Gade Pandu Rangaiah

National University of Singapore | NUS · Department of Chemical & Biomolecular Engineering

Multi-criteria decision making (MCDM) is necessary for choosing one from the available alternatives (or from the Pareto-optimal solutions obtained by multi-objective optimization), where the performance of each alternative is quantified against several criteria (or objectives). This paper presents a comprehensive review of the application of MCDM m...

Multi-criteria decision making (MCDM) is necessary for choosing one from the available alternatives (or from the obtained Pareto-optimal solutions for multi-objective optimization), where the performance of each alternative is quantified against several criteria (or objectives). This paper presents a comprehensive review of the application of MCDM...

Optimization has found numerous applications in engineering, particularly since 1960s. Many optimization applications in engineering have more than one objective (or performance criterion). Such applications require multi-objective (or multi-criteria) optimization (MOO or MCO). Spurred by this and development of techniques for handling multiple obj...

Control and Safety Analysis of Intensified Chemical Processes covers the basic principles of and recent developments in control and safety analysis of intensified chemical processes, ranging from dynamic simulations and safety analysis to the design and control of important processes. The text discusses general methods and tools such as dynamic sim...

In the catalytic ozonation process (COP), the reactions are complex, and it is very difficult to determine the effect of different operating parameters on the degradation rate of pollutants. Data-based modeling tools, such as the multilayer perceptron (MLP) neural network, can be useful in establishing the complex relationship of degradation effici...

This Matlab code includes the source code of the article "Memory, evolutionary operator, and local search based improved Grey Wolf Optimizer with linear population size reduction technique" which has been published in "Knowledge-Based Systems" journal. The DOI is "https://doi.org/10.1016/j.knosys.2023.110297"

The use of multi-criteria decision-making (MCDM) methods to select the most appropriate one from a range of alternatives considering multiple criteria is a suitable methodology for making informed decisions. When constructing a decision or objective matrix (DOM) for MCDM procedure, either crisp numerical values or fuzzy linguistic terms can be used...

Optimization problems in design and engineering often involve multiple conflicting objectives, and their solution requires multi-objective optimization (MOO). The solution of MOO problems is a set of equally good optimal solutions, known as Pareto-optimal solutions (front). One more critical step is therefore required to choose one solution from th...

Optimization of multi-modal functions is challenging even for evolutionary and swarm-based algorithms as it requires an efficient exploration for finding the promising region of the search space, and effective exploitation to precisely find the global optimum. Grey Wolf Optimizer (GWO) is a recently developed metaheuristic algorithm that is inspire...

To accelerate data-driven studies for various optimization applications in chemical engineering, a comprehensive machine learning aided multi-objective optimization and multi-criteria decision making (abbreviated as ML aided MOO-MCDM) framework is proposed in the present paper. The framework comprises a total of seven steps; firstly, study the appl...

The investigation of dynamic controllability of double liquid-only side-stream distillation (DLSD) is necessary due to its good potential for separating multicomponent mixtures in industrial practice. However, control strategy for DLSD is unique and complex owing to the existence of liquid side transfer streams. This study proposed three temperatur...

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 optimizat...

This work proposes a novel reactive distillation (RD) column for the production of algal biodiesel by the use of a heterogeneous nano-catalyst, Ca(OCH3)2. The elitist non-dominated sorting genetic algorithm (NSGA-II) is employed to optimize the design of this RD column to maximize biodiesel purity while minimizing total annual cost and CO2 emission...

A holistic approach for process design, control and safety analysis through a model-based improved HAZOP based on dynamic simulations is presented and illustrated for the formic acid (FA) process. First, this study develops a plantwide control (PWC) system for the FA process having a reactive dividing-wall column (R-DWC) and multiple material recyc...

This work deals with the formulation of a mixed-integer nonlinear multi-objective optimization (MOO) problem having five objectives to optimize the design of a conventional batch extractive distillation (BED). Of them, three primary objectives are to minimize total annual cost (TAC) and CO2 emissions while maximizing the total annual production of...

