Diffusion of Chemicals into Green Wood
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Mass transport of chemicals into wood is important in kraft pulping. This thesis models small wood particles as cylinders and monitors how tritiated water and sulfide diffuse into the water-filled pores. Tritiated water diffusion is Fickian and diffuses completely into the water contained in the wood. Tortuosity values of the aspen and pine are tabulated. As particle size decreases, the tortuosity of the particles increases. As sulfide diffuses into wood, it is occluded from some water filled areas. Charge exclusion is a possible explanation for this. Sulfide and hydroxide transport into wood chips was displayed using indicators for each component. Pictures show sulfide ingress into the chip core faster, thus confirming the diffusion results. Fractionated sawdust was pulped to determine particle size effect on cooking and pulp properties.