Solution of the Diffusion Equations in a Gas Centrifuge for Separation of Multi component Mixtures

Abstract

The demand for stable isotopes in physical and chemical research and in medical diagnostics is growing, and the gas centrifuge process is able to provide large quantities of stable isotopes. A set of diffusion equations describing separation in a gas centrifuge for a multi component mixture is established. These equations involve general diffusion coefficients. Using the radial averaging method and the simplified diffusion transport vector for a multi component isotopic mixture, nonlinear partial differential equations are transformed to a set of nonlinear ordinary differential equations. An iteration method for the solution is presented. The relationship between the separation factor and the mass difference, γ _ij = γ ^Mj _o ^?Mi , is shown to be in agreement with both the computational and the experimental results with very high precision.     

液膜自然扩散微型综合化学实验教学研究*--铬化合物随溶液变化过程的自然扩散规律

液膜自然扩散综合微型实验是以绿色化学为理念,在点滴皿中,使反应物的溶液滴形成易于观察的液膜,提高了透视度和分辨率。本文采用该法探究“Cr3＋继阶式综合微型实验及应用于相关离子鉴定”“ HCrO－4与Cr2 O2－7平衡移动式对比性实验”和“CrO2－4（ Cr2 O2－7）与Pb2＋、 Ba2＋、 Ag＋同心扩散式对比性实验”,提高了综合实验效果,有利于直接投影演示教学,拍摄记录实验过程中的现象信息。     

含生物毒性物质的化工污水对硝化作用的影响

针对某大型化工企业新建的污水生物脱氮处理系统,研究了含有生物毒性物质的化工污水对硝化作用的影响。研究结果表明来源于个别排放点的染料生产污水、橡胶生产污水、助剂生产污水对硝化作用有显著的影响,一些特征污染物如苯胺,硝基苯,苯酚及Zn2+,Mn2+,Ni2+均对硝化作用有明显的抑制作用,从而导致生化处理系统的硝化反应速率明显降低,而且以Ni2+最为显著。     

加盐萃取精馏分离酯水溶液的研究

将加盐精馏和萃取精馏结合起来的加盐萃取精馏新方法,由醋酸甲酯-水体系的汽液平衡试验结果表明,盐的加入破坏了共沸点组成,加盐萃取精馏比单纯的加盐精馏和萃取精馏工艺更优.     

化工专用空分装置的安全运行管理探讨

在实际建设和发展过程中,绝大多数的气化炉都使用煤为基础性的燃料,同时还使用氧气作为主要的气化剂。我国工业建设和发展的过程中,需要大力推动化工工业的发展,并在此过程中不断对其应有的油气工程产业进行完善,使得其逐渐向着煤炭方面进行发展。在这种状况下,就能够促进我国现代化化工产业的发展,并加强化工产业的转型,以促进其配套生产的空分装置在一定程度上得到转型。在逐渐发展的过程中对空分装置的研究,以及其安全运行过程中的管理措施就成为化工行业乃至整体工业领域关注的重点问题之一。     

无解析解表达式的模型方程组中待定参数的计算机估值

联合采用最优化技术与数值分析方法,可以有效地解决化学工程中的无解析解表达式的模型方程组中待定参数的估值问题。本文以一组由偏微分方程、常微分方程、代数方程等不同类型方程构成的复杂方程组为例,剖析了这一方法。分析结果表明,这一方法更能准确、迅速地获得所需要的模型参数,而且具有普遍意义。     

On the Solution of Non-Isothermal Reaction-Diffusion Model Equations in a Spherical Catalyst by the Modified Adomian Method

We investigate the reactant diffusion within a porous catalytic pellet including the heat of reaction. The Lane–Emden boundary value problem with an Arrhenius reaction rate is used to model the reactant concentration. We combine the Volterra integral form with the Adomian decomposition method to solve the equivalent Fredholm–Volterra integral equation. We then estimate the reactant concentration at the center of the catalytic pellet and the iterated Shanks transform is used to improve the accuracy of the approximations. The objective error analysis formulas are used to demonstrate a high accuracy and rapid rate of convergence, which does not depend on a priori knowledge of the exact solution or comparison with an alternate approximation method. Thus low-stage approximations by the Adomian decomposition method are validated for parametric simulations of the reactant concentration profiles and the effectiveness factor profiles. Our approach demonstrates enhancements over previous investigations, and is readily extensible to more general diffusion reaction models in catalytic reactor engineering.     

Separation of Biological Solutes by Liquid Thermal Diffusion

Abstract

A number of phenolic components of urine reactive to phosphomolybic acid were separated by the use of liquid thermal diffusion.     

丙炔醇-丁炔二醇-水溶液的渗透汽化分离研究

用PDMS复合膜从实际的丙炔醇-丁炔二醇-水溶液中渗透汽化分离丙炔醇。实验证明,膜渗透汽化可以实现丙炔醇的选择性分离,对水的分离因子可达3.78;丁炔二醇被膜完全截留;丙炔醇通量对温度具有敏感性,通量随着温度的增加上升得很快,丙炔醇通量在25℃时为45.28g/(m2.h),在60℃时为243.24g/(m2.h),显示了PDMS膜从这个体系中分离丙炔醇具有某种优势;对实验数据进行线性回归,证明丙炔醇通量和温度的关系可以用Arrhenius公式表征。为工业上用PDMS膜渗透汽化分离提纯丙炔醇提供参考。     

Effects of Inclined Angle and Plate Spacing on the Degree of Separation in Batch-Type Flat-Plate Thermal Diffusion Columns

Effects of inclined angle and plate spacing on the degree of separation in batch-type flat-plate thermal diffusion columns, with operating expense and fixed charge kept unchanged, are discussed. It was found that the degree ofseparation increases when the inclined angle increases or when the platespacing decreases. However, decreasing the plate spacing will lead to decreasingthe amount of solution to be treated in the column, while increasing the inclined angle will enlarge the operating time for reaching the steady state.     