Recent research interest has also been on increasing the concentration of lipids in microalgae and optimization of the biodiesel process. Although biodiesel production from algal biomass has significant potential to be used as renewable fuel, there are many aspects, which need researchers' attention for it to be technically and commercially feasibl...

Optimization in chemical engineering often involves two or more objectives, which are conflicting. Multi-objective optimization (MOO) generates a set of equally good solutions from the perspective of objectives used; these solutions are known as non-dominated or Pareto-optimal solutions. Although MOO has become popular in chemical engineering in th...

Empty fruit bunch (EFB) utilization to produce valuable bio-chemicals is seen as an economical and sustainable alternative to waste management in palm oil industries. This work proposed an integrated biorefinery configuration of EFB valorization considering sustainability pillars—namely, economic, environmental, and safety criteria. Techno-economic...

Ethyl acetate and n-hexane are two widely used organic solvents in chemical and pharmaceutical industries; however, separation of their mixtures is very challenging due to the formation of a minimum boiling azeotrope. This study proposes and develops an extractive distillation (ED) process for efficiently separating the mixture of ethyl acetate and...

This tutorial and review of multi-objective optimization (MOO) gives a detailed explanation of the 5 steps to create, solve, and then select the optimum result. Unlike single-objective optimization, the fifth step of selection or ranking of solutions is often overlooked by the authors of papers dealing with MOO applications. It is necessary to unde...

Despite generating enormous interest, the full landscape of process intensification and multi-objective optimization (MOO) remains unexplored in the area of batch extractive distillation (BED). This paper is focused on articulating a mixed-integer nonlinear MOO problem to optimize both conventional and vapor recompressed BED, considering both exist...

In this contribution, a unique multi-objective mixed-integer dynamic optimization problem considering two conflicting objectives, namely, maximization of amount of product per dollar while minimizing CO2 emission is formulated and solved using the elitist non-dominated genetic algorithm for both conventional batch distillation (CBD) and vapor recom...

This reference manual on Energy Recovery and Reuse (ERR) has 12 chapters. The first two chapters, namely, Introduction (Chapter 1) and Heat Exchanger Types and Principles (Chapter 2) cover the background necessary for the remaining chapters. Chapters 3 to 8 are on basic principles and systematic procedures in pinch analysis for heat recovery and re...

Extractive dividing-wall column (EDWC) is a promising thermally-coupled system for separating multiple azeotrope or close-boiling mixtures; however, its intensified structure with relatively small physical space and strong interactions makes model predictive control (MPC) an attractive scheme for EDWC operation. The performance of MPC strongly depe...

Formic acid (FA) is a chemical with numerous industrial applications. Available literature including patents on FA processes are limited and do not provide sufficient information for process simulation. In the present study, a conventional FA process, known as the Kemira-Leonard (KL) process, for producing 98 wt% FA is developed and simulated using...

Batch distillation columns are more energy inefficient than their continuous analogous. These batch columns commonly operate at a fixed reboiler duty and even reflux ratio. To improve their energetic potential, an attempt is made to optimize the reboiler duty, and reflux ratio profiles of the conventional batch scheme and its vapor recompressed cou...

This work aims at optimizing a vapor recompressed batch distillation that runs at variable reflux mode by employing a multi-objective optimization (MOO) strategy. This involves the formulation of optimization problem using factorial analysis for identifying dominating variables followed by solving the optimization problem using the elitist non-domi...

This works aims at formulating a multi-objective optimization (MOO) strategy to improve the energetic and economic potential of a batch distillation through vapor recompression. The optimization strategy is developed based on elitist non-dominated sorting genetic algorithm along with the selection of an optimal point implementing the technique for...

As a combination of the conventional reactive distillation (RD) and diving-wall column, reactive diving-wall column (RDWC) is the highly thermally integrated process that has the advantages of higher thermodynamic efficiency, lower capital cost and smaller equipment size. In this study, the conceptual design of four different RD processes, i.e. the...

