97/00561 Similarity of radial profiles of solid volume fraction in a circulating fluidized bed

1997 ◽  
Vol 38 (1) ◽  
pp. 43 ◽  
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Radial Profiles

Three-Dimensional Simulation of Gas-Solid Flow in the Biomass Circulating Fluidized Bed Gasifier’s Riser

2011 ◽  
Vol 383-390 ◽  
pp. 6537-6542
Author(s):  
Wen Yi Chen ◽  
Xin Liu ◽  
Xiao Xu Fan ◽  
Lei Zhe Chu ◽  
Yi Mei Yang ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Volume Fraction ◽  
Mutual Influence ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Momentum Exchange ◽  
Solid Flow ◽  
Radial Profiles

Using the Gidaspow model as the momentum exchange coefficient to take a full-loop simulation of miniature circulating fluidized bed gasifier (CFBG) in the lab, and taking mutual influence of different parts in consideration, it focus on the gas-solid flow structure in the riser in this paper. The heterogeneous behavior in the CFBG riser and the radial profiles of solid volume fraction under different solid inventories in simulation are showed in this paper as a replenishment of certain data which are hard to measure in experiments. The results showed it can’t form an obvious core-annulus flow because of the riser’s high height-diameter ratio and the big refeed line diameter. There are clusters growing and dissipation in a short time. A turning point of pressure drop may be seem as a separation of dense area and dilute area.The three-dimensional (3D) simulation revealed the solid flux and the pressure drop agree with the experimental data.

Simulation Studies of Gas-Solid in the Riser of a Circulating Fluidized Bed

2005 ◽  
Author(s):  
Ahmad Hussain ◽  
Farid Nasir Ani ◽  
Amer Nordin Darus ◽  
Azeman Mustafa ◽  
Arshad A. Salema
Keyword(s):  
Gas Phase ◽  
Fluidized Bed ◽  
Turbulence Model ◽  
Circulating Fluidized Bed ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Design Parameters ◽  
Cfd Model ◽  
End Effects ◽  
Wide Range

A numerical parametric study was performed on the influence of various riser exit geometries on the hydrodynamics of gas-solid two-phase flow in the riser of a Circulating Fluidized Bed (CFB). A Eulerian continuum formulation was applied to both phases. A two fluid framework has been used to simulate fully developed gas-solid flows in vertical riser. A two dimensional Computational Fluid Dynamics (CFD) model of gas-particle flow in the CFB has been investigated using the code FLUENT. The turbulence was modeled by a k-ε turbulence model in the gas phase. The simulations were done using the geometrical configuration of a CFB test rig at the Universiti Teknologi Malaysia (UTM). The CFB riser column has 265 mm (width), 72 mm (depth) and 2.7 m height. The riser is made up of interchangeable Plexiglas columns. The computational model was used to simulate the riser over a wide range of operating and design parameters. In addition, several numerical experiments were carried out to understand the influence of riser end effects, particle size, gas solid velocity and solid volume fraction on the simulated flow characteristics. The CFD model with a k-ε turbulence model for the gas phase and a fixed particle viscosity in the solids phase showed good mixing behaviour. These results were found to be useful in further development of modeling of gas solid flow in the riser.

Application of Wray-Agarwal turbulence model for numerical simulation of gas-solid flows in CFB risers

2021 ◽  
pp. 1-25
Author(s):  
Yali Shao ◽  
Ramesh K. Agarwal ◽  
Xudong Wang ◽  
Baosheng Jin
Keyword(s):  
Turbulence Model ◽  
Circulating Fluidized Bed ◽  
Volume Fraction ◽  
Solid Phase ◽  
Solid Volume Fraction ◽  
Turbulence Models ◽  
Two Phase ◽  
Efficient Simulation ◽  
Pressure Profiles ◽  
First Time

Abstract In recent decades, increasing attention has been focused on accurate modeling of circulating fluidized bed (CFB) risers to provide valuable guidance to design, optimization and operation of reactors. Turbulence model plays an important role in accurate prediction of complex gas-solid flows. Recently developed Wray-Agarwal (WA) model is a one-equation turbulence model with the advantages of high computational efficiency and competitive accuracy with two-equation models. In this paper for the first time, Eulerian-Eulerian approach coupled with different turbulence models including WA model, standard κ-ε model and shear stress transport (SST) κ-ω model is employed to simulate two-phase flows of gas phase and solid phase in two CFB risers, in order to assess accuracy and efficiency of WA model compared to other well-known two-equation models. Predicted gas-solid flow dynamic characteristics including the gas-solid volume fraction distributions in radial and axial directions, pressure profiles and solid mass flux distributions are compared with data obtained from experiment in detail. The results demonstrate WA model is very promising for accurate and efficient simulation of gas-solid multiphase flows.

