Analysis of the Zone Connecting Consecutive Sectors in Generalized Distillation Columns by Using the Ponchon-Savarit Method

Ponchon-Savarit is a classical graphical method for the design of binary distillation columns. This method is still widely used, mainly with didactical purposes, though it is also valid for preliminary calculations. Nevertheless, no complete description has been found in books and situations such as different thermal feed conditions, multiple feeds, possibilities to extract by-products or to add or remove heat, are not always considered. In this work we provide, a systematic analysis of the Ponchon-Savarit method by developing generalized equations for the operating lines or difference points, as well as a consistent analysis of what may happen in the zone between two consecutive trays of the corresponding sectors separated by a lateral stream of feed, product, or a heat removal or addition. The graphical interpretation of all situations shown allows a clarifying view of the different possibilities in the rectifying column and completes the existing literature about this method

Modelling of a dynamic multiphase flash: the positive flash. Application to the calculation of ternary diagrams

A general and polyvalent model for the dynamic simulation of a vapor, liquid, liquid-liquid, vapor-liquid or vapor-liquid-liquid stage is proposed. This model is based on the -method introduced as a minimization problem by Han & Rangaiah (1998) for steady-state simulation. They suggested modifying the mole fraction summation such that the same set of governing equations becomes valid for all phase regions. Thanks to judicious additional switch equations, the -formulation is extended to dynamic simulation and the minimization problem is transformed into a set of differential algebraic equations (DAE). Validation of the model consists in testing its capacity to overcome phase number changes and to be able to solve several problems with the same set of equations: calculation of heterogeneous residue curves, azeotropic points and distillation boundaries in ternary diagrams

Learning distillation by a combined experimental and simulation approach in a three steps laboratory : Vapor pressure, vapor-liquid equilibria and distillation column

Distillation is one of the most important separation process in industrial chemistry. This operation isbased on a deep knowledge of the fluid phase equilibria involved in the mixture to be separated. In par-ticular, the most important aspects are the determination of the vapor pressures of the single compoundsand the correct representation of the eventual not ideality of the mixture. Simulation science is a fun-damental tool for managing these complex topics and chemical engineers students have to learn andto use it on real case-studies. To give to the students a complete overview of these complex aspects, alaboratory experience is proposed. Three different work stations were set up: i) determination of vaporpressure of two pure compounds; ii) the study of vapor-liquid equilibria of a binary mixture; iii) the useof a continuous multistage distillation column in dynamic and steady-state conditions. The simulation ofall these activities by a commercial software, PRO II by AVEVA, allows to propose and verify the thermo-dynamic characteristics of the mixture and to correctly interpret the distillation column data. Moreover,the experimental plants and the data elaboration by classical equations are presented. The students arerequest to prepare a final report in which the description of the experimental plants and experimentalprocedure, the interpretation of the results and the simulation study are critically discussed in order toencourage them to reason and to acquire the concepts of the course.Two different questionnaires each with 7 questions, for the course and for the laboratory, are proposedand analyzed. The final evaluation of the students was strongly positive both for the course as a wholeand for the proposed laboratory activities

Comparative analysis of Extractive Distillation and Pressure Swing Distillation for different azeotropic mixtures

