共查询到20条相似文献,搜索用时 406 毫秒
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A. Borole B. G. Joshi K. Wisecarver Y. T. Shah 《Chemical Engineering Communications》1993,126(1):189-203
This paper describes the results of an experimental study to evaluate phase holdups and RTD for a jet bubble column. The experimental data were obtained in a 61 cm diameter jet bubble column with a conical inlet. Air and water were used as a two-phase system. The ranges of gas and liquid velocities examined were 0 to 9 cm/sec and 0 to 0·6 cm/sec respectively, both based on the cylinder diameter. The experimental data indicate that in the conical section of the column, the gas holdup first decreases with an increase in distance away from the cone inlet, achieves a minimum and then increases until it reaches a somewhat constant value within the cylinder. Gas holdup varies radially with the maximum at the center and the minimum near the wall. Radially-averaged gas holdup increased with gas velocity and remained essentially unchanged with liquid velocity. The RTD measurements were correlated by a two-dimensional dispersion model. The axial dispersion coefficient increased linearly from the cone inlet to the cylinder. It also increased with the gas velocity. The radial dispersion coefficients were considerably smaller than the axial dispersion coefficients. 相似文献
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Counter current bubble columns have the feature that specific gas-liquid interfacial area and gas holdup are larger than those for standard and cocurrent bubble columns. In this study, three different flow regimes, churn-turbulent flow, bubble flow and bubble down-flow, have been observed in a counter-current bubble column and correlations of gas holdup and volumetric liquid-phase mass transfer coefficient have been proposed as functions of operating variables such as the superficial velocities of gas and liquid, the gas-liquid slip velocity and the liquid properties. 相似文献
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Jose A. Salazar Keith D. Wisecarver Y. T. Shah Bruno Solari 《Chemical Engineering Communications》1993,124(1):177-188
The jet bubble column consists of a conical entrance section which expands to a cylindrical column. Gas and liquid are co-currently introduced at the bottom of the column by a small diameter inlet pipe which acts like an ejector. The kinetic energy of the gas and liquid jet together with the conical geometry at the lower section of the column cause the formation and dispersion of small bubbles.
Gas-liquid mass transfer in the jet bubble column (61 cm diameter) was measured by a dynamic response technique, in which a step change was made in the gas phase oxygen concentration and the aqueous dissolved oxygen concentration response was measured at various axial and radial locations. It was found that a continuous stirred tank reactor model could be used to evaluate experimental results. The volumetric mass transfer coefficient in this type of system was found to increase with increasing gas flow rate and was about 1.5 times larger than the values obtained at similar conditions in conventional bubble columns. Preliminary measurements and calculations indicate negligible effects of liquid velocity and bed height on the mass transfer coefficient. 相似文献
Gas-liquid mass transfer in the jet bubble column (61 cm diameter) was measured by a dynamic response technique, in which a step change was made in the gas phase oxygen concentration and the aqueous dissolved oxygen concentration response was measured at various axial and radial locations. It was found that a continuous stirred tank reactor model could be used to evaluate experimental results. The volumetric mass transfer coefficient in this type of system was found to increase with increasing gas flow rate and was about 1.5 times larger than the values obtained at similar conditions in conventional bubble columns. Preliminary measurements and calculations indicate negligible effects of liquid velocity and bed height on the mass transfer coefficient. 相似文献
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Experiments and simulations were conducted for bubble columns with diameter of 0.2 m(180 mm i.d.), 0.5 m(476 mm i.d.) and 0.8 m(760 mm i.d.) at high superficial gas velocities(0.12–0.62 m·s-1) and high solid concentrations(0–30 vol%). Radial profiles of time-averaged gas holdup, axial liquid velocity, and turbulent kinetic energy were measured by using in-house developed conductivity probes and Pavlov tubes. Effects of column diameter, superficial gas velocity, and solid concentration were investigated in a wide range of operating conditions. Experimental results indicated that the average gas holdup remarkably increases with superficial gas velocity, and the radial profiles of investigated flow properties become