problem solving in chemical process

Practical Chemical Process Optimization

With MATLAB® and GAMS®

• © 2022
• Ioannis K. Kookos 0

Department of Chemical Engineering, University of Patras, Patras, Greece

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• Applications cover examples encountered in chemical processes: chemical reactors, heat transfer and more
• Undergraduate practical introduction of optimization theory to chemical and biochemical systems
• Chapters include an introduction, examples, applications, terms and concepts, case studies, and problem sets

Part of the book series: Springer Optimization and Its Applications (SOIA, volume 197)

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This text provides the undergraduate chemical engineering student with the necessary tools for problem solving in chemical or bio-engineering processes. In a friendly, simple, and unified framework, the exposition aptly balances theory and practice. It uses minimal mathematical concepts, terms, algorithms, and describes the main aspects of chemical process optimization using MATLAB and GAMS. Numerous examples and case studies are designed for students to understand basic principles of each optimization method and elicit the immediate discovery of practical applications. Problem sets are directly tied to real-world situations most commonly encountered in chemical engineering applications. Chapters are structured with handy learning summaries, terms and concepts, and problem sets, and individually reinforce the basics of particular optimization methods. Additionally, the wide breadth of topics that may be encountered in courses such as Chemical Process Optimization, Chemical Process Engineering, Optimization of Chemical Processes, are covered in this accessible text. The book provides formal introductions to MATLAB, GAMS, and a revisit to pertinent aspects of undergraduate calculus. While created for coursework, this text is also suitable for independent study. A full solutions manual is available to instructors who adopt the text for their course.

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Table of contents (7 chapters)

Front matter, preliminary concepts and definitions.

Ioannis K. Kookos

Multidimensional Unconstrained Optimization

Constrained optimization, linear programming, integer and mixed integer programming problems, solving optimization problems in gams®, representative optimization problems in chemical engineering solved in gams®, back matter, authors and affiliations, about the author, bibliographic information.

Book Title : Practical Chemical Process Optimization

Book Subtitle : With MATLAB® and GAMS®

Authors : Ioannis K. Kookos

Series Title : Springer Optimization and Its Applications

DOI : https://doi.org/10.1007/978-3-031-11298-0

Publisher : Springer Cham

eBook Packages : Mathematics and Statistics , Mathematics and Statistics (R0)

Copyright Information : The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022

Hardcover ISBN : 978-3-031-11297-3 Published: 29 October 2022

Softcover ISBN : 978-3-031-11300-0 Published: 29 October 2023

eBook ISBN : 978-3-031-11298-0 Published: 28 October 2022

Series ISSN : 1931-6828

Series E-ISSN : 1931-6836

Edition Number : 1

Number of Pages : XI, 439

Number of Illustrations : 132 b/w illustrations, 19 illustrations in colour

Topics : Optimization , Industrial Chemistry/Chemical Engineering

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Chemical Process Engineering Volume 1: Design, Analysis, Simulation, Integration, and Problem Solving with Microsoft Excel-UniSim Software for Chemical Engineers Computation, Physical Property, Fluid Flow, Equipment and Instrument Sizing

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A. Kayode Coker, PhD, is an engineering consultant for AKC Technology, an honorary research fellow at the University of Wolverhampton, UK, a former engineering coordinator at Saudi Aramco Shell Refinery Company, and chairman of the Department of Chemical Engineering Technology at Jubail Industrial College, Saudi Arabia. He has been a chartered chemical engineer for more than 30 years. He is a fellow of the Institution of Chemical Engineers, UK, and a senior member of the American Institute of Chemical Engineers. He holds a BSc honors degree in chemical engineering, a master of science degree in process analysis and development and PhD in chemical engineering, all from Aston University, Birmingham, UK, and a Teacher’s Certificate in Education at the University of London, UK. He has directed and conducted short courses extensively throughout the world and has been a lecturer at the university level. His articles have been published in several international journals. He is an author of seven books in chemical engineering, a contributor to the Encyclopedia of Chemical Processing and Design, Vol 61 and a certified train-the-mentor trainer. He is also a technical report assessor and interviewer for chartered chemical engineers (IChemE) in the U.K. He is a member of the International Biographical Centre in Cambridge, UK, is in “Leading Engineers of the World for 2008.” He is also a member of “International Who’s Who of ProfessionalsTM” and “Madison Who’s Who in the U.S.”

Rahmat Sotudeh–Gharebaagh, PhD, is a full professor of chemical engineering at the University of Tehran. He teaches process modeling and simulation, transport phenomena, plant design and economics and soft skills. His research interests include computer-aided process design and simulation, fluidization, and engineering education. He holds a BEng degree in chemical engineering from Iran’s Sharif University of Technology, plus a MSc and a PhD in fluidization engineering from Canada’s Polytechnique. He has been an invited Professor at Qatar University and Polytechnique de Montréal. Professor Sotudeh has more than 300 publications in major international journals and conferences, plus four books and four book chapters. He is the co-founder and editor-in-chief of the journal, Chemical Product and Process Modeling , a member of the Iranian Elite Foundation, and an official expert (OE) on the oil industry with the Iranian Official Expert Organization.

