Graduate Thesis Or Dissertation
 

A study of deshive refining and its effects on high yield kraft pulp

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/cf95jf31b

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  • High yield unbleached kraft pulp for linerboard and bag paper was deshived in a PFI mill and a Bauer model 187 double disk refiner. Levels of plate gap, specific energy consumption, throughput rate, and stock consistency were varied to control PFI mill and Bauer 187 deshive refining. Shive content reductions were accurately monitored with the von Alf than shives analyzer. Mathematical models expressing post-treatment von Alf than values in terms of the four control variables were proposed for both refining machines. The PFI mill was an effective deshive refiner, but a poor modeling base due to the insensitive response of shive content to changes in processing conditions. The Bauer 187 performed well as a deshive refiner and model base. A strong relationship was found between post-treatment von Alfthan values and Bauer 187 control variables. A best model of Bauer 187 deshive refining was selected by the total square error criterion. That model involves a complex relationship of plate gap, stock consistency, and throughput rate, but, in general, reducing plate gap and increasing stock consistency reduces post-treatment shive contents. Conditions which optimized the efficiency of Bauer 187 deshive refining depended upon the desired shive content of processed pulp. Shive contents typical of industrially deshived pulp were most efficiently obtained by Bauer 187 deshive refining at 1.5 mm plate gap, 1.2 kg/minute throughput rate, and 12 percent consistency. The effects of deshive refining on pulp washing and strength development potential were also investigated. Chemical recovery from high yield kraft pulp was improved by Bauer 187 deshive refining. Washing improvements became more pronounced as pulp yield was increased. Pulp strength at common levels of CSF and sheet bulk generally benefited from Bauer 187 deshive refining. Strength differences between deshived and undeshived pulps were attributable to differences in the amount of strength development beating necessary to achieve specified bulks and freenesses.
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