High-temperature interactions of alkali vapors with solids during coal combustion and gasification
A temperature and concentration programmed reaction method is used to investigate the mechanism by which organically bound alkali is released from carbonaceous substrates. Vaporization of the alkali is preceded by reduction of oxygen-bearing groups during which CO is generated. A residual amount of alkali remains after complete reduction. This residual level is greater for potassium, indicating that potassium has stronger interactions with graphitic substrates that sodium. Other mineral substrates were exposed to high temperature alkali chloride vapors under both nitrogen and simulated flue gas atmospheres to investigate their potential application as sorbents for the removal of alkali from coal conversion flue gases. The compounds containing alumina and silica are found to readily adsorb alkali vapors and the minerals kaolinite, bauxite and emathlite are identified as promising alkali sorbents. The fundamentals of alkali adsorption on kaolinite, bauxite and emathlite are compared and analyzed both experimentally and through theoretical modeling. The experiments were performed in a microgravimetric reactor system; the sorbents were characterized before and after alkali adsorption using scanning Auger microscopy, X-ray diffraction analysis, mercury porosimetry and atomic emission spectrophotometry. The results show that the process is not a simple physical condensation, but a complex combination of several diffusion steps and reactions.
- Research Organization:
- Arizona Univ., Tucson, AZ (USA)
- OSTI ID:
- 6962817
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ADSORBENTS
PERFORMANCE TESTING
ALKALI METALS
ADSORPTION
BAUXITE
SORPTIVE PROPERTIES
KAOLINITE
AUGER ELECTRON SPECTROSCOPY
BENCH-SCALE EXPERIMENTS
CARBON MONOXIDE
CHEMICAL REACTIONS
CLEANING
COAL
COAL GASIFICATION
COMBUSTION
DIFFUSION
EMISSION SPECTROSCOPY
EVAPORATION
FLUE GAS
MATHEMATICAL MODELS
PHOTOMETRY
POROSIMETERS
POTASSIUM
REMOVAL
SODIUM
X-RAY DIFFRACTION
ALUMINIUM COMPOUNDS
ALUMINIUM ORES
ALUMINIUM SILICATES
CARBON COMPOUNDS
CARBON OXIDES
CARBONACEOUS MATERIALS
CHALCOGENIDES
COHERENT SCATTERING
DIFFRACTION
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUELS
GASEOUS WASTES
GASIFICATION
MATERIALS
MEASURING INSTRUMENTS
METALS
MINERALS
ORES
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SCATTERING
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SORPTION
SPECTROSCOPY
SURFACE PROPERTIES
TESTING
THERMOCHEMICAL PROCESSES
WASTES
014000* - Coal
Lignite
& Peat- Combustion
010404 - Coal
Lignite
& Peat- Gasification
010800 - Coal
Lignite
& Peat- Waste Management