Multicomponent Distillation Column Research Articles

СПОСОБ РАСЧЕТА ПРОСТОЙ МНОГОКОМПОНЕНТНОЙ РЕКТИФИКАЦИИ СПОСОБОМ ФЕНСКЕ-АНДЕРВУДА-ДЖИЛЛИЛЭНДА

An approach to calculating a multicomponent simple distillation column according to the Fensky-Underwood-Gilliland method is considered

Excel as an optimization tool applied to multicomponent distillation column sizing

The unit operation of distillation is a method of significant importance for industrial separation processes, as it enables the fractionation of a mixture based on the differences in volatility among its components. Considering that a typical initial mixture generally contains three or more products of interest, studies aimed at optimizing multicomponent distillation, although scarce in the literature, are increasingly imperative to ensure efficiency and reduce operational and energy costs associated with the process. Since sizing multicomponent distillation columns using the Fenske-Underwood and Gilliland (FUG) and Kirkbride methods involves extensive and complex calculations to obtain operational parameters, the objective of this study was to develop a computational method using Microsoft Excel® software to make them more practical and enhance the accuracy of the results obtained. The functionality of the developed spreadsheet was verified through the resolution of an example of application, both manually and electronically. In both cases, the results obtained were identical, but with significantly lower time consumption and probability of error by the electronic method, demonstrating its potential for use in academic and industrial settings.

Critique on spreadsheet for relaxation methods

This critique discusses the Excel spreadsheet developed by Gómez-Siurana and Font-Escamilla for the application of relaxation methods to solve a simple multicomponent distillation column.

Solution of the maximum distillate on a batch distillation column by a Pseudo-Newton method

This paper presents a new algorithm for the solution of the maximum distillate problem based on Pontryagin's maximum principle. Four cases of study were analyzed with the algorithm. The first case is a literature problem where the column uses twenty trays to distillate ten components, the second case is a binary mixture with no ideal behavior, the third case is a quaternary mixture, and the last case is a reactive mixture. In all cases, the desired purity was settled as a final constraint. The solution algorithm found the optimal control faster than results reported in literature concerning the CPU time.The batch distillation process is modeled by using a rigorous model with no constant volatility. The proposed algorithm uses the Hamiltonian function to reformulate the maximum distillate problem. Then, the optimal control is solved by a Broyden–Fletcher–Goldfarb–Shanno algorithm. The solution procedure of the indirect approach required the forward integration of the states, the integration of the co-state equations backward in time, and the control input is the distillate flow rate which is parameterized. The binary batch distillation column uses six stages, and the maximum recovery is 95% of the light component with a 95% mol percent on the accumulator. The multicomponent batch distillation column uses 17 stages, and the recovery of the lightest component in the product is 90% mol percent. The reactive case reached 80% conversion.

Optimal Sequencing of Multicomponent Distillation Columns by Rigorous Calculation Methods

Optimal Sequencing of Multicomponent Distillation Columns by Rigorous Calculation Methods

A REVIEW OF THERMODYNAMIC ANALYSIS OF DISTILLATIONCOLUMN

Separation technique with distillation column is an energy intensive process even though it is one of the most extensively used separation process in the petrochemical, chemical and agro-allied industries. Studies have proved that some other schemes of distillation columns other than the conventional columns could be more energy efficient. This has led to a number of different configurations of the columns. This study presents a review of second law of thermodynamics in determining and enhancing the effectiveness of energy usage in the distillation columns. The review covers binary, multicomponent and crude distillation columns and it is not limited to the conventional columns. It can be concluded that exergy analysis of the columns while providing a true analysis of the column efficiency can be used to improve the column’s energy efficiency. It is therefore imperative that process engineers should be armed with this tool to design and operate energy efficient columns. Keywords: Distillation, Exergy analysis, Efficiency, Thermodynamics.

Nonlinear model predictive control of ultra-high-purity air separation units using transient wave propagation model

Model reduction techniques can be used to reduce the computational burden associated with nonlinear model predictive control (NMPC). In our recent work, we introduced the transient nonlinear wave propagation model (TWPM) for reduced dynamic modeling of multi-component distillation columns with variable holdup, and demonstrated its suitability for optimization and control of single-section distillation columns and simple air separation units [Caspari et al., J. Process Control, 2020]. We show here that the TWPM is well-suited for reduced modeling of multi-sectional ultra-high-purity distillation columns and enables real-time capable NMPC of complex process flowsheets with tight operational constraints. To demonstrate its performance and accuracy, we apply the TWPM for NMPC of an ultra-high-purity nitrogen air separation unit. We perform an in-silico closed-loop case study comprising a series of load changes. Our approach reduces CPU time by 84%, enabling NMPC in real time.

