Removal of elemental mercury from Bayer stack gases using sulfur-impregnated activated carbons

The Bayer refining process can generate flue gases that contain elemental mercury, volatile organic carbons (VOCs) and water vapor creating a unique and challenging environment for the development of mercury adsorption technologies. Three sulfur impregnated activated carbons (SIACs) were tested under a range of conditions to assess each as a potential candidate for use in pilot scale fixed bed adsorber trials.All materials tested met or exceeded the mercury loading capacities specified by the respective suppliers and were therefore not significantly impeded by the addition of toluene into the gas phase. Of the SIACs, Pica/Alcoa Selexorb HG showed the lowest affinity to adsorption of organic vapors (toluene) and the highest affinity to the adsorption of mercury vapors (over a wide range of operating temperatures). Alcoa/Pica Selexorb HG is the preferable sulfur impregnated carbon for the removal of mercury vapors and is recommended for use in pilot trials.

► Vapor mixtures were tested for adsorption by carbon and sulfur-impregnated carbons.
► Equilibrium Hg adsorption complements column adsorption analyses.
► Adsorbents tested met or exceeded supplier’s specifications.
► VOC addition to Hg vapor had negligible effect adsorbent Hg capacity or efficiency.
► Rapid VOC breakthrough in packed beds indicated weak interaction with sulfur.