基于多场协同理论的渗透蒸发传质模型

Toprovide a theoretical basis for optimizing the pervaporation procedure, a mass transfer model for pervaporation for binary mixtures was developed basedon the multi-fields synergy theory. This model used the mechanism of sorption-diffusion-desorption and introduced a diffusion coefficient, which was dependent on the feed concentration and temperature. Regarding the strong coupling effect in the mass transfer, the concentration distribution in membrane was predicted using the Flory-Huggins thermodynamic theory. The batch experiments and other experiments with constant composition-were conducted-using a modified chitosan pervaporatioffmembrane to separate tert-butyl alcohol （TBA）-water mixtures. The parameters of the mass transfer model were obtained from the flux of the experiments with a constant composition and the activity coefficients available through phase equilibrium equation, using the Willson equation in the feed side and the Flory-Huggins thermodynamic theory within the membrane The simulation results of the experiments .are in good agreement with the results, of the experiments.     

Experimental and Numerical Investigations of Single Drop Mass Transfer in Solvent Extraction Systems with Resistance in Both Phases

Numerical simulation of transient mass transfer to a single drop controlled by the internal resistance or by the resistance in both phases was mathematically formulated and simulated in a boundary-fitted orthogonal coordinate system. The simulated results on the transient mass transfer dominated by the internal resistance are in good agreement with the Newman and Kronig-Brink models for drops with low Reynolds number. When the drop Reynolds number is up to 200, the mass transfer coefficient from numerical simulation is very low as compared with the Handlos-Baron model. The cases with mass transfer resistance residing in both the continuous and drop phases were simulated successfully and compared with the experimental data in three extraction systems recommended by European Confederation of Chemical Engineering (EFCE). For single drops with Re < 200, the numerically predicted values of the extraction fraction and overall mass transfer coefficient are in reasonable coincidence with the experimental data. I     

硅橡胶复合膜用于渗透蒸发的膜传质动力学(Ⅱ)膜内的扩散传质

The pervaporation of organics from dilute aqueous solution through a novel plate composite silicone rubber membrane was investigated. The measured and derived data indicated that the composite membrane possessed very high permeation flux and stable selectivity for dilute organic aqueous solution. Based upon the well- known resistance-in- series model, diffusive mass transfer behavior in membrane was investigated by calculation from the measured data with different skin layer thickness of membranes. The experimental results showed that the diffusive mass transfer coefficient conformed to Arrhenius correlation with temperature and was independent of the flow status. The diffusivities of the given alcohols in membrane had an order of magnitude 10 m-10·s-1 at a wider range of temperature, which is similar to those reported in literatures.     

第三分散相液滴增强气体吸收的一维非稳态非均相传质模型

A model for one-dimensional unsteady heterogeneous mass transfer was developed based on Danckwerts’ surface renewal theory in order to describe the mass transfer enhancement of absorption process for a slightly soluble gas in a gas-liquid-liquid system. The model accounts for the mass transfer resistance within the dispersed phase and the effect of emulsion viscosity on mass transfer. An analytical solution for enhancement factor was obtained by Laplace domain transformation. The absorption rates of carbon dioxide in the dodecane-in-water and castor oil-in-water systems were measured in a thermostatic reactor, and the enhancement factors were calculated at different volume fractions of dispersed phase and stirrer speeds. The model predictions agree well with the experi-mental data.     

利用固定化L-天冬酰氨酶进行血液净化治疗白血病的数学模型研究

Plasma was purified in an immobilized L-asparaginase column. The predicted results are in good agreement with experimental data. It is indicated that the mathematical model is suitable for the mass transfer and reaction of blood purification.     

MASS TRANSFER IN MEMBRANE ABSORPTIONDESORPTION OF AMMONIA FROM AMMONIA WATER

Hydrophobic membrane can provide fast mass transfer for absorption-desorption of gasesform liquid to absorbent.The removal of ammonia from ammonia water and absorption with dilutesulphuric acid was studied in a pilot plant with polypropylene hollow fiber column,The removalrate and influences of operation temperature,flow rate and concentration on mass transferperformances were discussed mathematically.Experimental results and computer calculation show thatthe ammonia removal rate is not affected by the feed concentration for a given system.Both partialand overall mass transfer coefficients vary along the axis of the fiber,and the mass transfer for themembrane process is controlled by membrane resistance.     

萃取体系滴内和两相阻力控制的单液滴传质实验和数值模拟研究

Numerical simulation of transient mass transfer to a single drop controlled by the internal resistance or by the resistance in both phases was mathematically formulated and simulated in a boundary-fitted orthogonal coordinate system. The simulated results on the transient mass transfer dominated by the internal resistance are in good agreement with the Newman and Kronig-Brink models for drops with low Reynolds number. When the drop Reynolds number is up to 200, the mass transfer coefficient from numerical simulation is very low as compared with the Handlos-Baron model. The cases with mass transfer resistance residing in both the continuous and drop phases were simulated successfully and compared with the experimental data in three extraction systems recommended by European Confederation of Chemical Engineering (EFCE). For single drops with Re ＜ 200, the numerically predicted values of the extraction fraction and overall mass transfer coefficient are in reasonable coincidence with the experimental data. It is concluded that the numerical simulation can be resorted in some cases of solvent extraction for conducting numerical experiments and parametric study. Nevertheless, for better resolution as higher Reynolds number drops are simulated, more sophisticated techniques should be developed and incorporated to deal with the large deformation and transient shape oscillation as well as possible Marangoni effect.     