BACKGROUND Bioethanol, an important biofuel, obtained from biomass fermentation is dilute and unsuitable for direct use as fuel for transportation. Its recovery and dehydration to ∼99.5 wt% ethanol is energy‐intensive because of dilute feed (∼10 wt% ethanol) and occurrence of ethanol–water azeotrope. From an energy efficiency perspective, hybrid se...

Over the years, intuition and experience based heuristic approaches are used for the development and operation of batch processing in a distillation column. An optimal operating condition of a batch distillation may lead to run the column most efficiently in terms of both utility consumption and cost. Robust optimization like genetic algorithm has...

Formic acid (FA) is an important chemical with many applications in the industry. Nevertheless, its manufacturing process has not received much attention in the open literature. In Part I of this work, FA process was simulated and optimized for the production of 98 wt% FA. Total annual cost (TAC) of the optimal base case process was 0.686 USD/kg. T...

Formic acid (FA) is an essential chemical but its process design and control have not received much attention in the literature. This contribution describes the design of plantwide control (PWC) structure for the intricate FA process having reactive distillation (RD), multiple liquid and gas recycles as well as snowballing effect. In this process,...

Bioethanol recovery (i.e., pre-concentration from 5 to 10 wt.% ethanol to near azeotrope composition) from the fermentation broth requires significantly more energy compared to bioethanol dehydration from near azeotrope composition to >99.5 wt.% ethanol. The present article proposes and evaluates two different alternatives, namely, double-effect di...

Extractive dividing-wall column (EDWC) was proved to be a promising energy-saving technique for the separation of multiple azeotropes or closing-boiling mixtures; however, its controllability is very challenging due to its intensified structure with smaller physical space and strong interactions. While most studies on the EDWC control focused on ev...

A multi-objective optimization framework that considers the influence of government policy on product design is presented. The government policy affects product design in the form of financial and non-financial incentives, and regulations. The consumers affect product design by their purchase behavior that is in turn influenced by price, product qu...

Formic acid (FA) is an important chemical with many applications in the industry. Despite this, FA process has not received much attention in the open literature. In this work, FA process design and optimization are performed for the production of 98 wt% FA. Total annual cost (TAC) of the optimal base case process is 0.686 USD/kg. In addition, a re...

The release of oxides of sulphur (SOx) and acid mist (H2SO4) during the production of sulphuric acid in the double contact double absorption (DCDA) process is hazardous to the environment. It is a challenging task to minimise these emissions while keeping plant operation within the production requirements and maximise revenue. In this study, SOx em...

Computational fluid dynamics has been used for consequence modelling in place of traditional methodologies, to obtain more accurate results and better understanding of complex problems. With today’s computational technology, it is not difficult to run CFD simulations for few selected scenarios. However, its use to produce a full quantitative risk a...

Heat exchanger network (HEN) retrofitting improves the energy efficiency of current processes by reducing utilities required. It is complicated involving many integer and continuous variables, and numerous combinations; thus an optimization technique is used for solving HEN retrofitting problems. In this work, multi-objective differential evolution...

Reduction of greenhouse gas emissions (GHG) in the automobile sector is one of the main reasons supporting bioethanol production. Bioethanol obtained from biomass fermentation is dilute and unsuitable for use as an automobile fuel. For recovery (pre-concentration) and dehydration (purification) of bioethanol from the fermentation broth, distillatio...

Optimization plays a key role in the design, planning and operation of chemical and related processes for several decades. Techniques for solving optimization problems are of deterministic or stochastic type. Of these, stochastic techniques can solve any type of optimization problems and can be adapted for multiple objectives. Differential evolutio...

Multi-Objective (or multi-criteria) Optimization (MOO) is useful for gaining deeper insights into trade-offs among objectives of interest and then selecting one of the many optimal solutions found. It has attracted numerous applications in chemical engineering. Common techniques for MOO are adaptations of stochastic global optimization methods, whi...

