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 of phosphorus in high-phosphorus hot-metal refining

Mass transfer of phosphorus in high-phosphorus hot-metal refining was investigated using CaO-FetO-SiO2 slags at 1623 K. Based on a two-film theory kinetic model and experimental results, it was found that the overall mass transfer coefficient, which includes the effects of mass transfer in both the slag phase and metal phase, is in the range of 0.0047 to 0.0240 cm/s. With the addition of a small amount of fluxing agents A1203 or Na20 into the slag, the overall mass transfer coefficient has an obvious increase. Silicon content in the hot metal also influences the overall mass transfer coefficient. The overall mass transfer coefficient in the lower [Si] heat is much higher than that in the higher [Si] heat. It is concluded that both fluxing agents and lower [Si] hot metal facilitate mass transfer of phosphorus in liquid phases. Fur- thermore, the addition of Na20 could also prevent rephosphorization at the end of the experiment.

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.

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.

Experimental determination of gas holdup and volumetric mass transfer coefficient in a jet bubbling reactor

The hydrodynamics and mass transfer characteristics of a lab-scale jet bubbling reactor(JBR)including the gas holdup,volumetric mass transfer coefficient and specific interfacial area were assessed experimentally investigating the influence of temperature,pH and superficial gas velocity.The reactor diameter and height were 11 and 30 cm,respectively.It was equipped with a single sparger,operating at atmospheric pressure,20 and 40℃,and two pH values of 3 and 6.The height of the liquid was 23 cm,while the superficial gas velocity changed within 0.010-0.040 m·s^(-1)range.Experiments were conducted with pure oxygen as the gas phase and saturated lime solution as the liquid phase.The liquid-side volumetric mass transfer coefficient was determined under unsteady-state oxygen absorption in a saturated lime solution.The gas holdup was calculated based on the liquid height change,while the specific interfacial area was obtained by a physical method based on the bubble size distribution(BSD)in different superficial gas velocities.The results indicated that at the same temperature but different pH,the gas holdup variation was negligible,while the liquid-side volumetric mass transfer coefficient at the pH value of 6 was higher than that at the pH=3.At a constant pH but different temperatures,the gas holdup and the liquid-side volumetric mass transfer coefficients at 40℃were higher than that of the same at 20℃.A reasonable and appropriate estimation of the liquid-side volumetric mass transfer coefficient(kla)in a pilot-scale JBR was provided which can be applied to the design and scale-up of JBRs.

VOLUMETRIC MASS TRANSFER COEFFICIENT BETWEEN SLAG AND METAL IN COMBINED BLOWING CONVERTER

The effects of operation parameters of combined blowing converter on the volumetric mass transfer coefficient between slag and steel are studied with a cold model with water simulating steel, oil simulating slag and benzoic acid as the transferred substance between water and oil. The results show that, with lance level of 2.1m and the top blowing rate of 25000Nm3/h, the volumetric mass transfer coefficient changes most significantly when the bottom blowing rate ranges from 384 to 540Nm3/h. The volumetric mass transfer coefficient reaches its maximum when the lance level is 2.1m, the top blowing rates is 30000Nm3/h, and the bottom blowing rate is 384Nm3/h with tuyeres located symmetrically at 0.66D of the converter bottom.

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 coefficient in the eductor liquid-liquid extraction column

In this research gasoil desalting was investigated from mass transfer point of view in an eductor liquid–liquid extraction column(eductor-LLE device).Mass transfer characteristics of the eductor-LLE device were evaluated and an empirical correlation was obtained by dimensional analysis of the dispersed phase Sherwood number.The Results showed that the overall mass transfer coefficient of the dispersed phase and extraction efficiency have been increased by increasing Sauter mean diameter(SMD)and decreasing the nozzle diameter from 2 to 1 mm,respectively.The effects of Reynolds number(R_(e)),projection ratio(ratio of the distance between venturi throat and nozzle tip to venturi throat diameter,Rpr),venturi throat area to nozzle area ratio(R_(th-n))and two phases flow rates ratio(R_(Q))on the mass transfer coefficient(K)were determined.According to the results,K increase with increasing Re and RQ and also with decreasing Rpr and R_(th-n).Semi-empirical models of drop formation,rising and coalescence were compared with our proposed empirical model.It was revealed that the present model provided a relatively good fitting for the mass transfer model of drop coalescence.Moreover,experimental data were in better agreement with calculated data with AARE value of 0.085.

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.

Predicting Mass Transfer Extraction with Steam Flow, Applying Boundary-Layer Concepts

Theory and concepts of boundary layer mass transfer is applied to correlate experimental data on extraction of essential oils from vegetable leaves and stems, using steam. From these theory, concepts and experimental data with seven systems, two correlations are developed to predict the Sherwood number and mass transfer coefficient as function of Reynolds and Schmidt numbers. From these equations, the molar flux, the amount of solute extracted, and the yield of extraction is predicted. A steam of higher temperature normally improves the mass transfer and the yield. A method to estimate the enhancement for temperature increase is proposed. The correlations developed are applied to a case with industrial size that was no part of the data for correlation generation. Theory may be applied for industrial applications.

