Bubble size distribution in cyclonic zone of a novel flotation column

In order to investigate bubble size distribution (BSD) in the cyclonic flotation column, a series of tests were conducted to study flow velocity distribution (FVD) and BSD by using the method of particle image velocimetry (PIV). Foaming performance of the n-octyl alcohol is more applicable than both of n-butyl alcohol and terpenic oil. At different circulation volume conditions, BSD range lies in 0–800 μm, and a large number of tiny bubbles (<90 μm) are generated. Besides, the curve presents a normal distribution in 90–180 μm. With the increase in circulation volume, bubble size decreases. BSD determined by cyclonic flow effect plays a crucial role on bubble mineralization with fine particle in cyclonic zone of the flotation column.     

Bubble size distribution in a bubble column with vertical tube internals: Experiments and CFD-PBM simulations

Knowledge of bubble size distribution (BSD) is critical for controlling mass transfer and reaction in bubble column reactors. Installation of internals further complicates this issue. The effects of internals on BSD were systematically investigated through experiments and computational fluid dynamics-population balance model simulations. The experiments show a bimodal distribution of the volume-based BSD except at low superficial gas velocity of 0.01 m/s. Addition of 20% internals increases the small-bubbles fraction, making the first BSD peak more evident. Correspondingly, the simulation reveals a prominent decrease of turbulent dissipation rate and turbulent kinetic energy. Moreover, while the unresolved turbulent kinetic energy dominates in the empty columns, the resolved portion becomes the major component in the presence of internals. This suggests that internals may redistribute turbulent kinetic energy in each scale, which provides more insights into the complex flow characteristics in the presence of internals and process intensification.     

二维鼓泡床内气泡尺寸分布的实验与CFD模拟

在有机玻璃制成的二维鼓泡床(0.20m×0.02m×2.00m)内,采用摄像法对空气－自来水的气液两相体系的气泡尺寸分布进行了考察。以商业计算流体力学软件ANSYS CFX 10.0为平台,在双流体模型的基础上,采用k-ε湍流模型和GRACE曳力模型对气液鼓泡床内流体动力学行为进行了多相流CFD数值模拟。结果表明 MUSIG(Multiple Size Group)模型实现了对多气泡体系内气泡尺寸分布特性的考察,气泡尺寸分布的模拟结果与实验结果吻合得较好,从而说明了考虑了气泡聚并破碎的MUSIG模型能很好地反映出鼓泡床内气泡尺寸分布特性。     

鼓泡塔中气泡尺寸分布和局部气含率研究

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。     

Gas holdup characteristics in a flotation column with different solids

This paper presents the effect of process variables on gas holdup. It was measured by volume expansion method in a continuously operating flotation column using coal and sphalerite. It was observed that addition of both solids reduced gas holdup. Increase in solid concentration and particle size reduced gas holdup. Also, increase in gas velocity and frother concentration increased the gas holdup as amount of gas increased and bubble surface property favored the formation of small bubbles. An empirical mathematical model was developed to predict gas holdup. The predicted results were in good agreement with the experimental and available published data.     

An agitated bubble column for use in potash flotation

A novel, agitated bubble column was designed, constructed and operated for the purpose of potash flotation. This report describes the apparatus and presents some typical results regarding bubble size distribution, gas hold-up and flotation efficiency. It was found that the column produced mean bubble diameters and overall gas hold-ups that could be predicted by empirical correlations presented earlier in the literature for aerated, agitated tanks. The column also achieved both a high percentage recovery ( > 90%) and a high product purity (97%).     

Bubble size distribution in bubble columns

The bubble size distributions are measured for the air-water system as a function of air velocity at room temperature in two bubble columns. High speed cinephotography and fiber optic probe techniques are used to measure the bubble size. Our limited measurements suggest that the bubble size may be independent of gas velocity in the range 3.6 to 9.2 cm/s and may be dependent on column diameter with smaller bubbles for narrower columns. The bubble size appears to be smaller at the column wall than at distances away from the wall.     