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1.1 Problems and Problem Solving

1.2 types and kinds of problems, 1.3 novice versus expert problem solvers/problem solving heuristics, 1.4 chemistry problems, 1.4.1 problems in stoichiometry, 1.4.2 problems in organic chemistry, 1.5 the present volume, 1.5.1 general issues in problem solving in chemistry education, 1.5.2 problem solving in organic chemistry and biochemistry, 1.5.3 chemistry problem solving under specific contexts, 1.5.4 new technologies in problem solving in chemistry, 1.5.5 new perspectives for problem solving in chemistry education, chapter 1: introduction − the many types and kinds of chemistry problems.

• Published: 17 May 2021
• Special Collection: 2021 ebook collection Series: Advances in Chemistry Education Research
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G. Tsaparlis, in Problems and Problem Solving in Chemistry Education: Analysing Data, Looking for Patterns and Making Deductions, ed. G. Tsaparlis, The Royal Society of Chemistry, 2021, ch. 1, pp. 1-14.

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Problem solving is a ubiquitous skill in the practice of chemistry, contributing to synthesis, spectroscopy, theory, analysis, and the characterization of compounds, and remains a major goal in chemistry education. A fundamental distinction should be drawn, on the one hand, between real problems and algorithmic exercises, and the differences in approach to problem solving exhibited between experts and novices on the other. This chapter outlines the many types and kinds of chemistry problems, placing particular emphasis on studies in quantitative stoichiometry problems and on qualitative organic chemistry problems (reaction mechanisms, synthesis, and spectroscopic identification of structure). The chapter concludes with a brief look at the contents of this book, which we hope will act as an appetizer for more systematic study.

According to the ancient Greeks, “The beginning of education is the study of names”, meaning the “examination of terminology”. 1 The word “problem” (in Greek: «πρόβλημα » /“ problēma” ) derives from the Greek verb “ proballein ” (“pro + ballein”), meaning “to throw forward” ( cf. ballistic and ballistics ), and also “to suggest”, “to argue” etc. Hence, the initial meaning of a “ problēma ” was “something that stands out”, from which various other meanings followed, for instance that of “a question” or of “a state of embarrassment”, which are very close to the current meaning of a problem . Among the works of Aristotle is that of “ Problēmata ”, which is a collection of “why” questions/problems and answers on “medical”, “mathematical”, “astronomical”, and other issues, e.g. , “Why do the changes of seasons and the winds intensify or pause and decide and cause the diseases?” 1  

Problem solving is a complex set of activities, processes, and behaviors for which various models have been used at various times. Specifically, “problem solving is a process by which the learner discovers a combination of previously learned rules that they can apply to achieve a solution to a new situation (that is, the problem)”. 2   Zoller identifies problem solving, along with critical thinking and decision making, as high-order cognitive skills, assuming these capabilities to be the most important learning outcomes of good teaching. 3   Accordingly, problem solving is an integral component in students’ education in science and Eylon and Linn have considered problem solving as one of the major research perspectives in science education. 4  

Bodner made a fundamental distinction between problems and exercises, which should be emphasized from the outset (see also the Foreword to this book). 5–7   For example, many problems in science can be simply solved by the application of well-defined procedures ( algorithms ), thus turning the problems into routine/algorithmic exercises. On the other hand, a real/novel/authentic problem is likely to require, for its solution, the contribution of a number of mental resources. 8  

According to Sternberg, intelligence can best be understood through the study of nonentrenched ( i.e. , novel) tasks that require students to use concepts or form strategies that differ from those they are accustomed to. 9   Further, it was suggested that the limited success of the cognitive-correlates and cognitive-components approaches to measuring intelligence are due in part to the use of tasks that are more entrenched (familiar) than would be optimal for the study of intelligence.

The division of cognitive or thinking skills into Higher-Order (HOCS/HOTS) and Lower-Order (LOCS/LOTS) 3,10   is very relevant. Students are found to perform considerably better on questions requiring LOTS than on those requiring HOTS. Interestingly, performance on questions requiring HOTS often does not correlate with that on questions requiring LOTS. 10   In a school context, a task can be an exercise or a real problem depending on the subject's expertise and on what had been taught. A task may then be an exercise for one student, but a problem for another student. 11   I return to the issue of HOT/LOTS in Chapters 17 and 18.

Johnstone has provided a systematic classification of problem types, which is reproduced in Table 1.1 . 8   Types 1 and 2 are the “normal” problems usually encountered in academic situations. Type 1 is of the algorithmic exercise nature. Type 2 can become algorithmic with experience or teaching. Types 3 and 4 are more complex, with type 4 requiring very different reasoning from that used in types 1 and 2. Types 5–8 have open outcomes and/or goals, and can be very demanding. Type 8 is the nearest to real-life, everyday problems.

Classification of problems. Reproduced from ref. 8 with permission from the Royal Society of Chemistry.

Problem solving in chemistry, as in any other domain, is a huge field, so one cannot really be an expert in all aspects of it. Complementary to Johnstone's classification scheme, one can also identify the following forms: quantitative problems that involve mathematical formulas and computations, and qualitative ones; problems with missing or extraordinary data, with a unique solution/answer, or open problems with more than one solution; problems that cannot be solved exactly but need mathematical approximations; problems that need a laboratory experiment or a computer or a data bank; theoretical/thought problems or real-life ones; problems that can be answered through a literature search, or need the collaboration of specific experts, etc.

