Recovery of caustic soda and side-products from the washing filtrates of the novel dissolving pulp process “StExCell” (steam-exploded cellulose pulp)
Loading...
Journal Title
Journal ISSN
Volume Title
Kemian tekniikan korkeakoulu |
Master's thesis
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.
Date
2024-08-29
Department
Major/Subject
Chemical and Process Engineering
Mcode
CHEM3043
Degree programme
Master's Programme in Chemical, Biochemical and Materials Engineering
Language
en
Pages
67+6
Series
Abstract
Steam explosion can be defined as an innovative pre -treatment technique of pulping that exposes wood chips to high pressure steam followed by rapid decompression to disrupt the cell wall structure, thus effectively extracting the hemicellulose and improving the accessibility of cellulose fibres to pulping chemicals in the subsequent stages. After steam explosion of the birch wood chips under pre-optimized conditions, the residual solid fraction was subjected to washing to extract the degraded, water-soluble wood components. The washing procedure of the steam-exploded wood was assessed and optimized by the Nordén model. The wash filtrate was analysed and further treated to isolate and valorize the extracted compounds. Rotary evaporation at 130 mbar and 60 °C to a target distillate collection of 35 wt.% was optimal for the furfural separation. The evaporated liquor was subjected to activated carbon adsorption with an optimum dose of 2 wt.% for the efficient removal of low molecular weight, reactive lignin fraction. The furfural and lignin-lean residue was subjected to acidic dehydration treatment (optimized at 200 °C for 7 minutes in 0.1M H2SO4) to degrade the remaining monomeric and oligomeric xylose to furfural, which was then isolated by another rotary evaporation. The steam exploded wood was subjected to mild caustic extraction (80 °C, 100 kg NaOH/t for 1 hour). A subsequent washing sequence was applied to primarily remove lignin which dissolves well in alkaline mediums. Membrane filtration with 0.5 kDa membranes was conducted to separate unreacted NaOH and lignin from the wash filtrate. Most of the extracted lignin remained in the retentate, while all NaOH had transferred to the permeate phase indicating a successful separation.Description
Supervisor
Hummel, MichaelThesis advisor
Sixta, HerbertLê, Huy Quang
Keywords
steam explosion, pulp washing, rotary evaporation, furfural recovery, dehydration of xylose, alkaline extraction
