Extractive Distillation Systems Involving Complex Columns with Partially Coupled Heat and Material Flows

A method based on the representation of flowsheets as graphs is proposed to synthesize flowsheets of extractive distillation of multicomponent azeotropic mixtures in complex columns with partially coupled heat and material flows. It is shown that the flowsheets constructed can provide a significant decrease in the energy consumption for separation because the process becomes structurally closer to thermodynamically reversible distillation.     

Use of Columns with Coupled Heat and Material Flows in Separation of Multicomponent Zeotropic Mixtures

The possibility of bringing real distillation processes to thermodynamically reversible distillation is considered. Distillation systems involving partially or fully thermally coupled columns are suggested for the separation of ternary mixtures. The transformation of the optimal flowsheet in response to variation of feed composition is studied. Recommendations are provided as to the choice of an energy saving distillation design.__________Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 3, 2005, pp. 264–268.Original Russian Text Copyright © 2005 by Ivanova, Timoshenko.     

Synthesis of Optimal Distillation Flowsheets Consisting of Columns with Various Numbers of Sections

Distillation flowsheets consisting of simple columns, both simple columns and complex columns with side streams, and simple column–complex column sequences are considered for zeotropic four-component mixtures. Applicability criteria are suggested for the complex columns.     

Application of Graphs of Distillation Trajectories to Synthesis of Separation Flowsheets

A graph method and a matrix method are proposed for synthesizing distillation flowsheets by analyzing process trajectories.     

改进的物料分配图用于非清晰精馏过程合成

本文提出一种改进的物料分配图(material allocation diagfam)表达分离过程。并在此基础上提出一种非清晰精馏过程合成方法。示例表明:本方法可很好地处理单一进料、只具有旁路的非清晰精馏过程合成问题,有时甚至可直接得最优解。     

完全能量耦合精馏塔的设计、模拟与优化

在很多的工业生产中,都需要进行精馏工作,尤其是化学工业,精馏过程的效率与化学工业的发展有着密不可分的联系。精馏过程是一个对能量消耗非常大的过程,一直以来,怎样使精馏过程更加简单、高效,怎样使精馏过程中能量利用效率更高,是相关企业和部门密切关注的问题。因此对完全能量耦合精馏塔的设计、模拟与优化的相关内容做了研究。     

Homology and Isomerism of the Structures of Phase Diagrams and Distillation Flowsheets

Theoretical Foundations of Chemical Engineering - The applications of homology and isomerism to the structure of phase diagrams and distillation flowsheets of multicomponent mixtures were...     

Energy Savings in Flowsheets based on Combination of Distillation and Splitting Processes

The relationship between structures of ternary systems phase diagram, separation flowsheets including distillation columns and decanters and their energy consumption are discussed. Phase equilibrium diagrams of two ternary systems cyclohexanol + cyclohexanone + water and propanol-1 + cyclohexane + acetonitrile were studied. A number of isomeric flowsheets were proposed for separation of the first ternary mixture and the influence of devices (columns and decanters) arrangement on the flowsheets energy consumption were shown. The influence of separation conditions in a distillation column (the ratio of distillate and bottom flows) on the energy consumption of separation flowsheet were demonstrated on the example system propanol-1 + cyclohexane + acetonitrile.     

A New Configuration for a Fully Thermally Coupled Distillation Column with a Postfractionator and Separated Main Columns

The installation of a postfractionator into a fully thermally coupled distillation column (FTCDC) significantly improves the distillation column efficiency, but the column operation is more difficult than for the original FTCDC. A modified configuration of the postfractionator FTCDC having sectionalized main columns is proposed for operational improvement, and its performance is examined through the HYSYS simulation of a BTX fractionation process. By setting different pressures for the various sections of the main columns, the proposed distillation column facilitates easy vapor transfer between the sections without the need to utilize compressors. The outcome of a dynamic simulation on the column shows that the control of the column pressure is easily undertaken and the specifications of three products in the BTX process can be separately controlled to facilitate ease of column operation.     

Design and Control of a Fully Thermally Coupled Distillation Column Modified from a Conventional System

A modified fully thermally coupled distillation column is proposed, with utilization of the existing distillation columns of the conventional system, and its control scheme is suggested here. The proposed distillation system is applied to a benzene‐toluene‐xylene (BTX) separation process, of which the system design and control performance evaluation are conducted using the HYSYS software. The performance of the suggested 3 × 3 control is examined in the set‐point tracking of product specification and the regulation for the changes of feed flow and composition. The pairings of three proportional‐integral control loops are the reflux flow and the specification of overhead product, the prefractionator vapor flow and that of the side product, and the vapor boil‐up rate and that of the bottom product. The multi‐variable controllability using various indices is investigated for the proposed control scheme, and the controllability is compared with that of the cross‐pairing between the control loops of the side and bottom products.     

