Characteristics of mercury desorption from sorbents at elevated temperatures

This study investigated the dynamic desorption characteristics of mercury d uring the thermal treatment of mercury-loaded sorbents at elevated temperat ures under fixed-bed operations. Experiments were carried out in a 25.4 mm ID quartz bed enclosed in an electric furnace. Elemental mercury and mercur ic chloride were tested with activated carbon and bauxite. The experimental results indicated that mercury desoption from sorbents was strongly affect ed by the desorption temperature and the mercury-sorbent pair. Elemental me rcury was observed to desorb faster than mercuric chloride and activated ca rbon appeared to have higher desorption limits than bauxite at low temperat ures. A kinetic model considering the mechanisms of surface equilibrium, po re diffusion and external mass transfer was proposed to simulate the observ ed desorption profiles. The model was found to describe reasonably well the experimental results. (C) 1999 Elsevier Science Ltd. All rights reserved.