Pilot-Scale Experimental Investigation on Dry Capture of Mercury and SO3 in Smelting Gas of Acid Making.

Abstract

In this study, a novel dry capture process utilizing a mixed adsorbent of ZnO and CuS was proposed for the simultaneous removal of Hg0 and SO3 in flue gas from zinc smelting, addressing severe mercury pollution and high SO3 concentrations. The experimental results showed that flue gas cooling caused the SO3 to transform into sulfuric acid mist, which changed the reaction mechanism from a gas-solid to a liquid-solid reaction and helped to improve the SO3 removal efficiency. Additionally, properly increasing the absorbent/SO3 molar ratio significantly improved the SO3 removal performance. However, excessive absorbent injection could cause aggregation and uneven dispersion of the absorbent particles in the flue gas, therefore impairing the effectiveness of SO3 capture. Under typical operating conditions (flue gas flow rate of 3500 m3/h, flue gas temperature of 180 °C, ZnO/SO3 molar ratio of 0.74, and residence time of 0.5 s), using a mixed absorbent of ZnO and CuS achieved an SO3 removal efficiency of up to 32.6%, and a total mercury capture at 43.2%, of which the Hg0 removal attained a remarkable 76.3%. These results preliminarily confirm the feasibility of the dry capture technology for simultaneous removal of SO3 and mercury, laying the foundation for further application and promotion.