A convenient method for measuring gas-liquid volumetric mass transfer coefficient in micro reactors

The research on gas-liquid multiphase reactions using micro reactors is becoming increasingly widespread, given their excellent mass transfer performance. Establishing an accurate and reliable method to measure the gas-liquid mass transfer performance of micro reactors is crucial for evaluating and optimizing the design of micro reactor structure. In this paper, the physical absorption method of aqueous solution-CO_(2) and the chemical absorption method of sodium carbonate solution-CO_(2) were proposed. By analyzing the chemical reaction equilibrium during the absorption process, the relationship between the mass transfer of CO_(2) and the solubility of hydroxide ions in the solution was established, and the total gas-liquid mass transfer coefficient was immediately obtained by measuring the p H value. The corresponding testing platform and process have been established based on the characteristics of the proposed method to ensure fast and accurate measurement. In addition, the chemical absorption method takes into account temperature factors that were not previously considered. The volumetric mass transfer coefficient measured by these two methods is in the same range as those measured by other methods using the same microchannel structure in previous literature. The methods have the advantages of low equipment cost, faster measurement speed, and simpler procedures, which can facilitate its wide application to the evaluation of the mass transfer performance and hence can guide the structure optimization of microchannel reactors.

PERVAPORATION PROPERTIES OF PDMS MEMBRANES CURED WITH DIFFERENT CROSS-LINKING REAGENTS FOR ETHANOL CONCENTRATION FROM AQUEOUS SOLUTIONS

Ethanol perm-selective PDMS/PVDF composite membranes were prepared by curing polydimethylsiloxane (PDMS) with various cross-linking reagents,such as tetraethoxylsilane(TEOS),γ-aminopropyltriethoxylsilane(APTEOS), phenyltrimethoxylsilane(PTMOS) and octyltrimethoxylsilane(OTMOS) as well.The cross-linking density and surface properties of the PDMS active layer were adjusted by varying cross-linking reagents.The pervaporation performance of PDMS membranes cured with different cross-linking reagents was investig...

Simulation research on oxygen mass transfer between steel and slag in IF steel refining process

The effects of oxidizing slag on oxygen mass transfer and inclusions in different stages of IF(interstitial-free)steel refining were investigated by several heat simulation experiments.The results of the experiments showed that the oxidizability of slag changed considerably during different refining stages.Keeping the content of FeO in the slag within 1 wt.%would narrow the difference of slag oxidizability,stabilize the content of[Al]s in the steel,avoid secondary oxidation of molten steel by the slag,and reduce the inclusions.When the mass transfer of FeO in the slag phase was a limiting step,the secondary oxidation reaction occurred at the steel–slag interface;when the diffusion of oxygen in the molten steel was a limiting step,the secondary oxidation reaction took place inside the molten steel.The oxygen transfer rate was affected by the mass transfer coefficient of oxygen.For every 0.0001m/s increase in mass transfer coefficient,the oxygen transfer rate increased by about 2.2×10^-6 min^-1.By changing the mass transfer coefficient,the oxygen transfer rate of the slag to the molten steel can be controlled.

FLOW BEHAVIOR AND MASS TRANSFER IN THREE-PHASE EXTERNAL-LOOP AIRLIFT REACTORS WITH LARGE PARTICLES

The flow behavior and mass transfer in a three-phase external-loop airlift reactor can be improved by adding large particles. The mass transfer and liquid dispersion behavior for a three-phase external-loop reactor with large particles are studied in terms of the effect of the diameter and loading of the large particles on the liquid dispersion coefficient and mass transfer coefficient, The results showed that increasing the diameter or loading of the large particles tend to decrease dispersion and intensify mass transfer, and that an increase in the diameter of the large particles remarkably decreases the particle loop rate, while the effect of fine particles is much less notable.

Gas-liquid mass transfer in the gas-liquid-solid mini fluidized beds

The gas-liquid-solid mini fluidized bed(GLSMFB)combines the advantages of fluidized bed and micro-reactor,and meets the requirements for safety and efficiency of green development of process industry.However,there are few studies on its flow performance and no studies on its mass and heat transfer performance.In this paper,the characteristics of gas-liquid mass transfer in a GLSMFB were studied in order to provide basic guidance for the study of GLSMFB reaction performance and application.Using CO_(2)absorption by NaOH as the model process,the gas-liquid mass transfer performance of GLSMFB was investigated.The results show that the liquid volumetric mass transfer coefficient and the gas-liquid interfacial area both increase with the increase of the superficial gas velocity within the experimental parameter range under the same given superficial liquid velocity.At the same ratio of superficial gas to liquid velocity,the liquid volumetric mass transfer coefficient increases with the increase of the super-ficial liquid velocity.Fluidized solid particles strengthen the liquid mass transfer process,and the liquid volumetric mass transfer coefficient is about 13%higher than that of gas-liquid mini bubble column.

