Kraft pulping selectivity

Sulfite pulps have properties that are desirable for tissues and top quaHty, fine papers. Because sulfite pulping is not as versatile as kraft pulping, various options have been developed, and the choice of a specific process is dependent on individual mill situations. The unbleached pulp has high (60+) brightness compared to kraft pulp and is easily bleached. However, it is limited to select wood species. The heartwood of pine, Douglas fir, and cedars are not easily pulped. Additionally, pulps produced from hardwood have limited economic value because of low strength. 

Complex manufacturing systems, such as an unbleached Kraft pulp plant (Fig. 9), are almost always characterized by some type of internal structure, composed of a number of interconnected subsystems with their own data collection and decisionmaking responsibilities. This raises a number of additional issues, not addressed in previous sections. For instance, if the learning methodology described in Section VI is applied to the digester module of a pulp plant (Fig. 9), it is possible for the final selected solution, to include ranges of desired values of sulfidity... 

This poses a question concerning deacidification. If a deacidification procedure does not remove aluminum from the cellulose carboxyls, will the paper have the stability that one would expect from a paper with an alkaline filler In an attempt to answer this question, a series of hand-sheets was made from a hardwood kraft pulp. This pulp was selected because (a) it had a carboxyl content of 5.75 mmol/100 g pulp, which is similar to that of some old papers (b) it was easy to beat in a laboratory beater and (c) the physical properties of the handsheets were in the "old... 

Yao KW, Kennedy KJ, Tam CM, and Hazlett JD. Pre-treatment of kraft pulp bleach plant effluent by selected ultrafiltration membranes. Can. J. Chem. Eng. 1994 72(6) 991-999. 

Fukagawa, N., Meshitsuka, G., and Ishizu, A. (1992) 2D NMR study of residual lignin in beech kraft pulp combined with selective cleavage with pivaloyl iodide. J. Wood Chem. Technol. 12(4), 425 45. 

FIGURE 10.3 A laboratory flow-through kraft cook of softwood with a lowered concentration of hydrosulfide ions present in the cooking liquor during the time interval of 60-105 min, after the start at 70°C, corresponding to a temperature interval of 130-170°C -H 5 min at 170°C. Pulping selectivity is measured as pulp viscosity as a function of kappa number. (Sjdblom, K., Mjdberg, J., and Hartler, N., Pap Puu, 65, 227-240, 1983.)... 

M Tenkanen, T Tamminen, B Hording. Investigation of Lignin-Carbohydrate Complexes in Kraft Pulps by Selective Enzymatic Treatments. App/ Microbiol Biotechnol 51 241-248, 1999. 

In comparison to chlorine (see the next section. Chlorine Bleaching Chemistry), chlorine dioxide has a much higher selectivity in its reactions with lignin, and in analogy to model experiments, oxidation is the major mode of reaction. This has been demonstrated by bleaching experiments of kraft pulp in which the prebleaching was... 

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