Comprehensive, Three-dimensional CFD Model of a Reacting Char Bed, 2004 International Chemical Recovery Conference

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This paper describes the development of a three-dimensional computer code that predicts fluid mechanics, heat and mass transfer and chemical kinetics within a reacting char bed and its application to black liquor. Finite-volume equations estimate pressure drop through porous media with the Ergun equation, a semi-empirical equation based on Darcy’s law, to predict fluid flow. Gas and particle temperatures are calculated using established albeit mostly empirical heat transfer correlations together with heat released/absorbed by chemical reactions. The model predicts air flow, including penetration depth into the bed and heat transfer between the bed and the surrounding gases. A companion project collecting experimental information from laboratory and commercial scale beds should provide experimental data for validation in the near future. In the absence of such data, current validation consists only of qualitative analysis of quantitative predictions. This model has not yet been incorporated into a comprehensive computer code, but its use in such codes is illustrated based on previous work coupling simpler bed models with CFD codes.