充填式浮选柱中径向返混及流速分布对浮选效果影响的研究

建立了充填式浮选柱的二维混合模型,并对该模型进行了数值法求解,探讨了径向返混系数和轴向气、液流速沿径向的分布对充填式浮选柱捕集区的回收率的影响.结果表明,增大径向返混系数有助于提高回收率;轴向气、液流速沿径向的分布越均匀越好;气速的不均匀分布将对回收率造成较大影响.分析结果对提高充填式浮选柱的浮选效果具有一定的理论指导意义.     

规整填料塔液相混合的研究

本文采用点源脉冲示踪的方法考察了装填２５０ Ｙ 型金属板波纹规整填料的填料塔中的轴向及径向返混。在规整填料塔的顶部注入 Ｋ Ｍｎ Ｏ４ 作为示踪剂,从塔的底部的不同径向位置取样。通过最优化方法计算出轴向返混系数 Ｄｚ 和径向返混系数 Ｄｒ,研究了液相和气相对规整填料的返混的影响,并就液相和气相对返混影响做了初步解释。实验结果表明：径向扩散系数和轴向扩散系数随气速和液体流速的增大而增大。得到轴向和径向混合系数的彼克列数（ Ｐｅｚ , Ｐｅｒ） 与液相和气相的表观雷诺数（ Ｒｅ１ , Ｒｅｇ） 的关联式。     

热管式固定床鼓泡反应器返混试验研究

为了研究热管式固定床鼓泡反应器的返混问题,采用脉冲法,在一内径为50mm、高800mm,床内充以多孔填料,内插一根16mm×2mm不锈钢-水热管的固定床反应器中,用并流向上的水和氮气进行返混试验研究。利用轴向扩散模型计算反应器轴向Peclet准数,考察了气相流速、液相流速、多孔介质和热管对返混的影响。研究表明反应器中热管的存在加重了返混。     

充填式浮选柱某些参数的相关关系研究

本文叙述了通过对充填式浮选柱模拟装置的测试，分析探讨了柱内的气泡直径与填料片波纹高度、起泡剂用量、充气量等因素之间的相关关系。     

加压下板波纹规整填料塔中液相混合行为

采用脉冲示踪法测量了在0．3MPa、0．5MPa和0．6MPa压力下以及在一系列液速和气速下250Y型孔板波纹规整填料内液相的混合行为。应用时域最小二乘法由实验数据得到了液相的轴向返混系数和轴向有效流速等参数,并以y=aReL^e10^cReG10^dp的形式对轴向Peclet准数进行了关联。本研究补充了目前缺乏的加压操作下规整填料液相混合行为的数据。     

运用CFD模拟浮选柱内的流体流动

根据浮选柱内气液流动的特点,在气速与气含率的径向分布一致的基础上,建立了通用的计算浮选柱内流体流动模型,简便且较准确地模拟出了浮选柱内气液的流动状况,为浮选柱内气体发生器设计以及柱内返混的研究提供了依据和方法。     

孔板波纹填料的结构参数对其性能的影响

在内径Φ30 0mm的填料塔中研究了孔板波纹填料的结构参数对液相轴向混合特性、流体力学和传质性能的影响 .研究结果表明 ,轴向返混参数随开孔率、倾角的增加及盘高的减小而增加 ,填料层压降随开孔率、盘高的增加及倾角的减小而降低 ,传质单元高度随倾角的增加、盘高的减小而降低 ,开孔率对传质单元高度的影响有一个适宜值 .通过对实验数据的回归分析得出了轴向返混参数、填料层压降及传质单元高度的关联式 .该研究结果对孔板波纹填料的开发与设计具有参考价值     

C_5热二聚反应器计算流体力学研究

为了了解现有C5装置所用中空管式反应器内的流场是否为反应所期望的平推流,文中结合理论分析及计算流体力学模拟软件ANSYS CFX 14.5,采用SST湍流模型,发现其入口处存在边界层分离及再附现象。分别对在入口处增加挡板、筛板等轴向阻尼内件和旋转进料的径向阻尼内件进行CFX模拟,并引进一个与速度有关的物理量Jk来表征返混的程度。结果表明:轴向阻尼内件形式在减少返混程度作用上效果不理想,甚至有加重反混的现象,在所研究的轴向阻尼内件中,迷宫式进料效果最优。结果同时表明采用径向阻尼内件旋转进料器可以较大幅度减小反应器内返混程度。     

填料塔中液体轴向返混行为对精馏分离效率影响的理论解

合理地作了一些近似假设，得到能反映液相轴向返混行为的等板高度理论计算公式。精度分析表明，等板高度近似理论解误差很小。在推导理论解的过程中，提出返混影响精馏分离效率的准数———返混特征准数，表明液相轴向返混行为对精馏分离效率的影响随液相轴向返混系数的增加而增加，而随汽相总传质单元高度和液相轴向有效流速的增加而减小。文中还给出了等板高度加长因子随返混特征准数和相平衡常数变化的计算公式和曲线图     

液固磁稳定床中固含率分布与液相返混特性

固含率分布和液相返混系数是液固磁稳定反应器放大与优化所必需的基础数据。采用床层膨胀高度法、光电法及瞬态点源示踪技术,研究了以SRNA-4催化剂为固相的液固磁稳定床中固含率分布和液相返混特性。试验结果表明,固含率轴向分布基本均匀,径向为“扁-陡曲线”分布。固含率随磁场强度和颗粒尺寸的增大而增大,随液体粘度和空塔液速的增大而减小。轴向液相返混系数随磁场强度和液体粘度的增大而减小,随空塔液速和颗粒尺寸的增大而增大。回归得到了固含率和轴向普朗特准数的关联式,预测值与试验值吻合良好。     

