Role of DeNOx Catalyst in PCDD/F Emission Reduction in Hazardous Waste Incineration (HWI) Plant

On the basis of nine periodical measurements, emissions of PCDD/F have been analysed. As a result, a correlation was detected between elevated PCDD/F emissions and operational problems with selective catalytic reduction (SCR) system. The air pollution control system (APCS) consisted of dry scrubbing system (mixture of active carbon and NaHCO3), fabric filter, DeNOx catalyst and wet scrubber. It was assumed that such a state-of-the-art system should be able to achieve dioxin emission limit of 0.1 ng Nm–3 I-TEQ, even without DeNOx catalyst. However, this expectation proved to be wrong. The presence of memory effect was recognized as the possible cause of elevated PCDD/F emissions. During normal operational periods presence of memory effect was not noticed, due to selective catalytic reduction system. With malfunction of DeNOx catalyst, this effect escalated, causing elevated PCDD/F emissions.