Professor Francis Stoessel is Head of Chemical Process Safety Consulting in the Swissi Process Safety GmbH. After graduating in Chemical Engineering from the Universite de Haute Alsace, he spent most of his career working for Ciba-Geigy in their Chemical Engineering Department. He was Head of the Thermal Safety Department at Ciba, later of Process Safety Consulting at Novartis. He then took up a professorship at the Swiss Federal Institute of Technology at Lausanne. Prof. Stoessel has received awards from the Swiss Expert Commission for Safety in the Chemical Industry and the Swiss Society for Thermal Analysis and Calorimetry.

Preface xxi

Acknowledgments xxv

Part I General Aspects of Thermal Process Safety 1

1 Introduction to Risk Analysis of Fine Chemical Processes 3

1.1 Chemical Industry and Safety 4

1.1.1 Chemical Industry and Society 4

1.1.2 Responsibility 6

1.1.3 Definitions and Concepts 7

1.2 Steps of Risk Analysis 8

1.2.1 Scope of Analysis 9

1.2.2 Safety Data Collection 10

1.2.3 Safe Conditions and Critical Limits 10

1.2.4 Identification of Deviations 10

1.2.5 Risk Assessment 11

1.2.6 Risk Matrixes 14

1.2.7 Risk-Reducing Measures 15

1.2.8 Residual Risk 17

1.3 Safety Data 17

1.3.1 Physical Properties 18

1.3.2 Chemical Properties 18

1.3.3 Toxicity 18

1.3.4 Ecotoxicity 20

1.3.5 Fire and Explosion Data 20

1.3.6 Interactions 21

1.4 Systematic Identification of Hazards 21

1.4.1 Checklist Method 22

1.4.2 Failure Mode and Effect Analysis 24

1.4.3 Hazard and Operability Study 24

1.4.4 Decision Table 26

1.4.5 Event Tree Analysis 26

1.4.6 Fault Tree Analysis 27

1.4.7 Brainstorming 29

1.5 The Practice of Risk Analysis 29

1.5.1 Preparing the Risk Analysis 29

1.5.2 The Risk Analysis Team 30

1.5.3 The Team Leader 30

1.5.4 Finalizing the Risk Analysis 31

1.6 Exercises 31

References 32

2 Fundamentals of Thermal Process Safety 35

2.1 Energy Potential 37

2.1.1 Thermal Energy 37

2.1.2 Pressure Effects 41

2.2 Effect of Temperature on Reaction Rate 41

2.2.1 Single Reaction 41

2.2.2 Multiple Reactions 42

2.3 Heat Balance 43

2.3.1 Terms of the Heat Balance 43

2.3.2 Simplified Expression of the Heat Balance 48

2.3.3 Reaction Rate Under Adiabatic Conditions 49

2.4 Runaway Reactions 50

2.4.1 Thermal Explosions 50

2.4.2 Semenov Diagram 51

2.4.3 Parametric Sensitivity 52

2.4.4 Critical Temperature 53

2.4.5 Sensitivity Toward Variation of the Coolant Temperature 55

2.4.6 Time Frame of a Thermal Explosion, the tmrad Concept 56

2.5 Exercises 57

References 59

3 Assessment of Thermal Risks 61

3.1 Thermal Process Safety 62

3.1.1 Thermal Risks 62

3.1.2 Processes Concerned by Thermal Risks 62

3.2 Thermal Risk Assessment Criteria 63

3.2.1 Cooling Failure Scenario 63

3.2.2 Severity 66

3.2.3 Probability 68

3.2.4 Runaway Risk Assessment 70

3.3 Criticality of Chemical Processes 70

3.3.1 Assessment of the Criticality 70

3.3.2 Criticality Classes 72

3.3.3 Special Cases of Criticality Assessment 76

3.3.4 Remarks on Criticality Class 5 76

3.3.5 Using MTT as a Safety Barrier 77

3.4 Assessment Procedures 81

3.4.1 General Rules for Thermal Safety Assessment 81

3.4.2 Practical Procedure for the Assessment of Thermal Risks 81

3.5 Exercises 85

References 87

4 Experimental Techniques 89

4.1 Calorimetric Measurement Principles 90

4.1.1 Classification of Calorimeters 90

4.1.2 Temperature Control Modes of Calorimeters 90

4.1.3 Heat Balance in Calorimeters 92

4.2 Instruments Used in Safety Laboratories 94

4.2.1 Characteristics of Instruments Used for Safety Studies 94

4.2.2 Example of Instruments Used for Safety Studies 97

4.3 Microcalorimeters 97

4.3.1 Differential Scanning Calorimetry (DSC) 97

4.3.2 Calvet Calorimeters 104

4.3.3 Thermal Activity Monitor 106

4.4 Reaction Calorimeters 107

4.4.1 Purpose of Reaction Calorimeters 107

4.4.2 Principles of Reaction Calorimeters 108

4.4.3 Examples of Reaction Calorimeters 110

4.4.4 Applications 113

4.5 Adiabatic Calorimeters 114

4.5.1 Principle of Adiabatic Calorimetry 114

4.5.2 On the Thermal Inertia 115

4.5.3 Dewar Calorimeters 116

4.5.4 Accelerating Rate Calorimeter (ARC) 119

4.5.5 Vent Sizing Package (VSP) 121

4.6 Exercises 122

References 126

5 Assessment of the Energy Potential 131

5.1 Thermal Energy 132

5.1.1 Thermal Energy of Synthesis Reactions 132

5.1.2 Energy Potential of Secondary Reactions 133

5.1.3 Adiabatic Temperature Rise 136

5.2 Pressure Effects 137

5.2.1 Gas Release 137

5.2.2 Vapor Pressure 138