Isopropanol, also known as isopropyl alcohol (IPA) is an important solvent used in many industries. It is mostly produced by direct hydration of propylene involving reversible reaction and azeotropic distillation in separate equipment. There have been many studies on separation of IPA and water azeotropic mixture but very few studies on the use of...

Today, at the threshold of the 21st century, rising apprehensions about the instability of oil prices, energy security and adverse effects of fossil fuels on the environment, have made it imperative to search for alternative energy resources that are clean and sustainable. Among various biofuels, bioethanol is very promising. Bioethanol obtained fr...

In place of traditional empirical methodologies, computational fluid dynamics (CFD) is used for more accurate consequence modelling as it takes into account of geometrical obstructions. However, its use is costly and not practical for large-scale use in the industry. The present paper explores the integration of design of experiments and surrogate...

For optimal design of chemical processes, selectivity, productivity or simple profit is often used as the sole objective for optimization. Several studies in the past decade have investigated multi-objective optimization (MOO) of chemical processes with selectivity, yield, productivity and/or energy as the objectives; economic criterion such as pro...

Liquefied natural gas (LNG) is a clean burning fossil fuel, which offers an energy density comparable to petrol and diesel fuels. LNG production has grown five-fold in the last 25 years. Although there are a few dominant processes for land-based liquefaction plants, there is much interest in the production of LNG off-shore, particularly “Floating L...

Heat exchanger networks (HENs) are employed in process industries to decrease external utilities required. Retrofitting HENs in numerous plants designed in the past and operating currently can achieve significant energy savings for a small investment. For solving HEN retrofitting problems, stochastic global optimization (SGO) methods such as geneti...

This chapter presents three MS Excel programs, namely, EMOO (Excel based Multi-Objective Optimization), NDS (Non-Dominated Sorting) and PM (Performance Metrics) useful for Multi-Objective Optimization (MOO) studies. The EMOO program is for finding non-dominated solutions of a given MOO problem. It has both binary-coded and realcoded NSGA-II (Elitis...

Formic acid (FA) is an important chemical. However, its process design and retrofitting have not received much attention in the open literature. The main objective of this work is to apply the recent methodology for process retrofitting via intensification (Niu and Rangaiah, 2016) to FA process. For this, conventional FA process is first developed...

The first edition of this book on multi-objective optimization (MOO) with focus on chemical engineering was published in December 2008. It was the first book on MOO in chemical engineering and has been well received, which motivated the preparation of this second edition. Optimization is important in many disciplines including chemical engineering...

Multi-objective optimization (MOO) has received considerable attention from researchers in chemical engineering. Bhaskar et al. (2000a) have reviewed reported applications of MOO in chemical engineering until 2000. In this chapter, nearly hundred MOO applications in chemical engineering reported in journals from 2000 until mid 2007 are reviewed bri...

Process optimization often has two or more objectives, which are conflicting. For such situations, Multi-Objective Optimization (MOO) provides many optimal solutions, which are equally good from the perspective of the given objectives. These solutions, known as Pareto-optimal front and as non-dominated solutions, provide deeper insights into trade-...

Downstream separation in the ethyl benzene (EB) production is energy intensive due to the use of multiple distillation columns. One technology to achieve significant energy and capital cost savings for this separation, is the use of dividing-wall column (DWC) to replace conventional columns. In the present study, a typical industrial EB process inc...

Thermal power plants are the most common source of electricity generation. To save limited fuel resources and reduce the production cost, power sectors need to face to the most fundamental challenge, which is improving electricity generation efficiency. Modelling the power generation process is the most direct, essential and accurate way to provide...

In this study, an isopropanol (IPA) process based on reactive distillation (RD) using excess propylene and propylene-propane separation column (splitter) is analyzed for retrofitting. This analysis led to identifying two limitations of this process, namely, excess propylene feed to RD and requirement of high purity IPA product from RD. To overcome...

This paper investigates the numerical behavior of several stochastic optimization methods in phase equilibrium modeling and calculations using different stopping (also known as termination and convergence) criteria. Several optimization methods, namely, Ant Colony Optimization, Particle Swarm Optimization, Differential Evolution and Harmony Search,...

