To Michèle.

The first edition of the book is now over 10 years old, and the book was qualified as a “long seller” by the publisher, which means that the interest of readers remains high. As time passes, the techniques and the knowledge especially in the field of process safety continue to develop. As a senior consultant at TÜV SÜD Schweiz – Process Safety, I have observed a number of trends and changes in the needs of customers in the fine chemicals and pharmaceutical industries. In the last years, besides the traditional fields such as process risk analyses, assessment of thermal risks, more technical aspects like designing and sizing protection systems gained in interest. For this reason it was time to account for these evolutions in the book, which gave rise to modify its structure and add new chapters on physical unit operations, sizing emergency relief systems, and assessment of the reliability of safety measures. Following the wishes of some of the readers, new case studies were added, and typical solutions are provided for all exercises at the end of the book.

Often, chemical incidents are due to loss of control, resulting in runaway reactions. Many of these incidents can be foreseen and avoided if an appropriate analysis of thermal process data is performed in the proper way and in due time. Chemical process safety is seldom part of university curricula, and many professionals do not have the appropriate knowledge to interpret thermal data in terms of risks. As a result, even though responsible for the safety of the process, they do not have easy access to the knowledge. Process safety is often considered a specialist matter; thus most large companies employ specialists in their safety departments. However, this safety knowledge is also required at the front, where processes are developed or performed, that is in process development departments and production. To achieve this objective of providing professionals with the required knowledge on the thermal aspects of their processes, the methods must be made accessible to nonspecialists. Such systematic and easy-to-use methods represent the backbone of this book, in which the methods used for the assessment of thermal risks are presented in a logical and understandable way, with a strong link to industrial practice.

The present book is rooted in a lecture on chemical process safety at graduate level (Masters) at the Swiss Federal Institute of Technology in Lausanne. It is also based on experience gained in numerous training courses for professionals held at the Swiss Safety Institute (Swissi), later at TÜV SÜD Schweiz AG – Process Safety, as well as in a number of major chemical and pharmaceutical companies. Thus it has the character of a textbook and not only addresses students but also addresses professional chemists, chemical engineers, or engineers in process development and production of fine chemicals and pharmaceutical industries, as support for their practice of process safety.

The objective of the book is not to turn the reader into a specialist in thermal safety. It is to guide those who perform risk analysis of chemical processes, develop new processes, or are responsible for chemical production, to understand the thermal aspects of processes, and to perform a scientifically founded – but practically oriented – assessment of chemical process safety. This assessment may serve as a basis for the optimization or the development of thermally safe processes. The methods presented are based on the author's long years of experience in the practice of safety assessment in industry and teaching students and professionals in this matter. It is also intended to develop a common and understandable language between specialists and nonspecialists.

The book is structured in four parts:

