A Comparison of the Breakage Mechanisms for Attrition of Selected Polymers in Pneumatic Transport and Spouted Beds

2009 ◽  
Vol 6 (1) ◽  
Author(s):  
Suma Al-Senawi ◽  
Bashar Hadi ◽  
Cedric Briens ◽  
Jean-Michel Chabagno
Keyword(s):  
Fluidized Bed ◽  
Pilot Plant ◽  
Fluidized Beds ◽  
Pneumatic Transport ◽  
The Other ◽  
Attrition Rate ◽  
Spouted Bed ◽  
Spouted Beds ◽  
Considerable Work ◽  
Product Degradation

Predicting the amount of attrition that will occur in a pneumatic transport system is very important in preventing product degradation. Considerable work has been performed on the mechanisms of attrition in fluidized beds; hence, they are well understood. On the other hand, there are fewer correlations that can be used to predict the attrition rate in pneumatic transport and spouted beds. In this study, polymethyl methacrylates particles were attrited in a pneumatic transport pilot plant and the experimental attrition rate was determined. The same particles were also used in a spouted bed with a sonic attrition jet and the attrition rate was measured. Finally, a fluidized bed correlation was applied to the spouted bed and a model was used to determine whether the attrition mechanism in pneumatic transport can be related to the attrition mechanism in the spouted bed.

Recent Advances of Spout-Fluid Bed: A Review of Fundamentals and Applications

2013 ◽  
Vol 11 (1) ◽  
pp. 243-258 ◽  
Author(s):  
Yingjuan Shao ◽  
Xuejiao Liu ◽  
Wenqi Zhong ◽  
B.-S. Jin ◽  
Mingyao Zhang
Keyword(s):  
Fluidized Beds ◽  
Hydrodynamic Characteristics ◽  
Future Research ◽  
Spouted Bed ◽  
Major Research ◽  
Research Topics ◽  
The Past ◽  
Spouted Beds ◽  
Fluid Bed ◽  
New Applications

Abstract The spout-fluid bed (SFB) is a very successful synthesis of the spouting and fluidization. The hydrodynamics of SFB are more complex than both fluidized beds and spouted beds. Up-to-date information on the fundamentals and applications of SFBs has been briefly presented, based on the limited work reported, in the new spouted bed book edited by Norman Epstein and John R. Grace (Spouted and spout-fluid beds: fundamentals and applications, 2011). In the past three years, nearly 30 papers have been published in international journals. They reported interesting studies on hydrodynamic characteristics, numerical simulations and new applications of SFBs. This article reviews the major research and development on SFB from the year 2010 and recommends further research topics. This review is intended not only as an important supplement to the SFB chapter of the spouted bed book but also helpful guidance for future research.

scholarly journals Coarse-Grain DEM Modelling in Fluidized Bed Simulation: A Review

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 279
Author(s):  
Alberto Di Renzo ◽  
Erasmo Napolitano ◽  
Francesco Di Maio
Keyword(s):  
Fluidized Bed ◽  
Fluidized Beds ◽  
Circulating Fluidized Bed ◽  
Coarse Graining ◽  
Pilot Scale ◽  
Contact Forces ◽  
Coarse Grain ◽  
Fluidized Bed Reactors ◽  
Future Directions ◽  
Spouted Beds

In the last decade, a few of the early attempts to bring CFD-DEM of fluidized beds beyond the limits of small, lab-scale units to larger scale systems have become popular. The simulation capabilities of the Discrete Element Method in multiphase flow and fluidized beds have largely benefitted by the improvements offered by coarse graining approaches. In fact, the number of real particles that can be simulated increases to the point that pilot-scale and some industrially relevant systems become approachable. Methodologically, coarse graining procedures have been introduced by various groups, resting on different physical backgrounds. The present review collects the most relevant contributions, critically proposing them within a unique, consistent framework for the derivations and nomenclature. Scaling for the contact forces, with the linear and Hertz-based approaches, for the hydrodynamic and cohesive forces is illustrated and discussed. The orders of magnitude computational savings are quantified as a function of the coarse graining degree. An overview of the recent applications in bubbling, spouted beds and circulating fluidized bed reactors is presented. Finally, new scaling, recent extensions and promising future directions are discussed in perspective. In addition to providing a compact compendium of the essential aspects, the review aims at stimulating further efforts in this promising field.

