Modeling of kraft liquors properties and applications to process simulations

A model of kraft liquor properties (BPR, density, heat capacity and causticizing equilibrium constant) which takes into account the concentration of major species has been developed. It is based on the semi-empirical approach developed by Chen et al. (Electrolyte NTRL Model) and has been implanted in the ASPEN PLUS package software. The model was validated by comparison between computed properties and those reported in the literature and good agreement was obtained. It was subsequently used for simulations of a multi-effect evaporator train for black liquor concentration and of the chemicals recovery loop. Again, good agreement was obtained with reported operating values. The domain of applicability of the model is still restricted because of lack of availability of interaction parameters between some pairs of key components (lignin principally). Determining those parameters will require laboratory experimentation.