Light olefins such as ethylene and propylene are one of the most important groups of compounds in the chemical industry. However, owing to their similarities in physicochemical properties with their paraffinic counterparts, the separation process requires high capital and operating costs. Hence, various alternative technologies including membrane s...

Heat exchanger networks (HEN) are employed in process industries to decrease external utilities consumption and for economic and environmental sustainability. Retrofitting existing HEN can achieve significant energy savings for a relatively small investment. It is useful for numerous plants designed in the past and operating currently. Mathematical...

In the chemical industry, water is extensively used as a reactant, separation solvent and heating/cooling medium, and therefore water integration is required due to both economic and environmental reasons. This study presents a mathematical model that can be used for grassroots and retrofit design of water networks. Then, a large water network exam...

This chapter describes the modeling, simulation and optimization steps as well as software and tools for design, retrofitting and revamping of chemical processes. A general modeling procedure for process units/operations is illustrated using membrane separation for a gas mixture. This separation process is not readily available in process simulator...

Vacuum operation is required in many process industries for a number of reasons. For this, steam jet ejectors (SJEs) are widely used due to their high reliability and medium pressure steam availability; however, they are highly inefficient. Owing to high energy prices, there is increased retrofitting of SJEs to reduce the energy cost. This chapter...

Table of Contents and Introduction are available at http://www.amazon.com/Chemical-Process-Retrofitting-Revamping-Applications/dp/1119016339 (click on “Look Inside”).

Although process retrofitting is essential for existing chemical plants to remain sustainable, studies on systematic retrofitting methodologies for chemical processes are limited and also do not focus on the possibility of replacing a few unit operations with an intensified unit. Hence, in this study, a heuristic-based systematic methodology is dev...

Biofuels are an attractive source of renewable energy as they can easily replace liquid fuels used in transportation and other machinery. The present study considers typical feed of ethanol-water-CO2 from which ethanol is recovered and purified using two popular techniques: pressure swing adsorption with molecular sieves and extractive distillation...

In the chemical industry, water integration is beneficial from the point of both economic and environmental impacts. An optimal water network reduces fresh water consumption by efficient reuse and recycling of water within the plant. In general, water networks are designed based on a single performance criterion such as fresh water consumption or t...

Cool dialysate is often recommended for prevention of intra-dialytic hypotensive episodes in maintenance hemodialysis (HD) patients. However, its effect on toxin removal is not studied. It is known that inter-compartmental resistance is the main barrier for toxin removal. Cool dialysate can potentially increase this resistance by vasoconstriction a...

Process optimization for two or more objectives is increasing. Since objectives are often conflicting, multi-objective optimization (MOO) provides many Pareto-optimal solutions, quantitative trade-off between objectives, optimal values of decision variables and their trends. These results give greater insight about the process and are useful for se...

In this study, an operator training simulator (OTS) has been developed for the homogeneously catalyzed two-step biodiesel production from waste cooking oil (WCO). Biodiesel from WCO leads to cheaper production and also protects the environment by utilizing WCO effectively and producing non-polluting biodiesel. Currently, many biodiesel producers us...

In this work, Excel-based multi-objective optimization (EMOO) program, based on the elitist non-dominated sorting genetic algorithm, is improved by implementing two termination criteria: a Chi-squared test-based termination criterion and a novel termination criterion based on steady-state detection. The termination criteria were shown to perform re...

Experimental design (ED) is a powerful technique for optimizing the performance of a process. Compared to a model-based optimization technique, ED does not require the development of mathematical formulation but nevertheless needs a good model or experimental setup and statistical analysis. This paper presents an ED based optimization approach of a...

Toxin kinetic modeling (TKM) for hemodialysis patients is an established method to understand the physiological distribution of toxins, their accumulation, and removal characteristics. To estimate unknown parameters in TKMs, patient blood samples are collected during and after dialysis. The question is—when and how many samples should be collected?...