PVDF-assisted pyrolysis strategy for corrugated plate oxygen electrocatalysis nanoreactor:Simultaneously realizing efficient active sites and rapid mass transfer

Though Zn-air batteries(ZABs)are one of the most promising system for energy storage and conversion,challenge still persists in its commercial application due to the sluggish kinetics of oxygen reduction/evolution reaction(ORR/OER).Hereby,a polyvinylidene fluoride(PVDF)-assisted pyrolysis strategy is proposed to develop a novel corrugated plate-like bifunctional electrocatalyst using two-dimensional zeolitic imidazolate frameworks(2D ZIF-67)as the precursor.The employed PVDF plays an important role in inheriting the original 2D structure of ZIF-67 and modulating the composition of the final products.As a result,a corrugated plate-like electrocatalyst,high-density Co nanoparticles decorated 2D Co,N,and F tri-doped carbon nanosheets,can be obtained.The acquired electrocatalyst enables efficient active sites and rapid mass transfer simultaneously,thus showing appreciable electrocatalytic performance for rechargeable Zn-air batteries.Undoubtedly,our proposed strategy offers a new perspective to the design of advanced oxygen electrocatalysts.

Research on shell-side heat and mass transfer with multi-component in LNG spiral-wound heat exchanger under sloshing conditions

The spiral-wound heat exchanger(SWHE) is the primary low-temperature heat exchanger for large-scale LNG plants due to its high-pressure resistance, compact structure, and high heat exchange efficiency. This paper studied the shell-side heat and mass transfer characteristics of vapor-liquid two-phase mixed refrigerants in an SWHE by combining a multi-component model in FLUENT software with a customized multicomponent mass transfer model. Besides, the mathematical model under the sloshing condition was obtained through mathematical derivation, and the corresponding UDF code was loaded into FLUENT as the momentum source term. The results under the sloshing conditions were compared with the relevant parameters under the steady-state condition. The shell-side heat and mass transfer characteristics of the SWHE were investigated by adjusting the component ratio and other working conditions. It was found that the sloshing conditions enhance the heat transfer performance and sometimes have insignificant effects. The sloshing condition is beneficial to reduce the flow resistance. The comprehensive performance of multi-component refrigerants has been improved and the improvement is more significant under sloshing conditions, considering both the heat transfer and pressure drop.These results will provide theoretical support for the research and design of multi-component heat and mass transfer enhancement of LNG SWHE under ocean sloshing conditions.

Structural engineering of Fe single-atom oxygen reduction catalyst with high site density and improved mass transfer

Fe-N-C catalysts are widely considered as promising non-precious-metal candidates for electrocatalytic oxygen reduction reaction(ORR),Yet despite their high catalytic activity through rational modulation,challenges remain in their low site density and unsatisfactory mass transfer structure.Herein,we present a structural engineering approach employing a soft-template coating strategy to fabricate a hollow and hierarchically porous N-doped carbon framework anchored with atomically dispersed Fe sites(FeNCh) as an efficient ORR catalyst.The combination of hierarchical porosity and high exterior surface area is proven crucial for exposing more active sites,which gives rise to a remarkable ORR performance with a half-wave potential of 0.902 V in 0.1 m KOH and 0.814 V in 0.1 m HClO_(4),significantly outperforming its counterpart with solid structure and dominance of micropores(FeNC-s).The mass transfer property is revealed by in-situ electrochemical impedance spectroscopy(EIS) measurement.The distribution of relaxation time(DRT) analysis is further introduced to deconvolve the kinetic and mass transport processes,which demonstrates an alleviated mass transport resistance for FeNC-h,validating the effectiveness of structural engineering.This work not only provides an effective structural engineering approach but also contributes to the comprehensive mass transfer evaluation on advanced electrocatalyst for energy conversion applications.

