Capture of heavy metals by sorbents in incineration flue gas

The emission of heavy metals can be controlled by injecting solid sorbents into the flue during incineration processes. Feed waste elemental compositi ons and types of sorbents influence the controlling efficiency of the sorbe nts for heavy metal compounds. The objective of this work is to experimenta lly study the controlling efficiency of different sorbents for heavy metals in the flue of an incineration system, and study the effects of feed waste composition on the controlling efficiency of sorbents. The investigated he avy metals are Pb, Cd, Cu and Cr. The operating parameters evaluated includ ed: (1) different sorbents (kaolinite, limestone, aluminum oxide, and water ); (2) the feed waste contained organic chloride (PVC); (3) the feed waste contained inorganic chloride (NaCl); (4) the feed waste contained sulfate ( Na2SO4); (5) comparing the controlling efficiency of sorbents used in the c ombustion chamber and injected in the flue of an incineration system. Exper imental results indicated that the control efficiency of the four sorbents for heavy metals under various feed waste composition follows the sequence of limestone > water > kaolinite > aluminum or;ide. The best sorbent for th e four heavy metals is limestone, especially as the feed waste contained or ganic chloride PVC, because limestone slurry provides a lot of calcium and alkali to react with the metal chlorides and acid gas. The presence of inor ganic chloride NaCl and sulfate Na2SO4 in the feed waste is helpful to incr ease the capture efficiency of the sorbents for heavy metals. By comparison , the capture efficiency of the sorbent injected in the flue is lower than that added in the combustion chamber. (C) 1999 Published by Elsevier Scienc e B,V. All rights reserved.