CTMP Pulp Dilution to Reduce Extractives Re-adsorption
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Solution Overview
Problem
Chemithermomechanical pulp (CTMP) typically contains high levels of wood extractives, which cause taste and odor issues in applications like food packaging, particularly due to the re-adsorption of extractives onto fibers during the dewatering process, making it difficult to achieve low extractives content.
Innovation Solution
A method involving a pulper to rapidly dilute the pulp to a consistency of 2-8 wt.% after refining, reducing residence time and preventing re-adsorption of extractives, combined with high-temperature steam treatment and bleaching steps to enhance extractives removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the pulp is diluted slowly in the pulper (residence time >15 min), then the pulp achieves good homogeneous dispersion, but the extractives have time to re-adsorb to the fibers making them harder to remove
Solution Approach 1:
The patent applies the principle of rushing through the pulping process by reducing the residence time in the pulper to less than 15 minutes. This allows the pulp to be rapidly diluted and transferred to the dewatering stage, minimizing the time window during which extractives can re-adsorb to fibers while still achieving adequate homogeneous dispersion through intensive mixing during this compressed timeframe.
2Object-generated harmful factors
If the residence time in the pulper is reduced to less than 15 min, then the removal of extractives is improved, but the time required for homogeneous dilution is insufficient
Solution Approach 1:
The patent applies preliminary action by performing intensive mixing and homogeneous dilution of the pulp during the compressed residence time in the pulper before extraction. The system prepares the pulp slurry with adequate homogeneity through high-intensity mixing during the brief residence time, so that when extraction occurs, the pulp is already properly dispersed and ready for efficient extractive removal without requiring additional time.
3Productivity
If conventional CTMP production methods are used, then the process is simple and fast, but the extractives content remains high causing taste and odor issues
Solution Approach 1:
The patent applies the extraction principle by introducing a dedicated extraction stage following the pulping process. During this stage, the diluted pulp undergoes extraction treatment (such as washing or chemical extraction) specifically targeted at removing extractives from the fiber structure. This separate extraction step effectively reduces extractives content to levels suitable for food packaging applications while maintaining the overall productivity of the CTMP production process.
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 effectively reduces the content of extractives in CTMP, improving its suitability for food packaging applications by ensuring efficient removal and minimizing taste and odor issues.
Implementation Method 1
diluting the pulp in a pulper to obtain a diluted pulp, wherein the residence time in the pulper is less than 15 min
Implementation Method 2
By diluting the pulp in a pulper, the pulp may be homogeneously diluted within less than 15 min
Implementation Method 3
heating the impregnated chips with steam to obtain pre-treated chips
Implementation Method 4
heating the impregnated chips with steam to obtain pre-treated chips
Implementation Method 5
followed by a heat treatment to soften the wood
Implementation Method 6
dewatering the diluted pulp
Implementation Method 7
Diluting the pulp after refining may further help to disperse the extractives in the water phase and thereby facilitate their removal in a subsequent dewatering step
Implementation Method 8
defibrating of the pre-treated chips to obtain a pulp
Implementation Method 9
The treated wood chips are then subjected to defibration/refining
Data Source
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AI summary
The present disclosure relates to a method for producing chemithermomechanical pulp, CTMP, comprising: a) providing wood chips comprising hardwood, softwood or a mixture thereof; b) impregnating the wood chips with an impregnation liquid to obtain impregnated chips; c) heating the impregnated chips with steam to obtain pre-treated chips; d) defibrating the pre-treated chips to obtain a pulp; e) diluting the pulp in a pulper, wherein the residence time in the pulper is less than 15 min; and f) dewatering the diluted pulp.