Thermal Safety of Chemical Processes

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1 Francis Stoessel Thermal Safety of Chemical Processes Risk Assessment and Process Design

3 Francis Stoessel Thermal Safety of Chemical Processes

4 Further Reading K. Bhagwati Managing Safety A Guide for Executives 2006 ISBN H. Schütz, P.M. Wiedemann, W. Hennings, J. Mertens, M. Clauberg Comparative Risk Assessment Concepts, Problems and Applications 2006 ISBN R.L. Brauer Safety and Health for Engineers 2005 ISBN C.A. Ericson Hazard Analysis Techniques for System Safety 2005 ISBN F.P. Helmus Process Plant Design Project Management from Inquiry to Acceptance 2008 ISBN

5 Francis Stoessel Thermal Safety of Chemical Processes Risk Assessment and Process Design

6 The Author Prof. Dr.-Ing. F. Stoessel Swiss Institute for the Promotion of Safety & Security Schwarzwaldallee Basel Switzerland All books published by Wiley-VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate. Library of Congress Card No.: applied for British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. Bibliographic information published by the Deutsche Nationalbibliothek Die Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at < WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form by photoprinting, microfilm, or any other means nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law. Printed in the Federal Republic of Germany Printed on acid-free paper Typesetting SNP Best-set Typesetter Ltd., Hong Kong Printing Strauss GmbH, Mörlenbach Bookbinding Litges & Dopf GmbH, Heppenheim ISBN:

7 To Michèle, Sébastien, Claire-Lise and Anne-Florence

9 VII Contents Preface XVII Part I General Aspects of Thermal Process Safety 1 1 Introduction to Risk Analysis of Fine Chemical Processes Introduction Chemical Industry and Safety Chemical Industry and Society Product Safety Process Safety Accidents in Chemical Industry Risk Perception Responsibility Definitions and Concepts Hazard Risk Safety Security Accepted Risk Risk Analysis Steps of Risk Analysis Scope of Analysis Safety Data Collection Safe Conditions and Critical Limits Search for Deviations Risk Assessment Risk Profiles Risk Reducing Measures Residual Risk Safety Data Physical Properties Chemical Properties 17

10 VIII Contents Toxicity Ecotoxicity Fire and Explosion Data Interactions Systematic Search for Hazards Check List Method Failure Mode and Effect Analysis Hazard and Operability Study Decision Table Event Tree Analysis Fault Tree Analysis Key Factors for a Successful Risk Analysis 28 References 29 2 Fundamentals of Thermal Process Safety Introduction Energy Potential Thermal Energy Heat of Reaction Heat of Decomposition Heat Capacity Adiabatic Temperature Rise Pressure Effects Gas Release Vapor Pressure Amount of Solvent Evaporated Effect of Temperature on Reaction Rate Single Reaction Multiple Reactions Heat Balance Terms of the Heat Balance Heat Production Heat Removal Heat Accumulation Convective Heat Exchange Due to Mass Flow Sensible Heat Due to Feed Stirrer Heat Losses Simplified Expression of the Heat Balance Reaction Rate under Adiabatic Conditions Runaway Reactions Thermal Explosions Semenov Diagram Parametric Sensitivity Critical Temperature 52

11 Contents IX Time Frame of a Thermal Explosion, the TMR ad Concept Exercises 56 References 58 3 Assessment of Thermal Risks Introduction Thermal Risks Systematic Assessment Procedure Cooling Failure Scenario Severity Probability Criticality of Chemical Processes Assessment of the Criticality Criticality Classes Criticality Class Criticality Class Criticality Class Criticality Class Criticality Class Remarks Concerning the Use of MTT as a Safety Barrier Assessment Procedures General Rules for Thermal Safety Assessment Practical Procedure for the Assessment of Thermal Risks Exercises 78 References 80 4 Experimental Techniques Introduction Calorimetric Measurement Principles Classification of Calorimeters Operating Modes of Calorimeters Heat Balance in Calorimeters Ideal Accumulation Ideal Heat Flow Isoperibolic Methods Choice of Instruments Used in Safety Laboratories Adiabatic Calorimeters On the Evaluation of Adiabatic Experiments Dewar Calorimeters Accelerating Rate Calorimeter (ARC) Micro Calorimeters Differential Scanning Calorimetry (DSC) Calvet Calorimeters Thermal Activity Monitor Reaction Calorimeters 95

