Prediction of Solid Recirculation Rate and Solid Volume Fraction in an Internally Circulating Fluidized Bed

2015 ◽  
Vol 12 (04) ◽  
pp. 1540005 ◽  
Author(s):  
Ravi Gujjula ◽  
Narasimha Mangadoddy
Keyword(s):  
Experimental Data ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Volume Fraction ◽  
Draft Tube ◽  
Numerical Study ◽  
Solid Particles ◽  
Granular Temperature ◽  
Solids Concentration ◽  
Drag Laws

This paper presents a numerical study of gas and solid flow in an internally circulating fluidized bed (ICFB). Two-fluid Eulerian model with kinetic theory of granular flow option for solid phase stress closure and various drag laws were used to predict the hydrodynamic behavior of ICFB. 2D and 3D geometries were used to run the simulations. The 2D simulation results by various drag laws show that the Arastoopour and Gibilaro drag models able to predict the fluidization dynamics in terms of flow patterns, void fractions and axial velocity fields close to the experimental data. The effect of superficial gas velocity, presence of draft tube on solid hold-up distribution, solid circulation pattern, and variations in gas bypassing fraction for the 3D ICFB are investigated. The mechanism governing the solid circulation and solids concentration in an ICFB has been explained based on gas and solid dynamics obtained from the simulations. Predicted total granular temperature distributions in the draft tube and annular zones qualitatively agree with experimental data. The total granular temperature tends to increase with increasing solids concentration in the dilute region (ε < 0.1) and decreases with an increase of solids concentration in the dense region (ε > 0.1). In the dense zone, the decreasing trend in the granular temperature is mainly due to the reduction of the mean free path of the solid particles.

Effect of Various Parameters on the Solids Holdup in a Liquid-Solid Circulating Fluidized Bed

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Natarajan Palani ◽  
Velraj Ramalingam ◽  
Seeniraj R.V.
Keyword(s):  
Experimental Data ◽  
Fluidized Bed ◽  
Flow Rate ◽  
Liquid Flow ◽  
Circulating Fluidized Bed ◽  
Liquid Flow Rate ◽  
Tap Water ◽  
Solid Particles ◽  
Circulation Rate ◽  
Solids Holdup

A liquid-solid circulating fluidized bed (LSCFB) is operated at high liquid velocity, where particle entrainment is highly significant and between the conventional liquid fluidized bed and the dilute phase liquid transport regimes. In the present work, systematic experiments were carried out in a 0.094 m ID and 2.4 m height laboratory-scale liquid-solid circulating fluidized bed apparatus by using various solid particles and tap water as a fluidizing medium to study the hydrodynamics (axial solids holdup and solids circulation rate). The effects of operating parameters, i.e., primary liquid flow rate in the riser (jf), auxiliary liquid flow rate (ja), total liquid flow rate (jl), particle density (?s), particle diameter (dp) and solids feed pipe diameter (do) on the axial solids holdup distribution were analyzed from the experimental data. Finally, a correlation was developed from the experimental data to estimate average solid holdup in the riser, and it was compared with present experimental and available data in the literature. They agree well with a maximum root-mean-square deviation of 9.12 %.

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

Applications of Feed-Forward Neural Network to Study Irregular-Shape Particle Effects on Hydrodynamics Behavior in a Liquid–Solid Circulating Fluidized Bed Riser

2013 ◽  
Vol 11 (1) ◽  
pp. 443-452 ◽  
Author(s):  
Shaikh Abdur Razzak
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Phase Distribution ◽  
Flow Behavior ◽  
Pilot Scale ◽  
Irregular Shape ◽  
Feed Forward Neural Network ◽  
Feed Forward

Abstract Feed-forward neural network (FFNN) modeling techniques are applied to study the flow behavior of different-size irregular-shape particles in a pilot scale liquid–solid circulating fluidized bed (LSCFB) riser. The adequacy of the developed model is examined by comparing the model predictions with experimental data obtained from the LSCFB using lava rocks (dmean 500 and 920 µm) and water as solids and liquid phases, respectively. Axial and radial solid holdup profiles are measured in the riser at four axial locations (H 1, 2, 3 and 3.8 m above the distributor) above the liquid distributor for different operating liquids. In the model training, the effects of various auxiliary and primary liquid velocities, superficial liquid velocities and superficial solid velocities on radial phase distribution at different axial positions are considered. For model validation along with other experimental parameters, dimensionless normalized superficial liquid velocities and net superficial liquid velocities are also introduced. The correlation coefficient values of the predicted output and the experimental data are found to be 0.95 and 0.94 for LR-500 and LR-920 particles, respectively which reflects the competency of the developed FFNN model.

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