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Themethanol to olefins (MTO) process has been successfully commercializedin China and will potentially become an important route for lightolefins production. In this work, a modeling approach is presentedfor MTO fluidized bed reactor design and operation optimization. Thetwo-fluid model (TFM) where the solid phase shear viscosity and solidphase pressure are derived from kinetic theory of granular flow hasbeen used to model the solid–gas two-phase flows. The interphasedrag force is calculated by either the traditional Gidaspow modelor a recently developed EMMS-bubble model. The simulation study hasbeen performed for a fluidized bed reactor in a 16 kt/a DMTO unit.It has been shown that the Gidaspow model cannot predict a stabledense bed, while the EMMS-bubbling model could simulate the solidfraction distribution in the reactor reasonable well. A reaction modelbased on the simple MTO reaction kinetics has been implemented totest the effectiveness of the model approach. The simulation resultsshow that the methanol is converted rapidly just above the gas inlet.The selectivity of ethylene and propylene however are underpredicted,while the selectivity of CO2and other products are overestimated.It is suggested that a further extension of the EMMS model to a turbulentfluidized bed is important in order to get more quantitative results.Also the MTO reaction kinetics for a commercial DMTO catalyst, inwhich the coke formation kinetics should be included, is highly desired. [ABSTRACT FROM AUTHOR]

Scale-up of fluidized bed reactors has long been regarded as a big challenge in chemical reaction engineering. While traditional scaling theories are mostly based on hydrodynamics similarity, computational fluid dynamics (CFD) aided approach allows direct coupling between hydrodynamics and reaction factors and is expected to speed up the experiment-based scale-up process with lower cost. In this study, we aim to investigate the scale-up effects through simulations of a series of methanol-to-olefins (MTO) reactors of different sizes. The two-fluid model and energy-minimization multi-scale (EMMS)-based drag models are combined in simulations. The fluidization characteristics in terms of flow structures, velocity distribution, mass fractions of gaseous product and coke distribution are presented against available experimental data for different-sized reactors. It is found that typical hydrodynamic features can be reasonably predicted, while the prediction of reaction behavior shows growing discrepancy with increasing reactor size. Possible reasons are discussed in the last section along with future work presented for scale-up studies. [ABSTRACT FROM AUTHOR]

The methanol to olefins (MTO) process opens an economical and important route to produce light olefins. The design of MTO reactor borrows ideas from the reaction–regeneration configuration of the modern fluid catalytic cracking (FCC) units. However, their hydrodynamic behaviors are quite different in the sense that the fluidized bed for MTO reactions operates in different flow regime from that of FCC, calling for new modeling for scale-up. In addition, the coke deposited on catalysts greatly affects the MTO reaction while its generation is very slow. It normally takes tens of minutes or even hours for catalysts to reach the desired level of coke content. Time-dependent computational fluid dynamics (CFD) simulation of such a long process poses a big challenge to reactive multiphase flow modeling. To speed up it, we try to integrate the classic chemical reaction engineering (CRE) model with CFD. In particular, the continuous stirred tank reactor (CSTR) model is established to estimate the steady state distribution of coke content, which is then set as the initial distribution for CFD simulation to shorten the time to reach the steady state of reactive flows. Comparison with experimental data shows good agreement and also great speed-up ratio compared to traditional CFD simulation. [ABSTRACT FROM AUTHOR]