Fluidization, Mixing and Segregation of a Biomass-Sand Mixture in a Fluidized Bed

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Yong Zhang ◽  
Baosheng Jin ◽  
Wenqi Zhong
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Visual Observation ◽  
Fluctuation Analysis ◽  
Mixing Ratio ◽  
Dynamic Features ◽  
Pressure Transducers ◽  
Sand Mixture ◽  
Wide Range ◽  
Initial Packing

Fluidization, mixing and segregation of a biomass-sand mixture in a 3D gas-fluidized bed have been investigated by means of visual observation, pressure fluctuation analysis and the bed-frozen method. Three types of mixtures are considered, in which biomass is a thin long stalk, and sand belongs to the Geldart B category. Experiments are carried out in a segmented fluidized bed equipped with multiple pressure transducers. Three initial packing conditions and two experiment procedures are used. The fluidization velocity varies to cover a wide range. Results show that in the local fluidization region, the mixing and segregation patterns are sensitive to the initial packing condition. In the case of a fully segregated state with biomass at the bottom, the bed inversion can be significantly observed due to the great segregation tendency of biomass. Further analyses indicate that the mixing ratio exerts a subtle influence on the competition between mixing and segregation by disturbing the coalescence and break-up of the bubble. In addition, the pressure fluctuation signal proves to be helpful in understanding the dynamic features of the phenomenology.

scholarly journals Agglomeration detection by pressure fluctuation analysis during Cynara cardunculus L. gasification in a fluidized bed

2016 ◽  
Vol 284 ◽  
pp. 640-649 ◽  
Author(s):  
Jesús Gómez-Hernández ◽  
Daniel Serrano ◽  
Antonio Soria-Verdugo ◽  
Sergio Sánchez-Delgado
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Fluctuation Analysis ◽  
Cynara Cardunculus

scholarly journals Deagglomeration of Ultrafine Hydrophilic Nanopowder Using Low-Frequency Pulsed Fluidization

Nanomaterials ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 388 ◽  
Author(s):  
Ebrahim H. Al-Ghurabi ◽  
Mohammed Shahabuddin ◽  
Nadavala Siva Kumar ◽  
Mohammad Asif
Keyword(s):  
Fluidized Bed ◽  
Low Frequency ◽  
Frequency Domain Analysis ◽  
Wave Flow ◽  
Velocity Change ◽  
Pressure Transducers ◽  
Wide Range ◽  
Transient Data ◽  
Flow Pulsations ◽  
Sensitive Pressure

Low-frequency flow pulsations were utilized to improve the hydrodynamics of the fluidized bed of hydrophilic ultrafine nanosilica powder with strong agglomeration behavior. A gradual fluidization of unassisted fluidized bed through stepwise velocity change was carried out over a wide range of velocities followed by a gradual defluidization process. Bed dynamics in different regions of the fluidized bed were carefully monitored using fast and sensitive pressure transducers. Next, 0.05-Hz square-wave flow pulsation was introduced, and the fluidization behavior of the pulsed fluidized bed was rigorously characterized to delineate its effect on the bed hydrodynamics by comparing it with one of the unassisted fluidized bed. Flow pulsations caused a substantial decrease in minimum fluidization velocity and effective agglomerate diameter. The frequencies and amplitudes of various events in different fluidized bed regions were determined by performing frequency domain analysis on real-time bed transient data. The pulsations and their effects promoted deagglomeration and improved homogeneity of the pulsed fluidized bed.

Horizontal Pressure Fluctuation in Bubbling Fluidized Bed

2003 ◽  
Author(s):  
Vesa V. Walle´n
Keyword(s):  
Pressure Gradient ◽  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Middle Part ◽  
Biomass Combustion ◽  
Bottom Part ◽  
Pressure Transducers ◽  
Bubbling Fluidized Bed ◽  
Horizontal Pressure

Pressure measurements were conducted in a two-dimensional hot atmospheric bubbling fluidized bed reactor in the laboratory of Energy and Process Engineering at Tampere University of Technology. A set of six fast pressure transducers was used to detect the rapid pressure fluctuations inside the bubbling bed of the reactor. These pressure transducers were placed both vertically and horizontally into the reactor. From these measurements it was found that the vertical pressure fluctuation took place at the same time at different levels of the bed. Also the same fluctuation could be seen under the air distributor. The horizontal pressure fluctuation was found to vary both by place and time. At the bottom part of the bed the highest pressure peaks was found at centre of the bed. Most of the time there was a pressure gradient the highest pressure being in the centre of the bed. This gradient creates horizontal flow of gases from middle to the sides. The velocity of this flow varies with the size of the pressure gradient. The opposite effect can be found in the upper part of the bed. The highest pressure was no more in the middle part of the bed. Instead, it was found to be between the centre of the bed and left and right walls. The pressure was low at the walls but also rather low at the middle of the bed. There must be flow towards the walls and to the centre axis. These pressure fluctuations can provide an explanation for the well-known “wandering plume” effect. They can also give a tool to better describe the mixing inside a bubbling fluidized bed. This kind of tool is needed when biomass combustion is modelled in bubbling fluidized bed.

