{"title":"Using multistage models to evaluate how pulp washing after the first extraction stage impacts elemental chlorine-free bleach demand","authors":"B. Brogdon, L. Lucia","doi":"10.32964/TJ17.11.621","DOIUrl":null,"url":null,"abstract":"Steady-state models were constructed to predict the response of a southern U.S. softwood brown¬stock to three- and five-stage elemental chlorine-free (ECF) bleach sequences. The models provided insight into how typical (EO) washing efficiencies from a vacuum drum unit affected pulp brightening and total chlorine dioxide con¬sumption. When (EO) carryover was between 15% and 30%, the chlorine dioxide needed to reach target brightness increased by 8% to 15% for the D0(EO)D1(EP)D2 sequence (89% ISO) and by 15% to 23% for the D0(EO)D1 sequence (86% ISO) versus perfect washing. Use of (EO) filtrate as D0 shower water, such as in split-flow countercurrent wash¬ing, caused the bleach uptake to increase by 1.5 to 3.0 kg chlorine dioxide (ClO2)/ton pulp when compared to using cleaner D0 shower water sources. The ClO2 consumed by 15% to 30% (EO) washer carryover is comparable to that consumed by typical carryover levels from brownstock washing (~10 kg Na2SO4/ton pulp). High (EO) carryover made ECF bleaching to higher brightness targets more difficult.","PeriodicalId":11014,"journal":{"name":"Day 1 Mon, November 12, 2018","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2018-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Day 1 Mon, November 12, 2018","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.32964/TJ17.11.621","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
Steady-state models were constructed to predict the response of a southern U.S. softwood brown¬stock to three- and five-stage elemental chlorine-free (ECF) bleach sequences. The models provided insight into how typical (EO) washing efficiencies from a vacuum drum unit affected pulp brightening and total chlorine dioxide con¬sumption. When (EO) carryover was between 15% and 30%, the chlorine dioxide needed to reach target brightness increased by 8% to 15% for the D0(EO)D1(EP)D2 sequence (89% ISO) and by 15% to 23% for the D0(EO)D1 sequence (86% ISO) versus perfect washing. Use of (EO) filtrate as D0 shower water, such as in split-flow countercurrent wash¬ing, caused the bleach uptake to increase by 1.5 to 3.0 kg chlorine dioxide (ClO2)/ton pulp when compared to using cleaner D0 shower water sources. The ClO2 consumed by 15% to 30% (EO) washer carryover is comparable to that consumed by typical carryover levels from brownstock washing (~10 kg Na2SO4/ton pulp). High (EO) carryover made ECF bleaching to higher brightness targets more difficult.