Liquid dispersion,gas holdup and frictional pressure drop in a packed bubble column at elevated pressures

The gas holdup, frictional pressure drop and liquid dispersion have been investigated in a packed bubble column at elevated pressures for the air–water system. The bubble column, which had an internal diameter of 0.15 m and which was packed with 15 mm plastic Pall rings was operated in the semibatch mode. The operating pressures ranged from 0.1 to 0.66 MPa. It was found that increasing the pressure increases both the gas holdup and the dispersion coefficient. In contradiction to the results obtained from packed bubble columns fed with a continuous net flow of liquid, a maximum point of the frictional pressure drop was observed at the transition point between bubble and pulse flow region.     

Minimizing axial dispersion in narrow packed column using superhydrophobic wall

The scope of minimizing dispersion in narrow packed column using superhydrophobic (SH) wall is assessed experimentally with implications in analytical techniques such as liquid chromatography. The study includes devising a packed column (7-19 mm) with lotus leaf pasted on the inner wall and establishing a gravity driven flow through it. The flow dispersion is characterized based on the residence time distribution study of the column. The results are compared against similar flow through smooth packed column. Experimental results reveal the influence of two factors: column diameter as well as the wall features, superhydrophobic or smooth. For similar surface features, the axial dispersion reduces with decrease in column diameter due to the increase in voidage, which leads to plug flow. For the same diameter, between smooth and superhydrophobic, effects of slip in the latter reduce the dispersion significantly. Thus, the introduction of superhydrophobic narrow columns can play a crucial role in minimizing dispersion in analytical techniques.     

Liquid distribution in a packed column

The effects of liquid flow rate, packing size, surface tension and viscosity of irrigation liquid on the liquid spread factor are studied, and the values of the liquid spread factor are correlated for a wide range of packing size.The distribution of the liquid in a packed column is predicted by using a diffusional model with a new boundary condition. The boundary condition at the wall is based on the assumption that the penetration of the liquid into the wall takes place by the similar mechanism to the transport phenomena considering the dependence of the equilibrium wall flow rate on the liquid flow rate. The experimental results agree well with the theoretical ones for pure water and the surfactant solution.     

规整填料塔的壁流研究

以新的观点分析了填料塔内壁流产生、发展且最终达到平衡的过程。通过数学推导，得到了一个三参数壁流模型，并在实验基础上，进行模型的参数估计，从而求得了八种规整填料的壁流曲线。研究认为，壁流量的大小是填料塔内诸多因素综合影响的最终结果，而填料自身的几何形状和加工精度，是其中最重要的影响因素。通过实验，测取了这些填料的平衡壁流量，其中某些大于４８％。     

Concentration profiles in a packed distillation column

Concentration profiles in a pilot plant-sized packed distillation column were measured by sampling both the liquid and the vapour in ten positions along the column. The results were compared with the profiles obtained by computer simulation from the plug flow and backmixing models. It was found that the stagewise backflow model reproduced the experimental profiles well. The corresponding mass transfer coefficients were greater than those calculated for the plug-flow model and could be better correlated with the vapour velocity. However, the corresponding backmixing coefficients were rather low, the equivalent eddy diffusivity in the liquid phase being of the order of 10^?3m²/s.     

Identification of a packed absorption column

A method is presented for the identification of parameters in the partial differential equations describing the dynamic behaviour of a certain class of two phase flow processes. This method is an extension of a procedure for the identification of single phase flow processes which were introduced in a previous paper. The method is applied to the identification of two parameters in the five simultaneous partial differential equations describing the behaviour of a packed absorption column being used to remove carbon dioxide from air with an aqueous solution of monoethanolamine. These parameters were determined from a single experimental step response. The approach employed was to reduce the partial differential equations to two coupled systems of ordinary differential equations by the method of characteristics. Once in this form the identification problem could be formulated as two coupled boundary value problems and solved with the use of quasilinearization.     

Effective interfacial area and liquid and gas side mass transfer coefficients in a packed column

The theory of gas absorption accompanied by fast pseudo-mth order reaction was used to obtain values of effective interfacial area in a packed column, irrigated with aqueous solutions and provided with 1 in. ceramic Raschig rings, 1 in. P.V.C. Raschig rings, 1 in. ceramic Intalox saddles, 1 in. polypropylene Intalox saddles, 1 in. stainless steel Pall rings and 1 in. polypropylene Pall rings. The values of liquid side mass transfer coefficient were obtained by physical absorption of carbon dioxide in water. In addition, the values of gas side mass transfer coefficient for a range of gas and liquid flow rates were obtained.     

