离散流量离心分离级联的数值优化

在连续流量离心分离级联的数值优化上已有不少研究,从理论上提供了最优化的级联模型.但实际中级联各级的离心机台数必为整数,即各级流量为离散值,因此为了获取更好的分离效益,研究离散流量级联的数值优化,使其尽可能接近连续流量级联是十分必要的.论文比较了不同的优化方式,找到了简便高效地完成此种情况下数值优化的方式和策略.结果表明,离散流量和连续流量两种情况下最优级联的形状参数是完全一致的;具体的水力学参数并不相同,但相差不大.最后审视并改进了处理整实型变量混合优化的策略,减少了优化工作量,提高了优化效率.     

A Calculation Procedure for Designing Ideal Centrifugal Separation Cascades

Abstract

A numerical method is presented for determining flow rates in centrifugal isotope separation cascades that satisfy the required “ideal cascade” conditions. This method is an iterative method, which in the iteration process uses the q-iteration method to give the concentration and distributions of components under a specified hydraulic status for a cascade; and then, based on the concentration distributions, solves the algebraic equations describing the hydraulic status of the cascade to improve the specified hydraulic status towards the required “ideal cascade” conditions. The material losses in the cascade pipes and centrifuges are taken into account. Numerical simulations are performed by taking an MARC cascade with variant stage separation factors as an example. The results from four cases with and without material losses are compared. The results demonstrate that the method works very well, and show that when the material losses are nonexistent or very small, the concentration distributions can exactly satisfy the “ideal cascade” condition; but when the material losses are large, the “ideal cascade” condition can not be satisfied, but the method can produce a solution that allows the condition to be approximately satisfied.     

Ideal and Optimum Cascades

Abstract

In gaseous diffusion and gas centrifuge uranium enrichment plants, separating units are connected in cascades. The stage separation factor in gaseous diffusion is close to unity, while in a gas centrifuge it is much larger. Ideal cascades for separating binary mixtures have been designed with no mixing of the species. A new concept, particularly applicable to cascades with large stage separation factors, is called the “optimum” cascade. These cascades allow mixing, but the value of the total flow as found in some cases is less than in corresponding ideal cascades. In this paper, ideal and optimum cascades are discussed and compared.     

A Generalized Computer Model of the Transient Behavior of Multicomponent Isotope Separation Cascades

Abstract

The time dependent performance of large separation systems is a major consideration in the enrichment of the isotopes of elements that have a direct role in nuclear fuel cycles. The transient behavior of multicomponent separation cascades is described by a set of nonlinear partial differential equations that are similar in form for chemical exchange, distillation, gaseous diffusion, thermal diffusion, and other countercurrent processes. The Mound computer model is set up to solve the differential equations by a fast, implicit forward difference technique. Systems of up to 10 components can be handled with a wide variety of multiple input and output streams. With modifications, the program can be used to model systems of two or more cascades. It has been applied to the separation of the isotopes of uranium, the noble gases, carbon, oxygen, nitrogen, chlorine, sulfur and calcium. A neon isotope separation problem is given as an example of the precision with which performance can be predicted for multicomponent systems.     

Influence of Holdups and Feed on the Transient Process of Pulse Cascades

In isotope separation pulse cascades are non-conventional and transient processes take place at each stage and in the whole cascade. A numerical method is developed to study the transient process of reaching steady state and applied to square pulse cascades to identify the majors of influence. Without feed and withdrawals, the main factors influencing the transient process are the cascade length and the ratio of the centrifuge holdup to the pipe holdup. With feed and withdrawals, the factors influencing the transient process include the feed, the centrifuge holdup, the pipe holdup, and the cascade length.     

