Design Of Reactive Distillation Research Articles

Pilot-scale validation and novel design of reactive distillation with HY@SiC foam catalytic packing for cyclohexyl acetate production

For reactive distillation (RD) process limited by the separation efficiency of gas–liquid mass transfer, if the physical size of the alternating operation in reaction and separation can be further reduced, it would greatly promote the efficiency of the RD process. For this purpose, a structured HY@SiC catalytic packing was developed in which the gas–liquid mass transfer separation process and the catalytic reaction occurred simultaneously on its surface. The HY@SiC catalytic packing was used in a pilot-scale column for experimental study on production of cyclohexyl acetate (CA) by RD to verify the performance of the catalytic packing for the first time. Furthermore, a RD model based on the HY@SiC catalytic packing was established based on the reaction kinetics of HY zeolite catalyst obtained in this work. Finally, a novel RD process with double recycle stream for CA production was proposed, which will be optimized design with TAC minimize as the optimization objective based on sequential iterative algorithm.

Structured Data Management for Investigating an Optimum Reactive Distillation Design

Reaction and separation are the two most important processes in the chemical industry that significantly affect the overall energy and cost requirements. Therefore, the operation of integrated reactive separation in a single equipment, such as reactive distillation, potentially increases the chemical process efficiency remarkably. To achieve that advantage, it is vital to design an optimum reactive distillation configuration in the preliminary evaluation. This paper proposes structured data management that can be used to encounter an optimum reactive distillation design. The approach simplified and reduced the data necessity from thousands to dozens by applying a systematic data sorting for the simulation results obtained from the Aspen Plus simulator. Using a case study that is highly relevant to the real chemical processes, i.e., the metathesis of 2-pentene, this study showed that the rule of thumb for determining the optimum design of conventional distillation can be adapted for reactive distillation technology.

Investigation on catalytic distillation for ethyl acetate production with different catalytic packing structures

Here, the performances of tea-bag catalytic packing (TBP) and supported catalytic packing (SCP) in the reaction distillation of ethyl acetate were designed and compared. There are significant differences in the distribution of efficiency factor and reaction rate between them. The results can provide a theoretical reference for the design of reactive distillation. The catalytic packing is the core component of the catalytic distillation, and how the catalyst exists in the packing has significant influence on the process. To investigate the effect of catalyst packings on the catalytic distillation process, the classical ethyl acetate reactive distillation system was utilized, and a supported catalytic packing (SCP) was prepared in comparison with the conventional tea-bag catalytic packing (TBP). Laboratory scale experiments showed that the ethyl acetate conversion of the SCP was superior to the TBP at a low catalyst loading. The effects of reaction kinetics, mass transfer performance and actual catalytic efficiency of the packings on this process were regarded as reasons and studied by combining the experiments and numerical simulation. Results suggested that the relatively immediate “ in-situ separation” caused by the rapid reaction kinetics and better mass transfer performance of SCP may be a main reason for the difference of the conversion.

Production of Biofuel Additives Using Catalytic Bioglycerol Etherification: Kinetic Modelling and Reactive Distillation Design

Glycerol is an unavoidable by-product of the biodiesel production process. The conversion of glycerol into valuable biofuel additives is essential in the fuel industry. The goal of this work is to develop a reactive distillation-based process for the production of biofuel additives by bio-glycerol etherification. In this study, a kinetic model using a lumping approach for glycerol etherification with tert-butyl alcohol (TBA) over Sn (II) phosphomolybdate (Sn1.5PMo12O40) catalyst was developed. Aspen Plus was used to validate the kinetic model by simulating the glycerol etherification with TBA in a batch reactor. The model predictions were in good agreement with the experimental data. A reactive distillation-based process to produce glycerol ethers was developed, and heat integration was conducted to reduce energy consumption. The energy requirements of the integrated process and the CO2 emissions were decreased by 17% and 14%, respectively. An economic evaluation was performed to study the profitability of the process for an annual capacity of 33,000 metric tons of glycerol ethers. It was found that the process is economically attractive, with a return on investment of 29.40% and a payback period of 2.2 years. The reactive distillation-based process is green and promising for producing biofuel additives that are sustainable and environmentally friendly.

