Impact of Melter Internal Design on Off-Gas Flammability.

摘要

It is critically important to understand that the global kinetics scheme used in the DWPF melter combustion model is not just concerned with the intrinsic kinetics of CO and H2 oxidation only. Instead, it is based on the global combustion kinetic parameters that incorporate the effects of fluid mixing and heat transfer in the melter vapor space as well as intrinsic kinetics, and the fluid mixing and heat transfer are both greatly influenced by the design of melter internals such as configuration of the melter cavity and vapor space heaters. The data needed to derive the global kinetic parameters used in the current DWPF combustion model were obtained during the Scale Glass Melter (SGM) Run 9 with the formic-acid flowsheet feed. The SGM was a . scale DWPF melter based on melt surface area or . on a linear scale; the SGM had a 4-feet diameter melt surface compared to 6-feet for the DWPF melter, and the configuration of the air purge and offgas exhaust ports as well as the vapor space heaters were the same in both melters. Thus, the SGM was a large prototypic melter, and its cold cap behavior as well as the mode of fluid mixing and heat transfer in the vapor space were similar to those of the DWPF melter. Furthermore, data from pilot- and full-scale melter runs have shown that with comparable feed chemistry off-gas surging potential generally increases with increasing melter size. Therefore, it would be desirable to obtain the baseline off-gas surge data for the glycolic-acid flowsheet feed using a melter that has as prototypic melter internals and as large a melt surface as practically possible, since the scale-up of data obtained from a smaller, non-prototypic melter will be much more challenging, if not impossible. Therefore, the goal of this study was to show explicitly the impact of melter internal design on the off-gas flammability by checking how well or how poorly the existing DWPF models would predict available off-gas data obtained from the melters with varying internal designs preferably using feeds based on the formic-acid reductant. The impact of melter internal design on the fluid mixing and, to a lesser extent, heat transfer was investigated further by performing computational fluid dynamics (CFD) modeling. This report summarizes the results of these model runs and the findings from the comparison of model results to data.