Theoretical insights into the adsorption behaviors of gaseous mercury species on solid particles during the cooling process of coal gases

During the cooling process of coal-fired flue gas and coal-derived syngas, gaseous mercury species may adsorb onto the solid particles entrained in the gas streams. The strength of the interaction influences the extent of mercury pollution from coal utilization, and a fundamental understanding of the adsorption mechanisms can inform effective mercury control strategies. In this work, density functional theory (DFT) calculations are employed to investigate the adsorption behaviors of four gaseous mercury species (Hg 0 , HgO, HgCl 2 and HgS) on the surfaces of four minerals (quartz, corundum, anorthite and mullite). The study provides not only stable adsorption configurations and corresponding adsorption energies, but also evaluates the Gibbs free energy changes for selected configurations within a temperature range of 200–1500 °C. Moreover, the temperature stability ranges of the minerals are taken into account to draw more industrially relevant conclusions. Results indicate that Hg 0 exhibits negligible adsorption on all mineral surfaces studied, and HgCl 2 can only adsorbs onto the corundum surface within 800–1100 °C during the cooling process of flue gas. HgO and HgS are identified as the mercury species most likely to be captured under flue gas and syngas conditions, respectively. However, while quartz mainly provides effective adsorption sites for HgO, and multiple minerals—including quartz, corundum, and mullite—can serve as active surfaces for HgS adsorption.