撞击流-旋转填料床萃取传质性能与微观混合效果的关系

为探寻撞击流-旋转填料床(IS-RPB)萃取效果与微观混合之间的关系,在相同操作条件下,分别对IS-RPB萃取传质性能与微观混合性能进行了实验研究。对于萃取传质性能研究过程中选用了水-苯酚-磷酸三丁酯(煤油)和煤油-苯甲酸-水2个萃取体系;对于微观混合效果的研究采用化学偶合法,以α-萘酚和对氨基苯磺酸重氮盐的串并联偶合反应为工作反应。结果表明:IS-RPB萃取传质性能与微观混合效果密切相关,在实验范围内,萃取传质性能随微观混合效果的增加而提高。通过因次分析方法,给出了描述IS-RPB设备参数、操作参数对萃取传质速率影响的关联表达式。

超临界CO_2萃取川芎挥发油过程研究

目的在萃取压力10～25MPa、萃取温度33～48℃、CO2流量2～4L/min的范围内研究了超临界CO2萃取川芎挥发油过程。考察了萃取压力、温度、流量对萃取过程的影响。方法将萃取过程考虑为CO2通过川芎固定床的模型,由Stastova提出的传质方程对不同压力、温度及CO2流量下的萃取过程进行模拟,并对不同操作条件下传质系数的变化进行了分析。结果本法在萃取川芎挥发油得到的传质系数随着温度的升高略为增大,随着流量的增大而增大,随着压力的增大而减少。结论该模型可以对超临界萃取川芎挥发油过程进行较好的描述。

Mass Transfer and Axial Mixing Characteristics in a Coalescence-Dispersion Pulsed-Sieve-Plate Extraction Column

A new configuration of coalescence-dispersed pulsed-sieve-plate extraction column (CDPSEC) was developed, and the mass transfer and axial mixing characteristics were evaluated with the two-point dynamic method.The influence of operation conditions was discussed with experimental results, showing that the mass transfer performance of CDPSEC mainly depends on the energy input and the holdup of dispersed phase. Higher energy input results in higher holdup of the dispersed phase, the axial mixing of the continuous phase is suppressed, and the true height of mass transfer unit decreases markedly. On the other hand, higher energy input leads to more serious forward mixing of the dispersed phase, so the energy input should be limited. Accordingly the operation conditions were divided into two regions, and empirical correlations for predicting the mass transfer and axial mixing characteristics in different regions with a satisfactory accuracy were suggested.

Phenol Removal from Aqueous Solution Through Hollow Fiber Membrane Extraction

In this work, mass transfer mechanism was studied for 50%TBP (in kerosene)-phenol-water as the working system in different hydrophobic microporous hollow fiber modules. The effect of different operating conditions on the removal of phenol was analyzed. Solvent entrainment in this process was detected with MALVERN-2600 laser pellet diameter analytical equipment. Experimental results indicate the mass transfer coefficient is increased while the two phase flow rates are increased. With increases in the flow rate of the water phase, the removal ratio of phenol will be decreased. Highly effective removal of phenol could be reached by changing the experimental conditions and the module configuration. The solvent entrainment in the water phase in the membrane extraction process was found to be 5%—8% of that in conventional liquid-liquid extraction process. Thus, solvent pollution could be better controlled.

Hydrodynamics and Mass Transfer Performance in Supercritical Fluid Extraction Columns

New models for describing hydrodynamics and mass transfer performance in supercritical fluid extraction columns were proposed. Those models were proved by experimental data, which were obtained in supercritical fluid extraction packed column, spray column and sieve tray column respectively. The inner diameter of those columns areФ25 mm. These experimental systems include supercritical carbon diox-ide-isopropanol-water and supercritical carbon dioxide-ethanol-water, in which supercritical carbon dioxide was dispersed phase, and another was continuous phase. The extraction processes were operated with continuous countercurrent flow. The predicted values are agreed well with experimental data.

Modeling of Mass Transfer in Nonideal Multicomponent Mixture with Maxwell-Stefan Approach

The Intalox metal tower packing was used to simulate an industrial relevant extractive distillation column for purifying azeotropic multicomponent mixture.In order to explain the inconsistencies in the modeling of transfer process in nonideal multicomponent distillation column,a method was developed with equilibrium stage models(EQ)and non-equilibrium model(NEQ)incorporated with Maxwell-Stefan diffusion equations in the framework of AspenONE simulator.Dortmund Modified UNIFAC(UNIFAC-DMD)thermodynamic model was employed to estimate activity coefficients.In addition,to understand the reason for the diffusion against driving force and the different results by EQ and NEQ models,explicit investigations were made on diffusion coefficients, component Murphree efficiency and mass transfer coefficients.The results provide valuable information for basic design and applications associated with extractive distillation.

