Mass transfer characteristics in a rotating packed bed with split packing

The rotating packed bed (RPB) with split packing is a novel gas–liquid contactor, which intensifies the mass transfer processes controlled by gas-side resistance. To assess its efficacy, the mass transfer characteristics with adjacent rings in counter-rotation and co-rotation modes in a split packing RPB were studied experimentally. The physical absorption system NH3–H2O was used for characterizing the gas volumetric mass transfer coeffi-cient (kyae) and the effective interfacial area (ae) was determined by chemical absorption in the CO2–NaOH sys-tem. The variation in kyae and ae with the operating conditions is also investigated. The experimental results indicated that kyae and ae for counter-rotation of the adjacent packing rings in the split packing RPB were higher than those for co-rotation, and both counter-rotation and co-rotation of the split packing RPB were superior over conventional RPBs under the similar operating conditions.     

规整填料传质性能计算的研究进展

综述了规整填料传质性能的计算方法和模型,并对这些模型的理论基础和适用条件进行了分析和比较。归纳了近年来对于传统规整填料传质模型的修正和扩展,并对影响传质性能的有效比表面积的经验关联式进行了讨论,指出了规整填料传质性能研究方面进一步的探索方向和应改进的若干问题。     

Performance characteristics of a new spherical metal mesh packing

Various tests and analysis on hydrodynamics and mass transfer properties show that, the newly invented spherical metal mesh packing (SMMP) has excellent properties from three aspects: (i) high void space (∼99%) and lower material cost; (ii) high mass transfer efficiency; (iii) easy installation, good liquid distribution, and prevention of wall flow. Moreover, SMMP is a type of isotropic spherical unit with numerous hollow holes, which realizes the regularization of random packing. The results indicate the potential of developing high-efficiency and energy-saving SMMP-based equipment.     

Gas and liquid phase mass transfer within KATAPAK-S structures studied using CFD simulations

The gas phase mass transfer in the empty channels, and the liquid phase mass transfer within the catalyst-packed channels, of the criss-crossing sandwich structures of KATAPAK-S have been studied using computational fluid dynamics. Due to the “upheaval” caused by the flow splitting at the cross-overs, the mass transfer coefficient is significantly larger than that for fully developed flow in a single tube.     

波纹填料技术的进展与多孔基材的开发

简述波纹填料的发展历程,强调复网借助毛细力提高分离效率的重要意义,提出“液体多向扩散”的理论观点,介绍金属复合板网波纹填料的研究进展。     

Liquid-phase mass transfer within KATAPAK-S structures studied using computational fluid dynamics simulations

The liquid-phase mass transfer within the catalyst-packed criss-crossing sandwich structures of KATAPAK-S has been studied with the use of computational fluid dynamics. Due to the “upheaval” caused by the flow splitting at the crossovers, the mass transfer coefficient is about 40% times larger than for fully developed laminar flow in a single, packed tube.     

Hydrodynamics and mass transfer in gas-liquid flow through static mixers

The objective of this study was to characterize the two-phase flow hydrodynamic behaviour and mass transfer in a static mixer in a horizontal pipe. Different arrangements of elements of the static mixer were tested and their performances compared. The pressure drop, bubble diameters and mass transfer coefficient were measured. The influence of operating conditions was also studied. A different correlations are proposed and compared with other correlations found in the literature.     

A corrugation geometry based model for efficiency of structured distillation packing

Although the structured packing is a well established gas–liquid contacting device, the understanding of its function is insufficient and often leads to poor exploitation of the available phase separating potential. This is a consequence of a rather superficial approach to modelling the packing performance through the years resulting in a lack of information on the nature and extent of interaction between counter-currently flowing gas and liquid phases and the micro and macro geometry of a rather ordered structure with a pronounced flow discontinuity at the transition among packing elements. This paper addresses the relation between the fluid-dynamics imposed by packing geometry and the mass transfer efficiency, and introduces a performance prediction method which does not require packing specific constants to describe mass transfer coefficients of phases.     