Dual fibre optical probe measurements of solids volume fraction in a circulating fluidized bed

2005 ◽  
Vol 151 (1-3) ◽  
pp. 19-26 ◽  
Author(s):  
A. Magnusson ◽  
R. Rundqvist ◽  
A.E. Almstedt ◽  
F. Johnsson
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Volume Fraction ◽  
Optical Probe ◽  
Probe Measurements

scholarly journals Effects of Riser Diameter on Solids Holdup and Particle Velocity Profiles in Circulating Fluidized Bed Riser Systems

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Ronald W. Breault ◽  
Steven L. Rowan ◽  
Justin M. Weber ◽  
Jingsi Yang
Keyword(s):  
Fluidized Bed ◽  
Particle Velocity ◽  
Circulating Fluidized Bed ◽  
Velocity Profiles ◽  
Small Scale ◽  
Sauter Mean Diameter ◽  
Particle Size Range ◽  
Cold Flow ◽  
Solids Holdup ◽  
Radial Profiles

Abstract Tests were performed in a 0.1-m diameter small circulating fluidized bed (SCFB) and 0.3 m diameter cold flow circulating fluidized bed (CFCFB) riser systems located at the National Energy Technology Laboratory (NETL) to study the effects of riser diameter on the riser hydrodynamics. These tests were performed at solids circulation rates of Gs = 20 and 75 kg/m2 s and superficial gas velocities of Ug = 5.8 and 6.5 m/s using high-density polyethylene (HDPE) pellets with a density of 0.863 g/cm3, particle size range of 600–1400 µm (with a Sauter mean diameter of 871 µm, placing them in the Geldart B classification). Comparisons of riser axial pressure and solids fraction profiles, radial particle velocity profiles, and radial profiles of higher statistical moments and select chaos analysis parameters were considered. The results showed that for a given Ug and Gs, the smaller diameter riser exhibited characteristics associated with more dilute solids flow than that observed in the larger diameter riser. Additionally, the larger diameter riser exhibited a downward flow of solids near the wall under all test conditions, whereas the smaller diameter riser data exhibited little or no indications of solids downflow near the wall. These findings suggest that, from an industrial standpoint, a direct scaleup of small-scale tests cannot readily be accomplished as the solids holdup and the solids velocity profiles in small units (those normally tested in the laboratory) are not similar to those of large units and the performance of large units can therefore not be predicted from small-scale tests.

Hydrodynamics of Multiple Jet Systems in a 2D Gas Solid Fluidized Bed

2012 ◽  
Author(s):  
Steven L. Brown ◽  
Brian Y. Lattimer
Keyword(s):  
Fluidized Bed ◽  
Digital Image Analysis ◽  
Particle Image ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Particle Model ◽  
Discrete Particle ◽  
Image Velocimetry ◽  
Discrete Particle Model ◽  
Single Jet

An experimental 2-D fluidized bed was developed to study gas-solid hydrodynamics. The effects of multiple jet systems were examined using Particle Image Velocimetry (PIV) combined with Digital Image Analysis (DIA). Flow regimes were classified through pressure drop spectral analysis. The combination of these non-intrusive techniques allowed for the development of a solid volume fraction correlation. The experimental results show new void fraction regimes of multiple interacting jets. Jet systems combined to promote gas solid mixing and decrease particle dead zones within the bed. It was determined that the validation of multiple jet Discrete Particle Model simulations cannot be exclusively confirmed from single jet studies.

CFD Simulation of Heat Transfer in Fluidized Bed Reactor

2014 ◽  
Vol 493 ◽  
pp. 267-272
Author(s):  
I. Nyoman Suprapta Winaya ◽  
I. Made Agus Putrawan ◽  
I. Nyoman Gede Sujana ◽  
Made Sucipta
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Cfd Simulation ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Navier Stokes ◽  
Velocity Variation ◽  
Navier Stokes Equation ◽  
Program Language ◽  
The Heat Transfer Coefficient

This study aims to predict heat transfer from a heated bed in a gas fluidized bed using Syamlal-OBrien drag coefficient. Discrete particles model with the Navier-Stokes equation and Eulerian multiphase are used to approach heat transfer simulation. Coefficient of heat transfer which is related to Nusselt Number and volume fraction are calculated using Gunn model which was compiled from C++ program language. The effect of fluidization velocity variation on the heat transfer coefficient comes to the fore, indicating the heat transfer and solid volume fraction at the bed height are very dependent. Contour of solid volume fraction and temperature distribution are also presented.

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