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Wet Cake Filtration: Fundamentals, Equipment, and Strategies

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Wet Cake Filtration: Fundamentals, Equipment, and Strategies

Harald Anlauf

ISBN: 978-3-527-82065-8 June 2019 210 Pages

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Description

Guides readers through the entire process of liquid filtrations, from a basic understanding and lab scale testing to advanced process applications and up-scaling of processes

Wet Cake Filtration is a key method in solid-liquid separation and plays an important role in many industrial processes from the separation of solid products from a liquid, to removing contaminants in wastewater treatment. Furthermore, separation processes are rarely isolated and the integration as well as necessary pre-treatments in the process chain must be carefully considered and implemented. Supported by more than 40 years of research, development, and teaching, this book provides a comprehensive treatment of all relevant aspects in wet cake filtration as a key method in solid-liquid-separation.

The first part of Wet Cake Filtration: Fundamentals, Equipment, Strategies discusses general principles and applications of wet cake filtration, determination of proper feed streams, and filter cake formation. The next chapters deal with variations of pre-treatment and process conditions, including necessary aspects of lab scale tests, up-scaling, and filter design. This is further strengthened with chapters examining particle purification, yield maximization, and cake deliquoring. Lastly, the filter media is discussed as the central piece of wet cake filtration. Beside the different possibilities of available filter media structures and process relevant aspects of filter media selection, the reliable characterization of pore sizes by porometry and innovative additional functionalities are introduced.

-Provides information on wet cake filtration?the necessary pre-treatments and process considerations?to guide the reader to develop or improve their own processes
-Offers the necessary tools that allow the engineer to transform a lab scale test into a scaled-up process
-Presents cake filtration process-related topics like slurry characterization or slurry pretreatment, and special developments such as hyperbaric filtration or steam pressure filtration
-Discusses promising new processes like gasless cake desaturation and shrinkage crack free cake desaturation

Wet Cake Filtration is a must-have resource for every engineer working with wet cake filtration, including water chemists, catalytic chemists, food chemists, chemical engineers, biotechnologists, and process engineers.

