Design, optimization and modelling of a chemical recovery system for wet spinning of cellulose in sodium carbonate solut
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ORIGINAL RESEARCH
Design, optimization and modelling of a chemical recovery system for wet spinning of cellulose in sodium carbonate solutions Marta Bialik Marta Lopes
. Anna Jensen . Oula Kotilainen . Ida Kulander .
Received: 27 March 2020 / Accepted: 10 August 2020 Ó The Author(s) 2020
Abstract The aim of this study is to present the design, optimization and modelling of a chemical recovery system for a novel CS2-free viscose-type process that entails dissolution of pre-treated dissolving pulp in a continuous-flow reactor in cold alkali and wet spinning of cellulose in sodium carbonate solutions. Technologies already known to other industries for the recovery and reuse of chemicals, such as causticizing, recalcination, recarbonization and freeze-separation, were used. Chemical equilibria simulations were performed with OLI Studio 9.5, with the purpose to select experimental conditions which avoid undesired precipitations in each unit operation. Synthetic solutions mimicking the spent coagulation liquor were used in the laboratorial experiments. The proposed chemical recovery system was shown to be technically feasible and reduce chemical make-ups to a minimum of 45 kg/ton of NaOH and 4 kg/ton of H2SO4. Small amounts of Zn are expected to precipitate during recarbonization of the coagulation liquor at 30 °C and causticizing at 98 °C. Thus, a filter for ZnO particles should be included in the design of the recarbonization unit and a M. Bialik (&) A. Jensen I. Kulander M. Lopes Department Biorefinery and Energy, RISE Research Institutes of Sweden, Drottning Kristinas Va¨g 61, 114 28 Stockholm, Sweden e-mail: [email protected] O. Kotilainen Andritz Oy, Tammasaarenkatu 1, 00180 Helsinki, Finland
continuous purge of lime mud and input of fresh lime make-up should be needed to keep burnt lime availability at an acceptable level. Overall, the results presented in this study portray a solution to reduce operating costs and the environmental impact of novel viscose-type processes with alkaline spin dopes and wet spinning of cellulose in sodium carbonate solutions. Keywords Regenerated cellulose Textile fibre Chemical recovery Process modelling Causticizing Freeze-crystallization Recarbonization
Introduction The manufacturing of regenerated cellulose fibres involves different chemical and mechanical processes that yield fibres with distinct properties. Viscose, modal, lyocell and cuprammonium rayon are the most common man-made cellulose fibres with application primarily in textile fabrics (Ro¨der et al. 2013). With the growing population and environmental awareness across the world, the demand for sustainable textile fibres is expected to increment at a steady rate. However, the dominant viscose process suffers certain economic and environmental drawbacks, such as the demand for large chemical make-ups (NaOH and H2SO4) and the use of hazardous carbon disulphide
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Cellulose
(CS2) in cellulose xanthation and dissolution. In recent years, a significa
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