Melting behavior of continuously charged loose batch blankets in glass melting furnaces

Abstract

The paper reports on numerical methodology for predicting the melting of a two-dimensional, axially fed glass batch blanket. In the absence of rheological data for commercial glass batch mixtures, it is assumed that each grain within batch acquires a horizontal velocity, which is constant and equal to that of charging speed throughout the transformation process. The vertical motion of batch is obtained from Newton's first law of motion by ignoring all the internal shear stresses in the vertical direction. During the transformation, the chemical reactions are simulated using modified form of Arrhenius equation. The gas percolation within the blanket is considered and the flow is predicted using Darcy's law, and heat exchange between gas and solid phase is accounted for. The formation of molten glass layer on the top of the blanket is modeled by appropriate transport equations, and the penetration of radiation from the combustion space incident on this semitransparent layer is approximated by spectral, two-flux equations. The system of equations is solved using the marching method of Patankar and Spalding [16]. The model is utilized to generate some sample results under idealized conditions. Accordingly, the heat flux at the top surface is assumed to be due to an effective gas-crown temperature. At the bottom surface, the heat flux from the melt was simulated by imposing a constant heat flux over the entire batch. A baseline condition is set for each parameter and parametric calculations were performed for a range of physically plausible conditions to determine the effects of the bottom heat transfer rate and preheating on the batch melting characteristics.