Agitator Design for Gas-Liquid Fermenters and Bioreactors

Agitator Design for Gas-Liquid Fermenters and Bioreactors

by Gregory T. Benz
Agitator Design for Gas-Liquid Fermenters and Bioreactors

Agitator Design for Gas-Liquid Fermenters and Bioreactors

by Gregory T. Benz

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Overview

AGITATOR DESIGN FOR GAS-LIQUID FERMENTERS AND BIOREACTORS

Explore the basic principles and concepts of the design of agitation systems for fermenters and bioreactors

Agitator Design for Gas-Liquid Fermenters and Bioreactors delivers a ­concise treatment and explanation of how to design mechanically sound agitation systems that will perform the agitation process function efficiently and economically. The book covers agitator fundamentals, impeller systems, optimum power and air flow at peak mass transfer calculations, optimizing operation for minimum energy per batch, heat transfer surfaces and calculations, shaft seal considerations, mounting methods, mechanical design, and vendor evaluation.

The accomplished author has created a practical and hands-on tool that discusses the subject of agitation systems from first principles all the way to implementation in the real world. Step-by-step processes are included throughout the book to assist engineers, chemists, and other scientists in the design, construction, installation, and maintenance of these systems.

Readers will also benefit from the inclusion of:

  • A thorough introduction to the design of gas-liquid fermenters and bioreactors
  • An exploration of agitator fundamentals, impeller systems, optimum power, and air flow at peak mass transfer calculations
  • A discussion of how to optimize operation for minimum energy per batch
  • Step-by-step processes to assist engineers, chemists, and scientists
  • An examination of heat transfer surfaces and calculations, shaft seal considerations, mounting methods, and mechanical design
  • Perfect for chemical engineers, mechanical engineers, process engineers, chemists, and materials scientists, Agitator Design for Gas-Liquid Fermenters and Bioreactors will also earn a place in the libraries of pharmaceutical scientists seeking a one-stop resource for designing mechanically sound agitation systems.


    Product Details

    ISBN-13: 9781119650492
    Publisher: Wiley
    Publication date: 04/13/2021
    Pages: 448
    Product dimensions: 0.39(w) x 0.39(h) x 0.39(d)

    About the Author

    Gregory T. Benz, P.E., is the President of Benz Technology International, an engineering consulting firm and Chinese business development corporation. He has authored numerous articles, conducted more than 50 seminars, and holds a patent on a nonrotating, nonseal method of mechanically agitating tanks.

