Effects of superficial gas velocity and temperature on entrainment and electrostatics in gas–solid fluidized beds

The gas–liquid hydrodynamics and mass transfer were studied in a concentric tube internal jet-loop airlift reactor with a conical bottom. Comparing with a standard design, the gas separator was equipped with an adjustable deflector placed above the riser. The effect of riser superficial gas velocity uSGR on the total gas holdup εGT, homogenization time tH, and overall volumetric liquid-phase mass transfer coefficient kLa was investigated in a laboratory bioreactor, of 300 mm in inner diameter, in a two-phase air–water system and three-phase air–water–PVC–particle system with the volumetric solid fraction of 1% for various deflector clearances. The airlift was operated in the range of riser superficial gas velocity from 0.011 to 0.045 m/s. For the gas–liquid system, when reducing the deflector clearance, the total gas holdup decreased, the homogenization time increased twice compared to the highest deflector clearance tested, and the overall volumetric mass transfer coefficient slightly increased by 10–17%. The presence of a solid phase shortened the homogenization time, especially for lower uSGR and deflector clearance, and reduced the mass transfer coefficient by 15–35%. Compared to the gas–liquid system, the noticeable effect of deflector clearance was found for the kLa coefficient, which was found approx. 20–29% higher for the lowest tested deflector clearance.

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Effect of Surfactants on Gas Holdup in Shear-Thinning Fluids

International Journal of Chemical Engineering ◽

10.1155/2017/9062649 ◽

2017 ◽

Vol 2017 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Shaobai Li ◽

Siyuan Huang ◽

Jungeng Fan

Keyword(s):

Experimental Data ◽

Liquid Phase ◽

Sodium Dodecyl ◽

Shear Thinning ◽

Gas Holdup ◽

Bubble Columns ◽

Gas Velocity ◽

Shear Thinning Fluids ◽

Liquid Surface Tension ◽

Superficial Gas Velocity

In this study, the gas holdup of bubble swarms in shear-thinning fluids was experimentally studied at superficial gas velocities ranging from 0.001 to 0.02 m·s−1. Carboxylmethyl cellulose (CMC) solutions of 0.2 wt%, 0.6 wt%, and 1.0 wt% with sodium dodecyl sulfate (SDS) as the surfactant were used as the power-law (liquid phase), and nitrogen was used as the gas phase. Effects of SDS concentration, rheological behavior, and physical properties of the liquid phase and superficial gas velocity on gas holdup were investigated. Results indicated that gas holdup increases with increasing superficial gas velocity and decreasing CMC concentration. Moreover, the addition of SDS in CMC solutions increased gas holdup, and the degree increased with the surfactant concentration. An empirical correlation was proposed for evaluating gas holdup as a function of liquid surface tension, density, effective viscosity, rheological property, superficial gas velocity, and geometric characteristics of bubble columns using the experimental data obtained for the different superficial gas velocities and CMC solution concentrations with different surfactant solutions. These proposed correlations reasonably fitted the experimental data obtained for gas holdup in this system.

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CFD-DEM Numerical Simulation and Experimental Validation of Heat Transfer and Two-Component Flow in Fluidized Bed

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2016-0207 ◽

2017 ◽

Vol 16 (1) ◽

Cited By ~ 1

Author(s):

Feihong Guo ◽

Zhaoping Zhong

Keyword(s):

Heat Transfer ◽

Numerical Simulation ◽

Fluidized Bed ◽

Quartz Sand ◽

Thermal Imager ◽

Gas Velocity ◽

Bed Height ◽

Two Component ◽

Superficial Gas Velocity ◽

Infrared Thermal Imager

AbstractBased on the improved computational fluid dynamics and discrete element method (CFD-DEM), heat transfer and two-component flow of biomass and quartz sand have been studied from experiments and numerical simulation in this paper. During experiments, the particle temperature and moving images are respectively recorded by infrared thermal imager and high speed camera. With the increase of the velocity, the mixing index (MI) and the cooling rate of the particles are rising. Due to larger heat capacity and mass, the temperature of biomass drops slower than that of quartz sand. Fictitious element method is employed to solve the incompatibility of the traditional CFD-DEM where the cylindrical biomass are considered as an aggregation of numerous fictitious sphere particles arranged in certain sequence. By the comparison of data collected by infrared thermal imager and the simulated results, it can be concluded that experimental data is basically agreement with numerical simulation results. Directly affected by inflow air (25℃), the average temperature of particles in the bed height area (h>30 mm) is about 3 degrees lower than that of the other heights. When the superficial gas velocity is larger, the fluidization is good, and the gas temperature distribution is more uniform in the whole area. On the contrary, bubbles are not easy to produce and the fluidization is restricted at lower superficial gas velocity. Gas-solid heat transfer mainly exists under the bed height of 10 mm, and decreases rapidly on fluidized bed height. The mixing index (MI) is employed to quantitatively discuss the mixing effectiveness, which first rises accelerate, then rising speed decreases, finally tends to a upper limit.

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Gas hold-up in a three-phase reciprocating plate column

Journal of the Serbian Chemical Society ◽

10.2298/jsc0511363n ◽

2005 ◽

Vol 70 (11) ◽

pp. 1363-1371 ◽

Cited By ~ 2

Author(s):

Ljubisa Nikolic ◽

Vesna Nikolic ◽

Vlada Veljkovic ◽

Dejan Skala

Keyword(s):

Solid Phase ◽

Liquid System ◽

Column Diameter ◽

Gas Velocity ◽

Vibration Intensity ◽

Three Phase ◽

Superficial Gas Velocity ◽

Phase Column ◽

Plate Column ◽

Good Agreement

The influence of the geometry of a reciprocating plate column (diameter), superficial gas velocity, vibration intensity and content of the solid phase in the column on the gas hold-up in a three phase column (G-L-S) were investigated in this study. For comparison, the gas hold-up was also analyzed in a gas-liquid system (G-L) in the same type of column. Good agreement between the experimentally determined values of the gas hold-up and those calculated on the basis of the derived correlation for the G-L and G-L-S system was obtained.