Preface ix

1 Introduction and Overview 1

1.1 General Aspects of Solid–Liquid Separation in General and Cake Filtration in Detail 1

References 11

2 Slurry Characterization 13

2.1 Introduction 13

2.2 Liquid Properties 14

2.3 Particle Properties 14

2.3.1 General Aspects 14

2.3.2 Characterization of Single Particles 16

2.3.3 Characterization of Particle Collectives 20

2.3.4 Characterization of Particle Collective Fractionation 24

2.4 Slurry 32

2.4.1 Solid Concentration 32

2.4.2 Stability 33

2.5 Sampling 35

References 38

3 Cake Structure Characterization 41

3.1 Introduction 41

3.2 Porosity 42

3.3 Particle Arrangement 49

3.4 Pore Size 52

References 54

4 Characterization of Liquid Flow Through Porous Particle Layers 57

4.1 Introduction 57

4.2 Dimension Analytic Approach for the Flow Through Porous Particle Layers 57

4.3 Empirical Approach for the Flow Through Porous Particle Layers 61

References 63

5 Slurry Pretreatment to Enhance Cake Filtration Conditions 65

5.1 Introduction 65

5.2 Thickening 66

5.3 Agglomeration 70

5.4 Fractionation/Classification/Sorting 75

5.5 Filter Aids – Body Feed Filtration 80

5.6 Thermal Conditioning 83

5.7 Chemical Conditioning 83

References 84

6 Filter Cake Formation 87

6.1 Introduction 87

6.2 Filtration Mechanisms During the Initial Phase of Cake Filtration 88

6.3 Formation of Incompressible Filter Cakes by Pressure Filtration 94

6.3.1 Principle Model of Time-Dependent Filter Cake Growth 94

6.3.2 Experimental Determination of Process Characterizing Parameters 98

6.3.3 Throughput of Discontinuous Cake Filters 104

6.3.4 Throughput of Continuous Vacuum and Pressure Filters 108

6.3.5 Aspects of Filter Design and Operation Regarding Cake Formation and Throughput 113

6.4 Formation of Compressible Filter Cakes by Pressure Filtration 123

6.4.1 Fundamental Considerations Regarding Compressible Cake Filtration 123

6.4.2 Experimental Determination of Process Characterizing Parameters 130

6.4.3 Optimization of Compressible Cake Filtration 133

6.4.4 Aspects of Filter Design and Operation Regarding Cake Formation and Throughput 136

6.5 Formation of Filter Cakes in Centrifuges 146

6.5.1 Fundamental Considerations Regarding Cake Filtration in Centrifuges 146

6.5.2 Aspects of Centrifuge Design and Operation Regarding Cake Formation and Throughput 152

References 169

7 Particle Washing 175

7.1 Introduction 175

7.2 Principles of Particle Washing 176

7.3 Limits of Particle Washing Processes 178

7.4 Characterization of Particle Washing Results 180

7.5 Dilution Washing 182

7.6 Permeation Washing 186

References 201

8 Filter Cake Deliquoring 203

8.1 Introduction 203

8.2 Characterization of Deliquoring Results 206

8.3 Desaturation of Filter Cakes 208

8.3.1 Boundary Surface and Surface Tension 208

8.3.2 Three-Phase Contact Line, Contact Angle, and Wetting 215

8.3.3 Capillary Pressure and Capillary Pressure Distribution 222

8.3.4 Desaturation of Incompressible Filter Cakes by Gas Pressure Difference 231

8.3.4.1 Equilibrium of Cake Desaturation with a Gas Pressure Difference 231

8.3.4.2 Kinetics of Filter Cake Desaturation with Gas Pressure Difference 234

8.3.4.3 Kinetics of Gas Flow through Filter Cakes and Energetic Considerations 240

8.3.4.4 Measurement of Cake Desaturation Equilibrium and Kinetics 246

8.3.4.5 Transfer of Desaturation Results from Bench Scale to Rotary Filters 248

8.3.4.6 Interrelation of Throughput, Cake Moisture, and Gas Consumption for Rotary Filters 251

8.3.5 Desaturation of Incompressible Filter Cakes by Steam Pressure Difference 257

8.3.6 Desaturation of Incompressible Filter Cakes in the Centrifugal Field 261

8.3.6.1 Equilibrium of Filter Cake Desaturation in the Centrifugal Field 261

8.3.6.2 Kinetics of Filter Cake Desaturation in the Centrifugal Field 267

8.3.6.3 Aspects of Centrifuge Design and Operation Regarding Cake Deliquoring 268

8.4 Consolidation of Compressible Filter Cakes by Squeezing 271

8.4.1 Fundamental Considerations Regarding the Consolidation Process 271

8.4.2 Aspects of Filter Design and Operation Regarding Cake Consolidation 274

8.5 Consolidation/Desaturation of Compressible Filter Cakes by Gas Differential Pressure 278

8.5.1 Equilibrium of Filter Cake Consolidation/Desaturation 278

8.5.2 Cake Shrinkage and Shrinkage Cracking 285

8.5.3 Prevention of Shrinkage Cracks by Squeezing and Oscillatory Shear 288

8.6 Electrically Enhanced Press Filtration 292

References 293

9 Selected Aspects of Filter Media for Cake Filtration 299

9.1 Introduction and Overview 299

9.2 Woven Filter Media for Cake Filtration 304

9.3 Porometry – Using Capillarity to Analyze Pore Sizes of Filter Media 310

9.3.1 Introduction 310

9.3.2 Methods of Pore Size Determination 312

9.3.3 Theoretical Approach to Correlate Bubble Point and Largest Penetrating Sphere 315

9.3.4 Experimental Validation of the Theoretical Findings 318

9.4 Semipermeable Filter Media – Gas Pressure Filtration Without Gas Flow 321

9.4.1 Introduction 321

9.4.2 Concept of Gasless Filtration on Vacuum Drum Filters and Physical Background 322

9.4.3 Realization of the Process in Lab and Pilot Scale 325

References 330

Nomenclature 333

Index 341