Dissertations / Theses on the topic 'Batch distillation column'

J'ai étudié deux nouvelles configurations de double-colonne pour distillation hétéroazéotropique. Ces configurations sont appropriées à la récupération simultanée des composants des mélanges binaires hétéroazéotropiques et homoazéotropiques (en utilisant un tiers corps (entraîneur)). Elle sont opérées en système fermé, c'est-à-dire, il n'y a pas de soutirage de produit continu. D'abord, en appliquant un modèle simplifié, j'ai étudié la faisabilité de la séparation d'un mélange hétéroazéotropique (1-butanol – eau), puis celle d'un mélange homoazéotropique (2-propanol – eau) aidé par entraîneur benzène ou cyclohexane, en utilisant le SDC. Puis, j'ai étudié cette configuration par modélisation rigoureuse, en appliquant le simulateur dynamique du logiciel professionnel ChemCAD (CC-DColumn). J'ai comparé la nouvelle configuration avec le RD, sur la base des résultats obtenus par toutes les deux méthodes d'étude. Le SDC s'est avéré faisable et compétitif avec le RD : pendant la même durée ou plus courte, les rendements des composants ont été plus élevés. Puis, on a étendu le SDC à un système plus flexible (système de double-colonne généralisé, SDCG) qui est approprié à la séparation des mélanges binaires homoazéotropiques aidé par entraîneur (en le cas présent : cyclohexane ou n-hexane). J'ai étendu la méthode de faisabilité aussi à l'étude de cette configuration. Le SDCG s'est avéré aussi faisable. En appliquant modélisation rigoureuse, j'ai étudié les effets des nouveaux paramètres opératoires sur la durée, et j'ai comparé le DCG avec le SDC. Le SDCG s'est avéré encore plus avantageux que le SDC : la durée a été plus courte, et les besoins spécifiques d'énergie des produits ont été plus bas. J'ai étudié le SDC et le SDCG aussi par des manipulations exécutées sur installations de taille laboratoire et pilote. D'abord, j'ai fait des manipulations laboratoires pour la séparation du mélange binaire hétéroazéotropique, en utilisant une installation en verre qui a été opérée aussi comme RD et SDC. Le SDC s'est avéré faisable et compétitif avec le RD aussi sur la base des résultats de ces manipulations : pendant la même durée, les rendements des tous les deux composants ont été plus élevés. Puis, en utilisant l'installation pilote comme SDC, j'ai étudié la séparation ci-dessus. Après cette manipulation, j'ai étudié la séparation du mélange binaire homoazéotropique en appliquant n-hexane comme entraîneur, en opérant le système comme RD et SDCG. La manipulation faite avec le SDCG a montré que la production simultanée de deux composants est faisable avec cette configuration
Distillation is the method the most frequently applied for the separation of liquid mixtures, e.g. for the recovery of the components of the waste solvent mixtures. Because of the high energy demand of these processes the optimal design and operation of the distillation equipments are important from economic and also environmental points of view. The separation of the azeotropic mixtures needs special distillation methods like heteroazeotropic distillation. In the pharmaceutical and fine chemical industries it is often applied in batch mode. The aims of the thesis are to study the feasibility of a new Double-Column System (DCS) for batch heteroazeotropic distillation and to compare it with the traditional Batch Rectifier (BR) equipped with a decanterto study the above configurations by rigorous simulationto extend the DCS (Generalised Double-Column System, GDCS) and to study this new configuration by the above methodsto do laboratory experiments for both configurations in order to prove the feasibility of the separation and validate the calculations, respectively. Two new double-column configurations for batch heteroazeotropic distillation were studied. These configurations are designed to produce simultaneously the components of binary heteroazeotropic and homoazeotropic mixtures (by using an entrainer). They are operated in closed system (without continuous product withdrawal). First the feasibility of the separation of a heteroazeotropic mixture (1-butanol – water) and that of a homoazeotropic one by using an entrainer (isopropanol – water + benzene or cyclohexane) in the DCS were investigated by a simplified model. Then the operation of this configuration was modelled by rigorous simulation by using the dynamic simulator of the professional flowsheet simulator ChemCAD (CC-DColumn). On the basis of the results obtained by both methods the new configuration was compared with the BR. The DCS proved to be feasible and competitive with the BR: during the same or shorter time the recoveries of the components were higher. Then the DCS was extended to a more flexible version (Generalised Double-Column System, GDCS), which is suitable for the separation of binary homoazeotropic mixtures (by using an entrainer, in this work: cyclohexane or n- exane). The feasibility method was extended for the study of this configuration, as well. The GDCS proved to be feasible. Then the effects of its additional operational parameters on the duration were studied by rigorous simulation. The GDCS was compared with the DCS by rigorous simulation, as well. The GDCS proved to be more advantageous than the DCS: the duration was shorter and the specific energy demands of the products were lower. The DCS and GDCS were also investigated by laboratory and pilot plant experiments. First laboratory experiments were done for the separation of the binary heteroazeotropic mixture in a simple small size glass equipment operated as BR and DCS. The DCS proved to be feasible and competitive with the BR also on the basis of the results of these experiments: during the same time the recovery of both components were higher. Then a pilot plant was used for the same separation as a DCS. After this experiment the separation of the binary homoazeotropic mixture by using n-hexane as entrainer was studied in the equipment operated as BR and GDCS. The experiment showed that the simultaneous production of two components is feasible also in the GDCS