steeper at high superficial gas velocities. The axial liquid velocities significantly increase with the growth of the column size, whereas the gas holdup was slightly affected. The presence of solid in bubble columns would inhibit the breakage of bubbles, which results in an increase in bubble rise velocity and a decrease in gas holdup, but time-averaged axial liquid velocities remain almost the same as that of the hollow column. Furthermore, a 2-D axisymmetric k–ε model was used to simulate heterogeneous bubbly flow using commercial code FLUENT 6.2. The lateral lift force and the turbulent diffusion force were introduced for the determination of gas holdup profiles and the effects of solid concentration were considered as the variation of average bubble diameter in the model. Results predicted by the CFD simulation showed good agreement with experimental data. 相似文献
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Bubble break-up, gas holdup, and the gas-liquid volumetric mass transfer coefficient are studied in a bubble column reactor with simultaneous injection of a gas and liquid through a T-junction nozzle. The theoretical dependence of bubble break-up and the volumetric mass transfer coefficient on liquid velocity in the nozzle is developed on the basis of isotropic turbulence theory. It is shown that correlations which are developed based on liquid jet kinetic power per nozzle volume explain average gas holdup and the volumetric mass transfer coefficient within an error of 15% for all gas and liquid flow rates and nozzle diameters used. Experiments with a larger scale column, height 4.64 m and diameter 0.98 m, show a transition from homogeneous to heterogeneous flow at a certain liquid flow rate through the nozzle. Liquid composition was found to have a significant effect on gas-liquid mass transfer. A phenol concentration of 10–30 mg/l in water increases the volumetric mass transfer coefficient of oxygen by 100%. This phenomenon may have significance in the chemical oxidation of wastewater. 相似文献
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喷嘴结构对射流鼓泡反应器的混合和传质性能具有重要的影响。以空气-水作为模拟介质,使用双探头电导探针、电解质示踪法和动态溶氧法,对比研究了缩径式圆形喷嘴和旋扭三角形喷嘴对射流鼓泡反应器中气泡尺寸分布、平均气含率、液相混合时间和气液传质系数的影响规律。实验发现,随着气速或液体射流Reynolds数的增大,两种喷嘴对应的平均气含率、液相混合时间和气液传质系数具有相同的变化规律;与缩径式圆形喷嘴相比,采用旋扭三角形喷嘴的射流鼓泡反应器中气泡尺寸更小,平均气含率更高,宏观混合时间更短;当气体输入功占总输入功比例超过20%时,喷嘴结构对气液传质系数的影响较小,当气体输入功占总输入功比例小于20%时,旋扭三角形喷嘴的气液传质性能优于缩径式圆形喷嘴。研究结果可为工业射流鼓泡反应器喷嘴结构的优化提供理论指导。 相似文献
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Sailesh Sudhakarrao Lahore Sudipto Chakraborty Bhim Charan Meikap 《Korean Journal of Chemical Engineering》2012,29(6):724-730
Systems generating uniform small bubbles are used in many mineral processing and chemical operations. We investigated the generation of smaller bubbles by using a two fluid jet system. Gas holdup results are reported in terms of the effect of superficial gas and liquid velocities in relation to the pressure in a bubble column with a water jet sparger. Experiments were conducted with hydrostatic head of 80 cm, 100 cm, and 120 cm in the bubble column. The gas velocity varied from 0.122 to 1.22 cm/s, and water flow rate from 33.3 to 333 cm3/s. Experiments were conducted at pressures of 2 atms., 3 atms. 4 atms. and 5 atms., and bubble sizes were measured by a digital camera (bubble compared to a reference wire inside the bubble column). Results show that the gas holdup increases with the pressure and superficial gas velocities; and at pressures of 2, 3, 4 and 5 atms., the gas holdup increases by 8.75%, 9.166%, 10% and 10%, respectively. The maximum gas holdup of 16.4% was observed at a liquid level of 80 cm and pressure of 4 atms. Optimum conditions for generating smaller bubbles with larger gas holdup are increased liquid flow rate, low liquid level, and high gas pressure. Experimental results also indicate that the column operates in both the homogeneous and heterogeneous regimes of gas-liquid flow. 相似文献
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This investigation reports the experimental and theoretical results carried out to evaluate the gas holdup for air–water system in a novel hybrid rotating and reciprocating perforated plate bubble column under countercurrent condition. The response of this hybrid column is found to be similar to that of reciprocating plate column (RPC) showing mixer‐settler, transition, and emulsion regions. The effect of agitation level, superficial gas velocity, superficial liquid velocity, perforation diameter, and plate spacing on gas holdup is studied and found to be significant. The gas holdup is found to be least in the range of agitation level of 1.3–1.5 cm/s. For all the superficial gas and liquid velocities considered in this present investigation, the critical agitation level at minimum gas holdup remains nearly same. The gas holdup in this hybrid column is 1.2–1.7 times higher in mixer‐settler region and 2.1–2.7 times higher in emulsion region than that of RPC. Correlations have been developed and found to concur with the experimental values. It can be used with 95% accuracy. © 2011 Canadian Society for Chemical Engineering 相似文献