According to Bodner and Herron, “Problem solving is what chemists do, regardless of whether they work in the area of synthesis, spectroscopy, theory, analysis, or the characterization of compounds”. 12   Hancock et al. comment that: “The objective of much of chemistry teaching is to equip learners with knowledge they then apply to solve problems”, 13   and Cooper and Stowe ascertain that “historically, problem solving has been a major goal of chemistry education”. 14   The latter authors argue further that problem solving is not a monolithic activity, so the following activities “could all be (and have been) described as problem solving:

solving numerical problems using a provided equation

proposing organic syntheses of target compounds

constructing mechanisms of reactions

identifying patterns in data and making deductions from them

modeling chemical phenomena by computation

identifying an unknown compound from its spectroscopic properties

However, these activities require different patterns of thought, background knowledge, skills, and different types of evidence of student mastery” 14   (p. 6063).

Central among problem solving models have been those dealing with the differences in problem solving between experts and novices. Experts ( e.g., school and university teachers) are as a rule fluent in solving problems in their own field, but often fail to communicate to their students the required principles, strategies, and techniques for problem solving. It is then no surprise that the differences between experts and novices have been a central theme in problem solving education research. Mathematics came first, in 1945, with the publication of George Polya's classic book “ How to solve it: A new aspect of mathematical method ”: 15  

“The teacher should put himself in the student's place, he should see the student's case, he should try to understand what is going on in the student's mind, and ask a question or indicate a step that could have occurred to the student himself ”.

Polya provided advice on teaching problem solving and proposed a four-stage model that included a detailed list of problem solving heuristics. The four stages are: understand the problem, devise a plan, carry out the plan, and look back . In 1979, Bourne, Dominowski, and Loftus modeled a three-stage process, consisting of preparation, production , and evaluation . 16   Then came the physicists. According to Larkin and Reif, novices look for an algorithm, while experts tend to think conceptually and use general strategies . Other basic differences are: (a) the comprehensive and more complete scheme employed by experts, in contrast to the sketchy one used by novices; and (b) the extra qualitative analysis step usually applied by experts, before embarking on detailed and quantitative means of solution. 17,18   Reif (1981, 1983) suggested further that in order for one to be able to solve problems one must have available: (a) a strategy for problem solving; (b) the right knowledge base, and (c) a good organization of the knowledge base. 18,19  

Chemistry problem solving followed suit providing its own heuristics. Pilot and co-workers proposed useful procedures that include the steps that characterize expert solvers. 20–22   They developed an ordered system of heuristics, which is applicable to quantitative problem solving in many fields of science and technology. In particular, they devised a “ Program of Actions and Methods ”, which consists of four phases, as follows: Phase 1, analysis of the problem; Phase 2, transformation of the problem; Phase 3, execution of routine operations; Phase 4, checking the answer and interpretation of the results. Genya proposed the use of “sequences” of problems of gradually increasing complexity , with qualitative problems being used at the beginning. 23  

Randles and Overton compared novice students with expert chemists in the approaches they used when solving open-ended problems. 24     Open-ended problems are defined as problems where not all the required data are given, where there is no one single possible strategy and where there is no single correct answer to the problem. It was found that: undergraduates adopted a greater number of novice-like approaches and produced poorer quality solutions; academics exhibited expert-like approaches and produced higher quality solutions; the approaches taken by industrial chemists were described as transitional.

Finally, one can justify the differences between novices and experts by employing the concept of working memory (see Chapter 5). Experienced learners can group ideas together to see much information as one ‘ chunk ’, while novice learners see all the separate pieces of information, causing an overload of working memory, which then cannot handle all the separate pieces at once. 25,26  

Chemistry is unique in the diversity of its problems, some of which, such as problems in physical and analytical chemistry, are similar to problems in physics, while others, such problems in stoichiometry, in organic chemistry (especially in reaction mechanisms and synthesis), and in the spectroscopic identification of compounds and of molecular structure, are idiosyncratic to chemistry. We will have more to say about stoichiometry and organic chemistry below, but before that there is a need to refer to three figures whom we consider the originators of the field of chemistry education research: the Americans J. Dudley Herron and Dorothy L. Gabel and the Scot Alex H. Johnstone, for it is not a coincidence that all three dealt with chemistry problem solving.

For Herron, successful problem solvers have a good command of basic facts and principles; construct appropriate representations; have general reasoning strategies that permit logical connections among elements of the problem; and apply a number of verification strategies to ensure that the representation of the problem is consistent with the facts given, the solution is logically sound, the computations are error-free, and the problem solved is the problem presented. 27–29   Gabel has also carried out fundamental work on problem solving in chemistry. 30   For instance, she determined students’ skills and concepts that are prerequisites for solving problems on moles, through the use of analog tasks, and identified specific conceptual and mathematical difficulties. 31   She also studied how problem categorization enhances problem solving achievement. 32   Finally, Johnstone studied the connection of problem solving ability in chemistry (but also in physics and biology) with working memory and information processing. We will deal extensively with his relevant work in this book (see Chapter 5). In the rest of this section, reference will be made to some further foundational research work on problem solving in chemistry.