Influence of Chitosan and Chitosan Derivatives on Hydrodynamics and Mass Transfer in a Bubble Contactor

The behavior of chitosan and two kinds of chitosan derivatives in carbon dioxide absorption in a bubble column contactor is analyzed. The effects of absorption type (physical or chemical), polymer type, concentration, and liquid‐phase physical properties on hydrodynamics (bubble size, gas holdup, and specific interfacial area) and mass transfer (absorption rate and mass transfer coefficient) are evaluated.     

Region-dependent mass transfer behavior in a forced circulation airlift loop reactor

The contribution of local regions to global mass transfer holds the key to optimization and scale-up of a reactor. Extensive study has been conducted to investigate gas-liquid mass transfer occurring in the internal airlift loop reactor, but mostly restricted to global mass transfer performance. A cold model forced circulation internal airlift loop reactor was employed and divided into six regions in which dissolved oxygen concentration in slurry and mass transfer interfacial area were measured respectively. Different models were utilized to calculate volumetric mass transfer coefficient. Contributions of individual region to global mass transfer performance were calculated and compared. It was found that mass transfer coefficient and mass transfer interfacial area of individual region increases with increasing superficial gas velocity and slurry feed flowrate. The feed affected region has the greatest mass transfer coefficient and volumetric mass transfer coefficient, contributing more than 30% to global mass transfer in most operating condition. Mass transfer interfacial area is close in the gas distributor region, feed affected region and the gas-slurry separator region. In the present work, circulating bubbles are rare and contribute negligibly to the global mass transfer. Global volumetric mass transfer coefficient is close to that of the gas-slurry separator region, ranging from 0.02 to 0.1 1/s. Comparison of k_La is made between this work and literatures, suggesting a great improvement of mass transfer due to external liquid circulation.     

Hydrodynamic‐Analogy‐Based Modeling Approach for Distillative Separation of Organic Systems with Elevated Viscosity

A modeling approach based on hydrodynamic analogies is applied to predict the influence of elevated viscosity on the separation efficiency of distillation processes in structured packed columns. An advantage of this approach compared to traditional models based on the film theory is that separation columns can be described without empirical mass transfer coefficient correlations. The separation efficiency was evaluated for two systems with distinct viscosities at different gas and liquid loads and various operating pressures. Simulated concentration profiles and height of a theoretical plate (HETP) values were compared with the data obtained from own experiments. The developed model is capable of correctly predicting the differences in the HETP values of the two evaluated systems.     

滴流床小颗粒催化剂滴流区和脉动流区传质的研究

本文研究了滴流床小颗粒催化剂在滴流区和脉动流区的气相容积传质系数k_Gα,气液接触有效界面积“α”和脉动流形成时分散气泡的平均直径d_b。实验表明:不同流区的传质与流型和流动介质的能量损失有关。强化传质会增加流动介质的能量消耗及减小催化剂粒度。     

改性塑料规整填料的流体力学和传质性能研究

主要研究了不同比表面积和开孔率塑料规整填料表面处理前后的流体力学和传质性能。结果表明：经过表面改性后,传质性能可提高约20%～35%,开孔填料经表面改性后阻力不会增加,并且在低喷淋密度时传质效率提高显著。     

CONTINUOUS PHASE MASS TRANSFER COEFFICIENTS FOR SINGLE DROPLETS MOVING IN AN INFINITE DROPLET CHAIN

Continuous phase mass transfer coefficients have been measured for a stream of drops falling freely in a stagnant liquid. Drop streams were produced by a dripping method and by a jet breakup method. Water and isobutanol, mutually saturated, were used as the dispersed and the continuous phases, respectively. Sodium hydroxide was used as solute and was transferred from the bulk solution of isobutanol to water drops which was initially free of solute. Resistance to the mass transfer was observed to be on the continuous phase side. The mass transfer coefficient and terminal velocity of drop streams were measured experimentally. The experimental results show that the mass transfer coefficient in the drop stream is affected by the shielding effect of the previous drops. An approximate analysis was conducted for the shielding effect of a drop stream on mass transfer coefficient caused by the superposing wakes produced by each drop in the stream. The resulting equation describes the effect of interdrop distance on mass transfer coefficient in the continuous phase side and the experimental data have been correlated as K,/U_t ^0.5 versus interdrop distance /. Good results were achieved and also can be applied to other liquid-liquid systems.     

