Measurements of the effective mass transfer areas for the gas–liquid rotating packed bed

Rotating packed bed(RPB) is one of the most effective gas–liquid mass transfer enhancement reactors, its effective specific mass transfer area(ae) is critical to understand the mass transfer process. By using the NaOH–CO_(2) chemical absorption method, the aevalues of three RPB reactors with different rotor sizes were measured under different operation conditions. The results showed that the high gravity factor and liquid flow rate were major affecting factors, while the gas flow rate exhibited minor influence.The radius of packing is the dominant equipment factor to affect aevalue. The results indicated that the contact area depends on the dispersion of the liquid phase, thus the centrifugal force of rotating packed bed greatly influenced the aevalue. Moreover, the measured ae/ap(effective specific mass transfer area/specific surface area of packing) values were fitted with dimensionless correlation formulas. The unified correlation formula with dimensionless bed size parameter can well predict the experimental data and the prediction errors were within 15%.

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 intensification device,exhibiting excellent mass transfer enhancement characteristics.However,the complex internal 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 dynamics(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 gasliquid flow in RPB.Firstly,the improvement of the simulation method in the aspect of mathematical models,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,velocity 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 structures are competitive to different applications.The defects of current research and future development directions are also discussed at last.

Catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-Mn-Cu/γ-Al2O_(3) in a rotating packed bed

This study investigated catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-MnCu/γ-Al_(2)O_(3)(Cat)in a rotating packed bed(RPB)for the first time.The results showed that the value of the overall decomposition rate constant of ozone(K_(c))and overall volumetric mass transfer coefficient(K_(L)a)are 4.28×10^(-3) s^(-1) and 11.60×10^(-3) s^(-1) respectively at an initial pH of 6,βof 40,Co3(g)of 60 mg·L^(-1)and Q_(L) of 85 L·h^(-1) in deionized water,respectively.Meanwhile,the K_(c) and K_(L)a values of Fenhe water are0.88×10^(-3) s^(-1) and 2.51×10^(-3) s^(-1) lower than deionized water,respectively.In addition,the K_(c) and K_(L)a values in deionized water for the Cat/O_(3)-RPB system are 44.86%and 47.41%higher than that for the Cat/O_(3)-BR(bubbling reactor)system,respectively,indicating that the high gravity technology can facilitate the decomposition and mass transfer of ozone in heterogeneous catalytic ozonation and provide some insights into the industrial wastewater.

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.

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(kLS) have been investigated. The correlation for predicting kLSwas proposed, and the deviation between the experimental and predicted values was within±12%. The liquid–solid volumetric mass transfer coefficient(kLSaLS) 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.

Research and development of advanced structured packing in a rotating packed bed

As the core component of the rotating packing bed,packing is a place for efficient gas–liquid mixing and mass transfer.In this paper,a 3D structured packing composed of a mesh structure and a support structure was designed.The mesh structure is a ring-shaped mesh surrounded by triangular meshes,which is stable in structure and can achieve a high degree of dispersion and aggregation of the liquid phase.The support structure is composed of ring-shaped structural units arranged at a certain angle along the axial direction,which can enhance the turbulence of the airflow while constructing regular gas-phase channels.Circumferential steel meshes of different diameters and supporting structures are alternately combined to form 3D packing,which is loaded in a layered cross-flow rotating packing bed.The results show that under the same operating conditions,the mass transfer performance of 3D packing and wire mesh packing are equivalent,and both are better than pall ring packing.Moreover,the pressure drop of 3D packing is significantly lower than that of pall ring packing and wire mesh packing.The design and implementation of packing the development presented in this paper can be used to develop special structured packing for rotating bed,which can further improve the performance of rotating packed bed(RPB).