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提出了一种鼓泡塔二维轴对称流体力学模型,模型中将气泡所受的升力以及湍动扩散力作为形成塔内气含率稳定分布的主要机制.采用Fluent 6.3流体力学软件求解模型,能得到稳定的二维流场,气含率与液速分布与实验值吻合良好,模型能准确反映表观气速(0.12~0.62 m·s-1)以及塔径(ø200 mm、ø500 mm、ø800 mm)对流型的影响.利用该模型对更大直径鼓泡塔的流动参数进行了预测,结果与文献给出的经验关联式相符. 相似文献
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Vishal H. Bhusare Dinesh V. Kalaga Mukesh K. Dhiman Jyestharaj B. Joshi Shantanu Roy 《加拿大化工杂志》2018,96(9):1957-1971
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L.Z. PINO R.B. SOLARI S. SIQUIER L. ANTONIO ESTÉVEZ M.M. YÉPEZ A.E. SÁEZ 《Chemical Engineering Communications》2013,200(1):367-382
This work presents experimental data on gas holdup in slurry bubble columns with a foaming liquid. The effects of solids concentration, solid particle size, superficial phase velocities and column dimensions on the gas holdup are analyzed. At low superficial gas velocities (less than 4cm/s), for which the liquid does not foam, the presence of solids with small particle size does not affect the gas holdup whereas solids with large particle size induce foam formation and thus their presence increases the gas holdup. In the foaming regime, an increase of solids concentration decreases the gas holdup. The operating mode has a strong effect on the gas holdup: the semi-batch operating mode (stagnant liquid-solid suspension) increases the ability of the liquid to foam with respect to the continuous mode. Regarding the effect of column dimensions, the results presented show that the height of the bubble column does not affect at an appreciable extent the gas holdup in the range 6 < LID < 12. At high gas velocities (greater than 6 cm/s) the gas holdups obtained in a 30 cm-internal diameter column are the same as those measured in a 10 cm-internal diameter column. 相似文献
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Y. T. Shah N. Yang S. D. Gharat K. Wisecarver 《Chemical Engineering Communications》1991,110(1):53-70
A hydrodynamic study in a gas-liquid jet bubble column was undertaken in a column with a 122 cm diameter cylindrical section and a conical bottom section approximately 180cm in height. Due to the jetting action in the cone, the circulation patterns are different from those in cylindrical bubble columns. In order to examine this difference in flow pattern, circulation velocity measurements were undertaken (for V5 = 0.39-2.73 cm/s and V, = 0-0.044 cm/s) using the Pavlov tube technique. These measurements should be helpful in understanding other design parameters (such as mixing, phase distribution, transport coefficients, etc.). Pressure drops were also measured at nine axial taps and using these values, sectional average gas holdup values were calculated. The study was centered on the conical section; the cylindrical bubble column was assumed to be the limiting case for the interpretation of the data. Using the experimental observations, the height of the jet effective region was approximated by two different methods. A simple empirical correlation to find the centerline velocity is proposed. 相似文献
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在油-氢气体系中使用欧拉-欧拉双流体模型考察了温度703.15 K和压力11 MPa下气升式环流反应器和鼓泡床反应器对气液两相流动的影响. 结果表明,环流反应器中气含率和轴向液速沿导流筒径向存在突增现象,环流反应器中气含率在径向0~0.5和0.75~1时明显大于鼓泡床反应器,在径向0.5~0.75处前者的平均气含率比后者高约6%;环流反应器中上升管内环流液速明显大于鼓泡床反应器,且在下降区有所增强,环流反应器平均轴向液速比鼓泡床反应器高约21%;反应器尺寸较小时环流反应器和鼓泡床反应器的流动特性相差不大,反应器体积放大过程中前者的流动特性优于后者的趋势逐渐明显. 相似文献
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Matías Monsalvo 《Chemical engineering science》2007,62(23):6595-6603
In this work, the influence of structured packing on gas holdup in gas-liquid-solid dispersions has been studied. The experiments were carried out in an empty column and in column containing structured packing operating under identical conditions. Glass beads and silicon carbide particles were used as the solid material and the volumetric fraction of solids was varied from 0% to around 10%. The liquid viscosity was strongly modified using water, CMC solution and glycerol. The experimental results obtained with both columns were compared with previous results obtained in two-phase bubble columns. The influence of structured packing on the total gas holdup for different superficial gas velocities was found to be similar with and without suspended solids. Therefore, the results obtained in this work were analysed on the basis of correlations derived earlier for gas-liquid dispersions. Excepting the results obtained with glycerol, these correlations can predict the gas holdup of three-phase bubble columns with reasonable accuracy. 相似文献