Economic, environmental, exergy (3E) analysis and multi-objective genetic algorithm optimization of isopropyl acetate production with hybrid reactive-extractive distillation

Isopropyl acetate (IPAC) is an important fine chemical intermediate with a great demand for industrial production. In view of the high energy consumption in the traditional reactive distillation (RD) process of IPAC production, this study further proposed three enhanced processes of reactive-extractive distillation (RED), reactive-extractive dividing wall column (REDWC) and reactive-extractive distillation coupled pervaporation (REDPV) process. Firstly, the surface charge density distribution between components is calculated by COSMO-SAC model to screen a variety of potential solvents. Combined with the empirical screening method, relative volatility is used to determine the optimal solvent. Then, the conceptual design of RD, RED and REDWC three processes are completed based on reaction kinetics, and the operating conditions of processes are optimized by multi-objective genetic algorithm. Furthermore, REDPV process using pervaporation module instead of solvent recovery column is proposed. Finally, the total annual cost (TAC), gas emissions and exergy efficiency are used to evaluate the proposed process. The results show that compared with RD process, the TAC and gas emission of RED process are reduced by 42.69% and 49.82%. While those of REDWC process are reduced by 45.06% and 52.93%. The thermodynamic efficiency of these two processes is increased by 63.28% and 62.67%. Compared with RED process, REDPV process further reduces the cost by 14.45% and the gas emissions by 34.55%, but obtain the lowest thermodynamic efficiency.

Optimizing algal biodiesel production from a novel reactive distillation based unit: Reducing CO2 emission and cost

The algal biodiesel as a potential alternative to conventional petroleum fuel and first-generation biofuel has been explored extensively but the efficacy of its production in a reactive distillation (RD) unit is yet to be analyzed thoroughly. In this contribution, the performance of the RD column is enhanced by process intensification and optimization. A multi-objective optimization (MOO) strategy is framed for optimizing the RD column for three conflicting objectives. For this MOO, the elitist non-dominated sorting genetic algorithm (NSGA-II) is employed. From the obtained Pareto-optimal front, one optimal solution for RD design is selected using the technique for order of preference by similarity to ideal solution (TOPSIS) with entropy information for weighting of objectives. To further reduce the environmental impact and optimal usage of internal energy, a novel thermally coupled reactive distillation (TCRD) column is suggested. Finally, a biodiesel production unit is developed by integrating a decanter with the TCRD column, to produce biodiesel product of 99.45 wt.% purity. Performance of the TCRD column is better than the conventional RD column, in terms of CO2 emission reduction (14.49%) and total annual cost savings (3.72%). Energetic sustainability of the proposed biodiesel process is determined by net energy ratio (NER) of 1.79, net energy value (NEV) of 18.2 and net renewable energy value (NREV) of 41.4 MJ/kg.

Energy Integration and Reactive Distillation for Dimethyl Ether Synthesis via Catalytic Dehydration of Methanol

Distillation is the most widely used separation technique in the process industry. Its main disadvantage is the high consumption of thermal energy: the heat requirements of the distillation columns often represent most part of the total energy cost of the plant, appropriate integration of the distillation columns with the overall process often results in a significant reduction of the energy consumption in many cases.In this work the concept of the integration has been applied by two integrated design approaches:Heat-integrated design; where the distillation system of the process will be heat-integrated with the background process (i.e. integration between the distillation columns and the heat exchangers).Reactive distillation design; where the reaction and distillation will be accomplished in the same unit.The process of dimethyl ether (DME) synthesis by the catalytic dehydration of methanol has been considered as a case study. Heat-integrated design of DME process showed a significant total annual cost saving of 41 % compared to the conventional process, and the reactive DME distillation column design showed highest saving in total annual cost (TAC) by 81 %. In addition to the cost saving of the two proposed designs, also the flue gas emissions have been reduced using process integration methodology, where 51 % of the total emissions has been reduced by the heat-integrated design and 86 % by the reactive distillation column design.