Preparation and characterization of NaY zeolite in a rotating packed bed

NaY Zeolite was synthesized in a rotating packed bed （RPB） for the first time. A Si-A1 gel with a specific composition was used as the structure-directing agent. The as-synthesized NaY Zeolite was characterized with scanning electron microscopy （SEM）, X-ray diffraction （XRD） and specific surface area （BET）. The characterization result showed that the NaY Zeolite had a particle size of approximately 200 rim, n（SiO2）/n（Al203） ratio of 5.03, crystallinity of 96% and specific surface area of 714 m2/g. The experimental results indicated that the structure of NaY Zeolite was related to the synthesis conditions （such as reactors, crystallization time and so on）. The micromixing efficiency was proven to be the most important factor for synthesis of NaY Zeolite in the high-gravity environment in RPB.

Preparation of Pd/c-Al_(2)O_(3)/nickel foam monolithic catalyst and its performance for selective hydrogenation in a rotating packed bed reactor

Selective hydrogenation plays an important role in chemical industries,yet its selectivity is usually limited by the mass transfer.In this work,the enhanced hydrogenation selectivity was achieved in a rotating packed bed(RPB)reactor with excellent mass transfer efficiency.Aiming to be used under the centrifugal filed,a monolithic catalyst Pd/c-Al_(2)O_(3)/nickel foam suiting for the shape and size of the rotor of RPB reactor was prepared by the electrophoretic deposition method.The mechanical strength of the catalyst can meet the requirement of high centrifugal force in the RPB.The hydrogenation selectivity in the RPB reactor using the 3-methyl-1-pentyn-3-ol hydrogenation system was 3–8 times higher than that in a stirred tank reactor under similar conditions.This work proves the feasibility of intensifying the selectivity of hydrogenation process in the RPB reactor.

Comparison of Mass Transfer Characteristics between Countercurrent-Flow and Crosscurrent-Flow Rotating Packed Bed

The rotating packed bed(RPB), mainly including the countercurrent-flow RPB(Counter-RPB) and the crosscurrentflow RPB(Cross-RPB) that are classified from the perspective of gas-liquid contact style, is a novel process intensification device. A significant measurement standard for evaluating the performance of RPB is the mass transfer effect. In order to compare the mass transfer characteristics of Counter-RPB and Cross-RPB with the same size, the liquid volumetric mass transfer coefficient(k_La_e) and effective interfacial area(a_e) were measured under identical operating conditions. Meanwhile, the comparison of comprehensive mass transfer performance was conducted using the ratio of ΔP(pressure drop) to kLae as the standard. Experimental results indicated that kLae and ae increased with the increase in liquid spray density q, gas velocity u, and high gravity factor β. Furthermore, compared with the Cross-RPB, the Counter-RPB has higher liquid volumetric mass transfer coefficient and slightly larger effective interfacial area. The experimental results of comprehensive mass transfer performance showed that the Counter-RPB had higher ΔP/k_La_e than the Cross-RPB with changes in liquid spray density and high gravity factor, and there exists a turning point at 0.71 m/s accompanied by a variation with gas velocity. Moreover, the relative error of experimental value to calculated value, which was computed by the correlative expressions of kLae, was less than 5 %. In conclusion, the mass transfer characteristics of RPB are deeply impacted by the manner in which the flows are established and the Cross-RPB would have a great potential for industrial scale-up applications.

Controllable and high-throughput preparation of microdroplet using an ultra-high speed rotating packed bed

Microdroplets and their dispersion,with a large specific surface area and a short diffusion distance,have been applied in various unit operations and reaction processes.However,it is still a challenge to control the size and size distribution of microdroplets,especially for high-throughput generation.In this work,a novel ultra-high speed rotating packed bed(UHS-RPB)was invented,in which rotating foam packing with a speed of 4000-12000 r·min^(-1) provides microfluidic channels to disperse liquid into microdroplets with high throughput.Then generated microdroplets can be directly dispersed into a continuous falling film for obtaining a mixture of microdroplet dispersion.In this UHS-RPB,the effects of rotational speed,liquid initial velocity,liquid viscosity,liquid surface tension and packing pore size on the average size(d_(32))and size distribution of microdroplets were systematically investigated.Results showed that the UHS-RPB could produce microdroplets with a d_(32) of 25-63μm at a liquid flow rate of 1025 L·h^(-1),and the size distribution of the microdroplets accords well with Rosin-Rammler distribution model.In addi-tion,a correlation was established for the prediction of d_(32),and the predicted d_(32) was in good agreement with the experimental data with a deviation within±15%.These results demonstrated that UHS-RPB could be a promising candidate for controllable preparation of uniform microdroplets.

