Detailed modeling of the kraft pulping chemistry: carbohydrate reactions

Abstract

The article introduces a detailed model for carbohydrate chemistry in kraft pulping. This article is continuation to the modeling work carried out for hot water extraction and chemical pulp bleaching. The model includes galactoglucomannan, xylan, and cellulose acid-base equilibria, in addition to peeling, stopping, and alkaline hydrolysis reactions of the same carbohydrates, as well as hexenuronic acid formation and degradation reactions. The Arrhenius parameters were applied from the literature or regressed against experimental data in the present study. The model is very successful in predicting the experimental data of carbohydrate reactions during kraft pulping. Many features of the pulping-related model can be applied to specific fractionation chemistry considerations. The detailed knowledge on carbohydrates composition at any stage of pulping gives possibility for further development of biorefinery cases based on kraft pulping, such as biofuel and chemicals production.

Inferential Model Predictive Control of Continuous Pulping under Grade Transition

“…Therefore, a significant decrease in Kappa number was observed in the cooking zone (5 m ≤ z < 15 m), driven mainly by the elevated free-liquor phase temperature; the temperature increase in this zone was a result of the circulation streams from the upper and lower heaters, which can be seen by the two temperature peaks at z = 5 m and z = 10 m in Figure . Additionally, the free-liquor temperature slightly increased owing to the exothermic nature of the delignification reaction. , Since the delignification reaction was quenched by the flow of cool washing liquor in the washing zone ( z ≥ 15 m), the Kappa number remains constant.…”

“…Therefore, inferential control strategies (e.g., soft sensor) are employed to estimate primary quality variables through the use of secondary measurements such as cooking liquor concentrations which are available at every 5–10 min without measurement delay. ,, Accordingly, there has been a need for a high-fidelity process model for the design of a soft sensor. In this regard, various pulping process models have been proposed to accurately elucidate the nonlinear reaction kinetics. ,,,− Specifically, triggered by the H-factor model, two widely used dynamic models were developed: the Purdue model and the 3-stage model . Developed by Smith and Williams and extended by other researchers, ,, the Purdue model divides the entire system into three phases and considers five components for the solid phase and six components for the entrapped-liquor and free-liquor phases.…”

Pretreatment with Sodium Methyl Mercaptide Increases Carbohydrate Yield during Kraft Pulping

“…To obtain a better fundamental understanding of the molecular basis for the experimentally observed differences in stabilization of cellulose and GGM by SMM pretreatment, we carried out a computational analysis of relevant model systems. Numerous kinetic models have been developed to predict carbohydrate degradation during pulping. ,,, While useful for predicting the effect of various kinetic parameters on product distributions, such models do not provide the molecular level insight critical to developing actionable hypotheses for pulp yield enhancement. Molecular dynamics studies have investigated various aspects of carbohydrate conformations and dynamics in aqueous solution at the molecular scale, ,− but detailed molecular-scale insight under kraft pulping conditions has not been demonstrated.…”

Chemical and Structural Changes of Ozonated Empty Fruit Bunch (EFB) in a Ribbon-Mixer Reactor

“…It is clearly observed that the delignification has three visible stages [39]: (1) Initial, (2) Bulk, and (3) Residual. At the beginning of the reaction time, the delignification occurred very fast.…”