    Table of Contents

    Preface xix

    Foreword xxi

    Foreword for Greg Benz xxiii

    1 Purpose of Agitator Design 1

    References 2

    2 Major Steps in Successful Agitator Design 3

    Define Process Results 3

    Define Process Conditions 5

    Choose Tank Geometry 6

    Calculate Equivalent Power/Airflow Combinations for Equal Mass Transfer Rate 7

    Choose Minimum Combined Power 7

    Choose Shaft Speed; Size Impeller System to Draw Required Gassed Power 7

    Decision Point: D/T and Gassing Factors OK? 8

    Mechanical Design 8

    Decision Point: Is the Mechanical Design Feasible? 8

    Repeat to Find Lowest Cost 8

    Repeat for Different Aspect Ratios 9

    Repeat for Different Process Conditions 9

    Finish 9

    Summary of Chapter 10

    List of Symbols 10

    References 10

    3 Agitator Fundamentals 11

    Agitated Tank Terminology 11

    Prime Mover 11

    Reducer 13

    Shaft Seal 13

    Wetted Parts 13

    Tank Dimensions 14

    How Agitation Parameters Are Calculated 14

    Reynolds Number 15

    Power Number 16

    Pumping Number 17

    Dimensionless Blend Time 17

    Aeration Number 18

    Gassing Factor 18

    Nusselt Number 18

    Froude Number 19

    Prandtl Number 19

    Geometric Ratios 20

    Baffle Number 20

    Dimensionless Hydraulic Force 20

    Thrust Number 21

    Typical Dimensionless Number Curves 21

    A Primer on Rheology 25

    Newtonian Model 26

    Pseudoplastic

    or Shear Thinning, Model (Aka Power Law Fluid) 27

    Bingham Plastic 27

    Herschel–Bulkley 27

    Impeller Apparent Viscosity 29

    A Bit of Impeller Physics 29

    Summary of Chapter 31

    List of Symbols 31

    Greek Letters 32

    References 32

    4 Agitator Behavior under Gassed Conditions 35

    Flooding 35

    Kla Method 35

    Power Draw Method 36

    Visual Flow Pattern Method 37

    Effect on Power Draw 38

    Holdup 39

    Example of Holdup Calculation 40

    Holdup “War Story” 40

    Variable Gas Flow Operation 40

    Mechanical Effects 42

    Summary of Chapter 42

    List of Symbols 42

    References 43

    5 Impeller Types Used in Fermenters 45

    Impeller Flow Patterns 45

    Axial Flow 46

    Radial Flow 47

    Mixed Flow 47

    Chaos Flow 48

    Examples of Axial Flow Impellers 49

    Low Solidity 49

    High Solidity 52

    Up-pumping vs. Down Pumping 55

    Examples of Radial Flow Impellers 56

    Straight Blade Impeller 56

    Disc, aka Rushton, Turbines 57

    Smith Turbines 62

    CD-6 Turbine by Chemineer; aka Smith Turbine by Many Manufacturers 62

    Deeply Concave Turbines 66

    Deep Asymmetric Concave Turbine with Overhang (BT-6) 68

    Examples of Mixed Flow Impellers 73

    Examples of Chaos Impellers 74

    Shear Effects 76

    Specialty Impellers 78

    Summary of Chapter 80

    List of Symbols 80

    References 81

    6 Impeller Systems 83

    Why Do We Need a System? 83

    Reaction Engineering 83

    Fermenter History 84

    Steps to Impeller System Design 85

    Choose Number of Impellers 86

    Choose Placement of Impellers 86

    Choose Type(s) of Impellers 87

    Choose Power Split or Distribution Among Impellers 93

    Choose D/T and/or Shaft Speed 93

    D/T Effects with Variable Gas Flowrates 96

    Conclusions on D/T Ratio 98

    Design to Minimize Shear Damage 99

    Sparger Design 100

    Ring Sparger 100

    Pre-dispersion 103

    Fine Bubble Diffuser 104

    Summary of Chapter 105

    List of Symbols 106

    References 106

    7 Piloting for Mass Transfer 109

    Why Pilot for Mass Transfer 109

    Methods for Determining kla 112

    Sulfite Method 112

    Dynamic Method; aka Dynamic Gassing/Degassing Method 112

    Steady-State Method; aka Mass Balance Method 113

    Combined Dynamic and Steady-State Method 114

    Equipment Needed for Scalable Data 114

    Data Gathering Needs 120

    Experimental Protocol 121

    Summary of Chapter 128

    List of Symbols 128

    References 129

    8 Power and Gas Flow Design and Optimization 131

    What This Chapter Is about 131

    Where We Are in Terms of Design 131

    Design with no Data 131

    Design with Limited Pilot Data 133

    Design with Full Data 135

    Choose Minimum Combined Power 136

    State of Design Completion 141

    Additional Considerations 142

    Summary of Chapter 142

    List of Symbols 142

    References 142

    9 Optimizing Operation for Minimum Energy Consumption per Batch 145

    Purpose of This Chapter 145

    Prerequisite 145

    Conceptual Overview 145

    Detailed Procedure 146

    Minimizing Total Energy Usage 150

    Practical Design 150

    Additional Considerations 150

    Summary of Chapter 152

    List of Symbols 152

    References 153

    10 Heat Transfer Surfaces and Calculations 155

    Purpose of This Chapter 155

    Design Philosophy 155

    Overview of the Problem 156

    Heat Sources 156

    Cooling Sources 157

    Heat Exchange Surface Overview 158

    Principle of Heat Transfer Calculation 164

    Calculations By Type of Surface 166

    Vessel Jacket, Agitated Side 166

    Simple Unbaffled Jacket, Jacket Side 167

