21 December 2022

Foaming in industrial glass tanks is typically an undesirable phenomenon, as it obstructs heat transfer from burner flames into the melt. This not only increases fuel consumption, but can also lead to overheating of the crown and insufficient melt temperatures. During his PhD research, Read-Ox founder Paul Laimböck conducted an in-depth study on this topic, culminating in the thesis Foaming of Glass Melts. Given the growing importance of energy efficiency and product quality, the decision was made to publish this work as an eBook.

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Topics:

Gas production in the melt (gas-producing redox reactions)
* Effect of redox-active additions (sulfate, iron, carbon/coke, nitrate)
* Effect of glass melt basicity (soda adn alumina levels)
Glass Foam stability mechanisms
Foaming behaviour of recycling glass mixtures
Foaming under oxy-fuel firing conditions
Foam control strategies, including a formula to determine optimal sulfate levels based on:
* Hotspot temperature
* Bulk glass composition
* Water level in atmosphere (air-fuel vs. oxy-fuel firing)

…

A schematic illustration shows the experimental setup used to investigate the foaming behavior of various glass-forming batches under different atmospheric conditions. This setup enabled simultaneous measurement of gas release and volume expansion of both the batch and the melt as a function of temperature.

 

The figure illustrates the batch expansion and foaming behavior of an oxidized, sulfate-containing glass-forming batch. The data shows moderate expansion during the initial heating phase, primarily due to the entrapment of small amounts of CO₂, CO, and SO₂ within the batch. However, vigorous foaming occurs above 1450°C, triggered by the thermal decomposition of sulfate, which releases SO₂ and O₂ gases in a molar ratio of 2:1.