3D Numerical Simulation of a Large Scale MTO Fluidized Bed Reactor

Multiphase flows and in particular dispersed flows are frequently encountered in a variety of important process facilities in the chemical industry; herein, the fluidized bed reactors. Whereas the internal and external solid fluxes in the fluidized bed reactors are generally determined by empirical correlations or prescribed in the Kunii–Levenspiel type of models, the two-fluid models serve as highly relevant in the progress of commercial reactors for processes such as the novel sorption-enhanced steam methane reforming (SE-SMR) technology because the solid flux incorporated in the two-fluid model allows for dynamic modeling of interconnected fluidized bed reactors. Nevertheless, the two- and three-dimensional two-fluid models are yet too computationally demanding for chemical process evaluation studies due to the complexity of the gas–solid flow in the bed. Hence, these models are not efficient for studies of the processes such as the SE-SMR technology where the solid particles are transported between reactor units for utilization and recovery of the characteristic solid property, i.e. CO2-capture and CO2-release. Thus, the aim of the present study is to derive a model that allows for a more complex description of the fluidized bed reactors relative to the frequently used Kunii–Levenspiel type of models. On the other hand, the model should not predict details in the flow, as the two- and three-dimensional two-fluid models, in order to ensure reasonable simulation costs. Hence, in this study, the classical SIMPLE algorithm is extended to compressible two-phase reactive flows. The governing equations are cross-sectional averaged to smooth out the details in the flow. The suggested dynamic one-dimensional Eulerian–Eulerian two-fluid model is applied to investigate the reactive gas–solid flows of the SMR and SE-SMR processes; and moreover, the simulation results are compared with the results of the more complex two-dimensional model with a solid stress closure based on kinetic theory of granular flow. The one-dimensional model predictions of the chemical process performance are in good agreement with the corresponding profiles predicted with the two-dimensional model. The deviations are larger comparing the internal flow details but these do not owe significant impact on the chemical process which to a large extent is determined by the imposed temperature in the reactor.

Modification of kinetic theory of granular flow for frictional spheres, part II: Model validation

A mathematical model was developed to investigate the flow behavior during the chemical sorption of carbon dioxide in a dense suspension upflow fluidized bed reactor. The two-fluid model with the kinetic theory of granular flow was applied to primarily investigate the carbon dioxide sorption performance similarity. The results indicated that the hydrodynamic similarity scaling parameter cannot achieve the carbon dioxide sorption performance similarity. Therefore, a modified set of scaling parameters were proposed to scale up the sorption fluidized bed reactor. The results indicated similar carbon dioxide removal percentages under different operating conditions for the same proposed scaling parameters.

Long-time simulation of catalytic MTO reaction in a fluidized bed reactor with a coarse-grained discrete particle method — EMMS-DPM

The risers of a conventional fluidized bed reactor and a stage fluidized bed reactor for the convention of methanol to olefins (MTO) were simulated using computational fluid dynamics. The reaction rates of the MTO reaction were validated to successfully match with the literature experiment. Then, the reactor stage parameters were examined by using the 2k design of the experiment method, including the number of reactor stages, the thickness of the reactor stage, and the wall temperature of the reactor stage. The stage circulating fluidized bed riser decreased the yield of ethene but increased the yield of propene and light olefins. From the obtained solid volume fraction profile, the stage circulating fluidized bed riser could reduce the back-mixing and increase the system turbulence, which promotes the light olefins of the MTO reaction yield. The wall temperature of the reactor stage did not significantly affect the chemical reaction in the circulating fluidized bed riser.

Chemical looping combustion of Victorian brown coal using Fe-based oxygen carriers

In this work, the business Computational Fluid Dynamics (CFD) is used for the numerical simulations of an air-solid fluidized bed container in the solid phase involving a multi-fluid Eulerian multiphase model and the Kinetic Theory of Granular Flow (KTGF). The height of the fluidized bed setup is 1.5 m while its diameter is 0.2 m. With it, a series of experimentations were obtained using Helium tracer to determine the Residence Time Distribution (RTD) at various normalized velocities, that is, mixing of air-solids at different degrees. 2 and 3 dimensions of the fluidized bed container are simulated. The main purpose of this study is to understand the hydrodynamic behavior of air-solid fluidized bed container through a framework of Eulerian multiphase model and to analyze the hydrodynamic behavior of the air-solids mixing. As a first approach, the CFD model is validated using the experimental results of the residence time study. The numerical results of RTD corresponded well with the experimental findings. This shows that the CFD modeling might be used to indicate the performance of a fluidized bed reactor. Key words: Computational fluid dynamics, fluidized bed, residence time distribution (RTD), gas-solids mixing, turbulence.

