scholarly journals Computational Analysis of the Hydrodynamic Behavior for Different Air Distributor Designs of Fluidized Bed Gasifier

2021 ◽  
Vol 9 ◽  
Author(s):  
Naveed Raza ◽  
Muhammad Ahsan ◽  
Muhammad Taqi Mehran ◽  
Salman Raza Naqvi ◽  
Iftikhar Ahmad
Keyword(s):  
Pressure Drop ◽  
Fluidized Bed ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Perforated Plate ◽  
Column Height ◽  
Thermochemical Conversion ◽  
Open Area ◽  
Slotted Plate ◽  
Distributor Plate

Fluidized bed gasification has proven to be an appropriate technique for converting various biomass feedstocks into helpful energy. Air distributor plate design is one of the critical factors affecting the thermochemical conversion performance of fluidized bed gasifiers. The present study is proposed to investigate the mixing pattern and pressure drop across different configurations of air distributors using a two-fluid model (TFM) of finite volume method-based solver ANSYS FLUENT. The pressure drop across the bed and mixing pattern have been investigated through qualitative and quantitative analysis of CFD results using three diverse distributor plate designs: perforated plate, 90° slotted plate, and 45° swirling slotted plate. The pressure drop by employing the perforated distributor plate reveals the highest pressure drop due to the smallest open area ratio. However, the pressure drop in the case of 90° slotted plate is found to be 7% and 4% lesser than perforated and 45° slotted plate respectively due to a smaller velocity head developed through the wider open area of the straight slotted plates. The distributor design configuration having a 45° slotted plate exhibits considerable pressure drop compared to the 90° slotted plate due to the longer path length of the slot. Numerical pressure drop results across the bed with different types of distributor plates prove reasonable agreement with the experimental results available in the literature. Mixing behavior in perforated distributor plates exhibits lower portion solid volume fraction of around 0.58. However, it falls rapidly as go up the riser (7.7% of column height); 90° slotted plate shows bottom region solid volume fraction of around 0.5. In addition, it exhibits an even broader range of sand volume fraction and column height (13.46% of column height). Finally, the 45° distributor plate reveals the highest range of volume fraction through the riser height (17.3% of column height), indicating the better mixing characteristics of the fluidized zone.

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.

Genetic Programming based Drag Model with Improved Prediction Accuracy for Fluidization Systems

2017 ◽  
Vol 15 (2) ◽  
Author(s):  
R. R. Sonolikar ◽  
M. P. Patil ◽  
R. B. Mankar ◽  
S. S. Tambe ◽  
B. D. Kulkarni
Keyword(s):  
Pressure Drop ◽  
Genetic Programming ◽  
Drag Coefficient ◽  
Prediction Accuracy ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Superior Performance ◽  
Momentum Exchange ◽  
Drag Model ◽  
Parameter Ranges

Abstract The drag coefficient plays a vital role in the modeling of gas-solid flows. Its knowledge is essential for understanding the momentum exchange between the gas and solid phases of a fluidization system, and correctly predicting the related hydrodynamics. There exists a number of models for predicting the magnitude of the drag coefficient. However, their major limitation is that they predict widely differing drag coefficient values over same parameter ranges. The parameter ranges over which models possess a good drag prediction accuracy are also not specified explicitly. Accordingly, the present investigation employs Geldart’s group B particles fluidization data from various studies covering wide ranges of Re and εs to propose a new unified drag coefficient model. A novel artificial intelligence based formalism namely genetic programming (GP) has been used to obtain this model. It is developed using the pressure drop approach, and its performance has been assessed rigorously for predicting the bed height, pressure drop, and solid volume fraction at different magnitudes of Reynolds number, by simulating a 3D bubbling fluidized bed. The new drag model has been found to possess better prediction accuracy and applicability over a much wider range of Re and εs than a number of existing models. Owing to the superior performance of the new drag model, it has a potential to gainfully replace the existing drag models in predicting the hydrodynamic behavior of fluidized beds.

scholarly journals Computational and Experimental Study on Pressure Drop in a Fluidised Bed with Different Air Distributor Designs

2020 ◽  
Vol 17 (2) ◽  
pp. 8043-8051
Author(s):  
A. S. M. Yudin ◽  
A. N. Oumer ◽  
N. F. M. Roslan ◽  
M. A. Zulkarnain
Keyword(s):  
Pressure Drop ◽  
Perforated Plate ◽  
Area Ratio ◽  
Maximum Pressure ◽  
Fluidised Bed ◽  
Key Factor ◽  
Minimum Number ◽  
Maximum Pressure Drop ◽  
Free Area ◽  
Distributor Plate

Fluidised bed combustion (FBC) has been recognised as a suitable technology for converting a wide variety of fuels into energy. In a fluidised bed, the air is passed through a bed of granular solids resting on a distributor plate. Distributor plate plays an essential role as it determines the gas-solid movement and mixing pattern in a fluidised bed. It is believed that the effect of distributor configurations such as variation of free area ratio and air inclination angle through the distributor will affect the operational pressure drop of the fluidised bed. This paper presents an investigation on pressure drop in fluidised bed without the presence of inert materials using different air distributor designs; conventional perforated plate, multi-nozzles, and two newly proposed slotted distributors (45° and 90° inclined slotted distributors). A 3-dimensional Computational Fluid Dynamics (CFD) model is developed and compared with the experimental results. The flow model is based on the incompressible isothermal RNG k-epsilon turbulent model. In the present study, systematic grid-refinement is conducted to make sure that the simulation results are independent of the computational grid size. The non-dimensional wall distance,  is examined as a key factor to verify the grid independence by comparing results obtained at different grid resolutions. The multi-nozzles distributor yields higher distributor pressure drop with the averaged maximum value of 749 Pa followed by perforated, 45° and 90° inclined distributors where the maximum pressure drop recorded to be about one-fourth of the value of the multi-nozzles pressure drop. The maximum pressure drop was associated with the higher kinetic head of the inlet air due to the restricted and minimum number of distributor openings and low free area ratio. The results suggested that low-pressure drop operation in a fluidised bed can be achieved with the increase of open area ratio of the distributor.

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.

On the Computational Modeling of Unfluidized and Fluidized Bed Dynamics

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Lindsey C. Teaters ◽  
Francine Battaglia
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Multiphase Flow ◽  
Fluidized Bed ◽  
Void Fraction ◽  
Volume Fraction ◽  
Flow Modeling ◽  
Ansys Fluent ◽  
Minimum Fluidization Velocity ◽  
Two Factors

Two factors of great importance when considering gas–solid fluidized bed dynamics are pressure drop and void fraction, which is the volume fraction of the gas phase. It is, of course, possible to obtain pressure drop and void fraction data through experiments, but this tends to be costly and time consuming. It is much preferable to be able to efficiently computationally model fluidized bed dynamics. In the present work, ANSYS Fluent® is used to simulate fluidized bed dynamics using an Eulerian–Eulerian multiphase flow model. By comparing the simulations using Fluent to experimental data as well as to data from other fluidized bed codes such as Multiphase Flow with Interphase eXchanges (MFIX), it is possible to show the strengths and limitations with respect to multiphase flow modeling. The simulations described herein will present modeling beds in the unfluidized regime, where the inlet gas velocity is less than the minimum fluidization velocity, and will deem to shed some light on the discrepancies between experimental data and simulations. In addition, this paper will also include comparisons between experiments and simulations in the fluidized regime using void fraction.

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