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The present study is conducted to propose a new code for optimizing a multicomponent isotope separation cascade. An efficient code is developed using an enhanced TLBO algorithm with a novel mutation for calculating the optimal parameters. The results indicate that by implementing a new objective function derived from the combination of D function with total interstage flow rates, the optimum tapered cascade is more efficient than the optimal square one. Also, the best feed locations for the separation of the middle components in the square cascade are the middle stages. [ABSTRACT FROM AUTHOR]

The Q-cascade is a type of model cascade that is particularly useful for studying multicomponent isotope separation. The cascade segmentation technique is further developed to optimize Q-cascades, which minimizes the relative total flow by splitting a cascade into smaller segments that each use the mass number of the virtual component as a decision variable. Application of this technique to Cadmium isotope separation shows that it is always effective. If the number of segments into which a cascade is split increases, then the minimum relative total flow decreases. A progressive segmentation strategy is developed to maximize the number of segments. [ABSTRACT FROM PUBLISHER]

The physical meaning of a continuous profile cascade, which is frequently used in the study of multicomponent isotope separation and named as the Q-cascade is explained. It is found that the parameter Q for a component at a stage is nothing but the relative increase of the concentration of the component, and is constant at all cascade stages. The Q-cascade is classified as the quasi-ideal cascade playing an importantrole for fast evaluation of the separation cascade parameters for multi-isotope mixture separation. [ABSTRACT FROM AUTHOR]

Analysis of economical aspects of centrifuge-based separation shows that the bulk of the cost is proportional to the number of centrifuges in a cascade. In this paper a program which is called MAKNO is used to obtain the velocity field in a centrifuge by solving popular purely axial flow in a gas centrifuge. Through using MAKNO and solving concentration equation in a single gas centrifuge a realistic function for α, separation factor, in relation to θ, cut, and f, feed flow rate is achieved. To minimize the number of centrifuges in a cascade one needs to determine optimal parameters, α, θ, and f. Finding the optimum solution requires a huge amount of calculation in classical methods. Recently, a genetic algorithm (GA) technique has attracted considerable attention among various modern heuristic optimization techniques. To optimize the parameters and the number of centrifuges for a given cascade a Real Coded Genetic Algorithm program, RCGA, is implemented and developed. It has been shown that the application of RCGA to this problem not only reduces the amount of calculation but also guarantees finding the best solution. It is found that, from an evolutionary point of view, the performance of the GA is excellent. [ABSTRACT FROM PUBLISHER]

Pulse cascades are non-conventional and may suit the flexible demand for stable isotopes varying in varieties and quantities. The separation power in pulse cascades is evaluated, and the definitions and the expressions of the separation efficiency are given respectively. They are both analyzed and studied, and are found having close relations with the pipe holdup and the pulse period. It is better to adopt an appropriate pulse period and a proper pipe holdup for a pulse cascade to obtain a large degree of separation and high separation powers and separation efficiencies in a short transient time. [ABSTRACT FROM AUTHOR]

The possibility of estimating the minimum total flow in a cascade with concentrations of a target component given in the product and waste flows by means of a model match abundance ratio cascade (MARC) is studied. The parameters required to describe MARC characteristics are the total number of separation stages, the feed flow location, and the M* parameter, which is equal to a half-sum of mass numbers of the target and the supporting components. Specific research carried out independently in two scientific labs in China and Russia has demonstrated that the integral parameters of the MARC, optimized by the M* parameter, are very close to that of the optimum by the minimum total flow cascade found by means of numerical optimization. The calculation is performed for separation of krypton isotopes when the end component 78Kr and the intermediate component 83Kr are considered to be the targets. It paves the way to use the optimized MARC parameters for two purposes: first, for fast and easy evaluation of the real cascade parameters and second, as an initial guess in its further direct numerical optimization, thereby allowing significant savings in computation time. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Suggestions are made for the practical implementation of membrane cascades using diafiltration for the fractionation of solute pairs. Experiments are described that demonstrate the desirability of replacing solvent during the course of each diafiltration, and a parallel modeling development suggests an attractive means for accomplishing this replacement. A batch process is described to achieve such separations by simple assemblies of existing equipment, and suggestions are made for designing continuous processors. Such cascades are attractive for a wide variety of solutes including native proteins, as well as commodity chemicals, and they can be applied to the resolution of enantiomers through simple modifications already described in the public literature. The same techniques can be applied to multicomponent systems using the concept of key components as has long been done in distillation. The low inherent capital costs and high throughput rates of such membrane cascades strongly suggest that they should compete successfully against a significant number of presently used chromatographic processes, and their simplicity should make then formidable competitors to simulated moving beds as well. [ABSTRACT FROM AUTHOR]

