regulated yet
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Chalmers University of Technology
NOx and SO2 emissions
The main difference between air and oxy-fuel firing is an increased
concentration of combustion products (due to flue gas recycle / absence
of air-borne nitrogen)
O2
Fuel+ Combustion
Wet or dry flue gas recycle
Flue gas
Several oxy-fuel cases are investigated and compared to air-firing
• Studies on NOx formation:
– Propane as fuel with NO injection
– Lignite as fuel
• Studies on SOx formation:
– Lignite as fuel
FuelCombustion
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Chalmers University of Technology
NOx reduction by reburning
• Depending on the recycle ratio of flue gas 60 to 80% of NOx produced
are recycled back to the furnace.
• The reaction of NO with hydrocarbon radicals in the flame zone is called
reburning:reburning:
� Recycle of NO containing flue gas is the most important reason for
increased reduction efficiency in oxy-fuel combustion
Additional information: Kühnemuth, D.; Normann, F.; Andersson, K.; Johnsson F.; Leckner, B.; Reburning
of Nitric Oxide in Oxy-Fuel Firing—The Influence of Combustion Conditions, Energy and Fuels, 2011
(http://pubs.acs.org/doi/abs/10.1021/ef101054t)
NO
N2
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Chalmers University of Technology
• Around three times higher SO2 concentration in oxy-fuel
compared to air-fired conditions (for the fuel investigated)
• However, lower SO2 emissions [mg/MJ]
SO2 reduction through increased
sulphur self-retention by ash
• However, lower SO2 emissions [mg/MJ]
• Higher amount of S in ash during oxy-coal combustion
• Higher SO2 concentration in oxy-fuel might favour sulphate formation
and formation of SO3 (as modeling shows)
Additional information: Fleig, D.; Andersson, K.; Johnsson, F.; Leckner, B. Conversion of Sulfur during
Pulverized Oxy-coal Combustion, Energy and Fuels, 2011 (http://pubs.acs.org/doi/abs/10.1021/ef1013242)