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High‐temperature adsorption of alkali vapors on solid sorbents
Author(s) -
Punjak W. A.,
Uberoi M.,
Shadman F.
Publication year - 1989
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690350714
Subject(s) - kaolinite , bauxite , alkali metal , sorbent , adsorption , chlorine , sorption , chemistry , desorption , flue gas , chemical engineering , diffusion , inorganic chemistry , aluminosilicate , exothermic reaction , mineralogy , organic chemistry , catalysis , thermodynamics , physics , engineering
Abstract Vapors of alkali metal compounds can be removed from coal combustion and gasification flue gases using high‐temperature aluminosilicate sorbents. The fundamentals of alkali adsorption on kaolinite, bauxite, and emathlite are compared and analyzed both experimentally and through theoretical modeling. The results show that the process is not a simple physical condensation, but a complex combination of diffusion and reaction. The kinetics of adsorption on these sorbents have similarities: the process is diffusion‐influenced, the rate decreases with time, and there is a final saturation limit. There are, however, differences in reaction mechanisms leading to potentially different applications for each sorbent. In adsorbing alkali chloride vapors, kaolinite and emathlite release all the chlorine back to the gas phase while bauxite retains some of the chlorine. Moreover, the products of reaction with emathlite have a melting point significantly lower than those for kaolinite and bauxite. Therefore, emathlite is more suitable for lower‐temperature sorption systems downstream of the combustors/gasifiers, while kaolinite and bauxite are suitable as in ‐ situ additives.