Study of Recovery Boiler Fouling Tendency in Low-Load High-Solid Operations, 2000 Engineering Conference Proceedings

K. Janka, A. Raukola, J. Wallén, S. H. Kochesfahani, G.B. Elton, K. Matzdorf--A study was performed on a kraft recovery boiler firing a black liquor dry solids content of about 80% under an exceptionally low firing load condition (40% MCR). The objectives were to evaluate the boiler fouling tendency and emissions under the current operating condition, and to determine how they change as the firing load increases to about 60% MCR or the solids content decreases to about 70%.

The results show that the amount and the carbonate content of dust increase with an increase in lower furnace temperature, whereas the sulfate, potassium, and chloride contents decrease. This study is the first to show that the chloride enrichment factor in dust decreases with increasing boiler load or the liquor solid content. While the boiler load and the liquor solid content both affect the quantity and composition of dust, data suggest that the effect of solid content is stronger. Therefore, high solids firing may increase the dust quantity and carbonate content to such extent that it binds the majority of SO2 in the flue gas and eliminates SO2 emissions even at extremely low load conditions as those used in this boiler.