Effect of Various Parameters on the Solids Holdup in a Liquid-Solid Circulating Fluidized Bed

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Natarajan Palani ◽  
Velraj Ramalingam ◽  
Seeniraj R.V.
Keyword(s):  
Experimental Data ◽  
Fluidized Bed ◽  
Flow Rate ◽  
Liquid Flow ◽  
Circulating Fluidized Bed ◽  
Liquid Flow Rate ◽  
Tap Water ◽  
Solid Particles ◽  
Circulation Rate ◽  
Solids Holdup

A liquid-solid circulating fluidized bed (LSCFB) is operated at high liquid velocity, where particle entrainment is highly significant and between the conventional liquid fluidized bed and the dilute phase liquid transport regimes. In the present work, systematic experiments were carried out in a 0.094 m ID and 2.4 m height laboratory-scale liquid-solid circulating fluidized bed apparatus by using various solid particles and tap water as a fluidizing medium to study the hydrodynamics (axial solids holdup and solids circulation rate). The effects of operating parameters, i.e., primary liquid flow rate in the riser (jf), auxiliary liquid flow rate (ja), total liquid flow rate (jl), particle density (?s), particle diameter (dp) and solids feed pipe diameter (do) on the axial solids holdup distribution were analyzed from the experimental data. Finally, a correlation was developed from the experimental data to estimate average solid holdup in the riser, and it was compared with present experimental and available data in the literature. They agree well with a maximum root-mean-square deviation of 9.12 %.

Predicting bed dynamics in three-phase, fluidized-bed biofilm reactors

1994 ◽  
Vol 29 (10-11) ◽  
pp. 231-241 ◽  
Author(s):  
H. T. Chang ◽  
B. E. Rittmann
Keyword(s):  
Fluidized Bed ◽  
Flow Rate ◽  
Liquid Flow ◽  
Gas Flow ◽  
Liquid Flow Rate ◽  
Gas Flow Rate ◽  
Biofilm Growth ◽  
Biofilm Thickness ◽  
Three Phase ◽  
Proper Design

This paper presents a unified model that inter-relates gas flow rate, liquid flow rate, and hold-ups of each of the liquid, gas, and solid phases in three-phase, fluidized-bed biofilm (TPFBB) process. It describes how carrier properties, biofilm properties, and gas and liquid flow velocities control the system dynamics, which ultimately will affect the density, thickness, and distribution of the biofilm. The paper describes the development of the mathematical model to correlate the effects of gas flow rate, liquid flow rate, solid concentration, and biofilm thickness and density. This knowledge is critically needed in light of the use of TPFBB processes in treating industrial wastewater, which often has high substrate concentration. For example, the proper design of the TPFBB process requires mathematical description of the cause-effect relationship between biofilm growth and fluidization.

Prediction of Solid Recirculation Rate and Solid Volume Fraction in an Internally Circulating Fluidized Bed

2015 ◽  
Vol 12 (04) ◽  
pp. 1540005 ◽  
Author(s):  
Ravi Gujjula ◽  
Narasimha Mangadoddy
Keyword(s):  
Experimental Data ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Volume Fraction ◽  
Draft Tube ◽  
Numerical Study ◽  
Solid Particles ◽  
Granular Temperature ◽  
Solids Concentration ◽  
Drag Laws

This paper presents a numerical study of gas and solid flow in an internally circulating fluidized bed (ICFB). Two-fluid Eulerian model with kinetic theory of granular flow option for solid phase stress closure and various drag laws were used to predict the hydrodynamic behavior of ICFB. 2D and 3D geometries were used to run the simulations. The 2D simulation results by various drag laws show that the Arastoopour and Gibilaro drag models able to predict the fluidization dynamics in terms of flow patterns, void fractions and axial velocity fields close to the experimental data. The effect of superficial gas velocity, presence of draft tube on solid hold-up distribution, solid circulation pattern, and variations in gas bypassing fraction for the 3D ICFB are investigated. The mechanism governing the solid circulation and solids concentration in an ICFB has been explained based on gas and solid dynamics obtained from the simulations. Predicted total granular temperature distributions in the draft tube and annular zones qualitatively agree with experimental data. The total granular temperature tends to increase with increasing solids concentration in the dilute region (ε < 0.1) and decreases with an increase of solids concentration in the dense region (ε > 0.1). In the dense zone, the decreasing trend in the granular temperature is mainly due to the reduction of the mean free path of the solid particles.