In the control of batch and continuous distillation columns, one of the most challenging problem is the difficulty in measuring compositions. This problem can be handled by estimating the compositions from readily available online temperature measurements using a state observer. The aim of this study is to design a state observer that estimates the product composition in a multicomponent batch distillation column (MBDC) from the temperature measurements and to test this observer using a batch column simulation. To achieve this, first a model for MBDC is prepared and compared with the data from literature where a case column is utilized. After checking the validity of the simulation package, it is used as a fictitious process for the performance evaluations. In the second phase of the study, an extended Kalman Filter (EKF) is designed by utilizing a simplified model of MBDC and it is implemented for performance investigation on the case column with 8 trays separating the mixture of cyclohexane, n-heptane and toluene. The simplified model utilized in EKF results in response, which have some deviation with rigorous model, mainly due to the simplification of vapor-liquid equilibrium relationship. In the performance evaluation, the tuning parameters of EKF
the diagonal terms of process noise covariance matrix and the diagonal terms of measurement model noise covariance matrix are changed in the range of 50¡
1x10¡
7 and 0:5¡
5x108 and the optimum values are found as 0:00001 and 5000, respectively. The effect of number of measurement points is also investigated with a result of number of component measurements. The effect of measurement period value is also studied and found that it has a major effect on the performance which has to be determined by the available computational facilities. The control of the column is done by utilizing the designed EKF estimator and the estimator is successfully used in controlling the product purities in MBDC under variable reflux-ratio operation.

Modeling and inferential control studies are carried out on a reactive batch distillation system for the esterification reaction of ethanol with acetic acid to produce ethyl acetate. A dynamic model is developed based on a previous study done on a batch distillation column. The column is modified for a reactive system where Artificial Neural Network Estimator is used instead of Extended Kalman Filter for the estimation of compositions of polar compounds for control purposes. The results of the developed dynamic model of the column is verified theoretically with the results of a similar study. Also, in order to check the model experimentally, a lab scale column (40 cm height, 5 cm inner diameter with 8 trays) is used and it is found that experimental data is not in good agreement with the models&rsquo
. Therefore, the model developed is improved by using different rate expressions and thermodynamic models (fi-fi, combination of equations of state (EOS) and excess Gibbs free energy (EOS-Gex), gama-fi) with different equations of states (Peng Robinson (PR) / Peng Robinson - Stryjek-Vera (PRSV)), mixing rules (van der Waals / Huron Vidal (HV) / Huron Vidal Original (HVO) / Orbey Sandler Modification of HVO (HVOS)) and activity coefficient models (NRTL / Wilson / UNIQUAC). The gama-fi method with PR-EOS together with van der Waals mixing rule and NRTL activity coefficient model is selected as the best relationships which fits the experimental data. The thermodynamic models
EOS, mixing rules and activity coefficient models, all are found to have very crucial roles in modeling studies. A nonlinear optimization problem is also carried out to find the optimal operation of the distillation column for an optimal reflux ratio profile where the maximization of the capacity factor is selected as the objective function. In control studies, to operate the distillation system with the optimal reflux ratio profile, a control system is designed with an Artificial Neural Network (ANN) Estimator which is used to predict the product composition values of the system from temperature measurements. The network used is an Elman network with two hidden layers. The performance of the designed network is tested first in open-loop and then in closed-loop in a feedback inferential control algorithm. It is found that, the control of the product compositions with the help of an ANN estimator with error refinement can be done considering optimal reflux ratio profile.