• Part I gives a general introduction and presents the theoretical, methodological, and experimental aspects of thermal risk assessment. Chapter 1 gives a general introduction on the risks linked to the industrial practice of chemical reactions. Chapter 2 reviews the theoretical background required for a fundamental understanding of runaway reactions and reviews the thermodynamic and kinetic aspects of chemical reactions. An important part of Chapter 2 is dedicated to the heat balance of reactors. In Chapter 3, a systematic evaluation procedure developed for the evaluation of thermal risks is presented. Since such evaluations are based on data, Chapter 4 is devoted to the most common calorimetric methods used in safety laboratories, and Chapter 5 presents the determination of energy potential in terms of thermal and pressure effects.
• Part II is dedicated to desired reactions and techniques allowing reactions to be mastered on an industrial scale. Chapter 6 introduces the dynamic stability of chemical reactors and criteria commonly used for the assessment of such stability. The behavior of reactors under normal operating conditions is a prerequisite for safe operation, but is not sufficient by itself. Therefore the different reactor types are reviewed with their specific safety problems, particularly in the case of deviations from normal operating conditions. This requires a specific approach for each reactor type, including a study of the heat balance, which is the basis of safe temperature control, and also includes a study of the behavior in cases where the temperature control system fails. The analysis of the different reactor types and the general principles used in their design and optimization is presented in Chapters 7–9. Chapter 7 presents the safety aspects of batch reactors with a strong emphasis on the temperature control strategies allowing safe processes. In Chapter 8, the semi-batch reactor is analyzed not only with the different temperature control strategies but also with the feed control strategies reducing the accumulation of non-converted reactants. In Chapter 9, the use of continuous reactors as tubular reactors, continuous stirred tank reactors, and their combinations for mastering exothermal reactions is introduced.
• Part III deals with secondary reactions, their characterization, and techniques to avoid triggering them. Chapter 10 reviews secondary reactions, especially the assessment of the probability of triggering them and the definition of a safe temperature. Chapter 11 is dedicated to the important category of self-accelerating reactions, their characteristics, and techniques allowing their control. The problem of heat accumulation situations where heat transfer is reduced is studied in Chapter 12. The different industrial situations where heat confinement may occur are reviewed, and a systematic procedure for their assessment is presented together with techniques that may be used for the design of safe processes. Chapter 13 is devoted to the physical unit operations, presenting specific testing procedures together with the interpretation of the results in terms of safety, on some examples.
• Part IV presents the technical aspects of thermal process safety. The temperature control requires technical means that may strongly influence operation safety. Consequently Chapter 14 is dedicated to the technical aspects of heat transfer and the estimation of heat transfer coefficients. Since risk reducing measures are often required to maintain safe operation, such as in the failure of the process control system, Chapter 15 is specifically dedicated to the evaluation of the control of a runaway reaction and the definition and design of appropriate risk reducing measures. Chapter 16 deals with the sizing of emergency relief systems including two-phase flow. Since planning risk reducing measures also requires to ensure their reliability, Chapter 17 is devoted to the assessment of reliability. The book concludes with Chapter 18 presenting some thoughts about integrated process development.

Each chapter begins with a case history illustrating the topic of the chapter and presenting lessons learned from the incident. Within the chapters, numerous examples stemming from industrial practice are analyzed. At the end of each chapter, a series of exercises or case studies are proposed, allowing the reader to check their understanding of the subject matter. Typical solutions are given at the end of the book.

The methodology presented in this book is the result of long-term experience and concerns with the assessment of thermal risks in the chemical process industry gained in the Central Safety Research Laboratories of the former Ciba, then at Swissi and EPFL, and finally at TÜV SÜD Schweiz AG. Therefore the author would like to thank his colleagues Kaspar Eigenmann, Franz Brogli, Ruedi Gygax, Hans Fierz, Bernhard Urwyler, Pablo Lerena, and Willy Regenass, who all participated in the development of the methodology and techniques covered in this book.

Many applications and methods were developed by students or young colleagues during diploma works, Master and PhD thesis, or development projects. Among others, the author is grateful to Jean-Michel Dien, Olivier Ubrich, Marie-Agnès Schneider, Benoît Zufferey, Pierre Reuse, Nadia Baati, and Charles Guinand.

The author also appreciated a lot the opportunity of discussions with Bertrand Roduit (AKTS SA, isoconversional methods) and Jim Burelbach (Fauske & Associates LLC, VSP) about their respective specialties. Roland Obermüller and Danny Levin made pertinent suggestions about the contents.

The author would like to especially acknowledge colleagues who reviewed parts of the final manuscript: Anne-Florence Tran-Van who reviewed the major part of the manuscript and Georg Suter, Carine Mayoraz, and Mischa Schwaninger who reviewed the parts concerning their own specialties. Many pertinent suggestions were made to improve the readability of a rather complex matter.

Writing a book like this is a long-term project, which cannot be brought to its end without some sacrifices. Thus my last thoughts go to my family, especially my wife Michèle, who not only accepted neglect during the course of writing but also encouraged and supported me and the work. “Tu n'aurais pas un livre à écrire?”