Synthesis of Silver Sulf ide Quantum Dots Via the Liquid–Liquid Interface Reaction in a Rotating Packed Bed Reactor

We developed the high-gravity coupled liquid-liquid interface reaction technique on the basis of the rotating packed bed(RPB)reactor for the continuous and ultrafast synthesis of silver sulfide(Ag2S)quantum dots(QDs)with near-infrared(NIR)luminescence.The formation of Ag2S QDs occurs at the interface of microdroplets,and the average size of Ag2S QDs was 4.5 nm with a narrow size distribution.Ag2S QDs can disperse well in various organic solvents and exhibit NIR luminescence with a peak wavelength at 1270 nm under 980-nm laser excitation.The mechanism of the process intensification was revealed by both the computational fluid dynamics simulation and fluorescence imaging,and the mechanism is attributed to the small and uniform droplet formation in the RPB reactor.This study provides a novel approach for the continuous and ultrafast synthesis of NIR Ag2S QDs for potential scale-up.

Removal of nitric oxide from simulated flue gas using aqueous persulfate with activation of ferrous ethylenediaminetetraacetate in the rotating packed bed

Nitric oxide being a major gas pollutant has attracted much attention and various technologies have been developed to reduce NO emission to preserve the environment.Advanced persulfate oxidation technology is a workable and effective choice for wet flue gas denitrification due to its high efficiency and green advantages.However,NO absorption rate is limited and affected by mass transfer limitation of NO and aqueous persulfate in traditional reactors.In this study,a rotating packed bed(RPB)was employed as a gas-liquid absorption device to elevate the NO removal efficiency(η_(NO))by aqueous persulfate((NH_(4))_(2)S_(2)O_(8))activated by ferrous ethylenediaminetetraacetate(Fe^(^(2+))-EDTA).The experimental results regarding the NO absorption were obtained by investigating the effect of various operating parameters on the removal efficiency of NO in RPB.Increasing the concentration of(NH_(4))_(2)S_(2)O_(8) and liquid-gas ratio could promoted the oxidation and absorption of NO while theη_(NO) decreased with the increase of the gas flow and NO concentration.In addition,improving the high gravity factor increased theη_(NO) and the total volumetric mass transfer coefficient(K_(G)α )which raise theη_(NO) up to more than 75%under the investigated system.These observations proved that the RPB can enhance the gas-liquid mass transfer process in NO absorption.The correlation formula between K_(G)α and the influencing factors was determined by regression calculation,which is used to guide the industrial scale-up application of the system in NO removal.The presence of O_(2) also had a negative effect on the NO removal process and through electron spin resonance spectrometer detection and product analysis,it was revealed that Fe^(2+)-EDTA activated(NH_(4))2S_(2)O_(8) to produce•SO_(4)^(-),•OH and•O_(2)^(-),played a leading role in the oxidation of NO,to produce NO_(3)^(-)as the final product.The obtained results demonstrated a good applicable potential of RPB/PS/Fe^(2+)-EDTA in the removal of NO from flue gases.

Removal of hydrophobic volatile organic compounds with sodium hypochlorite and surfactant in a co-current rotating packed bed

A co-current flow rotating packed bed was applied to remove volatile organic compounds（VOCs） by sodium hypochlorite（Na Cl O） and surfactant（sodium dodecyl benzene sulfonate,SDBS） from air stream. Xylene was used as a model VOC herein. The effect of p H,concentration of Na Cl O and SDBS solution, liquid flow rate, gas flow rate and rotational speed on xylene removal efficiency and overall mass transfer coefficient（KGa） were discussed. Then, a correlation for KGa of the co-current rotating packed bed was proposed by fitting the experimental data of KGa and independent variables of liquid/gas ratio,rotational speed, p H, Na Cl O concentration and treatment time, which was in good agreement with the experimental data（the deviation ≤ ± 30%）.

