Comparison of CFD Simulation and Simplified Modeling of a Fluidized Bed CO2 Capture Reactor

2016 ◽  
Vol 14 (1) ◽  
pp. 133-141 ◽  
Author(s):  
Daoyin Liu ◽  
Zhonglin Zhang ◽  
Yaming Zhuang ◽  
Xiaoping Chen
Keyword(s):  
Fluidized Bed ◽  
Flow Model ◽  
Cfd Simulation ◽  
Plug Flow ◽  
Fluidized Bed Reactors ◽  
Cfd Model ◽  
Two Phase ◽  
Multiphase Cfd ◽  
Reactor Models ◽  
Dem Model

AbstractCO2 capture using solid sorbents in fluidized bed reactors is a promising technology. The multiphase CFD model is increasingly developed to study the reactors, but it is difficult to model all the realistic details and it requires significant computational time. In this study, both the multiphase CFD model (i.e., CFD-DEM model coupled with reaction) and the simplified reactor models (i.e., plug flow model and bubbling two-phase model) are developed for modeling a fluidized bed CO2 capture reactor. The comparisons are made at different gas velocities from fixed bed to fluidized bed. The DEM based model reveals a detailed view of CO2 adsorption process with particle flow dynamics, based on which the assumptions in the simplified models can be evaluated. The plug flow model predictions generally show similar trends to the DEM model but there are quantitative differences; thus, it can be used to determine the reactor performance limit. The bubbling two-phase model gives better predictions than the plug flow model because the effect of bubbles on the inter-phase mass transfer and reaction is included. In the future, a closer combination of the multiphase CFD simulation and the simplified reactor models will likely be an efficient design method of CO2 capture fluidized bed reactors.

Development of Fast Solving Monolith Reactor Simulators: Computational Fluid Dynamics Studies of Methane Oxidation

2018 ◽  
Vol 14 (2) ◽  
Author(s):  
Mopeli Khama ◽  
Randhir Rawatlal ◽  
Glenn Jones
Keyword(s):  
Flow Model ◽  
Cfd Simulation ◽  
Plug Flow ◽  
Reaction Diffusion ◽  
Reaction Diffusion Equation ◽  
Cfd Model ◽  
Monolith Reactors ◽  
Mass And Heat Transfer ◽  
Complex Boundaries ◽  
Wall Mass

Abstract The optimisation of complex geometries such as that of monolith reactors can be supported by computation and simulation. However, complex boundaries such as those found in multi-channel monoliths where mass and heat transfer of characteristic of the reaction diffusion equation render such simulations of extremely high computational expense. In the first step toward developing a fast-solving hybrid simulation, a detailed CFD simulation was used to obtain the unsteady state, spatial temperature and concentration (and hence reaction rate) profiles for a range of input conditions. The results of the CFD simulation were then accepted as the benchmark to which faster-solving models were measured against to be considered as viable descriptions. The model evaluated here is a modified plug flow with effectiveness factor correction for wall mass-transfer. A close agreement between both temperature and species mole fraction profiles predicted from the modified plug flow model and a detailed CFD model was found with R2 values of 0.994 for temperature. The time needed to find a converged solution for plug flow model on an Intel(R) Core(TM) i5-5300U CPU @ 2.30 GHz workstation was found to be 53 seconds in comparison to 1.3 hours taken by a CFD model.

scholarly journals Comparative Study of CFD and LedaFlow Models for Riser-Induced Slug Flow

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3733
Author(s):  
Rasmus Thy Jørgensen ◽  
Gunvor Rossen Tonnesen ◽  
Matthias Mandø ◽  
Simon Pedersen
Keyword(s):  
Slug Flow ◽  
Oil And Gas ◽  
Cfd Simulation ◽  
Numerical Models ◽  
Oil And Gas Industry ◽  
Test Facility ◽  
Cfd Model ◽  
Two Phase ◽  
Transient Model ◽  
Vof Model

The goal of this study is to compare mainstream Computational Fluid Dynamics (CFD) with the widely used 1D transient model LedaFlow in their ability to predict riser induced slug flow and to determine if it is relevant for the offshore oil and gas industry to consider making the switch from LedaFlow to CFD. Presently, the industry use relatively simple 1D-models, such as LedaFlow, to predict flow patterns in pipelines. The reduction in cost of computational power in recent years have made it relevant to compare the performance of these codes with high fidelity CFD simulations. A laboratory test facility was used to obtain data for pressure and mass flow rates for the two-phase flow of air and water. A benchmark case of slug flow served for evaluation of the numerical models. A 3D unsteady CFD simulation was performed based on Reynolds-Averaged Navier-Stokes (RANS) formulation and the Volume of Fluid (VOF) model using the open-source CFD code OpenFOAM. Unsteady simulations using the commercial 1D LedaFlow solver were performed using the same boundary conditions and fluid properties as the CFD simulation. Both the CFD and LedaFlow model underpredicted the experimentally determined slug frequency by 22% and 16% respectively. Both models predicted a classical blowout, in which the riser is completely evacuated of water, while only a partial evacuation of the riser was observed experimentally. The CFD model had a runtime of 57 h while the LedaFlow model had a runtime of 13 min. It can be concluded that the prediction capabilities of the CFD and LedaFlow models are similar for riser-induced slug flow while the CFD model is much more computational intensive.

scholarly journals Comparative simulation study of gas-phase propylene polymerization in fluidized bed reactors using aspen polymers and two phase models

2013 ◽  
Vol 19 (1) ◽  
pp. 13-24 ◽  
Author(s):  
Ahmad Shamiria ◽  
M.A. Hussaina ◽  
Farouq Mjallic ◽  
Navid Mostoufid
Keyword(s):  
Molecular Weight ◽  
Gas Phase ◽  
Production Rate ◽  
Fluidized Bed ◽  
Average Molecular Weight ◽  
Phase Model ◽  
Propylene Polymerization ◽  
Flow Index ◽  
Fluidized Bed Reactors ◽  
Two Phase

A comparative study describing gas-phase propylene polymerization in fluidized-bed reactors using Ziegler-Natta catalyst is presented. The reactor behavior was explained using a two-phase model (which is based on principles of fluidization) as well as simulation using the Aspen Polymers process simulator. The two-phase reactor model accounts for the emulsion and bubble phases which contain different portions of catalysts with the polymerization occurring in both phases. Both models predict production rate, molecular weight, polydispersity index (PDI) and melt flow index (MFI) of the polymer. We used both models to investigate the effect of important polymerization parameters, namely catalyst feed rate and hydrogen concentration, on the product polypropylene properties, such as production rate, molecular weight, PDI and MFI. Both the two-phase model and Aspen Polymers simulator showed good agreement in terms of production rate. However, the models differed in their predictions for weight-average molecular weight, PDI and MFI. Based on these results, we propose incorporating the missing hydrodynamic effects into Aspen Polymers to provide a more realistic understanding of the phenomena encountered in fluidized bed reactors for polyolefin production.

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