Multistage Soda Pulping for Corrugated Medium Quality
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Solution Overview
Problem
Standard soda/caustic pulping methods produce pulp with inferior quality, particularly for paper grades requiring high ring crush and corrugated medium test values, and result in lower pulp yields compared to other semi-chemical pulping processes.
Innovation Solution
A new method involving multistage delignification using soda or soda ash cooking liquor, followed by mechanical fiberizing and oxidation of lignin at controlled temperatures and pressures, enhances pulp quality while maintaining simple chemical recovery and minimizing environmental pollution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard soda/caustic pulping is used, then chemical recovery is simple and inexpensive, but pulp quality is inferior with lower ring crush and CMT values
Solution Approach 1:
The pulping process is divided into multiple sequential stages: primary cooking in soda/caustic liquor, washing, and secondary delignification in carbonate liquor. This segmentation allows each stage to optimize for its specific function, achieving both high pulp quality and simple chemical recovery
Solution Approach 2:
The invention changes key process parameters including cooking temperature (160-200°C), cooking time (1-4 hours), and liquor composition ratios. These parameter optimizations enable the multi-stage process to achieve superior pulp quality while maintaining chemical recovery simplicity
2Manufacturing precision
If NSSC pulping is used, then pulp quality is improved, but pulp yield decreases to 75-82%
Solution Approach 1:
The invention extracts and removes lignin through controlled delignification stages, selectively eliminating harmful components while preserving cellulose fibers. This selective extraction improves pulp quality without excessive fiber loss, achieving yields of 75-80%
Solution Approach 2:
The delignification process is applied partially through controlled cooking stages rather than complete delignification. This partial action removes sufficient lignin to improve quality while avoiding excessive cooking that would reduce yield
3Manufacturing precision
If sulfur containing cooking chemicals are used, then pulp quality is improved, but pulp yield decreases and environmental pollution increases
Solution Approach 1:
The invention converts the traditionally harmful sulfur-containing chemicals into beneficial non-sulfur soda and soda ash chemicals. This substitution eliminates environmental pollution while maintaining effective pulping and delignification, achieving high pulp quality without harmful emissions
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
The method significantly improves pulp quality metrics such as ring crush, CMT, Mullen, Tensile, and Tear strength by 25% to 40% with final pulp yields of 75% to 80%, correlating with improved washing and consistency during oxygen treatment.
Implementation Method 1
The step of removing or oxidizing the lignin may be performed at a temperature in a range of 120 degrees Fahrenheit (deg. F) to 300 deg. F
Implementation Method 2
The method may also include a mechanical fiberizing process
Data Source
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AI summary
A method to make pulp adapted for forming a corrugated medium, the method includes: cooking chips in a cooking vessel using a caustic carbonated pulping soda/caustic (SC) cooking liquor injected into the cooking vessel; fiberizing the chips discharged from the cooking vessel to form a pulp, and removing lignin from the pulp or oxidizing lignin in the pulp by injecting oxygen (02) into the fiberized pulp.