错流旋转填料床气相压降特性

旋转填料床的气相压降是旋转填料床应用和设计的一项重要指标。在气液两相错流流动条件下,利用空气-水系统对错流旋转填充床的气相压降进行分段模型化和实验研究。按照错流旋转填料床气体流动的路径将气相压降分为进口压降、填料层压降、集气段旋转动能转化压降和出气段压降。推导出压降与操作工况的关联式,其计算值与实测值吻合较好。实验表明错流旋转填料床的气相总压降与气体流量、旋转床转速、液体流量有关。在高转速和小气量的条件下,气相压降随气量增大先下降后上升;其他情况随气量增大而上升。错流旋转填料床气相压降随转速上升而下降,在小气量情况下转速对气相压降有明显影响。气相压降随进液量的增大而增大,当旋转填料床在低转速时进液量对气相压降有明显影响。     

Studies on frictional pressure drop of gas-non-Newtonian two-phase flow in a cocurrent downflow bubble column

An exclusive study has been done on experimental investigation of the two-phase frictional pressure drop with air-non-Newtonian liquid (CMC solutions) system in cocurrent downflow bubble column. The effects of gas and liquid flowrate on two-phase frictional pressure drop have been illustrated. An attempt has been made to fit the experimental two-phase frictional pressure drop data by modified Lockhart and Martinelli correlation and Aoki correlation. In another approach, friction factor method was adopted to correlate the experimental results in terms of dimensionless groups of the operating and system variables and the predicted values were found to be in good agreement with the experimental result. The experiments were performed in the bubbly flow regime because of its stability and uniformity.     

并流旋转床压降与传质特性的研究

利用水-空气系统对并流旋转床的气相压降进行了研究,并与逆流旋转床气相压降进行了对比。研究结果表明：并流较逆流旋转床的气相压降低;并流旋转床的气相压降随气体流量的增大而增大,随液体流量的增大而减小,随转速的增大明显降低;而逆流旋转床的气相压降随转速的增大明显升高。利用水吸收SO2的实验对并流旋转床的传质特性进行了研究。研究结果表明：并流旋转床填料层内各点的体积传质系数随着气体流量、液体流量和转速的增大而增大;填料层半径由70mm增大至90mm时,并流旋转床的体积传质系数迅速增大,而后并流旋转床的体积传质系数随半径的增大而减小。对并流和逆流旋转床填料层内体积传质系数进行了对比。结果表明：填料层半径由70mm增大至130mm时,并流旋转床的体积传质系数较逆流时大;当半径大于130mm后,逆流旋转床的体积传质系数大于并流旋转床的体积传质系数,且随半径增大而增大。根据研究结果,提出了降低系统压降的设想,即并流与逆流旋转床串联操作。     

A general model for pressure drop prediction across a rotating packed bed

Although rotating beds show promise for intensified separations, the fundamentals of their hydrodynamics are still poorly understood. In many operating conditions, pressure drop in an irrigated bed can be considerably lower than that across a dry bed. Previously published correlations don’t provide good prediction of these phenomena. In this research, a semi-empirical correlation is developed to predict the pressure drop across the rotating packed beds. The results show the agreement of predicted pressure drop with the experimental data is acceptable. This model can also predict the pressure drop unexpected phenomena of higher pressure drop in dry beds than in wet beds.     

带内置水平管的大颗粒振动流化床流体力学研究

以大颗粒MAP（磷酸-铵）为试验物料对带内置水平管的大颗粒振动流化床流体力学进行了试验研究,结果表明,振动的引入对床层临界压降有明显的降低作用;同样床层条件下振动频率越大床层临界压降越低,振幅的改变对床层压降影响不大;低气速下振动使床层孔隙率降低而导致压降高于普通流化床;在带内置水平管的大颗粒振动流化床中,振动对大粒径颗粒的影响小于小粒径颗粒;由试验拟合出经验公式,与试验数据吻合良好。     

喷动流化床最大喷动压降的多因素影响与关联

基于截面200 mm×20 mm,高1600 mm,锥角60°的矩形喷动流化床,以二组分混合颗粒、单一组分球形颗粒及非球形颗粒为物料进行最大喷动压降的实验研究.结果表明,最大喷动压降随静止床高、颗粒密度、颗粒球形度及二组分混合颗粒体系中沉积组分分率增加而增大,随流化气速增大而减小;增大颗粒粒径或喷口宽度,呈现先减小后增...     

