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In this work, a comparative study on methanol to olefins (MTO) kinetics in fixed and fluidized bed reactors was conducted. Based on the analysis of experimental observations, a modeling approach that can be used to simulate both reactor configurations was proposed. The coke deposition was shown responsible for the difference of product selectivities for these two reactor configurations. In a fluidized bed reactor, the distribution of the coke deposition is spatially uniform, and evolves with time on stream. However, the coke deposition shows a distribution along the bed height in a fixed bed reactor, and olefins conversions were taken into consideration to account for the selectivity changes with time on stream. With the proposed model, we established a linkage between fixed bed reactors and fluidized bed reactors through coke deposition. By use of this model, it is possible to predict the performance of MTO reaction over SAPO-34 catalyst in fluidized bed reactor with experimental data obtained in fixed bed reactor, or verse vice. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quantitative analysis of the cluster characteristics in gas–solid turbulent fluidized bed by image processing. • Volume/mass fraction of each particle phase are characterized based on area statistics. • Distribution of the particle cluster characteristics are obtained under wide operating conditions. • Cluster cores movement brings a good solids mixing in the lateral direction. • Most cluster cores moved downward in turbulent fluidized bed. A two-step Otsu's method was applied to process the images of gas-solids flow field at multiple axial levels in a TFB with a H 0 / D ratio from 0.5 to 2.0. The flow field was segmented to a discrete particle phase, a dense particle phase, and a cluster core and a cluster cloud phases. The solids holdup, volume and mass fractions, and the velocity vector field of each phase were analyzed by postprocessing. The frequency, size, shape, and velocity of the cluster cores were also extracted. The increasing H 0 / D ratio results in an increase in solids holdup in each phase and a decrease in the mass and volume fraction of cluster clouds. A strong disturbance in the local flow field was resulted from the formation and movement of cluster cores and a more dynamic velocity change was found inside cluster clouds. The clusters were found to travel downwardly and with equal chances to move towards the center and the wall of the TFB at a low H 0 / D ratio with a high U g. [ABSTRACT FROM AUTHOR]

[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]