Competition for Sodium and Toxic Metals Capture on Sorbents

Abstract

The removal of toxic heavy metals by sorbents has been the focus of much recent research. In single metal/single sorbent systems, laboratory experiments have demonstrated capture of lead and cadmium by kaolinite and lime at high temperatures. However, practical systems (i.e., pulverized coal fired boilers) generally involve sodium as well as toxic metals and the amount of sodium usually exceeds that of the toxic metals. The purpose of this paper is to explore the effect of sodium on the capture of lead and cadmium by sorbents. Experiments were conducted in a 16 kW, 0.15 m ID, 6 m tall laboratory downflow furnace. Aqueous solutions of toxic metals and metal/sodium pairs were introduced into the furnace through a natural gas flame via atomization and subse quent vaporization. For all experiments, the total metal/sorbent equivalence ratio was maintained at 0.7. Approximately 0.5g/min of lime or kaolinite powder (mean particle diameter congruent 1.4 mu m) was injected along the furnace centerline in the post ...