Selection of the sequence of separation of ternary mixtures

Two optimization problems are considered. One of them is the problem of the sequence of separation of a ternary mixture in a two-step system for which the energy consumption in processes at given capacities is minimal, and the other is the problem of the optimal distribution of contact surfaces between the first and second steps. For thermal separation systems, the dependence of the maximum possible capacity of the system on the sequence of separation of components is analyzed.     

Synthesis of ternary distillation process structures featuring minimum utility cost using the IDEAS approach

A synthesis method for ternary distillation process structures is proposed on the basis of the infinite‐dimensional state‐space (IDEAS) approach. The proposed synthesis procedure consists of two steps. At the first step, the utility cost is minimized. The result of the first step contains many tiny flows among the modules because the number of flows is not included in the objective function. Then, at the second step, an evolutionary procedure for process simplification is executed. In this step, the weighted sum of flow rates is minimized recursively while updating the weights at each iteration. The practical process structure is finally determined from the result of the second simplification step. The developed synthesis procedure was applied to the separation problem of a ternary mixture consisting of benzene, toluene, and o‐xylene. It demonstrated that the proposed procedure provides a process whose liquid composition profile is quite similar to that of a Petlyuk column. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1285–1294, 2018     

应用遗传算法实现精馏分离序列优化综合

阐述了采用遗传算法求解具有组合爆炸特征的精馏分离序列综合问题。首先在数据结构上将精馏分离序列抽象为二叉树结构编码,然后应用图论方法建立起有效的交叉和变异算子,最后对10组分精馏分离序列综合问题实例进行求解。结果表明,遗传算法对最优解命中率达80％,平均空间搜索率仅为0．0318。因此遗传算法能够成功解算大规模精馏分离序列优化综合问题。     

基于带权有向图的非清晰复杂精馏序列的合成方法

在精馏系统中非清晰分离能够克服清晰分离所固有的返混效应,从而提高系统能效。基于数据结构理论,提出了非清晰精馏序列的合成与优化方法。对于N组元混合物的分离,合成的精馏序列由N-1个精馏塔构成,且其中的非清晰分离任务含有所允许的任意多个中间分配组分。为了合成上述分离序列,利用带权有向图建立了一种新的精馏分离序列模型,并基于“vector”动态数组,提出了一个同时拥有数组和链表优点的带权有向图的储存结构。序列合成过程定义了一系列的相关操作,且选择广度优先的策略以提高合成效率。算例证明了该方法在精馏序列合成和优化的高效性。算例结果表明该算例的最优分离序列可以有效减少设备投资和能耗。     

设计演化算法实现精馏分离序列优化综合

采用演化算法求解具有组合爆炸特征的精馏分离序列优化综合问题。由于精馏分离序列与二叉树之问具有同构性．在数据结构上精馏分离序列可以抽象为二又树,直接采用二叉树结构编码方案可以同时表达个体的基因型和表现形。借鉴生物界父本可以经过有性繁殖或无性繁殖得到子代的现象。对遗传算子进行设计。应冒图论方法建立有效的二叉树结构演化重组机制,从而形成基于双亲或单亲父本的交叉算子。实例表明：双亲遗传操作其空间搜索率较低,而单亲遗传操作其最优解命中率较高。因此。演化算法能够成功解算大规模精馏分离序列优化综合问题。     

Low temperature and pressure hydrogenation of methyl-9-(hydroxyimino)-octadecanoate and derivatives to their corresponding amino derivatives

A two step, one pot procedure, for the preparation of methyl-9-(or 12)-aminooctadecanoate and 1-hydroxy-9-(or 12)-aminooctadecane was developed. This procedure is based on the oximation followed by hydrogenation of methyl-9-oxooctadecanoate, 1-hydroxy-9-oxooctadecane and the C-12-oxo isomers. For the oximation of the keto compounds ( 1a – d ) two methods were used. In the first method NH₂OH.HCl as aminodonor and Et₃N as HCl-acceptor has been used. One of the major problems in this reaction sequence is the formation of Et₃N.HCl. Experimentally it became clear that in an one pot reaction without separation of the Et₃N.HCl, the catalytic reduction of the oximes ( 2a – d ) to their corresponding amines was inhibited. This problem could be solved by using free NH₂OH. In the second method free NH₂OH was used for the oximation. For the catalytic reduction of the oxime derivatives mild (room temperature and 40 psi), and therefore industrial interesting, hydrogenation conditions were used.     

Optimal Design and Economic Evaluation of Dividing‐Wall Columns

In an effort to reduce costs, a systematic optimization approach is proposed to address the energy consumption of dividing‐wall columns (DWCs). This iterative optimization procedure begins by minimizing the overall heat duty using an innovative objective function within a constrained design space. A sensitivity analysis is then carried out on the manipulated variables to obtain their optimal ranges. Optimal operating parameters are obtained through the evaluation of the total annualized cost (TAC). For the separation process of benzene/toluene/o‐xylene, the optimal DWC flow sheet exhibits a significant decrease in TAC when compared to conventional flow sheet optimum designs. The applied optimization method and sensitivity analysis have proven to produce results at the global optimum. This method is both practical and easily applied to other systems, even to systems with more than three components.     

