The improvement of delignification ratio and yield in alkaline sulfite pulping

Alkaline sulfite-anthraquinone (ASA), alkaline sulfite-anthraquinone-ethanol (ASAE) and alkaline sulfite-anhraquinone-sodium borohydrate (ASAB) processes were selected for pulping using spruce and pine wood on 150 min and 180 min cooking time. It was determined that adding ethanol and sodium borohydrate to alkali sulfite-anthraquinone process had affirmative affect on delignification ratio and pulp yield. When viscosity of ASAE pulp obtained from spruce wood increased, that of ASAE pulp obtained from pine wood did not change, clearly. It was designated that he viscosity of ASAB pulp decreased. While the viscosity of ASA and ASAE pulp decreased extending cooking time, it was designated that the viscosity of ASAB pulp increased.It was determined that the strength properties of paper sheets obtained from spruce wood pulp were better than obtained from pine wood pulp. The strength properties of paper obtained from ASA spruce wood pulp better than those of ASAE and ASAB spruce wood pulp. When the tensile and burst index of paper obtained from ASAB pine wood pulp improved by increasing sodium borohydrate addition ratio on 180 minute cooking time, it was found that tear index did not changed, evidently.Whiteness and brightness of paper were decreased by adding ethanol and sodium borohydrate to ASA pulping process. It was established that opacity of paper sheets obtained from ASAB spruce and pine wood pulp improved.Keywords: Alkaline sulfite; sodium borohydrate; delignification; anthraquinone; ethanol