Gas—Liquid Flow Through Helical Coils in Horizontal Orientation

Experimental investigations have been carried out to evaluate the two‐phase pressure drop and the holdup for gas‐Newtonian liquid flow through helical coils. 24 helical coils and three different liquids were used for the experiments. Empirical correlations have been developed to predict the two‐phase friction factor and the liquid holdup as functions of various physical and dynamic variables of the system. Statistical analysis of the correlations suggests that they are of acceptable accuracy.     

Effect of Plate Wettability on Dispersed-Phase Holdup in a Pulsed Disc-and-Doughnut Solvent Extraction Column

The effect of plate wettability on the dispersed-phase holdup in a pulsed disc-and-doughnut solvent extraction column is presented. Teflon, nylon, and stainless steel plates have been used to simulate a change in the wetting characteristics of the plate material that can occur in an operating column due to ageing or deposits accumulating on the plate. Experimental holdup data have been measured over a range of operating conditions using a 1.0 m long glass column with an internal diameter of 72.5 mm containing alternating discs and doughnuts. The liquid-liquid system studied was tri-n-octylamine (TOA)-kerosene-water with sulphuric acid as the solute. Results show that there are noticeable changes in the characteristic velocity (determined from measured holdup) and operational regimes for the different plate materials, particularly at low pulsation intensities, when operating under dispersed aqueous conditions. Experimental holdup data from this study have also been compared to correlations from literature for predicting holdup. As none of these correlations for holdup incorporate plate wettability, a new correlation for predicting holdup has been proposed that incorporates the contact angle of the plate material to allow for changes in the wettability of the plate surface. This correlation is able to predict the holdup data from this study to within 10.5% for aqueous dispersed conditions.     

Studies on cocurrent gas-liquid flow in helically coiled tubes. I. Flow patterns,pressure drop and holdup

The effects of tube diameter, coil diameter, helix angle and liquid viscosity on flow patterns, pressure drop and holdup for cocurrent gas-liquid flow in helically coiled tubes have been investigated. Nine coils of varying coil diameter and helix angle have been used with liquids of three different viscosities and air at varying pressures. The effect of tube diameter on pressure drop and holdup was determined by using tubes of diameters up to 2-in. Flow patterns were adequately predicted for all the systems by Baker's plot. Small helix angles were found to have no effect on pressure drop or holdup in coiled tubes. Both pressure drop and holdup could be adequately correlated using the Lockhart-Martinelli approach with modified correlating parameters.     

Prediction of Pressure Drop and Holdup for Homogeneous Ternary Mixtures of Spherical Glass Bead Particles in a Three-Phase Fluidized Bed

Hydrodynamic characteristics, viz. bed pressure drop and gas holdup, have been studied for ternary mixtures of homogeneous regular particles in a co-current three-phase fluidized bed. For this, a series of experiments have been carried out in a 5-cm diameter column with air as the gas phase, water as the liquid phase, and ternary mixtures of glass beads (1.54, 1.3, and 1.1 mm) as the solid phase. The dependence of bed pressure drop on the average particle diameter, superficial gas velocity, and initial static bed height has been discussed. Based on the dimensional and statistical analyses, correlations have been developed with the system parameters, for both bed pressure drop and gas holdup. Experimental values of bed pressure drop and gas holdup have been found to agree well with those calculated from developed correlations.     

Flow characteristics in a column agitated by blade impellers

Flow characteristics, axial dispersion coefficients in the continuous phase, and holdup of the dispersed phase were studied in a 4.66 cm inside diameter and 100 cm height column agitated by blade impellers. Flow characteristics were analyzed by residence time distribution using impulse input of a tracer. The best reasonable values of Peclet number and holding time were able to obtain by using the response surface method. The axial dispersion coefficients in the single phase flow, and in the two-phase countercurrent flow have been correlated within a confidence level of ±10% when impeller diameter, impeller speed and compartment height, were used as variables. The holdup of the dispersed phase was also correlated in terms of impeller diameter and the operating variables.     

Trickle-bed reactors: Tracer study of liquid holdup and wetting efficiency at high temperature and pressure

Liquid holdup and wetting efficiency were measured by means of stimulus-response (pulse-tracer) experiments in a trickle-bed reactor, packed with a commercial hydrodemetallization catalyst, and operated at 10 MPa and 330–370°C, with a superficial liquid velocity of 1.4 to 8.3 × 10^?4 m/s. The total liquid holdup was obtained from the first moments, and the external wetting efficiency from the second moments, of the response curves. The dynamic holdup obtained from the total holdup lies within the range described by existing correlations, but wetting efficiency is significantly lower than literature data obtained at ambient conditions.     