Development of a computational tool for designing multicomponent distillation columns

AbstractThe present paper aims to develop new software to simulate multicomponent distillation columns. AmProS software can help students and professionals with different areas of expertise (e.g., chemistry, and chemical, mechanical, and food engineers) to solve and understand distillation and thermodynamics problems with critical thinking. A database of 113 hydrocarbon compounds was created to make the software use more dynamic. This user‐friendly software was developed using the “V model” methodology and Visual Basic language to carry out the design and establish the operation parameters of distillation columns. The user can choose between two preprogrammed equations of state (Peng–Robinson or Soave–Redlich–Kwong) for the calculation of thermodynamic properties. Two approaches were integrated in specific modules considering Shortcut and Rigorous distillation methods obtaining good accuracy (<10%) compared to the commercial simulator. Each module shows the key equations and message logs that guide the user through the software. The results of the input parameters' effects (key components, temperature, pressure, and feed composition) in the design and rating column are shown in Excel table formats (.xlsm) as well as in pdf files. This software was applied in different courses at School of Chemical Engineering at University of Campinas for user acceptance testing. These tests showed that AmProS is intuitive, information can be effortlessly found and it is easy to use to solve complex simulations. Chemical engineering students (undergraduates and graduates) and professionals in different fields can use this tool to expand their knowledge.

A wave propagation approach for reduced dynamic modeling of distillation columns: Optimization and control

Reduced models enable real-time optimization of large-scale processes. We propose a reduced model of distillation columns based on multicomponent nonlinear wave propagation (Kienle 2000). We use a nonlinear wave equation in dynamic mass and energy balances. We thus combine the ideas of compartment modeling and wave propagation. In contrast to existing reduced column models based on nonlinear wave propagation, our model deploys a hydraulic correlation. This enables the column holdup to change as load varies. The model parameters can be estimated solely based on steady-state data. The new transient wave propagation model can be used as a controller model for flexible process operation including load changes. To demonstrate this, we implement full-order and reduced dynamic models of an air separation process and multi-component distillation column in Modelica. We use the open-source framework DyOS for the dynamic optimizations and an Extended Kalman Filter for state estimation. We apply the reduced model in-silico in open-loop forward simulations as well as in several open- and closed-loop optimization and control case studies, and analyze the resulting computational speed-up compared to using full-order stage-by-stage column models. The first case study deals with tracking control of a single air separation distillation column, whereas the second one addresses economic model predictive control of an entire air separation process. The reduced model is able to adequately capture the transient column behavior. Compared to the full-order model, the reduced model achieves highly accurate profiles for the manipulated variables, while the optimizations with the reduced model are significantly faster, achieving more than 95% CPU time reduction in the closed-loop simulation and more than 96% in the open-loop optimizations. This enables the real-time capability of the reduced model in process optimization and control.

Control of an Industrial-type Multicomponent Crude Distillation Column using Biggest Log Modulus Tuning

This paper is mainly focused on the Multi-Input-Multi-Output (MIMO) control design of an industrial-type multicomponent crude distillation column with 5 sidestreams. The mathematical model of a multicomponent crude distillation column was investigated in Ganesh, M et al. (2016), which aimed at predicting the concentration (mole fraction) and control of the concentration of any product taken out from the column. The VLE values on individual trays are obtained by reverse calculation of the Thomas algorithm and the composition on each tray are obtained. A transfer function model is obtained with five inputs namely Liquid flow rate, Vapor flow rate, SRK flow rate, LDO flow rate, and HDO flow rate and five outputs which are concentrations of the Whole Naphtha, SRK, LDO, HDO, and AR. This transfer function model is used to obtain the steady state matrix and the RGA analysis is performed to solve the pairing issues of the complex multivariable system. A PI controller is then designed by using BLT tuning which provides standard tuning methodology. This procedure helps at arriving standard tuning values with less computational effort.

