活性炭纤维填充床内多组分竞争吸附

建立了活性炭纤维填充床内多组分竞争吸附传质动力学模型 ,采用正交配置方法求解数学模型以预测突破曲线 ,从理论上探讨了竞争吸附平衡及吸附质在填充床内的轴向弥散、纤维内扩散和纤维外对流传质等因素对强、弱吸附组分突破曲线的影响。在间歇和填充床吸附器内进行了脱除水溶液中酚类化合物的实验 ,测定了活性炭纤维吸附水溶液中苯酚和氯代苯酚的吸附等温线 (间歇吸附 )以及苯酚和氯代苯酚在活性炭纤维填充床内竞争吸附时的突破曲线 ,并与模型计算值进行了比较。结果表明 ,吸附质在活性炭纤维内扩散和纤维外对流传质阻力不是填充床内吸附过程的控制步骤 ,而轴向弥散影响显著 ,不可忽略     

大型液相色谱分离过程参数辨识新方法

本文提出大型液相色谱分离过程流体轴向扩散系数、吸附相平衡常数和总传质系数参数辨识模型,用惰性物为示踪剂扰动应答实验技术和色谱测量技术测定参数。结果表明:在轴向扩散中,涡流扩散占主导地位;轴向扩散系数随流体流速以及装填密度的增大而增大;相平衡常数比总传质系数有较高灵敏度;葡萄糖果糖的相平衡常数随温度的升高而降低,而总传质系数随流体流速和温度的增大而增大;得到理论流出曲线与实验流出曲线一致的结果。     

LIQUID PHASE TRANSPORT PROPERTIES IN A HIGH PRESSURE PACKED COLUMN

A mathematical model of fluid flow and mass transfer in a packed bed was derived and used to evaluate the liquid phase axial dispersion and mass transfer coefficients under high pressure conditions. The least-squares method was used to evaluate the rate parameters from experimental breakthrough curves, and the agreement between the concentration curves predicted from rate parameters and those measured experimentally was good. Experiments were performed at 20 and 200°C with water as a solvent and nonporous soda-lime glass beads as packing. Although the axial dispersion coefficient was independent of temperature and pressure, the mass transport parameters were found to be pressure dependent.     

The gas–liquid contacting effect on the operation of small scale upflow hydrotreaters

The effect of reactor geometry and bed dilution on the extent of gas oil hydrodesulfurization was tested by conducting hydrodesulfurization experiments in two laboratory reactors of different scale with non-diluted and diluted beds in ascending flow. The superficial gas and liquid velocities and the catalyst bed height were kept constant while the main difference between the two reactor scales was the reactor diameter. The diluted bed of the mini-reactor showed the best performance and its results were identical in upflow and downflow mode. The differences between the performance of the mini- and the bench-scale reactor operating in upflow mode have been investigated. Reactor performance simulation was attempted by a mathematical model that takes into account axial dispersion of the liquid phase and gas–liquid mass transfer. Bench-scale reactor operation was characterized by lower mass transfer rates than the corresponding mini-scale one. Combining model predictions and mock up operation it is concluded that the stronger mass transfer resistances calculated for the bench-scale reactor are associated with poorer gas distribution through the catalyst bed. Reduction of the bed diameter results in better gas–liquid contact by forcing the gas bubbles to distribute more effectively into the liquid phase.     

New Approach in the Prediction of RDC Liquid‐Liquid Extraction Column Parameters

The liquid‐liquid extraction process is well‐known for its complexity and often entails intensive modeling and computational efforts to simulate its dynamic behavior. This paper presents a new application of the Genetic Algorithm (GA) to predict the modeling parameters of a chemical pilot plant involving a rotating disc liquid‐liquid extraction contactor (RDC). In this process, the droplet behavior of the dispersed phase has a strong influence on the mass transfer performance of the column. The mass transfer mechanism inside the drops of the dispersed phase was modeled by the Handlos‐Baron circulating drop model with consideration of the effect of forward mixing. Using the Genetic Algorithm method and the Numerical Analysis Group (NAG) software, the mass transfer and axial dispersion coefficients in the continuous phase in these columns were optimized. In order to obtain the RDC column parameters, a least‐square function of differences between the simulated and experimental concentration profiles (SSD) and 95 % confidence limit in the plug flow number of the transfer unit prediction were considered. The minus 95 % confidence limit and sum of square deviations for the GA method justified it as a successful method for optimization of the mass transfer and axial dispersion coefficients of liquid‐liquid extraction columns.     

