Mathematical correlations in two-phase modeling of fluidized bed adsorbers

Abstract

Choosing proper formulas for estimating different variables is imperative when modeling a fluidized bed using two–phase theory. In this study, a two–phase model was used to model the adsorption of volatile organic compounds (VOC) in a multistage fluidized bed adsorber. Two different approaches were used to describe gas flow and mixing in the emulsion phase, perfectly mixed (EGPM: Emulsion Gas – Perfectly Mixed) and plug flow (EGPF: Emulsion Gas – Plug flow). The impact of different formulas for estimating bubble size, bed porosity at minimum fluidization velocity, adsorption and interphase mass transfer coefficients, as well as tortuosity on the performance of the model was determined by comparing the model outcomes with experimental data. Finally, using a large dataset obtained from fluidized bed adsorption systems with different adsorbents, adsorbates, bed sizes, and operating conditions, a broadly-applicable set of formulas was suggested which could be used to describe the behavior of different countercurrent fluidized bed adsorbers. From the results, the two–phase model could successfully predict the experimental data, with EGPF showing better performance than EGPM. Proper use of formulas, especially those describing bed voidage and interphase mass transfer coefficient, could markedly improve the performance of the two-phase model. The two-phase model using the set of formulas proposed here was able to accurately replicate a large dataset of fluidized bed adsorption experiments over a wide range of operating conditions.