新型复合塔板JCPT的性能及工业应用

对一种新型高效复合塔板———喷射式并流填料塔板（ＪＣＰＴ） 分别采用空气水系统和乙醇水系统进行了流体力学和传质性能研究,并给出了适用于工业设计的板压降、漏液、雾沫夹带等性能参数的关联式。同新型垂直筛板（ＮＶＳＴ） 相比,ＪＣＰＴ具有压降低、操作弹性大、通量大、效率高等优点。同时给出了工业应用实例。     

The Effect of Size and Concentration of Nanoparticles on the Mass Transfer Coefficients in Irregular Packed Liquid–Liquid Extraction Columns

This investigation explored the effects of nanofluids on mass transfer enhancement using an irregularly packed liquid–liquid extraction column and the chemical systems of water–acetic acid–toluene. SiO₂ nanoparticles with sizes of 10, 30, or 80 nm are dispersed in toluene–acetic acid to produce nanofluids with different volume fractions of 0, 0.01, 0.05, and 0.1 vol.%. The effects of nanoparticle size and concentration on dispersed phase mass transfer coefficient were discussed based on the experimental data. This is for the first time that the effect of nanoparticle size is studied in liquid–liquid extraction systems. It was found that the mass transfer enhancement was more significant in nanofluids with smaller particles. It was also observed that mass transfer coefficient is larger in nanofluids compared to that in dispersed phase without nanoparticles, with a peak enhancement at a nanoparticle volume fraction of 0.05 vol.% for 10-nm particles and 0.01 vol.% for 30- and 80-nm particles. The maximum mass transfer coefficient enhancement was approximately 42% at 0.05% concentration of nanoparticles using smaller particles (10 nm). Finally, a novel correlation for prediction of effective diffusivity in the presence of nanoparticles has been proposed, which is a function of nanoparticle size and its concentration. The main advantage of this approach is that the principal effect of these two parameters is considered in correlation without which the experimental data could not be fitted with an acceptable accuracy.     

A new approach to fluid separation modelling in the columns equipped with structured packings

An analogy between the flow patterns in real separation columns equipped with structured packing and film flow is used to develop a new modelling approach. The packing is represented as a bundle of channels with identical triangular cross section. The dimensions of the channels as well as their number are derived from the packing geometry. The channel inner surface is wetted by a liquid flowing downwards, whereas the rest of the volume is occupied by a countercurrent vapour flow. Both phases are assumed to be totally mixed at regular intervals, determined by the corrugation geometry of the packing. The mathematical model is based on a set of partial differential equations describing hydrodynamics and mass and heat transport phenomena. These equations are complemented by the conjugate boundary conditions at the phase interface. A numerical solution of the model yields velocity profiles as well as concentration and temperature fields throughout the column. The model is verified using experimental data for a binary distillation in a column equipped with Montz-Pak A3-500.     

A dimensionless model for predicting the mass‐transfer area of structured packing

The mass‐transfer area of nine structured packings was measured in a 0.427 m ID column via absorption of CO₂ from air into 0.1 kmol/m³ NaOH. The mass‐transfer area was most strongly related to the specific area (125–500 m²/m³), and liquid load (2.5–75 m³/m²·h). Surface tension (30–72 mN/m) had a weaker but significant effect. Gas velocity (0.6–2.3 m/s), liquid viscosity (1–15 mPa·s), and flow channel configuration had essentially no impact on the mass‐transfer area. Surface texture (embossing) increased the effective area by 10% at most. The ratio of mass‐transfer area to specific area (a_e/a_p) was correlated within the limits of ±13% for the entire experimental database ${{a_{\rm{e}} } \over {a_{\rm{p}} }}= 1.34 \left[ {\left( {{{\rho _{\rm{L}} } \over \sigma }} \right)g^{1/3} \left( {{Q \over {L_{\rm{p}} }}} \right)^{4/3}} \right]^{\,0.116}$ . © 2010 American Institute of Chemical Engineers AIChE J, 2010