Particle Formation During Black Liquor Char Bed Burning, 1998 International Chemical Recovery Conference Proceedings

The formation of particulate during the char burning stage of black liquor combustion was studied using a laboratory scale char bed reactor connected to a particulate collection system. The results show that significant quantities of submicron sized fume and l-to-100 µm sized particles, “ejecta”, form during char bed burning. The amount of fume shows an exponential-like increase with bed temperature, while the amount of ejecta increases markedly with temperature up to l000°C, but reaches an almost constant value at higher temperatures. The carbonate content in fume increases with bed temperature, while the sulfate, chloride, and potassium contents decrease. The composition of ejecta is close to that of an oxidized smelt and is consistent with a “mechanical” mechanism of formation for these particles. The large amount of ejecta found in this study suggests that these particles may contribute to the fouling and plugging of the superheater and generating bank in kraft recovery boilers.