Sulfonation of Alkali Pulp for Bleaching Efficiency
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Solution Overview
Problem
Alkali pulps produced through Kraft processes are difficult to bleach and require high amounts of bleaching chemicals, leading to increased costs and environmental impact, as existing methods do not effectively utilize sulfonation to modify lignin for enhanced bleaching efficiency.
Innovation Solution
Sulfonating alkali pulp at a pH less than 7 prior to, during, or after an extended delignification stage, followed by washing, to make lignin more receptive to bleaching chemicals, thereby reducing the need for bleaching chemicals like ClO2, H2O2, and O3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional alkali pulping processes are used, then pulp strength is improved, but pulp brightness and ease of bleaching deteriorate
Solution Approach 1:
The patent applies sulfonation as a preliminary treatment step before bleaching. By treating the alkali pulp with sulfonating agents (SO2, MHSO3, or M2SO3) at controlled pH levels (less than 7) before the bleaching sequence, the lignin is pre-modified to be more receptive to subsequent bleaching chemicals, thereby improving bleaching efficiency without compromising pulp strength
Solution Approach 2:
The patent changes the chemical parameters of the pulp by introducing sulfonation treatment. This involves adjusting pH levels to less than 7 during sulfonation, controlling temperature and time parameters, and modifying the chemical structure of lignin through sulfonate group attachment, which transforms the lignin into a more bleachable state while preserving fiber strength
2Illumination intensity
If high amounts of bleaching chemicals are used to bleach alkali pulp, then pulp brightness is improved, but cost and environmental impact worsen
Solution Approach 1:
By performing sulfonation before bleaching, the patent prepares the lignin in advance to be more reactive toward bleaching chemicals. This preliminary modification reduces the quantity of bleaching chemicals needed during the actual bleaching process, thereby lowering both costs and environmental impact while achieving the desired brightness
Solution Approach 2:
The sulfonating agents (SO2, MHSO3, M2SO3) act as intermediary substances that modify the lignin structure to enhance its reactivity with subsequent bleaching chemicals. This intermediary treatment step creates a more receptive state for the bleaching chemicals, reducing their overall consumption while improving bleaching 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
Significantly reduces bleaching chemical usage, lowers costs, enhances pulp brightness and stability, and improves bleached pulp performance while minimizing environmental impact by making lignin more soluble and reactive to bleaching agents.
Implementation Method 1
sulfonating an alkali pulp at a pH less than 7 prior to, during, or after at least one bleaching sequence
Data Source
AI summary
This invention relates to the delignification of lignocellulosic pulp. More particularly, the invention relates to sulfonation and bleaching of the alkali pulping produced by Kraft pulp processes or produced through combination of alkali pulping processes and extended delignification stages.