Using residence time distribution to obtain figures of merit for melter studies

Abstract

Model studies were undertaken to map the flow paths in a glass melter in order to determine the residence time distribution of molten glass traversing the region from the batch cover to the spring tone. This, together with the temperature distribution measured at the same time, was used to compute the percentage reduction in a local inhomogeneity whose residence time in the melter is least, using a standard solution to the diffusion problem. This number is selected to gauge the extent of progress of homogenization, one of several physico-chemical rate processes taking place in the melter. As such it is one figure of merit to measure the capability of a melter design. A figure of merit was obtained for a so-called 'standard' situation and used as a basis against which to compare the effectiveness of other melter systems in transporting homogenized material to the refiner. In the cases examined it was found that the minimum melter residence time for material melting off the bottom of the batch was of the order of 10 h and that a greater than 95 % reduction in local inhomogeneity could be expected in the melter.