scholarly journals Absorption in a three-phase fluidized bed II: Mass transfer investigations

2003 ◽  
Vol 57 (7-8) ◽  
pp. 330-334
Author(s):  
Srdjan Pejanovic ◽  
Radmila Garic-Grulovic ◽  
Predrag Bozalo
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Fluidized Bed ◽  
Flow Rate ◽  
Liquid Flow ◽  
Liquid Flow Rate ◽  
Interfacial Area ◽  
Transfer Coefficients ◽  
Three Phase

The absorption of carbon dioxide in aqueous diethanolamine solutions was carried out in a three-phase fluidized bed with inert spherical packing. The rate of absorption was calculated on the basis of measuring the concentration change in the liquid phase on-line by a conductivity probe. It was shown that the Danckwerts plot method might be successfully used to simultaneously determine the effective interfacial area and both the gas and liquid-side mass transfer coefficients. While the gas-side mass transfer coefficient is independent of the liquid flow rate, the effective interfacial area and liquid-side mass transfer coefficient increase with increasing liquid flow rate.

scholarly journals Study on the Flow Characteristics of Desulfurization Ash Fine Particles in a Circulating Fluidized Bed

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1343
Author(s):  
Xiao Yang ◽  
Chengxiu Wang ◽  
Xingying Lan ◽  
Jinsen Gao
Keyword(s):  
Fluidized Bed ◽  
Flue Gas ◽  
Circulating Fluidized Bed ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Current Status ◽  
Circulation Rate ◽  
Wall Region ◽  
Gas Treatment ◽  
Solids Holdup

In view of the current status of catalytic cracking flue gas treatment, it is necessary to study the flow environment of desulfurization ash particles, which are a type of Geldart C particle, in a circulating fluidized bed (CFB) for semi-dry flue gas desulphurization using CFB technology. This study investigated the flow characteristics of desulphurization ash particles in a riser with an inner diameter of 70 mm and a height of 12.6 m, at a gas velocity of 4–7 m/s and a solids circulation rate of 15–45 kg/m2·s. The solids holdup in the axial distribution is relatively high near the bottom of the riser, and gradually decreases as the riser height increases, with a stable value from the middle to the top of the riser. In the radial distribution, the solids holdup of desulfurization ash particles is low in the center and high in the wall region. Within the above operating conditions, the solids holdup ranges from 0.008 to 0.025. The particle-based Archimedes number has a linear relationship with the solids holdup at all operating conditions.

scholarly journals Hydrodynamic Flow Characteristics in an Internally Circulating Fluidized Bed Gasifier

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
J. P. Simanjuntak ◽  
K. A. Al-attab ◽  
Z. A. Zainal
Keyword(s):  
Fluidized Bed ◽  
Flow Rate ◽  
Circulating Fluidized Bed ◽  
Draft Tube ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Hydrodynamic Flow ◽  
Orifice Diameter ◽  
Circulation Rate ◽  
Cfd Models

