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1.
在内径为0.38 m的鼓泡塔中采用双电导探针法对不同通气速率下的气泡尺寸分布和局部气含率进行了实验研究,分析了气泡尺寸的概率密度分布。结果表明:气泡尺寸随轴向高度的增加而增大,随径向距离增加而减小;鼓泡塔中气液流动可分为过渡流域和充分发展流域,在过渡流域气含率随轴向高度增加而增大,在充分发展流域气含率趋于均值,径向局部气含率分布呈抛物线型下降。高气速下气泡尺寸概率密度分布比低气速下宽,且随轴向高度的增加分布变宽。  相似文献   

2.
为了解浆态床鼓泡反应器中气含率的分布规律,在浆态床鼓泡反应器冷模试验装置中,以空气-液体石蜡-氧化铝微球为试验介质对装置内部的气含率进行研究。利用压差法研究了表观气速、浆液固含量等操作条件对反应器床层总体气含率的影响,利用光纤探针法研究了浆态床反应器不同操作条件对局部气含率的影响,总结了反应器内部气含率的分布规律,并由此对工业浆态床鼓泡反应器的设计进行了研究。结果表明:浆态床反应器的总体气含率随表观气速的增大而增大,固体细颗粒的加入能适当降低总体气含率;在反应器底部,分布器对气体的均布作用明显,但表观气速的增大能够弱化分布器的作用;在反应器的中上部气含率不受分布器的影响,沿反应器径向呈现"中间高,边缘低"的分布趋势;在工业费托浆态床中,表观气速不宜低于0.12 m/s,内过滤系统适宜设置于反应器中上部靠近器壁的位置。  相似文献   

3.
A 15 cm diameter reciprocating plate column has been operated under gas—liquid flow conditions with a stack of doughnut‐type plates having inner and outer diameters of 7.5 cm and 13.0 cm, respectively. Axial dispersion coefficients and gas holdup have been measured. It is found that this type of plate gives lower axial dispersion coefficients than a previously tested doughnut plate having an outer diameter almost the same as the column internal diameter, but the gas retention times are slightly lower.  相似文献   

4.
Experimental measurement of gas holdup was carried out in a medium-size gas-liquid-liquid bubble column with a multiple nozzle sparger plate using air, water and organic liquids. It was found that the fractional holdup depends on gas velocity, liquid properties, phase inversion in the liquid mixture as well as spreading coefficient of the organic liquid. In the presence of a liquid with a negative spreading coefficient the holdup is a minimum at the phase inversion point. but the reverse is true for a liquid with a positive coefficient of spreading. Observed bubble characteristics have been discussed. Correlations for gas holdup have been developed for different ranges of liquid composition.  相似文献   

5.
The presence of solid particles at lower contents (up to 6% by volume) caused an increase in the gas holdup in the three-phase reciprocating plate column, compared to that in the two phase (gas-liquid) column of the same type, under the same other operating conditions. The decrease in the gas holdup, which was normally observed in the two-phase column, was not found in the three-phase column as the vibration speed was increased at lower levels.  相似文献   

6.
Characteristics of a reciprocating screen-plate bubble column were experimentally determined with dilute alcohol solutions. Results show that the addition of ethanol up to the concentration of 0.8 wt% produces very large gas holdups and overall mass transfer coefficients, in comparison with conventional bubble columns. The plate agitation was shown to cause increases not only in the interfacial area “a” but also in the individual mass transfer coefficient kL when the speed of reciprocation was high.  相似文献   

7.
Air-holdup and heat transfer coefficient data are reported for the air-water and air-water-sand system as a function of air velocity in the temperature range 297-343 K as measured in a 0.305 m diameter bubble column operating in semi-batch mode and equipped with either a five- or seven-tube bundle. A 65 μm average size sand powder is used at concentrations of 5 and 10 mass percent in the slurry. Available correlations of gas holdup and heat transfer coefficients are examined on the basis of these data. These are found inappropriate and inadequate for representing these experimental data. Gas holdup data are well represented by an approach based on Nicklin's (1962) work, and heat transfer data are adequately represented by a simple semi-empirical expression. Accurate experimental data on additional systems are needed to develop a reliable heat transfer theory particularly for process representation at temperatures higher than ambient.  相似文献   

8.
The gas holdup is studies in a gassed reciprocating plate column with the addition of the Rashig rings placed in each interplate space. The gas holdup generally increases with increasing the vibration speed, the superficial gas velocity, and the solids concentration in the range of operating conditions applied. Independently of the solids concentration, the gas holdup is correlated with the power consumption and the superficial gas velocity. The Rashig rings are shown to have more effective dispersion action than the polypropylene spheres under the same other operating conditions.  相似文献   

