Bubble Column Reactor (bubble + column_reactor)

Distribution by Scientific Domains
Chemistry93%

Kinds of Bubble Column Reactor

  • slurry bubble column reactor
    		•

    Selected Abstracts

    A Study on Hydrodynamics and Heat Transfer in a Bubble Column Reactor with Yeast and Bacterial Cell Suspensions

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2005
    Nigar Kantarci
    Abstract Hydrodynamics and heat transfer experiments were carried out in a slurry bubble column with air-water-yeast cells and air-water-bacteria cells systems to investigate gas hold-up, bubble characteristics and heat transfer coefficients with cell concentrations of 0.1% w/w and 0.4% w/w and superficial gas velocity up to 0.20 m/s. The gas hold-ups and heat transfer coefficients were found to increase with increasing gas velocity and cell concentration. The heat transfer coefficients were higher at the centre of the column as compared to the near wall region. The development of empirical correlations to predict the heat transfer coefficient in two- and three-phase systems was carried out with ±15% confidence interval at most. On a réalisé des expériences d'hydrodynamique et de transfert de chaleur dans une colonne triphasique gaz-liquide-solide avec des systèmes de cellules air-eau-levure et de cellules air-eau-bactéries afin d'étudier la rétention de gaz, les caractéristiques des bulles et les coefficients de transfert de chaleur avec des concentrations de cellules de 0,1 % en poids et 0,4 % en poids et des vitesses de gaz superficielles jusqu'à 0,20 m/s. On a trouvé que les rétentions de gaz et les coefficients de transfert de chaleur augmentaient avec la vitesse de gaz et la concentration en cellules. Les coefficients de transfert de chaleur sont plus grands au centre de la colonne que dans la région proche de la paroi. Des corrélations empiriques pour prédire le coefficient de transfert de chaleur dans des systèmes bi et triphasiques ont été établies avec un écart de confiance inférieur ou égal à ± 15%. [source]

    CFD Modeling of a Bubble Column Reactor Carrying out a Consecutive A , B , C Reaction

    CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2004
    J.M. van Baten
    Abstract In this paper, we develop a CFD model for describing a bubble column reactor for carrying out a consecutive first-order reaction sequence A , B , C. Three reactor configurations, all operating in the homogeneous bubbly regime, were investigated: (I) column diameter DT = 0.1 m, column height HT = 1.1 m, (II) DT = 0.1 m, HT = 2 m, and (III) DT = 1 m, HT = 5 m. Eulerian simulations were carried out for superficial gas velocities UG in the range of 0.005,0.04 m/s, assuming cylindrical axisymmetry. Additionally, for configurations I and III fully three-dimensional transient simulations were carried out for checking the assumption of cylindrical axisymmetry. For the 0.1 m diameter column (configuration I), 2-D axisymmetric and 3-D transient simulations yield nearly the same results for gas holdup ,G, centerline liquid velocity VL(0), conversion of A, ,A, and selectivity to B, SB. In sharp contrast, for the 1 m diameter column (configuration III), there are significant differences in the CFD predictions of ,G, VL(0), ,A, and SB using 2-D and 3-D simulations; the 2-D strategies tend to exaggerate VL(0), and underpredict ,G, ,A, and SB. The transient 3-D simulation results appear to be more realistic. The CFD simulation results for ,A and SB are also compared with a simple analytic model, often employed in practice, in which the gas phase is assumed to be in plug flow and the liquid phase is well mixed. For the smaller diameter columns (configurations I and II) the CFD simulation results for ,A are in excellent agreement with the analytic model, but for the larger diameter column the analytic model is somewhat optimistic. There are two reasons for this deviation. Firstly, the gas phase is not in perfect plug flow and secondly, the liquid phase is not perfectly mixed. The computational results obtained in this paper demonstrate the power of CFD for predicting the performance of bubble column reactors. Of particular use is the ability of CFD to describe scale effects. [source]

