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Kraft pulping
Kraft pulping is a chemical pulping process that uses sodium hydroxide and sodium sulfide. There are two main types of reactions during kraft pulping - degradation reactions that break down lignin into smaller fragments that dissolve, and condensation reactions that join lignin fragments together and can cause precipitation. Degradation predominates early in kraft pulping while condensation reactions increase later. Carbohydrates like hemicellulose are also broken down during kraft pulping through reactions that change their structure.
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Kraft pulping
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- 2. pulping Chemical Soda Sulfite Sulfate Hybrid Chemi thermal mechanical pulp Neutralsulfite semi chemical Mechanical Groundwood Stone groundwood Thermal ground wood Pressurised ground wood Refiner Refiner mechanical pulp Thermal mechanical pulp Introduction
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- 5. Sulfite Proses • Veryaggressive • Removes more lignin sulfite + lignin -> lignosulfonate lignosulfonate is a high MW and soluble in water • Dissolve primary wall acidic condition • Dissolve hemicellulose change xylan -> xylose + fructose change glucomannan -> glucose + mannose • Acidic extractives remain in the fiber
- 6. Sulfate Process • Lessaggressive • Removes less lignin hydroluzed lignin, break down and cut to small piece (low MW) • Does NOT destroys primary wall • Does NOT destroy hemicellulose glucomannan -> glucoisosaccharinic acid + mannoisosccahrinic acid • Acidic extractives removed from the fiber
- 12. Reactions of ligninsduring kraft pulping can be divided into two categories: 1) degradation reactions which lead to the liberation of lignin fragments and ultimately to their dissolution, and 2) condensation reactions which increase the molecular size of lignin fragments and may result in their precipitation.
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- 25. Attempted Correlation Betweenthe Main Degradation Reactions and Particular Phases of Kraft Pulping
- 28. Tentative Description ofthe Course of Delignification During Kraft Pulping
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Editor's Notes
- #6 Big grindstone revolving around a big log presed against it as the grindstone turns around generates friction against the log the