Liquid-solid mass transfer in a rotating packed bed reactor with structured foam packing

A rotating packed bed (RPB) reactor has substantially potential for the process intensification of heterogeneous catalytic reactions. However, the scarce knowledge of the liquid–solid mass transfer in the RPB reactor is a barrier for its design and scale-up. In this work, the liquid–solid mass transfer in a RPB reactor installed with structured foam packing was experimentally studied using copper dissolution by potassium dichromate. Effects of rotational speed, liquid and gas volumetric flow rate on the liquid–solid mass transfer coefficient (k_LS) have been investigated. The correlation for predicting k_LS was proposed, and the deviation between the experimental and predicted values was within ± 12%. The liquid–solid volumetric mass transfer coefficient (k_LSa_LS) ranged from 0.04–0.14 1⁻¹, which was approximately 5 times larger than that in the packed bed reactor. This work lays the foundation for modeling of the RPB reactor packed with structured foam packing for heterogeneous catalytic reaction.     

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.     

Distillation studies in rotating packed bed with split packing

Rotating packed bed (RPB) with split packing has been developed recently to overcome the limitation of negligible tangential slip velocity between vapor and packing obtained with single rotating packing element of conventional RPB design. This work evaluates the performance of this contactor for separation of binary mixture methanol–ethanol by distillation. Experiments were carried out at total reflux condition. The height equivalent of a theoretical plate (HETP) of 2.9 cm was obtained at F-factor = 0.6 (m/s) (kg/m³)^0.5 and rotor speed of 1100 rpm. Comparison with distillation studies reported for this system in the literature indicated that the mass transfer performance of this rotor design was superior to that of conventional RPB. Analysis of the experimental data also suggested that the rotor speed influenced the overall volumetric mass transfer coefficient to a greater degree in this design.     

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。     

Carbon dioxide absorption in a cross-flow rotating packed bed

This work investigates the feasibility of applying the cross-flow rotating packed bed (RPB) to the removal of carbon dioxide (CO₂) by absorption from gaseous streams. Monoethanolamine (MEA) aqueous solution was used as the model absorbent. Also, other absorbents such as the NaOH and 2-amino-2-methyl-1-propanol (AMP) aqueous solutions were compared with the MEA aqueous solution. The CO₂ removal efficiency was observed as functions of rotor speed, gas flow rate, liquid flow rate, MEA concentration, and CO₂ concentration. Experimental results indicated that the rotor speed positively affects the CO₂ removal efficiency. Our results further demonstrated that the CO₂ removal efficiency increased with the liquid flow rate and the MEA concentration; however, decreased with the gas flow rate and the CO₂ concentration. Additionally, the CO₂ removal efficiency for the MEA aqueous solution was superior to that for the NaOH and AMP aqueous solutions. Based on the performance comparison with the conventional packed bed and the countercurrent-flow RPB, the cross-flow RPB is an effective absorber for CO₂ absorption process.     

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。     

翅片导流板填料应用于旋转填料床的特性

For an alcohol/water system and with fin baffle packing, continuous distillation experiments were carried out in a rotating packed bed (RPB) system at atmospheric pressure. The effects of the average high gravity factor (β), liquid reflux ratio (R) and feedstock flux (F) on the momentum transfer and mass transfer were investigated. The gas phase pressure drop of RPB increased with the average high gravity factor, liquid reflux ratio and feedstock flux, which was 13.55-64.37 Pa at β of 2.01-51.49, R of 1.0-2.5, and F of 8-24 L&;#8226;h－1 for a theoretical tray in the RPB with fin baffle packing. The investigation on the mass transfer in the RPB with different packings showed that the number of transfer units of RPB with a packing also increased with the average high gravity factor, reflux ratio and feedstock flux. It is found that the fin baffle packing (packing III) presents the best mass transfer performance and lowest pressure drop for the height equivalent to a theoretical plate (HETP), which is 6.59-9.84 mm.     

Evaluation of a rotating packed bed equipped with blade packings for methanol and 1-butanol removal

Absorption removal of methanol and 1-butanol from gaseous streams with water was investigated in the RPB equipped with blade packings. The removal efficiency (E) of methanol and 1-butanol was found to increase with the RPB speed and the liquid flow rate but decrease with the gas flow rate. Also, the overall volumetric gas-side mass transfer coefficient (K_Ga) for methanol and 1-butanol absorption was observed to increase with the RPB speed, the gas flow rate, and the liquid flow rate. According to the obtained dependence of K_Ga on the gas and liquid flow rates, the mass transfer in methanol and 1-butanol absorption was observed to be controlled primarily by the gas-side mass transfer. Furthermore, the height of a transfer unit (HTU) for methanol and 1-butanol absorption decreased with the RPB speed and the liquid flow rate but increased with the gas flow rate. The obtained results demonstrated that mass transfer efficiency of the RPB equipped with blade packing was comparable to that of a hollow fiber absorber. Consequently, the RPB equipped with blade packings has a great potential in the removal of alkanols from the exhausted gases.     