Treballs Finals de Grau d'Enginyeria Química, Facultat de Química, Universitat de Barcelona, Curs: 2018-2019, Tutors: Jordi Bonet Ruiz, Alexandra Bonet RuizOne of the most used and important unit operation to separate mixtures in the chemical industry is distillation. Actually approximately 95% of all the separations are carried out by distillation processes, and indeed, a heuristic indicate that whenever possible distillation must be the first option to separate mixtures. There is situations where is not possible the separation by this operation as a result of closely boiling points (below 50ºC), low relative volatilities or the presence of azeotropes. In the first two cases, a high number of trays would be required for the column. In the case of azeotropes, the separation is impossible due to the composition of liquid and vapor is the same. For that reason, enhanced distillation techniques are necessary. In this work, a comparative analysis about these available techniques to break binary azeotropic mixtures is conducted to conclude which one is more convenient. In particular, it focus on the extractive distillation (ED) and the distillation by variation of the pressure known as pressure swing distillation (PSD). ED is one of the most used and known techniques characteristically by the addition of an extractive agent (EA), with high boiling point and non-volatile, which modifies the relative volatilities thus allowing the recovery of one pure compound at extractive distillation column (EDC). To obtain the other compound and recovery the extractive agent, a second column is required: recovery distillation column (RDC). The disadvantages of this technique are the cost associated with the recovery of the EA and that always there will be traces of the added compound impurifying the products obtained. In the case of PSD, no additional components are added but is exploited the sensitive of the mixture by changes of the pressure. There are two columns one of which works at high pressure (HPC) and a second at low pressure (LPC), thus varying the azeotropic composition and obtaining the pure compounds. This second is the least used because it is necessary for the mixture to be sensitive to changes in the pressure. Actually, there is a general tendency to wonder that by working with pressure the process is more expensive or less feasible.Therefore, one of the first questions in the early stages of conception of a process is the selection of which available techniques explained is the more feasible to break an azeotrope. Unfortunately, in my knowledge there is no works that focus on the comparison of both alternatives. The projects often focus on one of the techniques and there are some available articles which compares both for a specific mixture in basis economical terms. To answer that question, an intense bibliographic research is carried out to select the different cases of binary mixtures which are sensitive to pressure changes. A list of 26 mixtures is selected and going to be studied out more thoroughly. The information available and necessary it is searched at one simulator, databases and one book thus reducing the list at 23 mixtures. The simulator selected is Aspen Plus V10. Then, based on the corresponding material balances and applying a simplified mathematical model (infinite/infinite analysis), the different energy efficiencies are obtained. For this calculus it is necessary to know the compositions and boiling-points. The variation of the azeotropic composition with the pressure and the sensitive is also being studied. Consecutively, the efficiencies achieved in the two alternatives are compared distinguishing azeotropes of minimum and maximum boiling point. Finally, to find the reason of the results obtained a critical comparison is conducted to establish useful general indications on the selection during the first stages of the design proces

Minimization of Utilities Consumption in a Distillation Column with and without Heat Integration for Separation of a Binary System of Acetone-Methanol

U ovom radu razvijeni su matematički modeli za destilacijsku kolonu s toplinskom integracijom i bez toplinske integracije. Simulacija matematičkih modela primijenjena je za određivanje potrošnje energije u destilacijskoj koloni za razdvajanje binarnog sustava acetona i metanola. Predloženi modeli određuju vrijednosti procesnih varijabli s ciljem utvrđivanja minimalne potrošnje pogonskih sredstava. Prikazana je usporedba rezultata toplinski integrirane destilacijske kolone s rezultatima neintegrirane destilacijske kolone. Rezultati su pokazali da se ušteda energije može postići primjenom toplinske integracije. Predloženi modeli mogu se primijeniti za projektiranje novih ili preuređenje postojećih destilacijskih kolona za razdvajanje binarnih smjesa. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.In this work, mathematical models for a distillation column with and without heat integration have been developed. Simulation based on the developed mathematical models was used to determine the energy consumption in the distillation column for separation of a binary system of acetone and methanol. The proposed models determine the values of process variables in order to obtain the minimum utilities consumption. The comparison of results of the heat-integrated distillation column with those of the non-integrated distillation column are presented. The results show that energy savings could be achieved using heat integration. The proposed models may be applied to the design of new or redesign of existing distillation columns for separation of binary mixtures. This work is licensed under a Creative Commons Attribution 4.0 International License

Thermodynamic Insight for the Design and Optimization of Extractive Distillation of 1.0-1a Class Separation

