Catalytic reaction in a circulating fluidized bed riser: Ozone decomposition

Li, Dongbing; Ray, Ajay K.; Ray, Madhumita B.; Zhu, Jesse

doi:10.1016/j.powtec.2013.01.015

Cited by 20 publications

(27 citation statements)

References 14 publications

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“…In general, the conversion of ozone increases with the solids holdup, as confirmed by other researchers . There appears to be a linear relationship between the total ozone conversion and the mean solids holdup as shown in Figure .…”

Section: Resultssupporting

confidence: 83%

“…Considering the numerous studies on hydrodynamics and hot model reactions in CFB riser reactors, not much efforts devoted to hydrodynamics and especially to reactor performance in downers in recent years . Previous studies using catalytic ozone decomposition as a model reaction to evaluate reactor performance were mainly focused on gas ‐ solids contacting in CFB risers . To the best of our knowledge, only two research groups carried out some introductory studies on the reactor performance in downers using this model reaction.…”

Section: Introductionmentioning

confidence: 99%

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Hydrodynamics and reactor performance evaluation of a high flux gas‐solids circulating fluidized bed downer: Experimental study

2014

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in Wiley Online Library (wileyonlinelibrary.com)Reactor performance of a high flux circulating fluidized bed (CFB) downer is studied under superficial gas velocities of 3-7 m/s with solids circulation rate up to 300 kg/m 2 s using ozone decomposition reaction. Results show that the reactant conversion in the downer is closely related to the hydrodynamics, with solids holdup being the most influential parameter on ozone decomposition. High degree of conversion is achieved at the downer entrance region due to strong gas-solids interaction as well as higher solids holdup and reactant concentration. Ozone conversion increases with the increase of solids circulation rate and/or the decrease of superficial gas velocity. Overall conversion in the CFB downer is less than but very close to that in an ideal plug flow reactor indicating a good reactor performance in the downer because of the nearly "ideal" hydrodynamics in downer reactors. Figure 1. Schematic diagram of the multifunctional CFB and ozone testing system.

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Section: Resultssupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Hydrodynamics and reactor performance evaluation of a high flux gas‐solids circulating fluidized bed downer: Experimental study

2014

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“…8 displays the relationship between overall conversion and the solids holdup in the riser and downer reactors. Generally, the conversion of ozone increases with the solids holdup, as confirmed by other researchers [9,29,30]. There appears to be a linear relationship between the total ozone conversion and the mean solids holdup in both riser and downer reactors.…”

Section: Relationship Between Solids Holdup Damköhler Number and Ovesupporting

confidence: 70%

Performance evaluation of high density riser and downer: Experimental study using ozone decomposition

Wang

Zhu

Barghi

2015

Chemical Engineering Journal

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“…Otherwise, by assuming a homogeneous system, e.g., ideal plug flow, overestimation of the conversion rate in heterogeneous systems is likely to result. The contact efficiency could be determined by assuming a riser as a steady-state plug flow reactor: 24 , 25 , 48 , 50 , 63 with a solution: where s is the averaged solids volume fraction in a slice of thickness Δz , U the gas superficial velocity, K ov the apparent volumetric reaction rate constant, γ pf a gas–solid contact efficiency, and Da the Damköhler number defined as The gas–solid contact efficiency γ pf could be computed at different axial increments of Δz , by quantifying the contact efficiency as the ratio between the apparent conversion rate and the conversion obtained when a 1D plug flow model is assumed, ignoring any heterogeneity.…”

Section: Methodsmentioning

confidence: 99%

Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) Study of Mass-Transfer Mechanisms in Riser Flow

Varas

Peters

Kuipers

2017

Ind. Eng. Chem. Res.

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We report a computational fluid dynamics–discrete element method (CFD-DEM) simulation study on the interplay between mass transfer and a heterogeneous catalyzed chemical reaction in cocurrent gas-particle flows as encountered in risers. Slip velocity, axial gas dispersion, gas bypassing, and particle mixing phenomena have been evaluated under riser flow conditions to study the complex system behavior in detail. The most important factors are found to be directly related to particle cluster formation. Low air-to-solids flux ratios lead to more heterogeneous systems, where the cluster formation is more pronounced and mass transfer more influenced. Falling clusters can be partially circumvented by the gas phase, which therefore does not fully interact with the cluster particles, leading to poor gas–solid contact efficiencies. Cluster gas–solid contact efficiencies are quantified at several gas superficial velocities, reaction rates, and dilution factors in order to gain more insight regarding the influence of clustering phenomena on the performance of riser reactors.

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Catalytic reaction in a circulating fluidized bed riser: Ozone decomposition

Cited by 20 publications

References 14 publications

Hydrodynamics and reactor performance evaluation of a high flux gas‐solids circulating fluidized bed downer: Experimental study

Hydrodynamics and reactor performance evaluation of a high flux gas‐solids circulating fluidized bed downer: Experimental study

Performance evaluation of high density riser and downer: Experimental study using ozone decomposition

Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) Study of Mass-Transfer Mechanisms in Riser Flow

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