Heterogeneous Batch Distillation Processes: Real System Optimisation

In this paper, optimisation of batch distillation processes is considered. It deals with real systems with rigorous simulation of the processes through the resolution full MESH differential algebraic equations. Specific software architecture is developed, based on the BatchColumn® simulator and on both SQP and GA numerical algorithms, and is able to optimise sequential batch columns as long as the column transitions are set. The efficiency of the proposed optimisation tool is illustrated by two case studies. The first one concerns heterogeneous batch solvent recovery in a single distillation column and shows that significant economical gains are obtained along with improved process conditions. Case two concerns the optimisation of two sequential homogeneous batch distillation columns and demonstrates the capacity to optimize several sequential dynamic different processes. For such multiobjective complex problems, GA is preferred to SQP that is able to improve specific GA solutions

Extractive distillation: recent advances in operation strategies

Extractive distillation is one of the efficient techniques for separating azeotropic and low-relativevolatility mixtures in various chemical industries. This paper first provides an overview of thermodynamic insight covering residue curve map analysis, the application of univolatility and unidistribution curves, and thermodynamic feasibility study. The pinch-point analysis method combining bifurcation shortcut presents another branch of study, and several achievements have been realized by the identification of possible product cut under the following key parameters: reflux ratio, reboil ratio, and entrainer-feed flow rate ratio. Process operation policies and strategy concerning batch extractive distillation processes are summarized in four operation steps. Several configurations and technological alternatives can be used when extractive distillation processes take place in a continuous or batch column, depending on the strategy selected for the recycle streams and for the main azeotropic feeds

Особенности ректификационного разделения многокомпонентных смесей

Objectives. To improve the process of developing energy-efficient flowsheets for the distillation separation of multicomponent aqueous and organic mixtures based on a comprehensive study of the phase diagram structures, including those in the presence of additional selective substances.Methods. Thermodynamic-topological analysis of phase diagrams; modeling of phase equilibria in the AspenTech software package using the equations of local compositions: Non-Random Two Liquid and Wilson; computational experiment to determine the column parameters for separation flowsheets of model and real mixtures of various nature.Results. The fractionation conditions of the origin multicomponent mixture due to the use of sharp distillation, pre-splitting process, extractive distillation with individual and binary separating agents were revealed. The columns operation parameters and the energy consumption of the separation flowsheets ensuring the achievement of the required product quality with minimal energy consumption were determined.Conclusions. Using the original methods developed by the authors earlier and based on the generalization of the results obtained, new approaches to the synthesis of energy-efficient multicomponent mixtures separation flowsheets were proposed. The provisions that form the methodological basis for the development of flowsheets for the separation of multicomponent mixtures and supplement the standard flowsheet synthesis plan with new procedures were formulated.Цели. Совершенствование процесса разработки энергоэффективных схем ректификационного разделения многокомпонентных водных и органических смесей на основе комплексного исследования структуры фазовой диаграммы, в том числе в присутствии селективных дополнительных веществ.Методы. Термодинамико-топологический анализ фазовых диаграмм; моделирование фазовых равновесий в программном комплексе AspenTech с использованием уравнений локальных составов Non-Random Two Liquid, Вильсона; вычислительный эксперимент по определению параметров работы колонн схем разделения модельных и реальных смесей разной природы.Результаты. Выявлены условия фракционирования исходной многокомпонентной смеси за счет использования промежуточного заданного разделения, предварительного расслаивания, экстрактивной ректификации с индивидуальными и бинарными разделяющими агентами. Определены параметры работы колонн и энергозатраты схем разделения, обеспечивающие достижение требуемого качества продуктов при минимальных энергозатратах.Выводы. С использованием разработанных ранее авторами оригинальных методик и на основе обобщения полученных результатов предложены новые подходы к синтезу энергоэффективных схем разделения многокомпонентных смесей. Сформулированы положения, которые составляют методологическую основу разработки принципиальных схем разделения многокомпонентных смесей и дополняют типовой план синтеза схем новыми процедурами

Application of process synthesis for the recovery of valuable chemicals from an industrial waste stream

