CaO hydrated with ethanol solution for flue gas HCl immobilization. Part II: Influences of gas components

Abstract

The injection of alkaline adsorbent into flue gas for HCl removal technology is greatly impacted by the complex flue gas components. The newly developed ethanol-modified Ca-based adsorbent was demonstrated a superior dechlorination performance. In this work, the effect of flue gas components on the dechlorination was comprehensively studied by experiments, micro-insight characterization and mechanism analyses. The results showed that the high initial HCl concentration boosts the reaction rate but lowers the Ca/Cl mole ratio. O2 promotes the HCl adsorption efficiency by impelling the reaction between HCl and adsorbent to generate Ca(ClO)2 that enhances the chlorination and converting CaClOH to CaO. The presence of SO2 and CO2 hinders the removal of HCl in both physical and chemical aspects. The product layers of CaSO3 and CaCO3 may cover the adsorbent active sites that deteriorates the pore structure and seriously inhibits the adsorption of HCl on the adsorbent surface and prevents mass diffusion into the inner pores. It was discovered that HCl, SO2 and CO2 have an affinity to the Ca site, so there exists nonnegligible competitive adsorption between them that reduces the number of basic sites to which HCl can adhere. The HCl removal efficiency falls from 72.33% to 41.34% as SO2 concentration rises from 0 ppm to 1600 ppm. While it decreases from 72.33% to 51.17% as CO2 concentration changes from 0% to 20%.