Effects of Combustion and Operating Conditions on Dioxin Emissions from Power Boilers Burning Salt-Laden Wood Waste

摘要

This paper discusses the effects of combustion conditions on dioxin/furan emissions from pulp and paper powerrnboilers burning salt-laden wood waste.rnWe found no correlation between dioxin/furan emissions and carbon monoxide emissions. A good correlation was,rnhowever, observed between dioxin/furan emissions and the concentration of stack polynuclear aromaticrnhydrocarbons (PAHs) in the absence of TDF addition. Thus, poor combustion conditions responsible for thernformation of products of incomplete combustion (PICs), such as PAHs and dioxin/furan precursors, increaserndioxin/furan emissions. On the other hand, ash carbon content increased with higher boiler load and/or low oxygenrnconcentrations at the boiler exit, probably because of lower available residence times and insufficient excess air. Ourrnfindings are consistent with the current understanding that high ash carbon content generally favours heterogeneousrnreactions leading to either de novo synthesis of dioxins/furans or their direct formation from precursors. Usingrngrate/lower furnace temperatures as a general measure of combustion performance in grate-fired boilers, we alsornfound that a linear increase in the grate/lower furnace temperature produces an exponential decrease in dioxin/furanrnemissions. Although the extent of this effect appears to be mill-specific, particularly at low temperatures, the resultsrnindicate that increasing the combustion temperature may improve combustion performance.