MSc ThesisA dissertation submitted in partial fulfilment of the requirements for the degree Master of Science in Engineering to the Faculty of Engineering and the Built Environment, School of Chemical and Metallurgical Engineering, University of the Witwatersrand, Johannesburg, 2018This work aims at designing and simulating on Aspen Plus process simulator a process that can recover valuable chemicals from a High Organic Waste (HOW) stream produced at Sasol Secunda plant, South Africa. The waste is made up of low boiling point organic components such as pyridine, acetonitrile and Methyl Ethyl Ketone and water. Currently, the waste is incinerated without energy recovery. This practice serves to exacerbate the already high greenhouse gases emissions from the plant, but more importantly, it results in the missed opportunity to maximize revenues through resale of recycled valuable chemicals. The recovery of valuable chemicals from the HOW is made difficult by the formations of azeotrope between organic components and water; at least 6 azeotropes exist in the HOW stream. In this work the emphasis is on pyridine because of its established market value and demand. Pyridine market size is about 400 million USD in 2017 and is expected to increase to over 600 million USD by 2021 mainly due to increased usage in the agrochemical industry. Water integration strategy was also assessed demand because of the reported need to improve water utilization efficiency at Sasol Secunda plant. The recovery was achieved in 2 separate steps: 1) water-pyridine mixture was separated from the rest of the HOW stream using fractional distillation and 2) pyridine enrichment section which was designed using thermodynamic tools such as residue curve maps and isovolatility curves. The rest of the HOW stream (light fractions) was sent to the currently used incinerator. Liquid-liquid extraction and azeotropic distillation were considered for the pyridine enrichment step. Results showed that the combination of liquid-liquid extraction and distillation offered the benefit of a lower entrainer to azeotropic mixture ratio (EA) compared to azeotropic distillation. This gave the lowest recorded EA at 0.320:1. The comparison between the proposed process and the incineration of the whole HOW stream showed that the implementation of the process proposed reduced the incineration load by 60wt% and CO and CO2 emissions by 50%. Dividing Wall column process integration technique was implemented to reduce the number of distillation columns in the proposed process and 10% reduction in the reboiler and condenser duties was observed. Implementation of DWC further improved the purity of the recovered pyridine from 96mol% to over 99.9mol%. Preliminary economic evaluation carried out on Aspen Plus showed that the proposed recovery process was profitable with an Internal Rate of Return (IRR) of 20% and a payback period of 4.5 years.MT 201

