Vacuum Technology in the Chemical Industry

List of Contributors XV 1 Fundamentals of Vacuum Technology 1 Wolfgang Jorisch 1.1 Introduction 1 1.2 Fundamentals of Vacuum Technology 2 1.2.1 Fundamentals of Gas Kinetics 3 1.2.2 Equation of State for Ideal Gases 6 1.2.3 Flow of Gases through Pipes in a Vacuum 7 1.2.4 Vacuum Pumps Overview 12 References 14 2 Condensation under Vacuum 15 Harald Grave 2.1 What Is Condensation? 15 2.2 Condensation under Vacuum without Inert 16 2.3 Condensation with Inert Gases 17 2.4 Saturated Inert Gas–Vapour Mixtures 19 2.5 Vapour–Liquid Equilibrium 20 2.6 Types of Condensers 21 2.7 Heat Transfer and Condensation Temperature in a Surface Condenser 24 2.8 Vacuum Control in Condensers 30 2.9 Installation of Condensers 30 2.10 Special Condenser Types 32 Further Reading 34 3 Liquid Ring Vacuum Pumps in Industrial Process Applications 35 Pierre Hähre 3.1 Design and Functional Principle of Liquid Ring Vacuum Pumps 35 3.1.1 Functional Principle 35 3.1.2 Design Details 37 3.2 Operating Behaviour and Design of Liquid Ring Vacuum Pumps 40 3.2.1 Hydraulics 40 3.2.2 Thermodynamics 41 3.2.3 Counterpressure, Air Pressure 45 3.2.4 Design Data 47 3.3 Vibration and Noise Emission with Liquid Ring Vacuum Pumps 48 3.3.1 Vibration Stimulation by Imbalance of Rotary Solids 48 3.3.2 Vibration Stimulation by Pulsation 49 3.3.3 Vibration Stimulation by Flow Separations 50 3.3.4 Measures for Vibration Damping 50 3.4 Selection of Suitable Liquid Ring Vacuum Pumps 51 3.4.1 Simple, Robust and Suitable for the Entire Pressure Range 52 3.4.2 The Vacuum Pump for the Delivery of Liquid 52 3.4.3 Quiet and Compact for a Vacuum Close to the Vapour Pressure 57 3.4.4 A Compact Unit 59 3.4.5 The Right Sealing Concept 59 3.4.6 Vacuum Control 63 3.4.7 Valve Control 63 3.4.8 Power Adjustment 64 3.5 Process Connection and Plant Construction 67 3.5.1 Set-Up and Operation of Liquid Ring Vacuum Pumps 67 3.5.2 Conveyance of the Operating Liquid 68 3.5.3 Precompression 69 3.6 Main Damage Symptoms 73 3.6.1 Water Impact 73 3.6.2 Cavitation 73 3.6.3 Calcareous Deposits and How to Avoid Them 75 3.7 Table of Symbols 78 4 Steam Jet Vacuum Pumps 81 Harald Grave 4.1 Design and Function of a Jet Pump 81 4.2 Operating Behaviour and Characteristic 84 4.3 Control of Jet Compressors 87 4.4 Multi-Stage Steam Jet Vacuum Pumps 90 4.5 Comparison of Steam, Air and Other Motive Media 93 Further Reading 95 5 Mechanical Vacuum Pumps 97 Wolfgang Jorisch 5.1 Introduction 97 5.2 The Different Types of Mechanical Vacuum Pumps 99 5.2.1 Reciprocating Piston Vacuum Pump 100 5.2.2 Diaphragm Vacuum Pump 100 5.2.3 Rotary Vane Vacuum Pump 101 5.2.4 Rotary Plunger Vacuum Pump 102 5.2.5 Roots Vacuum Pump 103 5.2.6 Dry Compressing Vacuum Pump 104 5.3 When Using Various Vacuum Pump Designs in the Chemical or Pharmaceutical Process Industry, the Following Must Be Observed 104 5.3.1 Circulatory-Lubricated Rotary Vane and Rotary Plunger Vacuum Pumps 104 5.3.2 Fresh-Oil-Lubricated Rotary Vane Vacuum Pumps 108 5.3.3 Dry, Respectively Oil-Free Compressing Vacuum Pumps 110 5.3.4 Roots Vacuum Pumps 111 5.3.5 Dry Compressing Vacuum Pumps for Chemistry Applications 118 References 128 6 Basics of the Explosion Protection and Safety-Technical Requirements on Vacuum Pumps for Manufacturers and Operating Companies 129 Hartmut Härtel 6.1 Introduction 129 6.2 Explosion Protection 130 6.2.1 General Basics 130 6.2.2 Explosive Atmosphere and Safety Characteristics 131 6.2.3 Measures of the Explosion Protection 144 6.3 Directive 99/92/EC 146 6.3.1 Requirements on Operating Companies of Vacuum Pumps 146 6.3.2 Classification of Hazardous Areas into Zones 