1. Pulping and Bleaching PSE 476: Lecture 111 Pulping and Bleaching PSE 476/Chem E 471 Lecture #11 Kraft Pulping Kinetics Lecture #11 Kraft Pulping Kinetics

2. Pulping and Bleaching PSE 476: Lecture 112 Agenda Effect of Variables on Kraft Pulping »Wood Species »Effective Alkali »Sulfidity Kraft Cooking Models Effect of Variables on Kraft Pulping »Wood Species »Effective Alkali »Sulfidity Kraft Cooking Models

3. Pulping and Bleaching PSE 476: Lecture 113 Kinetics? It is important as a pulping engineer to understand how to produce pulp with the desired properties in the most economical fashion. In order to do this, the kinetics of the pulping reactions need to be understood. Pulping variables: »Wood: species, source, etc (discussed previously) »Chemical charge (EA, sulfidity, liquor/wood, etc) » Temperature It is important as a pulping engineer to understand how to produce pulp with the desired properties in the most economical fashion. In order to do this, the kinetics of the pulping reactions need to be understood. Pulping variables: »Wood: species, source, etc (discussed previously) »Chemical charge (EA, sulfidity, liquor/wood, etc) » Temperature

4. Pulping and Bleaching PSE 476: Lecture 114 Kraft Pulping: Effect of Wood Species Notes

5. Pulping and Bleaching PSE 476: Lecture 115 Effect of Effective Alkali on Kraft Pulping (1) Simple story: if there is enough alkali present (with a certain level of sulfidity), pulp can be made. Increasing EA will increase rate and degree of delignification. Two ways of changing EA charge: »Increasing concentration of EA in white liquor »Increasing volume of White Liquor charged to digester Increasing EA using either method will increase the rate of delignification and change pulp properties. »Concentration change may have a larger effect than White Liquor volume. Simple story: if there is enough alkali present (with a certain level of sulfidity), pulp can be made. Increasing EA will increase rate and degree of delignification. Two ways of changing EA charge: »Increasing concentration of EA in white liquor »Increasing volume of White Liquor charged to digester Increasing EA using either method will increase the rate of delignification and change pulp properties. »Concentration change may have a larger effect than White Liquor volume. Notes

6. Pulping and Bleaching PSE 476: Lecture 116 Lignin Removal: Effect of Effective Alkali (2)

7. Pulping and Bleaching PSE 476: Lecture 117 Lignin Removal: Effect of Effective Alkali (3) Higher levels of EA results in more lignin removal but also lower screened pulp yield.

8. Pulping and Bleaching PSE 476: Lecture 118 Lignin Removal: Effect of Effective Alkali (4)

9. Pulping and Bleaching PSE 476: Lecture 119 Effect of Increasing Effective Alkali on Pulp Properties. In the kraft pulping of Scandinavian Pine, and increase in EA from 13.6% to 15.5% had the following effects: »Cooking time to yield cut in half. »Pulp yield at given kappa reduced. »Xylan content of pulp reduced while glucomannan content was increased. -Brightness increased. -Longer beating time to reached CSF. -Pulp strength properties (tear, breaking length,etc). changed. In the kraft pulping of Scandinavian Pine, and increase in EA from 13.6% to 15.5% had the following effects: »Cooking time to yield cut in half. »Pulp yield at given kappa reduced. »Xylan content of pulp reduced while glucomannan content was increased. -Brightness increased. -Longer beating time to reached CSF. -Pulp strength properties (tear, breaking length,etc). changed.

10. Pulping and Bleaching PSE 476: Lecture 1110 Removal of Glucomannans: Effect of Effective Alkali Why doesn’t EA affect glucomannan removal?

11. Pulping and Bleaching PSE 476: Lecture 1111 Removal of Xylans: Effect of Effective Alkali Why does EA affect xylan removal?

12. Pulping and Bleaching PSE 476: Lecture 1112 Lignin Removal: Effect of Sulfidity Sulfidity effect zero order in initial delignification (this means that changing sulfidity has no effect on initial rate) »Sulfidity is important during bulk delignification »Effects final lignin/carbohydrate ratio -HS - does not react with carbohydrates Sulfidity effect zero order in initial delignification (this means that changing sulfidity has no effect on initial rate) »Sulfidity is important during bulk delignification »Effects final lignin/carbohydrate ratio -HS - does not react with carbohydrates

13. Pulping and Bleaching PSE 476: Lecture 1113 Kraft Pulping Kinetics Lignin Removal: Effect of Sulfidity

14. Pulping and Bleaching PSE 476: Lecture 1114 Kraft Pulping Kinetics Kinetic Models Reaction models have been developed which simulate the pulping process. Models range from simple to quite complex. »Typically use the following reaction variables: -Time, Temperature, Alkali, Sulfidity, Liquor/Wood, Etc Models roughly derived from the following expression: Reaction models have been developed which simulate the pulping process. Models range from simple to quite complex. »Typically use the following reaction variables: -Time, Temperature, Alkali, Sulfidity, Liquor/Wood, Etc Models roughly derived from the following expression: dL dt = k[Lignin] a [OH - ] b [HS - ] c [other variables] d