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[Display omitted] • A population balance model is proposed for describing the evolution of coke content. • The PBM and multiscale CFD are efficiently combined to simulate an industrial-scale MTO reactor. • The primary light olefins and their selectivity are better predicted. • The relaxation time for expressing the effects of induction period in catalysts are considered. The coke distribution over shape-selective catalysts in fluidized bed reactors is critical to the selectivity of target products. A population balance model (PBM) is developed in this study to describe the evolution of coke distribution due to both reactions and circulation of catalysts. The PBM is coupled with multiscale computational fluid dynamics (CFD) to simulate a methanol-to-olefins fluidized bed reactor. A wide, uneven distribution of coke content can thus be predicted. The mass fractions of the desired products, ethylene and propylene, show better agreement with the experimental data than those without PBM. And the selectivity ratio of ethylene to propylene is also better predicted. Furthermore, the relaxation time of fresh catalyst is considered to express the effects of the induction period in MTO reactions. The reasonable prediction suggests that coupling PBM with multiscale CFD is helpful to understand MTO reactors and may find more application with respect to its optimization and scale-up. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of concentration models on fluidized bed measurements was studied. • Frequency dominant properties of bubble are unrelated to concentration models. • Selection of bubble threshold is strongly related to concentration models. • A general concentration model given in formula of a power function is proposed. Electrical capacitance tomography (ECT) has been widely applied in gas-fluidized bed measurements, which however is constrained by the sensor designs, image reconstruction algorithms and concentration models owing to the "soft-field" nature. Among the three factors, the concentration models that map the permittivity to solid concentration distribution are less understood. In this paper we present an experimental investigation on the effects of concentration models for the ECT measurements of gas-fluidized beds containing Geldart's group A particles. The results show that the bubble velocity, bubbling frequency and fluidization regime transition velocity are intrinsic whatever the concentration model employed. However, the time-averaged solid concentrations measured by ECT with the conventional concentration models are usually higher than the corresponding results obtained by the bed expansion experiments in homogeneous fluidization. It has been further found that the concentration models can significantly influence the threshold selection in identifying the bubbles and surrounding emulsion phase in gas-fluidized beds. Thus, a new concentration model given in the formula of a power function (ϕ = G α) has been proposed, with the optimal exponent α obtained via the least-square fitting of solid concentration in bed expansion during homogeneous fluidization. The model is robust and the sensitivity analysis shows that the variation of time-averaged solid concentration is negligible (≤ 3%) suppose that α changes by ± 20%. [ABSTRACT FROM AUTHOR]