Melting reactions in a granulated Na2O--CaO--SiO2 glass batch studied by x-ray diffraction and mass spectroscopy.

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Title:	Melting reactions in a granulated Na2O--CaO--SiO2 glass batch studied by x-ray diffraction and mass spectroscopy.
Authors:	Tsujimura, Tomoyuki¹ tomoyuki-tsujimura@agc.com, Tanaka, Chikao², Sakamoto, Osamu²
Source:	Glass Technology: European Journal of Glass Science & Technology Part A. Oct2012, Vol. 53 Issue 5, p202-210. 9p.
Subjects:	Fusion (Phase transformation), Granulation, X-ray diffraction, Mass spectrometry, Spray drying
Abstract:	The effects of granulation by spray drying and tumbling on the glass batch reactions and homogeneity of the melted glass were investigated for a Na2O--CaO--SiO2 system. Primary materials with a wide range of sizes were employed. The melting temperature of the mixture decreased when slurrying was carried out using fine (average particle size (D50)<1 µm) raw materials. This effect was marked in the case of spray dried granules. The glass homogeneity of the batch dried slurry improved when spray dried granules were employed. The glass homogeneity of the granules prepared by tumbling was inferior to that prepared by the slurrying process. CO2 degassing properties during heating of the raw materials and changes in crystalline phases indicated that the melting reactions of the spray dried granules started at a much lower temperature than those of the dry mixture. Thus, a chemical reaction occurred between Na2CO3 and SiO2 in the slurry. This reaction was accelerated when fine raw materials were employed, which resulted in high glass homogeneity. With increasing temperature, a new amorphous phase of 'Na2CO3--SiO2' was formed in the slurry and reacted with CaCO3 to form sodium calcium silicate. The melting mechanism of this newly formed material was different from that of conventional glass batches. [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

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Abstract:	The effects of granulation by spray drying and tumbling on the glass batch reactions and homogeneity of the melted glass were investigated for a Na2O--CaO--SiO2 system. Primary materials with a wide range of sizes were employed. The melting temperature of the mixture decreased when slurrying was carried out using fine (average particle size (D50)<1 µm) raw materials. This effect was marked in the case of spray dried granules. The glass homogeneity of the batch dried slurry improved when spray dried granules were employed. The glass homogeneity of the granules prepared by tumbling was inferior to that prepared by the slurrying process. CO2 degassing properties during heating of the raw materials and changes in crystalline phases indicated that the melting reactions of the spray dried granules started at a much lower temperature than those of the dry mixture. Thus, a chemical reaction occurred between Na2CO3 and SiO2 in the slurry. This reaction was accelerated when fine raw materials were employed, which resulted in high glass homogeneity. With increasing temperature, a new amorphous phase of 'Na2CO3--SiO2' was formed in the slurry and reacted with CaCO3 to form sodium calcium silicate. The melting mechanism of this newly formed material was different from that of conventional glass batches. [ABSTRACT FROM AUTHOR]
ISSN:	17533546