Experimental and numerical simulation of lignite chemical looping gasification with phosphogypsum as oxygen carrier in a fluidized bed

Numerical study on flow characteristics of hydrate slurry liquid-solid two-phase flow considering the adhesion between particles

Speeding up CFD simulation of fluidized bed reactor for MTO by coupling CRE model

Ocean floor mining : Pearson,J.S. Noyes Data Corporation, Publicity Department, Mill Road at Grand Avenue, Park Ridge, New Jersey 07656, USA (March 1975) 201 pp, $24

This work focuses on the numerical modelling and experimental validation of the hydrodynamic behaviour of a novel 50 kWth indirectly heated bubbling fluidized bed steam reformer. The hydrodynamic behaviour of fluidized beds with immersed vertical tubes and complex fluidized bed geometries in general have not been thoroughly investigated in terms of numerical modelling coupled with experimental validation for pilot scale reactors. Therefore, the present study contributes to the fluidized bed hydrodynamics numerical modelling field, while investigating a novel reactor concept. Simulations were performed employing the Two-Fluid Model approach, using the Kinetic Theory of Granular Flows (KTGF) and the adjusted Syamlal O’Brien drag model. The reactor’s hydrodynamic behaviour was simulated successfully, as showcased by a comparison of global hydrodynamic metrics (bed height, pressure drop) between computational and experimental results. Simulations were performed with and without considering an additional nitrogen gas feed on the side of the reactor (feeding system pressurization). Overall, for both cases, for realistic values of the particle restitution coefficient channelling of the gas flow near the reactor walls was observed. Larger bubbles appeared to be forming near the outer wall of the reactor for the no side-flow simulations. The opposite behaviour was encountered for the side-flow simulations due to stream-like behaviour of the side-flow moving up against the reactor’s outer wall. The choice to limit the simulations to a 72° symmetry domain was validated, indicating the possibility of further reduction. Finally, it was argued that increasing the reactor’s diameter could potentially lead to a reduction of the observed channelling of the fluidization media and improve the mixing achieved in the reactor and thus the conversion efficiency of the IHBFBSR during gasification applications.

Particulate modeling is often used to describe the kinematics of granular flow in mixers, granulators, and fluidized beds. An improved understanding of the rate processes associated with granulation can prove to be a valuable tool for modeling the evolution of particle size distributions. The kinetic theory of granular flow (KTGF) is a tool developed from the kinetic theory of gases to describe the kinematics found in granular media. Past work has shown that the KTGF can be used to describe the particle motion in a fluidized bed due to the inherently random particle movement caused by the fluid mechanics. Initially, it was thought that kinetic theory would not suffice when describing the kinematics in a high-shear mixer because of the shear motion in the mixer. However, recent work by Nilpawar et al. (in Proceedings: The 8th International Symposium on Agglomeration; The Industrial Pharmacists Group: Bangkok, Thailand, 2005) has shown experimentally that the collision frequency caused by random motion dominates over shear-induced collisions using measurements from the surface of the mixer. The present work attempts to support previous experimental findings by investigating the distributions of particle speed and velocity. The analysis is performed using discrete element modeling (DEM), a tool commonly used to simulate complex granular flow. This work demonstrates that, under idealized conditions, the KTGF is a very adequate means of describing particle flow. As the DEM process model becomes less ideal, the KTGF appears to be less successful in modeling the system.

The aim of the study described in this paper is to derive a fluidised bed reactor model that improve the description of the reactor performance relative to the KuniiLevenspiel type of models frequently used in chemical reactor engineering. The classical SIMPLE algorithm is extended to compressible multiphase reactive flows. The suggested one-dimensional Eulerian–Eulerian two-fluid model is applied to investigate the reactive gas–solid flows of the SE-SMR processes. Whereas the Kunii-Levenspiel models generally assumes a prescribed solid flux within the fluidised bed reactors, the two-fluid model derived in this study serves as highly relevant in the progress of commercial reactors for processes such as the novel SE-SMR technology because the solid flux incorporated in the two-fluid model allows for dynamic modeling of interconnected fluidized bed reactors. Moreover, the twoand three dimensional two-fluid models are yet too computational demanding due to the complexity of the gas–solid flow in the bed. Hence, these models are not efficient for studies of the processes such as the SE-SMR technology where the solid particles are transferred between reactor units for utilization and recover of the characteristic solid property, i.e. CO 2 -capture and CO 2 -release.

Numerical investigation of in situ gasification chemical looping combustion of biomass in a fluidized bed reactor