PTFE多孔膜气体渗透数学模型和膜孔结构的影响

Membrane-based separation processes are new technology combined membrane separation with conventional separation. Hydrophobic porous membranes are often used in these processes. The structure of hydrophobic porous membrane has significant effect on mass transfer process. The permeabilities of five kinds of gas, He, N2,O2, CO2 and water vapor, across six polytetrafluoroethylene(PTFE) fiat membranes were tested experimentally.Results indicated that the greater the membrane mean pore size and the wider the pore size distribution are, the higher the gas permeability. A gas permeation model, including the effects of membrane structure parameter and gas properties, was established. A comprehensive characteristic parameter (including porosity, thickness and tortuosity) was found more effective to express the influence of membrane structure in gas permeation process. The predicted permeation coefficients were in good agreement with experimental data.     

Electrochemical analysis and convection-enhanced mass transfer synergistic effect of MnOx/Ti membrane electrode for alcohol oxidation

The different electrocatalytic reactors could be constructed for the electrocatalytic oxidation of 2,2,3,3-tetrafluoro-1-propanol(TFP) with two typical MnO_x/Ti electrodes, i.e.the electrocatalytic membrane reactor(ECMR) with the Ti membrane electrode and the electrocatalytic reactor(ECR) with the traditional Ti plate electrode.For the electro-oxidation of TFP, the conversion with membrane electrode(70.1%) in the ECMR was 3.3 and 1.7 times higher than that of the membrane electrode without permeate flow(40.8%) in the ECMR and the plate electrode(21.5%) in the ECR, respectively.Obviously, the pore structure of membrane and convection-enhanced mass transfer in the ECMR dramatically improved the catalytic activity towards the electro-oxidation of TFP.The specific surface area of porous electrode was 2.22 m~2·g~(-1).The surface area of plate electrode was 2.26 cm~2(1.13 cm~2× 2).In addition, the electrochemical results showed that the mass diffusion coefficient of the MnO_x/Ti membrane electrode(1.80 × 10~(-6) cm~2·s~(-1)) could be increased to 6.87 × 10~(-6) cm~2·s~(-1) at the certain flow rate with pump, confirming the lower resistance of mass transfer due to the convection-enhanced mass transfer during the operation of the ECMR.Hence, the porous structure and convection-enhanced mass transfer would improve the electrochemical property of the membrane electrode and the catalytic performance of the ECMR,which could give guideline for the design and application of the porous electrode and electrochemical reactor.     

正十二烷-水乳液吸收丙烷的传质增强作用(英文)

A one-dimensional unsteady heterogeneous parallel mass transfer (ODUHPMT) model was developed for the absorption enhancement of volatile organic compounds (VOC) by the dispersed droplets. An analytical solution for enhancement factor was obtained based on surface renewal theory and the Laplace domain transformation. The absorption rate of propane into water at dif-ferent stirring speeds with the added micro dodecane droplets was investigated experimentally in a thermostatic stirred tank. The mass transfer flux across the gas-liquid interface and the enhancement factor were measured. The results showed that the dodecane has an obvious enhancement effect on propane absorption into water, the maximum enhancement factor reached 11. The enhance-ment factor increased with increasing dodecane volume fraction and decreased with increasing stirring speed. The experiment data agreed well with the model predictions and showed high prediction accuracy of ODUHPMT model.     

有氧补偿乳状液中多不饱和脂肪酸氧化模型

研究了恒表面氧压搅拌式有氧补偿条件下乳状液中多不饱和脂肪酸(PUFA)的氧化。通过综合考虑气液边界传质阻力、油水边界乳化剂形成的液膜边界层阻力、PUFA自催化氧化反应动力学,建立了相应的扩散-氧化数学模型。实验验证该模型能较好地拟合搅拌式有氧补偿条件下乳状液中氧的扩散和亚油酸的氧化过程,并在乳化剂浓度变化对乳状液中PUFA氧化的影响方面表现出很好的适用性。研究对揭示乳状液中PUFA的氧化机制最终有效控制PUFA的氧化具有重要的理论研究价值。     

无外界氧补偿条件下乳状液中多不饱和脂肪酸氧化模型

建立了在无外界氧补偿条件下乳状液中多不饱和脂肪酸(PUFA)氧化的数学模型。该模型综合考虑了乳化剂形成的液膜边界层阻力、PUFA自催化氧化反应以及油水相比表面积等因素的影响。实验验证了该模型能较好地拟合无外界氧补偿条件下乳状液中氧的扩散和亚油酸的氧化过程,并模拟计算了乳化剂膜传质系数和油水相比表面积等因素对扩散-氧化的影响程度。结果表明,乳化剂膜传质系数和油水相比表面积是影响乳状液中PUFA的氧化的主要因素。     

