Date of Award

5-2003

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Computer Engineering

Advisor

Adriaan R.P. van Heiningen

Second Committee Member

Joseph M. Genco

Third Committee Member

David J. Neivandt

Abstract

Wood as a raw material is generally the dominant cost factor for the production of chemical pulp. Therefore, an increase in pulp yield has a major impact on the competitiveness of a mill. In order to optimize pulp yield, for example by changing operating conditions, a mill must be able to monitor the yield accurately. However, an accurate "real-time" pulp yield measurement method is not available at the present time. Pulping yield is presently measured from the amount of pulp produced from a given quantity of wood consumed over a 3 to 6 month time frame. This method is obviously not suitable as a process optimization toll to maximize the pulp yield.

This thesis presents a yield measurement method based on a theoretical relationship between alkaline pulping yield and the mass fraction and degree of polymerization (DP) of cellulose in pulp. The relationship so-called UoM pulp yield prediction equation is derived from the cellulose mass balance and kinetics of the alkaline hydrolysis, peeling and stopping reactions of cellulose. It is validated for kraft, kraft-AQ, polysulfide and polysulfide-AQ pulping of Rock Maple, Yellow Birch, Poplar and Black Spruce.

Kraft cooks were performed at four sulfidities, 0, 7.5, 15 and 30%, and an effective alkali (EA) charge for the hard woods of 21% (as Na2O on o.d.(oven dried) wood) and 23% for Black Spruce. Four different polysulfide cooks at elemental sulfur additions of 0, 1, 2 and 4% (based on o.d wood) to 30% sulfidity liquors were performed on all four wood species at the same H-factor and EA (Effective Alkali) charges as that of the alkaline cooks. All haft and polysulfide cooks were also repeated the addition of 0.1% AQ based on 0.d. wood. UoM equation contains two parameters, (ΔDP)s and Yc,w, respectively the number of glucose units removed by secondary peeling and the cellulose mass fraction in pulp based on wood. These two parameters is not function of cooking conditions such as sulfidity but they are a function of the species used and the (ΔDP)s decreases with the addition of AQ.

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