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Diameter Column (diameter + column)
Selected AbstractsInvestigation of nonuniformity in a liquid,solid fluidized bed with identical parallel channelsAICHE JOURNAL, Issue 1 2010Long Fan Abstract Previous work has demonstrated that multiphase flow through identical parallel channels and multiple cyclones can give rise to significant nonuniformity among the flow paths. This article presents results from a study where the distribution of voidage and flux through parallel channels in liquid,solid fluidized beds is investigated. Experiments and computational fluid dynamics simulations were performed with 1.2 mm glass beads fluidized by water where a cross baffle divided a 191 mm diameter column into four identical parallel channels. Voidages were measured by optical fiber probes. Simulations from a three-dimensional unsteady-state Eulerian,Eulerian model based on FLUENT software showed good agreement with the experimental results. Despite the symmetrical geometry of the system, the average voidage and particle velocities in one channel differed somewhat from those in the others. Increasing the superficial liquid velocity could increase voidage greatly and affect the degree of nonuniformity in the four channels. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Destabilisation of homogeneous bubbly flow in an annular gap bubble columnTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010Fahd M. Al-Oufi Abstract Experimental results are presented to show that there are very significant differences in the mean gas void fractions measured in an open tube and a annular gap bubble column, when operated at the same gas superficial velocity, using a porous sparger. Measurements were carried out in a vertical 0.102,m internal diameter column, with a range of concentric inner tubes to form an annular gap, giving diameter ratios from 0.25 to 0.69; gas superficial velocities in the range 0.014,0.200,m/s were investigated. The mean gas void fraction decreases with increasing ratio of the inner to outer diameter of the annular gap column and the transition to heterogeneous flow occurs at lower gas superficial velocities and lower void fractions. Two reasons are proposed and validated by experimental investigations: (1) the presence of the inner tube causes large bubbles to form near the sparger, which destabilise the homogeneous bubbly flow and reduce the mean void fraction; this was confirmed by deliberately injecting large bubbles into a homogeneous dispersion of smaller bubbles, and (2) the shape of the void fraction profiles changes with gap geometry and this affects the distribution parameter in the drift-flux model. Both of these effects serve to reduce the mean gas void fraction in an annular gap bubble column compared to an open tube at the same gas superficial velocity. Des résultats expérimentaux sont présentés pour montrer qu'il existe de très grandes différences dans les fractions de vide gazeux moyennes mesurées dans un tube ouvert et une colonne à bulles à espace annulaire, lorsqu'ils sont utilisés à la même vitesse superficielle de gaz, au moyen d'un aérateur poreux. On a effectué des mesures dans une colonne verticale avec un diamètre interne de 0.102,m, avec une portée de tubes internes concentriques pour former un espace annulaire, procurant des rapports de diamètre de 0.25 à 0.69; des vitesses superficielles de gaz de 0.014 à 0.200,m/s ont été étudiées. La fraction de vide gazeux moyenne diminue avec le rapport croissant du diamètre interne à externe de la colonne à espace annulaire et la transition à la circulation hétérogène se produit à des vitesses superficielles de gaz et fractions de vide plus basses. Deux raisons sont proposées et validés par les vérifications expérimentales: (1) la présence du tube interne provoque la formation de grandes bulles près de l'aérateur, ce qui déstabilize l'écoulement à bulles homogène et réduit la fraction de vide moyenne; cet état a été confirmé en injectant délibérément de grandes bulles dans une dispersion homogène de plus petites bulles et, (2) la forme des profils de fraction de vide change avec la géométrie de l'espace qui les sépare, ce qui a des conséquences sur le paramètre de distribution du modèle à flux de dérive. Ces deux effets servent à réduire la fraction de vide gazeux moyenne dans une colonne à bulles à espace annulaire, en comparaison avec un tube ouvert à la même vitesse superficielle de gaz. [source] Effect of Gas Density on the Hydrodynamics of Bubble Columns and Three-Phase Fluidized BedsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2003Arturo Macchi Abstract Experiments were performed at ambient temperature and pressure in a 127 mm inner diameter column with a 55% wt. aqueous glycerol solution, 6-mm spherical borosilicate beads and four gases , helium, air, carbon dioxide and sulphur hexafluoride , giving a 35-fold gas density range. The dispersed bubble flow regime was sustained to higher gas velocities and gas holdups for denser gases. This finding appears to be due to the reduction of the maximum stable bubble size (i.e. enhanced bubble break-up), rather than to formation of smaller bubbles at the distributor with increasing gas density. The effect of gas density was significant both with and without the particles present, with gas holdup increasing, bed voidage increasing and liquid holdup decreasing with increasing gas density. The holdup correlations of Han et al. (1990) have been modified to incorporate the effect of gas density. On a mené des expériences à la température et à la pression ambiante dans une colonne de 127 mm de diamètre intérieur avec une solution de glycérol aqueux de 55 % en poids, des billes de verre de borosilicate sphériques de 6 mm et quatre gaz , hélium, air, gaz carbonique et hexafluorure de soufre , donnant une gamme de densité gazeuse multipliée par 35. Le régime d'écoulement bouillonnant dispersé est maintenu jusqu'à des vitesses et des rétentions de gaz supérieures pour les gaz plus denses. Ce résultat semble être dû à la réduction de la taille de bulle stable maximum (c.