Сравнение схем экстрактивной ректификации смесей метанол–тетрагидрофуран–вода

Objectives. Synthesis and comparative analysis of the extractive distillation flowsheets for aqueous mixtures of solvents utilized in pharmaceutical industries using the example of a methanol−tetrahydrofuran−water system with various compositions. The ternary system contains two minimally boiling azeotropes that exist in a vapor–liquid phase equilibrium. To evaluate the selective effect of glycerol, the phase equilibria of the methanol–tetrahydrofuran–water and methanol–tetrahydrofuran–water–glycerol systems at 101.32 kPa were studied.Methods. The calculations were carried out in the Aspen Plus V.9.0 software package. The vapor–liquid equilibria were simulated using the non-random two-liquid (NRTL) equation with the binary interaction parameters of the software package database. To account for the non-ideal behavior of the vapor phase, the Redlich–Kwong equation of state was used. The calculations of the extractive distillation schemes were carried out at 101.32 kPa.Results. The conceptual flowsheets of extractive distillation are proposed. The flowsheets consist of three (schemes I–III) or four (scheme IV) distillation columns operating at atmospheric pressure. In schemes I and II, the extractive distillation of the mixtures is carried out with tetrahydrofuran isolation occurring in the distillate stream. Further separation in the schemes differs in the order of glycerol isolation: in the third column for scheme I (traditional extractive distillation complex) or in the second column for scheme II (two-column extractive distillation complex + methanol/water separation column). Sсheme III caters to the complete dehydration of the basic ternary mixtures, followed by the extractive distillation of the azeotropic methanol–tetrahydrofuran system, also with glycerol. Sсheme IV includes a preconcentration column (for the partial removal of water) and a traditional extractive distillation complex.Conclusions. According to the criterion of least energy consumption for separation (the total load of the reboilers of distillation columns), sсheme I (a traditional complex of extractive distillation) is recommended. Additionally, the energy expended for the separation of the basic equimolar mixture using glycerol as the extractive agent was compared with that expended using another selective agent: 1,2-ethanediol. Glycerol is an effective extractive agent because it reduces energy consumption, in comparison with 1,2-ethanediol, by more than 5%.Цели. Синтез и сравнительный анализ схем экстрактивной ректификации водных смесей растворителей фармацевтических производств на примере системы метанол–тетрагидрофуран–вода различного состава. Трехкомпонентная система содержит два минимально кипящих азеотропа, которые присутствуют в диапазоне существования парожидкостного равновесия. Для оценки селективного действия глицерина исследованы фазовые равновесия систем метанол–тетрагидрофуран–вода и метанол–тетрагидрофуран–вода–глицерин при 101.32 кПа.Методы. Вычислительный эксперимент выполнен на платформе Aspen Plus V.9.0. Проведены расчеты фазовых равновесий по уравнению NRTL (Non-Random Two-Liquid) с параметрами бинарного взаимодействия базы данных программного комплекса. Для учета неидеального поведения паровой фазы использовали уравнение состояния Редлиха–Квонга. Расчеты схем экстрактивной ректификации проведены при 101.32 кПа.Результаты. Предложены принципиальные технологические схемы разделения (I–IV), состоящие из трех (I–III) или четырех (IV) ректификационных колонн, работающих при атмосферном давлении. В схемах I, II проводилась экстрактивная ректификация базовых смесей с различным содержанием воды для выделения в дистиллатном потоке тетрагидрофурана. Дальнейшее разделение в схемах различалось очередностью выделения глицерина: в третьей колонне схемы I (традиционный трехколонный комплекс экстрактивной ректификации) или во второй колонне схемы II (двухколонный комплекс экстрактивной ректификации + колонна разделения метанола и воды). В схеме III предусмотрено полное обезвоживание базовых трехкомпонентных смесей с последующей экстрактивной ректификацией азеотропной системы метанол–тетрагидрофуран также с глицерином. Схема IV состоит из колонны концентрирования (частичного удаления воды) и традиционного комплекса экстрактивной ректификации.Выводы. По критерию наименьших энергозатрат на разделение (суммарная нагрузка кипятильников ректификационных колонн) рекомендована схема I (традиционный комплекс экстрактивной ректификации). Дополнительно проведено сравнение энергозатрат схемы I при разделении смеси эквимолярного состава с другим селективным веществом – этиленгликолем, предложенным ранее в качестве агента. Глицерин является эффективным экстрактивным агентом, поскольку обеспечивает снижение энергозатрат более чем на 5%

Process Design Based on CO2-Expanded Liquids as Solvents

Magdeburg, Univ., Fak. für Verfahrens- und Systemtechnik, Diss., 2014von Kongmeng Y

VISUALIZATION METHODS FOR EVALUATION OF FEASIBLE SEPARATIONS OF AZEOTROPIC MIXTURES

In this study the visualization system AVS (Application Visualization System) is applied. This tool is provided with a module library for userfriendly modelling of systems under study. Three data viewers are implemented: Image Viewer, Graph Viewer and Geometry Viewer allowing the graphical representation of multidimensional data fields as the boiling and dew temperatures as a function of the composition. By using special modules the graphical representations can be characterized by colours, brightness and other effects; by the zoom module the scale can be varied; there are also possibilities for the animation of the objects under study, the representation of isolines, for example of temperature or driving forces, as well as the calculation and representation of vector fields. The last option makes it possible to construct representation combining information about the residue curve map and the temperature surface

Distillation

The purpose of this book is to offer readers important topics on the modeling, simulation, and optimization of distillation processes. The book is divided into four main sections: the first section is introduction to the topic, the second presents work related to distillation process modeling, the third deals with the modeling of phase equilibrium, one of the most important steps of distillation process modeling, and the the fourth looks at the reactive distillation process, a process that has been applied successfully to a number of applications and has been revealed as a promising strategy for a number of recent challenges