Cationic Polymer Drainage Aid for Cellulosic Pulp
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Solution Overview
Problem
Current pulp making processes face challenges in improving drainage rate and dryness of dewatered pulp sheets, with previous methods involving sophisticated dewatering and retention systems proving unsuccessful due to reduced drainage and increased thermal drying requirements.
Innovation Solution
The use of specifically defined cationic polymers as sole drainage agents, including copolymers of (meth)acrylamide and (meth)acryloyloxy trimethyl ammonium chloride, and hydrolysed homopolymers of vinylformamide, which are added to the cellulosic suspension to enhance drainage and drying efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sophisticated dewatering and retention systems are added to improve drainage, then drainage rate is reduced, but thermal drying requirements increase
Solution Approach 1:
The invention changes the chemical parameters of the dewatering system by using specifically defined cationic polymers with controlled molecular weights and charge densities, optimizing the polymer-to-pulp ratio and application timing to achieve better drainage without excessive thermal drying
Solution Approach 2:
The invention replicates the effective drainage mechanism found in integrated mills (where pulp is diluted directly for papermaking) in non-integrated mills by using polymer additives that mimic the natural drainage behavior, allowing efficient dewatering without complex sophisticated systems
2Productivity
If combinations of cationic polymers with inorganic materials like bentonite are used for dewatering, then drainage is improved, but dewatering time increases and energy costs rise
Solution Approach 1:
The invention extracts and eliminates the need for inorganic materials like bentonite from the dewatering system, using solely optimized cationic polymers that achieve superior dewatering performance without the time delays and energy costs associated with conventional combinations
Solution Approach 2:
The invention uses composite polymer structures with specific combinations of cationic charges and molecular weights to create a material that performs multiple functions (flocculation, dewatering, and retention) simultaneously, replacing the need for separate polymer and inorganic material applications
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
These polymers significantly improve dewatering time and solid content of pulp sheets, reducing energy costs and increasing productivity, as demonstrated by the examples provided, outperforming previous methods that used combinations of cationic polymers with inorganic materials like bentonite.
Implementation Method 1
a water soluble cationic polymer is added to the suspension as the sole drainage aid
Data Source
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AI summary
A pulp making process in which fibrous cellulosic material is pulped to form an aqueous suspension of cellulosic material, the suspension is drained through a screen to form a pulp sheet and that the pulp sheet is dried to form a dry market pulp, in which a water soluble cationic polymer is added to the suspension as the sole drainage aid wherein the water-soluble cationic polymer is either, i) a copolymer comprising (a) between 1 and 70 mole % (meth) acrylamide and (b) between 30 and 99 mole % (meth) acryloyloxyethyl- trimethyl ammonium chloride with an intrinsic viscosity between 5 and 9 dl/g; or ii) a hydrolysed homopolymer of vinylformamide comprising between 1 and 100 mole% vinyl amine units and having a K value of between 45 and 240. The process of the invention provides improved drainage time and solids content of the dewatered pulp.