Sulphate decomposition and sulphur chemistry in glass melting processes

ISSN： 0017-1050

Source： Glass Technology - European Journal of Glass Science and Technology Part A, Vol.46, Iss.2, 2005-04, pp. : 39-46

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Abstract

The chemical reactions of sulphur components during the heating of raw material batches for the production of soda–lime–silica glasses are presented. The effect of reducing components such as coke in the batch on the release of sulphur gases is investigated. The solubility of sulphur species in molten soda–lime–silica glasses has been derived for different temperature levels and water contents of the melt, depending on the oxidation state of the melt. The sulphate decomposition reaction equilibrium for float glass melts and the sulphite solubility are shown as function of temperature. These data are used to determine the amount of fining gas evolution and the onset temperature of sulphate fining processes in glass melts. Water infiltration into the glass melt leads to lower sulphate retentions in the glass and lower fining onset temperatures, whereas the volume of fining gases increases. The interaction between sulphur and other polyvalent ions in glass melts during fining and during the cooling of the melt is discussed. The formation mechanism of the amber chromophore is explained and the effect of oxidation state and temperature on the formation of the chromophore elements: Fe³⁺ –S²⁻ is presented.