Batch Distillation Column Research Articles

Short-Cut Design Procedure for Batch Distillations

This paper presents a short-cut procedure for the design of batch distillations which is equivalent to the Fenske−Underwood−Gilliland procedure for continuous distillations. Given a separation task, we propose computing the minimum number of stages and minimum reflux ratio required to perform it by batch distillation. These parameters are quite different from the continuous Nmin and Rmin parameters for the same separation task, because of the difference in the form of the material balances (steady state in continuous but integrated differential mass balances in the batch case). We propose that they should be computed as the number of stages and reflux ratio required by hypothetical batch distillation columns that operate at total reflux or have an infinite number of stages, respectively. Then, it is shown that the performance of batch distillations does correlate in Gilliland coordinates constructed with these batch Nmin and Rmin. This produces a quite simple, straightforward method to do preliminary design of batch distillations.

Applying risk assessment principles to a batch distillation column

AbstractSome distillation columns in the chemical industry are operated in batch mode with a fairly short operating cycle. At the end of each cycle the columns are cooled and recharged. During the cooling cycle, air will be drawn into the column by the action of a vacuum relief valve. Consequently, for a finite portion of the operating cycle a flammable mixture will exist in the column.Here we evaluate the risk posed by such an operation to see if a mitigation measure is justified. We develop a fault tree and estimate the frequency of ignition by all possible ignition sources. By comparing the risk reduction attainable by installing a lightning protection system with that attainable by using an inert blanketing system the lightning protection system is found to be the preferred solution. It provides about the same risk reduction at a lower overall cost.

Simultaneous optimization of design and operation of multicomponent batch distillation column—single and multiple separation duties

A method is presented for the simultaneous optimization of a batch distillation column design and its operation, for single and multiple separation duties, each involving different multicomponent mixtures and complex operations with intermediate cuts. For operation structures selected a priori, the formulation presented permits the use of general distillation design and cost models. The objective function and constraints include capital and operating cost. In particular, the number of internal plates is optimized along with the most significant operating variables (recoveries in various cuts and reflux ratio profiles and times). The multiple duty formulation presented accounts for the different importance of each duty and setup time between batches. Application of the method to single duty multicomponent separation from the literature shows that significant profit improvements can be achieved within acceptable computing times. For multiple separation duties (two binary mixtures), the method clearly shows the importance of including allocation time to each duty and setup time for each batch in the objective function.

Simultaneous Separation of Light and Heavy Impurities by a Complex Batch Distillation Column.

The characteristics of a new type of batch distillation column called the “complex batch distillation column” are examined. In the complex column, the feed is supplied to the middle of the column, and the light and heavy components are withdrawn from the top and the bottom at the same time. The liquid on the feed tray is recycled to the feed tank so as to accumulate the intermediate component in the tank. The complex column is convenient for removing light and heavy impurities from raw materials since the impurities can be withdrawn simultaneously from the top and the bottom. The complex column is similar to a combined system of ordinary and stripping batch distillation columns where the condenser of the stripping column is heat-integrated with the reboiler of the ordinary column. Therefore, it can be expected that separation can be executed effectively compared with the ordinary column. In this paper, by analyzing the differences between ordinary and stripping batch distillation columns, the conditions at which the complex column works effectively compared with an ordinary batch distillation column, are clarified.

Acetalization of Formaldehyde with Methanol in Batch and Continuous Reactive Distillation Columns

Methylal, an important raw material and a solvent, is produced by acetalization of aqueous formaldehyde with methanol. This acetalization reaction was carried out in a closed system in the presence of a cation-exchange resin Indion 130 as catalyst and was found to be equilibrium limited. In order to increase the conversion for this reaction, reactive distillation was carried. Batch reactive distillation was performed in the presence of the cation-exchange resin Indion 130 as catalyst. Continuous reactive distillation was performed in a reactive distillation column (RDC) using three different types of catalyst packing. The first type of catalyst packing was coarse size macroporous cation-exchange resin Indion 130, which was directly packed along with Raschig rings. The second type of catalyst packing was Indion 130 tied in cloth bags. The third type of catalyst packing used was a silica-supported organic catalyst. Up to 99% conversion of formaldehyde was achieved by reactive distillation. Vapor−liquid equi...

