Thermal Safety of Chemical Processes

Risk Assessment and Process Design

Francis Stoessel

• Publisher: Wiley-VCH
• Year: 2020
• Print ISBN: 9783527339211
• eBook ISBN: 9783527696925
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Industrial & Technical Chemistry

Completely revised and updated to reflect the current IUPAC standards, this second edition is enlarged by five new chapters dealing with the assessment of energy potential, physical unit operations, emergency pressure relief, the reliability of risk reducing measures, and process safety and process development.

Clearly structured in four parts, the first provides a general introduction and presents the theoretical, methodological and experimental aspects of thermal risk assessment. Part II is devoted to desired reactions and techniques allowing reactions to be mastered on an industrial scale, while the third part deals with secondary reactions, their characterization, and techniques to avoid triggering them. Due to the inclusion of new content and restructuring measures, the technical aspects of risk reduction are highlighted in the new section that constitutes the final part.

Each chapter begins with a case history illustrating the topic in question, presenting lessons learned from the incident. Numerous examples taken from industrial practice are analyzed, and each chapter concludes with a series of exercises or case studies, allowing readers to check their understanding of the subject matter. Finally, additional control questions have been added and solutions to the exercises and problems can now be found.

Part I
General Aspects of Thermal Process Safety

1
Introduction to Risk Analysis of Fine Chemical Processes

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Case History

A multipurpose reactor was protected against overpressure by a rupture disk, which lead directly to the outside through the roof of the plant. During a maintenance operation, it was discovered that this disk was corroded. Although it was decided to replace it, there was no spare part available. Since the next task to be carried out was a sulfonation reaction, it was decided to leave the relief pipe open without the rupture disk in place. In fact, a sulfonation reaction is unlikely to lead to overpressure (sulfuric acid only starts to boil above 300 °C), so such a protection device should not be required. During the first batch a plug of sublimate formed in the relief line. This went unnoticed, and production continued. After heavy rain, water entered the relief tube and accumulated above the sublimate plug. As the next batch began, the plug heated and suddenly ruptured, allowing the accumulated water to enter the reactor. This led to an abrupt exothermal effect, due to the dilution of concentrated sulfuric acid. The increase in temperature triggered sudden decomposition of the reaction mass, causing the reactor to burst, resulting in huge damage.

Lessons Drawn

This type of incident is difficult to predict. Nevertheless, by using a systematic approach to hazard identification, it should become clear that any water entering the reactor could lead to an explosion. Therefore when changing some parts of the equipment, even if they are not directly involved in a given process, especially in multipurpose plants, one should at least consider possible consequences on the safety parameters of the process.

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Introduction

Systematic searches for hazard, assessment of risk, and identification of possible remediation are the basic steps of risk analysis methods reviewed in this chapter. After an introduction that considers the place of chemical industry in society, the basic concepts related to risk analysis are presented. Section 1.2 reviews the steps of the risk analysis of chemical processes discussed. Safety data are presented in Section 1.3 and the methods of hazard identification in Section 1.4. The chapter closes with a section devoted to the practice of risk analysis.

1.1 Chemical Industry and Safety

The chemical industry, more than any other industry, is perceived as a threat to humans, society, and the environment. Nevertheless, the benefits resulting from this activity cannot be negated: health, crop protection, new material, colors, textiles, and so on. This negative perception is more enhanced after major accidents, such as those at Seveso and Bhopal. Even though such catastrophic incidents are rare, they are spectacular and retain public attention. Thus, a fundamental question is raised: “What risk does society accept regarding the benefits of an activity, of a product?” Such a question assumes that the corresponding risk can be assessed a priori.

In the present chapter, we focus on the methods of risk analysis as they are performed in the chemical industry and especially in fine chemicals and pharmaceutical industries.

1.1.1 Chemical Industry and Society

The aim of the chemical industry is to provide industry and people in general with functional products, which have a precise use in different activities such as pharmaceuticals, mechanics, electricity, electronics, textile, food, and so on.

Thus, on one hand, safety in the chemical industry is concerned with product safety, that is, the risks linked with the use of a product. On the other hand, it is concerned with process safety, that is, the risks linked with manufacturing the product. In this book, the focus is on process safety.

1.1.1.1 Product Safety

Every product between its discovery and its elimination passes through many different steps throughout its histor...

Table of contents

• Cover
• Table of Contents
• Preface
• Acknowledgments
• Part I: General Aspects of Thermal Process Safety
• Part II: Mastering Exothermal Reactions
• Part III: Avoiding Secondary Reactions
• Part IV: Technical Aspects of Thermal Process Safety
• Solutions of Exercises
• Symbols
• Index
• End User License Agreement