PREVENTION OF POLYCHLORINATED DIBENZO-P-DIOXINS DIBENZOFURANS FORMATION ON MUNICIPAL WASTE INCINERATOR FLY-ASH USING NITROGEN AND SULFUR-COMPOUNDS/

Formation of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorina ted dibenzofurans on incinerator fly ash can be reduced under laborato ry conditions by the addition of ethylenediaminetetraacetic acid (EDTA ), nitrilotriacetic acid (NTA), or Na2S. With these compounds (inhibit ors), a reduction in formation of ca. 80-90% is achieved. The inhibito rs reduce the ratio of [PCDD]:[PCDF] formed, suggesting that more than one pathway for the formation from carbon exists. EDTA and Na2S reduc e the degree of chlorination of PCDD; for PCDF, the same effect is see n with Na2S. No change was ever seen in the isomer distribution within homologues as a result of the inhibitors added, in accordance with th e theory that these isomer distributions are thermodynamically control led. In additional experiments, NTA gave a good reduction with reactio n times of 30-60 min, at temperatures between 300 and 400 degrees C, a nd with concentrations in the reaction mixture of 2-10%. With HCl as a chlorinating agent, the inhibition by NTA is >50% for both PCDD and P CDF. These inhibitors show promising results to achieve the reduction of PCDD/F formation. The additional experiments with NTA show that thi s compound can reduce formation under various conditions, making it su itable for use in the post-combustion zone of an incinerator, where re action conditions will vary.