Pulp mill filtrate oxidation
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Journal Title
Journal ISSN
Volume Title
Kemian tekniikan korkeakoulu |
Master's thesis
Authors
Date
2024-05-21
Department
Major/Subject
Biomass Refining
Mcode
CHEM3021
Degree programme
Master's Programme in Chemical, Biochemical and Materials Engineering
Language
en
Pages
77 + 3
Series
Abstract
The demand of methanol, one of the most widely traded chemicals, has been continuously growing. In order to achieve a sustainable bioeconomy, forest industry is promoting the utilization of methanol as a value-added by-product from pulping process, as methanol production in the kraft process can be as high as 15 kg/t of pulp. In kraft pulping, the majority of methanol is formed from xylan through elimination and from lignin through oxidative demethoxylation. Previous studies indicate that dissolved lignin present in pulp washing filtrates is a potential source of increasing the overall methanol yield further. According to literature, oxidative demethoxylation of lignin largely depends on several reaction parameters, such as oxygen pressure, mass transfer of oxygen, temperature, pH, and time. In this study, all the experiments were conducted without pH control, as the original filtrate pH levels were quite suitable for lignin oxidation. According to the results, the most important factors on methanol formation were filtrate type, followed by oxygen pressure, time and temperature. Methanol formation in the brown stock washing filtrates was more intensive compared to post-oxygen washing filtrates. The highest methanol formation in the oxidation of hardwood brown stock filtrates was 19.7 kg/t and the corresponding value for softwood filtrate was 8.6 kg/t. Basically, the methanol content could be tripled in hardwood and doubled in softwood brown stock filtrates compared to its original content. In addition, oxidation had a clear impact on filtrate characteristics. The harsher the condition, the more significant decrease of pH and dry matter content occurred, in turn the higher the methanol formation. However, the decrease of COD did not show a clear relationship with methanol formation.Description
Supervisor
Vuorinen, TapaniThesis advisor
Pesola, AinoFerro, Estefania Isaza
Keywords
methanol, washing filtrate, oxidation, demethoxylation, lignin