Gas release during melting and fining of sulphur containing glasses
article
At least 90 mass% of world's glass production uses some sulphate raw materials to improve melting kinetics and fining (removal of gas bubbles and dissolved gases) of glass melts. The batch reactions, especially in the presence of organic components or cokes, will influence the decomposition of sulphates or result partly in conversion to sulphides during batch melting. After batch melting, the remaining sulphur species, further react in, or with, the freshly molten glass, still containing sand particles and gaseous inclusions. Reactions may occur at different temperatures, associated with different glass melt viscosity levels. Evolved gas analysis of different batches, in specific (dry, wet, nitrogen) or simulated furnace atmospheres, is applied to investigate gas release (CO, CO<sub>2</sub>, SO<sub>2</sub>, O<sub>2</sub>) and sulphur reactions during batch heating and glass melt fining. This information is essential to predict foaming and fining behaviour and final glass redox (colour of final glass) for industrially applied raw material batch compositions and to find methods for reducing SO<sub>x</sub> emissions. Sulphate in batch reacts with cokes or char originating from organic components. This often results in sulphide formation. After melting-in of most batch components, sulphide and sulphate react and form SO<sub>2</sub> gas at temperature levels of about 1100-1350°C. This release of SO<sub>2</sub>-gas, causes bubble growth at these temperatures with viscosity levels above 50 Pa s. Higher temperatures are required to ensure sufficiently rapid removal of these bubbles from the melt by buoyancy forces. Residual sulphate may decompose at higher temperatures, depending on the residual sulphate content after the disappearance of sulphide from the melt. Thermal decomposition of sulphate only takes place when using batches without high carbon or organic material contents. In that case, bubble growth and bubble ascension in common soda-lime-silica glass melts are effective above 1450°C.
Topics
Batch compositionBatch reactionsBubble growthBuoyancy forcesDissolved gasEvolved gas analysisFurnace atmosphereGas bubbleGas releaseGlass meltsGlass productionMelting kineticsMolten glassOrganic componentsOrganic materialsSand particlesSoda-lime silica glassSulphur speciesThermal decompositionsViscosity levelBiological materialsFused silicaGlass manufactureOrganic carbon
TNO Identifier
408472
ISSN
00171050
Source
Glass Technology: European Journal of Glass Science and Technology Part A, 51(3), pp. 123-129.
Pages
123-129
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