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Three-component solids velocity measurements in the outlet section of a riser
Maria N Pantzali1, Javier Marqués de Marino1, Guy B Marin1
1Laboratory for Chemical Technology Faculty of Engineering and Architecture, Ghent University Ghent Belgium.
Aiche Journal. American Institute of Chemical Engineers
|August 20, 2019
Summary
This study reveals particle downflow and solids vortex formation in a cylindrical riser using laser Doppler anemometry. These phenomena, observed under dilute flow conditions, impact flow dynamics and turbulence.
Area of Science:
- Fluid dynamics
- Particle-laden flows
- Chemical engineering
Background:
- Understanding particle behavior in risers is crucial for optimizing industrial processes like fluidized catalytic cracking.
- Dilute flow regimes present unique challenges in predicting particle movement and distribution.
Purpose of the Study:
- To present the first coincident three-component particle velocity measurements in a cylindrical riser under dilute flow conditions.
- To investigate the formation and characteristics of a solids vortex and particle downflow at the riser outlet.
Main Methods:
- Utilized two laser Doppler anemometry (LDA) probes for simultaneous, three-component particle velocity measurements.
- Conducted experiments in a 9 m high cylindrical riser at dilute flow conditions.
- Analyzed particle velocity averages, fluctuations, and turbulence intensity.
Main Results:
- Observed a solids vortex near the T-outlet and particle downflow along the riser wall.
- Particle downflow height increased with higher gas flow rates.
- Identified regions of increased velocity fluctuations corresponding to the solids vortex and downflow.
- Found time and ensemble velocity averages to be unequal in the downflow region, indicating complex momentum transfer.
Conclusions:
- The study provides novel insights into particle dynamics in risers, particularly the formation of solids vortex and downflow.
- Observed phenomena are linked to the transformation of axial momentum into radial and azimuthal components, generating shear stresses.
- Turbulence intensity measurements effectively delineate the boundaries of the particle downflow region.
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