Distributions of solids holdup and particle velocity in the FCC riser with downward pointed feed injection scheme

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Effects of different gaseous nozzle injections on gas−solid dynamic mixing in FCC riser are experimentally studied by calculating the time fractions of the proposed phases (gas, diluter/denser dispersed particles, and cluster). Generally, a more dispersed particulate phase can be obtained when jets are downward. By analyzing the effects of operating parameters, it is shown that the larger jet/prelift flow momentum ratio increases the proportions of the gas and cluster phases, and the proportion of the useful denser, dispersed particulate phase decreases accordingly when nozzles are upward. For the downward pointed jets, the momentum ratio only affects the radial time fraction distributions of different phases. The cross-sectional time fractions of each phase change little with momentum ratios, indicating a good operational flexibility. To obtain better gas−solid dynamic mixing, suitable setting angle of nozzles is 30−45°when nozzles are mounted downward.

Section: Analysis Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of Different Gaseous Nozzle Injections on Gas–solid Dynamic Mixing in FCC Riser

Yan

Fan

et al. 2018

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“…Another important application of the CFB technology is the fluid catalytic cracking (FCC) using Geldart A particles with average diameter of 60–80 μm. The hydrodynamics in the CFB reactor with Geldart A particles has been studied in several decades. − It should be pointed out that the height of the riser has an obvious effect on the hydrodynamics in CFB systems with Geldart A particles . The previous studies almost always focused on the flow behavior in the CFB risers with heights less than 20 m, ,− which is lower than that in the industrial processes.…”

Section: Introductionmentioning

confidence: 99%

Flow of High Solids Density Suspensions in an 18 m High Circulating Fluidized Bed

Wang

Lan

et al. 2019

The detailed distributions of solids holdup in an 18 m high-density circulating fluidized bed are mapped under various operating conditions with fluid catalytic cracking particles. Solids flux (G s) is as high as 1000 kg/(m2 s) when the superficial gas velocity (U g) ranges from 5 to 9 m/s and high-density operation is achieved. For axial distribution, solids holdup decreases exponentially along the riser with a solids holdup up to 0.17 at the riser exist, indicating the high-density operation has been achieved when G s > 800 kg/(m2 s). For radial distribution, a parabolic radial profile at high-density conditions also replaces the “core-annual” flow structure at low-density conditions. Particles can be accelerated to the axial height of 12 m under G s > 800 kg/(m2 s). Both increasing U g and/or decreasing G s can enhance flow development at high-density conditions. The solids-to-air ratio is almost the same at about 70 when high-density operations are achieved.

“…Results show that the mixing of jets with particles is better when the injection is downward. Moreover, Yan et al − investigated the trajectories of injections and the dynamic characteristics of the two-phase gas–solid flow under different types of jet gas.…”

Section: Introductionmentioning

confidence: 99%

Mixing of Jet Gas with Catalyst Particles in Fluid Catalytic Cracking Risers

Yan

Fan

et al. 2019

Self Cite

The residence time distributions of upward and downward gas injections in a fluid catalytic cracking riser were investigated by large-scale cold model experiments. The tanks-in-series model was employed to describe the local mixing of feed jets with catalyst particles. The model parameter M at various axial and radial measuring points was obtained by using the helium tracer method. On this basis, M was fitted with the jet–catalyst flow momentum ratio and the axial height. By knowing M of the full mixing zone of the riser, this method calculates the influence height of jets above the injection point. Results show that the downward feed offers a fuller mixing environment for jets and catalysts in their initial contact region. Besides, the influence height above the nozzles in the downward injection scheme is over 50% shorter than that of the upward jet case. This study confirms that the downward jets can provide a more ideal environment for jet–catalyst mixing.