旋转填料床间歇萃取精馏性能研究

为了寻找强化间歇萃取精馏过程的有效途径,在装填2mm×2mm三角形螺旋填料的旋转床中,以乙醇-水为实验物系,乙二醇为萃取剂,通过考察馏出液组成随时间的变化情况,产品的纯度和回收率随转速、回流比和溶剂比的变化情况,研究了旋转填料床间歇萃取精馏的性能。结果表明,旋转填料床中强大的离心力和高效填料的协同作用极大地强化了间歇萃取精馏过程,具有分离效果好、操作时间短、节能、小设备大生产能力等突出优点;存在最佳转速使产品的纯度和回收率最大;增加溶剂比和回流比均能使产品的纯度和回收率得到提高,但增加溶剂比的效果更显著。旋转填料床是强化间歇萃取精馏过程的有效途径。     

Simulation of heat transfer and hydrodynamics for metal structured packed bed

Modeling and simulation based on computational hydrodynamics and heat transfer for metal structured packed bed are carried out to predict the flow field and temperature field, and to evaluate its performance in transport aspect. The comparison between the simulation results for the metal structured packed bed and the experimental heat transfer performance as well as pressure drop of the conventional pellet packed bed is made, which quantitatively validates that transport performance of the metal structured packed bed is much better. Furthermore, the effects of geometric parameters and the property of solid phase on heat transfer of the metal structured packed bed are discussed. It is found that at low Re, the specific surface area is a key factor to determine the heat transfer capability of the structured bed. However, when Re turns to be high, the property of solid phase and voidage of the structured packed bed will play an important role in the evaluation of its heat transfer. In light of above results, some feasible methods are available to enhance the heat transfer performance.     

Micromixing efficiency of rotating packed bed with premixed liquid distributor

Rotating packed bed (RPB), in which high gravity is simulated by a centrifugal force, plays an important role in process intensification of fluid mixing and mass transfer. However, uneven initial liquid distribution in RPB leads to poor micromixing efficiency in local areas of the packing. Therefore, a premixed liquid distributor is proposed in this work to improve the liquid distribution in RPB. Micromixing efficiency of RPB with the premixed liquid distributor was studied by adopting the iodide–iodate reaction as working system and show better micromixing efficiency compared to that of RPB with non-premixed liquid distributor. Also, the effects of operating conditions (e.g. rotational speed, acid concentration, volumetric flow rate) and geometries using the premixed liquid distributor on micromixing efficiency (characterized by segregation index X_S) were investigated. The results show that segregation index X_S decreases with the increase of rotational speed, and the decrease of acid concentration and volumetric flow rate.     

旋转填料床精馏过程流体力学性能研究

在对旋转填料床精馏特性研究的基础上,以塑料多孔板为填料,乙醇-水为体系,在全回流操作条件下,进一步研究了气相动能因子F、超重力因子β和回流量L对旋转填料床流体力学特性的影响,证明了旋转填料床的低耗能特性。     

Computational fluid dynamic simulation of gas-liquid flow in rotating packed bed:A review

The rotating packed bed (RPB) has been widely used in gas-liquid flow systems as a process intensifica-tion device,exhibiting excellent mass transfer enhancement characteristics.However,the complex inter-nal structure and the high-speed rotation of the rotor in RPB bring significant challenges to study the intensification mechanism by experiment methods.In the past two decades,Computational fluid dynam-ics (CFD) has been gradually applied to simulate the hydrodynamics and mass transfer characteristics in RPB and instruct the reactor design.This article covers the development of the CFD simulation of gas-liquid flow in RPB.Firstly,the improvement of the simulation method in the aspect of mathematical mod-els,geometric models,and solving methods is introduced.Secondly,new progress of CFD simulation about hydrodynamic and mass transfer characteristics in RPB is reviewed,including pressure drop,veloc-ity distribution,flow pattern,and concentration distribution,etc.Some new phenomena such as the end effect area with the maximum turbulent have been revealed by this works.In addition,the exploration of developing new reactor structures by CFD simulation is introduced and it is proved that such new struc-tures are competitive to different applications.The defects of current research and future development directions are also discussed at last.     

