Flow Regime Study of a Light Material in an Industrial Scale Cold Flow Circulating Fluidized Bed

2006 ◽  
Vol 128 (2) ◽  
pp. 129-134 ◽  
Author(s):  
Joseph S. Mei ◽  
Esmail R. Monazam ◽  
Lawrence J. Shadle
Keyword(s):  
Experimental Data ◽  
Mathematical Models ◽  
Flow Regime ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Density Ratio ◽  
Gas Velocity ◽  
Dense Phase ◽  
Empirical Correlations ◽  
Light Material

A series of experiments was conducted in the 0.3meter diameter circulating fluidized bed test facility at the National Energy Technology Laboratory (NETL) of the U. S. Department of Energy. The particle used in this study was a coarse, light material, cork, which has a particle density of 189kg∕m3 and a mean diameter of 812μm. Fluidizing this material in ambient air approximates the same gas-solids density ratio as coal and coal char in a pressurized gasifier. The purpose of this study is twofold. First, this study is to provide a better understanding on the fundamentals of flow regimes and their transitions. The second purpose of this study is to generate reliable data to validate the mathematical models, which are currently under development at NETL. Utilization of such coarse, light material can greatly facilitate the computation of these mathematical models. Furthermore, the ratio of density of cork to air under ambient conditions is similar to the density ratio of coal to gas at the gasification and pressurized fluidized bed combustion environment. This paper presents and discusses the data, which covered operating flow regime from dilute phase, fast fluidization, and to dense phase transport by varying the solid flux, Gs at a constant gas velocity, Ug. Data are presented by mapping the flow regime for coarse cork particles in a ΔP∕ΔL‐Gs‐Ug plot. The coarse cork particles exhibited different behavior than the published literature measurements on heavier materials such as alumina, sand, FCC, silica gel, etc. A stable operation can be obtained at a fixed riser gas velocity higher than the transport velocity, e.g., at Ug=3.2m∕s, even though the riser is operated within the fast fluidization flow regime. Depending upon the solids influx, the riser can also be operated at dilute phase or dense phase flow regimes. Experimental data were compared to empirical correlations in published literature for flow regime boundaries as well as solids fractions in the upper dilute and the lower dense regions for fast fluidization flow regime. Comparisons of measured data with these empirical correlations show rather poor agreements. These discrepancies, however, are not surprising since the correlations for these transitions were derived from experimental data of comparative heavier materials such as sands, FCC, iron ore, alumina, etc.

The Mapping of Flow Regimes for a Light Material: Cork

2003 ◽  
Author(s):  
Joseph S. Mei ◽  
Esmail R. Monazam ◽  
Lawerence J. Shadle
Keyword(s):  
Mathematical Models ◽  
Flow Regime ◽  
Fluidized Bed ◽  
Density Ratio ◽  
Flow Regimes ◽  
Ambient Air ◽  
Gas Velocity ◽  
Dense Phase ◽  
Empirical Correlations ◽  
Light Material

A series of experiments was conducted in the 0.3-meter diameter circulating fluidized bed test facility at the U.S. Department of Energy’s National Energy Technology Laboratory (NETL). Cork, the bed material used in this study, is a coarse, light material, with a particle density of 189 kg/m3 and a mean diameter of 1007 μm. Fluidizing this material in ambient air provides approximately the same gas to solids density ratio as coal and coal char in a pressurized gasifier. Furthermore, the density ratio of cork to air under ambient conditions is similar to the density ratio of coal to gas at the gasification and pressurized fluidized bed combustion environment. The purpose of this study is to generate reliable data to validate the mathematical models currently under development at NETL. Using such coarse, light material can greatly facilitate the computation of these mathematical models. This paper presents and discusses data for the operating flow regimes of dilute-phase, fast-fluidization, and dense-phase transport by varying the solid flux (Gs) at a constant gas velocity (Ug). Data are presented by mapping the flow regime for coarse cork particles in a ΔP/ ΔL-Gs-Ug plot. The coarse cork particles exhibited different behavior than the measurements on heavier materials found in published literature, such as alumina, sand, FCC, and silica gel. Stable operation can be obtained at a fixed riser gas velocity that is higher than the transport velocity (e.g. at Ug = 3.2 m/sec), even though the riser is operating within the fast fluidization flow regime. Depending upon the solid influx, the riser can also be operated at dilute-phase or dense-phase flow regimes. Experimental data were compared to empirical correlations in published literature for flow regime boundaries, and solid fractions in the upper-dilute and the lower-dense regions of a fast fluidization flow regime. Comparisons of measured data show rather poor agreement with these empirical correlations. Xu et al. (2000) have observed this lack of agreement in their study of the effect of bed diameter on the saturation carrying capacity. The basis of empirical correlations depends on bed diameter and particle type, and are generally not well understood.

