Drying in the Process Industry

C.M. VAN 'T LAND has run the seminar and consulting company Van 't Land Processing since 1999. Prior to that, he worked at Akzo Nobel Chemicals from 1968-2000 as process engineer, and later, process development manager and project leader. He is the author of Industrial Drying Equipment: Selection and Application and Industrial Crystallization of Melts.

Preface ix 1 Introduction 1 2 Drying as Part of the Overall Process 9 2.1 Residual Moisture / 9 2.2 Optimization of the Dewatering Step / 10 2.3 Process Changes to Simplify Drying / 10 2.4 Combination of Drying and Other Process Steps / 12 2.5 Nonthermal Drying / 15 2.6 Process Changes to Avoid Drying / 17 2.7 No Drying / 19 3 Procedures for Choosing a Dryer 21 3.1 Selection Schemes / 21 3.2 Processing Liquids, Slurries, and Pastes / 31 3.3 Special Drying Techniques / 33 3.4 Some Additional Comments / 34 3.5 Testing on Small-Scale Dryers / 37 3.6 Examples of Dryer Selection / 38 4 Convective Drying 41 4.1 Common Aspects of Continuous Convective Dryers / 42 4.2 Saturated Water Vapor Pressure / 43 4.3 Wet-Bulb Temperature / 44 4.4 Adiabatic Saturation Temperature / 46 4.5 Humidity Chart / 47 4.6 Water-Material Interactions / 49 4.7 Drying with an Auxiliary Material / 52 4.8 Gas Velocities / 54 4.9 Heat Losses / 55 4.10 Electrical Energy Consumption / 57 4.11 Miscellaneous Aspects / 59 4.12 Material Balance (kg*h-1) / 61 4.13 Heat Balance (kJ*h-1) / 61 4.14 Specific Heat of Solids / 63 4.15 Gas Flows and Fan Power / 64 4.16 Direct Heating of Drying Air / 65 5 Continuous Fluid-Bed Drying 67 5.1 General Description / 67 5.2 Fluidization Theory / 70 5.3 Drying Theory for Rectangular Dryers / 76 5.4 Removal of Bound Moisture from a Product in a Rectangular Dryer / 88 5.5 Circular Fluid-Bed Dryers / 90 6 Continuous Direct-Heat Rotary Drying 99 6.1 General Description / 99 6.2 Design Methods / 103 7 Flash Drying 117 7.1 General Description / 117 7.2 Design Methods / 120 7.3 Drying in Seconds / 122 7.4 Application of the Design Methods / 126 8 Spray Drying 133 8.1 General Description / 133 8.2 Single-Fluid Nozzle / 138 8.3 Rotary Atomizer / 143 8.4 Pneumatic Nozzle / 145 8.5 Product Quality / 149 8.6 Heat of Crystallization / 153 8.7 Product Recovery / 154 8.8 Product Transportation / 154 8.9 Design Methods / 155 9 Miscellaneous Continuous Convective Dryers and Convective Batch Dryers 163 9.1 Conveyor Dryers / 164 9.2 Wyssmont Turbo-Dryer / 169 9.3 Nara Media Slurry Dryer / 170 9.4 Anhydro Spin Flash Dryer / 172 9.5 Hazemag Rapid Dryer / 174 9.6 Combined Milling and Drying System / 176 9.7 Batch Fluid-Bed Dryer / 178 9.8 Atmospheric Tray Dryer / 182 9.9 Centrifuge-Dryer / 184 10 Atmospheric Contact Dryers 189 10.1 Plate Dryers / 189 10.2 Mildly Agitated Contact Dryers (Paddle Dryers) / 193 10.3 Vigorously Agitated Contact Dryers / 198 10.4 Vertical Thin-Film Dryers / 202 10.5 Drum Dryers / 204 10.6 Steam-Tube Dryers / 208 10.7 Spiral Conveyor Dryers / 212 10.8 Agitated Atmospheric Batch Dryers / 213 11 Vacuum Drying 217 11.1 Vacuum Drying / 219 11.2 Freeze-Drying / 232 11.3 Vacuum Pumps / 242 12 Steam Drying 251 12.1 Sugar Beet Pulp Dryer / 252 12.2 GEA Exergy Barr-Rosin Dryer / 255 12.3 Advantages of Continuous Steam Drying / 257 12.4 Disadvantages of Continuous Steam Drying / 257 12.5 Additional Remarks Concerning Continuous Steam Drying / 258 12.6 Eirich Evactherm Dryer / 258 13 Radiation Drying 263 13.1 Dielectric Drying / 264 13.2 Infrared Drying / 278 14 Product Quality and Safeguarding Drying 289 14.1 Product Quality / 289 14.2 Safeguarding Drying / 291 15 Continuous Moisture-Measurement Methods, Dryer Process Control, and Energy Recovery 313 15.1 Continuous Moisture-Measurement Methods for Solids / 313 15.2 Continuous Moisture-Measurement Methods for Gases / 321 15.3 Dryer Process Control / 327 15.4 Energy Recovery / 335 16 Gas-Solid Separation Methods 339 16.1 Cyclones / 340 16.2 Fabric Filters / 343 16.3 Scrubbers / 346 16.4 Electrostatic Precipitators / 349 17 Dryer Feeding Equipment 357 17.1 Fluid-Bed Dryers / 358 17.2 Direct-Heat Rotary Dryers / 360 17.3 Flash Dryers / 360 17.4 Spray Dryers / 361 17.5 Conveyor Dryers / 361 17.6 Hazemag Rapid Dryer / 363 17.7 Anhydro Spin Flash Dryer / 365 17.8 Plate Dryers / 365 17.9 Vigorously Agitated Contact Dryers / 365 17.10 Vertical Thin-Film and Drum Dryers / 365 Notation 369 Index 377