Mass transfer enhancement and hydrodynamic performance with wire mesh coupling solid particles in bubble column reactor

It is of vital significance to investigate mass transfer enhancements for chemical engineering processes.This work focuses on investigating the coupling influence of embedding wire mesh and adding solid particles on bubble motion and gas-liquid mass transfer process in a bubble column.Particle image velocimetry(PIV)technology was employed to analyze the flow field and bubble motion behavior,and dynamic oxygen absorption technology was used to measure the gas-liquid volumetric mass transfer coefficient(kLa).The effect of embedding wire mesh,adding solid particles,and wire mesh coupling solid particles on the flow characteristic and kLa were analyzed and compared.The results show that the gas-liquid interface area increases by 33%-72%when using the wire mesh coupling solid particles strategy compared to the gas-liquid two-phase flow,which is superior to the other two strengthening methods.Compared with the system without reinforcement,kLa in the bubble column increased by 0.5-1.8 times with wire mesh coupling solid particles method,which is higher than the sum of kLa increases with inserting wire mesh and adding particles,and the coupling reinforcement mechanism for affecting gas-liquid mass transfer process was discussed to provide a new idea for enhancing gas-liquid mass transfer.

Effect of surfactant frequently used in soil flushing on oxygen mass transfer in micro-nano-bubble aeration system

In-site soil flushing and aeration are the typical synergetic remediation technology for contaminated sites.The surfactant present in flushing solutions is bound to affect the aeration efficiency.The purpose of this study is to evaluate the effect of surfactant frequently used in soil flushing on the oxygen mass transfer in micro-nano-bubble(MNB)aeration system.Firstly,bio-surfactants and chemical surfactants were used to investigate their effects on Sauter mean diameter of bubble(dBS),gas holdup(ε),volumetric mass-transfer coefficient(kLa)and liquid-side mass-transfer coefficient(kL)in the MNB aeration system.Then,based upon the experimental results,the Sardeing's and Frossling's models were modified to describe the effect of surfactant on kL in the MNB aeration.The results showed that,for the twenty aqueous surfactant solutions,with the increase in surfactant concentration,the value of dBS,kLa and kL decreased,while the value ofεand gas-liquid interfacial area(a)increased.These phenomena were mainly attributed to the synergistic effects of immobile bubble surface and the suppression of coalescence in the surfactant solutions.In addition,with the presence of electric charge,MNBs in anionic surfactant solutions were smaller and higher in number than in non-ionic surfactant solutions.Furthermore,the accumulation of surfactant on the gas-liquid interface was more conspicuous for small MNB,so the reduction of kL in anionic surfactant solutions was larger than that in non-ionic surfactant solutions.Besides,the modified Frossling's model predicted the effect of surfactant on kL in MNB aeration system with reasonable accuracy.

Mass Transfer-Promoted Fe^(2+)/Fe^(3+)Circulation Steered by 3D Flow-Through Co-Catalyst System Toward Sustainable Advanced Oxidation Processes

Realizing fast and continuous generation of reactive oxygen species(ROSs)via iron-based advanced oxidation processes(AOPs)is significant in the environmental and biological fields.However,current AOPs assisted by co-catalysts still suffer from the poor mass/electron transfer and non-durable promotion effect,giving rise to the sluggish Fe^(2+)/Fe^(3+)cycle and low dynamic concentration of Fe^(2+)for ROS production.Herein,we present a three-dimensional(3D)macroscale co-catalyst functionalized with molybdenum disulfide(MoS_(2))to achieve ultra-efficient Fe^(2+)regeneration(equilibrium Fe^(2+)ratio of 82.4%)and remarkable stability(more than 20 cycles)via a circulating flow-through process.Unlike the conventional batch-type reactor,experiments and computational fluid dynamics simulations demonstrate that the optimal utilization of the 3D active area under the flow-through mode,initiated by the convectionenhanced mass/charge transfer for Fe^(2+)reduction and then strengthened by MoS_(2)-induced flow rotation for sufficient reactant mixing,is crucial for oxidant activation and subsequent ROS generation.Strikingly,the flow-through co-catalytic system with superwetting capabilities can even tackle the intricate oily wastewater stabilized by different surfactants without the loss of pollutant degradation efficiency.Our findings highlight an innovative co-catalyst system design to expand the applicability of AOPs based technology,especially in large-scale complex wastewater treatment.