During the last decades, batch distillation is preferably used with an increasing demand over continuous one, to separate fine chemicals in chemical and petroleum industries, due to its advantages like, flexibility and high product purity. Consequently, packed distillation columns, with newly generated packing materials, are advantageous compared to plate columns because of their smaller holdups, resistivity to corrosive materials and their higher separation efficiencies. Also, in many industrial applications, mathematical models of distillation systems are frequently used in order to design effective control systems, to train operating personnel and to handle fault diagnostics. Thus, the main objective of this study is to develop a mathematical model for a multicomponent batch distillation column, which is used to separate mixtures at low operating pressures, packed with random packing materials. In multicomponent batch packed distillation, operation with optimum reflux ratio profile is important for efficiency to maximize the amount of the distillate with a specified concentration, for a given time. Therefore, it is also aimed to find the optimum reflux ratio profile for the multicomponent batch packed distillation column. A simulation algorithm is written with the aid of MATLAB and FORTRAN programming languages by taking into account pressure drop and variation of physical properties. The selected incremental bed height, &
#916
z, to be used in the simulation program has an effect on the accuracy of the results. This is analyzed and the optimal incremental height is found to be 3.5 cm for a 1.5m bed height. The change in distillate compositions with a given constant reflux ratio is found to be similar with those of previous studies. The simulation code is also used to obtain responses in distillate compositions for different reflux ratios, condenser holdups and reboiler duties and compared with similar studies found from literature and found to be adequate. Finally, experiments are conducted to verify simulation algorithm by using a lab-scale packed distillation column for the separation of a polar mixture of ethanol and water. It is observed that, there is a good agreement between the experimental and simulation results. After the verification of dynamic model, optimum operation policy to maximize product amount is investigated numerically by using capacity factor approach. The column is operated with and without recycling of the holdups of the slop cut tanks, in order to examine the effect of recycling on capacity factor, CAP. It is observed that, recycling of the molar holdups of the slop cut tanks is resulted in a 28% increase in the separation efficiency.

The increasing trend of world-wide energy consumption emphasizes the importance of ongoing optimization of new and existing technologies. In this dissertation, two energy–intensive systems are simulated and optimized. Advanced estimation, optimization, and control techniques such as a moving horizon estimator and a model predictive controller are developed to enhance the profitability, product quality, and reliability of the systems. An enabling development is presented for the solution of complex dynamic optimization problems. The strategy involves an initialization approach to large–scale system models that both enhance the computational performance as well as the ability of the solver to converge to an optimal solution. One particular application of this approach is the modeling and optimization of a batch distillation column. For estimation of unknown parameters, an L1-norm method is utilized that is less sensitive to outliers than a squared error objective. The results obtained from the simple model match the experimental data and model prediction for a more rigorous model. A nonlinear statistical analysis and a sensitivity analysis are also implemented to verify the reliability of the estimated parameters. The reduced–order model developed for the batch distillation column is computationally fast and reasonably accurate and is applicable for real time control and online optimization purposes. Similar to estimation, an L1-norm objective function is applied for optimization of the column operation. Application of an L1-norm permits explicit prioritization of the multi–objective problems and adds only linear terms to the problem. Dynamic optimization of the column results in a 14% increase in the methanol product obtained from the column with 99% purity. In a second application of the methodology, the results obtained from optimization of the hybrid system of a cryogenic carbon capture (CCC) and power generation units are presented. Cryogenic carbon capture is a novel technology for CO2 removal from power generation units and has superior features such as low energy consumption, large–scale energy storage, and fast response to fluctuations in electricity demand. Grid–level energy storage of the CCC process enables 100% utilization of renewable power sources while 99% of the CO2 produced from fossil–fueled power plants is captured. In addition, energy demand of the CCC process is effectively managed by deploying the energy storage capability of this process. By exploiting time–of–day pricing, the profit obtained from dynamic optimization of this hybrid energy system offsets a significant fraction of the cost of construction of the cryogenic carbon capture plant.

