Peroxide Content Measurement in Pulp Suspension
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Solution Overview
Problem
Current methods for controlling the peroxide bleaching stage in pulp processing are inefficient due to poor correlation between laboratory and on-line measurements of total peroxide content, with existing methods either being complex or prone to deviations from sample handling and equipment maintenance, and failing to accurately determine the active perhydroxyl ion content.
Innovation Solution
A method and apparatus for determining the total peroxide content in pulp suspension by adjusting the pH of a sample to either convert all peroxide molecules to perhydroxyl ions or vice versa, using an electrochemical measuring device with pH control, allowing for precise measurement of total peroxide content that correlates well with laboratory titrating methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laboratory titrating methods are used to measure total peroxide content, then measurement accuracy is improved, but measurement time and operational complexity increase
Solution Approach 1:
The patent replaces the manual laboratory titrating method with an automated on-line electrochemical measuring device that uses a sensor to detect peroxide content electrically, eliminating the need for manual sample handling, titration preparation, and visual endpoint detection, thereby reducing measurement time while maintaining accuracy
Solution Approach 2:
The measuring device performs self-calibration and automatic measurement without requiring operator intervention for each measurement cycle, enabling continuous on-line monitoring of total peroxide content in the pulp suspension
2Productivity
If on-line electrochemical measuring devices are used to monitor peroxide content, then real-time control is improved, but measurement reliability deteriorates due to poor correlation with laboratory methods
Solution Approach 1:
The patent changes the measurement parameter from monitoring only perhydroxyl ions to measuring total peroxide content by controlling pH to convert all peroxide forms to perhydroxyl ions, ensuring the measurement reflects the actual total peroxide dosage in the suspension and correlates with laboratory methods
Solution Approach 2:
The patent introduces pH control as an intermediary mechanism that converts peroxide molecules to perhydroxyl ions before measurement, ensuring that the electrochemical sensor measures the complete peroxide content rather than only the active perhydroxyl ion fraction, thereby improving correlation with total peroxide laboratory measurements
3Quantity of substance
If pH is controlled to maintain high perhydroxyl ion content for effective bleaching, then bleaching effect is improved, but total peroxide content measurement becomes inaccurate
Solution Approach 1:
The patent applies preliminary pH adjustment to the sample before measurement to convert all peroxide molecules to perhydroxyl ions, ensuring that the measurement reflects total peroxide content rather than only the fraction present at the process pH, thereby resolving the discrepancy between process optimization and measurement accuracy
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
Enables precise control of the bleaching stage, improving pulp brightness and reducing chemical usage by accurately measuring and controlling the peroxide dose, with the apparatus being easy to use, quick, and suitable for on-line monitoring.
Implementation Method 1
measuring methods based on electrochemical measuring are generally used. These methods measure the electric current produced by a filtrate sample taken from the pulp suspension
Implementation Method 2
The reaction is an equilibrium reaction, which depends on the temperature and pH of the solution... when the pH is below 9, hydrogen peroxide is approximately 100% in peroxide molecular form. Whereas when the pH is over 11, i.e. very alkaline, approximately 100% of hydrogen peroxide is in perhydroxyl ion form
Implementation Method 3
The bleaching effect of the peroxide is based on oxidizing the colored chromophore radicals of lignings and rendering them colorless
Data Source
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AI summary
A method and an apparatus for determining the total peroxide content of a cellulose pulp suspension in the pulp suspension bleaching stage, wherein the bleaching chemical is peroxide. A sample is taken from the pulp suspension, which sample is measured in a measuring device (25, 25'). Before measuring, the pH of the sample is adjusted and after that the total peroxide content or the perhydroxyl content of the sample is measured, of which measurement the total peroxide content of the sample is determined.