Pressure fluctuation analysis of solid exchange in a dual-leg fluidized bed

2012 ◽  
Vol 224 ◽  
pp. 69-75 ◽  
Author(s):  
Chunzhen Yang ◽  
Yufeng Duan ◽  
Haitao Hu ◽  
Changsui Zhao
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Fluctuation Analysis

Pressure Fluctuation Analysis in Gas-Solid Fluidized Beds Using CFD Simulations

2012 ◽  
Author(s):  
Mirka Deza ◽  
Francine Battaglia
Keyword(s):  
Binary Mixture ◽  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Design Tool ◽  
Fluctuation Analysis ◽  
Valuable Insight ◽  
Turbulent Regime ◽  
Local Pressure ◽  
Long Time

Reliable computational methods provide valuable insight into gas-solid flow processes and can be used as a design tool. Of particular interest is the hydrodynamics of a binary mixture of sand-biomass in a fluidized bed. Our study interprets the hydrodynamic states of a fluidized bed by analyzing the local pressure fluctuations of beds of sand and a mixture of cotton stalks and sand over long time periods. Standard deviation of pressure drop will determine different fluidization regimes at inlet gas velocities ranging from 2 to 9 times the minimum fluidization velocity. Bode plots will present the pressure spectra and reveal characteristic frequencies that describe the bed hydrodynamics for different fluidization regimes. This works contribution will present CFD as a useful tool to perform pressure fluctuation analysis, the study of pressure fluctuations in the turbulent regime and the analysis of a binary mixture using CFD.

Pressure-fluctuation analysis of a Gas–Solid fluidized bed using the wigner distribution

AIChE Journal ◽  
1997 ◽  
Vol 43 (2) ◽  
pp. 345-356 ◽  
Author(s):  
Zhen He ◽  
Dongming Zhang ◽  
Bochuan Cheng ◽  
Weidong Zhang
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Wigner Distribution ◽  
Fluctuation Analysis

scholarly journals Line-of-Sight Winds and Doppler Effect Smearing in ACE-FTS Solar Occultation Measurements

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 680
Author(s):  
Chris D. Boone ◽  
Johnathan Steffen ◽  
Jeff Crouse ◽  
Peter F. Bernath
Keyword(s):  
Atmospheric Chemistry ◽  
Doppler Effect ◽  
Line Of Sight ◽  
Measured Signal ◽  
Mixing Ratio ◽  
Model Calculations ◽  
Doppler Shifts ◽  
Solar Occultation ◽  
Wide Range ◽  
Wind Profiles

Line-of-sight wind profiles are derived from Doppler shifts in infrared solar occultation measurements from the Atmospheric Chemistry Experiment Fourier transform spectrometers (ACE-FTS), the primary instrument on SCISAT, a satellite-based mission for monitoring the Earth’s atmosphere. Comparisons suggest a possible eastward bias from 20 m/s to 30 m/s in ACE-FTS results above 80 km relative to some datasets but no persistent bias relative to other datasets. For instruments operating in a limb geometry, looking through a wide range of altitudes, smearing of the Doppler effect along the line of sight can impact the measured signal, particularly for saturated absorption lines. Implications of Doppler effect smearing are investigated for forward model calculations and volume mixing ratio retrievals. Effects are generally small enough to be safely ignored, except for molecules having a large overhang in their volume mixing ratio profile, such as carbon monoxide.

scholarly journals Investigation into the Relationship between Super-Knock and Misfires in an SI GDI Engine

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2099
Author(s):  
Jian Gao ◽  
Anren Yao ◽  
Yeyi Zhang ◽  
Guofan Qu ◽  
Chunde Yao ◽  
...  
Keyword(s):  
Pressure Fluctuation ◽  
Direct Injection ◽  
Exhaust Valve ◽  
Gasoline Direct Injection ◽  
Exhaust Pipe ◽  
Pressure Transducers ◽  
Spark Plug ◽  
Si Engines ◽  
Gdi Engine ◽  
The Relationship

The super-knock poses new challenges for further increasing the power density of spark ignition (SI) engines. The critical factors and mechanism connecting regarding the occurrence of super-knock are still unclear. Misfire is a common phenomenon in SI engines that the mixture in cylinder is not ignited normally, which is often caused by spark plug failure. However, the effect of misfire on engine combustion has not been paid enough attention to, particularly regarding connection to super-knock. The paper presents the results of experimental investigation into the relationship between super-knock and misfires at low speed and full load conditions. In this work, a boosted gasoline direct injection (GDI) engine with an exhaust manifold integrated in the cylinder head was employed. Four piezoelectric pressure transducers were used to acquire the data of a pressure trace in cylinder. The spark plugs of four cylinders were controlled manually, of which the ignition system could be cut off as demanded. In particular, a piezoelectric pressure transducer was installed at the exhaust pipe before the turbocharger to capture the pressure traces in the exhaust pipe. The results illustrated that misfires in one cylinder would cause super-knock in the other cylinders as well as the cylinder of itself. After one cylinder misfired, the unburned mixture would burn in the exhaust pipe to produce oscillating waves. The abnormal pressure fluctuation in the exhaust pipe was strongly correlated with the occurrence of super-knock. The sharper the pressure fluctuation, the greater the intensity of knock in the power cylinder. The cylinder whose exhaust valve overlapped with the exhaust valve of the misfired cylinder was prone to super-knock.

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