Aromatic Transformation in Fluidized Bed Reactors

2008 ◽  
Vol 73 (8-9) ◽  
pp. 1061-1088
Author(s):  
Sule Rabiu ◽  
Sulaiman Al-Khattaf
Keyword(s):  
Fluidized Bed ◽  
The Other ◽  
Fluidized Bed Reactors ◽  
Y Zeolite ◽  
Y Zeolites ◽  
Toluene Disproportionation ◽  
Xylene Isomerization ◽  
Toluene Methylation ◽  
Toluene Conversion ◽  
Medium Acidity

In this work three important aromatic transformations, namely: toluene disproportionation, toluene methylation and m-xylene isomerization, were investigated in a riser simulator which closely mimics the operation of commercial fluidized bed reactors. The transformations were studied over a ZSM-5 based catalyst with medium acidity of 0.23 mmol/g and a series of Y zeolites of acidities between 0.55 and 0.03 mmol/g. For pure toluene feed, it was observed that conversion over the ZSM-5 based catalyst and the weakly acidic Y zeolite (USY-1) was very low. However, with the highly acidic Y zeolite (H-Y), significant toluene conversion was observed with paring reaction more prominent than disproportionation. On the other hand, when toluene was alkylated with methanol, higher toluene conversions were achieved over both the ZSM-5 based and the weakly acidic USY-1 catalysts as compared to when pure toluene feed was used. In addition, p-xylene/o-xylene (P/O) ratios higher than the equilibrium values were obtained in the reaction product over both catalysts. Finally, for m-xylene isomerization it was found that m-xylene conversion increased initially as the acidity of the catalyst increased up to 0.1 mmol/g beyond which any further increase in acidity resulted in a slight decrease in the m-xylene conversion.

Expulsion of particles from a buoyant blob in a fluidized bed

1994 ◽  
Vol 278 ◽  
pp. 63-81 ◽  
Author(s):  
G. K. Batchelor ◽  
J. M. Nitsche
Keyword(s):  
Fluidized Bed ◽  
Fluidized Beds ◽  
Particle Concentration ◽  
Small Concentration ◽  
Numerical Calculations ◽  
Significant Feature ◽  
Average Particle ◽  
Remarkable Property ◽  
Gas Fluidized Beds ◽  
Secondary Instabilities

It is a significant feature of most gas-fluidized beds that they contain rising ‘bubbles’ of almost clear gas. The purpose of this paper is to account plausibly for this remarkable property first by supposing that primary and secondary instabilities of the fluidized bed generate compact regions of above-average or below-average particle concentration, and second by invoking a mechanism for the expulsion of particles from a buoyant compact blob of smaller particle concentration. We postulate that the rising of such an incipient bubble generates a toroidal circulation of the gas in the bubble, roughly like that in a drop of liquid rising through a second liquid of larger density, and that particles in the blob carried round by the fluid move on trajectories which ultimately cross the bubble boundary. Numerical calculations of particle trajectories for practical values of the relevant parameters show that a large percentage of particles, of such small concentration that they move independently, are expelled from a bubble in the time taken by it to rise through a distance of several bubble diameters.Similar calculations for a liquid-fluidized bed show that the expulsion mechanism is much weaker, as a consequence of the larger density and viscosity of a liquid, which is consistent with the absence of observations of relatively empty bubbles in liquid-fluidized beds.It is found to be possible, with the help of the Richardson-Zaki correlation, to adjust the results of these calculations so as to allow approximately for the effect of interaction of particles in a bubble in either a gas- or a liquid-fluidized bed. The interaction of particles at volume fractions of 20 or 30 % lengthens the expulsion times, although without changing the qualitative conclusions.

Simulation of Spouted Bed Using a Eulerian Multiphase Model

2005 ◽  
Vol 498-499 ◽  
pp. 270-277 ◽  
Author(s):  
Claudio Roberto Duarte ◽  
Valéria V. Murata ◽  
Marcos A.S. Barrozo
Keyword(s):  
Control Volume ◽  
Flow Behavior ◽  
Cfd Modeling ◽  
Gas Flows ◽  
Present Calculation ◽  
Multiphase Model ◽  
Spouted Bed ◽  
Particle Coating ◽  
Spouted Beds ◽  
Good Agreement

Spouted bed systems have emerged as very efficient fluid-particle contactors and find many applications in the chemical and biochemical industry. Some important applications of spouted beds include coal combustion, biochemical reactions, drying of solids, drying of solutions and suspensions, granulation, blending, grinding, and particle coating. An extensive overview can be found in Mathur and Epstein[1]. The pattern of solid and gas flows in a spouted bed was numerically simulated using a CFD modeling technique. The Eulerian-Eulerian multifluid modeling approach was applied to predict gas-solid flow behavior. A commercially available, control-volume-based code FLUENT 6.1 was chosen to carry out the computer simulations. In order to reduce computational times and required system resources, the 2D axisymmetric segregated solver was chosen. The typical flow pattern of the spouted bed was obtained in the present calculation. The simulated velocity and voidage profiles presented a good agreement qualitative and quantitative with the experimental results obtained by He et al. [4].

