AN EXPERIMENTAL STUDY OF GAS HOLDUP IN TWO-PHASE BUBBLE COLUMNS WITH FOAMING LIQUIDS

Gas-liquid upward flow experiments have been performed in two bubble columns of different diameters (0.10 and 0.29 m,) using air as gas phase and several liquids: water, aqueous solutions of ethanol and glycerine, kerosene, and a solution of a surfactant in kerosene. The main goal of the study is the analysis of foaming systems, including the comparison of their behavior with respect to non-foaming systems. The gas holdup was determined experimentally as a function of the gas and liquid superficial velocities in bubbling, churn-turbulent and foaming regimes. It was found that, for foaming systems, semi-batch operation enhances foam formation, yielding higher holdups than those obtained in continuous operation at very low liquid velocities. Opposite to what is observed in non-foaming systems, the liquid superficial velocity affects the gas holdup appreciably in foaming systems. An increase in column diameter results in a decrease in gas holdup for all the systems studied. In aqueous foaming systems, this trend is more drastic since foam is inhibited as the column diameter increases.     

EFFECT OF SURFACTANT CONCENTRATION ON GAS HOLDUP IN A BUBBLE COLUMN WITH AN ORGANIC LIQUID

This work presents an experimental analysis of the effect of the addition of a surfactant on gas holdup in a bubble column with an organic liquid phase. For the system considered, the addition of surfactant increases the gas holdup by increasing the volume of foam within the column. The surfactant concentration has negligible effect on the intrinsic gas holdup of both the bubbling and foaming regions.     

热态下鼓泡浆液反应器的气含率研究

本文在热态条件下，研究了鼓泡浆液反应器的气含率、反应器直径为0.098m，物系组成为氮气－液体石腊－石英砂。考察了气速、压力、温度、静床高及固体引入等因素对气含率的影响。对于53μm粒子的三相浆态体系，气含率与表观气速关系式为εG=0.053uG^1.2。     

DISPERSION OF GAS AND LIQUID IN BUBBLE COLUMNS OF HOMOGENEOUS BUBBLE FLOW REGIME

Mean gas holdup, lateral distribution of gas holdup and axial mixing of gas and liquid were measured in bubble columns of 12 and 19cm i.d. The lateral distribution of gas holdup was strongly dependent on the flow regimes in the column. The axial mixing of liquid in the homogeneous bubble flow regime was much smaller than that in the heterogeneous bubble flow regime, and was not expressed by existing correlations. The axial mixing of liquid in the homogeneous bubble flow and the intermediate flow regime was simulated with a flow model based on the lateral distribution of buoyancy force and the effective viscosity. The axial mixing of gas was larger than that of liquid.     

HYDRODYNAMICS OF BUBBLE COLUMNS WITH TWO IMMISCIBLE LIQUID PHASES

An experimental study of hydrodynamic parameters of bubble columns with the presence of two immiscible liquid phases, water and kerosene, was performed. The solid used consisted of glass beads with a narrow size distribution. The analysis was based on the determination of global gas holdups and phases distribution along the length of the column in the semibatch mode of operation. The results show thai the presence of two immiscible liquid phases significantly reduces the gas holdup in the bubble column as compared to the results obtained with pure aqueous and organic liquid phases. The distribution of solid phase in a slurry bubble column is drastically affected by the presence of immiscible liquid phases, and exhibits a qualitatively different behavior when compared lo systems with one liquid phase. The addition of small amounts of aqueous phase to a slurry bubble column in which the liquid phase is kerosene results in the sedimentation of the solid. As the amount of aqueous phase added is increased, the solid fluidizes yielding almost flat concentration profiles.     

鼓泡塔中气含率的温度和电解质效应

在直径0.10m、高1.05m 的鼓泡塔中,对空气-水、乙醇、5%NaCl(aq)、5%KCl(aq)、5%CaCl_2(aq)、5%Na_2SO_4(aq)、2.34%MgCl_2(aq)等物系气含率的温度效应和电解质效应进行了实验研究。通过引入((P+Ps)/P)数群很好地关联了气含率的温度效应,找出了气含率的电解质校正因子与液相离子强度的关系。     

ON THE LIQUID FLOW REVERSAL IN BUBBLE COLUMNS

The maximum range of the radial position within which liquid flow reversal can be expected to occur in zero net liquid flow bubble columns is predicted. It is shown that existing models, that employ this position as an input parameter for predicting the liquid velocity profile, are intrinsically valid only when the flow reversal dimensiontess radius is confined to ihe narrow range of 0.644-0.707. It is demonstrated that radial positions outside this range are unacceptable on physical grounds. Guidelines for evaluating the appropriate location of the flow reversal point for typical bubble column operating conditions are proposed.     

