Total Chlorine Free Bleaching of NaOH-AQ Pulp of Corn Stalk:Bleaching Sequences Optimization

摘要

Corn stalk is an abundant fibric materials and can be used to produce pulp.Total chlorine free(TCF)bleaching is environmentally friendly technology and is widely used in the papermaking industry in the world.In this work,corn stalks NaOH-AQ pulp were selected as the experimental materials to be bleached with TCF bleaching sequences including oxygen,hydrogen peroxide,acetic acid and DTPA chemicals.Different bleaching sequences such as O,OQP,OQPa,OQPPa and OQPaP were carried out and the effect of chemical dosage,pH,temperature and time on the bleaching efficiency of corn stalks NaOH-AQ pulp were thoroughly investigated.The optimal bleaching sequences were thus chosen and its process conditions were further optimized.The results showed that the optimal bleaching sequence was OQPaP,in which the optimal bleaching conditions of each stage were as follows: O stage at oxygen pressure of 0.6 MPa,temperature of 100 ℃ and NaOH 3％for 60 min; Q stage at DTPA dosage of 0.5％and temperature of 60℃ for 60 min; and P stage at H2O2 dosage of 2％,NaOH of 1.5％and temperature of 80 ℃ for 120 min; Pa stage at 3％C2H4O3,pH 6 and 65 ℃ for 80 min.The brightness of the bleached pulp reached 80.5％ISO and the viscosity of 1031 mL· g-1 was obtained under the above optimal bleaching sequence.