Conceptual Design of n-Butyl Acetate Synthesis Process by Reactive Distillation Using Residue Curve Maps

Residue curve maps are a powerful tool for the preliminary design of Reactive Distillation (RD). In this study, residue curve maps of the n-butyl acetate synthesis reaction were calculated based on the Langmuir–Hinshelwood–Hougen–Watson kinetic and UNIQUAC models to calculate the physical properties of the system. The results showed that the unstable node branch emerged from the n-butyl acetate/water edge, moved toward the chemical equilibrium surface with increasing Damkohler number, and no ternary reactive azeotropic point appeared when the reaction was added. Conceptual design of n-butyl acetate synthesis by reactive distillation based on residue curve maps is presented. Based on the simulation results, both the energy consumption and the total annual cost were lower than previously reported values.

Global Optimization of Reactive Distillation Processes Using Bat Algorithm

Reactive distillation (RD) is an important process intensification approach with several advantages. It can improve the reaction selectivity and yield, overcome the thermodynamic restrictions, and reduce the cost/energy. However, the optimal design of RD relies on highly nonlinear and multivariable optimization including continuous and integer design variables. The objective function is generally non-convex with several constraints. For this problem, the conventional derivative-based optimization algorithms are faced with convergence problems and fail to guarantee the global optimal solution. Stochastic optimization algorithms appear to be a better alternative for the optimal design of RD because of the high robustness and efficiency. Bat algorithm (BA), which combines advantages of other existing algorithms, is a potential stochastic optimization algorithm. In this work, the BA was used to optimize the RD for the production of methyl acetate (MeAc). The link between Matlab and Aspen Plus was also created to ensure that each solution was provided from rigorous simulations. The total annual cost (TAC) was set as the objective function. Product purity constraints were achieved through Aspen plus instead of algorithms to simplify the process. BA can find the global optimal solution within less computation time than other stochastic algorithms or sequential optimization.

Systematic integrated process design and control of reactive distillation processes involving multi-elements

In this work, integrated process design and control of reactive distillation processes that involve multiple elements (more than two) is addressed through a computer-aided hierarchical decomposition-based framework. Multiple elements are encountered for reactive systems when four or more compounds (including inert compounds) are encountered. The reactive distillation design methods and tools which are similar in concept to design of binary non-reactive distillations and binary reactive distillations are used for design of multi-element reactive distillation processes, such as driving force approach. The methods that are used in this work are based on equivalent binary element concept. This concept provides the representation of a multi-element system in terms of two key elements, light key and heavy key elements. First, the reactive distillation column is designed using the equivalent binary element driving force approach. Next, through analytical, steady-state and closed-loop dynamic analysis it is verified that the control structure, disturbance rejection and energy requirement of the reactive distillation column is better than any other operation point that is not at the maximum driving force. Furthermore, it is shown that the design at the maximum driving force can be both controlled using simple controllers such as PI as well as advanced controllers such as MPC.

Integrated Process Design and Control of Reactive Distillation Processes

In this work, integrated process design and control of reactive distillation processes is presented. Simple graphical design methods that are similar in concept to non-reactive distillation processes are used, such as reactive McCabe-Thiele method and driving force approach. The methods are based on the element concept, which is used to translate a system of compounds into elements. The operation of the reactive distillation column at the highest driving force and other candidate points is analyzed through analytical solution as well as rigorous open-loop and closed-loop simulations. By application of this approach, it is shown that designing the reactive distillation process at the maximum driving force results in an optimal design in terms of controllability and operability. It is verified that the reactive distillation design option is less sensitive to the disturbances in the feed at the highest driving force and has the inherent ability to reject disturbances.