Nous étudions la distillation extractive continue de mélanges azéotropiques à temperature de bulle minimale avec un entraineur lourd (classe 1.0-1a) avec comme exemples les mélanges acétone-méthanol avec l’eau et DIPE-IPA avec le 2-méthoxyethanol. Le procédé inclut les colonnes de distillation extractive et de régénération de l’entraineur en boucle ouverte et en boucle fermée. Une première stratégie d’optimisation consiste à minimiser la fonction objectif OF en cherchant les valeurs optimales du débit d’entraineur FE, les positions des alimentations en entraineur et en mélange NFE, NFAB, NFReg, les taux de reflux R1, R2 et les débits de distillat de chaque colonne D1, D2. OF décrit la demande en énergie par quantité de distillat et tient compte des différences de prix entre les utilités chaudes et froides et entre les deux produits. La deuxième stratégie est une optimisation multiobjectif qui minimise OF, le coût total annualisé (TAC) et maximise deux nouveaux indicateurs thermodynamiques d’efficacité de séparation extractive totale Eext et par plateau eext. Ils décrivent la capacité de la section extractive à séparer le produit entre le haut et le bas de la section extractive. L’analyse thermodynamique des réseaux de courbes de résidu ternaires RCM et des courbes d’isovolatilité montre l’intérêt de réduire la pression opératoire dans la colonne extractive pour les séparations de mélanges 1.0-1a. Une pression réduite diminue la quantité minimale d’entraineur et accroît la volatilité relative du mélange binaire azéotropique dans la région d’opération de la colonne extractive. Cela permet d’utiliser un taux de reflux plus faible et diminue la demande énergétique. La première stratégie d’optimisation est conduite avec des contraintes sur la pureté des produits avec les algorithmes SQP dans les simulateurs Aspen Plus ou Prosim Plus en boucle ouverte. Les variables continues optimisées sont : R1, R2 et FE (étape 1). Une étude de sensibilité permet de trouver les valeurs de D1, D2 (étape 2) et NFE, NFAB, NFReg (étape 3), tandis l’étape 1 est faite pour chaque jeu de variables discrètes. Enfin le procédé est resimulé en boucle fermée et TAC, Eext et eext sont calculés (étape 4). Les bilans matières expliquent l’interdépendance des débits de distillats et des puretés des produits. Cette optimisation permet de concevoir des procédés avec des gains proches de 20% en énergie et en coût. Les nouveaux procédés montrent une amélioration des indicateurs Eext et eext. Afin d’évaluer l’influence de Eext et eext sur la solution optimale, la seconde optimisation multiobjectif est conduite. L’algorithme génétique est peu sensible à l’initialisation, permet d’optimiser les variables discrètes N1, N2 et utilise directement le shéma de procédé en boucle fermée. L’analyse du front de Pareto des solutions met en évidence l’effet de FE/F et R1 sur TAC et Eext. Il existe un Eext maximum (resp. R1 minimum) pour un R1 donné (resp. Eext). Il existe aussi un indicateur optimal Eext,opt pour le procédé optimal avec le plus faible TAC. Eext,opt ne peut pas être utilisé comme seule fonction objectif d’optimisation mais en complément des autres fonctions OF et TAC. L’analyse des réseaux de profils de composition extractive explique la frontière du front de Pareto et pourquoi Eext augmente lorsque FE diminue et R1 augmente, le tout en lien avec le nombre d’étage. Visant à réduire encore TAC et la demande énergétique nous étudions des procédés avec intégration énergétique double effet (TEHI) ou avec des pompes à chaleur (MHP). En TEHI, un nouveau schéma avec une intégration énergétique partielle PHI réduit le plus la demande énergétique. En MHP, la recompression partielle des vapeurs VRC et bottom flash partiel BF améliorent les performances de 60% et 40% respectivement. Au final, le procédé PHI est le moins coûteux tandis que la recompression totale des vapeurs est la moins énergivore. ABSTRACT : We study the continuous extractive distillation of minimum boiling azeotropic mixtures with a heavy entrainer (class 1.0-1a) for the acetone-methanol with water and DIPE-IPA with 2-methoxyethanol systems. The process includes both the extractive and the regeneration columns in open loop flowsheet and closed loop flowsheet where the solvent is recycled to the first column. The first optimization strategy minimizes OF and seeks suitable values of the entrainer flowrate FE, entrainer and azeotrope feed locations NFE, NFAB, NFReg, reflux ratios R1, R2 and both distillates D1, D2. OF describes the energy demand at the reboiler and condenser in both columns per product flow rate. It accounts for the price differences in heating and cooling energy and in product sales. The second strategy relies upon the use of a multi-objective genetic algorithm that minimizes OF, total annualized cost (TAC) and maximizes two novel extractive thermodynamic efficiency indicators: total Eext and per tray eext. They describe the ability of the extractive section to discriminate the product between the top and to bottom of the extractive section. Thermodynamic insight from the analysis of the ternary RCM and isovolatility curves shows the benefit of lowering the operating pressure of the extractive column for 1.0-1a class separations. A lower pressure reduces the minimal amount of entrainer and increases the relative volatility of original azeotropic mixture for the composition in the distillation region where the extractive column operates, leading to the decrease of the minimal reflux ratio and energy consumption. The first optimization strategy is conducted in four steps under distillation purity specifications: Aspen Plus or Prosim Plus simulator built-in SQP method is used for the optimization of the continuous variables: R1, R2 and FE by minimizing OF in open loop flowsheet (step 1). Then, a sensitivity analysis is performed to find optimal values of D1, D2 (step 2) and NFE, NFAB, NFReg (step 3), while step 1 is done for each set of discrete variables. Finally the design is simulated in closed loop flowsheet, and we calculate TAC and Eext and eext (step 4). We also derive from mass balance the non-linear relationships between the two distillates and how they relate product purities and recoveries. The results show that double digit savings can be achieved over designs published in the literature thanks to the improving of Eext and eext. Then, we study the influence of the Eext and eext on the optimal solution, and we run the second multiobjective optimization strategy. The genetic algorithm is usually not sensitive to initialization. It allows finding optimal total tray numbers N1, N2 values and is directly used with the closed loop flow sheet. Within Pareto front, the effects of main variables FE/F and R1 on TAC and Eext are shown. There is a maximum Eext (resp. minimum R1) for a given R1 (resp. Eext). There exists an optimal efficiency indicator Eext,opt which corresponds to the optimal design with the lowest TAC. Eext,opt can be used as a complementary criterion for the evaluation of different designs. Through the analysis of extractive profile map, we explain why Eext increases following the decrease of FE and the increase of R1 and we relate them to the tray numbers. With the sake of further savings of TAC and increase of the environmental performance, double-effect heat integration (TEHI) and mechanical heat pump (MHP) techniques are studied. In TEHI, we propose a novel optimal partial HI process aiming at the most energy saving. In MHP, we propose the partial VRC and partial BF heat pump processes for which the coefficients of performance increase by 60% and 40%. Overall, optimal partial HI process is preferred from the economical view while full VRC is the choice from the environmental perspective

