scholarly journals Effect of Particle Size on Carbon Nanotube Aggregates Behavior in Dilute Phase of a Fluidized Bed

Processes ◽  
2018 ◽  
Vol 6 (8) ◽  
pp. 121 ◽  
Author(s):  
Sung Kim
Keyword(s):  
Particle Size ◽  
Carbon Nanotube ◽  
Fluidized Bed ◽  
Laser Sheet ◽  
Scale Up ◽  
Experimental Parameter ◽  
Aggregate Size ◽  
Chemical Vapor ◽  
Gas Velocity ◽  
Effect Of Particle Size

Fluidized bed reactors have been increasingly applied for mass production of Carbon Nanotube (CNT) using catalytic chemical vapor deposition technology. Effect of particle size (dp = 131 μm and 220 μm) on fluidization characteristics and aggregation behavior of the CNT particles have been determined in a fluidized bed for its design and scale-up. The CNT aggregation properties such as size and shape were measured in the dilute phase of a fluidized bed (0.15 m-ID × 2.6 m high) by the laser sheet technique for the visualization. Two CNT particle beds showed different tendency in variations of the aggregates factors with gas velocity due to differences in factors contributing to the aggregate formation. The CNT particles with a larger mean size presented as relatively larger in the aggregate size than the smaller CNT particles at given gas velocities. The aggregates from the large CNT particles showed a sharp increase in the aspect ratio and rapid decrease in the roundness and the solidity with gas velocity. A possible mechanism of aggregates formation was proposed based on the variations of aggregates properties with gas velocity. The obtained Heywood diameters of aggregates have been firstly correlated with the experimental parameter.

scholarly journals Visualization of Carbon Nanotube Aggregates in Dilute Phase of a Fluidized Bed

2018 ◽  
Vol 7 (3.34) ◽  
pp. 534
Author(s):  
Sae Han Park ◽  
Sung Won Kim
Keyword(s):  
Carbon Nanotube ◽  
Bulk Density ◽  
Fluidized Bed ◽  
High Speed ◽  
Laser Sheet ◽  
Scale Up ◽  
Average Diameter ◽  
Aggregation Behavior ◽  
Aggregation Process ◽  
Size And Shape

Background/Objectives: Fluidization characteristics and aggregation behavior of carbon nanotube (CNT) particles have been determined in the freeboard of a bubbling fluidized for the design and scale-up of the process.Methods/Statistical analysis: The aggregation behavior of the CNT particles was observed in a gas solid fluidized bed (0.15 m i.d. X 2.6 m high) using laser sheet technique for their visualization. A high speed camera was installed at the height of 0.67, 1.05 and 1.50 m above the gas distributor to observe the CNT aggregates behavior and determine their size and shape. The Image J was applied to process the obtained images.Findings: Effect of height in the reactor on aggregation of CNT particles have been determined. The axial local bulk density distribution is almost similar with a general bubbling fluidized bed such as Geldart A or Geldar B particles, which shows typically a dense bed at the bottom of the reactor and a decrease of the local bulk density with increasing height. The Feret and Heywood diameters of the aggregates are larger than the average diameter of the CNT particles, indicating that the CNT particles form the aggregates by physical entanglements and van der Waals force in the dilute phase of fluidized bed. A possible mechanism of aggregates formation was proposed based on the variation of size and shape of CNT aggregation with the height. The aggregation process in dilute phase is attributed largely to nanotubes stripping off the surface of CNT particles in addition to the inter-particle aggregation. The aggregation process affects the decrease of aspect ratio and the increase of solidity of aggregates with increasing the height.Improvements/Applications: The obtained results on the CNT properties could be used for the design of cyclone and the modeling of heat transfer in the fluidized bed reactor.  

scholarly journals Effect of particle size and bed height on the characteristic of a fluidized bed dryer

