Effect of urea on fly ash PCDD/F concentrations in different particle sizes

The effect of urea as an inhibitor for reducing polychlorinated dibenzo-p-d ioxin and dibenzofuran (PCDD/F) concentrations in flue gases was studied in a pilot scale plant, together with the effect on the particle size distrib ution of these compounds. Total PCDD/F concentrations decreased by a maximu m of 74%, the decrease being greatest for the most highly (octa-) chlorinat ed isomers. The PCDD/F reduction affected all the particle size classes whe n an adequate amount of urea was used (1% of the fuel input), which indicat es that inhibition, unlike formation, is independent of the fly ash particl e size distribution. (C) 2001 Elsevier Science Ltd. All rights reserved.