The minimum fluidisation velocity, bed expansion and pressure-drop profile of binary particle mixtures

1979 ◽  
Vol 22 (2) ◽  
pp. 255-269 ◽  
Author(s):  
S. Chiba ◽  
T. Chiba ◽  
A.W. Nienow ◽  
H. Kobayashi
Keyword(s):  
Pressure Drop ◽  
Bed Expansion

scholarly journals Modelling of a Heated Gas-solid Fluidised Bed using Eulerian Based Models

R&D Journal ◽  
2021 ◽  
Author(s):  
A. Potgieter ◽  
M. Bhamjee ◽  
S. Kruger
Keyword(s):  
Pressure Drop ◽  
Fixed Bed ◽  
Fluidised Bed ◽  
Bubble Interactions ◽  
Bed Height ◽  
Chamber Height ◽  
Model Predictions ◽  
Computational Fluid Dynamics Cfd ◽  
Fluidised Beds ◽  
Bed Expansion

ABSTRACT An Eulerian-Eulerian granular model was used to simulate the flow and heat transfer through a heatedgassolid fluidised bed. The primary objective of the study was to determine whether the Eulerian-Eulerian granular model adequately predicts the chamber pressure drop, temperature, and bed expansion through the bed. The model predictions were assessed and validated for various flow-regimes, namely the fixed-bed, smooth, bubbling fluidisation, and the maximum fluidisation regimes. This was done on an experimental scale heated gas-solid fluidised bed. However, the results are generalisable for heated gas-solid fluidised beds when the flow is laminar. Numerical models were created using Computational Fluid Dynamics (CFD). The CFD-model predictions were investigated, analysed, and compared to experimental results. Basic experiments were carried out to obtain varying hydrodynamic characteristics. The results showed a slight overprediction of pressure drop and bed expansion, however, the results were still in close agreement with the experiment. In contrast, underprediction of chamber temperatures were obtained. Based on the results of this study, it is recommended that the Eulerian model be used to predict dynamic flow behaviour. Before minimum fluidisation, when in a fixed bed regime, pressure drop in the chamber increases with no increase in bed height. No visible bubbles were present in the fixed bed regime. When fluidisation has been reached, the bed height rises whereas the pressure drop tends to a constant value. Bubble size increases with chamber height and increased superficial velocities. Bubble speed increased with increased chamber height. With increased superficial velocity, the chamber temperatures increase to a maximum temperature of326.65 K with an initial heating element temperature of373.15 K. However, when excessive heat is present in the gas-solid fluidised bed, other methods that sufficiently incorporate particle-particle interactions and bubble-bubble interactions, are recommended. An investigation should be lent to bubble-bubble interactions in the fluidised beds with relation to heat transfer. Additional keywords: Heated fluidised bed, computational fluid dynamics, CFD, Eulerian, granular, fluidisation, gas-solid

Gas Holdup Characteristics in a Tapered Bubble Column

2003 ◽  
Vol 1 (1) ◽  
Author(s):  
Kai Zhang ◽  
Yulong Zhao ◽  
Bijiang Zhang
Keyword(s):  
Pressure Drop ◽  
Bubble Column ◽  
Particle Diameter ◽  
Liquid System ◽  
Gas Holdup ◽  
Internal Diameter ◽  
Slurry Concentration ◽  
The Difference ◽  
Bed Expansion ◽  
Solid System

Gas holdup characteristics were explored experimentally in a tapered bubble column of 3.00m height. The internal diameter increased from 0.10 m at the bottom to 0.20 m at the top. Two gas holdup characteristic parameters investigated were local gas holdup and overall gas holdup. Local gas holdup was measured by pressure drop method whilst overall gas holdup was measured by both pressure drop and bed expansion techniques. Axial gas holdup profile decreased from the bottom to the top in the range of the experiments. Overall gas holdup reached a maximum in transitional regime for either the gas-liquid system or the gas-liquid-solid system with low slurry concentration, but increased monotonically for gas-liquid-solid system with high slurry concentration. Overall gas holdup decreased with increasing static slurry height or solid concentration. The effect of particle diameter on gas holdup was too insignificant to be considered. Experiments were carried out in a cylindrical column to compare the difference between cylindrical and tapered bubble columns. Moreover, an empirical correlation was presented to estimate overall gas holdup in the tapered slurry bubble column (TSBC).

