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Glass melting reactions

by William Woelffel - published on , updated on

Glass is industrially produced from sand, soda ash, limestone and a couple of other minerals heated together until a lava-like, glassy liquid is reached. However, glass melting is much more than just melting.

Solid- and liquid-state chemical reactions, granular geometry and fluid mechanics are deeply intertwined. The strong coupling between local chemistry and global behavior make it a challenging and fascinating problem.

The raw materials used to produce industrial grain- and bubble-free glass a rather coarse (200-500 µm diameter), thus the heterogeneous granular microstructure of the glass batch affects the melting. It limits interspecies contact and reaction kinetics. Each grain will undergo transformations depending on its neighborhood. This leads to very different reaction paths, from early wetting and full dissolution to complete isolation.

In turn, this affects the transformations undergone by the granular packing. Upon heating up to 1500°C, eutectic melting, gas emissions, capillary forces and gravity reorganize the glass batch heap. Thermal conductivity, as well as local chemistry, are drastically affected.