Correlations for the viscosity of lignin lean black liquor

In this study, experimental results from earlier work on viscosity measurements of black liquors with different lignin contents were used to develop an empirical model describing viscosity as a function of temperature, dry content and concentration of lignin and hemicellulose. The liquors studied were taken from six different lignin extraction runs, according to the LignoBoost process, at different mills. The viscosity data was available at a wide range of temperature (40-130 degrees C) and dry content (30-70 w/w-%): this data was used to calculate the parameters in the model. Furthermore, one of the general correlations was developed by taking the concentrations of lignin and hemicellulose into account. The results of this study showed that a much better fitting of the model could be obtained by taking the influence of the organic content in the black liquor into account.