填料塔液泛的声发射测量

利用声发射技术采集填料塔在不同操作状态下壁面处的声发射信号,结合标准差分析、频谱分析和小波分析研究填料塔在不同操作状态时的声发射信号特征,提出填料塔液泛气速的声发射测量判据。以空气-水体系为例考察不同液体流量下的液泛气速,发现声发射信号标准差对液泛气速的预测值与压降法的预测值接近。比较不同操作条件下的声发射信号的功率谱,发现填料塔发生液泛时功率密度最大的峰从50 kHz 和60 kHz 转移到在25 kHz附近;进一步将声发射信号在0~300 kHz 频率范围内做7 尺度小波分解,当气速到达液泛气速时特征信号频段G₁(d₄、d₅)的声发射信号能量分率迅速增大。G₁尺度声发射信号能量分率对液泛气速的预测值与压降法的预测值接近。声发射技术作为一种非侵入式的检测手段,能够实现液泛的实时监控,具有良好的应用前景。     

Gas-solid trickle flow hydrodynamics in a packed column

The pressure gradient and the static and the dynamic hold-up have been measured for a system consisting of a Fluid Cracking Catalyst (FCC) of 30–150 × 10⁻⁶ m diameter, trickling over a packed bed and with a gas streaming in countercurrent flow. The experiments were carried out at ambient conditions using a glass column of 25 × 10⁻³ m diameter. The packing material consisted of 8 × 8 × 3 mm ceramic Raschig rings, a mixture of 7 × 7 × 1 mm glass Raschig rings and 5 × 5 mm catalyst pellets and of stacked Kerapak ceramic mixing units of Sulzer, each unit 50 mm long and 25 mm in diameter. Four different gases have been tested. A correlation for the pressure gradient in the preloading region is derived based on the Ergun equation and taking into account the internal gas recirculation due to the solids trickles. The void fraction of the trickles is found to be independent of the physical properties of the gas phase. The behaviour of the GSTF-system in the preloading regime and the phenomena of loading and flooding are discussed. A correlation is given which relates the boundary between preloading and loading with the particle and gas properties and the solids flow rate.     

Solubility and diffusivity of solvents by packed column inverse gas chromatography

Inverse gas chromatography was used with solid polymer particles in packed columns to measure polymer-solvent solubility and diffusion. A new model for this IGC technique has been developed and used to obtain experimental results for n-pentane, isopentane, 1-hexene, n-hexane, and 1-octene solvents in polymer beads of polyethylene. The conditions were measured for solvents at infinite dilution, and experimental data were obtained for the binary polymer-solvent systems in a temperature range from 70 to 100 °C.     

填料型饱和热水塔数学模拟

本文对填料型饱和热水塔最佳工况模拟,对该类型塔的计算机数学模拟进行了讨论。     

Mass transfer in a packed extractive distillation column

The kinetics of mass transfer in the extractive distillation of the benzene–heptane mixture (which imitates the catalytic reforming product mixture) in the presence of N-methylpyrrolidone as the separating agent has been investigated. The separating agent exerts an effect on the overall efficiency of the process. The partial heights of transfer units in the vapor and liquid have been determined, and equations for calculating these parameters have been set up.     

Axial dispersion in packed beds

Behaviour of axial dispersion in packed beds is made clear from the properties of the equation of continuity. New dispersion data are added to relate liquid data with gas data in the Stokes flow regime. A special device to send a plane impulse of tracer liquor was developed. A correlation has been given for a wide range of flow and dispersion in packed beds.     

Radial porosity distribution in cylindrical beds packed with spheres

Experimental determinations of radial porosity for cylindrical beds packed with spheres are reported. The data indicate that, for a wide range of bed and sphere sizes, porosity varies significantly and regularly near the container wall. For uniformly sized spheres, the oscillations in porosity can be detected up to a distance of about 5 particle diameters from the wall. For mixtures of spheres of two sizes, regular oscillations are detected only up to 2 or 3 diameters from the wall and for three sizes the effect of the wall is observed only within a distance of 1 particle diameter.