Ultralow Emission of Dust, SOx, HCl, and NOx Using a Ceramic Catalytic Filter Tube

The simultaneous removal of dust, NOx, and SO2 in flue gas is a hot topic in the field of air pollution control. This work established a simultaneous removal system that could remove dust, NOx, HCl, and SO2 in a single step, which can be operated under a wide range of test conditions. Brunauer–Emmett–Teller analysis, X-ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscopy, and X-ray fluorescence technique were used to determine the pore structure and surface chemistry of the ceramic catalytic filter tube. The results indicated that SO2 and HCl could be removed using sodium bicarbonate (NaHCO3) or calcium hydroxide [Ca(OH)2] as the sorbent, whereas NOx is catalytically converted with NH3 and O2 to N2 and H2O. The denitrification efficiency is above 95% in the reaction temperature range of 260–350 °C. The removal efficiency of SO2 and HCl at a Ca/S molar ratio of 2.0 can reach up to 85 and 91%, respectively. Ca(OH)2 showed lower removal efficiency of SO2 and HCl compared with NaHCO3 as the sorbent. Injection of sorbents upstream of the ceramic catalytic filter tube can prevent potential poisoning to the catalyst by particulates or acid gas. Moreover, the ceramic catalytic filter tube consists of a fine-particulate filter membrane as the surface layer, V2O5 and WO3 as the medium layer, and alumosilicate fibers as the final support layer. The NH3–NOx reaction was conducted under dust-free and SOx-free atmospheres and without diffusion restriction, and thus has almost 100% utilization of the catalyst's intrinsic activity.