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CFD simulation of solids residence time distribution in a CFB riser
Alternative TitleChem. Eng. Sci.
Hua, Leina; Wang, Junwu; Li, Jinghai
2014-09-27
Source PublicationCHEMICAL ENGINEERING SCIENCE
ISSN0009-2509
Volume117Issue:9Pages:264-282
AbstractSolids residence time distribution (RTD) in circulating fluidized bed risers is a critical parameter for evaluating reactor performances, however, it is still very difficult to be predicted via computational fluid dynamics (CFD) simulation due to the complexity of particle clustering phenomenon. This paper tries to establish an effective CFD model to reasonably predict solids RTD of gas solids riser flows by means of properly addressing the paramount role of particle clusters in determining solids RTD. The gas solids hydrodynamic characteristics were solved by Eulerian-Eulerian model, where an energy minimization multi scale (EMMS) drag model was applied to modify the gas solids drag force to account for the influence of particle clusters. The motion of tracer particles was calculated using species transport equation, where the diffusion coefficient of particles, a vital parameter indicating particle diffusion capacity, was investigated thoroughly. The established CFD model was validated against the available experimental data in the literature It was shown that axial profiles of solids volume fraction and radial profiles of solids mass flux can be well predicted with EMMS drag model, but not with homogeneous drag model. The proper prediction of bed hydrodynamics is also very crucial to the success of solids RTD simulation. On the other hand, the effect of the diffusion coefficient of particles, the magnitude of which can span a range from 10(-5) m(2)/s to 10 m(2)/s, is minor when compared with the convective transport mechanism, at least for the specific cases we studied. In addition, the importance of the sampling time resolution and tracer injection time for a RTD curve was addressed. The simulation results showed that a low time resolution often results in the loss of some micro-scale information, i.e. drastically smoothing the fluctuations of the RTD curve, and an inappropriate assessment of the tracer injection time can lead to a significant change of the RTD curve. (C) 2014 Elsevier Ltd. All rights reserved.; Solids residence time distribution (RTD) in circulating fluidized bed risers is a critical parameter for evaluating reactor performances, however, it is still very difficult to be predicted via computational fluid dynamics (CFD) simulation due to the complexity of particle clustering phenomenon. This paper tries to establish an effective CFD model to reasonably predict solids RTD of gas solids riser flows by means of properly addressing the paramount role of particle clusters in determining solids RTD. The gas solids hydrodynamic characteristics were solved by Eulerian-Eulerian model, where an energy minimization multi scale (EMMS) drag model was applied to modify the gas solids drag force to account for the influence of particle clusters. The motion of tracer particles was calculated using species transport equation, where the diffusion coefficient of particles, a vital parameter indicating particle diffusion capacity, was investigated thoroughly. The established CFD model was validated against the available experimental data in the literature It was shown that axial profiles of solids volume fraction and radial profiles of solids mass flux can be well predicted with EMMS drag model, but not with homogeneous drag model. The proper prediction of bed hydrodynamics is also very crucial to the success of solids RTD simulation. On the other hand, the effect of the diffusion coefficient of particles, the magnitude of which can span a range from 10(-5) m(2)/s to 10 m(2)/s, is minor when compared with the convective transport mechanism, at least for the specific cases we studied. In addition, the importance of the sampling time resolution and tracer injection time for a RTD curve was addressed. The simulation results showed that a low time resolution often results in the loss of some micro-scale information, i.e. drastically smoothing the fluctuations of the RTD curve, and an inappropriate assessment of the tracer injection time can lead to a significant change of the RTD curve. (C) 2014 Elsevier Ltd. All rights reserved.
KeywordFluidization Multiphase Flow Computational Fluid Dynamics Circulating Fluidized Bed Particle Clusters Solids Residence Time Distribution
SubtypeArticle
WOS HeadingsScience & Technology ; Technology
DOI10.1016/j.ces.2014.05.055
URL查看原文
Indexed BySCI
Language英语
WOS KeywordCIRCULATING FLUIDIZED-BED ; RADIOACTIVE PARTICLE TRACKING ; NEAR-WALL REGION ; KINETIC-THEORY ; NUMERICAL-SIMULATION ; FLOW STRUCTURE ; 2-FLUID MODEL ; FCC PARTICLES ; GAS ; DISPERSION
WOS Research AreaEngineering
WOS SubjectEngineering, Chemical
WOS IDWOS:000340931800026
Citation statistics
Cited Times:39[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Version出版稿
Identifierhttp://ir.ipe.ac.cn/handle/122111/11408
Collection研究所(批量导入)
AffiliationChinese Acad Sci, Inst Proc Engn, State Key Lab Multiphase Complex Syst, Beijing 100190, Peoples R China
Recommended Citation
GB/T 7714
Hua, Leina,Wang, Junwu,Li, Jinghai. CFD simulation of solids residence time distribution in a CFB riser[J]. CHEMICAL ENGINEERING SCIENCE,2014,117(9):264-282.
APA Hua, Leina,Wang, Junwu,&Li, Jinghai.(2014).CFD simulation of solids residence time distribution in a CFB riser.CHEMICAL ENGINEERING SCIENCE,117(9),264-282.
MLA Hua, Leina,et al."CFD simulation of solids residence time distribution in a CFB riser".CHEMICAL ENGINEERING SCIENCE 117.9(2014):264-282.
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