Working with German 16-year-old students in 1988, Sumfleth found that the knowledge of chemical terms is a necessary but not sufficient prerequisite for successful problem solving in structure-properties relationships and in stoichiometry. 33   In the U.S. it was realized quite early (in 1984) that students often use algorithmic methods without understanding the relevant underlying concepts. 32   Indeed, Nakhleh and Mitchell confirmed later (1993) that little connection existed between algorithmic problem solving skills and conceptual understanding. 34   These authors provided ways to evaluate students along a continuum of low-high algorithmic and conceptual problem solving skills, and admitted that the lecture method teaches students to solve algorithms rather than teaching chemistry concepts. Gabel and Bunce also emphasized that students who have not sufficiently grasped the chemistry behind a problem tend to use a memorized formula, manipulate the formula and plug in numbers until they fit. 30   Niaz compared student performance on conceptual and computational problems of chemical equilibrium and reported that students who perform better on problems requiring conceptual understanding also perform significantly better on problems requiring manipulation of data, that is, computational problems; he further suggested that solving computational problems before conceptual problems would be more conducive to learning, so it is plausible to suggest that students’ ability to solve computational/algorithmic problems is an essential prerequisite for a “progressive transition” leading to a resolution of novel problems that require conceptual understanding. 35–37  

Stoichiometry problems are unique to chemistry and at the same time constitute a stumbling block for many students in introductory chemistry courses, with students often relying on algorithms. A review of some fundamental studies follows.

Hans-Jürgen Schmid carried out large scale studies in 1994 and 1997 in Germany and found that when working on easy-to-calculate problems students tended to invent/create a “non-mathematical” strategy of their own, but changed their strategy when moving from an easy-to-calculate problem to a more difficult one. 38,39   Swedish students were also found to behave in a similar manner. 40   A recent (2016) study with junior pre-service chemistry teachers in the Philippines reported that the most prominent strategy was the (algorithmic) mole method, while very few used the proportionality method and none the logical method. 41  

Lorenzo developed, implemented, and evaluated a useful problem solving heuristic in the case of quantitative problems on stoichiometry and solutions. 42   The heuristic works as a metacognitive tool by helping students to understand the steps involved in problem solving, and further to tackle problems in a systematic way. The approach guides students by means of logical reasoning to make a qualitative representation of the solution to a problem before undertaking calculations, thus using a ‘backwards strategy’.

The problem format can serve to make a problem easier or more difficult. A large scale study with 16-year-old students in the UK examined three stoichiometry problems in a number of ways. 43   In Test A the questions were presented as they had previously appeared on National School Examinations, while in Test B each of the questions on Test A was presented in a structured sequence of four parts. An example of one of the questions from both Test A and Test B is given below.

• Test A. Silver chloride (AgCl) is formed in the following reaction: AgNO 3 + HCl → AgCl + HNO 3 Calculate the maximum yield of solid silver chloride that can be obtained from reacting 25 cm 3 of 2.0 M hydrochloric acid with excess silver nitrate. (AgCl = 143.5)

Test B. Silver chloride (AgCl) is formed in the following reaction:

(a) How many moles of silver chloride can be made from 1 mole of hydrochloric acid?

(b) How many moles are there in 25 cm 3 of 2.0 M hydrochloric acid?

(c) How many moles of silver chloride can be made from the number of moles of acid in (b)?

(d) What is the mass of the number of moles of silver chloride in (c)? (AgCl = 143.5)

Student scores on Test B were significantly higher than those on Test A, both overall and on each of the individual questions, showing that structuring serves to make the questions easier.

Drummond and Selvaratnam examined students’ competence in intellectual strategies needed for solving chemistry problems. 44   They gave students problems in two forms, the ‘standard’ one and one with ‘hint’ questions that suggested the strategies which should be used to solve the problems. Although performance in all test items was poor, it improved for the ‘hint’ questions.

Finally, Gulacar and colleagues studied the differences in general cognitive abilities and domain specific skills of higher- and lower-achieving students in stoichiometry problems and in addition they proposed a novel code system for revealing sources of students’ difficulties with stoichiometry. 45,46   The latter topic is tackled in Chapter 4 by Gulacar, Cox, and Fynewever.

Stoichiometry problems have also a place in organic chemistry, but non-mathematical problem solving in organic chemistry is quite a different story. 47   Studying the mechanisms of organic reactions is a challenging activity. The spectroscopic identification of the structure of organic molecules also requires high expertise and a lot of experience. On the other hand, an organic synthesis problem can be complex and difficult for the students, because the number of pathways by which students could synthesise target substance “X” from starting substance “A” may be numerous. The problem is then very demanding in terms of information processing. In addition, students find it difficult to accept that one starting compound treated with only one set of reagents could lead to more than one correct product. A number of studies have dealt with organic synthesis. 48–50   The following comments from two students echo the difficulties faced by many students (pp. 209–210): 50  

“… having to do a synthesis problem is one of the more difficult things. Having to put everything together and sort of use your creativity, and knowing that I know everything solid to come up with a synthesis problem is difficult… it's just you can remember… you can use H 2 and nickel to add hydrogen to a bond but then there's like four other ways so if you're just looking for like what you react with, you can remember just that one but if you need five options just in case it's one of the other options that's given on the test… So, you have to know like multiple ways… and some things are used to maybe reduce… for example, something is used to reduce like a carboxylic acid and something else, the same thing, is used to reduce an aldehyde but then something else is used to like oxidize”.