Liquid-fluidized magnetically stabilized beds

The fluid mechanics of liquid-fluidized magnetically stabilized beds (MSBs) have been studied to determine their operating characteristics and properties. Experiments were conducted to study the operating regimes, bed expansion and pressure drop, and axial liquid dispersion.Several regimes exist for magnetized, liquid-fluidized beds. These include the unfluidized or packed, stable, roll-cell, and random motion regimes. The transition between the stable and roll-cell regimes was found to be strongly dependent on the type of fluid distributor grid used. A hysteresis was found in both the pressure drop and bed expansion behavior. With decreasing liquid velocity, the pressure drop through the bed fell immediately to a value below the weight of the bed and the bed remained expanded even after the liquid flow had ceased. The height of the bed in the stable regime was found to depend on the liquid velocity but not on the strength of the magnetic field.Contacting experiments indicate axial dispersion in a liquid-fluidized MSB to be nearly the same as for packed beds and independent of the path taken to the stable operating condition.     

整体式床层中液体分布与气-液传质的关系

With a particular focus on the connection between liquid flow distribution and gas-liquid mass transfer in monolithic beds in the Taylor flow regime, hydrodynamic and gas-liquid mass transfer experiments were carried out in a column with a monolithic bed of cell density of 50 cpsi with two different distributors (nozzle and packed bed distributors). Liquid saturation in individual channels was measured by using self-made micro-conductivity probes. A mal-distribution factor was used to evaluate uniform degree of phase distribution in monoliths. Overall bed pressure drop and mass transfer coefficients were measured. For liquid flow distribution and gas-liquid mass transfer, it is found that the superficial liquid velocity is a crucial factor and the packed bed distributor is better than the nozzle distributor. A semi-theoretical analysis using single channel models shows that the packed bed distributor always yields shorter and uniformly distributed liquid slugs compared to the nozzle distributor, which in turn ensures a better mass transfer performance. A bed scale mass transfer model is proposed by employing the single channel models in individual channels and incorporating effects of non-uniform liquid distribution along the bed cross-section. The model predicts the overall gas-liquid mass transfer coefficient with a relative error within ±30%.     

三相循环流化床中的气液相界面积和传质系数

采用溶氧法测量了三相循环流化床中液相溶氧浓度的轴向分布,并按轴向扩散模型处理实验数据,优化得到气液体积传质系数kLa,同时用光纤探头测量了体系中的气含率和气泡大小分布,计算得到了气液相界面积a和气液传质系数kL,并研究了主要操作条件(表观气速、表观液速和固含率)对气液传质系数的影响规律.     

Liquid—liquid extraction column (rotating disc contactor)—model parameters from drop size distribution and solute concentration measurements

The practical application of an extraction column model which takes into account the influence of drop-size distribution (i.e. the ‘forward mixing’ model) is brought forward by the generation, from experimental data, of values of the mass transfer and axial dispersion coefficients required by the model. Values of these coefficients were generated from drop-size distribution and solute concentration profile measurements in a 22 cm diam. rotating disc contactor. The use of the Handlos-Baron drop mass transfer model is justified. The resulting continuous phase transfer coefficients were found to be dependent only on disc speed. Continuous phase axial dispersion coefficients were much higher than tracer-correlation predicted values at higher flows, and larger drop sizes. An explanation for this is presented.     

