Rheological Properties and Volumetric Isothermal Expansivity of Bamboo Kraft Black Liquor with high solid content and low lignin content

Abstract

Abstract The contradiction between the increasing demand for pulp and the insufficient capacity of existing alkali recovery system and the “silicon interference” problem of non-wood raw material pulping restrict the development of pulp and paper integration. Therefore, the key to improve pulp productivity is to improve the processing capacity of alkali recovery system and reduce the influence of “silicon interference”. In this study, a certain percentage of lignin in original bamboo Kraft black liquor (BKBL) was separated, and the residual BKBL with low lignin content was expected to be fed into the alkali recovery furnace to reduce the heat transfer load of the alkali recovery furnace. It can effectively improve the processing capacity of black liquor without a new alkali recovery system. With the decrease in lignin content, the rheological properties/volumetric isothermal expansivity (VIE) of BKBL change. When the lignin content was 70% remained in the original BKBL, the viscosity of BKBL with low lignin content is close to that of the passivated BKBL at the same solid content, the dynamic viscoelasticity is superior, and the VIE decreases by 57.2%. When the amount of desilication agent is 1.5%, the viscosity of BKBL with low lignin content did not change much, and the VIE increased sharply and was 62.7% higher than that of the passivated BKBL. Therefore, the combination of partial lignin separation process and sodium aluminate desilication process can effectively improve the ability of alkali recovery furnace to deal with BKBL and reduce the influence of “silicon interference’’.