Specific resistance and adsorption performance of acid-modified fly ash for escaped ammonia in flue gas

Escaped ammonia emission following Selective Catalytic Reduction denitrification significantly influences subse-quent flue gas treatment processes. This study investigates the adsorption capabilities of acid-modified fly ash concerning escaped ammonia (NH3) and its consequential impact on specific resistance. Furthermore, the adsorption mechanism of acid-modified fly ash on NH3 was explained. Acid activation facilitated the dissolution of a portion of Fe and Al constituents within the fly ash, the contents of Fe and Al in SFA decrease by 4.91% and 5.64%, respectively. In addition, the specific surface area and porosity of fly ash are obviously improved. The specific surface areas of HFA and SFA increased from 1.83 (OFA) to 4.69 and 7.71 m2/g, respectively. Adsorption kinetics adhered to the pseudo-first-order model. SFA showed the best adsorption performance, with NH3 adsorption up to 10.65 mg/g, which was 4.27 times higher than OFA. The creation of a surface liquid film during NH3 adsorption led to decreased specific resistance values across all fly ash samples after-adsorption. The highest specific resistance values recorded for original fly ash (OFA), hydrochloric acid-modified fly ash (HFA) and sulfuric acid-modified fly ash (SFA) were 6.21 x 1012, 3.37 x 1011 and 5.02 x 1010 omega & sdot;cm, respectively. Sulfuric acid activation makes fly ash have stronger adsorption capacity for escaping ammonia, and SFA maintains good specific resistance character-istics, which has good application prospects in electrostatic precipitation and air pollution control.