    Simulations of Bubble Column Reactors Using a Volume of Fluid Approach: Effect of Air Distributor

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2007
    M. Abid Akhtar
    Abstract Two- and three-dimensional numerical simulations have been performed on a laboratory scale bubble column reactor using a volume-of-fluid approach. The effect of hole-size and superficial gas velocity on the bubble size distribution and their trajectories has been investigated on a 20 cm diameter and 1 m high cylindrical reactor. All simulations were performed in a transient manner using a FLUENT solver. Surface tension between two phases has been modelled as a body force with a constant value. Turbulence was modelled using the k-, turbulence approach. A comparison between simulation predictions and the reported experimental studies has shown a good agreement. On a effectué des simulations numériques bi et tridimensionnelles dans un réacteur à colonne à bulles à l'échelle de laboratoire à l'aide d'une approche volume-de-fluide. L'effet de la taille du trou et de la vitesse de gaz superficielle sur la distribution de tailles des bulles et leurs trajectoires a été étudié dans un réacteur cylindrique de 20 cm de diamètre et de 1 m de hauteur. Toutes les simulations ont été réalisées selon un mode transitoire à l'aide du logiciel FLUENT. La tension de surface entre deux phases a été modélisée comme une force volumique avec une valeur constante. La turbulence a été modélisée par la méthode de turbulence k-,. Une comparaison entre les prédictions des simulations et les études expérimentales mentionnées montre un bon accord. [source]

    Efficiency of non-reactive isothermal bubble column based on mass transfer

    ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2008
    Subrata Kumar Majumder Assistant Professor
    Abstract Bubble column reactor as a gas,liquid contactor is extensively used in the chemical and biochemical industries. Mass transfer coefficients governing the transport processes in bubble contactors are a growing concern in chemical and biotechnological processes whose rates are often limited by the mass transfer rate. The influences of different physical, dynamic and geometric variables affect the efficiency characterization of the equipment which are involved in gas/liquid mass transfer processes. This characterization has great importance to optimize the process plant design. In this article, efficiency of two-phase mass transfer in bubble column reactors has been analyzed based on dynamic, geometric and physical variables of the system. An empirical correlation for mass transfer efficiency has also been developed in terms of those variables. The present analysis on the gas,liquid mass transfer efficiency of bubble column may give insight into a further understanding and modeling of multiphase reactors in industrial applications. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

    Enhanced production of lovastatin in a bubble column by Aspergillus terreus using a two-stage feeding strategy

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2007
    EM Rodríguez Porcel
    Abstract A two-stage feeding strategy is shown to improve the rate of production of lovastatin by Aspergillus terreus when compared with conventional batch fermentation. The feeding strategy consisted of an initial batch/fed-batch phase and a semi-continuous culture dilution phase with retention of pelleted biomass in a slurry bubble column reactor. The batch phase served only to build up the biomass for producing lovastatin, a secondary metabolite that inhibits its own synthesis in the producing microfungus. The semi-continuous dilution phase provided nutrients to sustain the fungus, but prevented biomass growth by limiting the supply of essential nitrogen. (Synthesis of lovastatin does not require nitrogen.) The preferred pelleted growth morphology that favors lovastatin synthesis was readily obtained and maintained in the 20 L bubble column used. In contrast, a stirred tank fermentation had a substantially lower production of lovastatin because mechanical agitation damaged the fungal pellets. The two-stage feeding method increased lovastatin production rate by more than 50% in comparison with the conventional batch operation. Rheological data for the fungal broth are presented. Copyright © 2007 Society of Chemical Industry [source]

    Simulation of a slurry-bubble column reactor for Fischer-Tropsch synthesis using single-event microkinetics