Discharge and mass transfer characteristics of atmospheric pressure gas-solid two-phase gliding arc

In this work,a gas-solid two-phase gliding arc discharge(GS-GAD)reactor was built.Gliding arc was formed in the gap between the blade electrodes,and solid powder was deposited on the sieve plate positioned beneath the blade electrodes.A range of experimental parameters,including the inter-electrode spacing,gas flow rate,applied voltage,and the type of the powder,were systematically varied to elucidate the influence of solid powder matter on the dynamics of gliding arc discharge(GAD).The discharge images were captured by ICCD and digital camera to investigate the mass transfer characteristics of GS-GAD,and the electrical parameters,such as the effective values of voltage,current,and discharge power were record to reveal the discharge characteristics of GS-GAD.The results demonstrate that powder undergoes spontaneous movement towards the upper region of the gliding arc due to the influence of electric field force.Increasing the discharge voltage,decreasing relative dielectric constant of the powder and reducing the electrode-to-sieve-plate distance all contribute to a greater involvement of powder in the GAD process,subsequently resulting in an enhanced powder concentration within the GAD region.Additionally,powder located beneath the gliding arc experiences downward resistance caused by the opposing gas flow and arc.Excessive gas flow rate notably hampers the powder concentration within the discharge region,and the velocity of powder motion in the upper part of the GAD region is reduced.Under the condition of electrode-to-sieve-plate distance of 30 mm,gas flow rate of 1.5 L/min,and peak-to-peak voltage of 31 kV,the best combination of arc gliding and powder spark discharge phenomena can be achieved with the addition of Al_(2)O_(3) powder.

Mass transfer process of peanut protein extracted by bis(2-ethylhexyl)sodium sulfosuccinate reverse micelles

The liquid-liquid extraction method using reverse micelles can simultaneously extract lipid and protein of oilseeds,which have become increasingly popular in recent years.However,there are few studies on mass transfer processes and models,which are helpful to better control the extraction process of oils and proteins.In this paper,mass transfer process of peanut protein extracted by bis(2-ethylhexyl)sodium sulfosuccinate(AOT)/isooctane reverse micelles was investigated.The effects of stirring speed(0,70,140,and 210 r/min),temperature of extraction(30,35,40,45,and 50℃),peanut flour particle size(0.355,0.450,0.600,and 0.900 mm)and solidliquid ratio(0.010,0.0125,0.015,0.0175,and 0.020 g/mL)on extraction rate were examined.The results showed that extraction rate increased with temperature rising,particle size reduction as well as solid-liquid ratio increase respectively,while little effect of stirring speed(P>0.05)was observed.The apparent activation energy of extraction process was calculated as 10.02 kJ/mol and Arrhenius constant(A)was 1.91 by Arrhenius equation.There was a linear relationship between reaction rate constant and the square of the inverse of initial particle radius(1/r_(0)^(2))(P<0.05).This phenomenon and this shrinking core model were anastomosed.In brief,the extraction process was controlled by the diffusion of protein from the virgin zone interface of particle through the reacted zone and it was in line with the first order reaction.Mass transfer kinetics of peanut protein extracted by reverse micelles was established and it was verified by experimental results.The results provide an important theoretical guidance for industrial production of peanut protein separation and purification.