Hydrodynamics of a cocurrent downflow of gas and foaming liquid through the packed bed. Part II. Liquid holdup and gas pressure drop

In the present study the results of experiments have been presented whose aim was to determine the values of liquid holdup as well as gas pressure drop through the packing for systems foaming under the pulse flow regime. On the basis of 245 experimental points for the pulse flow regime the verification of the models describing the hydrodynamics of the system has been performed. Attention was focused on the models of Benkrid et al. (Chem. Eng. Sci. 52 (1997) 4021), Pina et al. (AIChE J. 47 (2001) 19) and Fourar et al. (Chem. Eng. Sci. 56 (2001) 5987). It has been concluded that none of the models analysed describes the hydrodynamics of the foaming systems with enough accuracy. Next, based on our own data-base the verification has been carried out of parameters of Benkrid et al. (Chem. Eng. Sci. 52 (1997) 4021) (‘drift flux’ model for _L and boundary layer model for ΔP/H) and Pina et al. (AIChE J. 47 (2001) 19) models as well as the estimation of the values of F*-functions of Fourar et al. (Chem. Eng. Sci. 56 (2001) 5987) model. Using as the criterion the accuracy of estimation of the values of (ΔP/H) the best results have been obtained by applying Fourar et al. (Chem. Eng. Sci. 56 (2001) 5987) model (for the Ergun constants determined experimentally). The introduction of the estimated F*-functions into the equations of the model (Eqs. 11 and 12) makes it possible to estimate the liquid holdup with the average absolute relative error not exceeding 9.8% and the pressure drop with an error less than 26%.     

Minimum fluid flowrate,pressure drop and stability of a conical spouted bed

A model for calculating the minimum spouting flowrate and pressure drop in a conical spouted bed has been developed and described in our previous paper (Had?ismajlovi et al., 1986). In the present work, this model was examined at a wider range of experimental conditions and it was found that measured and predicted values of the minimum spouting flowrate and pressure drop differed by about 10.3% and 20.0%, respectively. It is shown that the spouted bed in a conical column is stable when the inlet tube diameter is less than 25 particle diameters.     

错流旋转填料床气相压降特性研究

旋转床的气相压降是旋转床工程设计的一项重要指标。笔者利用空气,水系统对错流旋转填料床的气相压降进行实验研究。结果表明：在实验范围内,错流旋转床压降是逆流旋转床的十分之一;对错流旋转床压降影响较大的是转速和气量,与液流量几乎无关。     

双喷嘴矩形导流管喷动床喷动压降

引言 传统的柱锥形喷动床(CSBs)的应用受到一些因素的限制,例如处理物料能力、起始压力大及难以放大等,为此,Romankov等[1]最早提出了长方形截面的矩形喷动床结构,来克服CSBs的缺点.此后,Rocha等[2]用矩形喷动床进行了片剂包衣的研究.     

General correlation for pressure drop through randomly-packed beds of spheres with negligible wall effects

Pressure drop in fixed beds has been studied for over a century and a large number of conflicting correlations exist in the literature. Contributing factors to these differences include the use of particles of different shapes, the presence of wall effects in beds of low tube-to-particle diameter ratio (N) and parameter fitting over limited ranges of modified Reynolds number ${\mathit{Re}}_m=\frac{\mathit{\rho v}{d}_p}{\mu \left(1-\epsilon \right)}$. The present work, in contrast, considers the entire Reynolds number range for perfect spheres in unbounded (high-N) random-packed beds. An asymptote-based correlation has been developed based on published data for extremely high ${\mathit{Re}}_m$ and on new particle-resolved computational fluid dynamics (PRCFD) results for extremely low ${\mathit{Re}}_m$. The resulting equation is given by: $\frac{∆P}{L}\frac{d_p}{\rho v^2}\frac{{\epsilon }^3}{\left(1-\epsilon \right)}=\frac{160.0}{{\mathit{Re}}_m}+\left(0.922+16{\mathit{Re}}_m^{-0.46}\right)\frac{{\mathit{Re}}_m}{\left({\mathit{Re}}_m+52\right)}$. This equation fits a literature data set of 541 points with average error 5.66%, and shows correct limits for both high and low ${\mathit{Re}}_m$.     