Gas-Liquid mass transfer in fixed beds with two-phase cocurrent downflow: Gas/newtonian and non-newtonian liquid systems

New data of gas-liquid mass transfer for cocurrent downflow through packed beds of porous and non-porous particles are presented. Mass transfer parameters for air/carbon dioxide/water, air/carbon dioxide/carboxymethylcellulose solution and air/carbon dioxide/sodium hydroxide systems were evaluated by least square fit of the calculated CO₂ concentration profiles in gas phase to the experimental values. The volumetric liquid-side mass transfer coefficient increases with the increase of the flow consistency index of the liquid. A comparison of the volumetric liquid-side mass transfer coefficient values evaluated with and without taking into account the axial dispersion shows that the influence of the liquid axial dispersion is significant at low liquid velocity and high CMC concentrations, and the influence of the gas axial dispersion is insignificant.     

Mathematical modeling of penicillin G Extraction by a bifunctional surfactant in a continuous extraction column

A bifunctional surfactant was used as a carrier of penicillin G for its continuous extraction by an emulsion liquid membrane without an extradant in a countercurrent extraction column of Oldshue-Rushton type. A permeation model was presented to describe transport mechanism of penicillin G in the continuous extraction system, including an axial dispersion model for the continuous phase and a mass transfer model for the dispersed emulsion phase. The mass transfer model describes the external mass transfer around the emulsion drop, the reaction at the external interface, the diffusion as well as the reaction equilibrium within the w/o emulsion drop, and the pH change of internal aqueous phase. Here, we considered three experimental variables: penicillin G concentration, pH of continuous phase and surfactant concentration. The calculated results from the permeation model fitted the experimental data well. This paper is dedicated to Dr. Youn Yong Lee on the occasion of his retirement from Korea Institute of Science and Technology.     

Interpretation of mass transfer measurements in bubble columns considering dispersion of both phases

Mass transfer measurements in two bubble columns with an inner diameter of 100 resp. 140 mm with the systems air/water/carbon dioxide and nitrogen/n-propanol/carbon dioxide have been evaluated with the axial dispersion model. The dispersion coefficients of both phases have been determined in separate investigations. As the results revealed a strong influence of the liquid viscosity, additional dispersion coefficient measurements have been carried out with the system air/glycol. It could be shown that the liquid phase dispersion coefficient decreases with increasing viscosity while the gas phase dispersion coefficient increases with increasing liquid viscosity. Both coefficients are strongly dependent on the gas throughput and the column diameter. Using these coefficients, the mass transfer coefficients have been calculated by fitting the calculated concentration profile to the measured values and by splitting the volumetric mass transfer coefficient with the experimental value of the interfacial are a. The results agree best with a correlation of Calderbank and Moo-Young.     

A 3-zone model for protein adsorption kinetics in expanded beds

The adsorption behavior of expanded beds is more complex than that of fixed beds, since the adsorbent particle size, local bed voidage and liquid axial dispersion will vary axially with expanded height. Models applicable to fixed beds maybe not adequately describe the hydrodynamic and adsorption behavior in expanded beds. In this paper, a 3-zone model is developed, in which the model equations are written for the bottom zone, middle zone, and top zone of the column, respectively, and the model parameters, such as the adsorbent particle diameter, bed voidage and liquid axial dispersion coefficient, are zonal values. In-bed breakthrough curves are predicted by the 3-zone model, and tested against literature data for lysozyme adsorption on Streamline SP in an expanded bed.Model parametric sensitivity is analyzed. The effects of film mass transfer resistance, liquid axial dispersion and adsorbent axial dispersion on the breakthrough curves are weaker than that of protein intraparticle diffusion resistance for stable expanded beds. Adsorbent particle size axial distribution and bed voidage axial variation significantly affect in-bed breakthrough curves, therefore, model parameters should not be assigned uniform values over the whole column; instead the model should account for the adsorbent particle size axial distribution and bed voidage axial variation.     