Finding the thermodynamically optimal separation sequence for multicomponent mixtures and the optimum distribution of the heat- and mass-transfer surface areas

The problem of the separation sequence minimizing the energy consumption at a given process capacity for multicomponent mixtures and the problem of the optimal contact area distribution among the separation stages are considered. For thermal separation systems, whose capacity is limited, the dependence of the maximum possible capacity on the separation sequence is analyzed.     

蒸馏顺序和塔间热集成的研究

本文通过对多组元蒸馏分离成本的定量分析肯定了两步法合成热集成蒸馏流程的合理性,并且提出了一种新的两步合成方法.首先用分枝定界搜索法找出最优和接近最优的非热集成分离顺序,再在已找出的每一顺序中用0—1规划建立热集成网络,最后通过比较热集成后几个分离流程的总分离成本决定出最优热集成蒸馏流程.这种合成方法具有计算量最少,且可在微型机上连续地完成合成过程等特点.     

Studies in process synthesis—II: Evolutionary synthesis of optimal process flowsheets

The method most often used by process designers to solve the formidable task of synthesizing a process flowsheet is probably the evolutionary approach. The method is easily based on the previous experience of the designer and involves moving to better and better flow-sheets by making a succession of small improvements to an existing one.This paper presents a first step to organize the evotutionary synthesis of process flowsheets. In general terms it discusses the rules to make modifications and their desired properties, strategies to use these rules, and the various means to compare flowsheets.Specific rules and strategies are then proposed and successfully demonstrated on the evolutionary synthesis of multicomponent separation flowsheets. Where appropriate, proofs are given that these specific modification have the stated desired properties.     

A systematic approach for synthesizing a low-temperature distillation system

In this paper, by combining a stochastic optimization method with a refrigeration shaft work targeting method, an approach for the synthesis of a heat integrated complex distillation system in a low-temperature process is presented. The synthesis problem is formulated as a mixed-integer nonlinear programming (MINLP) problem, which is solved by simulated annealing algorithm under a random procedure to explore the optimal operating parameters and the distillation sequence structure. The shaft work targeting method is used to evaluate the minimum energy cost of the corresponding separation system during the optimization without any need for a detailed design for the heat exchanger network (HEN) and the refrigeration system (RS). The method presented in the paper can dramatical y reduce the scale and complexity of the problem. A case study of ethylene cold-end separation is used to il ustrate the application of the approach. Compared with the original industrial scheme, the result is encouraging.     

Computer-aided total flowsheet synthesis

Building on a previous approach, a systematic computer-based method for synthesizing a total flowsheet has been developed. This work uses a hierarchical concept, whereby separation tasks selected by the algorithm at the top level are converted to cost-estimated sharp separation sequences at the second level. The strategy at both levels is heuristic and evolutionary. Only the top-level system is described here, although the results include both phases. The synthesis of separation tasks is described by Lu and Motard, and extends the work of Nath and Motard.The flow rates and sizes of processing tasks are determined by a new goal-lumping strategy and a successive linear programming algorithm. Information from the lower level design of separations is fed back to the top-level decision procedure. The entire system is self-adaptive, but also includes opportunities for interaction by the user. Several test problems indicate that the present approach is superior to earlier work.     

A systematic procedure for synthesis of intensified nonsharp distillation systems with fewer columns

Nonsharp separation sequences can intrinsically improve thermodynamic efficiency than that of sharp sequences for a multicomponent distillation. There are much more nonsharp sequences than that of sharp sequences. In this paper, the synthesis of new intensified distillation systems from nonsharp separation sequences is presented. Such intensified distillation systems have fewer columns and have the potential to reduce both energy and capital costs than conventional configurations. First, the representation of any nonsharp sequence with the simple column configuration is found to be the necessary starting point. Then, five strategies are introduced which present different mechanisms to change the structures of the distillation configurations. Third, a systematic procedure is formulated which can achieve the intensified distillation systems with fewer columns systematically. Finally, the systematic method has been applied to different examples of nonsharp separation sequences. It is demonstrated that the method can be used to generate the new intensified distillation systems from any nonsharp separation sequences. The method is easy to use and can explicitly derive all of the intensified distillation systems for the nonsharp separation sequences for a multicomponent distillation.     