Qualitative organic chemistry problems are dealt with in Chapters 6 and 7.

The present volume is the result of contributions from many experts in the field of chemistry education, with a clear focus on what can be identified as problem solving research. We are particularly fortunate that George Bodner , an authority in chemistry problem solving, has written the foreword to this book. (George has also published a review of research on problem solving in chemistry. 8   )

The book consists of eighteen chapters that cover many aspects of problem solving in chemistry and are organized under the following themes: (I) General issues in problem solving in chemistry education; (II) Problem solving in organic chemistry and biochemistry; (III) Chemistry problem solving in specific contexts; (IV) New technologies in problem solving in chemistry, and (V) New perspectives for problem solving in chemistry education. In the rest of this introductory chapter, I present a brief preview of the following contents.

The book starts with a discussion of qualitative reasoning in problem solving in chemistry. This type of reasoning helps us build inferences based on the analysis of qualitative values ( e.g. , high, low, weak, and strong) of the properties and behaviors of the components of a system, and the application of structure–property relationships. In Chapter 2, Talanquer summarizes core findings from research in chemistry education on the challenges that students face when engaging in this type of reasoning, and the strategies that support their learning in this area.

For Graulich, Langner, Vo , and Yuriev (Chapter 3), chemical problem solving relies on conceptual knowledge and the deployment of metacognitive problem solving processes, but novice problem solvers often grapple with both challenges simultaneously. Multiple scaffolding approaches have been developed to support student problem solving, often designed to address specific aspects or content area. The authors present a continuum of scaffolding so that a blending of prompts can be used to achieve specific goals. Providing students with opportunities to reflect on the problem solving work of others – peers or experts – can also be of benefit in deepening students’ conceptual reasoning skills.

A central theme in Gulacar, Cox and Fynewever 's chapter (Chapter 4) is the multitude of ways in which students can be unsuccessful when trying to solve problems. Each step of a multi-step problem can be labeled as a subproblem and represents content that students need to understand and use to be successful with the problem. The authors have developed a set of codes to categorize each student's attempted solution for every subproblem as either successful or not, and if unsuccessful, identifying why, thus providing a better understanding of common barriers to success, illustrated in the context of stoichiometry.

In Chapter 5, Tsaparlis re-examines the “working memory overload hypothesis” and associated with it the Johnstone–El Banna predictive model of problem solving. This famous predictive model is based on the effect of information processing, especially of working-memory capacity on problem solving. Other factors include mental capacity or M -capacity, degree of field dependence/independence, and developmental level/scientific reasoning. The Johnstone–El Banna model is re-examined and situations are explored where the model is valid, but also its limitations. A further examination of the role of the above cognitive factors in problem solving in chemistry is also made.

Proposing reaction mechanisms using the electron-pushing formalism, which is central to the practice and teaching of organic chemistry, is the subject of Chapter 6 by Bahttacharyya . The author argues that MR (Mechanistic Reasoning) using the EPF (Electron-Pushing Formalism) incorporates several other forms of reasoning, and is also considered as a useful transferrable skill for the biomedical sciences and allied fields.

Flynn considers synthesis problems as among the most challenging questions for students in organic chemistry courses. In Chapter 7, she describes the strategies used by students who have been successful in solving synthetic problems. Associated classroom and problem set activities are also described.

We all know that the determination of chemical identity is a fundamental chemistry practice that now depends almost exclusively on the characterization of molecular structure through spectroscopic analysis. This analysis is a day-to-day task for practicing organic chemists, and instruction in modern organic chemistry aims to cultivate such expertise. Accordingly, in Chapter 8, Connor and Shultz review studies that have investigated reasoning and problem solving approaches used to evaluate NMR and IR spectroscopic data for organic structural determination, and they provide a foundation for understanding how this problem solving expertise develops and how instruction may facilitate such learning. The aim is to present the current state of research, empirical insights into teaching and learning this practice, and trends in instructional innovations.

The idea that variation exists within a system and the varied population schema described by Talanquer are the theoretical tools for the study by Rodriguez, Hux, Philips, and Towns , which is reported in Chapter 9. The subject of the study is chemical kinetics in biochemistry, and especially of the action and mechanisms of inhibition agents in enzyme catalysis, where a sophisticated understanding requires students to learn to reason using probability-based reasoning.

In Chapter 10, Phelps, Hawkins and Hunter consider the purpose of the academic chemistry laboratory, with emphasis on the practice of problem solving skills beyond those of an algorithmic mathematical nature. The purpose represents a departure from the procedural skills training often associated with the reason we engage in laboratory work (learning to titrate for example). While technical skills are of course important, if part of what we are doing in undergraduate chemistry courses is to prepare students to go on to undertake research, somewhere in the curriculum there should be opportunities to practice solving problems that are both open-ended and laboratory-based. The history of academic chemistry laboratory practice is reviewed and its current state considered.

Chapter 11 by Broman focuses on chemistry problems and problem solving by employing context-based learning approaches, where open-ended problems focusing on higher-order thinking are explored. Chemistry teachers suggested contexts that they thought their students would find interesting and relevant, e.g. , chocolate, doping, and dietary supplements. The chapter analyses students’ interviews after they worked with the problems and discusses how to enhance student interest and perceived relevance in chemistry, and how students’ learning can be improved.