Residue curve maps of ethyl acetate synthesis reaction

The residue curve maps are considered as a powerful tool for the preliminary design of reactive distillation. The residue curve maps of ethyl acetate synthesis reaction were calculated based on the pseudo-homogeneous rate-based kinetic model and the NRTL activity coefficient model. The results show that the unstable node branch emerges from the ethyl acetate/water edge, moving toward the chemical equilibrium surface with the increase of Damkoler value (D), and the node reaches the ternary reactive azeotrope when D→∞ eventually. Conceptual design for the ethyl acetate synthesis of reactive distillation based on the residue curve maps is presented at last.

Optimization based conceptual design of reactive distillation for selectivity engineering

Reactive distillation can be effectively used to enhance the selectivity of the desired product in a multi-reaction system. Due to complex interaction of reactions and distillation, identification of an appropriate reactive distillation configuration for the known performance targets has been a challenge. The objective of this contribution is to present an MINLP optimization technique that would assist one to identify a suitable configuration for selectivity maximization at conceptual design level. An illustrative example of industrially important reaction of dimerization of isobutene for maximizing the selectivity toward di-isobutene is considered. The results of the optimization are found to be in agreement with those obtained by performing independent simulation using ASPEN PLUS simulator. Thus, the work highlights the potential of an optimization based tool for conceptual design of reactive distillation that involves complex reaction systems.

Optimization and Controllability Analysis of Thermally Coupled Reactive Distillation Arrangements with Minimum Use of Reboilers

The optimal design of reactive complex distillation systems is a highly nonlinear and multivariable problem, and the objective function used as optimization criterion is generally nonconvex with several local optimums and subject to several constraints. The esterification of lauric acid and methanol is explored using thermally coupled distillation sequences with side columns and with a minimum number of reboilers. The product of the esterification can be used as biodiesel. This is a major step forward since thermally coupled reactive distillation sequences with side columns and with a minimum number of reboilers offer significant benefits, such as the following: reductions on both capital investment and operating costs due to the absence of the reboilers and higher conversion and selectivity since products are removed as they are produced as well as no occurrence of thermal degradation of the products due to a lower temperature profile in the column. In this work, we have studied the design of reactive distillation with thermal coupling with a minimum number of reboilers, using differential evolution with restrictions coupled to AspenONE Aspen Plus. Also, we have analyzed the control properties of the reactive distillation schemes studied, and the results indicate that the energy requirements and the total annual cost of the complex distillation sequences with a minimum number of reboilers are reduced significantly in comparison with the conventional reactive distillation process and can be also achieved without significant control problems.

Short-Cut Method for the Design of Reactive Distillation Columns

The design of reactive distillation (RD) has received significant attention because of the technological and economic advantages obtained from the simultaneous occurrence of reaction and separation. Although the advantages of RD are well-documented in the literature, the commercial applications of RD are still limited because of the control and operation complexity of these separation systems and the need for improved software tools to reliably model and design RD columns. In this study, a robust short-cut method for the design of multicomponent reactive distillation is presented. This method is based on distillation lines and tray-by-tray calculations defined in terms of reaction-invariant composition variables. Our method provides the number of theoretical stages, the operating reflux ratio, the feed tray location, and the top or bottom flow. We use three case studies to demonstrate the effectiveness of the proposed strategy, namely, the reactive systems for the syntheses of ETBE and MTBE in the presenc...

A novel process for the synthesis of unsaturated polyester

Traditionally polyester production is done in a batch reactor equipped with a separation column for a batch distillation. A promising alternative for the intensification of this process is reactive distillation. The aim of this paper is to study the conceptual design of reactive distillation and to find out whether reactive distillation is potentially interesting compared to batch reactor process. Therefore, a reactive distillation model is developed and sensitivity analysis is used to obtain the design and operational parameters for the reactive distillation process. These parameters are the required number of stages, required residence time, feed ratio, reflux ratio and temperature of feed stream. The model predicts the polymer attribute, isomerization and saturation composition of the polymer in the range of industrial polyester production data. The simulation study shows that the total production time of polyester in a continuous reactive distillation system is reduced from 12 h to 1.5–2 h compared to the industrial batch reactor process. The equilibrium conversion is also raised by 7% compared to the conventional process. The model demonstrated that reactive distillation has the potential to intensify the process by factor of 6–8 in comparison to the batch reactor.

