Rheology of Eucalyptus Globulus Kraft Black Liquor

Abstract

Black liquor is the major by-product and biomass fuel of pulp mills, and the understanding of its thermophysical properties is essential for the improvement of the design and the operation of chemical recovery processes. In this work, the rheological behaviour of industrial samples of Eucalyptus globulus black liquor was investigated to study the influence of solids content ranging from 13 % for the white liquor sample, and from 30 to 65 % of dissolved solids for the black liquors, and of temperature from 298.15 to 338.15 K, covering shear rates from 0 to 1200 s-1. The black liquor showed a complex non-Newtonian behaviour, presenting at low shear rates a pseudoplastic behaviour, followed by a viscosity Newtonian plateau. The modified Quemada model gives an expression applicable to all the shear rate range, which was used to describe the flow curves for the viscosity of E. globulus black liquors samples. Moreover, a correlation based on a VTF model with parameters dependent on solids content was successfully developed for the viscosity data of the Newtonian plateau.

Keywords

• viscosity
• black liquor
• eucalyptus globulus
• rheological model
• shear thinning