Effects of chemical environment on softwood kraft pulp: Exploring beyond conventional washing methods

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Title: Effects of chemical environment on softwood kraft pulp: Exploring beyond conventional washing methods
Authors: Senthilkumar, Eashwara Raju, Henriksson, Gunnar, Lindström, Mikael, Professor, 1967, Vikström, Tomas, Sevastyanova, Olena
Source: Nordic Pulp & Paper Research Journal. 40(1):83-93
Subject Terms: brownstock washing, ionic strength, kraft pulping, leaching, lignin
Description: Brownstock washing, a critical process in cleansing kraft pulp, removes dissolved lignin residues from the pulp after it has passed through the cooking digester. It plays a significant role in kraft pulp mills by enhancing economic efficiency and environmental sustainability. Improved washing efficiency leads to better pulp quality and more effective recovery of cooking chemicals. Our study aimed to better understand the impact of different chemical compositions in washing liquors on washing performance. We tested a range of washing liquors, including neutral solutions (deionized water, 1M NaCl, 3M NaCl, 1M Na2SO4) and alkaline solutions (tap water, washing liquor composed of 0.35M NaOH and 1M Na2SO4, and white liquor with 50 g[OH]/l and 8.77 g[HS]/l). These liquors were evaluated for their efficacy in maximizing lignin extraction. Our findings suggest that salt solutions generally reduce washing efficiency. Deionized water and white liquor proved to be the most efficient washing agents, while high-concentration salts and those with high ionic strength negatively impacted washing efficiency. This suggests that brownstock washing may not be operating at its full potential.
File Description: print
Access URL: https://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-363111
https://doi.org/10.1515/npprj-2023-0061
Database: SwePub
Description
Abstract:Brownstock washing, a critical process in cleansing kraft pulp, removes dissolved lignin residues from the pulp after it has passed through the cooking digester. It plays a significant role in kraft pulp mills by enhancing economic efficiency and environmental sustainability. Improved washing efficiency leads to better pulp quality and more effective recovery of cooking chemicals. Our study aimed to better understand the impact of different chemical compositions in washing liquors on washing performance. We tested a range of washing liquors, including neutral solutions (deionized water, 1M NaCl, 3M NaCl, 1M Na2SO4) and alkaline solutions (tap water, washing liquor composed of 0.35M NaOH and 1M Na2SO4, and white liquor with 50 g[OH]/l and 8.77 g[HS]/l). These liquors were evaluated for their efficacy in maximizing lignin extraction. Our findings suggest that salt solutions generally reduce washing efficiency. Deionized water and white liquor proved to be the most efficient washing agents, while high-concentration salts and those with high ionic strength negatively impacted washing efficiency. This suggests that brownstock washing may not be operating at its full potential.
ISSN:02832631
20000669
DOI:10.1515/npprj-2023-0061