Stirring Vessel Cover Heating for Glass Melt Contamination
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Solution Overview
Problem
Existing glass stirring processes fail to effectively reduce condensation-formed contaminants, such as volatile oxides like PtO2, B2O3, As4O6, Sb4O6, and SnO2, which lead to inclusion and blister defects in glass products due to temperature differences and the condensation of these oxides on cooler surfaces within the stirring apparatus.
Innovation Solution
The apparatus includes a stirring vessel cover with heating elements and a thermocouple to regulate the temperature of the aperture-defining surface and annular gap between the stirrer shaft and the cover, preventing condensation of volatile oxides by maintaining a consistent temperature and using a platinum-containing cladding to protect the surfaces from corrosive atmospheres.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If heating the shaft above the glass free surface is applied to reduce particulate contamination, then condensation of volatile oxides is reduced, but temperature stratification of condensation occurs and contamination is not fully eliminated
Solution Approach 1:
The heating system is segmented into multiple independent heating zones along the shaft, allowing different temperature levels to be maintained in different regions. This prevents uniform heating that causes stratification while effectively preventing condensation at critical locations.
Solution Approach 2:
Heating elements are strategically positioned at specific locations where condensation is most likely to occur, such as near the aperture-defining surface and in the annular gap. This localized heating approach targets the root cause of condensation without creating temperature stratification throughout the entire shaft.
2Object-affected harmful factors
If a disc-shaped shield is disposed between the glass free surface and upper portions of the stir chamber to reduce contamination, then condensation-formed contaminants are reduced, but temperature control of the glass free surface becomes difficult and the shield-shaft joint becomes an additional contamination source
Solution Approach 1:
The shield structure is completely removed from the system. Instead of using a physical barrier that interferes with temperature control, the solution extracts the problem source by directly heating the aperture-defining surface and annular gap to prevent condensation formation, eliminating the need for shields and their associated joints.
Solution Approach 2:
Heating elements serve as an intermediary mechanism to control condensation. Rather than using a physical shield that blocks heat transfer, the heating elements actively manage the thermal environment in the annular gap, preventing condensation through controlled heating without interfering with glass surface temperature regulation.
3Object-affected harmful factors
If the stirrer shaft and cover temperature are below the dew point of volatile oxides, then volatile oxides condense onto the shaft surface forming contaminants, but heating the shaft creates temperature stratification
Solution Approach 1:
Heating elements are positioned to pre-heat the aperture-defining surface and annular gap region before volatile oxides can condense. This preliminary heating action maintains temperatures above the dew point at critical locations, preventing condensation formation before it can occur.
Solution Approach 2:
The temperature parameter is locally modified in the annular gap and aperture region through targeted heating, creating a temperature gradient that prevents condensation only where needed. This selective parameter change maintains overall thermal stability while preventing localized condensation.
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 solution effectively reduces the formation and deposition of condensation-formed contaminants in the glass melt, enhancing the homogeneity and quality of the glass product by maintaining a controlled temperature environment and minimizing the introduction of defects.
Implementation Method 1
a first heating element 56 disposed in the first channel that heats the aperture-defining surface
Implementation Method 2
a second channel 60 comprising a thermocouple 58 disposed therein, and wherein a sensing end 62 of the thermocouple is positioned proximate the aperture-defining surface 40
Implementation Method 3
the volatile oxides contained with the stirring apparatus atmosphere can condense onto the surface of the shaft if the shaft and/or cover temperature are below the dew point of the oxides
Data Source
AI summary
The present invention is directed toward a method of reducing contamination of a glass melt in a stirring apparatus by an oxide material. The oxide material, such as platinum oxide, may be volatilized by the high temperature of the glass melt, and then condense on the inside surfaces of a stirring vessel, particularly the stirrer shaft and surrounding surfaces of the stirring vessel cover. A build-up of condensed oxide material may then be dislodged and fall back into the glass melt. Accordingly, an apparatus and method is provided that includes a heating element disposed adjacent an annular gap between the stirring vessel cover and the stirrer shaft. The heating element heats a surface of the stirring vessel cover bounding the annular gap and prevents condensation of volatile oxides that may flow through the annular gap.