The role of surfactants in the neutral sulfite pulping process was studied. The mass transfer of the pulping liquor into the wood as well as the interfacial properties between the liquor and wood, and the changes in the properties due to the surfactants present in the liquor were investigated. / A mixture of anionic and nonionic surfactants, effective in neutral sulfite pulping, was selected during the pulping experiments. Due to the surfactants present in the pulping liquor, the reaction rate of carbohydrate degradation was found to be considerably lower when compared with those of control without surfactants. / The surfactant mixture was observed to accelerate the deresination process during the pulping heat-up period. However, the dissolved extractives diffused out of the wood chips at slower rate when the surfactants were present. This was a result of more micelles being formed by surfactants and dissolved extractives which also are surfactants. / The sodium sulfite concentration profiles in wood after cooking indicated that the surfactant mixture could increase the diffusion process by improving the swelling of the lignin fraction. It was concluded that surfactants could modify the mass transfer mechanism. However, the experiments also indicated that the diffusion of surfactants was rather slow. Compared to the cooks with the surfactants, the reaction rates of the control cooks were found to be higher. As more of the wood components got dissolved, the more porous wood structure was developed during pulping, which explains, why after certain period of time, the sodium sulfite content of the control cook was higher. / In order to obtain quantitative information on the diffusion process, the chemical profiles in wood were simulated using the diffusion model with simultaneous reactions. The simulated chemical distribution curve was adjusted to fit the measured ones by changing the effective diffusivity. / Measurements of a dynamic contact angle, as well as a diameter and volume of a droplet of pulping liquor were carried out to obtain an in-depth understanding of the surfactants behavior in pulping process. The results show that the surfactants did not improve the spreading wetting but improved the absorption. This phenomenon could not be simply explained as a function of capillary pressure, in fact, the liquor containing surfactants must have been able to disperse the air inside the wood structure and therefore to reduce the resistance of air to penetration and diffusion. / Finally, it was found that surfactants improved the pulp yield as a result of a slower reaction rate and faster diffusion rate, as less lignin condensation and carbohydrate degradation was observed.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.84853 |
| Date | January 2003 |
| Creators | Wei, Hongmei |
| Contributors | Kubes, G. J. (advisor), Berk, D. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002149947, proquestno: AAINQ98386, Theses scanned by UMI/ProQuest. |
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