Particle Residence Time and Particle Mixing in a Scaled Internal Circulating Fluidized Bed

2002 ◽  
Vol 41 (11) ◽  
pp. 2637-2645 ◽  
Author(s):  
Ralf Kehlenbeck ◽  
John G. Yates ◽  
Renzo Di Felice ◽  
Hermann Hofbauer ◽  
Reinhard Rauch
Keyword(s):  
Fluidized Bed ◽  
Residence Time ◽  
Circulating Fluidized Bed ◽  
Particle Residence Time ◽  
Particle Mixing

scholarly journals Investigation of Hydrodynamic Behavior of Alginate Aerogel Particles in a Laboratory Scale Wurster Fluidized Bed

Molecules ◽  
2019 ◽  
Vol 24 (16) ◽  
pp. 2915
Author(s):  
Işık Sena Akgün ◽  
Can Erkey
Keyword(s):  
Fluidized Bed ◽  
Residence Time ◽  
Laboratory Scale ◽  
Tube Length ◽  
Operating Parameters ◽  
Hydrodynamic Behavior ◽  
Particle Residence Time ◽  
Upper Limit ◽  
Gap Height ◽  
Circulatory Motion

The effects of design and operating parameters on the superficial velocity at the onset of circulatory motion and the residence time of alginate aerogel particles in a laboratory scale Wurster fluidized bed were investigated. Several sets of experiments were conducted by varying Wurster tube diameter, Wurster tube length, batch volume and partition gap height. The superficial velocities for Wurster tube with 10 cm diameter were lower than the tube with 8 cm diameter. Superficial velocities increased with increasing batch volume and partition gap height. Moreover, increasing batch volume and partition gap height led to a decrease in the particle residence time in the Wurster tube. The results showed that there is an upper limit for each parameter in order to obtain a circulatory motion of the particles. It was found that the partition gap height should be 2 cm for proper particle circulation. Maximum batch volume for the tube with 10 cm diameter was found as 500 mL whereas maximum batch volume was 250 mL for the tube with 8 cm diameter. The fluidization behavior of the aerogel particles investigated in this study could be described by the general fluidization diagrams in the literature.

Influence of the Gas and Particle Residence Time on Fast Pyrolysis of Lignite

2006 ◽  
Vol 129 (2) ◽  
pp. 152-158 ◽  
Author(s):  
Lijie Cui ◽  
Wenli Song ◽  
Jiayuan Zhang ◽  
Jianzhong Yao ◽  
Weigang Lin
Keyword(s):  
Residence Time ◽  
Circulating Fluidized Bed ◽  
Product Distribution ◽  
Liquid Fuels ◽  
High Yield ◽  
Flash Pyrolysis ◽  
Particle Residence Time ◽  
Coal Particles ◽  
Liquid Products ◽  
Secondary Reactions

Coal resource is abundant in China, while the reserves of natural gas and petroleum are limited. Due to the rapid increase in the number of automobiles, a competitive way to produce liquid fuels from coal is urgently needed in China. A so-called “coal topping process” is under development at the Institute of Process Engineering, Chinese Academy of Sciences, from which liquid products can be obtained by flash pyrolysis in an integrated circulating fluidized bed system. In order to achieve a high yield of liquid products from high volatile coal, controlling the residence time of coal particles and produced gas may be of importance for minimizing the degree of the secondary reactions; i.e., polymerization and cracking of the liquid products. Experiments of the flash pyrolysis of coal have been conducted in an entrained bed reactor, which is especially designed to study the influence of the coal particle residence time on the product distribution. The results show that the gaseous, liquid, and solid product distribution, the gas compositions as well as the liquid compositions depend strongly on the gas and particle residence time.

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.

Sign in / Sign up

Export Citation Format

Share Document