5.2.3 Amount of Solvent Evaporated 139

5.3 Experimental Determination of Energy Potentials 140

5.3.1 Experimental Techniques 140

5.3.2 Choosing the Sample to be Analyzed 141

5.3.3 Assessment of Process Deviations 144

5.4 Exercises 147

References 149

Part II Mastering Exothermal Reactions 153

6 General Aspects of Reactor Safety 155

6.1 Dynamic Stability of Reactors 157

6.1.1 Parametric Sensitivity 157

6.1.2 Sensitivity Toward Temperature: Reaction Number B 157

6.1.3 Heat Balance 158

6.2 Reactor Safety After a Cooling Failure 163

6.2.1 Potential of the Reaction, the Adiabatic Temperature Rise 163

6.2.2 Temperature in Case of Cooling Failure: The Concept of MTSR 164

6.3 Example Reaction System 165

References 168

7 Batch Reactors 171

7.1 Chemical Reaction Engineering Aspects of Batch Reactors 172

7.1.1 Principles of Batch Reaction 172

7.1.2 Mass Balance 173

7.1.3 Heat Balance 174

7.1.4 Strategies of Temperature Control 174

7.2 Isothermal Reactions 175

7.2.1 Principles 175

7.2.2 Design of Safe Isothermal Reactors 175

7.2.3 Safety Assessment 178

7.3 Adiabatic Reaction 178

7.3.1 Principles 178

7.3.2 Design of a Safe Adiabatic Batch Reactor 178

7.3.3 Safety Assessment 179

7.4 Polytropic Reaction 179

7.4.1 Principles 179

7.4.2 Design of Polytropic Operation: Temperature Control 180

7.4.3 Safety Assessment 184

7.5 Isoperibolic Reaction 184

7.5.1 Principles 184

7.5.2 Design of Isoperibolic Operation: Temperature Control 184

7.5.3 Safety Assessment 184

7.6 Temperature-Controlled Reaction 185

7.6.1 Principles 185

7.6.2 Design of Temperature-Controlled Reaction 186

7.6.3 Safety Assessment 187

7.7 Key Factors for the Safe Design of Batch Reactors 188

7.7.1 Determination of Safety Relevant Data 188

7.7.2 Rules for Safe Operation of Batch Reactors 190

7.8 Exercises 193

References 195

8 Semi-batch Reactors 197

8.1 Principles of Semi-batch Reaction 198

8.1.1 Definition of Semi-batch Operation 198

8.1.2 Material Balance 199

8.1.3 Heat Balance of Semi-batch Reactors 200

8.2 Reactant Accumulation in Semi-batch Reactors 202

8.2.1 Fast Reactions 203

8.2.2 Slow Reactions 205

8.2.3 Design of Safe Semi-batch Reactors 207

8.3 Isothermal Reaction 208

8.3.1 Principles of Isothermal Semi-batch Operation 208

8.3.2 Design of Isothermal Semi-batch Reactors 208

8.3.3 Accumulation with Complex Reactions 212

8.4 Isoperibolic, Constant Cooling Medium Temperature 212

8.5 Non-isothermal Reaction 214

8.6 Strategies of Feed Control 215

8.6.1 Addition by Portions 215

8.6.2 Constant Feed Rate 215

8.6.3 Interlock of Feed with Temperature 217

8.6.4 Why Reducing the Accumulation 219

8.7 Choice of Temperature and Feed Rate 219

8.7.1 General Principle 219

8.7.2 Scale-Up from Laboratory to Industrial Scale 220

8.7.3 Online Detection of Unwanted Accumulation 221

8.8 Advanced Feed Control 222

8.8.1 Feed Control by the Accumulation 222

8.8.2 Feed Control by the Thermal Stability 224

8.9 Exercises 226

References 228

9 Continuous Reactors 231

9.1 Continuous Stirred Tank Reactors 232

9.1.1 Mass Balance 233

9.1.2 Heat Balance 233

9.1.3 Cooled CSTR 234

9.1.4 Adiabatic CSTR 234

9.1.5 The Autothermal CSTR 236

9.1.6 Safety Aspects 237

9.2 Tubular Reactors 240

9.2.1 Mass Balance 240

9.2.2 Heat Balance 241

9.2.3 Safety Aspects 242

9.2.4 Performance and Safety Characteristics of Ideal Reactors 246

9.3 Other Continuous Reactor Types 247

9.3.1 Cascade of CSTRs 248

9.3.2 Recycling Reactor 248

9.3.3 Microreactors 249

9.3.4 Process Intensification 251

9.4 Exercises 252

References 253

Part III Avoiding Secondary Reactions 255

10 Thermal Stability 257

10.1 Thermal Stability and Secondary Decomposition Reactions 258

10.2 Triggering Conditions 260

10.2.1 Onset: A Concept Without Scientific Base 260

10.2.2 Decomposition Kinetics, the tmrad Concept 261

10.2.3 Safe Temperature 262

10.2.4 Assessment Procedure 262

10.3 Estimation of Thermal Stability 264

10.3.1 Estimation of TD24 from One Dynamic DSC Experiment 264

10.3.2 Conservative Extrapolation 264

10.3.3 Empirical Rules for the Determination of a "Safe" Temperature 267

10.3.4 Prediction of Thermal Stability 268

10.4 Quantitative Determination of the TD24 269

10.4.1 Principle of Quantitative Determination Methods for the Heat Release Rate 269

10.4.2 Determination of q¿ = f (T) from Isothermal Experiments 269

10.4.3 Determination of q¿ = f (T) from Dynamic Experiments 273

10.4.4 Determination of TD24 275