    AICHE JOURNAL, Issue 8 2009
    Gisela Lozano-Blanco
    Abstract A single-event microkinetic model for Fischer-Tropsch synthesis including the water-gas shift reaction has been implemented in a one-dimensional, two-bubble class, heterogeneous model with axial effective diffusion to study the performance of a commercial slurry bubble column reactor. Mass balance equations are solved for every species in the reaction network in the large bubbles, small bubbles, and slurry phase, whereas the energy balance is applied to the slurry phase. The catalyst concentration profile is described by a sedimentation-dispersion model. The combination of microkinetics that generate net production rates for the individual reaction products and hydrodynamics allows describing detailed concentration profiles along the reactor axis as a function of operating conditions and design parameters. As example, the effects of catalyst loading, syngas feed flow rate, inlet temperature, or hydrogen to carbon monoxide inlet ratio on the individual hydrocarbons are investigated. To our knowledge, no reactor model in literature is able to describe detailed compositions at the level described by the reactor model developed in this work. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

    Energy Efficiency of Two-Phase Mixing in a Modified Bubble Column

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2007
    Subrata Kumar Majumder
    Abstract Energy efficiency for gas liquid mixing in a modified downflow bubble column reactor has been analyzed in this paper. Efficiencies of the different parts of the bubble column have been assessed on the basis of energy dissipation. Prediction of the energy dissipation coefficient as well as energy utilization efficiency due to gas-liquid mixing as a function of different physical, geometric and dynamic variables of the system has been done by correlation method. The distribution of energy utilization in the different zones of the column has also been analyzed. Experiments were carried out with air-water and air-aqueous solutions of carboxy methyl cellulose with different concentrations. Dans cet article on a analysé l'efficacité énergétique pour le mélange gaz-liquide dans un réacteur à colonne à bulles à écoulement descendant modifié. Les efficacités des différentes régions de la colonne à bulles ont été évaluées sur la base de la dissipation d'énergie. On a utilisé une méthode de corrélation pour prédire le coefficient de dissipation d'énergie ainsi que l'efficacité d'utilisation de l'énergie due au mélange gaz-liquide en fonction des différentes variables physiques, géométriques et dynamiques du système. La distribution de l'utilisation de l'énergie dans les différentes régions de la colonne a également été analysée. Des expériences ont été menées avec des solutions air-eau et air-solutions aqueuses de carboxyméthylcellulose à différentes concentrations. [source]

    Simulations of Bubble Column Reactors Using a Volume of Fluid Approach: Effect of Air Distributor

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2007
    M. Abid Akhtar
    Abstract Two- and three-dimensional numerical simulations have been performed on a laboratory scale bubble column reactor using a volume-of-fluid approach. The effect of hole-size and superficial gas velocity on the bubble size distribution and their trajectories has been investigated on a 20 cm diameter and 1 m high cylindrical reactor. All simulations were performed in a transient manner using a FLUENT solver. Surface tension between two phases has been modelled as a body force with a constant value. Turbulence was modelled using the k-, turbulence approach. A comparison between simulation predictions and the reported experimental studies has shown a good agreement. On a effectué des simulations numériques bi et tridimensionnelles dans un réacteur à colonne à bulles à l'échelle de laboratoire à l'aide d'une approche volume-de-fluide. L'effet de la taille du trou et de la vitesse de gaz superficielle sur la distribution de tailles des bulles et leurs trajectoires a été étudié dans un réacteur cylindrique de 20 cm de diamètre et de 1 m de hauteur. Toutes les simulations ont été réalisées selon un mode transitoire à l'aide du logiciel FLUENT. La tension de surface entre deux phases a été modélisée comme une force volumique avec une valeur constante. La turbulence a été modélisée par la méthode de turbulence k-,. Une comparaison entre les prédictions des simulations et les études expérimentales mentionnées montre un bon accord. [source]

    A model for the dynamic behavior of a commercial scale slurry bubble column reactor applied for the Fischer,Tropch synthesis

    ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010
    Samira Ghasemi
    Abstract Fischer-Tropsch synthesis (FTS) is an important chemical process for the production of liquid fuels. In the present study, a dynamic model for a commercial size slurry bubble column reactor (SBCR) operating under heterogeneous flow regime and dealing with the FTS has been developed. In such a model a detailed kinetics expressions for the FTS and water gas shift (WGS) reactions have been considered. A selectivity model combined with SBCR hydrodynamics and the multicomponent VLE scheme have been applied to estimate the distribution of olefins and paraffins in the products. In addition, the effects of catalyst deactivation on reactor performance and product distribution under transient conditions may be predicted from this model. The data calculated from the model have been correlated with the experimental results available in the literature. It seems that the present model could be applied to estimate the main characteristics of the reactor's dynamic behavior. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

    Numerical Simulation of Absorbing CO2 with Ionic Liquids

    CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2010
    X. Wang
    Abstract Although separating CO2 from flue gas with ionic liquids has been regarded as a new and effective method, the mass transfer properties of CO2 absorption in these solvents have not been researched. In this paper, a coupled computational fluid dynamic (CFD) model and population balance model (PBM) was applied to study the mass transfer properties for capturing CO2 with ionic liquids solvents. The numerical simulation was performed using the Fluent code. Considering the unique properties of ionic liquids, the Eulerian-Eulerian two-flow model with a new drag coefficient correlation was employed for the gas-liquid fluid dynamic simulation. The gas holdup, interfacial area, and bubble size distribution in the bubble column reactor were predicted. The mass transfer coefficients were estimated with Higbie's penetration model. Furthermore, the velocity field and pressure field in the reactor were also predicted in this paper. [source]

    CFD Modeling of a Bubble Column Reactor Carrying out a Consecutive A , B , C Reaction

    CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2004
    J.M. van Baten
    Abstract In this paper, we develop a CFD model for describing a bubble column reactor for carrying out a consecutive first-order reaction sequence A , B , C. Three reactor configurations, all operating in the homogeneous bubbly regime, were investigated: (I) column diameter DT = 0.1 m, column height HT = 1.1 m, (II) DT = 0.1 m, HT = 2 m, and (III) DT = 1 m, HT = 5 m. Eulerian simulations were carried out for superficial gas velocities UG in the range of 0.005,0.04 m/s, assuming cylindrical axisymmetry. Additionally, for configurations I and III fully three-dimensional transient simulations were carried out for checking the assumption of cylindrical axisymmetry. For the 0.1 m diameter column (configuration I), 2-D axisymmetric and 3-D transient simulations yield nearly the same results for gas holdup ,G, centerline liquid velocity VL(0), conversion of A, ,A, and selectivity to B, SB. In sharp contrast, for the 1 m diameter column (configuration III), there are significant differences in the CFD predictions of ,G, VL(0), ,A, and SB using 2-D and 3-D simulations; the 2-D strategies tend to exaggerate VL(0), and underpredict ,G, ,A, and SB. The transient 3-D simulation results appear to be more realistic. The CFD simulation results for ,A and SB are also compared with a simple analytic model, often employed in practice, in which the gas phase is assumed to be in plug flow and the liquid phase is well mixed. For the smaller diameter columns (configurations I and II) the CFD simulation results for ,A are in excellent agreement with the analytic model, but for the larger diameter column the analytic model is somewhat optimistic. There are two reasons for this deviation. Firstly, the gas phase is not in perfect plug flow and secondly, the liquid phase is not perfectly mixed. The computational results obtained in this paper demonstrate the power of CFD for predicting the performance of bubble column reactors. Of particular use is the ability of CFD to describe scale effects. [source]

    Efficiency of non-reactive isothermal bubble column based on mass transfer

    ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2008
    Subrata Kumar Majumder Assistant Professor
    Abstract Bubble column reactor as a gas,liquid contactor is extensively used in the chemical and biochemical industries. Mass transfer coefficients governing the transport processes in bubble contactors are a growing concern in chemical and biotechnological processes whose rates are often limited by the mass transfer rate. The influences of different physical, dynamic and geometric variables affect the efficiency characterization of the equipment which are involved in gas/liquid mass transfer processes. This characterization has great importance to optimize the process plant design. In this article, efficiency of two-phase mass transfer in bubble column reactors has been analyzed based on dynamic, geometric and physical variables of the system. An empirical correlation for mass transfer efficiency has also been developed in terms of those variables. The present analysis on the gas,liquid mass transfer efficiency of bubble column may give insight into a further understanding and modeling of multiphase reactors in industrial applications. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