Team Based Learning (TBL) is the theme of Chapter 12 by Capel, Hancock, Howe, Jones, Phillips , and Plana . TBL is a structured small group collaborative form of learning, where learners are required to prepare for sessions in advance, then discuss and debate potential solutions to problems with their peers. It has been found to be highly effective at facilitating active learning. The authors describe their experience with embedding TBL into their chemistry curricula at all levels, including a transnational degree program with a Chinese university.

The ability of students to learn and value aspects of the chemistry curriculum that delve into the molecular basis of chemical events relies on the use of models/molecular representations, and enhanced awareness of how these models connect to chemical observations. Molecular representations in chemistry is the topic of Chapter 13 by Polifka, Baluyut and Holme , which focuses on technology solutions that enhance student understanding and learning of these conceptual aspects of chemistry.

In Chapter 14, Limniou, Papadopoulos, Gavril, Touni , and Chatziapostolidou present an IR spectra simulation. The software includes a wide range of chemical compounds supported by real IR spectra, allowing students to learn how to interpret an IR spectrum, via a step by step process. The chapter includes a report on a pilot trial with a small-scale face-to-face learning environment. The software is available on the Internet for everyone to download and use.

In Chapter 15, Sigalas explores chemistry problems with computational quantum chemistry tools in the undergraduate chemistry curriculum, the use of computational chemistry for the study of chemical phenomena, and the prediction and interpretation of experimental data from thermodynamics and isomerism to reaction mechanisms and spectroscopy. The pros and cons of a series of software tools for building molecular models, preparation of input data for standard software, and visualization of computational results are discussed.

In Chapter 16, Stamovlasis and Vaiopoulou address methodological and epistemological issues concerning research in chemistry problem solving. Following a short review of the relevant literature with emphasis on methodology and the statistical modeling used, the weak points of the traditional approaches are discussed and a novel epistemological framework based on complex dynamical system theory is described. Notably, research using catastrophe theory provides empirical evidence for these phenomena by modeling and explaining mental overload effects and students’ failures. Examples of the application of this theory to chemistry problem solving is reviewed.

Chapter 17 provides extended summaries of the chapters, including a commentary on the chapters. The chapter also provides a brief coverage of various important issues and topics related to chemistry problem solving that are not covered by other chapters in the book.

Finally, in Chapter 18, a Postscript address two specific problem solving issues: (a) the potential synergy between higher and lower-order thinking skills (HOTS and LOTS,) and (b) When problem solving might descend to chaos dynamics. The synergy between HOTS and LOTS is demonstrated by looking at the contribution of chemistry and biochemistry to overcoming the current coronavirus (COVID-19) pandemic. One the other hand, chaos theory provides an analogy with the time span of the predictive power of problem solving models.

«Ἀρχὴ παιδεύσεως ἡ τῶν ὀνομάτων ἐπίσκεψις» (Archē paedeuseōs hē tōn onomatōn episkepsis). By Antisthenes (ancient Greek philosopher), translated by W. A. Oldfather (1925).

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Technical groups, follow aiche, spreadsheet problem-solving for chemical engineers.

Limited time summer sale: 20% off select eLearning courses. Use Promo Code SUMMERSALE .

Many chemical engineers are self-taught in the use of spreadsheets for day-to-day problem-solving, which is testimony to the inherent usefulness of this tool. The goal of this course is to provide you with a more comprehensive background in spreadsheet techniques and improve the quality, reliability and efficiency of your work. Dr. Clough will provide instruction using Microsoft Excel to illustrate a wide range of spreadsheet applications and skills that are relevant to the calculations and problem-solving encountered by practicing chemical engineers. Lectures include frequent live spreadsheet demonstrations. There is ample opportunity for you to practice and perfect the sound techniques and the methods taught.

Topics include:

• Excel basic skills – improving your efficiency
• Working with tables of data and information
• Process calculations including flowsheeting and economic analysis
• Applied statistics including regression analysis
• Solving equations – algebraic and differential

Learning Outcomes:

• Develop efficiently well-organized Excel spreadsheets for typical chemical engineering calculations
• Organize and access tables of data and information using Excel’s built-in features and functions
• Carry out typical chemical process calculations, including flowsheet material balances with recycle
• Analyze chemical engineering data using Excel’s statistical tools, including regression analysis
• Carry out targeting and optimization calculations in Excel using the Solver, Goal Seek, and other methods.

Who Should Attend:

Chemical engineers who already have some level of proficiency with Excel and use, or desire to use, spreadsheeting as a common software tool for problem solving and daily work. The course is also ideal for those engineers who believe they are very proficient Excel users, as a common comment on evaluations from those who have attended Dr. Clough’s short courses in the past is “I thought I knew a lot about Excel before I attended this course.” Knowledge of programming in VBA is not required nor expected.

