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Alkali Uptake, Release, and Speciation in Fluidized Beds Using Oxygen Carriers.
Viktor Andersson1, Jan B C Pettersson2, Thomas Allgurén1
1Department of Space, Earth and Environment, Division of Energy Technology, Chalmers University of Technology, Hörsalsvägen 7A, SE-412 96 Gothenburg, Sweden.
Energy & Fuels : an American Chemical Society Journal
|February 19, 2025
Summary
Advanced fuel conversion using CO2-neutral fuels requires understanding alkali chemistry. New methods reveal how oxygen carriers like ilmenite capture alkali, crucial for optimizing processes and controlling emissions from biomass and waste.
Area of Science:
- Combustion Chemistry and Thermodynamics
- Materials Science for Energy Applications
- Environmental Engineering and Emission Control
Background:
- CO2-neutral fuels (bioderived materials, waste) contain high alkali content, impacting combustion processes.
- Alkali compounds influence fuel conversion, tar cracking, but also cause fluidized bed agglomeration, ash deposition, and corrosion.
- Understanding alkali behavior is critical for scaling up advanced fuel conversion technologies.
Purpose of the Study:
- To develop and apply novel high-temperature alkali analysis methods for real-time characterization.
- To investigate alkali uptake, release, and speciation in fluidized beds with various oxygen carriers.
- To assess alkali emissions during biomass pyrolysis and their implications for fuel conversion.
Main Methods:
- Temperature-modulated surface ionization (TMSI) for real-time alkali speciation.
- Laboratory-scale reactor for continuous alkali vapor injection and emission monitoring.
- TMSI-thermogravimetric analysis (TGA) for simultaneous alkali release and mass loss monitoring.
Main Results:
- Ilmenite demonstrated high alkali chloride absorption (>90%), especially under reducing conditions.
- NaCl and KCl were primary emitted species during injections, with similar behavior for alkali sulfates.
- TMSI analysis of biomass pyrolysis showed KOH dominance at low temperatures, with KOH and NaOH from char/ash.
Conclusions:
- Developed TMSI and reactor methods provide real-time insights into high-temperature alkali chemistry.
- Oxygen carrier selection (e.g., ilmenite) significantly impacts alkali capture efficiency.
- Real-time characterization enables optimization of solid fuel conversion processes for diverse feedstocks.
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