Low pressure design for reducing energy cost of extractive distillation for separating Diisopropyl ether and Isopropyl alcohol

We show how reducing pressure can improve the design of a 1.0-1a mixture homogeneous extractive distillation process and we use extractive efficiency indicators to compare the optimality of different designs. The case study concerns the separation of the diisopropyl ether (DIPE)–isopropyl alcohol (IPA) minimum boiling azeotrope with heavy entrainer 2-methoxyethanol. We first explain that the unexpected energy cost OF decrease following an increase of the distillate outputs is due to the interrelation of the two distillate flow rates and purities and the entrainer recycling through mass balance when considering both the extractive distillation column and the entrainer regeneration column. Then, we find that for the studied case a lower pressure reduces the usage of entrainer and increases the relative volatility of DIPE–IPA for the same entrainer content in the extractive column. A 0.4 atm operating pressure is selected to enable the use of cheap cooling water in the condenser. We run an optimization of the entrainer flow rate, both columns reflux ratios, distillates and feed locations by minimizing the total energy consumption per product unit. Double digit savings in energy consumption are achieved while TAC is reduced significantly. An extractive efficiency indicator that describes the ability of the extractive section to discriminate the desired product between the top and the bottom of the extractive section of the extractive section is calculated for comparing and explaining the benefit of lowering pressure on the basis of thermodynamic insight