Unit One: Excel Setup and Basic Skills

• Lecture One: Preview of the Course
• Lecture Two: Entry and Formatting of Data and Information
• Lecture Three: Selection, Copying and Moving Efficiently
• Lecture Four: Cell Addressing and Names
• Lecture Five: Creating Excel Formulas with Built-in Functions
• Unit One Quiz: 16 Questions

Unit Two – Working with Tables of Data

• Lecture One: Tables and Lists
• Lecture Two: Lookup Functions
• Lecture Three: Case Studies with the TABLE Function
• Lecture Four: Array Formulas and Functions
• Lecture Five: Pivot Tables and Scenarios
• Unit Two Quiz: 15 Questions

Unit Three – Process Calculations

• Lecture One: Material Flowsheeting
• Lecture Two: Closing recycles with the Iterative Solver
• Lecture Three: Property Estimation and Equations of State
• Lecture Four: Solving Differential Balances
• Lecture Five: Cost Estimation and Cash Flow Analysis
• Unit Three Quiz: 10 Questions

Unit Four – Applied Statistics

• Lecture One: Characterizing Data Sets
• Lecture Two: Creating Excel Graphs
• Lecture Three: Regression Analysis
• Lecture Four: Design of Experiments
• Lecture Five: Statistical Quality Control
• Unit Four Quiz: 12 Questions

Unit Five – Solving Equations

• Lecture One: Algebraic Equations and Equation Sets
• Lecture Two: Differential Equations
• Lecture Three: Use of Solver and Goal Seek
• Lecture Four: Unit Operation Modeling
• Lecture Five: Process Control Calculations
• Unit Five Quiz: 12 Questions

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David E. Clough

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• Course ID: ELS101
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• Problem Solving and Troubleshooting i...

Problem Solving and Troubleshooting in Process Operations

Topic Process Operations

CPD Hours 14

This is an IChemE   approved training course   and not delivered directly by the Institution. For more information about the course,   contact the training provider   directly.

IChemE members get a 10% discount when they enter their membership number at the time of booking.

This highly interactive course is challenging and interesting and will appeal to both engineers and operators, especially those with some 'hands-on' experience in a process operations environment. The course uses a variety of simulation models to give delegates the chance to solve many challenging and realistic problems in a safe environment.

Who will benefit

Engineers and operations personnel who work in chemical plants, process plants of any kind, and oil and gas processing facilities including offshore, onshore, refineries, gas plants, petrochemical plants, FPSOs and LNG plants.

Course outline

• What is problem solving and troubleshooting?
• Methodology
• Respond correctly to abnormal operating conditions
• Exercises to practice solving realistic problems

Upcoming dates

• What is Chemical and Biological Engineering?
• Engineering problem solving
• Error and uncertainty
• Process variables
• Process Fundamentals
• Material Balances
• Reacting systems
• Reaction kinetics
• Reactor design
• Bioreactors
• Fluids and fluid flow
• Mass transfer
• Energy balances
• Heat transfer
• Heat exchangers
• Mechanical energy balances
• Process safety
• Engineering ethics
• Sustainability
• Engineering in a global context
• Terminology
• Decision tree
• The control volume
• Where can we apply material (and energy) balances?
• Material balance equations
• Material balances equations for multiple species
• Material balances: No species formation or consumption
• « Process Fundamentals
• Reacting Systems »

Material Balances ¶

When you want to know how things really work, study them when they’re coming apart. —William Gibson

Terminology ¶

First, let’s remind ourselves of the terminology for process variables .

Consider a process for converting chemical species, according to the reaction stoichiometry \(\ce{A + 3B -> 2C}\) .

digraph simple_process { splines = ortho; bgcolor=transparent; rankdir=LR; node [shape=box]; "i1" [style=invis]; "o1" [style=invis]; "r" [label="process", color=black]; "i1" -> "r" [label="stream 1 \n (species A and B)"]; "r" -> "o1" [label="stream 2 \n (species A and C)"]; }

Stream 1 has the following properties:

\(\dot m\) , \(\dot n\) , \(\dot V\)

\(\dot n_{A}\) , \(\dot n_{B}\) , \(\dot n_{C}\)

\(x_{A}\) , \(x_{B}\) , \(x_{C}\)

\(\rho\) , \(P\) , \(T\)

At steady state, which of those properties will be the same in stream 2 ?

Does the process matter?

First, as individuals, write down your answers. Then, discuss your answers with students around you.

Conservation laws

From Wikipedia : Conservation laws are fundamental to our understanding of the physical world, in that they describe which processes can or cannot occur in nature. In general, the total quantity of the property governed by that law remains unchanged during physical processes.

Which of these are conserved during ‘normal’ CBE processes?

total energy

total number of moles

moles of a given species

Overview of solving material balance problems ¶

Let’s begin with an overview of the approach to solving material balance problems. We’ll then cover methods for specific classes of problems.

Decision tree ¶

digraph decision_tree{ graph [size="4,6"]; bgcolor=transparent; ranksep=0.5; node [shape=box, width=1.75, height=0.6, fontname="Arial", color=darkolivegreen, penwidth="1.5"]; edge [color=black, arrowsize="0.8"]; /* create nodes for courses */ M1 [label="Material Balance"]; M2 [label="Total Balance\nIs Adequate"]; M3 [label="Species Balance(s)\nAre Needed"]; M4 [label="No Formation/\nConsumption"]; M5 [label="Formation/\nConsumption"]; M6 [label="Known\nStoichiometry"]; M7 [label="Unknown\nStoichiometry"]; {rank=same; M1} {rank=same; M2 M3} {rank=same; M4 M5} {rank=same; M6 M7} M1 -> M2 [style="solid"]; M1 -> M3 [style="solid"]; M3 -> M4 [style="solid"]; M3 -> M5 [style="solid"]; M5 -> M6 [style="solid"]; M5 -> M7 [style="solid"]; }

Thus, the following questions will lead you through that decision tree:

Is species information required, or will a total balance suffice?

