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This paper investigates the effect of sparger geometry on flow regime of a bubble column. The experiments presented in this study were performed under atmospheric pressure with water/air in a cylindrical Plexiglas® column of 33.0 cm i.d. and 3.0 m height. Three different perforated plate spargers were employed. Hole diameter was varied in the range of 1–3 mm, while the free area was 1.0%.The theory of linear stability is used for the prediction of regime transitions in the bubble column and a comparison has been presented between the predictions and the experimental observations. A good agreement between the predictions and the experimental values of transition gas holdup has been obtained.In addition, the data from the literature has been analyzed. Experimental values of transition gas holdups and predictions by the theory of linear stability have been compared with those of literature.A correlation based on dimensionless numbers (Archimedes, Froude, Eötvös and Weber) and the group (do/DC) for the prediction of gas holdup in homogeneous regime is proposed. The average error between the correlation predictions and experimental values remains under ±10%.The proposed correlation is compared with the published data and found to be in fairly good agreement. 相似文献
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Jos L. Moreira Pedro E. Cruz Paula C. Santana Ana S. Feliciano Jurgen Lehmann Manuel J. T. Carrondo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,62(2):118-131
Large-scale animal cell operation is costly both in terms of facilities and consumables. Hence developmental studies with animal cells normally start at laboratory scale, often using small stirred tanks. In order to better optimise cell performance, it is necessary to know the physical conditions under which the cells are grown. In this study a laboratory-scale vessel (2 dm3 working volume) with two large-bladed paddle impellers was characterised hydrodynamically. Three different aeration methods (surface, sparging and membrane aeration) were investigated and compared. Power input and oxygen transfer rates to culture medium were determined as a function of agitation and gas flow rates. Non-dimensional correlations were established for each case, which can be useful for scale-up purposes. The results obtained indicate that power input is quite dependent on the vessel accessories: for the same agitation rate, the maximum power is required for the membrane structure and the minimum for surface aeration, with the addition of the sparger leading to an intermediate situation. Predictions found in the literature can be used for simple vessels, but may not be applicable when accessories are added to the vessel structure; in such cases, the use of experimental relationships are required. Oxygen transfer rate was dependent on the aeration method and working conditions (agitation and gas flow rates), particularly for sparger aeration. Membrane aeration gave larger oxygen transfer but higher gas pressure and flow rates were required. Surface aeration was the least effective method, nevertheless requiring gas flow rates similar to those used for membrane aeration. The aeration method of choice depends upon the culture and work specificities: surface aeration is limited to small cell concentrations and low oxygen consumption rates. For higher cell concentrations and oxygen consumption rates, both membrane and sparger aeration methods can be applied: the use of the sparger is limited to cells that are not affected by the presence of bubbles or the addition of surfactants, whereas the membrane aeration basket should not be used when a hydrodynamically controlled stirred tank is required. 相似文献
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Fractional gas holdup was measured in 0.57, 1.0, and 1.5 m i.d. vessels. Pitched blade downflow turbines (PTD) were used as the impeller. Design details of the impeller, such as the impeller diameter (0.22 T to 0.5 T) and blade width (0.25 D to 0.4 D), were studied. The effect of sparger type, geometry and size on fractional gas hold-up has been investigated in detail. Four different types of spargers (pipe, conical, ring and concentric ring spargers) were used. Sparger location was varied for all the types studied. Further, design details of the ring sparger, which gave the highest hold-up were then studied in detail. These included ring diameter, number of holes and hole size. All the reported correlations for fractional gas hold-up in mechanically agitated gas-liquid reactors were tested and compared. A better correlation has been developed for pitched blade turbines. 相似文献
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N.A. Kazakis 《Chemical engineering science》2007,62(12):3092-3103
New experimental data concerning the gas holdup in bubble columns equipped with porous sparger were acquired. The effect of liquid properties and sparger characteristic (i.e., pore size, dimensions) on gas holdup at the pseudo-homogeneous regime has been studied and a correlation regarding the prediction of the transition point from the pseudo-homogeneous to the heterogeneous regime has been proposed and found to be in good agreement with available data. Moreover, a previously proposed correlation [Mouza, A.A., Dalakoglou, G.K., Paras, S.V., 2005. Effect of liquid properties on the performance of bubble column reactors with fine pore spargers. Chemical Engineering Science 60(5), 1465-1475], for the prediction of gas holdup at the homogeneous regime for this type of equipment, has been modified to take into account the effect of the mean pore diameter and it is also found to be in good agreement with published data. 相似文献
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为指导Ⅰ型鼓泡器排放管的结构设计,对常压工况下不同蒸汽质量流速(150~500 kg/(m2·s))、池水过冷度(18~68 ℃)、开孔直径(10、16 mm)和孔数(单孔、双孔)蒸汽浸没射流的压力振荡特性开展实验研究。结果表明:不同开孔结构下的振荡强度均随蒸汽质量流速的升高或池水过冷度的降低而先增大后减小;当孔径增大或孔数增多时,达到稳定冷凝所需的最小蒸汽质量流速降低,流型转变导致振荡强度减小。不同开孔结构下的振荡主频均主要受池水过冷度和开孔直径的影响,且随过冷度的降低或孔径的增大而减小。孔数变化对主频的影响是多重的,但总体效果弱于孔径变化。通过对主频实验值进行拟合,获得了由池水过冷度和排放孔径表征的半经验关系式,相对误差在±20%以内。 相似文献
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使用欧拉两流体模型研究气体分布器结构对气升式环流反应器内气液两相流动的影响,预测了环己烷氧化反应器内单环结构、三环结构、五环结构的气体分布器时反应器内液相速度分布、气含率分布、液相循环速度以及液相微观混合特性.模拟结果表明,在等量的进气流量下,气体分布器环数增加,液相速度分布和气含率分布更趋均匀;气体分布器环数增加,液相推动力增加,从而使得液相循环速度增加,液相的宏观混合效果增强;气体分布器环数增加,导流筒内外的平均气含率增加.随机游走模型模拟结果表明,气升式环流反应器与普通鼓泡床反应器对气体分布器结构要求不同. 相似文献
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带气体分布器表面曝气反应器的气液传质特性 总被引:2,自引:0,他引:2
在高径比较大的表面曝气反应器中,由表面吸入的气体较难分散到反应器的底部,为增强反应器的气液传质性能,需要将反应器底部供气和表面曝气的配置优化。在直径380 mm、液位为530 mm的表面曝气反应器中,表观气速为2.45,4.90,7.35 mm/s的条件下,实验测定了3种不同构型的双层桨组合的气液传质系数和搅拌功率。结果表明,表面曝气结合气体分布器供气能有效改善气液反应器内气体的整体混合状况,以较低的功耗达到气体分布均匀、增强气液传质性能的目的。 相似文献
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