12 X Contents 4.4 Exercises 96 References 97 Part II Mastering Exothermal Reactions General Aspects of Reactor Safety Introduction Dynamic Stability of Reactors Parametric Sensitivity Sensitivity Towards Temperature: Reaction Number B Heat Balance The Semenov Criterion Stability Diagrams Heat Release Rate and Cooling Rate Using Dimensionless Criteria Chaos Theory and Lyapunov Exponents Reactor Safety After a Cooling Failure Potential of the Reaction, the Adiabatic Temperature Rise Temperature in Cases of Cooling Failure: The Concept of MTSR Example Example Reaction System 112 References Batch Reactors Introduction Principles of Batch Reaction Introduction Mass Balance Heat Balance Strategies of Temperature Control Isothermal Reactions Principles Design of Safe Isothermal Reactors Safety Assessment Adiabatic Reaction Principles Design of a Safe Adiabatic Batch Reactor Safety Assessment Polytropic Reaction Principles Design of Polytropic Operation, Temperature Control Safety Assessment Isoperibolic Reaction Principles 133

13 Contents XI Design of Isoperibolic Operation, Temperature Control Safety Assessment Temperature Controlled Reaction Principles Design of Temperature Controlled Reaction Safety Assessment Key Factors for the Safe Design of Batch Reactors Determination of Safety Relevant Data Rules for Safe Operation of Batch Reactors Exercises 144 References Semi-batch Reactors Introduction Principles of Semi-batch Reaction Definition of Semi-batch Operation Material Balance Heat Balance of Semi-batch Reactors Heat Production Thermal Effect of the Feed Heat Removal Heat Accumulation Reactant Accumulation in Semi-batch Reactors Fast Reactions Slow Reactions Design of Safe Semi-batch Reactors Isothermal Reaction Principles of Isothermal Semi-batch Operation Design of Isothermal Semi-batch Reactors Isoperibolic, Constant Cooling Medium Temperature Non-isothermal Reaction Strategies of Feed Control Addition by Portions Constant Feed Rate Interlock of Feed with Temperature Why to Reduce the Accumulation Choice of Temperature and Feed Rate Feed Control by Accumulation Exercises 176 References Continuous Reactors Introduction Continuous Stirred Tank Reactors Mass Balance 181

14 XII Contents Heat Balance Cooled CSTR Adiabatic CSTR The Autothermal CSTR Safety Aspects Instabilities at Start-up or Shut Down Behavior in Case of Cooling Failure Tubular Reactors Mass Balance Heat Balance Safety Aspects Parametric Sensitivity Heat Exchange Capacities of Tubular Reactors Passive Safety Aspects of Tubular Reactors Other Continuous Reactor Types Cascade of CSTRs and Recycle Reactor Micro Reactors 199 References Technical Aspects of Reactor Safety Introduction Temperature Control of Industrial Reactors Technical Heat Carriers Steam Heating Hot Water Heating Other Heating Media Electrical Heating Cooling with Ice Other Heat Carriers for Cooling Heating and Cooling Techniques Direct Heating and Cooling Indirect Heating and Cooling of Stirred Tank Reactors Single Heat Carrier Circulation Systems Secondary Circulation Loop Temperature Control Systems Temperature Control Strategies Isoperibolic Temperature Control Isothermal Control Isothermal Control at Reflux Non Isothermal Temperature Control Dynamic Aspects of Heat Exchange Systems Thermal Time Constant Heating and Cooling Time Cascade Controller Heat Exchange Across the Wall Two Film Theory 219

15 Contents XIII The Internal Film Coefficient of a Stirred Tank Determination of the Internal Film Coefficient The Resistance of the Equipment to Heat Transfer Practical Determination of Heat Transfer Coefficients Evaporative Cooling Amount of Solvent Evaporated Vapor Flow Rate and Rate of Evaporation Flooding of the Vapor Tube Swelling of the Reaction Mass Practical Procedure for the Assessment of Reactor Safety at the Boiling Point Dynamics of the Temperature Control System and Process Design Background Modeling the Dynamic Behavior of Industrial Reactors Experimental Simulation of Industrial Reactors Exercises 236 References Risk Reducing Measures Introduction Strategies of Choice Eliminating Measures Technical Preventing Measures Control of Feed Emergency Cooling Quenching and Flooding Dumping Controlled Depressurization Alarm Systems Time Factor Emergency Measures Emergency Pressure Relief Definition of the Relief Scenario Design of the Relief Device Design of Relief Devices for Multipurpose Reactors Design of the Effluent Treatment System Containment Design of Technical Measures Consequences of Runaway Temperature Pressure Release Closed Gassy Systems Closed Vapor Systems 259

Extrusion-Cooking Techniques

Edited by Leszek Moscicki Extrusion-Cooking Techniques Applications, Theory and Sustainability Edited by Leszek Moscicki Extrusion-Cooking Techniques Further Reading Brennan, J. G., Grandison, A. S. (eds.)