泡沫陶瓷填料旋转填充床微观混合性能

采用碘化物-碘酸盐平行竞争反应为工作体系,以离集指数（X_S）表征微观混合性能,实验考察了物料体积流量、H⁺浓度、旋转填充床转速、物料体积流量比等对两种不同孔径的新型整体泡沫陶瓷填料旋转填充床的微观混合性能的影响。结果表明,孔径较小的泡沫陶瓷填料更利于微观混合;H⁺浓度、进料体积流量比的增加会导致X_S增加;而旋转填充床转速、进料流量的增大都可使X_S下降。在实验研究的基础上,利用团聚模型计算泡沫陶瓷填料旋转填充床微观混合时间（t_m）,得到t_m范围为0.385～8.55 ms。与传统不锈钢丝网填料对比,泡沫陶瓷填料t_m最小值（0.385 ms）低于不锈钢丝网填料的t_m最小值（1.6 ms）,表明泡沫陶瓷填料的微观混合性能优于传统不锈钢丝网填料。     

旋转填料床最新研究进展

旋转填料床是20世纪80年代发展起来的一种新兴气液传质设备,经过20多年的发展,旋转填料床在设备构型、气液进料上不断得到改进。就旋转填料床的研究进展进行了详细阐述,并介绍了几种常见的旋转填料床。     

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。     

Numerical simulation and experimental study of the characteristics of packing feature size on liquid flow in a rotating packed bed

Rotating packed bed has high efficiency of gas–liquid mass transfer. So it is significant to investigate fluid motion in rotating packed bed. Numerical simulations of the effects of packing feature size on liquid flow characteristics in a rotating packed bed are reported in this paper. The particle image velocimetry is compared with the numerical simulations to validate the turbulent model. Results show that the liquid exists in the packing zone in the form of droplet and liquid line, and the cavity is droplet. When the radial thickness of the packing is less than 0.101 m, liquid line and droplets appear in the cavity. When rotational speed and radial thickness of the packing increase, the average diameter of the droplets becomes smaller, and the droplet size distribution becomes uniform. As the initial velocity of the liquid increases, the average droplet diameter increases and the uniformity of particle size distribution become worse. The droplet velocity increases with the radial thickness of the packing increasing, and gradually decreases when it reaches the cavity region. The effect of packing thickness is most substantial through linear fitting. The predicted and simulated values are within ±15%. The cumulative volume distribution curves of the experimental and simulated droplets are consistent with the R-R distribution.     

A two-stage blade-packing rotating packed bed for intensification of continuous distillation

A two-stage blade-packing rotating packed bed(TSBP-RPB) was designed and developed for the intensification of continuous distillation. The mass transfer parameters of the TSBP-RPB were investigated using a chemisorption system. Continuous distillation experiments were conducted in the TSBP-RPB by the methanol–water binary system. Experimental results showed that values of the effective interfacial area and liquid-side mass transfer coefficient of the TSBP-RPB were 93–337 m~2·m~(-3) and 0.05–0.19 cm·s~(-1), respectively. The height of equivalent theoretical plate(HETP) of the TSBP-RPB ranged from 1.9 to 10 cm. Moreover, the TSBP-RPB is easy to be manufactured, which shows great potential for the application of continuous distillation.     

Preparation of nanostructured goethite by chemical precipitation in a rotating packed bed

Nanostructured goethite was successfully prepared at 25°C by chemical precipitation in the rotating packed bed in which the rotational speed was 1800 rpm, the flow rate of aqueous FeCl₃ with a concentration of 0.3 mol/L was 0.5 L/min, and the flow rate of aqueous NaOH with a concentration of 0.9 mol/L was 0.5 L/min. The prepared nanostructured goethite had an average crystallite size of 20 nm and a needle shape with a mean length of 500 nm. Moreover, the prepared nanostructured goethite exhibited the Type-III isotherm for N₂ adsorption-desorption with a BET specific surface area of 23 m²/g. The rotating packed bed with the chemical precipitation approach yielded a rate of preparation of nanostructured goethite of about 19 kg/day. The adsorption capacity of the prepared nanostructured goethite was examined using the adsorption of dyes in water. Based on the Langmuir model, its maximum adsorption capacity for Reactive Red 2 was 29.1 mg/g, and its maximum adsorption capacity for Orange G was 24.5 mg/g. Accordingly, the prepared nanostructured goethite can be used as a potential adsorbent for removing dyes from water.     

不同填料旋转填料床废水气提效果研究

为了探索旋转填料床中不同填料对废水中丙烯腈去除率的影响,并为超重力气提丙烯腈废水工艺优选合适的填料提供参考,分别在装有填料A和填料B的旋转填料床中进行气提丙烯腈废水的实验。在相同的工艺条件下对比考察了填料A和B对丙烯腈去除率的影响。结果表明:在实验操作条件范围内,填料A和B的丙烯腈去除率均可达60%以上;更换高效的填料有助于丙烯腈去除率的提高,且气液比对丙烯腈去除率的增幅影响最为显著,超重力因子β次之;与填料A相比,仅考虑丙烯腈废水处理效果和处理成本,填料B更适用于超重力气提工艺中的旋转填料床。研究结果为选取适宜的旋转填料床填料以及超重力气提工艺的工业化应用提供一定依据。