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Study on Fluidization Characteristics of Magnetically Fluidized Beds for Microfine Particles

Minerals ◽

10.3390/min12010061 ◽

2022 ◽

Vol 12 (1) ◽

pp. 61

Author(s):

Yakun Tian ◽

Shulei Song ◽

Xuan Xu ◽

Xinyu Wei ◽

Shanwen Yan ◽

...

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Fluidized Bed ◽

Magnetic Field Strength ◽

Fluidized Beds ◽

Expansion Rate ◽

Gas Velocity ◽

Bed Height ◽

Bed Expansion ◽

The Magnetic Field

The bed pressure drop, minimum fluidized gas velocity, bed density, and bed expansion rate are important parameters characterizing the fluidization characteristics of gas-solid fluidized beds. By analyzing these parameters, the advantages and disadvantages of the fluidization state can be known. In this study, experiments were conducted to study the fluidization characteristics of a gas-solid magnetically fluidized bed for microfine particles by changing the magnetic field strength, magnetic field addition sequence, and static bed height. The experimental results show that when the magnetic field strength increased from 0 KA/m to 5 KA/m, the minimum fluidized gas velocity of particles increased from 4.42 cm/s to 10.32 cm/s, while the bed pressure drop first increased and then decreased. When the magnetic field strength is less than 3.4 KA/m, the microfine particles in the bed are mainly acted on by the airflow; while when the magnetic field strength is greater than 3.4 KA/m, the microfine particles are mainly dominated by the magnetic field. The magnetic field addition sequence affects the fluidization quality of microfine particles. The fluidized bed with ‘adding magnetic field first’ shows a more stable fluidization state than ‘adding magnetic field later’. Increasing of the static bed height reduces the bed expansion rate. The bed expansion rate is up to 112.5% at a static bed height of h0 = 40 mm and H = 5 KA/m. This will broaden the range of density regulation of a single magnetic particle and lay the advantage of gas-solid magnetically fluidized bed for microfine particles in the field of separation of fine coal.

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The gas holdup in a multiphase reciprocating plate column filled with carboxymethylcellulose solutions

Journal of the Serbian Chemical Society ◽

10.2298/jsc0512533s ◽

2005 ◽

Vol 70 (12) ◽

pp. 1533-1544 ◽

Cited By ~ 3

Author(s):

Ivica Stamenkovic ◽

Olivera Stamenkovic ◽

Ivana Bankovic-Ilic ◽

Miodrag Lazic ◽

Vlada Veljkovic ◽

...

Keyword(s):

Liquid Phase ◽

Power Consumption ◽

Rheological Properties ◽

Gas Holdup ◽

Gas Velocity ◽

Vibration Intensity ◽

Three Phase ◽

Solids Content ◽

Superficial Gas Velocity ◽

Plate Column

Gas holdup was investigated in a gas-liquid and gas-liquid-solid reciprocating plate column (RPC) under various operation conditions. Aqueous carboxymethyl cellulose (sodium salt, CMC) solutions were used as the liquid phase, the solid phase was spheres placed into interplate spaces, and the gas phase was air. The gas holdup in the RPC was influenced by: the vibration intensity, i.e., the power consumption, the superficial gas velocity, the solids content and the rheological properties of the liquid phase. The gas holdup increased with increasing vibration intensity and superficial gas velocity in both the two- and three-phase system. With increasing concentration of the CMC PP 50 solution (Newtonian fluid), the gas holdup decreased, because the coalescence of the bubbles was favored by the higher liquid viscosity. In the case of the CMC PP 200 solutions (non-Newtonian liquids), the gas holdup depends on the combined influence of the rheological properties of the liquid phase, the vibration intensity and the superficial gas velocity. The gas holdup in the three-phase systems was greater than that in the two-phase ones under the same operating conditions. Increasing the solids content has little influence on the gas holdup. The gas holdup was correlated with the power consumption (either the time-averaged or total power consumption) and the superficial gas velocity.

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Frictional Pressure Drop and Liquid Holdup of Churn Flow in Vertical Pipes with Different Viscosities

Geofluids ◽

10.1155/2021/6661014 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Zilong Liu ◽

Yubin Su ◽

Ming Lu ◽

Zilong Zheng ◽

Ruiquan Liao

Keyword(s):

Pressure Drop ◽

Liquid Velocity ◽

Gas Velocity ◽

Liquid Holdup ◽

Two Phase ◽

Frictional Pressure Drop ◽

Viscous Oil ◽

Predicted Values ◽

Superficial Gas Velocity ◽

Churn Flow

Churn flow commonly exists in the pipe of heavy oil, and the characteristics of churn flow should be widely understood. In this paper, we carried out air and viscous oil two-phase flow experiments, and the diameter of the test section is 60 mm. The viscosity range of the oil was 100~480 mPa·s. Based on the measured liquid holdup and pressure drop data of churn flow, it can be concluded that, due to the existence of liquid film backflow, positive and negative frictional pressure drop can be found and the change of frictional pressure drop with the superficial gas velocity is related to superficial liquid velocity. With the increase of viscosity, the change rate of frictional pressure drop increases with the increase of the superficial gas velocity. Combining our previous work and the Taitel model, we proposed a new pressure drop model for viscous oil-air two-phase churn flow in vertical pipes. By comparing the predicted values of existing models with the measured pressure drop data, the proposed model has better performance in predicting the pressure drop.

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