The effect of Kaolinite’s structure on migration and release characteristics of sodium under oxy-fuel combustion condition

Abstract

Studying the adsorption properties of kaolinite on sodium chloride is of great significance for application of high sodium coal, but high concentration of steam in the oxy-fuel combustion atmosphere increases the uncertainty of this process. Moreover, under the corresponding condition, the research on the adsorption properties of sodium of kaolinite after calcination and intercalation-exfoliation is still scarce. Therefore, this paper carried out a study on sodium adsorption characteristics of kaolinite. This work further evaluated H2O influence on its Na retention ability via integrating experimental and DFT computational studies. As the proportion of additive increases, the sodium content in the ash also increases, but after the ratio exceeds 9%, the increase is not obvious. The kaolinite’s adsorption performance on sodium chloride has been significantly improved after the intercalation-exfoliation. In order to confirm this conclusion, this paper also carried out adsorption experiments using pure sodium chloride, and obtained similar results. Variations in the concentration of steam (0–45%) in the atmosphere have a strong effect on the adsorption of sodium chloride on the surface of kaolinite. Moreover, both acceleration and competition effects of H2O on surface-bound Na species were substantiated by DFT calculations·H2O showed a stronger interaction with the dehydroxylated surface, can promptly replenish the missing adsorption sites on the surface due to high temperature. The experimental results show that the dynamic balance can be achieved at 20%. However, H2O and sodium chloride compete with each other on the complete adsorption surface, which reduces the fixation of sodium.