-à-d. une rupture de bulles améliorée), plutôt qu'à la formation de bulles plus petites au distributeur avec l'augmentation de la densité gazeuse. L'effet de la densité gazeuse est significatif avec ou sans la présence des particules, avec l'augmentation de la rétention de gaz, l'augmentation du vide du lit et la diminution de la rétention de liquide avec l'augmentation de la densité gazeuse. Les corrélations de rétention de Han et al. (1990) sont modifiées de sorte à introduire l'effet de la densité gazeuse. [source] Hydrodynamics and mass transfer in a pulsed packed columnTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2000Yu Jie Abstract The hydrodynamics and mass transfer characteristics of a pulsed packed column (PPC) filled with a stainless steel super mini ring (SMR), ceramic and stainless steel Raschig rings have been studied using a 30% tributyl phosphate-kerosene (dispersed phase)/acetic acid/water (continuous phase) system. Experiments were performed in a 100 mm internal diameter column with 1.0 m height of packing. The mass transfer and axial mixing parameters were estimated simultaneously from the measured concentration profiles of two-phase based on the backflow model. It was found that pulsation has great influence on hydrodynamics and mass transfer characteristics of PPC with the SMR. Hoxp and Hox decrease significantly with pulsation, whereas flooding velocity decreases only slightly. Comparison among the three types of packing showed that the SMR has superior characteristics both in terms of capacity and mass transfer efficiency. The influence of mass transfer on characteristics of PPC was also studied. New empirical equations of characteristic velocity, Hoxand Hoxd were proposed and good agreement between calculated and experimental data was obtained. Les caractéristiques de l'hydrodynamique et du transfert de matiére dans une colonne pulsée garni (PPC) contenant des super mini-anneaux (SMR) d'acier inoxydable et des anneaux de Raschig de céramique et d'acier inoxydable (s.s.) ont été étudiées à l'aide du système 30% de phosphate de tributyl-kérosène (phase dispersée)/acide acétique/eau (phase continue). On a mené des expériences dans une colonne de 100 mm de diamètre intérieur avec une hauteur de garnissage de 1.0 m. Les paramètres de transfert de matière et de mélange axial ont été estimés simultanément à partir des profils de concentration mesurés de deux phases d'après le modèle de reflux. On a trouvé que la pulsation avait une grande influence sur les caractéristiques de l'hydrodynamique et de transfert de matière de la colonne PPC avec le SMR. Hoxp et Hox diminuent de maniére significative avec la pulsation, tandis que la vitesse d'engorgement ne diminue que Iégèrement. Une comparaison entre les trois types de garnissage montre que le SMR possède des caractéristiques supérieures à la fois en termes de capacité et d'efficacité du transfert de matière. L'influence du transfert de matière sur les caractéristiques de la colonne PPC a également été étudiée. De nouvelles équations empiriques de la vitesse caractéristique, Hox et Hoxd, sont proposées et un bon accord est obtenu entre les données calculées et les données expérhentales. [source] Separation of product associating E. coli host cell proteins OppA and DppA from recombinant apolipoprotein A-IMilano in an industrial HIC unit operationBIOTECHNOLOGY PROGRESS, Issue 2 2009Alan K. Hunter Abstract We have shown how product associating E. coli host cell proteins (HCPs) OppA and DppA can be substantially separated from apolipoprotein A-IMilano (apo A-IM) using Butyl Sepharose hydrophobic interaction chromatography (HIC). This work illustrates the complex problems that frequently arise during development and scale-up of biopharmaceutical manufacturing processes. Product association of the HCPs is confirmed using co-immunoprecipitation and Western blotting techniques. Two-dimensional gel electrophoresis and mass spectrometry techniques are used to confirm the identity of OppA and DppA. In this example, clearance of these difficult to separate HCPs decreased significantly when the process was scaled to a 1.4 m diameter column. Laboratory-scale experimentation and trouble shooting identified several key parameters that could be further optimized to improve HCP clearance. The key parameters included resin loading, peak cut point on the ascending side, wash volume, and wash salt concentration. By implementing all of the process improvements that were identified, it was possible to obtain adequate HCP clearance so as to meet the final specification. Although it remains speculative, it is believed that viscosity effects may have contributed to the lower HCP clearance observed early in the manufacturing campaign. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] CFD Modeling of a Bubble Column Reactor Carrying out a Consecutive A , B , C ReactionCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2004J.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] | ||||||||||