9.
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   

10.
11.
Experiments conducted in 0.15 m diameter bubble columns using water and non-aqueous liquids have shown that the gas velocity at which transition from the bubbly flow to the churn-turbulent flow regime occurs is a function of gas density. The transition velocity increased with increasing gas density. The direct effect of gas density on gas holdup in the bubbly flow regime is small with only a slight increase in holdup being observed at higher densities (?G α ρg 0.04). In the churnturbulent region a much greater effect of gas density on gas holdup was observed. These differences were found to be a direct function of the differences in holdup values at the transition points. Gas holdup was found to be a function of the gas phase momentum. In the bubbly flow regime holdup was directly proportional to momentum while in the churn-turbulent regime holdup was proportional to momentum to the one third power. Reasons for this behaviour are discussed, as well as the implied effects on liquid mixing in bubble column slurry reactors. The effects of gas density may offer an explanation for some apparently anomalous published results.  相似文献   

12.
This paper reports on the experimental investigation carried out to evaluate fractional dispersed phase holdup for a gas‐liquid mixture in a modified multi‐stage bubble column (with contraction and expansion disks), which has been conceived, designed and fabricated as a wet scrubber for control of air pollution; in addition it has versatile use as a gas‐liquid contactor in chemical process industries. A correlation developed for predicting fractional dispersed phase holdup has been found to be encouraging and highly significant from statistical analysis.  相似文献   

13.
采用改进的Pavlov管测定鼓泡塔中的液相局部流速,采用电导探针方法测定气含率分布,测定了3种塔径(D200mm,D500mm,D800mm)、不同空塔气速下的流速三维分布和气含率分布。  相似文献   

14.
加压大型鼓泡床反应器内大小气泡气含率研究   总被引:6,自引:0,他引:6  
在内径0.3m、高6.6m的加压鼓泡床反应器内采用床层塌落技术测量床层内的大小气泡气含率实验。由于大小气泡上升速度不同,床层塌落曲线存在一水平段,在此基础上,详细考察了表面张力、粘度、系统压力、表观气速对大小气泡气含率的影响,得出大气泡气含率随粘度和表面张力升高而升高,随压力升高而降低;小气泡气含率随粘度和表面张力升高而降低,随压力升高而升高;并根据质量守恒定理,进行了解释。  相似文献   

15.
Including internals in bubble columns is known to enhance the gas holdup. In this paper, a method to achieve this objective substantially has been proposed via the use of vibrating helical spring internals. Experimental observations on effect of vibrating internals such as vibrating helical springs on gas holdup in bubble columns are presented. Effects of superficial gas velocity, H/D ratio (height of the static liquid to column diameter ratio), volume fraction of helical springs, and thickness of the helical spring wires on hydrodynamics parameters are studied. Increase in gas holdup up to 135% is observed by using vibrating helical spring internals in bubble columns compared to bubble columns without internals. This method offers a simple, cost‐effective, and easy way to enhance gas holdup even at high gas fluxes. It has been reported that this enhancement stems from the fact that the vibrating springs breakup the gas into fine bubbles, which effectively reduces their rise velocity and enhances their average residence time in the liquid column.  相似文献   

16.
17.
A novel resistance internal is proposed to optimize the flow field and improve the gas–liquid contact in a co-hydrogenation reactor of coal and vacuum residuum. Local gas holdup, local liquid velocity, and characteristics of the bubble were investigated in a scaled-down laboratory model. The quantitative results showed that the resistance internals could reduce the thickness of the liquid reflux layer by a percentage up to 32% and reduce the difference in the local gas holdup at cross-sections of up to 44%. The Sauter mean diameter of the bubble decreased from 20.30 to 16.00 mm, which aroused the increase in bubble surface area by a percentage of up to 71.9%. The resistance internal promoted the breakup of the bubble with multiple mechanisms and provided diversion to fluid. In this work, improvement at multiple scales was realized, and the technical support for industrial application was provided.  相似文献   

18.
在外径0.3 m的多级鼓泡塔中采用双探针电导探头考察了筛板结构对鼓泡塔中筛板上下两处流体力学参数的影响,并与无筛板鼓泡塔中流体力学参数进行了对比。研究结果表明:带筛板的鼓泡塔中气含率径向分布规律和无筛板的鼓泡塔相类似,筛板上下二侧的平均气含率随表观气速的增加而增加;在鼓泡塔轴向位置上,筛板下侧的气含率普遍比筛板上侧气含率要高;筛板的孔分布方式对于气含率径向分布有着一定影响,但孔径大小对此影响较小。  相似文献   

19.
在带列管内构件的鼓泡塔内测量了4种不同布气方式下的气含率和液速径向分布,并与无列管内构件的空塔中的分布进行了比较。结果表明:中心布气条件下气含率与液速的径向分布比空塔更为陡峭;环隙及近壁布气时呈现出环隙高、两边低的马鞍形分布;均匀布气时径向分布较空塔更为平坦。空塔内气体分布器的影响是局部性的,充分发展段在塔内占主要部分;而在列管塔中气体分布器的影响是全局性的,气含率与液速的初始分布决定着其全塔分布。在带列管的大型鼓泡塔中难以观察到充分发展段的存在,因此,气体分布器的设计具有比空塔更为重要的意义  相似文献   

20.
通过冷模试验方法考察了充填浮选柱捕集区的气含率,经试验数据回归分析,气含率εg=0.096Jg0.91(Hc/D)-0.18。并结合漂移通量的理论,确定充填浮选柱的捕集区为近似均匀鼓泡流。  相似文献   

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