Dynamic Viscoelasticity of Kraft Black Liquor at a High Dry Solid Content with the Addition of Sodium Aluminate

Xiaopeng Yue, Xin Du, Yongjian Xu


Black liquor is not only a by-product of the papermaking industry but also an energy source that is often burned at a high solids content in a recovery furnace because of its high combustion efficiency and stability. However, the silicon content of bamboo kraft black liquor (BKBL) is much higher than that of softwood kraft black liquor, and the presence of silicon causes serious problems in the recovery cycle. Sodium aluminate, when used as a desilicating agent during combustion, has an excellent effect on the removal of silicon from BKBL. In this work, the dynamic viscoelasticity of BKBL with the addition of sodium aluminate was studied using a rotational rheometer. The results indicated that the BKBL was a pseudo-plastic fluid. A power-law model and the Cross model accurately described the relationship between the dynamic viscosity and angular frequency. The zero shear rate viscosity of BKBL was relatively high, even at a high temperature. The addition of sodium aluminate increased the viscosity of BKBL when the loading was 1.5 wt.%, but it had the opposite effect when its loading was 0.5 wt.%. With an increase in the angular frequency, the effect of sodium aluminate on the viscosity became less apparent.


Dynamic viscoelasticity; Black liquor; Complex viscosity; Dynamic viscosity

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