Optimal startup procedures for batch distillation

Operation of a conventional batch distillation column can be conveniently described in three parts: 1) startup period, 2) production period and 3) shutdown period. For standard separation processes, the production period is the most time consuming. However, for difficult separations, such as for high purity or azeotropic separations, the startup time may also be significant. In this paper, we present results for optimal operation of a number of different separations taking the startup time into consideration. It is generally found that the startup time is significant compared to the total operating time for difficult separations (high purities and recoveries) and when the combined column and condenser holdup is large. It is also found that the exact value of the startup time is of limited significance unless it is very different from the optimal value. Alternative ways of reducing the duration of the startup period are discussed.

Understanding batch distillation process principles with MultiBatchDS

This article describes the MultiBatch Distillation Systems MultiBatchDS for simulation, optimal design, and control of batch distillation columns with multiple configurations, multiple operating modes, and multiple fractions with multiple levels of models. The use of this package as a teaching aid for explaining batch distillation fundamentals is presented. © 1996 John Wiley & Sons, Inc.

Some issues in the design and operation of a batch distillation column with a middle vessel

Some issues in the design and operation of a batch distillation column with a middle vessel are addressed. Simulation results indicate that operation at infinite reflux and reboil ratios may be more profitable than conventionally considered finite reflux and reboil ratios policies. From an experimental point of view, the possibility of running a pre-existing continuous pilot plant column in a complex batch mode is investigated. Practical suggestions for column design and process control are given.

Robust design using an efficient sampling technique

The concept of robust design involves identification of design settings that make the product performance less sensitive to the effects of seasonal and environmental variations. Batch processes are more flexible compared to continuous processes and are frequently used in these situations. Stochastic optimization methods provide a general approach to robust/ parameter design as compared to conventional techniques. However, the computational burden of these approaches can be extreme and depends on the sample size used for characterizing the parametric variations and uncertainties. In this paper, we present a novel sampling technique. The example of robust batch distillation column design illustrates that the new sampling technique offers significant computational savings and better accuracy.

Understanding batch distillation process principles with MultiBatchDS

This article describes the MultiBatch Distillation Systems (MultiBatchDS) for simulation, optimal design, and control of batch distillation columns with multiple configurations, multiple operating modes, and multiple fractions with multiple levels of models. The use of this package as a teaching aid for explaining batch distillation fundamentals is presented. © 1996 John Wiley & Sons, Inc.

Design and Operation of a Batch Distillation Column with a Middle Vessel

Design and Operation of a Batch Distillation Column with a Middle Vessel

Comparison of Inverted and Regular Batch Distillation

Several alternative strategies have been suggested to increase the productivity of batch distillation columns. One is the use of inverted columns where the feed is charged to the condenser drum instead of to the reboiler. We find that an inverted column is best for separations with small amounts of light component in the feed. The reason is that it takes a long time to move this small amount from the reboiler to the top before removal when a regular column is used. The regular and the inverted column are found not to be mirror images of each other. This is because the inverted column considered in this study isnotthe true inverse of the regular column since the feed and product are in liquid phase. The ideal inverted column with feed in vapor phase is briefly discussed.

ALAMBIC - A Software Package for Optimising Design and Operation of Batch Distillation Columns

ALAMBIC is a window based, interactive and easy-to-use software package developed for optimising the design and operation of batch distillation columns. Its features are highlighted. The package permits the solution of a wide range of problems encountered in multicomponent and reactive batch distillation, including simulation and optimal operation of a given column, and simultaneous optimisation of design-operation, for single and multiple duties, utilising rigorous models. The problem definition is done interactively by editing menus and forms in multiple windows. Results are viewed in graphical form. A case management tool permits the easy solution of multiple problems. The use of the package is demonstrated by two examples from the literature.

Automation of a batch distillation column using fuzzy and conventional control

In this paper the automatic control of a batch-distillation column is described. This control is done both with fuzzy logic and with a combination of conventional linear and nonlinear control methods. After a short explanation of the function of a batch-distillation column, its operating strategy is described. This strategy is the starting point for developing both automation concepts. The realizations of both concepts are described, and measurements at the real plant are shown. Both concepts are compared with regard to the effort required in development and the quality of the operating results. This leads to the conclusion that both methods are equivalent. The plant can be automated by the conventional linear and nonlinear method with the same quality as by fuzzy logic, although this problem seems to be predestined for fuzzy logic because of its knowledge representation in linguistic form.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design and operation of a batch distillation column with a middle vessel

The paper examines a new type of a batch distillation column which is built up from two separation sections and a vessel in between. The behavior of the column is analyzed using the infinite separation and the minimum reflux models. A comparison of a batch rectifier, a batch stripper and a column with a middle vessel showed that the latter always performs better than conventional design. Using the minimum reflux model it is shown that operation at the steady state is the optimal control policy for the column with a middle vessel in the case of a binary separation.

