alkali sulphation in flames - ieaghg presentations... · 2015. 11. 16. · alkali sulphation in...
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Alkali sulphation in flames
Thomas Ekvall(thomas.ekvall@chalmers.se)
Project funded by The Swedish Research Council
Department of Energy and Environment, Division of Energy Technology, Chalmers University of Technology, Sweden
5th Meeting of the IEAGHG International Oxyfuel Combustion Research Network – 27th -30th October 2015, Wuhan, China
mailto:thomas.ekvall@chalmers.se
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Outline
Aim
Background
• What has been done and why
Project description
• Experimental setup
Results
Summary
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Aim
• Investigating K-S-Cl chemistry in combustion
• Is there a difference between air-fuel and oxy-fuel combustion?
Aim - Background – Project description – Results - Summary
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Alkali salts
• 𝐾 + 𝐶𝑙 → 𝐾𝐶𝑙
• Deposits
• High temperature corrosion
• Lower operating temperatures -> Lower efficiency
Coal vs Biomass
Coal
• Fossil
• Large resources
• High sulphur content
Biomass
• Renewable
• High alkali content (mainly potassium, K)
• High chlorine (Cl) content
Biomass fired boiler
Aim – Background – Project description – Results - Summary
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Alkali salts
• 𝐾 + 𝐶𝑙 → 𝐾𝐶𝑙
• Depositions and High temperature corrosion
• 𝐾𝐶𝑙 + 𝑆𝑂𝑋 → 𝐾2𝑆𝑂4
• Higher melting point (less sticky)
Degree of sulphation: How much KCl will be converted to 𝐾2𝑆𝑂4?
• More sulphur → higher degree of sulphation
Co-Combustion
Coal + Biomass
• Partly renewable
• High alkali content
• High chlorine content
• High sulphur content
Co-fired boiler
Aim – Background – Project description – Results - Summary
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Oxy-Fuel combustion
Combustion
O2
Fuel
CO2SO2H2OKClHClK2SO4
Ash removal Condenser
CO2SO2H2OHCl
CO2SO2
KClK2SO4
H2OHCl
Aim – Background – Project description – Results - Summary
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Project description
Aim
• Investigating K-S-Cl chemistry in combustion
• Compare air and oxy-fuel combustion
• Will the higher sulphur content in a oxy-fuel system result in a higher degree of sulphation?
Experimental methodology
• Isolating the chemistry of interest
• Neglecting release of inorganic species and ash retention
• Get a better control of the amount of K, S and Cl in the system
Aim – Background – Project description – Results - Summary
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Experimental setup
Fuel
• Propane
• 1.73 g/s (80kW)
Oxidizer
• Air
• Oxy-Fuel
• 25% O2• 75% dry flue gases
Injections
• SO2 (g)
• KCl (aq)
Aim – Background – Project description – Results - Summary
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Experimental setup
Sulphur injection
• Gaseous SO2
• 0.15 - 2.2 Nl/min
• 100 - 3000 ppm
KCl injection
• Aqueous solution, 3.34 wt%
• 0.9 l/h
• 100 ppm
Aim – Background – Project description – Results - Summary
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Experimental setup
Measurement systems
• Gas composition • FTIR
• HCl concentration (KCl+SOx->K2SO4+HCl)
• Solid particles• IACM™ *
• KCl aerosols
*IACM™ (In-situ Alkali-Chloride Monitor)
Aim – Background – Project description – Results - Summary
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Results
Air (port 2)
OF25 (port 3)
No KCl KCl
Aim – Background – Project description – Results - Summary
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Sulphation of Potassium Chloride
• Good agreement between experiments and simulations*
• Higher degree of sulphation oxy-fuel combustion
• Complete sulphation already at S/K=3 for OF25
• Suggests oxy-fuel to be a preferred from a corrosion point of view
Aim – Background – Project description – Results - Summary
*For simualtion deatails: Ekvall, T.; Normann, F.; Andersson, K.; Johnsson, F., Modeling the alkali sulfation chemistry of biomass and coal co-firing in oxy-fuelatmospheres. Energy and Fuels 2014, 28 (5), 3486-3494.
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Sulphation of Potassium Chloride
• Only an effect of higher SO2 concentration?• No
• Additional reason still to be found
Aim – Background – Project description – Results - Summary
For simualtion deatails: Ekvall, T.; Normann, F.; Andersson, K.; Johnsson, F., Modeling the alkali sulfation chemistry of biomass and coal co-firing in oxy-fuelatmospheres. Energy and Fuels 2014, 28 (5), 3486-3494.
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Reaction Routes during Sulphation
Sulphation via:
SO2SO3SO2 or SO3
Other:
SO3 formation
Pre-sulphation
Aim – Background – Project description – Results - Summary
Air OF25
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Summary
• The alkali chemistry is of importance due to the corrosivity of the salts that they might form. Between chlorides and sulphates the latter is to prefer from a HTC point of view.
• A higher degree of sulphation is reached during oxy-fuel combustion compared to air combustion. Almost complete combustion is reached for S/K=3.
• It seems to be possible to use a higher biomass to coal ratio if the two fuel categories are co-combusted in a oxy-fuel unit without having alkali related problems to the same extent as is expected for air combustion.
Aim – Background – Project description – Results - Summary
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Acknowledgement
• Tomas Leffler, the division of Combustion Physics at Lund University.Gratefully acknowledged for his contribution to this work providing both instrumentation and knowledge regarding alkali measurements.
• The Swedish research councilAcknowledged for their financial support
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Thank you!
P.S. Reduced maintenance is always appreciated!
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Alkali sulphation in flames
Thomas Ekvall(thomas.ekvall@chalmers.se)
Project funded by The Swedish Research Council
Department of Energy and Environment, Division of Energy Technology, Chalmers University of Technology, Sweden
5th Meeting of the IEAGHG International Oxyfuel Combustion Research Network – 27th -30th October 2015, Wuhan, China
mailto:thomas.ekvall@chalmers.se
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