Liquid-Liquid-Liquid Three Phase Extraction Apparatus:Operation Strategy and Influences on Mass Transfer Efficiency

Abstract A new mixer-settler-mixer three chamber integrated extractor is proposed in this work for liquid-liquid- liquid three phase countercurrent and continuous extraction. Experiments revealed the influences of the structural design of the three-liquid-phase extractor and some key operational parameters on three-phase partition of two phenolic isomers, p-nitrophenol （p-NP） and o-nitrophenol （o-NP）. The model three-liquid-phase extraction system used here is nonane （organic top-plaase）-polyethylene glycol （PEG 20UU） （polymer mlddle-phase）-（NH4）2SO4 aqueous solution （aqueous bottom-phase）. It is indicated that agitating speed and retention time in three-phase mixer are key parameters to extraction fraction of nitrophenol. Dispersion band behavior is related to agitating intensity, and its occurrence does not affect the extraction fraction of target compounds. The present work highlights the possibility of a feasible approach of scaling up of the proposed three-phase extraction apparatus for future in- dustrial-aimed applications.

Use of axial dispersion model for determination of Sherwood number and mass transfer coefficients in a perforated rotating disc contactor

The mass transfer process in a perforated rotating disk contactor(PRDC) using a toluene-acetone-water system was investigated.The volumetric overall mass transfer coefficients are calculated in a PRDC column.Both mass transfer directions are considered in experiments.The influences of operating variables containing agitation rate,dispersed and continuous phase flow rates and mass transfer in the extraction column are studied.According to obtained results,mass transfer is significantly dependent on agitation rate,while the dispersed and continuous phase flow rates have a minor effect on mass transfer in the extraction column.Furthermore,a novel empirical correlation is developed for prediction of overall continuous phase Sherwood number based on dispersed phase holdup,Reynolds number and mass transfer direction.There has been great agreement between experimental data and predicted values using a proposed correlation for all operating conditions.

Removal of Phenol from Dilute Solutions by Predispersed Solvent Extraction

Predispersed solvent extraction (PDSE) is a new method for separating solutes from aqueous solution by solvent extraction and one which has shown promise for extraction from extremely dilute solution very efficient and very quick. The use of colloidal liquid aphrons in predispersed solvent extraction may ameliorate the problems such as emulsion formation, reduction of interfacial mass transfer and low interfacial mass transfer areas in solvent extraction process. In present paper, colloidal liquid aphrons are successfully generated using kerosene as a solvent, tributyl phosphate(TBP) as an extractant, sodium dodecyl benzene sulphate(SDBS) as surfactant in aqueous phase and Tween-80 in oil phase. Extraction of phenol from dilute solution was studied by using colloidal liquid aphrons and colloidal gas aphrons in a semi-batch extraction column. It has been found that the PDSE process is more suitable for extraction of dilute solutions. It has also been discovered that the PDSE process has a great advantage over traditional single-stage extraction process.

Prediction of dispersed phase holdup in pulsed disc and doughnut solvent extraction columns under different mass transfer conditions

Using experimental data from a number of pulsed disc and doughnut solvent extraction columns, a unified correla- tion for the prediction of dispersed phase holdup that considers the effects of mass transfer is presented. Pulsed disc and doughnut solvent extraction columns （PDDC） have been used for a range of important applications such as ura- nium extraction and nuclear fuel recycling. Although the dispersed phase holdup in a PDDC has been presented by some researchers, there is still the need to develop a robust correlation that can predict the experimental dispersed phase holdup over a range of operating conditions including the effects of mass transfer direction. In this study, dis- persed phase holdup data from different literature sources for a PDDC were used to refit constants for the correlation presented by Kumar and Hartland lind. Eng. Chem. Res.,27 （1988）,131-138] which did not consider the effect of col- umn geometry. In order to incorporate the characteristic length of the PDDC （i.e. the plate spacing）, the unified cor- relation for holdup proposed by Kumar and Hartland based on data from eight different types of columns [Ind. Eng. Chem. Res.,34 （1995） 3925-3940] was refitted to the PDDC data. New constants have been presented for each hold- up correlation for a PDDC based on regression analysis using published holdup data from PDDCs that cover a range of onerating conditions and nhwical nronerties and consider the direction of mass transfer.