scholarly journals Fluidization Dynamics of Hydrophobic Nanosilica with Velocity Step Changes

2020 ◽  
Vol 10 (22) ◽  
pp. 8127
Author(s):  
Ebrahim H. Al-Ghurabi ◽  
Mohammad Asif ◽  
Nadavala Siva Kumar ◽  
Sher Afghan Khan
Keyword(s):  
Pressure Drop ◽  
Fluidized Bed ◽  
Large Scale ◽  
Gas Flow ◽  
Temporal Frequency ◽  
Sampling Rate ◽  
Intimate Contact ◽  
Frequency Domains ◽  
Bulk Processing ◽  
Bed Expansion

Nanosilica is widely used in various applications, with its market expected to grow over USD 5 billion by 2025. The fluidized bed technology, owing to its intimate contact and efficient mixing of phases, is ideally suited for the large scale processing of powders. However, the bulk processing and dispersion of ultrafine nanosilica using the fluidized bed technology are critically affected by the interparticle forces, such that the hydrophilic nanosilica shows agglomerate bubbling fluidization (ABF), while the hydrophobic nanosilica undergoes agglomerate particulate fluidization (APF). This study carried out a detailed investigation into the fluidization hydrodynamic of the hydrophobic nanosilica by monitoring the region-wise dynamics of the fluidized bed subjected to a regular step change of fixed duration in the gas velocity. The gas flow was controlled using a mass controller operated with an analog output signal from a data acquisition system. The analog input data were acquired at the sampling rate of 100 Hz and analyzed in both time and temporal frequency domains. The effect of velocity transients on the bed dynamics was quickly mitigated and appeared as lower frequency events, especially in regions away from the distributor. Despite the apparent particulate nature of the fluidization, strong hysteresis was observed in both pressure drop and bed expansion. Moreover, the fully fluidized bed’s pressure drop was less than 75% of the theoretical value even though the bed appeared to free from non-homogeneities. Key fluidization parameters, e.g., minimum fluidization velocity (Umf) and the agglomerate size, were evaluated, which can be readily used in the large scale processing of nanosilica powders using fluidized bed technology.

scholarly journals Hydrodynamics of Turbulent Bed Contactor with Non Newtonian Liquids

2021 ◽  
Author(s):  
Hadil Abukhalifeh
Keyword(s):  
Pressure Drop ◽  
Aqueous Solutions ◽  
Methyl Cellulose ◽  
Gas Holdup ◽  
Newtonian Liquid ◽  
Hydrodynamic Characteristics ◽  
Liquid Holdup ◽  
Viscous Liquids ◽  
Newtonian Liquids ◽  
Bed Expansion

Little information is available in literature in terms of the hydrodynamic characteristics in a turbulent bed contractor [sic] (TBC) with viscous liquids. In this study, the hydrodynamic characteristics in three-phase turbulent bed contactor with counter current flow of air and non-Newtonian liquid was studied and compared with that of Newtonian liquid under consistent conditions. Aqueous solutions of carboxy methyl cellulose (CMC) with apparent viscosities ranged between 5 to 25 cP were used as non-Newtonian liquid. The hydrodynamic parameters iinvestigatedwere: bed pressure drop, minimum fluidization velocity, liquid holdup, bed expansion, and gas holdup. The effect of rheological properties of the CMC aqueous solutions and operating parameters on hydrodynamic characteristics of the TBC were examined. Results showed that increasing CMC concentration increased the net pressure drop across the bed and the liquid holdup, while the gas holdup and bed expansion decreased. At that quoted apparent viscosity range, aqueous solutions of CMC behaved as Newtonian viscous liquids in the TBC.

