Evaluation of the SuperBatch TM pulping process for Pinus taeda

Author(s)

Fernando Soares Ribeiro de Vasconcelos

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2005-12-07
• Advisor: Francides Gomes da Silva Junior

Abstract

In this research was evaluated the efficiency of the SuperBatchTM kraft pulping process in comparison to conventional pulping process as well as the effects of the anthraquinone (AQ), aiming the production of unbleachable grades (kappa number 58 ± 2) and bleachable grades (kappa number 28 ± 2) for Pinus taeda with 9 years old, the main specie used in Brazil to produce long fiber pulp. A study of the impregnation phase in the conventional cooking was performed, where the heating up time was variable and the time at the maximum temperature was adjusted to a H factor of 2300. It was also studied the evolution of the delignification during the SuperBatchTM and conventional process. The pulping results show that in the SuperBatchTM process, regarding unbleachable pulps, a smaller amount of rejects was produced in comparison to conventional process; the addition of anthraquinone was efficient to reduce the kappa number in the SuperBatchTM process, however without significant gains of selectivity; in the conventional process with the addition of anthraquinone a reduction of 0,5 percentual points in the initial active alkali was possible. Considering the bleachable grade, the SuperBatchTM process had a greater selectivity in comparison to conventional process and in both process the addition of anthraquinone was not efficient. During the evaluation of the impregnation phase in the conventional process, considering unbleachable grade, the adoption of a longer time during the heating up phase results in a reduction of the rejects and an increase in the screened yield; to bleachable grades, a longer heating up time in the kraft process results in an increase of the screened yield while in the kraft-AQ process the parameters analyzed were similar in all heating up times studied, showing that the anthraquinone was efficient to compensate drastic conditions in the pulping process. Finally, in the study of the delignification during the cooking, the logistic mathematical model developed showed a good adjustment with three phases identified for all the cases: (i) initial delignification phase when a small amount of lignin is removed, (ii) bulk delignification phase, when the intensity of delignification increase and most of the lignin is dissolved and a (iii) residual delignification phase, when the delignification is small again. In the SuperBatchTM process, regarding both kappa number grades, during the impregnation phase, practically did not happen any reaction between reagents and lignin; during the hot black liquor (HBL) about 25-30% of the lignin is dissolved, in the bulk phase about 50-60% of the lignin is removed. The addition of anthraquinone in the SuperBatchTM process, considering unbleachable grade, increased the intensity of the reactions with the lignin, resulting a faster delignification during the bulk delignification phase while in the production of bleachable grades it was not observed any catalytic effect for the anthraquinone, probably related to the high alkali charge used (AU)