La tesis doctoral se compone de dos partes fundamentales: El desarrollo teórico de un modelo de simulación para la destilación discontinua y la validación de este mediante experimentos hechos en una planta piloto de destilación discontinua.
La parte teórica se divide en la parte de desarrollo del modelo y en la parte de la implementación del modelo en un programa de simulación. El nuevo modelo desarrollado es un modelo de transferencia de materia que se distingue de los desarrollos anteriores por su capacidad de contemplar la cinética de la transferencia de materia tal como la hidrodinámica. La incorporación de efectos hidrodinámicos se basa principalmente en la observación de diferentes geometrías de contacto en una columna de platos perforados. Estas geometrías de contacto son canales de vapor y burbujas. En caso de las burbujas se distingue entre grandes y pequeñas con diferentes propiedades hidrodinámicas. De esta forma el modelo contempla tres diferentes clases de vapor, dos clases de vapor de desequilibrio y una de equilibrio (burbujas pequeñas). Para las clases de vapor de desequilibrio se calcula explícitamente los caudales de materia que traviesen la interfase basándose en la teoría de Maxwell-Stefan de transferencia de materia multicomponente.
La parte experimental se divide en la parte de diseño de la columna usada en una planta piloto y en la de la realización de los experimentos. El diseño de la columna tiene como objetivo la obtención de un medio de validación del nuevo modelo desarrollado. Por tanto está equipado con un gran número de sensores de temperatura, de presión y de tomas de muestra. También la realización de los experimentos se adapta al fin de la validación del modelo, ya que la frecuencia de toma de muestra y de capturación de señales de temperatura es elevada.
La memoria de la tesis contiene una comparación amplia de los resultados experimentales con los de la simulación. Estas comparaciones demuestran una determinada superioridad del modelo desarrollado sobre desarrollos anteriores.

The synthesis of a number of alkyl esters such as methyl lactate, methyl decanoate, and ethyl benzoate via esterification in a reactive distillation is quite challenging. It is due to the complexity in the thermodynamic behaviour of the chemical species in the reaction mixture in addition to the difficulty of keeping the reactants together in the reaction section. One of the reactants (in these esterification reactions) having the lowest boiling point can separate from the other reactant as the distillation continues. This can result in a significant drop in the reaction conversion in a conventional reactive distillation whether it is a batch or a continuous column. To overcome this challenge, new different types of batch reactive distillation column configurations: (1) integrated conventional (2) semi-batch (3) integrated semi-batch (4) integrated dividing-wall batch distillation columns have been proposed here. Four esterification reaction schemes such as (a) esterification of lactic acid (b) esterification of decanoic acid (c) esterification of benzoic acid (d) esterification of acetic acid are investigated here. A detailed dynamic model based on mass, energy balances, chemical reaction, and rigorous thermodynamic (chemical and physical) properties is considered and incorporated in the optimisation framework within gPROMS (general PROcess Modelling System) software. It is found that for the methyl lactate system, the i-SBD operation outperforms the classical batch operations (CBD or SBD columns) to satisfy the product constraints. While, for the methyl decanoate system, the i-DWCBD operation outperforms all CBD, DWBD and sr-DWBD configurations by achieving the higher reaction conversion and the maximum product purity. For the ethyl benzoate system, the performance of i-CBD column is superior to the CBD process in terms of product quality, and conversion rate of acid. The CBD process is found to be a more attractive in terms of operating time saving, and annual profit improvement compared to the IBD, and MVD processes for the benzyl acetate system.
The Higher Committee for Education Development in Iraq (HCED)

