Thermal Removal of Mercury in Spent Powdered Activated Carbon from TOXECON Process

Abstract

This research developed and demonstrated a technology to liberate Hg adsorbed onto powdered activated carbon PAC by the TOXECON process using pilot-scale high temperature air slide HTAS and bench-scale thermogravimetric analyzer TGA . The HTAS removed 65, 83, and 92% of Hg captured with PAC when ran at 900°F, 1,000°F, and 1,200°F, respectively, while the TGA removed 46 and 100% of Hg at 800°F and 900°F, respectively. However, addition of CuO–Fe2O3 mixture and CuCl catalysts enhanced Hg removal and PAC regeneration at lower temperatures. CuO–Fe2O3 mixture performed better than CuCl in PAC regeneration. Scanning electron microscopy images and energy dispersive X-ray analysis show no change in PAC particle aggregation or chemical composition. Thermally treated sorbents had higher surface area and pore volume than the untreated samples indicating regeneration. The optimum temperature for PAC regeneration in the HTAS was 1,000°F. At this temperature, the regenerated sorbent had sufficient adsorption capacity similar to its virgin counterpart at 33.9% loss on ignition. Consequently, the regenerated PAC may be recycled back into the system by blending it with virgin PAC.