Optimization and control of selenium chemistry and color in flint glass melts

The selenium chemistry in the decoloration process in flint glass melts was investigated both in commercial practice and in laboratory. Samples were taken from two furnaces of a flint glass production site, analysed with respect to Se, Fe, redox state, and color. Color defects during production could be attributed to an unduly high Se loss which, in turn, could be traced back to production periods with too high temperatures in the combustion space. Pull rate changes did, however, not have an unanimous effect. In lab experiments, the relation between redox state, total Se, Co, Fe, S on the one side, and the resulting color on the other side, were thoroughly investigated in an empirical way. Due to the very loss Se level, a speciation of Se could, however, not be performed. With respect to 0.05 % iron containing glass, the ratio Fe2+ to total Fe should not exceed 0.12 and the amount of sulfate should be ~ 0.4 wt. %. Otherwise the Se loss might reach 100 %. Oxidizing conditions with a redox number about 15 was also found the optimum condition for the decoloration. The same absorption range of spectra between 220 ppm Se-iron free glass and 2 ppm Se-iron containing industrial glass, suggests FeSe may act as the dominating coloring agent in the decoloration process. This got along well with the constructed phase stability diagrams of Na-O-Se system. Finally, a strategy of vectors addition in the L*a*b* color space diagram was developed by which optimal decoloration conditions can be swiftly determined. The strategy was verified with a glass containing total Fe as high as 0.1 wt. %.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2005

Author dc:creator

• Jitwatcharakomol, Tepiwan

Contributors dc:contributor

• Conradt, Reinhard

• info:eu-repo/classification/ddc/660
• Weißglas
• Glasherstellung
• Glasschmelze
• Entfärbung
• Selen
• Oxidationszahl
• Technische Chemie
• selenium

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121652%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:59911