149 6.4 Directive 94/9/EC 150 6.4.1 Equipment Groups and Categories 150 6.4.2 Assignment between Equipment Categories and Zones 152 6.4.3 Requirements on Manufacturers of Vacuum Pumps 153 6.4.4 Conformity Assessment Procedure 154 6.4.5 Application of the Regulations of the Directive 155 6.5 Summary 157 References 158 Further Reading 159 7 Measurement Methods for Gross and Fine Vacuum 161 Werner Große Bley 7.1 Pressure Units and Vacuum Ranges 161 7.2 Directly and Indirectly Measuring Vacuum Gauges and Their Measurement Ranges 162 7.3 Hydrostatic Manometers 163 7.4 Mechanical and Electromechanical Vacuum Gauges 164 7.4.1 Sensors with Strain Gauges 165 7.4.2 Thermal Conductivity Gauges 167 7.4.3 Thermal Conductivity Gauges with Constant Filament Heating Power 169 7.4.4 Thermal Conductivity Gauges with Constant Filament Temperature 170 7.4.5 Environmental and Process Impacts on Thermal Conductivity Gauges 170 References 172 Further Reading 172 8 Leak Detection Methods 173 Werner Große Bley 8.1 Definition of Leakage Rates 173 8.2 Acceptable Leakage Rate of Chemical Plants 174 8.3 Methods of Leak Detection 175 8.4 Helium as a Tracer Gas 176 8.5 Leak Detection with Helium Leak Detector 176 8.6 Leak Detection of Systems in the Medium-Vacuum Range 177 8.6.1 Connection of Leak Detector to the Vacuum System of a Plant 177 8.6.2 Detection Limit for Leakage Rates at Different Connection Positions of a Multistage Pumping System 179 8.7 Leak Detection on Systems in the Rough Vacuum Range 180 8.7.1 Connection of Leak Detector Directly to the Process Vacuum 180 8.7.2 Connection of Leak Detector at the Exhaust of the Vacuum System 180 8.8 Leak Detection and Signal Response Time 181 8.9 Properties and Specifications of Helium Leak Detectors 182 8.10 Helium Leak Detection in Industrial Rough Vacuum Applications without Need of a Mass Spectrometer 183 8.10.1 Principle of theWise Technology® Sensor 185 8.10.2 Application 186 References 187 Further Reading 187 European Standards 187 9 Vacuum Crystallisation 189 Guenter Hofmann 9.1 Introduction 189 9.2 Crystallisation Theory for Practice 189 9.3 Types of Crystallisers 195 9.4 Periphery 203 9.5 Process Particularities 205 9.5.1 Surface-Cooling Crystallisation 206 9.5.2 Vacuum-Cooling Crystallisation 207 9.5.3 Evaporation Crystallisation 207 9.6 Example – Crystallisation of Sodium Chloride 207 References 209 10 Why Evaporation under Vacuum? 211 Gregor Klinke Summary 211 10.1 Introduction 211 10.2 Thermodynamics of Evaporation 211 10.3 Pressure/Vacuum Evaporation Comparison 213 10.3.1 Vapour Utilisation 214 10.3.2 Design of the Apparatuses 214 10.3.3 Machine Equipment 214 10.3.4 Corrosion 215 10.3.5 Insulation 215 10.3.6 Safety Aspects 215 10.3.7 Product Properties 215 10.3.8 Boiling Range 216 10.4 Possibility of Vapour Utilization 217 10.4.1 External Utilization 217 10.4.2 Multi-Stage Evaporation 217 10.4.3 Mechanical Vapour Recompression 217 Further Reading 220 11 Evaporators for Coarse Vacuum 221 Gregor Klinke Summary 221 11.1 Introduction 221 11.2 Criteria for the Selection of an Evaporator 221 11.2.1 Suitability for the Product 221 11.2.2 Cleaning 222 11.2.3 Quality of Heat Transfer 222 11.2.4 Required Space 222 11.2.5 Cost Efficiency 223 11.3 Evaporator Types 223 11.3.1 Agitator Evaporator 223 11.3.2 Natural Circulation Evaporator 223 11.3.3 Climbing-Film Evaporator 225 11.3.4 Falling-Film Evaporator 226 11.3.5 Forced-Circulation Evaporator 228 11.3.6 Fluidised-Bed Evaporator 230 11.3.7 Plate Evaporator 231 Further Reading 233 12 Basics of Drying Technology 235 Jürgen Oess 12.1 Basics of Solids–Liquid Separation Technology 235 12.2 Basics of Drying