两级泡沫镍填料旋转填充床压降及精馏研究

在两级逆流式旋转填充床(TSCC-RPB)的基础上,采用简单结构的整体泡沫镍填料替代其相对复杂的动静环结构填料,从而构建新型两级整体泡沫镍填料旋转填充床(TSNF-RPB)。采用空气-水体系,研究了TSNF-RPB的压降特性,并以甲醇-水为工作体系,对TSNF-RPB进行了连续精馏实验研究。结果表明:虽然TSNF-RPB的湿床压降比TSCC-RPB高出了20%—30%,但TSNF-RPB的分离效率提高了20%,且TSNF-RPB结构简单、安装方便,更利于工业推广应用。     

错流移动床的压降特性

在矩形移动床内考察了颗粒下移速度、颗粒堆积状态及空腔生成和长大发展过程等因素对压降的影响. 在错流气体速度为0.09~1.35 m/s、颗粒下移速度为0.95~9.68 cm/min的较大变化范围内进行了实验研究. 结果表明,颗粒下移速度对压降几乎没有影响;当错流气速足够大时移动床内将出现"空腔"和"贴壁"等现象,空腔的发展过程造成压降随时间出现稳定、微波脉动和大幅波动3种变化;欧根公式适用于低错流气速时的移动床压降;高错流气速下空腔出现了"生成-长大-塌落-流化"的循环变化过程. 在实验基础上建立了有空腔时的移动床压降模型,并对空腔尺寸进行了无因次关联,其床层压降的计算结果与实验值相符.     

Fundamental investigation of plug conveying of cohesionless particles in a vertical pipe (pressure drop and friction of a stationary plug)

A stationary packed bed of cohesionless particles is set up in a vertical pipe for the fundamental study of plug conveying. The effect of flow acceleration or deceleration on the pressure drop of the plug is investigated first. It is found that the pressure drop increases due to the flow acceleration and vice versa. Next, the following three kinds of experiments were made for the study of friction characteristics: 1. Friction between the plug and moving wall without air flow, 2. Friction between the plug and wall with downward air flow, 3. Friction between the plug and wall with upward air flow. The results are compared with the theory established in powder mechanics. The state of stress being of the active or passive case is discussed. Finally the problem of particles raining down from the back of the plug is studied. It is shown that the air velocity necessary to support the particles can be calculated based on a simple analysis of pressure distribution around the particles.     

气-固微型流化床压降特性及最小流化速度的实验研究

在内径3～20 mm的4个气-固微型流化床中,分别考察了A类和B类两种类型颗粒的流化特性,同时研究了床几何结构、操作条件、物相性质等各因素对其最小流化速度的影响.结果 表明,气-固微型流化床中的床层压降特性与颗粒类型密切相关,不同的流动状态下两种类型颗粒的流动特性存在显著地差异.在固定床阶段,与B类颗粒相比,A类颗粒与...     

Prediction of pressure drop in a modified gas-liquid downflow bubble column

A model for pressure drop in the ejector induced downflow bubble column based on mechanical energy balance within the framework of dynamic interaction of the phases has been formulated. The model includes the effect of bubble formation and form drag at interface on the pressure drop. It provides a functional form of equation for correlating pressure drop. The theoretical model proposed in the present study appears to predict the pressure drop satisfactorily for gas-liquid dispersed flow in the concurrent gas-liquid downflow bubble column.     

Experimental study of a cocurrent upflow packed bed bubble column reactor: pressure drop, holdup and interfacial area

Gas–liquid interfacial areas have been determined by means of chemically enhanced absorption of CO₂ into DEA in a packed bed bubble column reactor with an inner diameter of 156 mm. The influence of the gas velocity and particle diameter on the interfacial areas, pressure drops and liquid holdups has been investigated. For both packings the limiting values of the gas velocities have been determined above which the interfacial areas and liquid holdups stabilize. In particular gas channelling has been found, which is less pronounced in the bed of larger particles.     

气体干法净化旋流吸附耦合设备压降特性

气体干法净化旋流吸附耦合设备将旋流分离和移动床吸附/过滤分离有机结合,可适应较宽的温度范围,为高温气体净化提供了一种新思路。在不加尘及不同的移动床循环速率和旋风入口气速下对该设备进出口静压差进行了测量和分析。实验结果表明,设备静压差在整个运行过程中较为稳定,有较强的可预测性,无量纲标准偏差维持在0.4%以内;实验范围内,移动床循环量的大小对设备静压差没有影响;设备压降与旋风入口气速呈现出良好的二次方程（抛物线）关系;将设备实际压降划分为进口管路沿程摩擦损失、入口天圆地方摩擦损失、旋流体摩擦损失、内置移动床摩擦损失和出口管路沿程摩擦损失五个部分;获得了旋流体摩擦损失及设备实际压降与入口速度头的关联方程;该设备的阻力系数与普通旋风分离器相比,没有明显增大;初步加尘实验确认了旋风壳体与移动床之间旋流作用的存在,为进一步结构优化提供了参考。