Accelerating kraft pulping with hydroxyethylidene diphosphonic acid (HEDP)
Source abstract
Abstract
Three hardwoods (aspen, maple, and birch) and one softwood (black spruce) were pulped under standard kraft cooking conditions with and without hydroxyethylidene diphosphonic acid (HEDP). The H factor required to give a kappa number of 15 for the aspen furnish was decreased from 1,100 to 650 by adding 0.1% HEDP on wood. Significantly smaller rate increases were observed with birch and maple, and no rate increase was observed with the softwood furnish. When aspen and black spruce chips were impregnated with calcium, it was found that aspen delignification was retarded while there was no effect on black spruce. HEDP, therefore, appears to work by removing calcium which, in hardwoods, causes lignin to be strongly bonded to the fiber. Adding carbonate to the pulping liquor showed that carbonate has the same effect as HEDP by removing calcium as insoluble calcium carbonate (CaCO3). These observations lead to the conclusion that HEDP is not an effective additive, even for hardwoods, when sufficient carbonate is present.
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Research context
OpenAlex topics: Lignin and Wood Chemistry · Materials Engineering and Processing
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References (18)
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