Effects of operating conditions on longitudinal solids mixing in a circulating fluidized bed riser

AIChE Journal ◽  
1991 ◽  
Vol 37 (10) ◽  
pp. 1450-1458 ◽  
Author(s):  
M. J. Rhodes ◽  
S. Zhou ◽  
T. Hirama ◽  
H. Cheng
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Operating Conditions ◽  
Solids Mixing

Solids mixing in the bottom zone of a circulating fluidized bed

2001 ◽  
Vol 120 (1-2) ◽  
pp. 21-33 ◽  
Author(s):  
Philipp Schlichthaerle ◽  
Joachim Werther
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Bottom Zone ◽  
Solids Mixing

Solids mixing in a circulating fluidized bed

2006 ◽  
Vol 49 (21-22) ◽  
pp. 4183-4193 ◽  
Author(s):  
Yu.S. Teplitskii ◽  
V.I. Kovenskii ◽  
E.F. Nogotov ◽  
V.A. Borodulya
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Solids Mixing

Dynamic simulation of the circulating fluidized bed loop performance under the various operating conditions

2019 ◽  
Vol 233 (7) ◽  
pp. 901-913 ◽  
Author(s):  
Seongil Kim ◽  
Sangmin Choi ◽  
Jari Lappalainen ◽  
Tae-Ho Song
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Heat Transfer Rate ◽  
Dynamic Simulation ◽  
Transfer Rate ◽  
Gas Flow ◽  
Circulating Fluidized Bed ◽  
Operating Conditions ◽  
Temperature Behavior ◽  
Furnace Temperature

In a circulating fluidized bed boiler, the large thermal mass and flow characteristics of the solids strongly affect the transient response of the circulating fluidized bed loop temperature, which determines the heat transfer rate to steam flow. Therefore, it is essential to interpret the dynamic response of the solid behavior in the circulating fluidized bed loop for the stable and efficient operation of the circulating fluidized bed boiler. In this study, the dynamic simulation of the solid behavior along with the flue gas flow in a circulating fluidized bed loop was performed by applying the core-annulus approach for the solid-gas flow inside the furnace and selected models for other physical phenomena of the fluidized bed. The circulating fluidized bed loop of a commercial boiler was selected as the target system. Especially, the model simulates the characteristics of the solid behavior, such as the local solid mass distribution, and the solid flow inside the furnace and the circulating solid according to the various operating conditions. These aspects are difficult to measure and quantify in a real power plant. In this paper, the simulated furnace temperature behavior as the representative performance parameter of the circulating fluidized bed loop was discussed along with the qualitative operation experiences reported in the literature. The operating conditions include the feed rate of fuel and air, the particle size, the solid inventory and the solid circulation rate. Furnace temperature behavior was reproduced through the simulation for each operating case in the literature and was analyzed with the solid behavior along with the combustion rate and heat transfer rate of the circulating fluidized bed loop. The simulation enables quantitative evaluation of the effect of the solid behavior on the temperatures of the furnace and return part in the various operating conditions.

scholarly journals Systematic Study of Pressure Fluctuation in the Riser of a Dual Inter-Connected Circulating Fluidized Bed: Using Single and Binary Particle Species

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 890 ◽  
Author(s):  
Yusif A. Alghamdi ◽  
Zhengbiao Peng ◽  
Caimao Luo ◽  
Zeyad Almutairi ◽  
Behdad Moghtaderi ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Circulating Fluidized Bed ◽  
Pressure Fluctuations ◽  
Single Species ◽  
Terminal Velocity ◽  
Operating Conditions ◽  
Cold Flow ◽  
Fluidization Regime ◽  
Spectrum Density

This study systematically investigates the pressure fluctuation in the riser of a dual interconnected circulating fluidized bed (CFB) representing a 10 kWth cold-flow model (CFM) of a chemical-looping combustion (CLC) system. Specifically, a single-species system (SSS) and a binary-mixtures system (BMS) of particles with different sizes and densities were utilized. The pressure fluctuation was analyzed using the fast Fourier transform (FFT) method. The effect of introducing a second particle, changing the inventory, composition (i.e., 5, 10 to 20 wt.%), particle size ratio, and fluidization velocity were investigated. For typical SSS experiments, the results were similar to those scarcely reported in the literature, where the pressure fluctuation intensity was influenced by varying the initial operating conditions. The pressure fluctuations of BMS were investigated in detail and compared with those obtained from SSS experiments. BMS exhibited different behaviour; it had intense pressure fluctuation in the air reactor and in the riser when compared to SSS experiments. The standard deviation (SD) of the pressure fluctuation was found to be influenced by the fluidization regime and initial operating conditions, while the power spectrum density (PSD) values were more sensitive to the presence of the particles with the higher terminal velocity in the binary mixture.

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.

Attrition Behavior of Coal Ash Under Circulating Fluidized Bed Combustion Conditions

2003 ◽  
Author(s):  
Franz Winter ◽  
Xin Liu
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Coal Ash ◽  
Operating Conditions ◽  
Laboratory Scale ◽  
Silica Sand ◽  
Electrical Heating ◽  
Fluidized Bed Combustion ◽  
Bed Temperature ◽  
Wide Range

The attrition behavior of ash produced from two bituminous and one anthracite coal was studied under laboratory-scale circulating fluidized bed combustor (CFBC) conditions. After the ash was produced in the oven, the ash sample with a size range from 0.1 to 1 mm was fed into the hot CFBC, which was heated by electrical heating shells and fluidized by air. The laboratory-scale CFBC was operated with using fine silica sand (40 to 80 μm) as bed material. After a certain time the operation was stopped, all particles were collected and sieving analysis was performed to obtain the actual particle size distribution (PSD) of the coal ash. The operating conditions were changed in a wide range, i.e. the bed temperature from 600 to 850°C, the fluidizing velocity from 1.2 to 2 m/s, the residence time from 60 to 120 min and the design of the cyclone. The effects of operating conditions and coal type were studied and their relative importance is discussed. Elemental analysis of the coal ashes showed that Si and Ca may play an important role during attrition.

Axial gas and solids mixing in a down flow circulating fluidized bed reactor based on CFD simulation

2012 ◽  
Vol 73 ◽  
pp. 8-19 ◽  
Author(s):  
Parinya Khongprom ◽  
Archwit Aimdilokwong ◽  
Sunun Limtrakul ◽  
Terdthai Vatanatham ◽  
Palghat A. Ramachandran
Keyword(s):  
Fluidized Bed ◽  
Cfd Simulation ◽  
Circulating Fluidized Bed ◽  
Fluidized Bed Reactor ◽  
Solids Mixing
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