Batch distillation in a column with a middle vessel

This paper examines a new type of a batch distillation column which is built up from two separation sections and a vessel in between. Mixtures with constant relative volatilities are investigated. One of the most important features of the new column is that it has additional steady states on binary edges of the simplex which do not correspond to pure components. These steady states are saddle and unstable singular points of a dynamic system describing the process. Existence of additional steady states, their dependence on parameters and the introduction of one more parameter q add more flexibility to the process and provide new opportunities for batch distillation. For example, a binary mixture can be separated into pure components under finite reboil and reflux ratio.

Simulation, design, and analysis of azeotropic distillation operations

The computational tools needed for simulation, design, and analysis of azeotropic distillation operations are described. These tools include simple methods to identify the existence of binary and ternary azeotropes and to classify ternary mixtures as homogeneous or heterogeneous. The tools also include more complex methods to compute the phase diagram (or a heterogeneous liquid boiling surface), predict liquid-vapor phase equilibrium, and/or predict liquid-liquid-vapor phase equilibrium for simulations of batch and continuous distillation column operations. Important new features of these tools are the incorporation of a fast and efficient method for test of phase stability in simulation of distillation operations, the ability to handle a large range of mixtures (including mixtures with supercritical compounds), and the ability for computations covering wide ranges of temperature and pressure. On the basis of these tools, simple and consistent design algorithms are developed. The applicability of the design algorithms is verified through process simulation and analysis of the predicted behavior and data from the open literature. Conditions are given for examples illustrating (when and how possible distillation boundaries can be crossed) how multiple steady states can be obtained. Finally, the effect of changes in operating on the dynamic behavior of the azeotropic distillation columns andmore » the sensitivity of design to the prediction of phase equilibria are presented.« less

Optimal design and operation of complex batch distillation column : S. Hasebe, B.B. Abdul Aziz, I. Hashimoto, T. Watanabe pp 177–182

Optimal design and operation of complex batch distillation column : S. Hasebe, B.B. Abdul Aziz, I. Hashimoto, T. Watanabe pp 177–182

Optimal Design and Operation of Complex Batch Distillation Column

Abstract A new type of batch distillation column called a “complex batch distillation column” is proposed, and the characteristics of this column are studied. In the complex “batch distillation column, the feed is supplied to the middle of the column, and the liquid on the feed tray is recycled to the feed tank. The complex column is convenient for removing light and heavy impurities from the raw materials since the impurities could be withdrawn simultaneously from the top and the bottom. In this research, the complex column is regarded as a combined system of ordinary and stripping batch distillation columns where the condenser of the stripping column is heat-integrated with the reboilerof the ordinary column. First, the differences between the ordinary and stripping columns are clarified analytically. By using this result, the conditions at which the complex column works effectively compared with the ordinary batch distillation column are clarified.

BATCH-DIST: A comprehensive package for simulation, design, optimization and optimal control of multicomponent, multifraction batch distillation columns

BATCH-DIST is a general-purpose simulation package for the design, simulation and optimization of multicomponent, multifraction batch distillation columns operating under different modes (constant reflux, variable reflux and optimal reflux policy). The package includes simulation models of varying degrees of complexity and rigor; efficient but simplified models (based on short-cut methods) for preliminary design and rapid analysis of column behavior, and rigorous models (based on solution of transient heat and mass balance differential equations) for verification and detailed column design. Besides simulation and design, BATCH-DIST can also accomplish optimization and optimal control of columns. Coded in Fortran 77, the package is flexible and user-friendly. BATCH-DIST has been extensively tested with benchmark cases involving binary and multicomponent systems, with nonideal behavior and in columns with appreciable holdup effects. Such test cases have clearly demonstrated that predictions of the simplified models in the package compare well with those of the rigorous models. This powerful and comprehensive package is expected to be computationally more efficient than existing packages.