Optimization of Supercritical Extraction of Linalyl Acetate from Lavender via Box‐Behnken Design

Essential oil was extracted from lavender using supercritical carbon dioxide by means of a newly developed periodic static‐dynamic (PSD) procedure and the conventional semicontinuous (SC) technique. Applying GC‐FID analysis in conjunction with Box‐Behnken design, an optimum overall extraction yield (94.4 %) was obtained via PSD in contrast to 90 % for the SC method. The results indicate that supercritical fluid extraction is a viable technique for separation of constituents such as linalyl acetate, linalool, fenchone, and camphor for pharmaceutical and medicinal applications. Furthermore, a substantial reduction of energy consumption and solvent consumption is achieved with the developed PSD process compared to the conventional SC method.     

Quantitative Analysis of Mixtures of Metal Ions by the Ring-Oven Method: Uranium-Thorium-Zirconium-Titanium and Thorium-Cerium-Zirconium-Titanium

Abstract

Successful schemes for the separation of the constituents in the mixtures U-Th-Zr-Ti and Ce-Th-Zr-Ti have been worked out, using the ring-oven method. The constituents are first separated in the form of thin rings. The rings are then developed with selective organic reagents. For the determinations, the intensities of these rings are then compared visually with standard rings, similarly prepared with known amounts. The time required for complete separation and determination of the constituents is about 60–70 min, excluding the time required for the preparation of the standard scales. Separations are possible down to the following concentrations. Ce, 2.1 μg; Th, 3.5 μg; Ti, 0.36 μg; U, 1.8 μg; Zr, 2.7 μg.     

气液两相分离的免方程多尺度模拟方法

提出了一种用于模拟气液两相分离过程的免方程多尺度方法, 该方法以格子Boltzmann(LB)模型作为介观仿真器, LB模型进行少量演化步后运用二阶伸缩式投影方法对介观仿真器演化得到的结果进行有效的外推处理, 能够快速准确地获取后续演化步的结果, 从而实现对气液两相分离过程的多尺度模拟研究。对气液分离过程中饱和密度曲线和模型产生的伪速度大小的对比分析表明所提出的多尺度模拟方法能够快速准确地反映气液两相分离过程的宏观特性, 证明了所提方法的准确性和高效性。     

A Complex Procedure for the Analysis of Used Frying Fats

For an elaborate study of used frying fats a new complex procedure with two different sequences of analytical steps was developed. The first one consists of separation by molecular size (with gel permeation chromatography). As a combined result of GPC and TLC a gel chromatogram resolved according to polarity - i.e. molecular weight distribution curves of fractions with different polarities-can be obtained. Fractions with different molecular weights and polarities can be isolated by preparative GPC and TLC and characterized by spectroscopy. The other procedure includes fractionation by polarity (with adsorption column chromatography) followed by separation according to molecular size (by GPC). The most important groups of compounds of heated oils can be isolated in this way and their quantities (i.e. composition of the sample) can be determined as well.     

The Upper Limit of the Separation Efficiency of a Gas Centrifuge

A general theory of isotopes separation in a gas centrifuge based on a radial averaging method has been developed. The ultimate upper limit for a centrifuge separative power is expressed as a function of its external parameters. This is a more accurate definition of the centrifuge efficiency upper limit than the well-known Dirac's estimation or estimations of his followers, because it takes into account the feed flow value (throughput) and it provides the way to a one-dimensional diffusion equation without a lot of assumptions. For the first time the problem of an energy efficient centrifuge is formulated and the solution is obtained. Two cases of a centrifuge internal flow optimization are compared. The optimal internal circulations for both optimization cases are calculated. The results help us to understand how far the modern centrifuges are from their highest possible effectiveness limit and to identify ways to improve centrifuge performance.     

A diverse approach for the solution of the isothermal multiphase flash problem. Application to vapor-liquid-liquid systems

The paper presents a novel approach for the solution of the isothermal multiphase flash problem with particular application to systems exhibiting liquid-liquid-vapor equilibria. The approach includes a rigorous method for thermodynamic stability analysis as a first step and an efficient phase identification procedure. The stability analysis, exercised only once, uses a modification of the Gibbs tangent plane criterion. The identification procedure implements the results of the stability test in a sequence of liquid-liquid and liquid-vapor calculations only till the phase configuration with a minimum Gibbs energy is determined. The efficiency and reliability of the proposed new method is illustrated by solving three typical problems encountered in enhanced oil recovery, natural gas processing and petrochemical industry.     

WattsApp in Multiphase Systems by Gravity-Driven Buoyancy and Settling

Power and energy balances are described for simplified gravity-driven multiphase flows. It is emphasized that the power (→ Watts) or energy input by gravity impulse must be found back as the sum of all power or energy consumptions from the flow processes (→ Application). Examples are given for bubble columns and for batch liquid-liquid separation processes, based on simplified assumptions regarding the flow behavior. For large-scale apparatus, the flow characteristic of the involved phases is more complex and needs to be modeled more precisely. That is still a key challenge for scaling-up multiphase systems. Computational fluid dynamics is an adequate instrument but needs to be further developed and enhanced for multiphase flows in large-scale processes. And of course, any rigorous model must then be verifiable by a power balance.