Kraft green liquor pulping of Douglas-fir for corrugating medium Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/8s45qc86f

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  • Douglas-fir wood chips from Oregon were pulped with kraft green liquor to produce semi-chemical pulps with properties suitable for the manufacture of corrugating medium. The effects of five cooking variables were studied, chemical charge, chip size, bark content of chips, pulping temperature, and liquor sulfidity. The combinations of levels of these five independent variables were chosen according to an incomplete block design, which allowed a maximum amount of statistical information to be obtained from only 30 individual cooks. Pulping properties studied were pulp yield, total solids of the waste liquor, pH of the waste liquor, the hypo number test of the pulp, and such pulp strength properties as Concora crush strength, tensile, burst, tear, and stiffness. Chemical charge is the most important single variable affecting pulp yield, tensile strength, and Concora strength, whereas the sulfidity does not affect the pulp yield but does affect the tensile and Concora strengths. Cooking temperature, bark content, and chip size have less significant effects on pulp yields and pulp strength properties. Green liquor pulps have distinctly darker colors than neutral sulfite pulps from the same wood species, and the former pulp forms denser sheets than the latter. Generally speaking, green liquor semi-chemical Douglas-fir pulps are equivalent to or slightly lower in quality than other commercial semi-chemical pulps in Concora strength, but equal or slightly superior to them in tensile and bursting strengths. The deficiency in Concora strength can be overcome with increased refining, and the slightly higher pulp yield and elimination of the causticizing step make the green liquor semi-chemical process more attractive for corrugating medium.
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