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。     

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     

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.     

PREDICTION OF GAS-PHASE HOLDUP IN A BUBBLE COLUMN

Hydrodynamic properties of bubble columns play a significant role in many chemical and biochemical processes. Recent theoretical and experimental work conducted by Krishna et al. (1991, 1994), and Wilkinson et al. (1992) have been examined in conjunction with a bubble column and data for the air-water system operating at ambient conditions. The bubble column is 0.108 m in internal diameter, has a 1.70 m tall test section, and is equipped with a perforated plate distributor having 91 holes of 0.8 mm diameter. The data are taken for five values of the slumped water column height in range from 0.79 to 1.15 m, and for superficial air velocities up to about 0.4 m/s.

The data accord to the qualitative aspects of Krishna et al. model but lead to different values of the bubble swarm rise velocity, and superficial transition air velocity characterizing the transition from homogeneous bubbly flow regime to heterogeneous churn-turbulent flow regime. The quantitative reproduction by the model expressions of these recent works of the experimental data is poor. This may be partly attributed to the geometry of the column, diameter and distributor design.

The qualitative features of Krishna et al. model for the two regimes are confirmed by the present data. For quantitative predictions of gas-phase holdup, a new model is proposed in which the large bubble flow in the churn-turbulent regime is formulated following the drift-flux theory. The proposed theory and experimental data are in good agreement.     

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。     

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。     

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.     

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。     

POWER CONSUMPTION AND GAS HOLDUP IN A GAS-LIQUID RECIPROCATING PLATE COLUMN

The pressure fluctuation at the column base is confirmed to be proportional to the vibration intensity on a power of 2 in non-gassed conditions and up to a critical vibration intensity, corresponding to the dispersion resonance frequency, in gassed conditions. The power consumption is successfully correlated with the vibration intensity and the liquid holdup. The gas holdup in both mixer-settter and emulsion regime is well correlated with the power consumption and the superficial gas velocity. The effect of the superficial gas velocity is more important than that of the power consumption. The effects of the liquid phase properties, the wetting tendency of the plate material and the fraction free area above 41% were not observed     

EFFECT OF OPERATING CONDITIONS ON GAS HOLDUP IN SLURRY BUBBLE COLUMNS WITH A FOAMING LIQUID

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.     

开孔转盘塔(RPDC)分散相滞存率及液滴直径分布的研究

本文在无传质条件下研究了RPDC内乳液-水体系的流体力学性能。测定了塔内分散相滞存率x,考察了塔几何条件及操作条件对x及特性速度u_6的影响。采用因次分析法,建立了x及u_o与塔几何条件及操作条件间的经验关联式。并采用摄影法,对分散相液滴直径d_滴及其分布进行了初步研究。实验结果表明,d_滴的分布可用上限对数正态分布来描述。     

AXIAL DISTRIBUTION OF SOLID PARTICLES IN BUBBLE COLUMN SLURRY REACTORS IN THE BUBBLE FLOW REGIME

Physical mechanisms responsible for the suspension of solid particles in semi-batch bubble column slurry reactors in bubble flow are identified, thus allowing the classification of solids into four states: free, engaged, wake-entrained and captured particles. A theory is then presented to predict the axial distribution of solids when wake-entrained and captured particles are absent. Reasonable agreement is found between the theory and experimental data obtained in this work and those reported by otherinvestigators.     

AXIAL DISTRIBUTION OF SOLID PARTICLES IN BUBBLE COLUMN SLURRY REACTORS IN THE BUBBLE FLOW REGIME

Physical mechanisms responsible for the suspension of solid particles in semi-batch bubble column slurry reactors in bubble flow are identified, thus allowing the classification of solids into four states: free, engaged, wake-entrained and captured particles. A theory is then presented to predict the axial distribution of solids when wake-entrained and captured particles are absent. Reasonable agreement is found between the theory and experimental data obtained in this work and those reported by otherinvestigators.     

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。     

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     

浆态床内颗粒浓度分布的研究

1 前言浆态床内固体颗粒可以是反应物、生成物、固体催化剂或催化剂载体。固体颗粒的大小和浓度分布与其他流体力学因素相互作用,可以改变过程的传质、传热性能,进而影响反应的转化率和选择性。尤其是对强放热催化反应,作为催化剂的固体颗粒,其浓度分布不同,造成了反应器内各处反应速率的差异,从而引起各处不同的温度效应,结果导致反应速率的更大差异。Serpemen 和 Deckwer 对 F—T 合成、CO 甲烷化和丁炔二醇加氢过程中催化剂分布对转化率影响的分析,证明在设计反应器时必须考虑固体颗粒浓度分布。     

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     

HYDRODYNAMIC STUDIES IN FISCHER-TROPSCH DERIVED WAXES IN A BUBBLE COLUMN

Gas hold-up and Sauter mean bubble diameter measurements were made in a 0.051 m diameter by 3 m long glass bubble column in the system, nitrogen-molten wax, with three different waxes (paraffin wax FT-300, Sasol's Arge wax and Mobil's reactor wax). Paraffin wax has a tendency to foam and gas hold-up is a strong function of gas distributor type, temperature and start-up procedure, whereas the reactor waxes do not foam and are much less affected by these variables, In experiments at 265°C with a 1.85 mm single hole orifice plate distributor the gas hold-ups were nearly the same for all three waxes. However, significant differences in Sauter mean bubble diameters were obtained in experiments with different waxes; FT-300 wax produced the smallest Sauter mean bubble diameters whereas Mobil's reactor wax produced the largest bubbles. Addition of 1-octadecanol and octadecanoic acid (up to 10wt%) to the FT-300 paraffin wax caused an increase in gas hold-up and a delay in the foam break-up in runs at 265°C with the 1.85 mm orifice plate distributor.     

HOLDUP MEASUREMENT IN A SCHEIBEL EXTRACTION COLUMN

ABSTRACT The total holdup of a dispersed organic phase in a rotary-agitated Scheibel liquid-liquid extraction column of the first type is studied experimentally. The column is 2 inches in diameter and contains 11 stages with a 4-inch height packed section and a 1-inch height mixing section. The packed section is made of stainless steel wire mesh packing with a 93.74% free area and acts as a settler for the coalescence of droplets. Three systems are studied: benzene/water, methyl isobutyl ketone (MIBK)/water and 20% TBP-80% kerosene/1?M nitric acid. The effects of different phase flow rates and rotation speeds (300-670?rpm) on the dispersed phase holdup are investigated. The results show that the holdup increases with increasing dispersed phase flow rate but does not vary with continuous phase flow rate. For benzene, the holdup is large at low rotation speeds and decreases with increasing rotation speed until a minimum holdup is reached, after this transition point, the holdup increases with increasing rotation speed. This phenomena is analogous to that found in a pulse column. For MIBK and 20% TBP-kerosene, the holdup always increases with rotation speed in our experimental range and the transition point is not observed as M in benzene. This is attributed to the much larger interfacial tension of benzene-water as compared with the other 2 systems.