Hydrodynamics and mass transfer enhancement of gas–liquid flow in micropacked bed reactors: Effect of contact angle

Pressure drop, residence time distribution, dispersive behavior, liquid holdup, and mass transfer performance of gas–liquid flow in micropacked bed reactors (μPBRs) with different contact angles (CA) of particles are studied. The value of pressure drop for three types of beads can be obtained: copper beads (CA = 88.1°) > stainless steel beads (CA = 70.2°) > glass beads (CA = 47.1°). The liquid axial dispersion coefficient is 1.58 × 10⁻⁶ to 1.07 × 10⁻⁵ m²/s for glass beads and copper beads, which is smaller than those of trickle bed reactors. The liquid holdup of 400 μm copper beads is larger than that of 400 μm glass beads. The ratio of effective interfacial area enhancement is evaluated up to 55% for big contact angle beads compared with the hydrophilic glass beads. In addition, correlations of pressure drop, liquid holdup, and effective interfacial area in μPBRs with different wettability beads are developed and predicted values are in agreement with the experimental data.     

有蛇管的釜中气液机械搅拌的功率研究

比较了挡板和蛇管对搅拌功率的影响关系，并在Ф４７６和Ф７８４两台几何相似的有蛇管釜中，采用六直叶圆盘涡轮，详细研究了不同液体中搅拌功率与通气量，桨径，桨层数，液位等因素的关系，由回归分析法得不通气时桨的功率准数Ｎｐ为Ｎｐ＝２．４（Ｄ／Ｔ）－０．３２．ｎ０．５１．（Ｈ／Ｔ）０．５７通过时的搅拌功率计算式为Ｐａ＝１．６６（Ｐ０＾２．Ｎ．Ｄ＾３／ＱＧ＾０＾．＾５＾６）０．４１当在Ф１０００釜中安置三层圆     

A correlation for gas holdup in turbulent coalescing bubble columns

A review of existing literature for the purpose of comparing correlations which allow the explicit predictiosn of gas holdup in two- or three-phase bubble columns shows wide disagreement concerning the effect of various variables. Further, various correlations, apparently of equal validity, show equally wide disagreement in the predicted absolute values of gas holdup among three test systems; water-air, hydrocarbon solvent—air, and trichloroethytene air. Some possible reasons for these disagreements are discussed. Extensive gas holdup data obtained in a 0.30 m diameter column for the three test systems were correlated statistically for the transition and the turbulent region. The resulting correlation gives agreement with experiment to within ±20%, with most data showing ± 10% agreement. The proposed correlation was also tested against thirteen data sets (from eight researchers) which corresponded to its region of validity and gave good agreement. Three additional relevant data sets were not satisfactorily predicted.     

垂直管中气,液两相上升流动摩擦压降测定的改进

本文研究了气、液两相垂直上升流动的摩擦压降，改进了两相液中流体的压差与持液量的测定技术，实验在内径为１９ｍｍ、高度为１５００ｍｍ的垂直玻璃管中完成，实验介质采用空气与水，两相流摩擦压了值通过测定压差与持液量实验数据计算得到，流型通过观察决定。     

Characterization of hydrodynamic parameters in a multistage column contactor

Accurate knowledge of hydrodynamic parameters is of major importance for the performance study of liquid-liquid column extractors. The effects of operating parameters on dispersed phase holdup profiles, drop size distributions, and axial mixing in both phases were investigated in a 127 mm diameter multistage contactor of pilot plant scale for the toluene-water physically equilibrated system. Correlations for the mean holdup, the mean drop size, and the continuous phase backmixing were obtained. A stronger dependence of holdup and drop size on the operating conditions and especially on the agitation speed was observed as compared to previous investigations for the same type of contactor. The axial mixing for the single phase flow was found to follow adequately an existing correlation, while the continuous-phase axial mixing in two-phase flows showed some deviations from other existing correlations. Also, flooding criteria, important for the control of the extraction process, were determined based on the shape of the holdup profiles.     

Influence of structured packing on gas holdup in a three-phase bubble column

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.     

Regime Transition and Holdup in Pulsed Sieve-Plate and Pulsed Disc-and-Doughnut Columns: A Comparative Study

This study reports a detailed comparison of dispersed-phase holdup and onset of different operating regimes in PSPC (pulsed sieve-plate column) and PDDC (pulsed disc-and-doughnut column) for 3 N nitric acid–30% tributyl phosphate (TBP) in dodecane system. Experiments are performed in a 3-inch glass column with SS internals for aqueous-continuous mode of operation keeping O/A ratio at 1:3. The effects of column throughput (0.0097–0.0219 m/s) and pulsing velocity (0.011–0.039 m/s) on holdup and onset of operating regimes are studied and compared. Holdup in PDDC is found to be consistently more than that in PSPC. Onset of dispersion regime is found to be delayed in PDDC in comparison to PSPC. Insights into the movement of a typical dispersed-phase drop under pulsatile flow in PSPC have been provided. Additionally, a sensitivity analysis of the effect of pulsing velocity on holdup in PDDC and PSPC is reported. For the phase system and O/A ratio used in the experiments, holdup in PSPC is observed to be more sensitive to variation in pulsing velocity as compared to PDDC. Efficacy of several previously reported correlations to predict dispersed-phase holdup in PSPC and PDDC is evaluated using the experimental data generated in this study.     

