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Title

INVESTIGATION ON PRODUCTION OF BLEACHABLE CHEMI-MECHANICAL PULP FROM WHEAT STRAW

Writers

JAHAN LATIBARI A.

Pages

 Start Page 634 | End Page 646

Abstract

 In an attempt to develop pulping process suitable for small scale implementation, production of bleachable CHEMI-MECHANICAL PULP from wheat starw is investigated. Four levels (10, 12, 14 and 16% based on oven dry weight of straw) NaOH and three pulping times (20, 30 and 40 minutes) at 95oC pulping temperature were used. After digester YIELD varied between 64.65 and 71.7% and the total YIELD after defibration was measured as 54.45% and 62%.  Unrefined pulp freeness varied between 708 and 765 ml CSF. Pulps produced applying 10-16% NaOH, 40 minutes pulping time and 95oC pulping temperature was selected from further evaluation. These pulps were refined to about 365 ml CSF in a PFI mill and then hand sheets were made for STRENGTH evaluation. The apparent density of the hand sheets varied between 437-488 kg/m3, tear index between 6.51-7.11 mN.m2/g, and tensile index between 29.2 -30.8 N.m/g. Significant difference at 99%  was not observed between the STRENGTH of the pulps. Then pulp produced applying 10% NaOH, 40 minutes pulping time and 95oC pulping temperature was selected for bleaching trials. TOTALLY CHLORINE FREE (TCF) bleaching sequence was used for bleaching the selected pulp.  Pulps bleached applying 4% H2O2 and 3.5% NaOH, 3% sodium Silicate, 0.5% MgSO4 and 0.3% DTPA for 2 hours showed the highest brightness of 50.69% compared to 29.2% for unbleached pulp.

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