If species information is required, are there formation/consumption terms?

If there are formation/consumption terms, is the reaction stoichiometry known or unknown?

The control volume ¶

First, let’s define a very useful term in CBE: the control volume .

A control volume is a volume fixed in space or moving with constant flow velocity through which the continuum (gas, liquid, or solid) flows.

It is essentially a region in space that we define to conduct a particular process analysis.

Our control volume could contain…

an entire process

a particular unit operation (heat exchanger, reactor, separator, …)

a series of unit operations or subprocesses

a small volume within a process

It is very important to define your control volume when analyzing CBE processes.

Where can we apply material (and energy) balances? ¶

The material and energy balances (and other conservation laws) we will develop can be applied to almost any control volume.

Essentially, we can apply these balances whenever our control volume has inputs and/or outputs and we have some idea of what’s going on inside this volume.

Material balance equations ¶

In the equations below, we can think of the system as being our control volume.

In words, the fundamental mass balance equation is

In this course, we will focus primarily on systems at steady state . This means that relevant system properties do not change over time. Under these conditions, our material balance equation becomes

Consider the following process with input and output streams:

digraph generic_process { splines = ortho; rankdir=LR; bgcolor=transparent; node [shape=box]; "i1" [style=invis]; "i2" [style=invis]; "o1" [style=invis]; "o2" [style=invis]; "r" [label="process", color=black]; "i1" -> "r" [label="stream 1"]; "i2" -> "r" [label="stream 2"]; "r" -> "o1" [label="stream 3"]; "r" -> "o2" [label="stream 4"]; }

At steady state, the governing mass balance equation would be the following:

More generally, we have the following relationships.

Fundamental mass balance equation

Material balances equations for multiple species ¶

In the general case, the expression for the material balance on a species \(\ce{A}\) that is part of a mixture is

For steady-state conditions, this becomes

Expressing this steady-state relationship mathematically, we have

Mass balance equation for an individual species

\(R_{\text{formation, A}}\) = rate that species \(A\) is formed, in units of \(\si{mass/time}\)

\(R_{\text{consumption, A}}\) = rate that species \(A\) is consumed, in units of \(\si{mass/time}\)

Making use of relationships between our process variables , we can write this equation as

Note that the above equations should be written for one species at a time .

Material balances: No species formation or consumption ¶

A number or important problems in chemical and biological engineering do not include formation or consumption.

Exercise: Species mass balance with no formation or consumption

Two chemicals \(\ce{A}\) (desired) and \(\ce{B}\) (undesired) are partially separated using a chemical separator.

digraph generic_process { splines = ortho; bgcolor=transparent; rankdir=LR; node [shape=box]; "i1" [style=invis]; "o1" [style=invis]; "o2" [style=invis]; "r" [label="chemical separator", color=black]; "i1" -> "r" [label="feed stream"]; "r" -> "o1" [label="product stream"]; "r" -> "o2" [label="waste stream"]; }

The feed stream has a flow rate of \(\SI{100}{kg/hr}\) and contains \(\ce{A}\) at a mass fraction of \(0.20\) , with the balance being \(\ce{B}\) .

Furthermore, \(\SI{98}{percent}\) (by mass) of \(\ce{A}\) in the feed stream leaves in the product stream.

In the waste stream, the mass flow rate of \(\ce{B}\) is \(\SI{65}{kg/hr}\) .

What are the mass flow rates of \(\ce{B}\) in the product stream and \(\ce{A}\) in the waste stream?

Use our problem solving approach .

Guidelines for solving material balance problems involving multiple species

From pg 76 in Introduction to Chemical Engineering: Tools for Today and Tomorrow (5th Edition) :

Determine if species information is required, or if an overall mass balance will suffice. Note: Problems involving multiple species require species information.

If information on a particular species is required, write the balance for that species first. It may be that a single-species equation will provide enough information to solve the problem.

Use species mole balances rather than mass balances if the reaction stoichiometry is known.

Do not attempt to balance the total number of moles for reacting systems if the reaction changes the number of moles.

A total mass balance is frequently useful to determine a missing flow rate for systems where the densities of the input and output streams are approximately constant. The constant-density assumption is applicable to liquid systems that contain a small amount (small concentration) of a reactant or pollutant or dissolved substance such as a salt.

Words like consumed , formed , converted , reacted , produced , generated , absorbed , destroyed , and the like in the problem statement indicate that consumption or formation term are required in the material balance. Systems that include chemical reaction always require formation and/or consumption terms.

If a single species balance does not provide sufficient information to solve the problem, write additional material balances up to the total number of species. If there are still more unknowns than equations, look for additional relationships among the unknowns, such as

Given flow rates or ratios

Fractions (mass or mole) of all species in a stream must add up to \(1.0\)

Stoichiometry: if the process includes a chemical reaction.

Conversion: if it is known that a certain fraction ( \(X\) ) of reactant \(A\) is converted (or consumed) in the process, one can write that the rate of consumption of \(A\) equals that fraction of the total incoming flow rate of \(A\) .

Carry units as you work the problem. Calculation mistakes are frequently discovered as you try to work out the units.