Determination of Alkali and Sulfite Ratios in Paper Pulp Produced from Sorghum Stalks via the Kraft Method

Ayhan Gençer, Ceyda Hatıl


Paper pulp was produced by the kraft method using sorghum (Sorghum bicolor × S. bicolor sudanense) as the fibrous raw material. Two groups were cooked using active alkali at 10% and 14%. For each group, five sulfite ratios (0, 4, 8, 12, and 16%) were used, making a total of 10 different groups that were cooked. A literature study was conducted to determine the cooking temperature, the time needed to reach the maximum temperature, and the duration of cooking time at the maximum temperature. A total of 30 batches of paper were obtained from pulps without beating and from pulps beaten at values of 35 ± 2 °SR and 50 ± 2 °SR (Schopper Riegler) freeness. The aim was to determine the most suitable alkali and sulfite ratios by conducting standard tests for the yield, kappa number, and viscosity of the screened pulps and for the papers obtained from these pulps. The highest screened yield of cooked pulp was obtained under conditions of 14% active alkali and 12% sulfite. Since the mechanical properties of the paper obtained from this pulp were satisfactory when compared with those in the literature, it was concluded that these ratios could be recommended as a condition for cooking.


Sorghum sudanense; Kraft method; Alkali-sulfidity ratio; Pulp yield; Paper production

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