Methodology for design and analysis of reactive distillation involving multielement systems

A new methodology for design and analysis of reactive distillation has been developed. In this work, the element-based approach, coupled with a driving force diagram, has been extended and applied to the design of a reactive distillation column involving multielement (multicomponent) systems. The transformation of ordinary systems to element-based ones and the aggregation of non-key elements allow the important design parameters, such as the number of stages, feed stage and minimum reflux ratio, to be determined by using simple diagrams similar to those regularly employed for non-reactive systems consisting of two components. Based on this methodology, an optimal design configuration is identified using the equivalent binary-element-driving force diagram. Two case studies of methyl acetate (MeOAc) synthesis and methyl- tert-butyl ether (MTBE) synthesis have been considered to demonstrate the successful applications of the methodology. Moreover, energy requirements for various column configurations corresponding to different feed locations are determined to verify whether the optimal design can be identified by following the proposed methodology.

Reactive Thermally Coupled Distillation Sequences: Pareto Front

Design of reactive distillation sequences is a major computer-aided design challenge. The optimal design of reactive complex distillation systems is a highly nonlinear and multivariable problem, and the objective function used as optimization criterion is generally nonconvex with several local optimums and subject to several constraints. In addition, several attributes for the design of these separation schemes are often conflicting objectives, and the design problem should be represented from a multiple objective perspective. As a result, solving with traditional optimization methods is not reliable because they generally converge to local optimums and often fail to capture the full Pareto optimal front. In this work, we have studied the design of reactive distillation with thermal coupling (using as study case the production of fatty esters), generalizing the use of a multiobjective genetic algorithm with restrictions coupled to Aspen ONE Aspen Plus, previously used in the design and optimization of intensified distillation systems. The results obtained in the Pareto front indicate that the energy consumption of the complex distillation sequence can be reduced significantly by varying operational conditions. Trends in the energy consumption, total annual cost, and greenhouse gas emissions of the thermally coupled reactive distillation sequences can be obtained.

Reactive Dividing-Wall Columns - Defying Equilibrium Restrictions

This work presents an integrated reactive-distillation design based on a dividing-wall column (DWC) applied to an industrial case study within AkzoNobel. Remarkably, it is among the first industrial applications of a reactive DWC reported in literature. The benefits of this novel integrated design are the ability to overcome VLE and chemical equilibrium limitations, as well as to separate the main product as high purity side-stream. To solve the problem of a production shift required by market demand changes, we propose an innovative integrated design that combines reaction and separations into one reactive DWC that allows significant savings in capital and operating costs – up to 35% and 15%, respectively. Two scenarios are analyzed and the results of the rigorous AspenPlus simulations are provided.

