Particulate formation during black liquor char bed burning

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 quant ities of submicron-sized fume and 1-100 mu m sized particles, "ejecta", for m during char bed burning. The amount of fume shows a strong increase with bed temperature, while the amount of ejecta increases markedly with tempera ture LIP to 1000 degrees C, but reaches an almost constant value at higher temperatures. The carbonate content in fume increases with bed temperature, while the sulphate, chloride and potassium contents decrease. The composit ion 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 kraf t recovery boilers.