Removal of elemental mercury from flue gas using red mud impregnated by KBr and KI reagent

In this work, the solid waste residue derived from the production of alumina, red mud, is modified by potassium halides impregnation, and is used to capture elemental mercury (Hg-0) from flue gas. The chemical and physical properties of materials are studied by X-ray diffraction (XRD), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET). A series of experiments are conducted in a fixed-bed reactor to study the effects of some key parameters such as loading value, reaction temperature and main flue gas components on Hg-0 removal. The reaction mechanism and kinetics model analysis of Hg-0 removal are also studied. The results indicate that the modification of potassium halides significantly improve the Hg-0 removal performance of red mud, and the KI modified red mud exhibits the highest Hg-0 removal efficiency. Increasing reaction temperature, loading value, O-2 concentration and NO concentration enhances Hg-0 removal. Increasing SO2 concentration greatly reduces Hg-0 capture. Water vapor has a dual effect on Hg-0 removal, which has an optimal concentration of 4%. The process of Hg-0 adsorption on modified red mud conforms to the pseudo-second order kinetic model.