A 3D CFD-DEM Methodology for Simulating Industrial Scale Packed Bed Chemical Looping Combustion Reactors

Abstract

Design of industrial scale packed bed reactors can be aided by using computational fluid dynamics (CFD)-discrete element method (DEM) simulation for understanding the transport phenomena. However, conducting CFD-DEM simulation for the whole large-scale packed bed reactor is computationally prohibitive, which limits the usage of this tool. Hence, a methodology has been developed to identify the segments of the bed, which can serve as a good representative for the CFD simulation of large industrial scale packed bed reactors. Two segments, a cylindrical cut-segment and a wall-segment, have been used to represent the core central region of packed bed and the near wall region of packed bed, respectively. The methodology determines the size (diameter and height) of the cylindrical bed cut-segment that can be a good representative for the large-scale packed bed reactor. The segments are then used to obtain the information on transport phenomena (friction factor coefficients (pressure drop) and the heat transfer/mass-transfer coefficients) for packed beds made of spherical particles and non-spherical particles. CFD simulations have been conducted on the DEM generated packing segments for a wide particle Reynolds number range (from laminar to turbulent regime) to develop the correlations. The proposed methodology (on cut-segment and wallsegment) has been validated for spherical particle packed bed by comparing results to well-established correlations (such as Ergun equation for pressure drop, Wakao correlation and multiparticle Ranz−Marshal correlation for particle heat transfer coefficient, and Dixon−Lubua and Colledge−Paterson correlation for wall heat transfer coefficient). The methodology is then applied to understand the transport phenomena and to develop correlations for long cylindrical pellet (aspect ratio 7) and flutedring. The pressure drop correlation obtained for the long cylindrical pellet (aspect ratio of 7) packed bed has been compared to the correlation for cylindrical pellet with aspect ratio of 5.77 (obtained by Nemec; Nemec, D.; Levec, J. Chem. Eng. Sci. 2005, 60, 6947). The comparison shows that the effect of increasing aspect ratio on pressure drop is captured as per the expected trend. The methodology has been applied in a chemical looping combustion reactor based on the pressure drop and heat transfer results. Thus, the proposed CFD-DEM methodology offers a computationally efficient way of understanding the transport phenomena in an industrial scale reactor through simulating a methodically selected segment inside the reactor. This enables design and performance assessment of such reactors.

Multiscale modelling of CO2 reduction to methanol over industrial Cu/ZnO/Al2O3 heterogeneous catalyst: Linking ab initio surface reaction kinetics with reactor fluid dynamics

“…Beds of the PBR where prepared using the distinct element method (DEM) which simulates realistic packing of the PBR (de Moura Teixeira, 2013; Eppinger et al, 2011;Kuroki et al, 2009;Tabib et al, 2013;Tsory et al, 2013;Vollmari et al, 2015;Wehinger et al, 2015;Zobel et al, 2012). The simulations were conducted with Blender (Blender Foundation), which is often used in scientific studies (Boccardo et al, 2015;Icardi et al, 2014;Pavlišič et al, 2018;van Gumster, 2015).…”

“…, meshing the whole reactor would require an excessive number of computational cells, resulting in impractically long computational times. Previous studies have shown that it suffices to find a representative cut-segment of the bed (D cut /d p > 4 for arbitrary particles) (Tabib et al, 2013).…”

Computational fluid dynamics simulation for chemical looping combustion of coal in a dual circulation fluidized bed

“…Based on the description of the fluid dynamics of the reactor, two categories of models can be identified [8]: macroscopic fluid dynamics models (MFD) [9][10][11][12][13] and computational fluid dynamics models (CFD). Based on the description to the particle phase dynamics, the CFD models can also be divided into three categories: the two-fluid model, the CFD-DEM (discrete element method) model [14,15], and the CPFD (computational particle fluid dynamics) model [16,17]. In CFD simulation based on the Navier-Stokes equation for describing the fluid flow, less artificial factors existed.…”

Hydrodynamic analysis of gas‐liquid‐liquid‐solid reactors using the XDEM numerical approach

“…In this method, normally time and volume average conservation equations are solved for each phase separately . The second method is suitable for multiphase systems, including a disperse or particulate phase, in which a continuum method is applied to the continuous phases and a particle tracking method to the discrete phase . In our previous works,, we developed an Eulerian‐Lagrangian method to model trickle bed reactors, including three phases of gas‐liquid‐solid.…”