A Model for the Diffusion of Moisture in Adhesive Joints. Part I: Equations Governing Diffusion

A methodology is proposed to relate the diffusion coefficient of small penetrant molecules in polymers to temperature, strain, and penetrant concentration. The approach used is based on well-known free volume theories. It is assumed that the transport kinetics is governed by the constant redistribution of the free volume, caused by the segmental motions of the polymeric chains. An expression for the diffusion coefficient is inferred from the temperature, strain, and penetrant concentration dependence of the free volume. The stress dependence of solubility is predicted from the Hildebrand theory. It is shown that the resulting constitutive equations exhibit many features desirable for joint durability studies. Finally, a non-Fickian driving force arising from differential swelling is included in the governing equations.     

Effects of Inclined Angle and Plate Spacing on the Degree of Separation in Batch-Type Flat-Plate Thermal Diffusion Columns

Effects of inclined angle and plate spacing on the degree of separation in batch-type flat-plate thermal diffusion columns, with operating expense and fixed charge kept unchanged, are discussed. It was found that the degree ofseparation increases when the inclined angle increases or when the platespacing decreases. However, decreasing the plate spacing will lead to decreasingthe amount of solution to be treated in the column, while increasing the inclined angle will enlarge the operating time for reaching the steady state.     

Oxygen Chemical Diffusion Coefficient of Uranium Dioxide

The diffusion of oxygen in UO_2+α was measured between 600° and 1100°C. Samples with initial O/U values 2.08 and 2.04 were reduced in hydrogen; reduction was monitored continuously by electrical conductivity measurements. The relation between total conductivity and average O/U ratio was derived, and the diffusion coefficients were obtained. The validity of the electrical conductivity vs O/U relation was checked by measuring weight loss during reduction. Diffusion-controlled kinetics were confirmed by oxygen gradient measurements. The oxygen chemical diffusion coefficient is given by D = 0.5 exp - This equation agrees with previously determined values of the oxygen chemical diffusion coefficient of UO_2+α.     

彩钼铅矿化学分选的研究

本文论述了以化工冶金技术分离富集彩钼铅矿中铅和钼的化学分选新工岂,研究了以饱和硫化钠液浸钼分铅的工艺条件及以氯化铵为试剂在氧化酸性环境下沉钼富集的工艺条件,并提出综合利用的无废工艺及铅、钼进一步深度转化高效益化工产品的方向。     

表面活性剂在化学分离中的应用

化学分离在工业中广泛应用，表面活性剂在其中发挥着重要的作用。主要阐述在泡沫浮选、萃取和膜分离3个方面的应用前景。通过对于分离机理以及影响因素的分析说明表面活性剂在分离中的作用，并探索表面活性剂在分离中的应用前景。     

Separation of Heavy Water by Vapor-Phase Thermal Diffusion Coupled with Distillation and Condensation

Abstract

A study on the enrichment of heavy water in a vapor-phase thermal-diffusion column has been conducted. With the combination of the effects of distillation, vapor-phase thermal diffusion, and partial condensation, considerable improvement in the degree of enrichment has been achieved in a vapor-phase column rather than in a liquid-phase column. It was also found that even the part of enrichment contributed only by vapor-phase thermal-diffusion effect is much higher than that obtained by liquid-phase thermal diffusion.     

多分散聚合物稀溶液体系的Rouse模型

本文将Rouse提出的均一分布球簧链式分子模型加以推广.得到了多分散体系的本构方程.对几种最常见的分子量分布,在稳态剪切流中,分别计算了它们的物质函数以及特性粘数与重均聚合度的关系.结果表明,这一线性模型的流变性质与聚合物的分子量分布有密切的关系;若通过物质函数的监测,则还能预示聚合反应的动态过程.     

蒎烯醇液相扩散系数的测量

蒎烯醇(Trans-sobrerol,Sob)由α-蒎烯环氧化物水解产生,是α-蒎烯在大气中重要的氧化产物。溶液中的化学反应受溶剂的影响,同时液相反应也会受到反应物扩散系数的影响,我们采用核磁共振技术扩散排序谱法来测量Sob在水溶液中的扩散系数(diffusion coefficient,D),得到其自扩散系数为4.6×1010 m2/s,并且发现在一定的浓度范围内D不受浓度的影响。     

含醇溶液中分子扩散系数的分子模拟

利用分子动力学(MD)模拟验证了含醇溶液的无限稀释扩散系数模型和不同浓度溶液的扩散系数模型.选用的溶质分别为甲醇、乙醇、丙醇、异丙醇、正丁醇和甘油,温度为293.15K,压力为0.1MPa.计算结果表明:Dullien和Asfour方程适用于计算甲醇和乙醇溶液的扩散系数DAB;而对于其它醇溶液的扩散系数,Leffler和Cullinan方程较适用.