Modeling of sand grain dissolution in industrial glass melting tanks

A combination of a microscale and a macroscale model, describing dissoln. of sand grains in batch blankets or in the molten glass, is presented. The macroscale model is based on a 3-dimensional calcn. procedure to det. the temp. distributions and the flows in industrial glass-melting tanks. With microscale models, using mass transfer relations for diffusional transport, the dissoln. rate of single sand grains can be calcd. The dissoln. of the sand is detd. by following a large no. of single grains during their trajectories through the batch blanket and the molten glass in the glass melting tanks. The dissoln. rate of a sand grain is calcd. for the temps. and flow conditions in every vol. element in the tank through which the grain proceeds. The dissoln. rate in the batch blanket depends strongly on temp. and the stage of the dissoln. process. Initially the very fast shrinkage rate of the grain as temps. exceed 1200 Deg results within 10 min in the dissoln. of more than 50% of the sand in the blanket. Forced and free convection in the glass melt leads to increase in the dissoln. rate, up to a factor 5 compared to motion-free conditions. Forced bubbling for instance results locally in extremely high mass transfer rates and often improves the melting performance of industrial glass furnaces. [on SciFinder (R)