Industrial & Engineering Chemistry Research, Vol.58, No.1, 18-26, 2019
Adsorption of HCl on Calcined Ca and Zn Hydrotalcite-like Compounds (HTLs) at Medium-High Temperature in Flue Gas
The high level of HCl generated from municipal solid-waste incinerators at 350-650 degrees C is considered a primary chlorine source for emitted toxic polychlorinated dibenzodioxins and polychlorinated dibenzofurans. Herein, calcium (Ca) and zinc (Zn) hydrotalcite-like compounds (HTLs) were prepared to remove HCl at different reaction temperatures and initial HCl concentrations. The mechanism of the adsorption of HCl by the HTLs and calcined HTLs (HTOs) was investigated using thermogravimetric analysis, X-ray powder diffraction, scanning electron microscopy, and surface-area measurements. The Ca- and Zn-HTLs had similar structures and physicochemical properties. Both sorbents had good adsorption capacities for HCl that exceeded 90% over 456 min at 550 degrees C in an HCl concentration of 750 mg/g. The adsorption capacity of Zn-HTOs was better than that of Ca-HTOs at 350 degrees C. The removal efficiency of Ca-HTLs was higher than that of Zn-HTLs at temperatures above 550 degrees C. The Freundlich isotherm provided a good fit to the experimental data for the HTLs.