CFD Modeling to Predict Mass Transfer in Multicomponent Mixtures

Abstract A novel three-dimensional computational fluid dynamics mass transfer (CMT) model in Eulerian–Eulerian frame work is deploys for investigating the concentration profiles, and trays efficiencies in multicomponent distillation columns. The proposed model is based on Maxwell Stefan equations, and CFD was employed as a powerful tool to model the hydrodynamics and mass transfer. The two phases are modelled as two interpenetrating phases with interphase momentum, heat and mass transfer. The Closure model is developed for mass interphase transfer rate in ternary mixtures. The predictability of the mass transfer behaviours of multicomponent can result in a more efficient and predictable design of distillation trays. Two non-ideal ternary mixtures were studied. The tray geometry and operating conditions are based on the experimental works of Kalbassi and the composition profiles, tray efficiencies, and point efficiencies of mixtures were presented. The obtained results were confirmed by the experimental data. The results indicate that the values of individual component tray efficiencies and point efficiencies for these multicomponent systems were considerably different which confirm the interactive nature of the mass transfer in multicomponent mixtures. These mixtures also illustrated different point efficiencies across the tray because of the composition dependency of these mixtures. The average relative error for the prediction of efficiencies is about 8 %, which indicates the accuracy of the model.

A rate-based dynamic model of multicomponent distillation column for 18O isotope separation

The rate-based model of multicomponent distillation was developed in order to study dynamic behavior of a distillation column used for 18O isotope separation under total reflux condition. The present research describes water distillation as a multicomponent reactive distillation process using a mechanistic method in which reaction and isotope exchanges between the components can be predicted based on the molecular thermodynamics and principles of probability. The non-equilibrium formulation was applied based on the mass transfer of nine components in the phases interface resulting via Maxwell-Stefan equations. The separation factors of these components for equilibrium calculations were estimated by empirical correlation as a function of temperature. The distillation column was equipped with the Sulzer-CY packing and initially was fed through enriched water of 18O that was obtained from cascade of industrial columns. The dynamic equations of the model were solved by the Euler method. The model validation was carried out using comparing the model results with the experimental data obtained from a column of semi-industrial distillation. The results of the non-equilibrium model showed that despite the complexity to solve the rate-based model equations, it had a valid prediction in 18O isotope separation process.

Development of extrinsic functions for optimal synthesis and design—Application to distillation-based separation processes

This work deals with the development and implementation of mathematical models in the General Algebraic Modeling System (GAMS) environment for optimization purposes, involving extrinsic functions that are executed outside GAMS from dynamic-link libraries (DLL) implemented in the programming language C. Three DLL libraries are developed to calculate thermodynamic properties: the Raoult's law for vapor-liquid equilibrium, the Non-Random Two-Liquid (NRTL) model, and the Peng–Robinson equation of state. A detailed description on how GAMS and DLL libraries interact is presented. Case studies dealing with the optimal design of multi-component distillation columns with increasing complexity levels are discussed. For the proposed case studies, the obtained results show that the usage of the proposed extrinsic functions allows to significantly enhance the model implementation compared to the traditional model implementation approach, and to considerably reduce the model size as well as the computational time required by the optimization algorithms.

Side draw control design for a high purity multi-component distillation column

Industrial methanol production involves a multi component feed containing methanol, water and trace levels of ethanol being refined to produce AA grade methanol at high product recovery. Due to practical constraints, the bottoms discharge of the column is primarily water with only trace of methanol impurities. As a result of these constraints, ethanol, which is a non-key middle boiling component gets “trapped” near the side draw of the column forming an ethanol bulge, which in turn results in non-linear, inverse, time and state varying behaviour of the side draw ethanol composition. In this work, we established that the existence of the ethanol bulge creates the complex process behaviour of the side draw ethanol composition and that this bulge needs to be explicitly controlled. This type of explicit composition bulge analysis and subsequent control has not been attempted on methanol distillation columns before. For this purpose a novel, robust and practical side draw control scheme to detect and remedy the excess ethanol bulge movement using override control is presented. The side draw controller, together with other regulatory controllers is shown to maintain on-specification operations of the column. Disturbance rejection tests carried out illustrate that the side draw control scheme will keep the column operating within commercial specification. It is also shown that a traditional DV control structure is unable to achieve this objective.

Monotonic reformulation and bound tightening for global optimization of ideal multi-component distillation columns

This paper addresses the problem of determining cost-minimal process designs for ideal multi-component distillation columns. The special case of binary distillation was considered in the former work (Ballerstein et al. in Optim Eng 16(2):409–440, 2015. https://doi.org/10.1007/s11081-014-9267-5 ). Therein, a problem-specific bound-tightening strategy based on monotonic mole fraction profiles of single components was developed to solve the corresponding mixed-integer nonlinear problems globally. In the multi-component setting, the mole fraction profiles of single components may not be monotonic. Therefore the bound-tightening strategy from the binary case cannot be applied directly. In this follow-up paper, a model reformulation for ideal multi-component distillation columns is presented. The reformulation is achieved by suitable aggregations of the involved components. Proofs are given showing that mole fraction profiles of aggregated components are monotonic. This property is then used to adapt the bound-tightening strategy from the binary case to the proposed model reformulation. Computational results are provided that indicate the usefulness of both the model reformulation and the adapted bound tightening technique for deterministic global optimization of ideal multi-component distillation column designs.