Simulation of ethanol production processes from sugar and sugarcane bagasse, aiming process integration and maximization of energy and bagasse surplus

Orientadores: Rubens Maciel Filho, Carlos Eduardo Vaz RossellDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuimicaResumo: O objetivo desta dissertação é apresentar a descrição e a simulação de processos de produção de etanol a partir do caldo e do bagaço da cana-de-açúcar, visando o levantamento do consumo de energia destes processos. Foram consideradas melhor ias no processo convencional de produção de etanol a partir do caldo, tais como a realização de eficientes tratamento e esterilização do caldo, a condução da fermentação a temperaturas mais baixas (28°C) do que as utilizadas atuamente, o estudo de configuração de destilação duplo efeito e a otimização de processos de desidratação para produção de etanol anidro. O processo de produção de etanol a partir do bagaço da cana-de-açúcar é baseado em um processo de hidrólise do tipo Organosolv com ácido diluído em três etapas: pré-hidrólise da hemicelulose, deslignificação Organosolv e hidrólise da celulose. Considerando-se a utilização de 70 % do bagaço gerado nas moendas como matéria prima do processo de hidrólise estudado, seria possível aumentar a produção de etanol em cerca de 17 %, considerando somente a fermentação das hexoses obtidas a partir da celulose do bagaço. A realização do processo de hidrólise leva a um aumento do consumo de energia do processo, que pode ser compensado pela otimização do processo convencional de produção .de etanol a partir do caldo da cana-de-açúcar, do aproveitamento da palha e de subprodutos do processo de hidrólise como a lignina, e da integração térmica do processo integrado, que utiliza caldo e bagaço como matéria prima para produção de etanol. O equacionamento do consumo energético da produção integrada de etanol a partir da cana-de-açúcar e do bagaço de cana-de-açúcar constitui um obstáculo à viabilização técnica e econômica do processo de hidrólise. Este trabalho visa apresentar então colaborações no sentido de superar este obstáculo, considerando-se a produção de etanol a partir do bagaço de cana-de-açúcar por meio de um processo de hidrólise do tipo Organosolv com ácido diluídoAbstract: The main objective of this dissertation is to present the description and simulation of bioethanol production processes from sugarcane juice and bagasse, considering the evaluation of energy consumption. Some improvements were considered for the conventional bioethanol production process from sugarcane juice, such as efficient juice treatment, sterilization and concentration, lower fermentation temperatures (28°C) than the ones used nowadays in the industry, study of a double effect distillation sys tem and optimization of dehydration processes for anhydrous bioethanol production. The process considered for bioethanol production from sugarcane bagasse is based on an Organosolv process with dilute acid hydrolysis, carried on three non-simultaneous steps: prehydrolysis of hemicellulose, Organosolv delignification and cellulose hydrolysis. The use of 70 % of sugarcane bagasse generated on the mills as raw material for the hydrolysis process allows an increase in bioethanol production of 17 %, considering exclusively the fermentation of the hexose obtained from the cellulose fraction of sugarcane bagasse. An increase on energy consumption is observed when bagasse is used as raw material in the hydrolysis process, but it may become feasible considering the optimization of conventional bioetlJ.anol production process, the use of sugarcane trash and lignin as fuel in boilers and the thermal integration of the integrated process, which uses sugarcane juice and bagasse as raw materiaIs for bioethanol production. Evaluation of the energy consumption of the integrated production of ethanol from sugarcane and sugarcane bagasse constitutes an obstacle for the technical and economical feasibility of the hydrolysis processo This work aims to present contributions to help surpass this obstacle, considering the production of ethanol from sugarcane bagasse using an Organosolv process with dilute acid hydrolysisMestradoDesenvolvimento de Processos QuímicosMestre em Engenharia Químic