Further analysis of the near-plug gas flow conditions in micro gas-solid fluidized beds

This work presents a theoretical analysis of the near-plug gas flow conditions in micro gas-solid fluidized beds based on the simple one-dimensional dispersion model. The analysis is validated by comparison with the experimental results reported in the literature. It concludes that gas flows can be considered near-plug flow only when: 1) the gas RTD curve is symmetrically shaped; 2) the product of RTD peak height E(t)h and variance σt (i.e., E(t)hσt) approximates 0.4; and 3) E(t)h is greater than 1.0 s−1 (dimensionless Eθ,max > 2.82) or σt2 < 0.25 s2 (and (dimensionless σθ2 > 0.02). This work further improves the criterion for the near-plug flow of gas in micro fluidized beds originally proposed by Geng et al. (CEJ, 351 (2018) 110–118). [Display omitted] •The Pe or Da, g is inappropriate for defining gas flow conditions in MFBs.•Uncertainties in estimating bed voidage and height contribute to the biased Da, g and Pe.•Measuring gas RTD is a reliable approach to determine gas flow conditions in MFBs.•A near-plug flow of gas is characterized by an RTD curve in MFBs.•A near-plug flow of gas in MFB is attained by careful selections of operating conditions.