Dynamic simulation of a multicomponent distillation column for D-T separation

Cryogenic distillation (CD) process is being employed, among other applications, in tritium separation technologies and in case of ITER is one of the key processes in the fuel cycle. The ITER Isotope Separation System has to process by cryogenic distillation various mixtures of H-D-T depending from the various torus operation scenarios.Cryogenic distillation has also been employed to separate and concentrate tritium in a CANDU water detritiation system. Dynamic simulation of a distillation column gives information on the behavior of the system when fluctuations in flow feed or feed concentration may occur, with direct impact on the design of the control system.The objective of this work is to present a mathematical model for dynamic simulation of a multicomponent distillation column for D-T separation. The procedure of dynamic simulation is based on Lewis – Matheson method and tridiagonal matrix method for design, respectively simulate a multicomponent distillation column for D-T separation; the model is used to determinate the time required to reach steady state into the entire distillation column, after the occurrence of a process perturbation (e.g. modification of a feed flow, feed concentrations).

An Improved Restarted Adomian-based Solution for the Minimum Reflux Ratio of Multicomponent Distillation Columns

An improved version of powerful Adomian decomposition method (ADM), namely Restarted Adomian decomposition method (RADM), has been employed to find the roots of Underwood’s equations. Underwood’s equations frequently appear in the design of multi-component distillation columns and are used to get a quick estimate of minimum reflux ratio. However, due to highly nonlinear nature and presence of singularities, these equations pose convergence-related difficulties. In this communication, it is shown that RADM is not only capable of overcoming these difficulties but also the values of residual errors show that the RADM-based solutions are superior to the recently developed ADM-based solutions as well as to those obtained by using the well-known Newton–Raphson method. Besides, unlike ADM, the proposed RADM does not require convergence accelerators such as Shanks transformation and only few terms are needed to get the accurate results.

Theoretical Investigation on the Performance of Multicomponent Distillation Column for the Separation of Hydrocarbon Mixture Using Inside out Approach

Theoretical Investigation on the Performance of Multicomponent Distillation Column for the Separation of Hydrocarbon Mixture Using Inside out Approach

Computer Aided Design of a Multi-Component Distillation Column-Using the Fenske-Underwood-Gilliland Short-Cut Method

Most design calculations in multi-component distillation column are tedious and time consuming, thus the need for the Engineer to embrace the applications of computer for the design of multi-component distillation columns design. At the same time the need for accurate design in engineering cannot be over emphasize, meaning that the safety of lives and property so much depend on the accuracy of design calculation, thus, the need for computer packages that will aid the design of multi-component distillation columns to avoid such errors. The objective of this work is to develop a module that uses Fenske-Underwood-Gilliland (FUG) shortcut method in the design of a multi-component distillation column. The FUG shortcut method for multi-component distillation column design uses the Fenske equations for minimum number stages, the Underwood equations for minimum reflux and the Gilliland correlation for the number of stages for a given reflux. The scope of this design is basically development of software that could be used for the calculations involved in the design of multi-component distillation columns. The package developed however utilizes only the FUG shortcut method. The package is built on the Visual Basic 6++ programming language, which is a user friendly and object oriented program.

Estimation of variation in Vapour Liquid Equilibrium constants for modeling a multicomponent crude distillation column

In this paper, the mathematical model of a multicomponent crude distillation column is investigated which aimed at predicting the concentration (mole fraction) of any component on each tray of the column. In literature, it is observed that there is a drastic up and down variations in the steady state composition profile of various multicomponent at each tray of the column. These variations are due to the assumption that Vapor Liquid Equilibrium (VLE) ratios are kept constant throughout the tray for any component and are not true in real time petroleum industries. The proposed method shows a proper procedure for choosing equilibrium constants by using an estimation technique by reverse calculation of Thomas algorithm. Hence, a reverse calculation is performed using a Tridiagonal matrix method for estimating the VLE values from the steady state composition profile for each component mixture. Further, the composition profile for various components, mainly Whole Naphtha, Straight Run Kerosene (SRK), Light Diesel Oil (LDO), Heavy Diesel Oil (HDO) and Atmospheric Residue (AR) are estimated and compared. This modified algorithm is a simple technique for ideal and non-ideal systems with ease of implementing a composition profile for a multicomponent mixture and reduction in computational complexities.