COMBUSTION DIOXIN SUPPRESSION IN MUNICIPAL SOLID-WASTE INCINERATION WITH SULFUR ADDITIVES

Combustion of municipal solid waste (MSW) has - among other most probably more relevant sources - shown to produce PCDD/F's which in some countries has led to emission limits for an I-TE value as low as 0.1 ng/m3. "End-of-pipe" technology has so far only made available "add-on" filters and purification stages which may introduce additional safety problems (filter burn), increase down-time of the whole plant or induce over-sized design of the final stages due to incomplete knowledge of pre-dust-filter raw gas concentration of PCDD/F's. Since some theoretical conclusions have suggested a negative influence of elevated SO2-concentration with regard to dioxin/furan formation or re-formation 2 sets of very careful full-scale tests were carried out at a MSW incinerator whereby sulphur-containing Austrian lignite of similar physical fuel features compared to MSW (lower heating value, ash, humidity) was added in different quantities at constant feed-rate (t/h input) and compared with respect to their PCDD/F release. Results show a dramatic decrease from "usual" MSW incinerator dioxin levels in the order of 2.5 to nearly 10 ng TE/nm3 down to less than 1 ng TE/nm3 with addition of coal. Unlike other experiments which have not shown a significant decline of PFDD/F's in the raw gas and usually no decrease in PCDD/F concentration in the filter dust at all, our large scale tests have revealed a decrease in PCDD/F concentration in both gas and dust measurements, both before and after the dust filter as well as in the dust itself.