The Science and Engineering of Granulation Processes

Transcription

1 The Science and Engineering of Granulation Processes JIM LITSTER The University of Queensland, Brisbane, Australia BRYAN ENNIS E&G Associates, Nashville, Tennessee, U.S.A. and LIAN LIU (Associate Editor) The University of Queensland, Brisbane, Australia KLUWER ACADEMIC PUBLISHERS DORDRECHT / BOSTON / LONDON

2 CONTENTS Preface vii 1 Introduction Granulation Rate Processes Considering a Granulator as a Reactor Granulation as Particle Design How To Use This Book 9 2 Particle and Granule Morphology 2.1 Particle Size, Shape and Size Distribution Particle Size Definitions Particle Shape Basic Particle Size Distribution Definitions Different Ways to Represent Particle Size Distributions Measures of Mean Size and Spread of the Size Distribution Particle Size Measurement Particle Size Summary Density, Porosity and Pore Size Distribution Density and Porosity Definitions Density Measurement Porosity and Pore Size Distribution Measurement Granule Properties Granule Size Distribution Porosity and Granule Density Wet Granule Morphology Granule Performance Properties Summary 2.5 Bibliography Nomenclature 3 Wetting, Nucleation and Binder Distribution 3.1 Powder Surface Properties Some Definitions Methods of Measurement Wetting and Nucleation Regimes for Granulation Drop Penetration into Powder Beds Analysis of the Spray Zone in Granulators- the Dimensionless 59 Spray Flux A Nucleation Regime Map Related Studies on Wetting and Nucleation Control of Wetting and Nucleation for Particle Design 68 ix 40

3 3.3.1 Adhesion Tension Control Other Powder and Liquid Properties Spray Distribution Agitation Intensity Simultaneous Drying Concluding Comments Bibliography 72 4 Consolidation, Coalescence and Growth 4.1 Granule Mechanics Measuring the Dynamic Yield Stress of a Particle Assembly Granule Consolidation A Mechanistic Understanding of Granulation Effect of Formulation Properties and Process Conditions 86 on Consolidation Granule Consolidation with Simultaneous Drying Theoretical Models for Consolidation Granule Coalescence Criteria for Near Elastic Particles Growth Regimes for near Elastic Granules Estimating the Characteristic Collision Velocity Examples of Application of the Stokes Regime Analysis Limitations of the Stokes Regime Analysis and Final Remarks Granule Coalescence Criteria for Deformable, Porous Granules Development of Coalescence Criteria Implications of the Coalescence Criteria Extension to Surface Dry Granules Comparison with Laboratory Granulation Data Summary Granulation Behaviour for Deformable Granules: A Growth Regime 107 Map 4.6 Control of Growth and Consolidation for Particle Design Elastic Granule Systems Deformable Granule Systems Bibliography Nomenclature Breakage and Attrition 5.1 Breakage of Wet Granules Experimental Observations Predicting Conditions for Breakage Controlling Granule Attributes through Breakage Attrition and Fracture of Dry Granules Fracture Properties of Dry Granules Measurements of Fracture Properties Empirical Crush Strength and Attrition Tests Breakage Mechanisms for Dry Granules Case Study - Fluid Bed Attrition of Agglomerates 134

4 XI 5.3 Particle Design for Controlling Attrition and Breakage Effect of Process Variables Effect of Formulation Properties Controlling Granule Dispersibility Concluding Comments Bibliography Nomenclature Mathematical Modelling of Agglomeration Processes 6.1 Derivation of the Macroscopic Population Balance Moments of the PB Kinetic Expressions for Granulation Rate Processes Nucleation Layering Coalescence Consolidation Attrition and Breakage The Complete Population Balance for Granulation Solution of the Population Balance Equation Analytical Solutions Numerical Solutions Example Applications of the Population Balance Growth by Layering ' Growth by Coalescence Effect of Mixing in the Granulator Summary ' References ' Nomenclature '^0 7 Classification and Choice of Size Enlargement Equipment 7.1 Classification of Size Enlargement Equipment ' Future Directions in Granulation Process Equipment Bibliography Tumbling Granulation 8.1 Introduction 8.2 Disc Granulators Granule Hold Up, Mixing and Segregation on the Disc Drum Granulators l Granule Hold Up, Mixing and Segregation Granulation Drum Circuits ' Granulation Rate Processes ' Nucleation Consolidation l Granule Growth by Coalescence Layering

5 Xll 8.5 Scale Up and Operation of Tumbling Granulators Variations on a Theme Bibliography Nomenclature Fluidised Granulators 9.1 Hydrodynamics of Fluidised Beds Minimum Fluidisation Velocity and Pressure Drop Types of Fluidisation Behaviour The Role of Bubbles in Fluidised Beds Mass and Energy Balances Granulation Mechanisms and Rate Processes Nucleation Coalescence Layering Consolidation Attrition Summary Scale Up of Fluidised Bed Granulators Operation of Fluidised Bed Granulators Draft Tube and Spouted Bed Coaters Concluding Comments Bibliography Nomenclature Mixer Granulators 10.1 Introduction Description of Mixer Granulation Equipment High Shear Mixer Granulators Low Shear Mixer Granulators Powder Flow in Mixer Granulators Powder Flow in a Vertical Shaft Mixer Powder Flow in Horizontal Axis Lodige Granulator Granulation Rate Processes in Mixer Granulators Wetting and Nucleation 230 Case Study Consolidation and Growth Granule Breakage Scale Up of Mixer Granulators Scale Up of a Vertical Shaft Mixer 238 Case Study Instrumentation and Control in Mixers Summary Bibliography Nomenclature 247 Index 249