气—液鼓泡塔中流动域和气含率的分布

利用压力传感器测定了气、液两相鼓泡塔内不同轴、径向位置上压强的脉动信号,分析了压强的脉动特征,计算了各种操作条件下塔内不同轴向位置截面上的平均气含率,发现在不同操作条件下,塔内可能出现不同的流动域分布,即全塔均匀鼓泡域、全塔过渡域、全塔湍动鼓泡域以及均匀鼓泡域,过渡域和湍动鼓泡域中的相邻2种或3种流域同时出现在塔内不同高度上。提出了不同轴向位置流域转变的判据。并发现,同一截面的不同径向位置基本处于同一流域内。同时研究了鼓泡塔内气含率在轴向上的分布规律,给出了不同流动域内气含率的关系式。     

变径鼓泡浆液反应器的气含率特性

本文研究了变径鼓泡浆液反应器的平均气含率特性,考察了气体速度、静液床高、固体颗粒浓度以及颗粒直径的影响,并提出了变径鼓泡浆液反应器平均气含率的计算方法。     

导流管型鼓泡塔中带泡沫非牛顿型液体的气含率

在塔径０１１２ｍ的三组不同直径导流管装置中，采用液体溢出法测定了带泡沫的非牛顿型液体的气含率分析了表观气速Ｖｇ０和管径比（ＤＲ／Ｄ０）对气含率的影响     

气液逆流鼓泡塔中的气含率与液速分布和数值模拟

分别采用线－线电导探针和背靠背式皮托和测定了气液逆流鼓泡塔中局部气含率和液体轴向速度的径向和轴向分布,讨论了操作条件对气含率与液体轴向速度分布的影响,利用双流体模型对塔内两相湍流流动进行了数值模拟。     

SPATIAL DISTRIBUTION OF GAS AND SOLID PHASES IN CONICAL SLURRY BUBBLE COLUMNS

In this work we perform an experimental study of the spatial distribution of phases in slurry bubble columns with conical distributors that have a volume comparable to that of the cylindrical section. Three different distributors were used whose apex angles were 13°, 22° and 34°. In gas-liquid operation, the gas holdups are axially uniform in the cylindrical section and decrease towards the wall, whereas in the conical section they increase towards the inlet. These trends are observed in the three cones for all the operating conditions explored. The solids distributions in the conical sections are qualitatively different depending on whether the operation is semibatch or continuous with respect to the flow of solid-liquid suspension: in semibatch operation, the concentration monotonically increases towards the bottom of the cone and exhibits a slight increase as the wall is approached; in continuous operation, an absolute maximum in solids concentration is obtained at a point located on the wall of the cone and intermediate height. The location of this maximum moves upwards as the total solids content in the column increases and as the apex angle decreases. The maximum in solids concentration signals the most probable site for the onset of solids sedimentation and the presence of low mixing levels and reduced mass transfer rates in a slurry reactor. In the range of conditions explored in the present work, the lowest apex angle (13°) yields a more uniform solids distribution throughout the system     

浆液循环锥形鼓泡塔反应器的相含率研究

在浆液循环条件下，考察了以空气、水和石英砂为三相体系的锥形鼓泡塔反应器（Φ顶２００ｍｍ，Φ底１００ｍ，高３０００ｍｍ）中的相含率及固体颗粒浓度轴向分布。使用压降法和颗粒同步取样方法测量了不同表现气速（０￣０．１２５ｍ／ｓ），表现浆液循环速（０￣０．１５７ｍ／ｓ）以及固体颗粒浓度０￣１００ｋｇ／ｍ＾３下相含率分布，并用园柱床的一维沉降－扩散模型近似地描述了固体颗粒辆向浓度分布的规律。在此基础上，本文     