Dynamic analysis of a trickle bed reactor by moment technique

The performance of a trickle bed reactor is investigated by the moment technique. Residence time distributions of SO₂ tracer in both gas (Helium) and liquid (distilled water) effluents are used to predict zero reduced and first absolute moments and these values are compared with the derived theoretical expressions. Correlations are suggested for gas-liquid mass transfer coefficient, liquid hold up, and extent of axial mixing in liquid phase.True adsorption equilibrium constant of the system is estimated as 0.378 from liquid full bed experiments and contacting efficiency of the trickle bed reactor is found as 0.987.Effect of axial dispersion is not significant on gas-liquid mass transfer coefficient since absorption factor is small, but is found to be quite important on the true estimation of adsorption factor.     

Effect of interfacial mass transfer on the dispersion in segmented flow in straight capillaries

The effect of interfacial mass transfer on the extent of dispersion in liquid‐liquid segmented flow in straight capillaries is studied. In the absence of interfacial mass transfer, dispersion coefficient was seen to go through a minimum with increasing flow rates. In the presence of mass transfer, physicochemical properties of both the phases and slug lengths were seen to vary along the capillary length. The extent of dispersion was always higher in the presence of interfacial mass transfer. The predictions using axial dispersion model deviated noticeably for larger capillaries as the model does not account for varying buoyancy, dynamic contacting, and Marangoni convection. Simulations of a first‐order interfacial reaction considering varying slug lengths showed a significant change in optimum operating parameters than the conventional approach. A special case of “drop‐on‐demand” type of controlled two‐phase flow in capillaries was also studied. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4294–4308, 2015     

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 a...     

气液固三相循环流化床气液传质行为

<正>气液固三相流化床反应器在石油化工、湿法冶金、环境工程和煤的液化等工业领域得到了广泛应用,其基础研究也取得了很大进展.但是,传统三相床主要应用于低液速(U_L<     

阶梯环填料层流体力学和传质性能研究

本文研究了16 mm聚丙烯阶梯环填料层的压强降和液流的分布特性,研究了液相传质性能。获得了压强降填料因子、泛点填料因子,以及液相真实传质单元高度的关联式。结果表明,阶梯环填料对液体分布的保持性能好,分散常数C值比同尺寸的拉西环大23.4％;传质单元高度比同尺寸的拉西环低20～45％。     

Investigation of hydrodynamic and mass transfer of mercaptan extraction in pulsed and non-pulsed packed columns

We investigated the hydrodynamic behavior and mass transfer characteristics of a pilot-scale conventional packed bed extraction column of mercaptan removal from liquid propane. The extraction column was filled with pall rings structured packing where mercaptan was extracted from the continuous phase to the dispersed phase, accompanied by a chemical reaction in propane-mercaptan-caustic system. The pulsing was introduced into the column to enhance the mass transfer rate. Hydrodynamic parameters such as hold up, flooding velocity and mean drop size were studied together with the effect of chemical reaction on increasing mass transfer performance. Finally, the mass transfer and axial mixing coefficients were obtained from the optimization of data by ADM. It was found that at the pulsation intensity from 0.003 to 0.007 m/s, the maximum mass transfer and minimum axial mixing occurred and it can be concluded that pulsation improves the efficiency of mass transfer just at low intensities.     

“FORWARD MIXING” MODEL: APPLICATION TO PULSED PLATE EXTRACTION COLUMN OPERATION IN THE EMULSION REGION

The “Forward Mixing” model has been applied to data obtained from a 22 cm diameter pulsed plate extraction column. Measurements of drop size distributions, dispersed phase hold-up and concentration profiles for two systems (toluene-acetone-water and n-butanol-succinic acid-water) of quite different properties were made with the column operating in the emulsion region. Generated drop size distribution function parameters, size-dependent slip velocities and mass transfer coefficients, and continuous phase axial dispersion coefficients were accurate in predicting dispersed phase hold-up and extraction efficiencies (or the related plug flow number of transfer units). These parameters were correlated with phase superficial velocities and pulse velocities. The influence of continuous phase axial dispersion was much greater than the influence of drop size variation, and was not accurately predicted by most previous tracer-based correlations. An inlet dispersed phase distributor was beneficial to the performance with the high interfacial tension system.