A nonconventional gas centrifuge cascade, called the NFSW(no feed and single withdrawal) cascade, is studied in the separation of middle components by means of numerical simulation. The cascade has no feed and only a single withdrawal at either end of the cascade, different from conventional cascades, which usually have two withdrawals at the two ends of the cascade and one feed in between. The material to be separated is loaded in a reservoir at either end, and the desired component is enriched in either the reservoir or the withdrawal at the other end. The effects of the unit separation factor(equivalently, the cascade length) and the ratio of the upstreaming flow rate to the withdrawal rate are investigated on separation. The separation performance is evaluated in terms of the material recovery and the operation time efficiency, and is compared with those of the corresponding conventional cascades and another type of nonconventional cascade, the SW(single withdrawal) cascade. It is found that the NFSW cascade is superior to the conventional cascade and comparable in the material recovery with, but advantageous in the operation time efficiency over the SW cascade. [ABSTRACT FROM AUTHOR]

The conceptual design for N-stage cascades based on the differential condensation (DC), and differential vaporization (DV) processes is presented. Four and six stage “no-mix” and constant recycle DCDV cascades have been modeled to separate an arbitrary binary feed. The study suggests that cascades based on the differential processes could be significantly more efficient than cascades based on equilibrium stages (ordinary distillation). In no-mix DCDV cascades, all stage separation factors are equal and significantly greater than the equilibrium stage separation factors (i.e., relative volatility). In constant recycle DCDV cascades, the DV reboiler and DC (partial) condenser stages have stage separation factors much higher than the relative volatility and are significantly greater than the separation factors for the interior DCDV stages, although the stage separation factors for the interior stages are still higher than the relative volatility. Constant recycle hybrid cascades containing DV reboilers and DC condensers coupled with equilibrium interior stages are more efficient than constant recycle ordinary distillation cascades containing the same number of stages, especially for systems with higher relative volatility that require fewer stages. For systems with lower relative volatility (greater number of stages) the difference in performance between the hybrid and ordinary distillation cascades is less pronounced. [ABSTRACT FROM AUTHOR]

Distillation cascades based on differential condensation (DC) and differential vaporization (DV) stages are considered as an alternative to ordinary (equilibrium stage) distillation for the separation of binary mixtures. In the differential condensation--differential vaporization (DCDV) cascades, stage separation factors can be much higher than for cascades based on equilibriumstages, and as a result, significantly fewer stages and, possibly, lower recycle ratios may be required compared with conventional distillation. This paper presents the theory behind the DV and DC stages and explores the use of the two-stage cascade design (a DV reboiler and DC condenser), to recover oxygen for use in hypersonic flight. Part II will consider N-stage cascades that could possibly be used to separate most systems now separated by ordinary distillation. [ABSTRACT FROM AUTHOR]

This article reviews and analyzes the state-of-the art on separation of multicomponent isotope mixtures in cascades. Different methods, which are applied to calculate the cascade configurations and designs as well as those used to describe some transient processes in cascades when separating multicomponent isotope mixtures are discussed and analyzed in detail. The main directions for the further development of isotopes fractionation using cascades are formulated. [ABSTRACT FROM AUTHOR]