    Production of astaxanthin by Haematococcus pluvialis: Taking the one-step system outdoors

    BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009
    M. Carmen García-Malea
    Abstract The feasibility of a one-step method for the continuous production of astaxanthin by the microalga Haematococcus pluvialis has been verified outdoors. To this end, influence of dilution rate, nitrate concentration in the feed medium, and irradiance on the performance of continuous cultures of H. pluvialis was firstly analyzed indoors in bubble column reactors under daylight cycles, and then outdoors, using a tubular photobioreactor. At the laboratory scale, the behavior of the cultures agreed with that previously recorded in continuous illumination experiences, and attested that the major factors determining biomass and astaxanthin productivity were average irradiance and specific nitrate supply. The rate of astaxanthin accumulation was proportional to the average irradiance inside the culture, provided that a nitrate limiting situation had been established. The accumulation of astaxanthin under daylight cycles was maximal for a specific nitrate input of 0.5 mmol/g,day. The recorded performance has been modeled on the basis of previously developed equations, and the validity of the model checked under outdoor conditions. Productivity values for biomass and astaxanthin of 0.7 g/L,day and 8.0 mg/L,day respectively, were obtained in a pilot scale tubular photobioreactor operating under continuous conditions outdoors. The magnitude of the experimental values, which matched those simulated from the obtained model, demonstrate that astaxanthin can be efficiently produced outdoors in continuous mode through a precise dosage of the specific nitrate input, taking also into consideration the average irradiance inside the culture. Biotechnol. Bioeng. 2009;102: 651,657. © 2008 Wiley Periodicals, Inc. [source]

    CFD Modeling of a Bubble Column Reactor Carrying out a Consecutive A , B , C Reaction

    CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2004
    J.M. van Baten
    Abstract In this paper, we develop a CFD model for describing a bubble column reactor for carrying out a consecutive first-order reaction sequence A , B , C. Three reactor configurations, all operating in the homogeneous bubbly regime, were investigated: (I) column diameter DT = 0.1 m, column height HT = 1.1 m, (II) DT = 0.1 m, HT = 2 m, and (III) DT = 1 m, HT = 5 m. Eulerian simulations were carried out for superficial gas velocities UG in the range of 0.005,0.04 m/s, assuming cylindrical axisymmetry. Additionally, for configurations I and III fully three-dimensional transient simulations were carried out for checking the assumption of cylindrical axisymmetry. For the 0.1 m diameter column (configuration I), 2-D axisymmetric and 3-D transient simulations yield nearly the same results for gas holdup ,G, centerline liquid velocity VL(0), conversion of A, ,A, and selectivity to B, SB. In sharp contrast, for the 1 m diameter column (configuration III), there are significant differences in the CFD predictions of ,G, VL(0), ,A, and SB using 2-D and 3-D simulations; the 2-D strategies tend to exaggerate VL(0), and underpredict ,G, ,A, and SB. The transient 3-D simulation results appear to be more realistic. The CFD simulation results for ,A and SB are also compared with a simple analytic model, often employed in practice, in which the gas phase is assumed to be in plug flow and the liquid phase is well mixed. For the smaller diameter columns (configurations I and II) the CFD simulation results for ,A are in excellent agreement with the analytic model, but for the larger diameter column the analytic model is somewhat optimistic. There are two reasons for this deviation. Firstly, the gas phase is not in perfect plug flow and secondly, the liquid phase is not perfectly mixed. The computational results obtained in this paper demonstrate the power of CFD for predicting the performance of bubble column reactors. Of particular use is the ability of CFD to describe scale effects. [source]