scholarly journals Hydrodynamics of Turbulent Bed Contactor with Non Newtonian Liquids

2021 ◽  
Author(s):  
Hadil Abukhalifeh
Keyword(s):  
Pressure Drop ◽  
Aqueous Solutions ◽  
Methyl Cellulose ◽  
Gas Holdup ◽  
Newtonian Liquid ◽  
Hydrodynamic Characteristics ◽  
Liquid Holdup ◽  
Viscous Liquids ◽  
Newtonian Liquids ◽  
Bed Expansion

Little information is available in literature in terms of the hydrodynamic characteristics in a turbulent bed contractor [sic] (TBC) with viscous liquids. In this study, the hydrodynamic characteristics in three-phase turbulent bed contactor with counter current flow of air and non-Newtonian liquid was studied and compared with that of Newtonian liquid under consistent conditions. Aqueous solutions of carboxy methyl cellulose (CMC) with apparent viscosities ranged between 5 to 25 cP were used as non-Newtonian liquid. The hydrodynamic parameters iinvestigatedwere: bed pressure drop, minimum fluidization velocity, liquid holdup, bed expansion, and gas holdup. The effect of rheological properties of the CMC aqueous solutions and operating parameters on hydrodynamic characteristics of the TBC were examined. Results showed that increasing CMC concentration increased the net pressure drop across the bed and the liquid holdup, while the gas holdup and bed expansion decreased. At that quoted apparent viscosity range, aqueous solutions of CMC behaved as Newtonian viscous liquids in the TBC.

Pressure drop, bed expansion and liquid holdup in a three phase spouted bed contactor

1974 ◽  
Vol 52 (2) ◽  
pp. 180-184 ◽  
Author(s):  
D. V. Vukov ÍC ◽  
F. K. Zdanski ◽  
G. V. Vunjak ◽  
Ž. B. Grbavčić ◽  
H. Littman
Keyword(s):  
Pressure Drop ◽  
Spouted Bed ◽  
Liquid Holdup ◽  
Three Phase ◽  
Bed Expansion

Effects of Different Granular Viscosity Models on the Bubbling Fluidized Bed - A Numerical Approach

2013 ◽  
Vol 393 ◽  
pp. 857-862
Author(s):  
M.I. Hilmee ◽  
Mohan Sinnathambi Chandra ◽  
Saravanan Karuppanan ◽  
M. Fadhil ◽  
Mohd Rizal Lias
Keyword(s):  
Pressure Drop ◽  
Fluidized Bed ◽  
Granular Flow ◽  
Simulation Models ◽  
Numerical Approach ◽  
Ansys Fluent ◽  
Viscosity Models ◽  
Simulation Based ◽  
Bubbling Fluidized Bed ◽  
Bed Expansion

Kinetic Theory of Granular Flow (KTGF) has been successfully incorporated and widely implemented in the Eulerian simulation models in many multiphase cases. The KTGF theory involves many parameters and is applied in the multiphase simulation for the purpose of hydrodynamic properties modeling of the granular phase. This paper is focused on granular viscosity which is a parameter in the KTGF that incorporates three different viscosities arising from the inter-phase and intra phases interaction in a bubbling fluidized bed (BFB). The 2D BFB model of 0.2 m width and 0.8 m length having a 13-hole orifice plate has been modeled for this purpose. The model was constructed using Gambit software version 2.4.6 and then simulated using ANSYS Fluent version 14. Two models of granular viscosity, namely Syamlal-Obrien model and Gidaspow model, were compared based on its effect to the pressure drop and bed expansion of the BFB. The results depicted that the simulation based on Syamlal-Obrien model tends to produce larger bubbles and contributing to a higher pressure drop across the distributor plate as compared to the Gidaspow model.

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