Technology 235 12.2.1 Convection Drying 236 12.2.2 Radiation Drying 237 12.2.3 Contact Drying 237 12.2.4 Advantages of the Vacuum Drying 242 12.3 Discontinuous Vacuum Drying 244 12.3.1 Setup of a Batch Vacuum Drying System 244 12.3.2 Operation of Discontinuous Vacuum Dryers 244 12.4 Continuous Vacuum Drying 246 12.4.1 Setup of a Batch Vacuum Drying System 246 12.4.2 Operation of Continuous Vacuum Dryers 246 12.4.3 Inlet- and Outlet Systems 247 12.5 Dryer Designs 248 Reference 249 13 Vacuum Technology Bed 251 Michael Jacob 13.1 Introduction to Fluidized Bed Technology 251 13.1.1 Open or Once-through Fluidized Bed Plants 251 13.1.2 Normal Pressure Fluidized Bed Units with Closed-Loop Systems 251 13.2 Vacuum Fluidized Bed Technology 253 13.2.1 Layout 253 13.2.2 Sequence of Operation 255 13.2.3 Fluidization at Vacuum Conditions 255 13.2.4 Heat Energy Transfer under Vacuum Conditions 256 13.2.5 Applications 257 References 258 14 Pharmaceutical Freeze-Drying Systems 259 Manfred Heldner 14.1 General Information 259 14.2 Phases of a Freeze-Drying Process 260 14.2.1 Freezing 260 14.2.2 Primary Drying – Sublimation 261 14.2.3 Secondary Drying 264 14.2.4 Final Treatment 264 14.2.5 Process Control 265 14.3 Production Freeze-Drying Systems 266 14.3.1 Drying Chamber and Shelf Assembly 267 14.3.2 Ice Condenser 270 14.3.3 Refrigerating System 271 14.3.4 Vacuum System 273 14.3.5 Cleaning of the Freeze-Drying System 274 14.3.6 Sterilisation 276 14.3.7 VHP Sterilisation 277 14.4 Final Comments 278 Further Reading 279 15 Short Path and Molecular Distillation 281 Daniel Bethge 15.1 Introduction 281 15.2 Some History 281 15.2.1 Vacuum Distillation 282 15.2.2 Short Path Evaporator 285 15.2.3 The Vacuum System 286 15.2.4 Distillation Plant 288 15.2.5 Application Examples 289 15.2.6 New Developments 292 15.3 Outlook 293 References 293 16 Rectification under Vacuum 295 Thorsten Hugen 16.1 Fundamentals of Distillation and Rectification 295 16.2 Rectification under Vacuum Conditions 298 16.3 Vacuum Rectification Design 302 16.3.1 Liquid and Gas Load 303 16.3.2 Pressure Drop 303 16.3.3 Separation Efficiency 303 16.4 Structured Packings for Vacuum Rectification 305 Nomenclature, Applied Units 309 Greek Symbols 310 Subscripts and Superscripts 310 References 310 17 Vacuum Conveying of Powders and Bulk Materials 311 Thomas Ramme 17.1 Introduction 311 17.2 BasicTheory 312 17.2.1 General 312 17.2.2 Typical Conditions in a Vacuum Conveying Line 315 17.3 Principle Function and Design of a Vacuum Conveying System 318 17.3.1 Multiple-Stage, Compressed-Air Driven Vacuum Generators 319 17.3.2 Conveying and Receiver Vessels 322 17.3.3 Filter Systems 324 17.4 Continuous Vacuum Conveying 325 17.5 Reactor- and Stirring Vessel Loading in the Chemical Industry 325 17.6 Conveying,Weighing, Dosing and Big-Bag Filling and Discharging 330 17.7 Application Parameters 330 References 330 18 Vacuum Filtration – Systemand Equipment Technology, Range and Examples of Applications, Designs 331 Franz Tomasko 18.1 Vacuum Filtration, a Mechanical Separation Process 331 18.1.1 On theTheory of Filtration and Significance of the Laboratory Experiment 332 18.1.2 Guide to Filter-Type Selection 333 18.2 Design of an Industrial Vacuum Filter Station 335 18.3 Methods of Continuous Vacuum Filtration, Types of Design and Examples of Application 337 18.3.1 Vacuum Filtration on a Curved Convex Surface, the Drum Filter 337 18.3.2 Vacuum Filtration on a Curved Concave Surface, the Internal Filter 351 18.3.3 Vacuum Filtration on a Flat Horizontal Surface 352 18.3.4 Vacuum Filtration on a Vertical Flat Surface, the Disc Filter 358 References 361 Index 363