Sodium Dithionite in Cellulose Pulping for Yield and Odor Control
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Solution Overview
Problem
Current processes for producing cellulose from lignocellulose-containing materials, such as sulfite and sulfate digestion, face challenges in achieving high pulp yield with low lignin content while minimizing malodorous emissions, particularly in the sulfate process.
Innovation Solution
The addition of small amounts of dithionic acid salts, such as sodium dithionite, during sulfite or sulfate digestion processes optimizes the extraction of cellulose, improving pulp yield and reducing lignin content while minimizing the formation of malodorous substances like mercaptans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional sulfite or sulfate digestion processes are used to extract cellulose from lignocellulose-containing material, then cellulose production is achieved, but pulp yield is limited and lignin content in the pulp remains high
Solution Approach 1:
Sodium dithionite is added to the cooking liquor before the digestion process begins, allowing it to pre-react with lignin and form water-soluble complexes. This preliminary action modifies the lignin structure in advance, making it more susceptible to removal during the subsequent digestion process, thereby achieving both high pulp yield and low lignin content simultaneously
Solution Approach 2:
Sodium dithionite acts as a chemical intermediary that facilitates the separation of lignin from cellulose. It forms temporary water-soluble complexes with lignin molecules, enabling selective removal of lignin while preserving cellulose integrity. This intermediary substance bridges the gap between the cooking liquor and lignin, enhancing the overall extraction efficiency
2Productivity
If sulfate digestion process is used to produce cellulose, then cellulose extraction is achieved, but malodorous mercaptan emissions are generated
Solution Approach 1:
The patent converts the harmful sulfate digestion process into a beneficial one by adding sodium dithionite, which reacts with mercaptans to form non-odorous disulfides. This transforms the harmful malodorous emissions into harmless or less harmful substances, eliminating the odor problem while maintaining the effectiveness of cellulose extraction
Solution Approach 2:
The addition of sodium dithionite changes the chemical parameters of the cooking liquor, introducing reducing agents that modify the sulfur chemistry. This parameter change prevents the formation of mercaptans or converts them into non-odorous compounds, thereby reducing harmful emissions while maintaining cellulose extraction efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances pulp yield and whiteness while reducing the concentration of malodorous substances in the exhaust gases, specifically mercaptans, thereby improving the overall efficiency and environmental impact of the cellulose production process.
Implementation Method 1
The addition of small amounts of dithionic acid salts, such as sodium dithionite, during sulfite or sulfate digestion processes optimizes the extraction of cellulose, improving pulp yield and reducing lignin content
Data Source
AI summary
The invention relates to a method for producing cellulose from material containing lignocellulose by means of sulfite decomposition or sulfate decomposition in the presence of a salt of dithionous acid, characterized in that the salt of dithionous acid is used in an amount in the range of 0.1 to 4.0 wt% with respect to the amount of kiln-dry material containing lignocellulose.