Silica Removal in Pulp Process via Thermal Dissolution
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Solution Overview
Problem
Existing methods for removing silica contaminants from wood chips in pulp production are inefficient and difficult to scale for large-scale pulp production, often resulting in clogged equipment due to incomplete particle separation and high silica content.
Innovation Solution
A system and method involving a vessel with a chip soaking zone where wood chips are submerged in a fluid at elevated temperatures for extended periods, followed by dilution and dewatering, utilizing silica separators to effectively remove silica contaminants, with a liquor-to-wood ratio of at least 10:1 and temperatures between 95-105°C to enhance silica dissolution and separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional chip washing systems (settling tank, circulation tank, hydrocyclone) are used, then silica removal is attempted, but the system becomes space-consuming and difficult to adapt to large-scale pulp production
Solution Approach 1:
The system is divided into functional sections: a soaking zone with heated fluid for silica dissolution, a dewatering device for liquid-solid separation, and a silica separator for contaminant removal. This segmentation allows each component to be optimized independently and reduces overall system footprint compared to traditional multi-tank washing systems.
Solution Approach 2:
The invention replaces mechanical washing systems (hydrocyclones, settling tanks) with a chemical-thermal approach using heated dilute acid to dissolve silica, followed by simple dewatering and filtration. This substitution eliminates complex mechanical separation equipment and reduces space requirements.
2Manufacturing precision
If multiple impellers are used in soak vessels, then contaminant removal is attempted, but the system becomes complex with many moving parts exposed to wear
Solution Approach 1:
The invention removes all moving parts (impellers, agitators) from the soak vessel system entirely. Instead of using mechanical agitation to remove contaminants, it relies on chemical dissolution using heated dilute acid and natural dewatering processes, eliminating wear and maintenance issues associated with moving parts.
Solution Approach 2:
The system uses the natural properties of the materials and processes: heated dilute acid spontaneously dissolves silica, the slurry self-dewateres through gravity in the dewatering device, and silica separators passively remove contaminants. No external energy input or mechanical action is required during the soaking and separation phases.
3Manufacturing precision
If traditional washing systems are used, then some particle separation is achieved, but the separation appears to be rather incomplete resulting in high silica content in dissolving pulp
Solution Approach 1:
The invention changes the chemical parameters (using dilute acid instead of water) and thermal parameters (heating to elevated temperatures) to transform silica from an insoluble contaminant into a dissolved state. This fundamental parameter change enables complete separation through dewatering and filtration, achieving high purity dissolving pulp without equipment clogging.
Solution Approach 2:
The invention replaces incomplete mechanical particle separation systems with a chemical dissolution approach followed by dewatering and filtration. This substitution achieves complete silica removal by converting the separation mechanism from mechanical size-based separation to chemical dissolution followed by phase separation, eliminating the clogging problems associated with mechanical separators handling high silica content materials.
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
This approach allows for efficient and cost-effective removal of silica contaminants, preventing equipment clogging and ensuring high chemical purity in dissolving pulp production, suitable for large-scale pulp mills.
Implementation Method 1
a chip slurry temperature in a chip soaking zone... to provide a chip slurry having a specified chip slurry temperature... temperatures between 95-105°C to enhance silica dissolution
Implementation Method 2
a dewatering device connected to the chip slurry transportation pipe for dewatering of the chip slurry transported therein and for providing a first flow of chip slurry... and for providing a second flow of silica-containing fluid
Data Source
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AI summary
The invention relates generally to a system and a method for the removal of silica contaminants from wood chips in a prehydrolysis kraft cooking pulp production process, and in particular to a system and a method in which silica is removed from a warm chip slurry containing chips that have been soaked in fluid for an extended soaking time at an elevated temperature.