Experimental investigation of nanoparticles precipitation in a rotating packed bed

Precipitation of BaSO4 nanoparticles was studied for the first time in a specially designed rotating packed bed （RPB）, which allowed sampling at different radial positions to provide better insight of the mechanism of precipitation in RPB. Particle size and morphology were characterized by TEM, while the quality of synthesized BaSO4 powders was analyzed by XRD and BET, and compared with those prepared in a stirred-tank reactor. The important role of the inlet region of the RPB in the whole precipitation process was experimentally confirmed, as a significant essence for the design of industrial RPB for the precipitation of sparingly soluble materials. The effects of different operating conditions on particle size were also investigated, showing that particle size decreases with increasing rotational speed and liquid flow rate, due to the enhancement of micromixing in the RPB.

A method for establishing a bearing residual life prediction model for process enhancement equipment based on rotor imbalance response analysis

A rotating packed bed is a typical chemical process enhancement equipment that can strengthen micromixing and mass transfer.During the operation of the rotating packed bed,the nonreactants and products irregularly adhere to the wire mesh packing in the rotor,thus resulting in an imbalance in the vibration of the rotor,which may cause serious damage to the bearing and material leakage.This study proposes a model prediction for estimating the bearing residual life of a rotating packed bed based on rotor imbalance response analysis.This method is used to determine the influence of the mass on the imbalance in the vibration of the rotor on bearing damage.The major influence on rotor vibration was found to be exerted by the imbalanced mass and its distribution radius,as revealed by the results of orthogonal experiments.Through implementing finite element analysis,the imbalance response curve for the rotating packed bed rotor was obtained,and a correlation among rotor imbalance mass,distribution radius of imbalance mass,and bearing residue life was established via data fitting.The predicted value of the bearing life can be used as the reference basis for an early safety warning of a rotating packed bed to effectively avoid accidents.

Sulfonation of 1,4-diaminoanthraquinone leuco by chlorosulfonic acid:Kinetics and process intensification

The work herein employed a rotating packed bed(RPB)to intensify the sulfonation process of 1,4-diaminoanthraquinone leuco(DL)in an attempt to improve the yield of the product 1,4-diaminoanthra quinone-2-sulfonic acid(DSA).First,the effects of operating conditions in a stirred tank reactor(STR),including stirring speed,chlorosulfonic acid/DL molar ratio(η),solvent/DL mass ratio(ζ),reaction temperature and dropping speed of chlorosulfonic acid,on the yield of DSA were investigated.The yield of DSA can reach 87.34%under the optimal operating conditions:stirring speed of 500 r·min^(-1),ηof 4.5,ζof 7,reaction temperature of 150℃,dropping speed of 0.61 ml·min^(-1).In addition,the kinetics of the sulfonation process via the shrinking core model revealed that the reaction is controlled by diffusion via a product layer under the reaction temperature of 140℃.Furthermore,the RPB was employed to intensify the mass transfer between liquid and solid phases during the sulfonation reaction process.The results showed that the DSA yield of 92.69%obtained by RPB was 5.35%higher than that by STR,indicating that RPB can significantly intensify the mass transfer in the liquid-solid phase sulfonation reaction process.

