Anion-Exchange Resin-Based Desulfurization and Dechlorination of Spent Sorbent Material

Abstract

Emissions of acid gases such as SO₂ and HCI/CI₂ from energy conversion or waste incineration facilities are unacceptable. Under the various regulations, the emissions of such acid gases are regulated by the U.S. Environmental Protection Agency (EPA). Alkali metal sorbents can remove these acid gases more efficiently than the lime/limestone type sorbents used in the conventional flue gas desulfurization (FGD) systems. However, the resulting alkali metal sulfate and chloride are unsuitable for landfill disposal because they are water-soluble and can potentially leach into groundwater, altering the soil pH. Replacing the (virgin) sorbent material is expensive. Hence, it is desirable that the spent sorbent materials obtained from such emissions control systems be converted to sulfur- and chlorine-free forms, so that they can be reused. The weak-base, anionexchange resin-based desulfurization concept, developed and tested at the University of Tennessee Space Institute (UTSI), can also simultaneously remove sulfur- and chlorine- containing species from such spent sorbent materials. Under the U.S. Department of Energy’s (DOE) sponsorship, bench scale studies have been carried out at UTSI to evaluate the feasibility of removing sulfur- and chlorine-containing species using this resin-based concept. Efforts have also been made to enhance the candidate resins’ performance by carrying out the resin exhaustion step under CO₂ static pressure and by using suitable pH buffering agents, such as low-molecular weight organic acids. Preliminary cost estimates for a regeneration scheme employing reactivated alkali metal-based spent sorbent material using the ion-exchange resin-based concept seem attractive and comparable to currently available options. After further development, this low-cost, simple process can be easily integrated into alkali metal sorbent-based flue gas desulfurization and acid gas emission control systems.