An Experiment on Solid Circulation Characteristics of a Dual Circulating fluidized Bed Based on Biomaterial Properties and Mechanics Properties

2012 ◽  
Vol 600 ◽  
pp. 261-264
Author(s):  
Teng Ge Mi ◽  
Ying Zhao ◽  
Chang Qing Dong ◽  
Wei Liang Cheng
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Circulation Rate ◽  
Gas Velocity ◽  
Solid Circulation Rate ◽  
Dual Fluidized Bed ◽  
Bed Material ◽  
Circulation Characteristics

In this paper, a dual fluidized bed has been established. The effect of bed material build-up height and gas velocity on the solid circulation rate of CFB (circulating fluidized bed) and BFB (bubble fluidized bed) has been studied. The results show that the solid circulation rate is increased with the increasing of gas velocity Uc and the bed material build-up height. Bed material build-up height of BFB and CFB is changed with the changing of gas velocity Uc. The bed material heights of CFB and BFB have been also investigated in this experiment.

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.

A MODEL FOR A DENSE PHASE CIRCULATING FLUIDIZED BED

1997 ◽  
Vol 161 (1) ◽  
pp. 103-124
Author(s):  
YINGHE HE ◽  
VICTOR RUDOLPH
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Dense Phase

The Effect of Coal Type on Thermal Balance in a Dense Phase of a Circulating Fluidized Bed Combustor

2003 ◽  
Author(s):  
Mirko S. Komatina ◽  
Xin Liu ◽  
Franz Winter
Keyword(s):  
Fluidized Bed ◽  
Coal Batch ◽  
Circulating Fluidized Bed ◽  
Temperature Drop ◽  
Thermal Balance ◽  
Experimental Investigations ◽  
Volatile Content ◽  
Dense Phase ◽  
Fluidized Bed Combustor ◽  
Coal Type

The results of experimental investigations of the effect of coal type on the thermal balance during early stages in a dense phase of a circulating fluidized bed combustor (CFBC) are presented in this paper. The experimental investigations were performed in a laboratory-scale CFBC. Five coals with three size classes (small 0.5–0.63 mm, medium 2–3.1 mm, and large 7.1–8 mm) were tested. The electrical heating system was used to ensure that the riser has a constant temperature (850°C) before the experiments. Mean velocity was 1.2 m/s. Oxygen concentration was 5%. During the experiments the temperature in the dense phase in the lower part of the riser and the gas concentrations of CO and CO2 were measured continuously. On the temperature histories measured, it can be seen that after feeding the coal batch into the hot CFBC, the temperature in the dense phase decreases, after reaching a minimum value and increases back again. The experimental results were compared to each other on the basis of the maximum temperature drop after feeding the coal batch. It was concluded that the temperature drop depends slightly on coal size and mainly on coal type and its mechanical and physical structure. The temperature drop slightly increases when the particle size of the coal batch increases. The strongest influence on the temperature drop in the dense phase of the CFBC shows the volatile content of the original coal and the temperature drop is directly proportional to the volatile content.

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