Effects of Combustion and Operating Conditions on Dioxin Emissions from Power Boilers Burning Salt-Laden Wood Waste, 2004 Paper Summit, Spring Technical & International Environmental Conference, (including Papermakers; Process Control, Electrical & Inform

This paper discusses the effects of combustion conditions on dioxin/furan emissions from pulp and paper power boilers burning salt-laden wood waste.

We found no correlation between dioxin/furan emissions and carbon monoxide emissions. A good correlation was, however, observed between dioxin/furan emissions and the concentration of stack polynuclear aromatic hydrocarbons (PAHs) in the absence of TDF addition. Thus, poor combustion conditions responsible for the formation of products of incomplete combustion (PICs), such as PAHs and dioxin/furan precursors, increase dioxin/furan emissions. On the other hand, ash carbon content increased with higher boiler load and/or low oxygen concentrations at the boiler exit, probably because of lower available residence times and insufficient excess air. Our findings are consistent with the current understanding that high ash carbon content generally favours heterogeneous reactions leading to either de novo synthesis of dioxins/furans or their direct formation from precursors. Using grate/lower furnace temperatures as a general measure of combustion performance in grate-fired boilers, we also found that a linear increase in the grate/lower furnace temperature produces an exponential decrease in dioxin/furan emissions. Although the extent of this effect appears to be mill-specific, particularly at low temperatures, the results indicate that increasing the combustion temperature may improve combustion performance.