In this paper, the hydrodynamic flow inside an internally circulating fluidized bed (ICFBG) was characterized using experimental and three-dimensional computational fluid dynamics (CFD) models. Eulerian-Eulerian model (EEM) incorporating the kinetic theory of granular flow was implemented in order to simulate the gas–solid flow. A full-scale plexiglass cold flow experimental model was built to verify simulation results prior to the fabrication of the gasifier. Six parameters were manipulated to achieve the optimum design geometry: fluidization flow rate of the draft tube (Qdt), aeration flow rate of the annulus (Qan), initial bed static height (Hbs), draft tube height (Hdt), draft tube diameter (Ddt), and orifice diameter (Dor). The investigated parameters showed strong effect on the particle flow characteristics in terms of the pressure difference (ΔP) and solid circulation rate (Gs). The predicted results by simulation for the optimum case were in close agreement with experimental measurements with about 5% deviation. The results show that the ICFBG operated stably with the maximum Gs value of 86.6 kg/h at Qdt of 350 LPM, Qan of 150 LPM, Hbs of 280 mm, Hdt of 320 mm, Ddt of 100 mm, and Dor of 20 mm.

A Model to Predict Radial Solids Holdup and Liquid Velocity Distributions in Liquid-Solid Circulating Fluidized Bed

2007 ◽  
Vol 2 (3) ◽  
Author(s):  
Natarajan Palani ◽  
Velraj R. ◽  
Seeniraj R.V.
Keyword(s):  
Experimental Data ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Liquid Velocity ◽  
Two Phase ◽  
Cross Sectional ◽  
Operating Variables ◽  
Solids Holdup ◽  
Cross Sectional Average ◽  
Good Agreement

A general expression which is useful for predicting the radial distributions or for analyzing and interpreting experimental data is derived for a liquid-solid circulating fluidized bed. The effect of both the radial liquid velocity and solids holdup distributions are taken into account in the analysis. Both effects are analyzed and are related to the operating variables of superficial liquid velocity, jl, superficial solids velocity, js, and cross-sectional average solids holdup. The results predicted by the analysis are compared with the experimental data obtained for various two-phase flow regimes, when different solids and bed dimensions are applied. The model predictions show good agreements with the experimental data and reasonable trends when different solids and bed dimensions are applied. Stronger non-uniformities in flow structures are found in larger size particles systems, with larger solids density and/or larger diameter columns. Radial solids holdup distribution is related with the cross-sectional average solids holdup. Good agreement with data and reasonable trends are observed.

Evaluating Liquid-Cooled Heat Sink Resistance Data for Electronic Applications

2012 ◽  
Author(s):  
Randall D. Manteufel
Keyword(s):  
Experimental Data ◽  
Thermal Resistance ◽  
Flow Rate ◽  
Liquid Flow ◽  
Liquid Flow Rate ◽  
Experimental Studies ◽  
Heat Sinks ◽  
Model Parameters ◽  
Relative Contribution ◽  
Overall Resistance

A number of experimental studies have been published for single-phase liquid cooling for electronic heat sources. These include flow though various sized channels and configurations. Results are expressed using a thermal resistance as a function of liquid volumetric (or mass) flow rate. This paper discusses the regression of experimental data. Two simple thermal resistance models are evaluated, each having a combination of conduction and convection components. The models are applicable to a wide set of data. A preferred model is identified having three parameters: (1) overall resistance at a nominal flow, (2) percentage of resistance due to conduction at the nominal flow, and (3) convective exponent for the liquid flow rate. The preferred model has lower correlation between its parameters and reproduces the trends in experimental data. The model is used to quantify the relative contribution of the convective and conductive sources of thermal resistance. It is also useful in design to evaluate the effectiveness of increasing the liquid flow rate which can be accomplished with increased pressure drop and pumping costs. The best-fit estimates and their approximate 95% confidence intervals are calculated using experimental data. A few experimental results yield discrepant values for the model parameters. In some cases the rate of reduction of the thermal resistance with increasing flow rate appears beyond what can be reasonably expected. Sources of discrepant results are discussed. The results of the paper are helpful in evaluating experimental data and guiding the design of liquid-cooled heat sinks.