热扩散法分离氖同位素级联设计及应用

通过计算设计了热扩散法分离氖(Ne)同位素的工艺参数,并进行了单柱试验;在此基础上设计了Ne同位素分离的热扩散级联装置,应用于^22Ne同位素的分离,得到了^22Ne同位素浓缩的动力学曲线及装置的浓缩曲线、产率曲线。试验结果表明该工艺和技术具有较高的分离Ne同位素的效率。     

A Study of Multicomponent Streams in Off-Design Centrifuge Cascades

International Atomic Energy Agency inspectors employ several safeguards measures to ensure only declared operations are occurring at a gas centrifuge plant. One safeguards tool, environmental sampling, can help quantify the materials present in a cascade and gas centrifuge plant. The sampling results can be compared with expected values to determine if the concentrations found are reasonable. In this paper, a methodology is presented for determining the operating envelope of isotope enrichment and material throughput that can be achieved in a reduced throughput cascade. The effects of feed material and centrifuge performance and optimization are studied.     

Analysis of Gas Centrifuge Cascade for Separation of Multicomponent Isotopes and Optimal Feed Position

Abstract

Analysis of the concentration distribution in a gas centrifuge cascade for separation of multicomponent isotope mixtures is different from that in a cascade for separation of two-component mixtures. This paper presents the governing equations for a multicomponent isotope separation cascade. Numerically predicted separation factors for the gas centrifuge cascade agree well with the experimental data. A theoretical optimal feed position is derived for a short square cascade for a two-component mixture in a close-separation case. The optimal feed position for a gas centrifuge cascade for separation of multicomponent mixture is discussed.     

Isotope Separation of Nitrogen by Ion Exchange Chromatography in a Cascade System

The ion exchange chromatography technique in a cascade process was used to separate stable isotopes of nitrogen (¹⁴N/¹⁵N). For this purpose, three column systems (with different internal diameters, S1?14.5 cm; S2–9.5 cm; S3–5.2 cm) were used that contained the cationic resins DOWEX 50 WX8 (as H⁺ and equilibrated with H₂O) and measured 1.7 m in height. Isotopic fractionation of nitrogen occurs during displacement band chromatography (DBC) of the NH₃ (aq) solution with a 0.75 mol L^?1 NaOH solution. The active sites of the resin were previously saturated to form NH₄ ⁺ (RNH₄) with a 0.75 mol L^?1 solution of (NH₄)₂SO₄ at a natural isotopic abundance (0.366 at. %) in ¹⁵N. The NH₄ ⁺/NH₃ (aq) equilibrium was determined during the DBC, which enriched the rear portion of the band with ¹⁵N. In S1, enrichment of approximately 5 at. % of ¹⁵N in the last 10 cm was achieved. After four interactions (couplings) between S1–S2, an enrichment of approximately 50 at. % of ¹⁵N was obtained. During the interaction between S2–S3, after the second coupling, an isotopic enrichment of approximately 90 at. % of ¹⁵N was observed, which produced 70 g month^?1 of (¹⁵NH₄)₂SO₄.     

多组元溶液分相条件的探讨

本文通过改型的UNIQUAC方程 ,利用NEWTON RAPHSON法计算了二元、三元及四元液液平衡数据。从中发现 ,当具有部分互溶性质组分的活度系数发生突变时 ,则该体系就会出现分层现象。为此 ,本文认为具有部分互溶组分活度系数的突变可做为多组元溶液分相的判据。     

关于同位素硼-10的分离和生产

叙述了同位素硼 １０的分离技术,唯有三氟化硼—苯甲醚化学交换精馏法是当今世界美、俄等国工业生产规模所采用的技术路线。     

Systematic Modeling of the (13C) Isotope Cryogenic Distillation Process

Isotopic enrichment by low-temperature distillation of carbon monoxide is difficult to handle, the experiments providing with the necessary data are time-consuming and difficult to perform, so the mathematical modeling of the process is an appropriate approach to study and to further control the column. This paper develops a mathematical model for the (¹³C) isotope cryogenic distillation process using two subsystems of the plant: the hydrodynamic part and the isotope-separation part. The model is validated using experimental data from the pilot column from the National Institute for Research and Development of Isotopic and Molecular Technologies Cluj-Napoca. The proposed model is suitable for various cryogenic distillation columns, using the proper parameters.     

