Dissolving pulp manufacture using SO<sub>2</sub>-ethanol-water (SEW) fractionation process followed by ECF bleaching

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School of Chemical Engineering | Master's thesis
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Authors

Date

2013

Department

Puunjalostustekniikan laitos

Major/Subject

Selluloosatekniikka

Mcode

Puu-23

Degree programme

Language

en

Pages

104 + [24]

Series

Abstract

The objective of this thesis is to develop a process for the manufacture of rayon pulp from spruce wood based on SO<sub>2</sub>-ethanol-water (SEW) fractionation process followed by ECF bleaching. SEW fractionation process is highly promising to become a basis for Forest Biorefinery as it allows clean separation of biomass components, i.e. cellulose, hemicelluloses and lignin. In addition to complete conversion of biomass polysaccharides into biofuels, this process is capable of producing traditional pulp and paper products. Compared to the state-of-the-art acid sulfite technology the advantages of using SEW process to prepare dissolving pulp are absence of base, higher dissolved sugar yields due to absence of oxidation, higher flexibility in raw material (pine and larch are readily digestible) and considerably lower overall duration due to absence of impregnation stage. In the present work, the influence of the fractionation and bleaching parameters on the physical and chemical characteristics of SEW dissolving pulp is investigated. Based on the study of the effect of the fractionation conditions, two unbleached SEW pulp (I and II) were produced using the following conditions: ethanol volume fraction 0.55, SO<sub>2</sub> concentration 12 w/w%, liquor-to-wood ratio (L/W) 6 (I) and 3 (II), 150 °C, duration 60 (I) and 50 (II) minutes. The following bleaching sequences were applied: EO-D-Q-P (I), E-O-D-Q-P (I) and O-D-EP-Q-P (II) to accomplish full brightness. Practically all the characteristics of the final rayon SEW pulps were comparable to those of Mg acid sulfite rayon pulps. SO<sub>2</sub> regeneration experiments showed that most of SO<sub>2</sub> can be recovered during evaporation of ethanol, while only a small fraction (about 3%) was bound in the form of lignosulfonates.

Description

Supervisor

Sixta, Herbert

Thesis advisor

Iakovlev, Mikhail

Keywords

biorefinery, SO<sub>2</sub>-ethanol-water, fractionation, dissolving pulp, bleaching

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https://urn.fi/URN:NBN:fi:aalto-2020122859458

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[dipl] Kemian tekniikan korkeakoulu / CHEM