ABSTRACT One of the most important tasks in the chemical industry is the separation of multicomponent liquid mixtures into one or more high-purity products. Several technologies are feasible for this task, either alone or in combination, such as distillation, extraction, crystallization, ect. Among these, distillation is by far the most widely spread and has a long history in chemical technology. However, until recently, there has been no systematic approach for understanding the separation of complex mixtures where azeotropes and multiple liquid phases may occur. There has been a growing interest in the use of residue curve and column profiles for the preliminary design of distillation columns. Residue curves and column profile are not only used to predict the composition changes in the distillation column but also to determine the feasibility of the proposed separation. Recently, theory underlying column profile maps has been developed by Tapp, Holland and co-workers. However there has been no direct experimental validation of the predictions of the column profile map theory. The main aim of this thesis is to experimentally verify some of the predictions of column profile map theory. A simple experimental batch apparatus has been developed to measure residue curve maps (RCMs) by Tapp and co-workers, the apparatus was modified so that it could be used to measure column profile maps (CPMs) in this thesis. CPM theory has shown that CPMs are linear transforms of the residues curve maps (RCMs). A stable node which was the apex of a mass balance triangle (MBT) was introduced inside the MBT, this was done by transforming the RCMs to CPMs using the appropriate distillate composition xd and reflux ratio R. It was also shown that the saddle point which was on the boundary of the triangle of the RCM can be shifted inside the MBT by transforming the RCM to CPM. This is again in accordance with theoretical predictions of CPM theory. iv Residue curves (RCs) and pinch point curves (PPCs) are used to determine the operation leaves and hence the feasible region for distillation columns operating at a specific distillate and bottoms composition for all fixed reflux ratio. The operating leaves were expanded beyond the pinch point curve by varying the reflux ratio from a higher reflux to a lower reflux ratio. This showed that one can effectively cross the pinch point curve hence expanding the operating leave. Finally the importance of experimentally measuring CPMs is demonstrated. Two thermodynamic models were used to predict the profiles of a complex system. The binary vapor-liquid equilibrium (VLE) diagrams and the residue curves produced from using these two thermodynamic models did not predict the same topology. The composition of the profiles were not the same because there were multiple liquid phases involved in this system, which made it difficult for the researchers to measure the correct profiles. Column profile maps were simulated using the different thermodynamic models, they also showed that there is some discrepancy between the predictions of the two models.

碩士
國立臺北科技大學
化學工程研究所
101
Batch Distillation is an important process in chemical industry. Batch distillation is often used to produce small amounts of products with high added value. Most of textbooks focus on the steady state. However, the dynamics operation is more important. 　　The research developed a windows program for binary batch distillation column under atmospheric pressure by Visual Basic 2010. The subprograms for solving the mass balance, energy balance and phase equilibrium equations were constructed firstly. Three strategies for operating the distillate flow rate were applied in the program. By simulation examples, different operation strategies have the different optimal control conditions; the program can apply the capability for user to learn the dynamic operations of batch distillation.

碩士
東海大學
化學工程學系
91
Industrial interest in batch distillation has increased significantly in recent years as more batch processing is being used for low-volume specialty chemicals. Most studies in the literature have concentrated on the determination of optimum operation strategies, e.g., optimum trajectories of reflux ratio and pressure during the batch and processing of the slop cuts that are produced. Little attention has been paid to problems associated with control. In fact, one of the main difficulties in batch distillation process control is getting reliable and accurate measurement of product compositions. If instantaneous and perfect analyzers were available, the task of batch distillation control would be straightforward once the optimum policies are available. Although composition analyzers, like on-line gas chromatography (on-line GC), have been used in the process industries for a long time, they are normally not so suitable for batch distillation processes. Moreover, the most important drawback for using the on-line GC in controlling a batch distillation process is that it possesses a very large time delay and thereby lowers the achievable control performance. The use of inferential variables, say temperatures, to estimate process compositions in place of direct on-line measurements is usually desired for plant engineers. However, the batch distillation process has been known as a highly nonlinear, dynamic system; it is more complex and difficult to predict real-time compositions through temperature measurements. On the other hand, the artificial neural networks (ANN) with the ability to evolve a good process model from experimental data requires very little or no knowledge of first principles. It has the ability of learning and prediction for nonlinear model, and has therefore been used to identify the process dynamics nonparametrically. The primary object of this investigation, however, is to develop an ANN composition estimator of a batch distillation column from temperature measurements. Then, using this estimator to implement an inferential control on the column. Simulation results in a batch distillation column have demonstrated that the proposed inferential control technique using recurrent and stack ANN can performance better than that of the classic operation.