    Dimple Jacket, Jacket Side 167

    Half-Pipe Coil, Jacket Side 169

    Helical Coil, Inside 171

    Helical Coil, Process Side 171

    Vertical Tube Bundle, Inside 173

    Vertical Tube Bundle, Process Side 174

    Plate Coil, Inside 175

    Plate Coil, Process Side 176

    Example Problem: Vertical Tube Bundle 176

    Problem Statement 176

    Problem Solution 177

    Additional Consideration: Effect on Power Draw 182

    Additional Consideration: Forces on Heat Exchange Surfaces Used as Baffles 183

    Additional Consideration: Wall Viscosity 184

    Additional Consideration: Effect of Gas 185

    External Heat Exchange Loops 186

    Summary of Chapter 187

    List of Symbols 187

    References 189

    Further Readings 189

    11 Gasses Other Than Air and Liquids Other Than Water 191

    General Principle 191

    Comments on Some Specific Gasses 191

    Ammonia 191

    Carbon Dioxide 192

    Carbon Monoxide 192

    Hydrogen 192

    Methane 192

    Oxygen 192

    Economic Factors 192

    Disposal Factors 193

    Effects of Different Gasses on kla 193

    Effects of Different Gasses on Driving Force 195

    Operating Condition Effects 195

    Constraints on Outlet Concentration 196

    Safety 196

    Liquids Other Than Water 198

    Summary of Chapter 198

    List of Symbols 198

    References 199

    12 Viscous Fermentation 201

    General Background 201

    Sources of Viscosity 201

    Viscosity Models for Broths 202

    Effect of Viscosity on Power Draw 203

    Example Problem 204

    Example Problem Answer 204

    Effect of Viscosity on kla 205

    Effect of Viscosity on Holdup 207

    Effect of Viscosity on Blend Time 207

    Effect of Viscosity on Flooding 209

    Caverns 209

    Estimating Cavern Size 211

    Xanthan and Gellan Gums 212

    Viscosity Models for Gums 213

    Installation Survey 214

    Effect of D/T and No. and Type of Impellers on Results in Xanthan Gum 217

    Production Curve 218

    Heat Transfer 218

    All-Axial Impeller Design 218

    Invisible Draft Tube vs. Axial/Radial Combination 222

    Mycelial Broths 223

    Typical Viscosity Model 224

    Morphology Effects 224

    Recommendations 225

    Summary of Chapter 227

    List of Symbols 227

    References 228

    13 Three Phase Fermentation 231

    General Problem 231

    Effect on Mass Transfer 231

    Effect on Foam 233

    Emulsion vs. Suspension 233

    Complexity: How to Optimize Operation 233

    Summary of Chapter 234

    List of Symbols 234

    References 234

    14 Use of CFD in Fermenter Design 237

    Purpose of This Chapter 237

    Basic Theory 237

    Methods of Presenting Data 239

    Velocity Distribution 240

    Cavern Formation 240

    Blending Progress 242

    Flow Around Coils 245

    Bubble Size, kla, Holdup 247

    DO Distribution 248

    Summary of Chapter 250

    List of Symbols 250

    References 250

    15 Agitator Seal Design Considerations 251

    Introduction 251

    Terminology 251

    Main Functions of Fermenter Shaft Seals 252

    Common Types of Shaft Seals 254

    Material Considerations 265

    Methods of Lubricating Seals 267

    Seal Environmental Control and Seal Support System 267

    Seal Life Expectations 272

    Special Process Considerations 272

    Summary of Chapter 275

    Reference 275

    16 Fermenter Agitator Mounting Methods 277

    Introduction 277

    Top Entering Methods 277

    Direct Nozzle Mount 278

    Beam Gear Drive Mount with Auxiliary Packing or Lip Seal; Beams Tied into Vessel Sidewall 281

    Beam Gear Drive Mount with Auxiliary Mechanical Seal; Beams Tied into Vessel Sidewall 283

    Beam Gear Drive Mount with Auxiliary Mechanical Seal; Beams Tied into Building Structure 284

    Complete Drive and Seal Mount to Beams Tied into Vessel Sidewall, with Bellows Connector 285

    Complete Drive and Seal Mount to Beams Tied into Building Structure, with Bellows Connector 287

    Bottom Entering Methods 287

    Direct Nozzle Mount 288

    Floor Gear Drive Mount with Auxiliary Packing or Lip Seal 288

    Floor Gear Drive Mount with Auxiliary Mechanical Seal 289

    Floor Integrated Drive and Seal Mount with Bellows Connector 291

    Summary of Chapter 292

    References 292

    17 Mechanical Design of Fermenter Agitators 293

    Introduction 293

    Impeller Design Philosophy 294

    Discussion on Hydraulic Force 295

    Shaft Design Philosophy 297

    Shaft Design Based on Stress 298

    Simple Example Problem 302

    Sample Problem with Steady Bearing 304

    Shaft Design Based On Critical Speed 304

    Cantilevered Designs 306

    Example Problem 308

    Units with Steady Bearings 311

    Solid Shaft vs. Hollow Shaft 315

    Role of FEA in Overall Shaft Design-Simplified Discussion 319

    Agitator Gear Drive Selection Concepts 319

    Early History 320

    Loads Imposed 320

    Handle or Isolate Loads? 323

    Handle Loads Option 1: Oversized Commercial Gear Drive 323

    Handle Loads Option 2: Purpose-Built Agitator Drive 324

    Isolate Loads Option 1: Hollow Quill Integrated Drive with Flexibly Coupled Extension Shaft 325