Heat and Mass Transfer on Non-Newtonian Peristaltic Flow in a Channel in Presence of Magnetic Field: Analytical and Numerical Analysis

A study has been arranged to investigate the flow of non-Newtonian fluid in a vertical asymmetrical channel using peristalsis. The porous medium allows the electrically conductive fluid to flow in the channel, while a uniform magnetic field is applied perpendicular to the flow direction. The analysis takes into account the combined influence of heat and mass transfer, including the effects of Soret and Dufour. The flow’s non-Newtonian behavior is characterized using a Casson rheological model. The fluid flow equations are examined within a wave frame of reference that has a wave velocity. The analytic solution is examined using long wavelengths and a small Reynolds number assumption. The stream function, temperature, concentration and heat transfer coefficient expressions are derived. The bvp4c function from MATLAB has been used to numerically solve the transformed equations. The flow characteristics have been analyzed using graphs to demonstrate the impacts of different parameters.

Analysis and modeling of alumina dissolution based on heat and mass transfer

A comprehensive heat and mass transfer model of dissolution process of non-agglomerated and agglomerated alumina particles was established in an aluminum reduction cell. An appropriate finite difference method was used to calculate the size dissolution rate, dissolution time and mass of alumina dissolved employing commercial software and custom algorithm based on the shrinking sphere assumption. The effects of some convection and thermal condition parameters on the dissolution process were studied. The calculated results show that the decrease of alumina content or the increase of alumina diffusion coefficient is beneficial for the increase of size dissolution rate and the decrease of dissolution time of non-agglomerated particles. The increase of bath superheat or alumina preheating temperature results in the increase of size dissolution rate and the decrease of dissolution time of agglomerated particles. The calculated dissolution curve of alumina（mass fraction of alumina dissolved） for a 300 k A aluminum reduction cell is in well accordance with the experimental results. The analysis shows that the dissolution process of alumina can be divided into two distinct stages： the fast dissolution stage of non-agglomerated particles and the slow dissolution stage of agglomerated particles, with the dissolution time in the order of 10 and 100 s, respectively. The agglomerated particles were identified to be the most important factor limiting the dissolution process.

Mass transfer process in replacement-column purification device in zinc hydrometallurgy

It is important to remove the impurities, such as copper and cadmium, from leaching solution in zinc hydrometallurgy. To improve purification efficiency, a replacement-column purification device was proposed and its mass transfer characteristics and purification efficiency were experimentally studied. The results show that purification efficiency increases with the decrease of the zinc powder diameter and decreases with the increase of solution velocity. If appropriate structure and operation parameters are used, it is possible to make purification efficiency more than 99%, but the diameter of zinc powder should be larger than 0.45 mm. For the velocity of 0.05-0.7 cm/s, mass transfer coefficient kc is in the range of 3.94×10-7-2.76×10-6 m/s, and increases with the decrease of zinc powder diameter and the increase of solution velocity. Moreover, it can be derived by mass transfer correlations of Sherwood number:Sh=0.1069Re0.5Sc0.33, for 0.3<Re<6.

Computational Mass Transfer Method for Chemical Process Simulation

The recent works on the development of computational mass transfer （CMT） method and its applications in chemical process simulation are reviewed. Some development strategies and challenges in future research are also discussed.

Gas–liquid mass transfer and flow phenomena in the Peirce–Smith converter: a water model study

A water model with a geometric similarity ratio of 1：5 was developed to investigate the gas-liquid mass transfer and flow charac- teristics in a Peirce-Smith converter. A gas mixture of CO2 and Ar was injected into a NaOH solution bath. The flow field, volumetric mass transfer coefficient per unit volume （Ak/V; where A is the contact area between phases, V is the volume, and k is the mass transfer coeffi- cient）, and gas utilization ratio （t/） were then measured at different gas flow rates and blow angles. The results showed that the flow field could be divided into five regions, i.e., injection, strong loop, weak loop, splashing, and dead zone. Whereas the Ak/V of the bath increased and then decreased with increasing gas flow rate, and n steadily increased. When the converter was rotated clockwise, both Ak/F and t/increased. However, the flow condition deteriorated when the gas flow rate and blow angle were drastically increased. Therefore, these para- meters must be controlled to optimal conditions. In the proposed model, the optimal gas flow rate and blow angle were 7.5 m3.h-1 and 10°, respectively.

