Characteristics of Axial and Radial Development of Solids Holdup in a Countercurrent Fluidized Bed Particle Solar Receiver

2021 ◽  
Author(s):  
Kaijun Jiang ◽  
Fengli Wang ◽  
Yanqiang Kong ◽  
Chao Xu ◽  
Xiaoze Du
Keyword(s):  
Fluidized Bed ◽  
Solids Holdup ◽  
Solar Receiver

Solids Holdup of High Flux Circulating Fluidized Bed at Elevated Pressure

2012 ◽  
Vol 35 (5) ◽  
pp. 904-910 ◽  
Author(s):  
S. Yin ◽  
B. Jin ◽  
W. Zhong ◽  
Y. Lu ◽  
Y. Zhang ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Elevated Pressure ◽  
High Flux ◽  
Solids Holdup

Measurement of solids holdup in a three-phase fluidized bed by an ultrasonic technique

1989 ◽  
Vol 44 (1) ◽  
pp. 196-198 ◽  
Author(s):  
S. Okamura ◽  
S. Uchida ◽  
T. Katsumata ◽  
K. Iida
Keyword(s):  
Fluidized Bed ◽  
Ultrasonic Technique ◽  
Solids Holdup ◽  
Three Phase

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.

scholarly journals 3D CPFD Simulation of Circulating Fluidized Bed Downer and Riser: Comparisons of Flow Structure and Solids Back-Mixing Behavior

Processes ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 161
Author(s):  
Yancong Liu ◽  
Yingya Wu ◽  
Xiaogang Shi ◽  
Chengxiu Wang ◽  
Jinsen Gao ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Residence Time ◽  
Circulating Fluidized Bed ◽  
Operating Conditions ◽  
Solids Holdup ◽  
The Difference ◽  
Large Clusters ◽  
Small Clusters ◽  
Cluster Behavior ◽  
Back Mixing

The difference of gas-solids flow between a circulating fluidized bed (CFB) downer and riser was compared by computational particle fluid dynamics (CPFD) approach. The comparison was conducted under the same operating conditions. Simulation results demonstrated that the downer showed much more uniform solids holdup and solids velocity distribution compared with the riser. The radial non-uniformity index of the solids holdup in the riser was over 10 times than that in the downer. In addition, small clusters tended to be present in the whole downer, large clusters tended to be present near the wall in riser. It was found that the different cluster behavior is important in determining the different flow behaviors of solids in the downer and riser. While the particle residence time increased evenly along the downward direction in the downer, particles with both shorter and longer residence time were predicted in the whole riser. The nearly vertical cumulative residence time distribution (RTD) curve in the downer further demonstrated that the solids back-mixing in the downer is limited while that in the riser is severe. Solids turbulence in the downer was much weaker compared with the riser, while the large clusters formation near the wall in the riser would hinder solids transportation ability.

Numerical investigation of the isothermal flow field and particle deposition behaviour in a rotating fluidized bed solar receiver

Solar Energy ◽  
2019 ◽  
Vol 182 ◽  
pp. 348-360 ◽  
Author(s):  
Zhao Lu ◽  
Alfonso Chinnici ◽  
Mehdi Jafarian ◽  
Maziar Arjomandi ◽  
Graham J. Nathan
Keyword(s):  
Flow Field ◽  
Numerical Investigation ◽  
Fluidized Bed ◽  
Particle Deposition ◽  
Isothermal Flow ◽  
Solar Receiver

A 50 kW Fluidized Bed High Temperature Solar Receiver: Heat Transfer Analysis

1988 ◽  
Vol 110 (4) ◽  
pp. 313-320 ◽  
Author(s):  
G. Flamant ◽  
D. Gauthier ◽  
C. Boudhari ◽  
Y. Flitris
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Large Diameter ◽  
Pilot Scale ◽  
Heat Transfer Analysis ◽  
Transfer Model ◽  
Front Wall ◽  
Measured Efficiency ◽  
The Mean ◽  
Solar Receiver

A theoretical and experimental investigation of a pilot scale solar fluidized bed receiver is presented. Large diameter alumina particles were used. Experimental data with the bed in the temperature range of 550° C to 915° C (wall 740° C–1035° C) are compared with a simple model based on one parameter: the mean front wall temperature. At 950° C, the predicted efficiency is 73 percent and the measured efficiency is about 65 percent. In addition, unsteady behavior of the receiver is described by a simple heat transfer model.

Single-Phase Flow Analysis: An Attempt to Mitigate Particle Deposition on the Glass Window of a Fluidized Bed Solar Receiver

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
M. Shahabuddin
Keyword(s):  
Numerical Analysis ◽  
Turbulent Flow ◽  
Fluidized Bed ◽  
Mass Flow ◽  
Particle Deposition ◽  
Flow Analysis ◽  
Radiation Transmission ◽  
Flow Phenomena ◽  
Solar Receiver ◽  
Made In

The problem of particle deposition on the glass window of a solar receiver has restricted its continuous operation by reducing solar radiation transmission. A rigorous attempt has been made in this analysis by exploring the understanding of particle deposition mechanisms and their mitigating strategies. A simplified form of a fluidized bed solar receiver (FBSR) having the same flow phenomena of FBSR is chosen for the numerical analysis. In the numerical analysis, the turbulent flow in the receiver is investigated by renormalized group (RNG) theory based k–ε models. The validation of the numerical model is carried out by measuring the turbulent flow properties using a turbulent flow instrumentation (TFI) Cobra probe. The results of this analysis revealed that mass flow into the secondary concentrator of the receiver was reduced significantly when the ratio between the outlets and inlet areas was 0.5, and the ratio between the aperture and receiver diameter was 0.41. When using window shielding jets, only 5% of the inlet mass as a window jet was sufficient to prevent any particle deposition on the glass window, however, the number of jets was found to be an important factor. At a constant mass flow rate, increasing the number of window shielding jets reduced the suction pressure from the core to the aperture, which helped to restrict the inlet flow in the secondary concentrator.

Different Exit Effects between a Combined Riser with Variable Exit Constraints and a Conventional Riser with Weak Exit Constraints

2012 ◽  
Vol 550-553 ◽  
pp. 529-533
Author(s):  
De Wu Wang ◽  
Meng Da Jia ◽  
Shao Feng Zhang ◽  
Chun Xi Lu
Keyword(s):  
Fluidized Bed ◽  
Particle Velocity ◽  
Large Scale ◽  
Operating Conditions ◽  
Wall Region ◽  
Cold Model ◽  
Linear Distribution ◽  
Cross Sectional ◽  
Bed Height ◽  
Solids Holdup

A large-scale cold model experimental setup of combined riser with variable constraint exit (CRVCE) was established. The axial and radial distributions of solids holdup and particle velocity, under different operating conditions, were investigated experimentally, and the results were compared with conventional riser (CR). Experimental results showed that, the exit restrictive effect of combined riser with variable constraint exit was weak when particle circulation flux and static bed height in upper fluidized bed were lower, while it turned to be strong when superficial gas velocity and static bed height in upper fluidized bed were higher. Under the same conditions, averaged cross-sectional solids holdup of CRVCE was characterized by C type distribution when article circulation flux was higher, while that of CR with weak constraint exit was characterized by linear distribution. In axial direction, averaged cross-sectional particle velocity of CRVCE changed in order: acceleration-constant-decrease velocity, while that of CR changed in another: acceleration-constant velocity. The maximum of local solids holdup value of CRVCE appeared at the dimensionless radius position r/R=0.7, while that of CR appeared in the wall region. Their local particle velocities were similar in the core region, while local particle velocity of CRVCE was lower than that of CR in the annular region.

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