浮选柱中液相轴向返混的研究

An experimental study on the axial dispersion of liquid was carried out in a 0.382-m-ID flotation column packed with different structured packings or free of packings. The correlations of axial Peclet numbers with the liquid and gas superficial Reynolds numbers were developed for various packings. Among the packings tested, it is found that in the column packed with 250Y or 350Y packings the axial dispersion is the lowest. The addition of frother can decrease the axial dispersion. By the simulation analysis of the one-dimension dispersion model of packed flotation column, it is found that small axial dispersion, high collection rate constant and low axial liquid velocity can increase the collection zone recovery.     

AXIAL AND RADIAL DISPERSION IN TRICKLE-BED REACTORS WITH TRICKLING GAS-LIQUID DOWN-FLOW

In cocurrent down-flow trickle-bed reactors in the trickling flow regime, the liquid flows down the column in the form of liquid films or rivulets on the surfaces of packings. Depending on system variables such as liquid flow rate, packing size, surface tension, etc., the liquid flow paths can be so well-connected that all packings are completely wetted or some of them remain dry. Dispersion of the liquid phase is confined within, and is controlled by the topology and flow field of, the flow paths. To provide a model for dispersion, flow paths are first developed on a computer-generated, two-dimensional packed column of uniform spheres. Then axial and radial dispersion coefficients are determined based on Monte Carlo simulation. Model predictions are in general agreement with experimental data in the literature.     

Modeling of vanillin production in a structured bubble column reactor

Vanillin is an important flavour. Semi-synthetic vanillin can be produced by the oxidation of lignin. Experimental studies leading to vanillin production in a batch reactor and a structured bubble column reactor (SBCR) lead us to the conclusion that the SBCR could have non-idealities such as dispersion. The radial and axial liquid-phase dispersion within the packed criss-crossing sandwich structures of Mellapak-750Y had been studied. A 2D model accounting for axial and radial velocities and dispersion was formulated and solved. The model predictions were compared with that of an experimental residence time distribution curve. The axial dispersion coefficient of the liquid phase is of the same order of magnitude as the radial dispersion coefficient. The reaction kinetics available in literature is adopted for the present study. Model for the SBCR was formulated and simulated using commercial modeling software. Simulation experiments were conducted in a SBCR. The effect of the following parameters on the yield of vanillin is studied: lignin concentration, lignin molecular weight, oxygen partial pressure and reaction temperature. It can be said that lignin molecular weight is a crucial parameter in vanillin production.     

一种新型浮选柱的数值模拟及性能研究

自主研制了一种新型多级规整填料浮选柱,应用计算流体力学软件FLUENT6.3.26进行数值模拟计算,对其内部的气液两相流动进行了考察,采用了欧拉-欧拉多相流模型,对气相的模拟采用单一气泡尺寸,液相湍流采用了标准k-ε模型,两相之间的动量传输仅考虑曳力作用。通过模拟,获得了不同实验条件下浮选柱内部的气液速度场分布、气含率分布等,对部分模拟结果进行了定量比较。结果表明随着气相流量的增大,浮选柱内部气含率增大,液体循环速度增大,从而气液之间混合更加充分,这对于提高浮选柱的分选效率和设备的放大有重要意义。在唐山钱家营开滦煤矿选煤厂进行了以其煤浆为原料的浮选性能的测试,在气体1.25 m³/h,进料0.05 L/h条件下20 min停留时间获得了精煤灰分10.28%,尾煤灰分43.39%,精煤产率52.53%的指标,与该厂浮选精煤灰分10.58%相接近。     

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 influence of frother types and concentrations on fine particles’ entrainment using column flotation

Entrainment which is the characteristic feature of fine particles is closely related to water recovery. It is based on the changes depending on the establishment of linear relationship between water recovery and solid recovery. This paper deals with the investigation of the effect of frother types and concentrations on fine particles’ entrainment using column flotation. Entrainment of fine particle using a mixture of artificial ore (celestite:calcite; 1:1) was investigated in column flotation. In a two-phase system (water/air), the variation of bubble diameters and gas hold-up with a superficial air rates using different frother types and concentrations were tested. The results showed that the frother types and concentrations had significant effect on the grade and recovery, superficial air rate, gas hold-up and fine gangue entrainment. Entrainment factors for frother types and concentrations were compared in flotation column. Kirjaveinen^[11] model was used for describing the specific entrained factor (P_i) of hydrophilic particles. It has been found that Kirjaveinen model supports the results of this study.     

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.     

固定床内径向扩散研究

在直径为２６７ｍｍ的５Ａ分子筛固定床上，采用稳态有限源示踪技术，利用计算机数据采集系统，测定了不同流速下床层内部截面上示踪气体的浓度分布数据。并分别利用稳态有限源和稳态点源示踪条件下扩散模型的解析解，获得床层内的径向扩散系数值。结果表明，两种处理方法所获得的径向扩散系数值大致相等，且在实验条件范围内，当Ｒｅ数较小时，径向扩散系数值与分子扩散系数值相当，随着Ｒｅ数的增加，径向扩散系数值逐渐增大，最后几乎与流速成正比。文中还讨论了轴向扩散系数值对径向扩散系数计算结果的影响。