Iridium Melt Contact Surface for High-Purity Glass Refining
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Solution Overview
Problem
Current glass refining processes for high-purity optical glasses face challenges such as high residual bubble content, discoloration, and material contamination due to the use of expensive platinum alloys, which are reactive and limit refining temperatures, and require complex monitoring and control to prevent oxygen bubble formation.
Innovation Solution
A method and device using an iridium-containing unit with a melt contact surface that heats sections of the unit and adjusts the atmosphere to prevent oxygen bubble formation, allowing for higher refining temperatures and reduced use of toxic refining agents, while minimizing material contamination and improving bubble removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If platinum or platinum alloys are used as aggregate material for glass refining, then the glass can be refined effectively, but the material releases alloying elements into the melt causing discoloration and reduced transmission
Solution Approach 1:
The patent replaces expensive platinum aggregates with a more economical aggregate material (such as ceramic or graphite) that does not release harmful alloying elements into the glass melt. This disposable-like approach uses a material that can be replaced rather than maintaining the expensive platinum, thereby eliminating the discoloration issue while maintaining refining effectiveness.
Solution Approach 2:
The patent introduces an intermediary substance (refining agent such as arsenic oxide, antimony oxide, or bismuth oxide) that facilitates bubble removal without requiring direct contact between the aggregate and glass melt. The refining agent mediates the refining process by releasing gases that coalesce with bubbles and carry them to the surface, eliminating the need for platinum aggregates that cause discoloration.
2Productivity
If higher refining temperatures are used to reduce viscosity and increase bubble rising velocity, then refining efficiency improves, but glass attack on the aggregate wall increases leading to higher material input and strong yellowing
Solution Approach 1:
The patent uses a heat-resistant aggregate material (such as ceramic or graphite) that can withstand high refining temperatures without releasing harmful materials into the glass melt. This replaces platinum aggregates that limit the maximum temperature to 1600-1800°C and cause yellowing, enabling higher temperatures for improved refining efficiency.
Solution Approach 2:
The patent uses refining agents as intermediaries that enable efficient bubble removal at high temperatures without requiring direct aggregate-melt contact. The refining agents (such as metal oxides) decompose at high temperatures to release gases that facilitate bubble rise, allowing the aggregate to be thermally isolated from the melt and thus preventing material input and yellowing.
3Temperature
If platinum aggregates are used up to maximum temperatures of 1600-1800°C, then higher refining temperatures are achievable, but the material input into the glass melt increases causing strong yellowing
Solution Approach 1:
The patent employs a heat-resistant aggregate material (ceramic or graphite) that can withstand temperatures exceeding 1800°C without releasing harmful materials. This replaces platinum aggregates that begin to release material at 1600-1800°C, enabling higher refining temperatures without the yellowing problem.
Solution Approach 2:
The patent introduces refining agents as intermediaries that perform the bubble removal function at high temperatures without requiring the aggregate to be in direct contact with the melt. This allows the aggregate to be made of heat-resistant materials that can withstand higher temperatures without contributing harmful materials to the glass.
4Loss of time
If chemical refining agents are used to improve refining speed, then refining time is reduced, but toxic substances such as arsenic or antimony are introduced into the final glass product
Solution Approach 1:
The patent uses a disposable-like approach with heat-resistant aggregate materials that do not require toxic refining agents. The aggregate itself (such as ceramic or graphite) can withstand high temperatures and facilitate bubble removal through its physical properties alone, eliminating the need for toxic chemical refining agents that contaminate the glass.
Solution Approach 2:
The patent replaces toxic chemical refining agents with a non-toxic intermediary (the heat-resistant aggregate material) that facilitates bubble removal through physical mechanisms such as gas release upon heating or surface tension effects. This intermediary achieves rapid refining without introducing toxic substances like arsenic or antimony into the glass.
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 achieves high-temperature refining with reduced bubble inclusions and toxic agent usage, enhancing glass quality and reducing production costs by utilizing iridium's chemical resistance and high-temperature capabilities, resulting in improved transmission and reduced material contamination in the glass product.
Implementation Method 1
it has surprisingly been recognised that iridium-containing sections, in particular iridium-containing melt contact surfaces, prevent the formation of oxygen bubbles resulting from water dissociation in the melt
Implementation Method 2
at least the iridium-comprising section of the unit and/or the inlet and/or outlet is heated at least partially
Implementation Method 3
the absence of gas inclusions or bubbles and a minimum of discoloring inclusions are crucial for the interference-free transmission of electromagnetic radiation
Data Source
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AI summary
The present invention relates to an apparatus and a process for the continuous refining of low-viscosity glass melts in an aggregate. Apparatus and process are characterized in that the inclusion of bubbles and the occurrence of streaks in the glass end product are significantly reduced or even avoided completely if the melt contact surface of the aggregate comprises iridium or a high-iridium alloy as material.