热泵热集成精馏流程的优化设计与综合

从综合的角度详细讨论了热泵精馏的原理,提炼出了用于综合的热泵精馏规则,并开发了综合所用的热泵精馏简捷经济评价方法,提出了一个两水平综合策略,给出了热泵精馏综合步骤。实例研究表明,本文开发的算法及提出的规则用于热泵热集成精馏流程的综合,能够得出最优的絷泵精馏流程。     

A Numerical Study of Heat Transfer Mechanisms in Gas-Solids Flows Through Pipes Using a Coupled CFD and DEM Model

A two dimensional numerical model has been developed to simulate heat transfer in gas-solids flows through pipes, in which the gas phase is modelled as a continuum using the Computational Fluid Dynamics (CFD) approach and the solids phase is modelled by the Discrete Element Method (DEM). This allows interactions between gas, particles, and pipe wall to be accounted at the scale of individual particles and convective and conductive heat transfers to be calculated using local gas and solids parameters. The predicted changes to the flow structures and the various heat transfer mechanisms due to the presence of particles were analyzed and compared with other workers' findings. This study has quantitatively demonstrated the crucial effect of particle transverse motion on heat transfers due firstly to the thermal energy transport by rebounding particles and secondly to the modification of the fluid thermal boundary layer characteristics.     

带有冷存料塔釜的热敏物料间歇精馏

提出了带有冷存料塔釜的热敏物料间歇精馏流程，该流程包括冷存料塔釜、预热-冷却器、循环泵、蒸发器和精馏塔及冷凝器。该过程的设备降解指数比常规间歇精馏过程小得多。通过模拟计算，研究了回流比、预热-冷却器面积、塔釜冷却量、蒸发器加热量以及泵循环流量对热敏精馏过程的影响。     

Fluid Mechanics of Distillation Trays (I): Depth-Averaged Theory and One-Dimensional Flows

Abstract

Rigorous design of a distillation column requires a better fundamental understanding of the fluid mechanics of bubble formation and global flows on trays than that currently available. To progress beyond the empirical-or correlation-based state of understanding that currently exists, a theoretical and computational framework is described here that is based on reducing the governing set of three-dimensional conservation equations to a two-dimensional set by averaging them across the depth of the fluid film flowing across the tray. In contrast to related previous works, realistic boundary conditions to the flow problem are provided in this paper by solving simultaneously for the flow on the tray and its inlet and outlet downcomers. In this first of a series of papers, attention is focused on situations in which the flow is invariant in the direction perpendicular to the main flow direction. By means of such a set of one-dimensional, depth-averaged equations, predictions are made in several interesting and practically important situations in which the flow is either steady or time dependent.     

Hybrid Distillation/Melt Crystallization Process Using Thermally Coupled Arrangements: Optimization with evolutive algorithms

Innovative hybrid processes offer significant cost savings, particularly for azeotropic or close-boiling mixtures. Hybrid separation processes are characterized by the combination of two or more different unit operations, which contribute to the separation task by different physical separation principles. Despite of the inherent advantages of hybrid separation processes, they are not systematically exploited in industrial applications due to the complexity of the design and optimization of these highly integrated processes. In this work we study a hybrid distillation/melt crystallization process, using conventional and thermally coupled distillation sequences. The design and optimization were carried out using, as a design tool, a multi-objective genetic algorithm with restrictions coupled with the process simulator Aspen Plus™, for the evaluation of the objective function. The results show that this hybrid configuration with thermally coupled arrangements is a feasible option in terms of energy savings, capital investment and control properties.     

连续催化酯化-精馏联合过程合成乙酸正丙酯的研究

在一连续酯化-精馏装置中,对以固体酸为催化剂、乙酸与正丙醇为原料合成乙酸正丙酯的酯化反应进行了研究.结果表明催化剂在反应条件下有很高的活性,运行300小时后仍具有很好的稳定性和寿命,酯化率达96%以上.     

利用人工神经网络和遗传算法对热偶精馏过程进行模拟优化

In this paper, a new approach using artificial neural network and genetic algorithm for the optimization of the thermally coupled distillation is presented. Mathematical model can be constructed with artificial neural network based on the simulation results with ASPEN PLUS. Modified genetic algorithm was used to optimize the model. With the proposed model and optimization arithmetic, mathematical model can be calculated, decision variables and target value can be reached automatically and quickly. A practical example is used to demonstrate the algorithm.     

热敏物料的蒸馏及常用设备(I)——蒸馏过程的特征

本文描述了热敏物料的蒸馏特点 ,蒸馏过程和某些热敏物质的热反应过程同时进行 ,并以热敏度和非热敏度为目标进行了数学模拟计算     

催化精馏合成乙二醇乙醚的研究

催化精馏是将固体催化剂布于精馏塔内,它既加速了化学反应,又可作为分离过程的传质表面。本文研究了在内径为35mm的不锈钢塔中,用NKC—01催化剂从乙醇和环氧乙烷合成乙二醇乙醚(单醚)的过程,详细考察了进料比,操作压力,处理量等因素对过程的影响,找到的适宜条件为:进料比(乙醇/环氧乙烷)=6～8(摩尔);处理量为104.0Nm~3环氧乙烷/h(m~3催化剂);操作压力=2.35×10~5Pa。在此条件下乙二醇乙醚对环氧乙烷的收率为90％(mol);环氧乙烷的单程收率为93％;乙二醇乙醚的选择性为97％。为考察塔内的流体力学条件对催化反应的影响,在搅拌容器中测定了过程的反应动力学。为保证此搅拌容器中的液体流速接近塔内操作条件下的流速,以确定适宜的搅拌器转速,我们用DANTEC MODEL 2020激光测速仪测定了不同搅拌器转速下容器中液体的流速。通过研究可以看出:在塔内的操作条件下,与化学反应相比,扩散阻力可以被忽略。