A SIMPLE EXPERIMENTAL TECHNIQUE TO MEASURE GAS PHASE DISPERSION IN BUBBLE COLUMNS

A new technique to measure gas phase dispersion in bubble columns is presented. This technique is fairly simple to implement, accurate and inexpensive as compared to conventional methods used in the literature. Nitrogen is used as a tracer and a step change is effected by switching from air to the tracer, nitrogen. The gas phase concentration of oxygen is monitored by means of a polarographic oxygen sensor. The system studied is air-water and the experimental results compare well with the literature data. The technique presents a simple way to measure gas phase axial dispersion in bubble columns and can also be applied to other types of reactors     

A SIMPLE EXPERIMENTAL TECHNIQUE TO MEASURE GAS PHASE DISPERSION IN BUBBLE COLUMNS

A new technique to measure gas phase dispersion in bubble columns is presented. This technique is fairly simple to implement, accurate and inexpensive as compared to conventional methods used in the literature. Nitrogen is used as a tracer and a step change is effected by switching from air to the tracer, nitrogen. The gas phase concentration of oxygen is monitored by means of a polarographic oxygen sensor. The system studied is air-water and the experimental results compare well with the literature data. The technique presents a simple way to measure gas phase axial dispersion in bubble columns and can also be applied to other types of reactors     

操作变量对大型浆态床反应器流体力学特性的影响

研究了系统压力、表观气速和固体颗粒体积分数对浆态床反应器气含率、气泡直径及气液接触面积的影响 ,通过试验得出了气含率和操作变量之间的统计关联式 ,给出了在湍流条件下浆态床反应器中气含率和气体动量之间的关系     

THEORETICAL PREDICTION OF GAS HOLDUP IN BUBBLE COLUMNS WITH NEWTONIAN AND NON-NEWTONIAN LIQUIDS

A simple model based on an energy balance which takes into account the friction losses at the gas-liquid interface and the slip velocity of single bubble is used to simulate the gas holdup in bubble columns containing Newtonian and non-Newtonian liquids which circulate in both laminar and turbulent flows. Experimental data available from the literature for bubble columns up to 7 m height and 1 m diameter with water and glycerol as Newtonian liquids and different solutions of CMC in a wide range of concentrations as non-Newtonian liquids are simulated with good agreement despite the simplifications made to describe the gas liquid flow regimes. Most of the differences between experimental and calculated gas holdup are justified on the basis of the simplifying assumptions.     

CHARACTERIZATION OF GAS-LIQUID FLOWS IN RECTANGULAR BUBBLE COLUMNS USING CONDUCTIVITY PROBES

Unsteady gas-liquid flows in bubble columns are comprised of various flow processes occurring with varying length and time scales and govern mixing and transport processes. In the present work, we have characterized dynamic and time-averaged properties of gas-liquid flows in rectangular bubble columns using conductivity probes. The development of a single-tip conductivity probe, data processing methodology, and photographic validation procedure is discussed in detail. The effect of superficial gas velocity and aerated liquid height-to-width (H/W) ratio on voidage fluctuations and time-averaged gas holdup was investigated. The experimental data presented here can help in understanding the dynamics of various flow processes and validating computational fluid dynamics based models.     

FORMATION AND FLOW OF GAS BUBBLES IN A PRESSURIZED BUBBLE COLUMN WITH A SINGLE ORIFICE OR NOZZLE GAS DISTRIBUTOR

The characteristics of gas bubbles in a 5 cm diameter bubble column equipped with a single orifice of 1,3 or 5 mm diameter were investigated under system pressure of 0.1-15 MPa. The formation of gas bubbles was strongly affected by the system pressure. Under high pressures a dispersed gas jet was formed at gas velocities where spherical gas bubbles would have been formed at atmospheric pressure. The critical gas velocity between the bubbling regime and the jetting regime was correlated with the liquid phase Weber number and the gas phase Reynolds number based on the gas velocity at the orifice. Bubble size and gas holdup in the main part of the bubble column were also affected by the bubble formation pattern at the distributor     

气液及气液固三相浆态鼓泡塔的气相轴向返混系数

气液及气液固三相浆态鼓泡塔的气相轴向返混系数宋同贵，赵玉龙，苏晓丽，张碧江（中国科学院山西煤炭化学研究所，煤转化国家重点实验室，太原０３０００１）关键词：气液鼓泡塔，浆态鼓泡塔，气相轴向返混１前言在鼓泡塔反应器的设计、放大及数学模拟中，气相轴向返混系...