A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Pulp and Paper Technology

Thesis (M.Sc.) - Asian Institute of Technology, 2009

The aim of this work was to study the effect of adding AQ, HEDP, digester additive A, pitch dispersant, surfactant A, surfactant B, Urea, MeOH and their combination into kraft pulping liquor. All cooks were performed under the same cooking conditions and same Eucalyptus cammeludensis chips which was originated from Thailand. These pulps produced from these cooking were compared in terms of yield, screen reject, residual alkali, kappa number and brightness and tensile index of unbleached hand sheets. Kraft process was modified by adding AQ, HEDP, digester additive A (with or without methanol) with different charges and the results showed an increase in pulp yield and reduction in kappa number. On the contrary, there was an increase in both yield and kappa when the kraft cook was modified by urea and combination of urea+methanol, urea+AQ. The most notable out come of yield increase was found from Urea + methanol kraft cooking and the value was 9.9%. The highest residual alkali increased 35.8% from AQ-kraft cook and 17.2% kappa number reduction was gained by the combination effect of AQ and methanol. The highest brightness also resulted from the same cook. Moreover, tear index was improved 51.9% by the addition of urea and methanol.