Solution Method for Countercurrent Plug Flow Models of Multicomponent Gas Separation by Permeation

Abstract

A simple solution method was developed for the countercurrent ideal plug flow model of multicomponent gas separation by permeation that is commonly applied to hollow fiber membrane modules. The solution method is independent of the number of components in the feed gas. The result is an implicit function in a single variable defined as the stage cut. The function is readily solved by the method of damped successive substitution. The method was tested for three cases from the literature and found to be insensitive to the initial guess for stage cuts less than 60%.     

Diffusion Transport Vector for Multicomponent Gas Separation in Ultracentrifuge

Abstract

Simplified diffusion transport vector expressions for multicomponent gas mixture mass transfer analysis have been derived. Approximate relations for the general diffusion coefficients for multicomponent gas separation in an ultracentrifuge for both isotope and nonisotope mixtures are developed. Taking into account that diffusion coefficients matrices are diagonally dominant, a simple relationship for diffusion transport vectors for the case of isotope separation is derived. It is shown that the relative inaccuracies in separative power and separation factors calculation are less than 1-2%. Analogous relationships for diffusion coefficients for the separation of a nonisotope mixture containing small admixtures in the main gas are suggested. These relationships can be used when the total mole fraction of the admixtures is less than 5%.     

合成氨装置中蒸汽发生器及其控制系统优化设计

针对合成氨关键设备蒸汽发生器多次发生换热管泄漏及设备顶部汽包气液夹带等情况,对该设备及其控制系统进行优化设计改造,改造后设备运行稳定。     

泡沫分离技术在蛋白质多元体系分离中的应用

综述了泡沫分离蛋白质与糖,蛋白质与表面活性剂以及不同蛋白质的混合体系的研究进展,分析了泡沫分离技术在蛋白质分离中应用的前景并提出了需要解决的问题。     

Comparison study of schemes for separation of intermediate isotope components

ABSTRACT

This paper uses the Q-cascade model to investigate the separation performance of eight schemes, comprising variations of two single-cascades and two double-cascades, to separate an intermediate isotope component. Optimization determines the relationship between the minimum relative total flow and concentration for different concentration requirements of the intermediate component. The results show that single-cascade schemes are not efficient. Rather, the optimal scheme is a double-cascade scheme that uses a three-stream cascade and a cascade with two feeds and an intermediate withdrawal. The successful optimization of all schemes indicates that this approach can be generalized to optimize various multistep separation processes.     

粒状塑料原料中粉尘分离机理及柔性流动分离模型

塑料原料中的粉尘含量直接影响其下游制品如薄膜、注塑件等的质量,控制或减少塑料原料中的粉尘含量十分重要。对塑料粒子中粉尘的分离机理进行了探讨,构建了柔性流动分离模型,它为精确控制和测定粉尘含量提供了量化依据,提出了提高粉尘分离效率的措施。     

稳定同位素的分离与应用

介绍了国内外稳定同位素的发展以及Ｄ，＾１３Ｃ，＾１５Ｎ，＾１８Ｏ等稳定同位素的分离，并对标记化合物的生产和应用作了概述。     

Ne同位素分离中微量杂质的气相色谱法

用气相色谱法测定热扩散法生产的Ne同位素气体的化学纯度。Ne同位素产品中的杂质主要为O2和N2(≤0.1%)及极微量的CO2、CH4、Ar、He、H2。Ne同位素产品分析过程借助控制待测气体中关键组分O2、N2的方法可以间接表征Ne同位素气体的化学纯度。实验采用H2气为载气、分子筛为固定相、柱温40.5°C,O2、N2检测灵敏度分别为0.0113%/mm、0.0331%/mm。进样方式为活动定体积进样,样品量≤2mL,平均偏差分别为0.01%、0.03%。