亚油酸乳状液体系氧化模型与求解

研究了恒表面氧压静置式无限氧补偿条件下乳状液中亚油酸的氧化,通过综合考虑气液边界传质阻力、水相扩散、油水边界乳化剂膜边界层阻力、多不饱和脂肪酸(PUFA)自催化氧化反应动力学,建立了扩散-氧化数学模型。采用非对称正交配置法处理特殊边界,求解偏微分方程组,计算了氧化过程中乳状液中氧和亚油酸在垂直于液膜方向的浓度分布,计算方法快捷、有效;结合数学模拟试验和实验值,确定了气液界面氧的液膜传质系数和水相中氧的扩散系数。实验验证该模型能较好地拟合静置式无限氧补偿条件下乳状液中氧的扩散和亚油酸的氧化过程。     

乳状液膜扩散－反应双控制过程传递机理数学模型研究

本文建立了乳状液膜扩散－反应双控制过程传递机理的数学模型,该模型综合考虑了膜外相边界层,金属离子与载体的界面化学反应以及膜相阻力等因素对传质的影响。实验验证了该模型具有较好的适应性,并模拟计算了各因素对传质的影响程度     

AM/AMPS/SSS三元反相乳液聚合体系稳定性研究

以丙烯酰胺(AM)为主单体、2-甲基-2-丙烯酰胺基丙磺酸(AMPS)、对苯乙烯磺酸钠(SSS)为抗温抗盐单体,以白油为连续相,Span 80/Tween 80为复合乳化剂,制得了AM/AMPS/SSS三元反相乳液聚合体系,考察了HLB值、乳化剂浓度、油水比、pH值、搅拌时间、搅拌速度对乳液稳定性的影响。结果表明,乳化剂含量为6%～7%(体系总量),HLB值为5.89,体系pH=8,油水体积比为1.8∶1,搅拌时间30～40 min,搅拌速度为500 r/min时得到稳定的反相乳液体系,适合进行三元反相乳液聚合。     

响应面分析法优化乳化石蜡制备工艺

采用响应面分析法(RSM)中CCD数学模型优化工艺参数,考察乳化剂用量、乳化时间、乳化温度、搅拌速度各因素之间相互作用对石蜡乳液稳定性的影响。得到乳化石蜡制备的最佳工艺条件:Tween80质量为复合乳化剂质量的32.7%,乳化剂用量为总乳液质量的7.056%,乳化时间为46 min,搅拌速率为1 240 r/min,在此条件下,实验制备得到平均粒径为0.286μm,分散性为0.224的石蜡乳液。结果表明:该模型综合分数预测值为0.656,与实验验证值0.638的相关系数为0.973 2,可用于实际预测。     

秸秆基环氧树脂乳液的制备及其涂膜性能

以脂肪醇聚氧乙烯醚(AEO-9)和十二烷基硫酸钠(SDS)复配为乳化剂,通过相反转技术乳化秸秆基环氧树脂,考察了复配乳化剂的HLB值、用量以及乳化温度和搅拌速率对乳液临界含水量Rf值、粒径及稳定性的影响,获得了如下较佳的乳化工艺条件:HLB值17,复合乳化剂用量8%,乳化温度35°C,搅拌速率800 r/min。以此工艺制得的乳液稳定性较好,平均粒径为1.57μm。以水性聚酰胺为固化剂,将此乳液制成清漆,固化后所得漆膜综合性能良好。     

聚合釜釜型对偏氟乙烯乳液聚合的影响

偏氟乙烯(VDF)乳液聚合工艺的聚合效果关键是取决于VDF单体与水介质中助剂之间的传质效率。为研究较佳的聚合工艺参数,分别采用立式和卧式聚合釜,投入种类和规格相同的原料,在相同的温度和压力等操作条件下,研究较佳的VDF乳液聚合工艺参数。实验结果显示:釜型及搅拌桨形式在很大程度上影响了传质效率,采用卧式聚合釜能以较少的引发剂和乳化剂,得到较快的反应速率、较高的含固质量分数,且乳液稳定性更佳。因此可以认为卧式聚合釜是VDF乳液聚合较佳的聚合设备。     

高稳定性硅油乳液的制备研究

以2 000 mPa.s的二甲基硅油为主要原料,研究了乳化剂配方的选择、硅油乳液制备的条件,考察了乳化剂用量、乳化时间、乳化温度和搅拌速度等因素。结果表明,最佳乳化条件为:乳化剂用量为7%,乳化温度70℃,乳化时间30 min,搅拌速度800 r/min,乳化水分2次加入,乳化时间分别为10 min和20 min。制备的固含量约为40%的硅油乳液,稳定性和分散性好。