Reactive distillation design and control

Chapter1: Introduction 1.1 History 1.2 Basics of Reactive Distillation 1.3 Neat Operation versus Excess Reactant 1.4 Limitations 1.5 Scope 1.6 Computational Methods 1.7 References PART 1: STEADY-STATE DESIGN OF IDEAL QUATERNARY SYSTEM Chapter 2: Parameter Effects 2.1 Effect of Holdup on Reactive Trays 2.2 Effect of Number of Reactive Trays 2.3 Effect of Pressure 2.4 Effect of Chemical Equilibrium Constant 2.5 Effect of Relative Volatilities 2.6 Effect of Number of Stripping and Rectifying Trays 2.7 Effect of Reactant Feed Location 2.8 Conclusion Chapter 3: Economic Comparison of Reactive Distillation with a Conventional Process 3.1 Conventional Multi-Unit Process 3.2 Reactive Distillation Design 3.3 Results for Different Chemical Equilibrium Constants 3.4 Results for Temperature-Dependent Relative Volatilities 3.5 Conclusion Chapter 4: Neat Operation versus Using Excess Reactant 4.1 Introduction 4.2 Neat Reactive Column 4.3 Two-Column System with Excess B 4.4 Two-Column System with 20% Excess A 4.5 Economic Comparison 4.6 Conclusion PART 2: STEADY-STATE DESIGN OF OTHER IDEAL SYSTEMS Chapter 5: Ternary Reactive Distillation Systems 5.1 Ternary System without Inerts 5.2 Ternary System with Inerts 5.3 Conclusion Chapter 6: Ternary Decomposition Reaction 6.1 Intermediate Boiling Reactant 6.2 Heavy Key Reactant with Two Column Configuration 6.3 Heavy Key Reactant with One Column Configuration 6.4 Conclusion PART 3: STEADY-STATE DESIGN OF REAL CHEMICAL SYSTEMS Chapter 7: Steady-State Design for Acetic Acid Esterification 7.1 Reaction Kinetics and Phase Equilibrium 7.2 Process Flowsheets 7.3 Steady-State Design 7.4 Process Characteristics 7.5 Discussion 7.6 Conclusion Chapter 8: Design of TAME Reactive Distillation Systems 8.1 Chemical Kinetics and Phase Equilibrium 8.2 Component Balances 8.3 Effect of Parameters on Reactive Column 8.4 Pressure-Swing Methanol Separation Section 8.5 Extractive Distillation Methanol Separation Section 8.6 Economic Comparison 8.7 Conclusion Chapter 9: Design of MTBE and ETBE Reactive Distillation Columns 9.1 MTBE Process 9.2 ETBE Process 9.3 Conclusion PART 4: CONTROL OF IDEAL SYSTEMS Chapter 10: Control of Quaternary Reactive Distillation Columns 10.1 Introduction 10.2 Steady-State Design 10.3 Control Structures 10.4 Selection of Control Tray Location 10.5 Closedloop Performance 10.6 Using More Reactive Trays 10.7 Increasing Holdup on Reactive Trays 10.8 Rangeability 10.9 Conclusion Chapter 11: Control of Excess-Reactant System 11.1 Control Degrees of Freedom 11.2 Single Reactive Column Control Structures 11.3 Control of Two-Column System 11.4 Conclusion Chapter 12: Control of Ternary Reactive Distillation Columns 12.1 Ternary System without Inerts 12.2 Ternary System with Inerts 12.3 Ternary A B+C System: Intermediate Boiling Reactant 12.4 Ternary A B+C System: Heavy Reactant with Two-Column Configuration 12.5 Ternary A B+C System: Heavy Reactant with Single Column PART 5: CONTROL OF REAL SYSTEMS Chapter 13: Control of MeAc/ EtAc/IPAc/BuAc/AmAc Systems 13.1 Process Characteristic 13.2 Control Structure Design 13.3 Extension to Composition Control 13.4 Conclusion Chapter 14: Control of TAME Plantwide Process 14.1 Process Studied 14.2 Control Structure 14.3 Results 14.4 Conclusion Chapter 15 Control of MTBE and ETBE Reactive Distillation Columns 15.1 MTBE Control 15.2 ETBE Control PART 6: HYBRID AND NON-CONVENTIONAL SYSTEMS Chapter 16: Design and Control of Column/Side- Reactor Systems 16.1 Introduction 16.2 Design for Quaternary Ideal System 16.3 Control of Quaternary Ideal System 16.4 Design of Column/Side-Reactor Process for Ethyl Acetate System 16.5 Control of Column/Side-Reactor Process for Ethyl Acetate System 16.6 Conclusion Chapter 17: Effect of Boiling Point Rankings on the Design of Reactive Distillation 17.1 Process and Classification 17.2 Process Configurations 17.3 Relaxation and Convergence 17.4 Results and Discussion 17.5 Conclusion Chapter 18: Effects of Feed Tray Locations on the Design and Control of Reactive Distillation 18.1 Process Characteristics 18.2 Effects of Relative Volatilities 18.3 Effects of Reaction Kinetics 18.4 Operation and Control 18.5 Conclusion APPENDIX A1. Reference A2. Catalog of Types of Real Reactive Distillation Systems