Homogeneous bed expansion of FCC catalysts, influence of temperature on the parameters of the Richardson–Zaki equation

Lettieri, Paola; Newton, David E.; Yates, J.G.

doi:10.1016/s0032-5910(01)00463-6

Cited by 77 publications

(57 citation statements)

References 20 publications

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“…Several authors investigated powders flow behaviour at different temperature through fluidization tests [3][4][5][6][7] and measurements of interactive forces between particles [8][9][10][11][12]. However, a full understanding of the effect of temperature on interparticle interactions and flow properties of bulk solid is still challenging.…”

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confidence: 99%

Analysis of industrial reactive powders flow properties at high temperature

et al. 2017

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Section: Introductionmentioning

confidence: 99%

Analysis of industrial reactive powders flow properties at high temperature

et al. 2017

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“…Several studies available in the literature have addressed the experimental evaluation of the effect of temperature on fluidization behaviour (Xie and Geldart, 1995;Formisani et al, 1998Formisani et al, , 2002Lettieri et al, 2000Lettieri et al, , 2002Bruni et al, 2006), showing a significant change that cannot be entirely explained by taking into account only hydrodynamic forces. The authors provided an interpretation based on the hypothesis that temperature could increase the relative weight of IPFs with respect to HDFs.…”

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Experimental and theoretical analysis of TiO2 powders flow properties at ambient and high temperatures

Macrì

Lettieri

Poletto

2017

Chemical Engineering Science

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Highlights Temperature effect on bulk flow properties of TiO 2 powders is evaluated experimentally.  Measured properties are related to the microscopic IPFs by theoretical models.  A sensitivity analysis on models' parameters is performed. AbstractChanges of bulk flow properties of two different types of titanium dioxide powders are measured at room temperature and 500 °C using the High Temperature Annular Shear Cell.A significant increase of the macroscopic bulk flow properties is observed with increasing temperature, in particular with regards to the unconfined yield strength. Two different modelling approaches are proposed with the aim to relate the measured properties to the microscopic interactions between particles. The results indicate that both the model provides a good match with the experimental data when proper values for the models' parameters are taken into account. To this end, the sensitivity analysis for the main parameters of the models is performed.

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“…Whereas, for the fluidized bed of FCC catalysts, fluidization remains steady at gas velocities greater than the terminal setting velocity of a single particle. This phenomenon might be due to the cohesive inter-particle forces due to the Van der Waals attraction, which are responsible for agglomeration of particles and lead to a reduced drag force for FCC particles.Lettieri et al 16 found that, for the FCC catalyst in the fluidized bed, the experimentally obtained terminal velocity (u t *) is much higher than the calculated one (u t ). If the homogeneous bed was assumed to be characterized by the presence of clusters, the diameter of clusters, d p *, can be back-calculated from the experimental u t * values.…”

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confidence: 88%

“…If the homogeneous bed was assumed to be characterized by the presence of clusters, the diameter of clusters, d p *, can be back-calculated from the experimental u t * values. Lettieri et al 16 also calculated effective particle diameters in the range of 200-474 lm for FCC catalysts with Sauter mean diameters from 49 to 71 lm. Based on the results above, an effective mean diameter of 265 lm (the diameter of particle clusters) is determined instead of the actual 58 lm FCC particle to modify the Gidaspow drag force model in this article.…”

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CFD modeling of mass transfer and stripping efficiency in FCCU strippers

et al. 2008

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This article presents an experimental and computational study of mass transfer characteristics and stripping efficiency of bubbling fluidized beds within FCCU strippers. The hydrodynamic and mass transfer characteristics are investigated experimentally. Based on the granular kinetics theory, a two-fluid CFD model coupled with a modified Gidaspow drag model and an empirical mass transfer model has been developed and verified against the experimental results. The overall trend of the time-averaged bed density, concentration of tracer and stripping efficiency at various superficial gas velocities were in reasonable agreement with the experimental data. It was found that stripping efficiency depends strongly on the operating conditions as well as on the internal configuration of the strippers. Increasing superficial gas velocity increases stripping efficiency. Internal baffles improve break-up and redistribution of bubbles and enhance the gas-solids contacting remarkably, showing a benefit for the mass transfer in the V-baffled stripper. AIChE J, 54: 1164AIChE J, 54: -1177AIChE J, 54: , 2008 Keywords: fluidization, FCCU stripper, stripping efficiency, Eulerian simulation, FCC catalysts American Institute of Chemical Engineers IntroductionFluid catalytic cracking (FCC) is the main heavy oil conversion process in most petroleum refineries.1 Circulating fluidized bed technology is used in modern FCC units where cracking reactions take place as the vaporized gas oil feed and catalyst flow up the riser. Having been disengaged from the product gas, the catalyst needs to be regenerated because of deactivation due to coke deposition. However, hydrocarbon products are entrained, adsorbed, or present on the spent catalyst. It is important to strip these hydrocarbons off quickly and efficiently prior to regeneration. Incomplete stripping leads to loss of valuable product due to their combustion in the regenerator. The increase in hydrocarbon burned also increases the regenerator temperature, and subsequently, affects the FCC unit heat balance, while promoting faster catalyst degradation and mechanical wear of components. 2,3 Stripping is generally accomplished in a bubbling or turbulent fluidized bed by adding steam which bubbles upwards, counter-currently to the down flowing catalyst particles. 4 Understanding the hydrodynamics, mass and heat transfer in the stripper is essential for improving its performance and optimizing the design process. However, research on the stripper published in the open literature has been scarce until recently. Senior et al. 5 have described in detail the flow probCorrespondence concerning this article should be addressed to Chunming Xu at xcm@cup.edu.cn. American Institute of Chemical EngineersAIChE Journal May 2008 Vol. 54, No. 5 1164 lems encountered in commercial FCCU stripper operation. Cui et al. 6,7 investigated experimentally the gas-solids mixing and the effect of jet configuration on fluidized bed stripping in a dynamically scaled fluid coker stripper.With the increase of computational...

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Homogeneous bed expansion of FCC catalysts, influence of temperature on the parameters of the Richardson–Zaki equation

Cited by 77 publications

References 20 publications

Analysis of industrial reactive powders flow properties at high temperature

Analysis of industrial reactive powders flow properties at high temperature

Experimental and theoretical analysis of TiO2 powders flow properties at ambient and high temperatures

CFD modeling of mass transfer and stripping efficiency in FCCU strippers

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