Preparation by High-gravity Technology of a Cu/N-TiO_(2) Nanophotocatalyst for Photodegradation of Phenol Wastewater

TiO_(2) is a promising photocatalyst,but its practical use is restricted by its low catalytic efficiency caused by the large particle size and uneven size distribution,which arise from the limited contact area of the liquid-liquid interface during synthesis.Impinging stream-rotating packed bed(IS-RPB)reactors,which are used for process intensification,overcome the mixing limitation of traditional stirred-tank reactors and provide a micromixing environment at the molecular scale for the two liquid phases,which can reduce the particle size and distribution range.Cu/N-TiO_(2) nanoparticles were prepared in an IS-RPB reactor by the one-step precipitation method using urea as the nitrogen source,titanyl sulfate as the titanium source,copper chloride as the copper source,and ammonium hydroxide as the precipitant.The particle size of the photocatalyst was about 11.40 nm with a narrow size distribution measured by scanning electron microscopy and transmission electron microscopy.X-ray photoelectron spectroscopy showed that N replaced some O and was uniformly dispersed in the TiO_(2) lattice as interstitial and substitutional N.Cu replaced some Ti and was present as Cu^(2+).The synergistic effects of these two elements formed a new impurity energy level and reduced the band gap energy of the TiO_(2) nanoparticles.The specific surface area of the Cu/N-TiO_(2) nanoparticles was 152.97 m^(2)/g.The effects of the main factors on the degradation rate were studied,and the removal efficiency reached 100%under the optimal operating conditions after 2 h ultraviolet irradiation.The electron paramagnetic resonance measurements showed that the superoxide radical played a main role in the degradation process,whereas the photogenerated holes and hydroxyl radicals had weak effects.

Synthesis and Catalytic Activity of Copper(Ⅱ) Resorcylic Acid Nanoparticles

Copper（ Ⅱ ） resercyiic acid（CuRes） nanoparticles were synthesized by using reactive precipitation method with resorcylic acid and blue copperas as the raw material in a rotating packed bed. The sample obtained was characterized by using X-ray diffraction（XRD）, transmission electron micrescopy（TEM）, Fourier transform infrared spectroscopy （FTIR）, thermo-gravimetric analyses （TG）, and element analysis. In addition, the catalytic activity of CuRes nanoparticles on the thermal decomposition of nitrocellulose-nitroglycerine（NC-NG） was also determined via DSC. The results show that the spherical nanoparticles with a diameter of 20 nm were obtained in ethanol solution. The peak temperature of the thermal decomposition of NC-NG-CuRes decreases by 3℃ compared with that of normal CuRes, and the decomposition enthalpy is increased by 735 J/g, and therefore, it is reasonable to assume that CuRes nanoparticles have a better catalytic activity.

A Novel Route to Prepare Nanocomposites in Larger Scale

A novel route to prepare nanocomposites was illustrated through preparing overbased calcium petroleum sulfonate lubricating oil detergent, where the rotating packed bed （RPB） was used as reactor in place of conventional reaction vessel. The results showed that the carbonation efficiency is improved, the raw materials consumption is reduced, and the dispersibilities, sizes and morphologies of nano-sized CaCO3 particles in overbased detergent are enhanced. It is deduced reasonably that this route can be extensively applied to nanocomposites preparation in appropriate conditions and would be a platform technology in this field.

MASS PRODUCTION OF NANOPARTICLES BY HIGH GRAVITY REACTIVE PRECIPITATION TECHNOLOGY WITH LOW COST

Mass production of nanoparticles at low cost has attracted much attention from industrial and academic circles. In this paper, a novel method, the high gravity reactive precipitation (HGRP) technology, of manufacturing CaCO3 nanoparticles, presently scaled-up to an annual capacity of 10,000 tons, is presented. This paper describes the process principle, the process design and experiments on the syntheses of 15-30 nm CaCO3, 30-50 nm SiO2, 20-30 nm TiO2, 20-60 nm ZnO, 20-30 nm ZnS, 30 nm SrCO3, 40-70 nm BaTiO3, stick-like nano BaCO3 as well as nano-fibrillar aluminum hydroxide measuring 1-10 nm in diameter and 50-300 nm in length, using liquid-liquid, gas-liquid and gas-liquid-solid reactant systems. The advantage of using the HGRP technology is illustrated by comparison to conventional methods.