Prediction of Distillation Column Performance by Computational Mass Transfer Method

A computational mass transfer model is proposed for predicting the concentration profile and Murphree efficiency of sieve tray distillation column. The proposed model is based on using modified c＇2 -εc＇ two equations formulation for closing the differential turbulent mass transfer equation with improvement by considering the vapor injected from the sieve hole to be three dimensional. The predicted concentration distributions by using proposed model were checked by experimental work conducted on a sieve tray simulator of 1.2 meters in diameter for desorbing the dissolved oxygen in the feed water by blowing air. The model predictions were confirmed by the experimental measurement. The validation of the proposed model was further tested by comparing the simulated result with the performance of an industrial scale sieve tray distillation column reported by Kunesh et al. for the stripping of toluene from its water solution. The predicted outlet concentration of each tray and the Murphree tray efficiencies under different operating conditions were in agreement with the published data. The simulated turbulent mass transfer diffusivity on each tray was within the range of the experimental result in the same sieve column reported by Cai et al. In addition, the prediction of the influence of sieve tray structure on the tray efficiency by using the proposed model was demonstrated.

Determination of Mass Transfer Parameters During Deep Fat Frying of Rice Crackers

The accuracy of the knowledge of mass transfer parameters （effective moisture diffusivity, mass transfer Biot number and mass transfer coefficient） in the case of frying food, is essential and important for designing, modeling and process optimization. This study is undertaken to develop an approach for determining mass transfer parameters during frying of spherical rice cracker in sunflower oil at 150, 170 and 190 ℃. These parameters were evaluated from the plots of dimensionless concentration ratios against time of frying. Effective moisture diffusivity, mass transfer Biot number and mass transfer coefficient ranged between 1.24×10^-8 to 2.36×10^-8 m^2/s, 1.96 to 2.34 and 5.51×10^-6 to 9.70×10^-6 m/s, respectively. Effective moisture diffusivity and mass transfer coefficient were found to increase with an increasing frying temperature, whereas mass transfer Biot number decreased. An Arrhenius-type relationship was found between effective diffusivity coefficient and frying temperature.

Mass transfer mechanism and relationship of gas–liquid annular flow in a microfluidic cross-junction device

Mass transfer performance of gas–liquid two-phase flow at microscale is the basis of application of microreactor in gas–liquid reaction systems.At present,few researches on the mass transfer property of annular flow have been reported.Therefore,the mass transfer mechanism and relationship of gas–liquid annular flow in a microfluidic cross-junction device are studied in the present study.We find that the main factors,i.e.,flow pattern,liquid film thickness,liquid hydraulic retention time,phase interface fluctuation,and gas flow vorticity,which influence the flow mass transfer property,are directly affected both by gas and liquid flow velocities.But the influences of gas and liquid velocities on different mass transfer influencing factors are different.Thereout,the fitting relationships between gas and liquid flow velocities and mass transfer influencing factors are established.By comparing the results from calculations using fitting equations and simulations,it shows that the fitting equations have relatively high degrees of accuracy.Finally,the Pareto front,namely the Pareto optimal solution set,of gas and liquid velocity conditions for the best flow mass transfer property is obtained using the method of multi-objective particle swarm optimization.It is proved that the mass transfer property of the gas–liquid two-phase flow can be obviously enhanced under the guidance of the obtained Pareto optimal solution set through experimental verification.

A review on single bubble gas–liquid mass transfer

It is common to empirically correlate volumetric mass transfer coefficient kLa for predicting gas–liquid mass transfer in industrial applications,and the investigation of single bubble mass transfer is crucial for a detailed understanding of mass transfer mechanism.In this work,experiments,models and simulations based on the experimental results were highlighted to elucidate the mass transfer between single bubbles and ambient liquid.The experimental setups,measurement methods,the mass transfer of single bubbles in the Newtonian and the nonNewtonian liquid,models derived from the concept of eddy diffusion,the extension of Whitman’s,Higbie’s and Danckwerts’models,or dimensionless numbers,and simulation methods on turbulence,gas–liquid partition methods and mass transfer source term determination are introduced and commented on.Although people have a great knowledge on mass transfer between single bubbles and ambient liquid in single conditions,it is still insufficient when facing complex liquid conditions or some phenomena such as turbulence,contamination or non-Newtonian behavior.Additional studies on single bubbles are required for experiments and models in various liquid conditions in future.

