Title
Alkaline-sulfite/anthraquinone (AS/AQ) pulping of old corrugated container and elemental chlorine free (ECF) bleaching of the pulp
Authors
MAJID SHAFIEI and AHMAD JAHAN LATIBARI

Received March 13, 2014
Published Volume 49 Issue 9-10 October-December
Keywords alkaline-sulfite/anthraquinone, brightness, old corrugated container, opacity, strength

Abstract
Pulping of OCC was carried out applying one of the two levels (16 and 18%) of active alkali, one of the three levels of anthraquinone (0, 0.1 and 0.2% dry weight of the OCC) and one of the two pulping times (120 and 150 minutes). Pulping temperature, Na2SO3/NaOH ratio and liquor to OCC ratio were selected as 170 °C, and 30/70 and 8/1 respectively. The highest yield (65.2%) was reached applying 16% active alkali, pulping time of 150 minutes without AQ and the lowest kappa number (8.8) was related to pulps produced applying 18% active alkali, 0.2% AQ and 150 minutes time. The pulp produced applying 18% active alkali, 150 minutes pulping time without AQ exhibited the highest tensile strength index at 24.6 N.mg-1. The pulp produced applying 18% active alkali, 150 minutes time and 0.1% AQ was selected for elemental chlorine free (ECF) bleaching (D0EPD1 short sequence). The results of ECF bleaching revealed that the application of 1.61% ClO2 produces brightness, opacity and yellowness of 82.6%, 80.2% and 5.6% ISO, respectively. The bleaching yield was measured as 92.1% and the tensile strength and tear strength indices of bleached pulp were of 17.88 N·mg-1 and 10.48 mN·m2g-1, respectively.