Reducing Fluorescence in Recycled Pulp via Sequential Oxidation
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Solution Overview
Problem
Fluorescent whitening agents in recycled paper pulp cause operational issues in de-inked pulp and paper mills, affect product quality, and pose potential health hazards, necessitating an efficient method to reduce or remove them, especially for food-grade applications.
Innovation Solution
A process involving the simultaneous or subsequent addition of chlorine dioxide and sodium hypochlorite to pulp slurry, with chlorine dioxide added first, effectively reduces fluorescence, using specific chemical amounts and timing to achieve near-zero fluorescence without significant brightness increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If fluorescent whitening agents are added to enhance brightness, then apparent brightness is improved, but operational problems occur in de-inked pulp mills and product quality is impaired
Solution Approach 1:
The patent removes fluorescent whitening agents from recycled pulp through chemical treatment with chlorine dioxide and sodium hypochlorite, extracting the harmful fluorescent compounds while preserving the pulp fibers for further processing
Solution Approach 2:
The patent changes the chemical parameters of the pulp by introducing specific oxidizing agents (chlorine dioxide and sodium hypochlorite) in controlled amounts and sequences, transforming the fluorescent compounds into non-fluorescent degradation products
2Illumination intensity
If fluorescent whitening agents are used to enhance brightness, then apparent brightness is improved, but color and brightness control is affected
Solution Approach 1:
The patent extracts fluorescent whitening agents from the pulp using sequential chemical treatment, removing the substances that interfere with color and brightness control measurements and processing
Solution Approach 2:
The patent implements UV-based on-line color sensors with control loops that can accurately measure and control color and brightness parameters after fluorescent agents are removed, enabling precise manufacturing control
3Illumination intensity
If fluorescent whitening agents are added to improve brightness, then apparent brightness is improved, but health hazards are created through leaching
Solution Approach 1:
The patent extracts fluorescent whitening agents from recycled pulp through chemical oxidation with chlorine dioxide and sodium hypochlorite, removing the leachable compounds that pose health hazards in food-grade applications
Solution Approach 2:
The patent uses strong oxidizing agents (chlorine dioxide and sodium hypochlorite) to rapidly degrade fluorescent whitening agents into non-hazardous compounds, eliminating health risks associated with leaching
4Object-generated harmful factors
If chlorine dioxide is used to reduce fluorescence, then fluorescence is reduced, but residual chlorine dioxide hazards remain
Solution Approach 1:
The patent introduces sodium hypochlorite as an intermediary substance that reacts with and neutralizes residual chlorine dioxide, converting it into less hazardous compounds while maintaining fluorescence reduction benefits
Solution Approach 2:
The patent converts the potentially harmful residual chlorine dioxide into beneficial or neutral substances through reaction with sodium hypochlorite, transforming a hazard into a safe end state
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 process achieves significant reduction or elimination of fluorescence, reducing chemical usage and preventing residual chlorine dioxide-related hazards, while maintaining pulp quality and safety for food-grade applications.
Implementation Method 1
contacting the pulp, which contains fluorescent agents, with a combination of chlorine dioxide (CIO2) and sodium hypochlorite (or a derivative of sodium hypochlorite) in amounts sufficient to reduce the fluorescence of the pulp
Data Source
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AI summary
The invention is directed to a method for reducing fluorescence in recycled pulp, wherein the method includes: contacting a pulp slurry containing fluorescent agents with chlorine dioxide; and contacting the pulp slurry with a sodium hypochlorite component, in an amount sufficient to reduce the fluorescence of the pulp; wherein the pulp is contacted with sodium hypochlorite component simultaneous with or after contact with chlorine dioxide.