SiO2 Granulate Production via Freezing-Thawing and pH Control
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Solution Overview
Problem
Existing methods for producing SiO2 granulates are energy-intensive, risk contamination, and produce granulates with large particle sizes and poor homogeneity, making them inefficient and unsuitable for high-purity applications.
Innovation Solution
A method involving the adjustment of the pH of an aqueous SiO2 suspension to more than 7 using alkali-free bases like nitrogen hydrides, followed by deep-freezing and thawing, which breaks the hydrate shell around SiO2 particles, allowing for easy separation and stabilization, resulting in a finely divided granulate without the need for mechanical stirring or additional comminution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional granulation methods are used with intensive stirring and heating, then moisture removal is achieved, but energy consumption increases and contamination risk rises
Solution Approach 1:
The invention utilizes the phase transition of water from liquid to solid (freezing) and back to liquid (thawing) to achieve granulation. By freezing the SiO2 suspension and then thawing it, the ice crystal formation and melting process naturally aggregates the particles into granulates without requiring intensive stirring or heating, thereby significantly reducing energy consumption while maintaining manufacturing simplicity
Solution Approach 2:
The invention replaces the conventional mechanical stirring and heating system with a freezing-thawing process. Instead of using mechanical energy for intensive stirring and thermal energy for heating to remove moisture, the method uses the phase change of water to naturally aggregate particles and separate liquid phases, eliminating the need for complex mechanical and thermal processing equipment
2Productivity
If intensive contact between granulating tool and SiO2 dispersion is used, then moisture removal is supported, but contamination risk increases
Solution Approach 1:
The freezing-thawing process is a self-service mechanism where the suspension itself undergoes phase change to achieve granulation. The water in the suspension freezes and thaws, naturally aggregating particles and separating the liquid phase without requiring external granulating tools that would contact and potentially contaminate the SiO2 dispersion, thus maintaining high productivity while eliminating contamination risk
3Manufacturing precision
If conventional drying processes are used after freezing, then residual moisture is removed, but the process becomes long-winded and energy-intensive
Solution Approach 1:
The freezing step performs a preliminary separation of the liquid phase from the solid particles by forming ice crystals. When the frozen suspension is thawed, the liquid phase separates and can be easily removed by decanting or filtration before the final drying step. This preliminary action reduces the moisture content significantly beforehand, making the subsequent drying process much faster and less energy-intensive while maintaining high granulate purity
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 method produces high-purity, finely divided SiO2 granulates with a broad and homogeneous grain size distribution, reducing the risk of contamination and energy consumption, and is suitable for high-purity applications such as optically active materials and semiconductor components.
Implementation Method 1
deep-frozen and is subsequently re-thawed
Implementation Method 2
subsequently re-thawed to room temperature
Implementation Method 3
the original SiO2 particles will agglomerate and settle as a fine granulate on the bottom of the container
Data Source
AI summary
The invention relates to a process for producing SiO2 granules by freezing and re-thawing an SiO2 suspension, wherein a separation of liquid and sediment composed of agglomerated SiO2 particles occurs in the course of thawing, the liquid removed is decanted and the residual moisture in the sediment is removed by a drying step with formation of the SiO2 granules. According to the invention, an auxiliary comprising alkali metal-free bases in the form of nitrogen hydrides is added to the suspension to set the pH greater than 7.