Date of Award

4-1955

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

First Advisor

Dr. Raja Aravamuthan

Abstract

This research characterized and optimized the bleaching potential of dimethyldioxirane (DMD) on an -oxygen-delignified hardwood kraft pulp. The DMD wash produced in-situ using a caroate (2KHSO5.KHSO4.K2 SO4) acetone under controlled conditions. The studied variables included chemical concentration, consistency, temperature, reaction time, and chelation. Statistically designed experiments with response surface, methodology were used - to help locate the optimum conditions with respect to pulp brightness and strength. These conditions were located at 2.8% AO (activated-oxygen charge), 5.5% consistency, and 55° C.

It was found that over 95% of the total brightness increase and about 70% of the total viscosity decrease occurs during the first 5 minutes of reaction time. The bleaching response quickly diminishes beyond this initial time. Bleaching. efficiency was improved using a separate chelation stage prior to the DMD stage. Step-wise chemical addition during bleaching improved brightness, but increased viscosity loss.

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