Application of Statistical Analysis on the Bubble Surface Area Flux in a Column Flotation Cell

Flotation is a widely used separation process with applications from mineral separation to de-inking of recycled paper, waste water treatment, and solid remediation. In flotation column, bubble surface area flux (S_b) has been reported to describe the gas dispersion properties, and it has a strong correlation with the flotation rate constant. No information is available regarding S_b for coal flotation in column cell. This paper describes the effects of hydrodynamic parameters on S_b by means of a 2³ factorial experimental design in designed flotation column using coal slurry. The results showed that S_b increased with increasing superficial gas velocity and frother concentration, but decreased with increasing solid concentration. The main and interaction effects of operating parameters on S_b were evaluated using Yates’ analysis. The statistical model was developed to predict S_b in column flotation cell using experimental data. This paper also presents the development of the statistical model and the validation using a number of additional data sets. There is a good agreement between experimental results and predicted results from the developed model.     

The effect of bubble size on oil-water separation efficiency for a novel oil-water separation column

Bubble size is a key factor in froth flotation for oil-water separation. In this paper, the bubble size which impacts on oil removal efficiency for a novel oil-water separation column was researched systematically. The bubble size distribution was researched by using the photographic method and Matlab software. In addition, several operating parameters which impact on the bubble size were investigated, including circulating pressure, aeration rate, and the foaming agent. Based on the results of experimental data and image analysis, the frother consumption and aeration rate has important influence on the bubble size. The bubble size can be controlled by adjusting the operation conditions including the circulating pressure, aeration rate, and the frother consumption. The optimum operating conditions for the oil-water separation column were determined. Furthermore, the mathematical model of oil removal efficiency for the oil-water separation column was established.     

Bubble size and radial gas hold‐up distributions in a slurry bubble column using ultrafast electron beam X‐ray tomography

Gas hold‐up and bubble size distribution in a slurry bubble column (SBC) were measured using the advanced noninvasive ultrafast electron beam X‐ray tomography technique. Experiments have been performed in a cylindrical column (D_T = 0.07 m) with air and water as the gas and liquid phase and spherical glass particles (d_P = 100 μm) as solids. The effects of solid concentration (0 ≤ C_s ≤ 0.36) and superficial gas velocity (0.02 ≤ U_G ≤ 0.05 m/s) on the flow structure, radial gas hold‐up profile and approximate bubble size distribution at different column heights in a SBC were studied. Bubble coalescence regime was observed with addition of solid particles; however, at higher solid concentrations, larger bubble slugs were found to break‐up. The approximate bubble size distribution and radial gas hold‐up was found to be dependent on U_G and C_s. The average bubble diameter calculated from the approximate bubble size distribution was increasing with increase of U_G. The average gas hold‐up was calculated as a function of U_G and agrees satisfactorily with previously published findings. The average gas hold‐up was also predicted as a function of C_s and agrees well for low C_s and disagrees for high C_s with findings of previous literature. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1709–1722, 2013     

Flow characterization of a flotation column

The flow characteristics of a froth flotation column have been experimentally studied using air and aqueous surfactant solutions without the presence of solids. The hold-up behaviours of the bubbly and the froth zones of the column were linked together using the drift-flux model. The ratio of the gas drift-flux, j_gf, to the bubble terminal velocity, V, for both the bubbly and the froth zones was found to be well correlated by the Richardson–Zaki equation:      

Drop size distribution in a liquid-liquid spray column via a photographic technique

A photographic technique was devised for obtaining drop size distribution in a liquid-liquid (kerosene-water) spray column. Drop sizes were determined with the aid of a reference ball, using a double-flash technique with side lighting. Experimentally analyzed Sauter mean diameters were in good agreement with those predicted by the Kumar and Hartland correlations. The technique was applied up to a holdup of about 6% in this countercurrent flow study     

