THERMODYNAMICS AND KINETICS OF THE KRAFT CAUSTICIZING REACTION

A methodology for the calculation of the equilibrium of the causticizi ng reaction of pure sodium carbonate solutions at 100-degrees-C withou t any adjustable parameters is presented. The methodology is extended to compute the effect of sodium sulfide. The causticizing reaction was found to be slightly endothermic at 100-degrees-C. The caculated resu lts were found to be in good agreement with experimental data. An empi rical kinetic model for the causticizing reaction is also presented. T he model takes into account the variations in both green liquor compos ition and lime quality and can yield the causticizing efficiency direc tly. The calculated results of the causticizing efficiency were found to be in good agreement with experimental data from several Canadian p ulp mills and reflected the effect of the variation in lime quality.