Application of anthraquinone in extending the delignification of kraft and polysulfide pulps Part 1: Pulping and bleaching of mixed hardwoods

摘要

Delignification of conventional kraft andrnpolysulfide (PS) hardwood pulps was extended to kappa no. 15rnby adding anthraquinone (AQ). AQ had the samerndelignification effect on both kraft and PS pulping. AQsupplementedrnpulps consumed 6–8% less chemical (0.9–1.1%rnless effective alkali) than conventional pulps. Black-liquor solidsrnfor the AQ-supplemented processes were 3–4% lower than kraftrnor PS, implying a 4% lower heat load to the recovery boiler.rnBleached PS–AQ pulps required 18% less refining time thanrnkraft pulp to reach a freeness of 500 mL CSF. No significantrndifferences in pulp strength were observed among the fourrnbleached pulps. However, the PS and PS–AQ pulps showedrnlower double fold and opacity.