Novel Insight\ninto Lignin Degradation during Kraft\nCooking

Abstract

In\nthis study three different modeling approaches, with varying\nlevels of sophistication and complexity, on modeling kraft cooking\nkinetics have been investigated. In the first and second approaches,\nisothermal conditions were used by converting the heating and cooling\ntimes into isothermal time. In the third approach, real temperature\nand time were used. Donnan theory, accounting for the cation exchange\nproperty of the wood fibers, was used in the second and third approaches\nfor estimation of the cooking chemical concentrations in the fiber\nwall liquid, whereas in the first approach the cooking chemical concentrations\nin the bulk liquid phase were used. A modification of the Purdue model\nwas used for modeling the delignification kinetics. The parameters\nof the Purdue model were regressed both with Matlab (commercial software)\nand Kinfit (in-house software). All three regressions with different\nmodeling approaches provided very good fits to the experimental data.\nWhen Donnan theory and real temperature profiles (third approach)\nwere employed, the estimated reaction rates for the faster reacting\nlignin subcomponent in the Purdue model decreased at all temperatures.\nOn the other hand, the portion of the faster reacting component increased\nfrom 24% to 28%. In this way the third modeling approach mimics the\nreality in the most accurate way. Its implementation is more tedious,\nbut the model should have more predictive capabilities. Furthermore,\nthe effect of anthraquinone on kraft cooking kinetics was studied.