scholarly journals Study on Fluidization Characteristics of Magnetically Fluidized Beds for Microfine Particles

Minerals ◽  
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.

scholarly journals Influence of inlet air distributor geometry on the fluid dynamics of conical spouted beds: A CFD study

2018 ◽  
Vol 24 (4) ◽  
pp. 369-378 ◽  
Author(s):  
J.N.M. Batista ◽  
R.C. Brito ◽  
R. Béttega
Keyword(s):  
Fluid Dynamics ◽  
Cfd Simulation ◽  
Low Cost ◽  
Scale Up ◽  
Straight Tube ◽  
Spouted Bed ◽  
Bed Height ◽  
Spouted Beds ◽  
Wide Range ◽  
Solid Dynamics

The spouted bed presents limitations in terms of scale-up. Furthermore, its stability depends on its geometry as well as the properties of the fluid and solid phases. CFD provides an important tool to improve understanding of these aspects, enabling a wide range of information to be obtained rapidly and at low cost. In this work, CFD simulation was used to evaluate the effects of different inlet air distributors (Venturi and straight tube) and the effects of static bed height on the fluid and solid dynamics of a conical spouted bed. Simulations were performed using the two-dimensional Euler-Euler approach. In order to evaluate the fluid dynamics model, static pressure data obtained by simulation were compared with experimental data obtained with the Venturi distributor. The fluid and solid dynamics of the conical spouted bed were obtained by CFD simulation. The results showed that the pressure drop was lower for the straight tube air distributor, while the Venturi air distributor provided higher stability and a more homogenous air distribution at the bed entrance.

scholarly journals Heat transfer to a moving wire immersed in a gas fluidized bed furnace

2021 ◽  
Author(s):  
Antonio Tannas
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Steel Wire ◽  
Transfer Rates ◽  
New Correlation ◽  
Bed Temperature ◽  
Molten Lead ◽  
The Difference ◽  
Considerable Work ◽  
Work Done

In order to replace hazardous molten lead baths in the heat treatment of carbon steel wire with environmentally friendly fluidized bed furnaces a better understanding is needed of their heat transfer rates. There has been considerable work done in examining heat transfer rates to large cylinders immersed in fluidized beds, and some on wire sized ones as well, but all previous studies have been conducted on static cylinders. In order to gain a deeper understanding of heat transfer rates to a moving wire immersed in a fluidized bed furnace an apparatus has been constructed to move a wire through a fluidized bed. The heat transfer rates were calculated using the difference in inlet and outlet temperatures, wire speed and the bed temperature. As predicted, correlations for static wire were found to under-predict heat transfer rates at higher wire speeds, so a new correlation was developed by modifying an existing one.

Scale Effects on Fluidized Bed Hydrodynamics

2005 ◽  
Vol 3 (1) ◽  
Author(s):  
Rachid Mabrouk ◽  
Ramin Radmanesh ◽  
Jamal Chaouki ◽  
Christophe Guy
Keyword(s):  
Fluidized Bed ◽  
Particle Tracking ◽  
Fluidized Beds ◽  
Fiber Optic ◽  
Scale Effects ◽  
Scale Up ◽  
Radial Profile ◽  
Radioactive Particle Tracking ◽  
Industrial History ◽  
Radioactive Particle

Industrial history is full of events related to scale-up challenges. Failure at the scale-up stage is no longer surprising. Engineers and scientists have been trying to gather all the key parameters for decades, but, unfortunately, there are still no exact and well-established rules ensuring an accurate transition from one scale to another. Even the minimum lab-scale fluidized bed is still undefined.In this work, the effect of bed diameter on gas-solid behavior is investigated in three fluidized beds, 152mm, 78mm, and 50mm in diameter, in which the conventional scale-up rules are respected. The experiments were carried out using sand and alumina particles.The results were obtained and confirmed using fiber optic techniques and radioactive particle tracking, respectively. The results show that radial solid hold-up behavior on a small bed diameter scale is completely different from that on the intermediate bed diameter scale. The radial profile of solid hold-up on a small and very small bed diameter indicates an increase from a low value near the wall to a high value at the center at different heights from the distributor. By contrast, the opposite profile is observed on the intermediate bed diameter, similar to what is usually reported in the literature.

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