充填浮选柱正-反浮选胶磷矿工艺研究

通过充填浮选柱浮选胶磷矿的工艺实验,提出了串联操作的正一反浮选流程,得到了较为合适的工艺条件,为生产放大提供了理论依据。     

Drop size distribution and mean drop size in a pulsed packed extraction column

Drop size distribution and mean drop size are used for calculation of interfacial area available for mass transfer. In this study, the drop size distribution and Sauter mean drop diameter (d₃₂) have been investigated using three different liquid systems in the absence of mass transfer in a pilot plant pulsed packed column. The drop size was measured at four different points along the active column height. Three operating variables have been studied including the pulse intensity (af) and flow rates of both liquid phases. The effect of liquid properties and height of the active column were also investigated. A combination of the pulse intensity and interfacial tension had the largest effect on the drop size distribution while none of the flow rates were of significance. The height of the column played an important role at the bottom of the active column, but the associated effect was reduced with increase of the height. Finally, a normal probability function of number density was proposed for prediction of the drop size distribution with an Average Absolute Relative Error (AARE) of 8.8% for their optimized constant. Furthermore, two correlations were presented involving height or flow rates of the two phases along with operating variables and physical properties of the liquids. These correlations had AARE values of about 8.5 and 7.8%, respectively.     

旋流微泡浮选柱在涡北选煤厂的应用

分析了涡北选煤厂煤泥粒度组成,发现煤样矸石存在泥化现象,高灰细泥含量较高,对浮选不利。进行了浮选机的单因素浮选试验、两因素三水平正交试验以及最优药剂条件下的分步释放试验,同时进行了浮选柱的煤泥浮选试验。结果表明,当煤泥矿浆质量浓度为45 g/L,复合药剂为1.10 kg/t时,精煤灰分为10.97%,精煤产率为72.62%,浮选完善指标最高为53.43%,浮选机煤泥浮选效果最好;浮选柱可以分选出各种质量的精煤,精煤灰分可调性大,可以适应市场变化。最后进行了浮选机和浮选柱的综合对比试验,在精煤灰分相近的情况下,浮选柱不同程度地提高了精煤回收率和浮选完善指标,具有明显优势。     

浮选设备流体力学特征参数研究现状

浮选设备是矿物加工工程领域一种重要的气液反应装置,主要包括浮选机和浮选柱。浮选设备应用已有百年历史,随着选矿技术水平的提高,浮选设备逐渐向自动化、大型化的方向发展。近年来对浮选设备内流体力学特征参数的研究解析越来越多,进一步促进了设备的合理放大和优化。本工作在简要介绍目前浮选设备的发展和应用现状后,总结了国内外学者对浮选设备内气泡尺寸、气含率和气泡速度3个重要流体力学特征参数的检测方法和研究现状,提出了在今后研究中,开发以机器视觉为核心的检测技术和强化侵入式检测装置的适用性是流体力学特征参数检测手段的发展方向之一。     

浮选精煤粒度组成对过滤效果的影响与分析

针对浮选精煤过滤工艺系统存在处理能力低、产品水分高等问题,研究精煤粒度组成对过滤效果的影响,分析不同过滤设备的过滤效果,阐述了浮选精煤粒度对过滤工艺的影响和几点看法。     

Effect of frothers on removal of unburned carbon from coal-fired power plant fly ash by froth flotation

The effect of single frothers and their blends on bubble size, froth stability, and unburned carbon (UC) flotation performance was studied. Methyl isobutyl carbinol that produces smaller bubbles is efficient in floating ultrafine particles and producing concentrate. DF-250 that gives higher froth stability is effective for recovering coarse particles and improving recovery. The presence of DF-250 in the blend increases bubble size and significantly enhances froth stability, and hence the optimal flotation performance is achieved with 75% DF-250. It indicates that the frother giving high froth stability is better in UC flotation due to the little effect of UC on froth stability.     

Bubble characteristics in shallow bubble column reactors

The bubble characteristics have been investigated in an air–water bubble column with shallow bed heights. The effect of bed height, location and the presence of solids on the bubble size, bubble rise velocity and overall and sectional gas holdup are studied over a range of superficial gas velocities. Optimal shallow bed operation relies on the combined entrance and exit effects at the distributor and the liquid bed surface. The gas holdup is found to decrease with an increase in H/D ratio but the effect is diminishing at high H/D ratios. A H/D ratio of 2–4 is found to be suitable for shallow bed operation. The presence of solids causes the formation of larger bubbles at the distributor and the effect is diminishing as the gas velocity is increased.     

填料在充填浮选柱中的应用及研究

介绍了化工填料在浮选柱的应用及研究情况,探讨了填料在浮选柱中所起的作用,说明了今后的研究方法及方向。