Starch Agglomeration in Recycled Pulp for Papermaking
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Solution Overview
Problem
Recycled fibre material in paper production contains low molecular weight starch, which is not effectively retained on fibres, leading to increased microbial growth, odour issues, and higher wastewater treatment costs due to its presence in water circulation, affecting process yield and product quality.
Innovation Solution
A method involving the addition of a coagulant agent followed by a flocculating agent to the pulp flow, allowing the starch to form agglomerates that can be retained on the fibres, reducing the amount of starch in water circulation and improving process yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If starch is added to recycled fibre material for strength improvement, then paper strength is enhanced, but microbial growth increases and wastewater treatment costs increase
Solution Approach 1:
The patent extracts and removes excess starch from the recycled fibre material through screening and washing processes. By separating the starch from the fibres before papermaking, the harmful microbial growth is eliminated while retaining the necessary starch for strength improvement in controlled amounts.
Solution Approach 2:
The patent changes the molecular weight parameter of starch by using enzymes to break down high molecular weight starch into lower molecular weight starch. This modified starch retains strength-improving properties while being less susceptible to microbial degradation, thus reducing microbial growth and wastewater treatment costs.
2Productivity
If starch is retained in water circulation during pulping, then process yield is maintained, but COD load increases and wastewater treatment costs increase
Solution Approach 1:
The patent extracts starch from the water circulation through screening and thickening processes. By removing starch from the aqueous phase before it enters wastewater treatment, the COD load is significantly reduced while the starch is recovered and retained in the fibre slurry to maintain process yield.
Solution Approach 2:
The patent uses screening media and thickening equipment as intermediary devices to separate starch from water circulation. These intermediaries enable the division of the water-starch mixture into starch-rich solid phase and starch-poor liquid phase, allowing starch recovery and wastewater quality improvement simultaneously.
3Productivity
If low molecular weight starch is present in recycled fibre material, then papermaking process continues, but starch is not retained on fibres and is lost to water circulation
Solution Approach 1:
The patent changes the molecular weight parameter of starch by using enzymatic hydrolysis to convert high molecular weight starch into lower molecular weight starch. This modified starch has improved retention properties on fibres and can be effectively held in the papermaking process, reducing starch loss to water circulation.
Solution Approach 2:
The patent creates a composite system by combining starch with cationic polymers or other retention aids. This composite approach enhances the interaction between starch and fibres through electrostatic or adsorptive forces, improving starch retention on fibres and preventing starch loss to water circulation.
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 reduces the COD value of the wastewater, increases ash content and bursting strength of the paper, and minimizes microbial issues, thereby enhancing the overall papermaking process and product quality.
Implementation Method 1
adding a coagulant agent to the pulp flow or to an aqueous process flow comprising starch having low molecular weight; allowing the coagulant agent to interact with the starch having low molecular weight and optionally forming aggregates
Implementation Method 2
adding at least one flocculating agent, after the addition of the coagulant agent, to any flow, which comprises interacted coagulant agent, and forming a treated flow with starch comprising agglomerate(s)
Data Source
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AI summary
The invention relates to a method for making of paper, tissue, board or the like by using recycled fibre material as a raw material. The method comprises following steps: pulping recycled paper, board or the like in a pulper and obtaining a pulp flow comprising (i) an aqueous phase and (ii) at least recycled fibres and starch having low molecular weight, which are dispersed in the aqueous phase; adding a coagulant agent to the pulp flow or to an aqueous process flow comprising starch having low molecular weight; allowing the coagulant agent to interact with the starch having low molecular weight and optionally forming aggregates; and adding at least one flocculating agent, after the addition of the coagulant agent, to any flow, which comprises interacted coagulant agent, and forming a treated flow with starch comprising agglomerate(s); retaining at least part of the said aggregates and/or the said agglomerates to the fibres or to a web, which is formed.