Investigation of the kinetic mechanism of the demanganization reaction between carbon-saturated liquid iron and CaF2–CaO–SiO2-based slags

The demanganization reaction kinetics of carbon-saturated liquid iron with an eight-component slag consisting of CaO–SiO2–MgO–FeO–MnO–Al2O3–TiO2–CaF2 was investigated at 1553, 1623, and 1673 K in this study. The rate-controlling step（RCS） for the demanganization reaction with regard to the hot metal pretreatment conditions was studied via kinetics analysis based on the fundamental equation of heterogeneous reaction kinetics. From the temperature dependence of the mass transfer coefficient of a transition-metal oxide（MnO）, the apparent activation energy of the demanganization reaction was estimated to be 189.46 kJ·mol^–1 in the current study, which indicated that the mass transfer of MnO in the molten slag controlled the overall rate of the demanganization reaction. The calculated apparent activation energy was slightly lower than the values reported in the literature for mass transfer in a slag phase. This difference was attributed to an increase in the ＂specific reaction interface＂（SRI） value, either as a result of turbulence at the reaction interface or a decrease of the absolute amount of slag phase during sampling, and to the addition of calcium fluoride to the slag.

A more precise method to evaluate kinetic leakage of anion exchange resin used in condensate polishing of power plant

Sulfate mass transfer coefficient(MTC) is a sensitive parameter to evaluate the kinetic leakage of anion exchange resin used in condensate polishing system of thermal and nuclear power plant.However,a sufficiently precise determination method has not been well established.In this paper,the final expression of sulfate MTC derived based on plug flow reactor model is the same as Harries' model,which is widely acknowledged in this field.In the determining system we constructed,in-situ calibration of the concentration of sulfate and its cation conductivity was conducted and sulfate MTCs of four typical strongly basic anion exchange resin samples were determined.The systematic error is 8.26% and the calibrated curve used for quantifying sulfate is obtained.The repeatability and reproducibility standard deviation are 0.05×10^(-4) m·s^(-1) and 0.07×10^(-4) m·s^(-1) respectively,which are lower than previous works.By controlling test condition accurately,this study has developed a more precise sulfate MTC determining method.This method provides a basis for further research.

Heat and mass transfer through spiral tubes in absorber of absorption heat pump system for waste heat recovery

Heat and mass transfer of a LiBr/water absorption heat pump system(AHP)was experimentally studied during working a heating-up mode.The examination was performed for a single spiral tube,which was simulated for heat transfer tubes in an absorber.The inside and outside of the tube were subjected to a film flow of the absorption liquid and exposed to the atmosphere,respectively.The maximum temperature of the absorption liquid was observed not at the entrance but in the region a little downward from the entrance in the tube.The steam absorption convective heat transfer coefficient between the liquid film flowing down and the inside wall of the temperature and the film temperature at the maximum temperature location and the bottom.The film heat and mass transfer coefficients rose with increasing Reynolds number of the liquid film stream.The coefficients showed opposite trend to the empirical correlation reported for laminar film flow on a straight smooth tube in a refrigeration mode in the past work.The fact can be caused due to a turbulent promotion effect of the liquid in a spiral tube.

Predictions of equilibrium solubility and mass transfer coefficient for CO_(2) absorption into aqueous solutions of 4-diethylamino-2-butanol using artificial neural networks

In the present work,artificial neuron network(ANN)based models for predicting equilibrium solubility and mass transfer coefficient of CO_(2) absorption into aqueous solutions of high performance alternative 4-diethylamino-2-butanol(DEAB)solvent were successfully developed.The ANN models show an outstanding predictive performance over the predictive correlations proposed in the literature.In order to predict the equilibrium solubility,the ANN model were developed based on three input parameters of operating temperature,concentration of DEAB and partial pressure of CO_(2).An outstanding prediction performance of 2.4%average absolute deviation(AAD)can be obtained(comparing with 7.1–8.3%AAD from the literature).Additionally,a significant improvement on predicting mass transfer coefficient can also be achieved through the developed ANN model with 3.1%AAD(comparing with 14.5%AAD from the existing semi-empirical model).The mass transfer coefficient is considered to be a function of liquid flow rate,liquid inlet temperature,concentration of DEAB,inlet CO_(2) loading,outlet CO_(2) loading,concentration of CO_(2) along the height of the column.

Mass transfer between bubbles and the dense phasein gas fluidized beds

Mass transfer between a bubble and the dense phase in gas fluidized beds of Group A and Group B particles was proposed based on previous experimental results and literature data. The mass transfer coefficient between bubbles and the dense phase was determined by kbe = 0.21 db. A theoretical analysis of the mass transfer coefficient between a bubble and the dense phase using diffusion equations showed that the mass transfer coefficient between a bubble and the dense phase is kbe α εmf√ub/db in both three- and two-dimensional fiuidized beds. An effective diffusion coefficient in gas fluidized beds was introduced and correlated with bubble size as De = 13.3db2.7 for Group A and Group B particles. The mass transfer coefficient kbe can then be expressed as kbe = 0.492εmf√ubdb1.7 for bubbles in a three-dimensional bed and kbe = 0.576εm√ubdb1.7 for bubbles in a two-dimensional bed.