Investigating the effects of process variables on APMP Pulp brightness and yields of p.alba

The present study was fulfilled with the aim of investigating the effects of process variables on APMP (alkaline peroxide mechanical pulping) pulp brightness and yields of P.alba to produce high yield pulps suitable for making writing and printing papers. The wood samples have been prepared from the poplar plantation fields in the area of Maragheh Paper Company and converted to acceptable chips by MWPI industrial chipper. Based on the results obtained in the preliminary experiments (1), chips prostrating time of 20 minutes, impregnation times of 20 minutes for first stage and 9o and 105 minutes for second stage, total caustic soda charge of 6 and 7 % with usage rations of 40, 50 and 60% of total caustic in first impregnation stage, total hydrogen peroxide charge of 5% with usage ratio of 25% in first impregnation stage, pulp consistency of 32-34 and 23% in first and second impregnation stages, respectively, were selected and studied as effective process variables to achieve high yield APMP pulps with pulp brightness of about 80%. The results have shown that; at caustic soda charge level of 6% with usage ratio of 60% of total caustic in first impregnation stage and treatment time of 105 minutes at second impregnation stage, it would be possible to produce APMP pulp with 81.9% brightness and relatively high pulp yield of about 88%. At total caustic charge of 7% with similar usage ratio, APMP pulp of 79.9% brightness at pulp yield of 86.8% in treatment time of 90 minutes, and APMP pulp of 80.2% brightness at relatively low pulp yield of 85.3% can be produced in treatment time of 105 minutes at second impregnation stage. By reducing the treatment time at second impregnation stage and using lower usage ratio of total caustic in the first impregnation stage, APMP pulps have higher yields but at lower brightness.