HT-CTMP Pulping of Hardwood-Softwood Chips With Short Steam Pretreatment
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Solution Overview
Problem
Existing CTMP production methods do not effectively produce pulp with improved properties such as high bulk and tensile strength while minimizing energy consumption and chemical use.
Innovation Solution
A method involving mixing hardwood and softwood chips, impregnating with sulfite and optionally NaOH, and applying high-temperature steam to produce high-temperature chemithermomechanical pulp (HT-CTMP) with controlled residence time and mass flow ratios of sulfite to NaOH, eliminating or reducing NaOH use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If higher temperatures are used during heat treatment to improve pulp properties, then bulk and tensile strength are improved, but energy input increases
Solution Approach 1:
The patent applies parameter changes by using high-temperature steam (at least 150°C) during the heat treatment step to soften the wood chips. This elevated temperature parameter enables improved fiber separation and pulp properties (higher bulk and tensile strength) while the continuous process design and optimized residence time (no more than two minutes) help control the overall energy input efficiency
Solution Approach 2:
The patent applies preliminary action through the impregnation step where sulfite and optionally NaOH are applied to the wood chips before heat treatment. This pre-treatment modifies the wood structure in advance, making it more responsive to the subsequent high-temperature steam treatment, thereby achieving better pulp properties with optimized energy utilization
2Strength
If sulfite and NaOH are used for impregnation to improve pulp quality, then bulk and freeness are improved, but chemical usage increases
Solution Approach 1:
The patent applies the taking out principle by selectively removing NaOH from the impregnation liquid formulation or reducing it to minimal amounts. The process achieves improved bulk and freeness properties primarily through sulfite impregnation combined with high-temperature steam treatment, eliminating the need for significant NaOH addition and thereby reducing chemical usage while maintaining pulp quality
Solution Approach 2:
The patent changes the chemical composition parameters of the impregnation liquid by using sulfite as the primary chemical agent with optionally minimal or no NaOH. This parameter change in chemical formulation, combined with the high-temperature steam treatment parameter, achieves the desired pulp properties (bulk and freeness) with reduced overall chemical usage compared to conventional methods
3Productivity
If residence time is reduced to increase productivity, then production speed is improved, but treatment effectiveness may worsen
Solution Approach 1:
The patent applies parameter changes by using high-temperature steam (at least 150°C) which accelerates the heat treatment kinetics. This elevated temperature parameter compensates for the reduced residence time (no more than two minutes), ensuring that effective softening and fiber separation occur within the shorter time frame, thereby maintaining treatment effectiveness while increasing productivity
Solution Approach 2:
The patent applies preliminary action through the impregnation step that prepares the wood chips before the brief high-temperature steam treatment. This pre-treatment with sulfite modifies the wood structure in advance, making it more susceptible to rapid softening during the short residence time in the steam treatment, thus ensuring effective treatment is achieved even with reduced residence time for higher productivity
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
Results in HT-CTMP with enhanced tensile index and bulk properties, reducing energy input and chemical usage, and maintaining or improving bulk and freeness characteristics.
Implementation Method 1
impregnating the chips of the mixture with an impregnation liquid comprising sulfite and optionally NaOH to obtain impregnated chips
Implementation Method 2
applying steam having a temperature of at least 150°C to the impregnated chips to obtain pretreated chips
Implementation Method 3
applying steam having a temperature of at least 150°C to the impregnated chips
Data Source
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AI summary
There is provided a method of forming a high temperature chemithermomechanical pulp (HT-CTMP) comprising the steps of: a) mixing hardwood chips and softwood chips to obtain a mixture, wherein the dry weight ratio of hardwood to softwood in said mixture is between 85:15 and 65:35; b) impregnating the chips of the mixture with an impregnation liquid comprising sulfite and optionally NaOH to obtain impregnated chips; c) applying steam having a temperature of at least 150°C to the impregnated chips to obtain pretreated chips; and d) defibrating the pretreated chips, wherein the mass flow of sulfite (calculated as Na2SO3) to step b) is higher than the mass flow of NaOH to step b) and the residence time in step c) is no more than two minutes.