A simulating investigation into the characteristics of the mass transfer between molten steel and particles in the 150 t RH-IJ refining

The characteristics of the mass transfer between powder particles and liquid steel in the Ruhrstahl Heraeus process injection （RH-IJ） refining were simulatively investigated by the use of a 1/4 scale water model of a 150 t Ruhrstahl Heraeus（RH） degasser. The influences of the lifting gas flow rate, the up-snorkel and down-snorkel inner diameters and the size of powder particles on the characteristics of the mass transfer were examined. The results show that under the condition that the inner diameters of both the up-snorkel and the down-snorkel are the same, the mass transfer coefficient in the liquid,k increases with the increase of the inner diameter of the up-snorkel,the particle size and the lifting gas flow rate （Q1）. However, the increase of Q~ should not result in a saturated circulation rate. Under the current working condition,k ranges from 3. 392 × 10 -5 m/s to 2. 661 × 10-4 m/s. On the other hand,with a given lifting gas flow rate and up-snorkel inner diameters ,the mass transfer weakens with the increase of the down-snorkel inner diameter. An inherently nonlinear relationship between the circulation rate （Q~） of molten steel in the RH degasser and k,which increases with the increase of Q1,was found. Under the condition of other parameters being the same,k increases with the increase of the powder particle size. In order to enhance the mass transfer,it is better not to use extremely fine powder.

Mass transfer analysis for microwave hot in-place recycling of asphalt pavements

In order to realize mass transfer analysis for microwave hot in-place recycling of asphalt pavements, a volume element is established including asphalt mixtures, liquid water and vapor. A mass transfer control model is built by the theory of multiphysics, phase transformation and diffusion. The model contains continuity equation, energy conservation equation, movement equation and vapor diffusion equation. To gain the solution of the mass transfer model, the formulas are simplified to one-dimensional differential equations. And then a mathematical model of boundary conditions is established. The mass transfer velocity and dissipative energy are obtained in different moisture contents through simulation of asphalt pavements recycling. The result indicates that when initial moisture content is certain, mass transfer velocity is almost uniform in depth direction at the same heating time and enertrv absorbed by water i,~ descendino with denletion of moisture.

Shear Alteration, Mass Transfer and Gold Mineralization: An Example from Jiaodong Ore Deposit Concentrating Area, Shandong, China

Taking the gold ore deposit concentrating area of Jiaodong area in Shandong, China for an example, based on geological analysis, and applying Gresens’ equation, Grant’s isocon diagram and O’hara microelement calculation method, a thorough study on shear alteration, mass transfer and gold mineralization was carried out. The authors also made mathematic simulation and geochemical analysis. The work reveals temporal spatial changing regularities of temperature field and velocity field of fluids, and also reveals fluid transport chemical reaction coupling metallogenic dynamics of the Jiaojia gold ore concentrating area. During shear alteration process of the Jiaodong gold ore concentrating area, all kinds of components transferred with different amounts, fluid rock ratio was rather high and volume strain was of dilation type. Fast flow of ore forming fluid favors the occurrence of mixed fluid. Shear fractured zones are places where there was strong transportation reaction coupling mineralization. Ore bodies were located in dilation space of shear structure where there was the greatest fluid flux. After the emplacement of the rock body, a convex heat field was formed around the rock body. It is one of the main metallogenic forces. The major reason for mineralization is the mobilization, migration and enrichment of ore forming elements induced by shear compressive extensional tectonism. Inclusion gold dominant low grade ores were formed in the early ore forming stage, while high grade ores, which contained fissure gold and polymetallic veinlets, were formed in late ore forming stage.