A low capital method for silicon interference in bamboo kraft pulping alkaline recovery system

The problem posed by the silicon interference in bamboo pulp black liquor has been troubling bamboo pulp mills as well as hindering the development of non-wood pulp mills. Silica is separated from bamboo pulp black liquor by acid precipitation, accompanied by the sediment of lignin, which is disadvantageous to alkali recovery system. The amount of carboxylate increases through the oxidation of lignin, and the solubility of lignin increases. So the lignin precipitation and the removal of silica can be quantified by the combination of acidification and light oxidation. For solving the problem, we separate the silicon in the black liquor through oxygen oxidation and carbon dioxide acidification without affecting the stability of the alkali recovery system. TG, combustion calorific value and visible light absorption are tested after oxidation and acidification. Finally, by comparing with the mature pulp black liquid alkali recovery system, it is concluded that when taking economic capital into consideration, oxidizing to pH 12.45(at 80 degrees C) and acidifying to pH 10 (at 50 degrees C) are suitable for our goal. In this case, the silicon removal rate reaches 76.41 wt%; the amount of separated lignin is 17.58 wt% and the calorific value loss of black liquor reaches 26.47%.

Automated summary

The interference of silicon in bamboo pulp black liquor has been a problem for pulp mills, hindering the development of non-wood pulp mills. Silica is separated from black liquor through acid precipitation, which is disadvantageous to the alkali recovery system due to lignin sedimentation. By increasing the carboxylate amount through lignin oxidation, the solubility of lignin also increases. The silicon removal and lignin separation can be quantified by combining acidification and light oxidation.