碩士
國立臺北科技大學
化學工程研究所
98
Entrainer was added to a distillation column to increase the relative volatility of mixtures, and then the mixtures can be separated by normal distillation. This research developed a windows simulation program of batch extract distillation column which water was used as the entertainer to separate acetone and methanol. By changing reboiler duty, flow rate of entrainer, reflux ratio, learner can study the optimal operation of batch extractive distillation. This research was to develop program with solving the mass balance, energy balance and phase equilibrium equations of the different operation units and then construct them to be a series of subroutine models. Visual Basic was used to develop the operating interface. By virtue of this simulation results, the steady state value of simulation program is similar by calculated. The dynamic response is also reasonable, therefore this simulation program can be provided for further studies and research of control strategy.

Yes
Although batch reactive distillation process outperforms traditional reactor-distillation processes due to simultaneous reaction and separation of products for many reaction systems, synthesis of Methyl lactate (ML) through esterification of lactic acid (LA) with methanol in such process is very challenging due to difficulty of keeping the reactants together when one of the reactants (in this case methanol) has the lowest boiling point than the reaction products. To overcome this challenge, two novel reactive distillation column configurations are proposed in this work and are investigated in detail. These are: (1) integrated conventional batch distillation column (i-CBD) with recycled methanol and (2) integrated semi-batch and conventional batch distillation columns (i-SBD) with methanol recovery and recycle. Performances of each of these configurations are evaluated in terms of profitability for a defined separation task. In i-SBD column, an additional constraint is included to avoid overflow of the reboiler due to continuous feeding of methanol into the reboiler as the reboiler is initially charged to its maximum capacity. This study clearly indicates that both integrated column configurations outperform the traditional column configurations (batch or semi-batch) in terms of batch time, energy consumption, conversion of LA to ML, and the achievable profit.

No
Comparison of optimal operation between conventional batch reactive distillation column (CBRD) and middle-vessel batch reactive column (MVBRD) for the production of lactic acid via hydrolysis of methyl lactate has not been considered in the past. Therefore, it is the main focus in this work. A dynamic optimization problem incorporating a process model is formulated to minimize the batch time subject to constraints on the amount and purity of lactic acid. Control variables (reflux ratio or/and a reboil ratio) are treated as a piecewise constant. Optimization results indicate that MVBRD is more effective than CBRD in terms of saving in batch time which can be as high as of 20 %.

Yes
The synthesis of ethyl benzoate (EtBZ) via esterification of benzoic acid (BeZ) with ethanol in a reactive distillation is challenging due to complex thermodynamic behaviour of the chemical reaction and the difficulty of keeping the reactants together in the reaction zone (ethanol having the lowest boiling point can separate from the BeZ as the distillation proceeds) causing a significant decrease in the conversion of BeZ in a conventional reactive distillation column (batch or continuous). This might be the reason of not reporting the use of reactive distillation for EtBZ synthesis although the study of BeZ esterification reaction is available in the public literature. Our recently developed Integrated Conventional Batch Distillation (i-CBD) column offers the prospect of revisiting such reactions for the synthesis of EtBZ, which is the focus of this work. Clearly, i-CBD column outperforms the Conventional Batch Distillation (CBD) column in terms of product amount, purity and conversion of BeZ and eliminates the requirement of excess use of ethanol. For example, compared with CBD column, the i-CBD operation can yield EtBZ at a much higher purity (0.925 compared to 0.730) and can convert more benzoic acid (93.57% as opposed to only 74.38%).

Yes
In this work, for the first time, the synthesis of benzyl acetate via the esterification of acetic acid and benzyl alcohol is investigated in the reactive distillation system using a middle vessel (MVD), inverted (IBD), and conventional batch reactive distillation columns. The measurement of the performance of these column schemes is determined in terms of profitability through minimization of the batch time for a defined separation task. The control variables (reboil ratio for MVD, IBD columns) and (reflux ratio in case of CBD column) are considered as piecewise constants over batch time. The optimization results obviously indicate that the CBD system is a more attractive process in terms of batch time reduction, and maximum achievable yearly profit as compared to the MVD, and IBD operations.