Gas-solid Flow Behaviors in a Pressurized Multi-stage Circulating Fluidized Bed with Geldart Group B Particles
-
Wei Nie
,
Junguo Li
,
Zhenhua Hao
Abstract
A comprehensive study of gas-solids flow behaviors was conducted in a novel multi-stage circulating fluidized bed (MCFB). Experiments were carried out in a cold model apparatus (a jetting fluidized bed, JFB, of 0.3 m diameter and 1.95 m tall, a riser of 0.15 m diameter and 12 m tall) at different elevated pressure, solids circulation rates and gas velocities. Geldart group B polystyrene particles of 400 μm in diameter and 1020 kg/m3 in density were used as bed materials. The characteristic of L-valve, axial and radial distributions of solids holdup were systematically tested at elevated pressures by pressure transducers with the frequency of 100 Hz and model PC6M of the optical fiber probes. Operating the L-valve at elevated pressure needs less cross-section average gas velocity compared to that at atmospheric pressure. Experimental results showed that under elevated pressure and high solids flow rate, the MCFB could more easily couple JFB with a riser, where the solids that entered could form three-level step-by-step supplement entrainment and multi-flow regimes formed. Besides, increasing operating pressure led to a higher the apparent solids holdup and local solids holdup. The local solids profiles behaved less uniform distribution at elevated pressure due to decreasing the gas velocity.
Nomenclature
- dp
Particle diameter (μm)
- f
Calibration function for optical fiber probe
- F
The wall friction and solid acceleration (kg/(m2s))
- g
Gravitational acceleration, m/s2
- Gs
Solids circulation rate (kg/(m2·s))
- H
Height, (m)
- ΔH
Height difference,
- ΔP
Pressure drop, (Pa)
- Ur,g
Riser’s superficial gas velocity, (m/s)
- Ut
Terminal velocity, (m/s)
- V(t)
Voltage time series (V)
- z
Distance above the gas distributor (m)
- Greek letters
- εs
Solids holdup (dimensionless)
- εs,mf
The highest solids holdup (dimensionless)
- εs(t)
Instantaneous solids holdup (dimensionless)
Average solids holdup in the entire column (dimensionless)
- ρp
Particle density (kg/m3)
- ρB
Bulk density (kg/m3)
- σ(εs)
Standard deviation of the radial solids holdup (dimensionless)
- σ(εs)
Max maximum possible standard deviation (dimensionless)
- Subscripts
- g
Gas
- s
Solid
Acknowledgements
This work was supported by the National Natural Science Foundation (NO. 21606250) and Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering (No. 2017-K02). Their supports are greatly appreciated.
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Supplementary Material
The online version of this article offers supplementary material (https://doi.org/10.1515/ijcre-2019-0087).
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- Articles
- Promoting Effects of Al on Ni-Based Catalyst for the Hydrodeoxygenation Performance of Ethyl Acetate
- Chalcopyrite Leaching Kinetics in the Presence of Methanol
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- Gas-solid Flow Behaviors in a Pressurized Multi-stage Circulating Fluidized Bed with Geldart Group B Particles