2020 ◽  
Vol 7 (1) ◽  
pp. 1738185
Author(s):  
Eflita Yohana ◽  
Muchammad ◽  
Mohammad Tauviqirrahman ◽  
Awallina Ani Sayekti ◽  
Kwang-Hwan Choi ◽  
...  
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Fluidized Bed Dryer ◽  
Bed Height ◽  
Effect Of Particle Size

scholarly journals Effect of Bed Particle Size on Thermal Performance of a Directly-Irradiated Fluidized Bed Gas Heater

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 967
Author(s):  
Sae Han Park ◽  
Chae Eun Yeo ◽  
Min Ji Lee ◽  
Sung Won Kim
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Gas Velocity ◽  
Bubble Behavior ◽  
Heat Transfer Characteristics ◽  
Maximum Value ◽  
Solar Thermal Collector ◽  
Sic Particle

There is a growing interest in a fluidized bed particle receiver that directly irradiates sunlight to particles in the fluidized bed as a solar thermal collector for heating. Thermal performance of directly-irradiated fluidized bed gas heater is strongly affected by the physical properties of the particles. The effect of SiC particle size on heat transfer characteristics in the solar fluidized bed gas heater (50 mm-ID × 100 mm high) has been determined. The outlet gas temperatures showed a maximum value with increasing gas velocity due to the particles motion by bubble behavior in the bed, and the maximum values were found at 3.6 times of Umf for fine SiC and less than 2.0 times of Umf for coarse SiC. Heat absorption from the receiver increased with increasing gas velocity, showing with maximum 18 W for the fine SiC and 23 W for the coarse SiC at 4.5 times of Umf. The thermal efficiency of the receiver increased with increasing gas velocity, but was affected by the content of finer particles. The maximum thermal efficiency of the receiver was 14% for fine SiC and 20% for coarse SiC within the experimental range, but showing higher for the fine SiC at the same gas velocity. A design consideration was proposed to improve the thermal efficiency of the system.

scholarly journals Effect of particle size on elutriation rate constant for a fluidized bed.

1987 ◽  
Vol 20 (5) ◽  
pp. 498-504 ◽  
Author(s):  
KUNIO KATO ◽  
SINJI KANBARA ◽  
TORU TAJIMA ◽  
HIDEKI SHIBASAKI ◽  
KENJI OZAWA ◽  
...  
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Rate Constant ◽  
Effect Of Particle Size

scholarly journals Analysis of the Hydrodynamic Effects of Gas Permeation in a Pilot-Scale Fluidized Bed Membrane Reactor

2018 ◽  
Vol 9 (1) ◽  
pp. 67
Author(s):  
Chenxi Bai ◽  
Yao Xiao ◽  
Ruifeng Peng ◽  
John Grace ◽  
Yumin Chen
Keyword(s):  
Fluidized Bed ◽  
Bubble Size ◽  
Membrane Reactor ◽  
Scale Up ◽  
Pilot Scale ◽  
Gas Permeation ◽  
Gas Extraction ◽  
Gas Velocity ◽  
Attenuation Rate ◽  
Hydrodynamic Effects

This study experimentally investigates the effects of gas extraction/addition, via multiple vertical membrane panels, on the hydrodynamics in different regions of a pilot-scale gas fluidized bed membrane reactor (FBMR), based on differential pressure signals measured at different vertical bed sections at high temperature. In a bed section where membrane panels were installed and activated, the extraction of gas caused the average bubble size to increase, but decreased the number of small- and medium-sized bubbles. This effect of gas extraction penetrated into bed sections above the active membrane panel, but attenuated with increasing distance away from the extraction location. The attenuation rate was much faster in FBMR with lower bed voidage, mainly due to the large decrease of the drag force exerted by gas extraction on fluidizing gas in a denser bed. With the same inlet gas velocity, gas addition favored the growth of bubbles, especially in the upper bed sections compared with operation without gas permeation. The increase of the effective fluidizing velocity was the major reason for the increase of the bubble size during gas addition. These findings preliminarily suggest that membrane units should not be installed in or below fast-reacting zones in a scale-up FBMR, and operation with a lower bed voidage is preferable to avoid the formation of large bubbles enhanced by gas extraction.

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