    Isolate Loads Option 2: Outboard Support Bearing Module 328

    Bearing Life Considerations 329

    Noise Considerations 330

    Torsional Natural Frequency 332

    Important or Useful Mechanical Design Features 332

    Summary of Chapter 333

    List of Symbols 333

    Greek Letters 334

    References 334

    18 Sanitary Design 335

    Introduction 335

    Definitions 336

    Construction Principles 336

    Wetted Parts Construction Methods 336

    Welded Construction 336

    In-Tank Couplings 338

    Mounting Flange Area 341

    Axial Impellers 344

    Radial Impellers 345

    Bolts and Nuts 347

    Steady Bearings 348

    Use of Castings, 3-D Printing 349

    Polishing Methods and Measures1: Polishing vs. Burnishing 350

    Polishing Methods and Measures2: Lay 351

    Polishing Methods and Measures3: Roughness Average 353

    Electropolish 355

    Passivating 357

    Effect on Mechanical Design 357

    Summary of Chapter 357

    Additional Sources of Information 358

    List of Symbols 358

    References 358

    19 Aspect Ratio 359

    Acknowledgment 359

    Definition and Illustration of Aspect Ratio 359

    What Is the Optimum Aspect Ratio? 360

    Effects of Z/T on Cost and Performance at a Given Working Volume 361

    Vessel Cost 361

    Agitator Shaft Design Difficulty 361

    Power Required for Mass Transfer 361

    Agitator Cost 362

    Airflow Requirements 362

    Compressor Power 362

    DO Uniformity 362

    Heat Transfer Capability 363

    Real Estate/Land Usage Issues 363

    Building Codes; Noise 363

    Illustrative Problem Number 1 363

    Vessel Dimensions 364

    Airflow and Power 366

    Heat Transfer Data and Assumptions 367

    Heat Transfer Results 369

    Blend Time, DO Uniformity 371

    Capital Cost (Agitator Plus Vessel Only) 372

    Other Operating Costs 372

    So What Is the Optimum Aspect Ratio for This Problem? 373

    Illustrative Problem Number 2 373

    Illustrative Problem Number 3 376

    Summary of Chapter 380

    List of Symbols 381

    References 381

    20 Vendor Evaluation 383

    Product Considerations 383

    Gear Drive Ruggedness 384

    Design Technology 384

    Impeller Selection 384

    Shaft Design 385

    Company Considerations 385

    Reputation with Customers 385

    Company Size 386

    Years in Business 386

    Years Under New Ownership 386

    Employee Turnover 387

    Vertical Integration 387

    R&D Program and Publications 388

    Depth of Application Engineering 389

    Testing Laboratory 389

    ISO Certification (Necessary vs Sufficient) 391

    Quality Control Program (Not Lot Sample; 100%) 391

    Rep vs Direct Sales (a Good Rep Annoys the Manufacturer) 392

    Service Capability 393

    Typical Delivery Times and Performance 393

    Parts Availability 394

    Price (Least Important) 395

    Willingness to Work with Consultants 395

    Vendor Audit Checklist 396

    Use of an Outside Consultant 397

    Summary of Chapter 399

    List of Symbols 399

    References 400

    A. Appendix to Chapter 20 400

    21 International Practices 401

    Introduction 401

    North America 401

    Vendors 401

    Design Practices 402

    Selling/Buying Practices 402

    Degree of Vertical Integration 403

    Role of Design Firms 403

    R&D 404

    Culture 404

    EU 405

    Vendors 405

    Design Practices 405

    Selling/Buying Practices 405

    Degree of Vertical Integration 406

    Role of Design Firms 406

    R&D 406

    Culture 407

    Japan 407

    Vendors 407

    Design Practices 407

    Selling/Buying Practices 407

    Degree of Vertical Integration 408

    Role of Design Firms 408

    R&D 408

    Culture 408

    China 409

    Vendors 409

    Design Practices 409

    Selling/Buying Practices 411

    Degree of Vertical Integration 412

    Role of Design Firms 412

    R&D 412

    Culture 413

    Summary of Chapter 413

    Cultural Resources 413

    Afterword 415

    Index 417

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