Two phase (air-molten carbonate salt) flow characteristics in a molten salt oxidation reactor

Molten salt oxidation process is one of the most promising alternatives to incineration that can be used to effectively destroy the organic components of mixed and hazardous wastes. To detect the flow characteristics of the molten salt oxidation process (air-molten carbonate salt two-phase flow), differential pressure fluctuation signals from a molten salt oxidation process have been analyzed by adopting the stochastic methods. Effects of the input air flow rate (0.05–0.22 m/sec) and the molten salt temperature (870–970 °C) on the phase holdup and flow characteristics are studied. The gas holdup increases with an increasing molten salt temperature due to the decrease of the viscosity and surface tension of the molten carbonate salt. It is found that a stochastic analysis of the differential pressure signals enables us to obtain the flow characteristics in the molten salt oxidation process. The experimentally obtained gas holdup data in the molten salt reactor were well described and characterized by means of the drift-flux model. This work was presented at the 7th China-Korea Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.     

合成气制二甲醚三相淤浆床反应器气含率

引　言二甲醚是近年来国内外竞相开发、性能优越的碳一化工产品 .二甲醚不仅是从合成气制汽油、低碳烯烃的重要中间体 ,而且也是多种化工产品的重要原料 .同时由于二甲醚具有优良的燃烧性能和高的辛烷值 ,作为柴油的替代品日益引起人们的普遍关注 .随着对环境和生态平衡保护力度的加大 ,二甲醚的作用和地位将越来越重要 .与传统的采用固定床反应器以甲醇为原料脱水生成二甲醚的生产工艺相比 ,以煤或天然气为原料 ,通过合成气在三相淤浆床反应器中一步法合成二甲醚新工艺具有巨大的优越性 .三相淤浆床反应器流体力学性质十分复杂 ,目前还不能…     

Prediction of two‐phase pressure drop and liquid holdup in co‐current gas–liquid downflow of air–Newtonian systems through packed beds

The dependency of pressure drop and liquid holdup on phase velocities, geometry of the column and packing materials as well as on the physical properties have been analyzed. Our experimental data (825 data points obtained using four liquid systems and three different particles) along with those of the available literature (776 data point from five different sources) were used for the analysis. The applicability and the limitations of the literature correlations were evaluated using the available data. Based on the analysis, new correlations for the estimation of pressure drop and liquid holdup, valid for low and high interaction regimes have been developed using the available data, with a wide range of variables. Copyright © 2005 Society of Chemical Industry     

Gas Holdup and Solid‐Liquid Mass Transfer in Newtonian and non‐Newtonian Fluids in Bubble Columns

Gas holdup and surface‐liquid mass transfer rate in a bubble column have been experimentally investigated. De‐mineralized water, 0.5 and 1.0% aqueous solutions of carboxy methyl cellulose (CMC), and 60% aqueous propylene glycol have been used as the test liquids. Effects of column diameter, liquid height to column diameter ratio, superficial gas velocity and liquid phase viscosity on gas holdup and mass transfer rate are studied. Generalized correlations for the average gas holdup and wall to liquid heat and mass transfer coefficients are proposed. These are valid for both Newtonian and pseudoplastic non‐Newtonian fluids.     

Pressure drop and liquid holdup for two phase concurrent flow in packed beds

Pressure drop and liquid holdup for two-phase concurrent downward flow in packed beds were correlated for various types of packings by taking into account two hydrodynamic regimes: a poor and a high gas-liquid interaction regime.Foaming and non-foaming systems have been considered.In the poor interaction regime, the pressure drop was calculated as due to the gas flowing in a bed restricted by the presence of the liquid. A correlation valid for a free liquid trickling, modified in order to take into account the effect of the pressure drop, is proposed and used to correlate liquid holdup in the presence of a concurrent gas flow.In the high interaction regime, empirical correlations were proposed for both foaming and non-foaming systems.All the employed correlations fit experimental results from several authors better than those proposed in the literature.     

加温加压下CFD-PBM耦合模型空气-水两相流数值模拟研究

计算流体力学与群体平衡模型（CFD-PBM）结合可有效地模拟鼓泡塔内流体行为,较准确地预测流场、相含率以及局部气泡尺寸分布。以直径100 mm、高1.3 m的加温加压鼓泡塔为模拟对象,在系统压力为1 MPa、表观气速为0.08~0.24 m/s、温度为30~160℃条件下系统地考察了空气-水体系的表观气速、温度以及固含率对平均气含率、大小气泡气含率、气泡直径和气泡尺寸分布等参数的影响。结果表明,平均气含率的模拟结果和实验值在10%的误差范围内吻合较好;温度的变化主要影响了塔内气泡的聚并和破碎,并用聚并破碎的机理解释了温度对其流体行为的影响。