Modeling Drying Kinetics of Mustard in Fluidized Bed

2008 ◽  
Vol 4 (3) ◽  
Author(s):  
Chandrasekar Srinivasakannan
Keyword(s):  
Experimental Data ◽  
Fluidized Bed ◽  
Flow Rate ◽  
Total Duration ◽  
Effective Diffusivity ◽  
Model Parameters ◽  
Drying Rate ◽  
Solids Holdup ◽  
Maximum Root ◽  
Kinetics Of

Mustard (Brassica juncea), one of the popular oil seeds, is investigated for drying in Batch fluidized beds. Experiments were conducted to assess the kinetics of drying for the variation in the inlet air temperature, the inlet air flow rate and the solids holdup in the fluidized bed. The drying rate was found to increase significantly with increase in temperature and with flow rate of the heating medium, while decrease with increase in solids holdup. The duration of constant rate period was found to be insignificant, considering the total duration of drying. The drying rate was compared with various exponential time decay models and the model parameters were evaluated. The page model was found to match the experimental data very closely with the maximum root mean square error (RMSE) of less the 2.0%. The experimental data were also modeled using Fick's diffusion equation and the effective diffusivity coefficients was found to be within 1.69*10-11 to 3.26*10-11m2/s for the range of experimental data covered in the present study with RMSE less than 4%.

Utilization of Waste of Enzymes Biomass as Biosorbent for the Removal of Dyes from Aqueous Solution in Batch and Fluidized Bed Column

2020 ◽  
Vol 71 (1) ◽  
pp. 1-12
Author(s):  
Salman H. Abbas ◽  
Younis M. Younis ◽  
Mohammed K. Hussain ◽  
Firas Hashim Kamar ◽  
Gheorghe Nechifor ◽  
...  
Keyword(s):  
Experimental Data ◽  
Aqueous Solution ◽  
Particle Size ◽  
Adsorption Capacity ◽  
Fluidized Bed ◽  
Flow Rate ◽  
Fungal Biomass ◽  
Solution Flow Rate ◽  
Maximum Adsorption Capacity ◽  
Solution Flow

The biosorption performance of both batch and liquid-solid fluidized bed operations of dead fungal biomass type (Agaricusbisporus ) for removal of methylene blue from aqueous solution was investigated. In batch system, the adsorption capacity and removal efficiency of dead fungal biomass were evaluated. In fluidized bed system, the experiments were conducted to study the effects of important parameters such as particle size (701-1400�m), initial dye concentration(10-100 mg/L), bed depth (5-15 cm) and solution flow rate (5-20 ml/min) on breakthrough curves. In batch method, the experimental data was modeled using several models (Langmuir,Freundlich, Temkin and Dubinin-Radushkviechmodels) to study equilibrium isotherms, the experimental data followed Langmuir model and the results showed that the maximum adsorption capacity obtained was (28.90, 24.15, 21.23 mg/g) at mean particle size (0.786, 0.935, 1.280 mm) respectively. In Fluidized-bed method, the results show that the total ion uptake and the overall capacity will be decreased with increasing flow rate and increased with increasing initial concentrations, bed depth and decreasing particle size.

Absorption of oxygen into solutions of polymers

1986 ◽  
Vol 51 (10) ◽  
pp. 2127-2134 ◽  
Author(s):  
František Potůček ◽  
Jiří Stejskal
Keyword(s):  
Mass Transfer ◽  
Aqueous Solutions ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Liquid Flow ◽  
Flow Curve ◽  
Liquid Flow Rate ◽  
Polymer Concentration ◽  
Newtonian Liquids

Absorption of oxygen into water and aqueous solutions of poly(acrylamides) was studied in an absorber with a wetted sphere. The effects of changes in the liquid flow rate and the polymer concentration on the liquid side mass transfer coefficient were examined. The results are expressed by correlations between dimensionless criteria modified for non-Newtonian liquids whose flow curve can be described by the Ostwald-de Waele model.

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