Table of Contents

Food Extrusion Process Scale-Up & Process Transfer

SECTION 1: Basic Principles of Extrusion Processing, Scale-Up & Dimensional Analysis

1. Basic Principles of Extrusion Processing & Scale-Up
1. Introduction
1.1 Extrusion Cooking Technology
1.2 Process Scale-Up & Process Scale-Down

2. A Review of Basic Extrusion Cooking Theory – The Four Golden Rules
2.1 Introduction
2.2 What is Product Quality?
2.3 A Review of the Extrusion Process
2.4 Flow Components in an Extruder Screw
2.5 The Steady-State Operation of an Extrusion System
2.6 The Role of the Energy Inputs
2.7 A Simple Analogy for Extruder Performance
2.8 The Interactive Nature of the Extrusion Process

3. Modelling & Measuring the Degree of Cook in Extrusion Technology
3.1 Introduction
3.2 Modelling the Gelatinisation Process
3.3 Modelling the Extrusion Cooking Process
3.4 Gelatinisation vs. Cooking
4. The Development of Optimal Screw Profiles
4.1 Introduction
4.2 Classification of the Performance Characteristics of Alternative Screw Elements
4.3 Calculation of the Performance Characteristics of Alternative Screw Geometries
4.4 Comparison of Alternative SSE
4.5 Comparison of Screw Elements
4.6 Evaluation of a Proposed Screw Profile
4.7 Basic Considerations When Preparing a Screw Profile

5. Potential Limitations to the Scale-Up of Extrusion Processes
5.1 Introduction
5.2 Reducing Risk in Process Commercialisation
5.3 An Overview of Some of the Important Considerations for Extruder Scale-Up
5.4 Compromises in Process Scale-Up: Examples of Limited Processes
5.4.1 Barrel Heat Transfer
5.4.2 Energy Transfer Scale-Up Limitations
5.4.3 Feed Intake Scale-Up Limitations
5.4.4 Surface Renewal Scale-Up Limitations (Devolatilisation or Venting)
5.4.5 Process Instabilities
5.5 Final Comments

6. An Introduction to the Principles of Dimensional Analysis
6.1 Introduction
6.2 Primary Criteria & Secondary Criteria
6.3 Physical Properties & Dimensions
6.4 Application of the Fundamental Method
6.5 Application of the Rayleigh Method
6.6 Application of the Buckingham π Theorem
6.7 Common Dimensionless Groups
6.8 The Basic Laws of Similitude
6.9 Completion of the Dimensional Analysis
6.10 The Limitations of Dimensional Analysis
6.11 A Brief Summary of the Application of the Principles of Dimensional Analysis

SECTION 2: Quantification of the Raw Materials, the Product & the Process

7. Quantification of the Extrusion Process – Raw Materials & Product Specifications
7.1 The Many Applications of Extrusion Cooking Technology
7.2 Defining the Proximate Composition of Raw Materials & Products
7.3 Thermal Properties of the Formulation & the Melt
7.4 Finished Product Attributes (Physical)
7.5 Additional Product Attributes
7.6 Linking the Rheology, Extrusion Cooking & Extruded Product Quality
7.6.1 Background Theory for Rotational Rheometers
7.6.2 Background Theory for the Use of Pasting Rheometers
7.7 Determining Product Colour
7.8 Measurement of Product Texture

8. Quantification of the Extrusion Process – The Mass & Energy Balance
8.1 Introduction
8.2 Some Basic Concepts
8.3 Mass Balances
8.4 Energy Balances
8.4.1 The Concept of Heat
8.4.2 The Concept of Enthalpy
8.4.3 Adiabatic Processes
8.4.4 Isothermal Processes
8.5 Understanding the Equivalence of Electrical & Mechanical Energy
8.6 Understanding the Energy Losses From an Extruder
8.7 Completion of Mass & Energy Balances for Extrusion Systems
8.7.1 Calculation of Heat Capacity
8.7.2 Mass & Energy Balance for the Preconditioner
8.7.3 Mass & Energy Balance for the Extruder
8.7.4 Barrel Heat Transfer
8.7.5 Special Cases & Considerations
8.8 Benefits of Performing a Mass & Energy Balance

9. Weighted Average Total Strain (WATS)
9.1 Introduction
9.2 Extruder Residence Time Distributions
9.3 Extruder Shear Rate & Shear Strain
9.4 Total Strain in the Extruder Die
9.5 The Relationship Between Shear Strain & the Total Energy Input

SECTION 3: Process Scale-Up & Process Transfer Methodologies

10. The General Requirements for Extrusion Process Scale-Up
10.1 Introduction
10.2 Process Scale-Up: Before You Start
10.3 Completing “Sensible” Extrusion Experiments
10.4 Initial Considerations for Extrusion Scale-Up
10.4.1 Comparative Machine Geometry
10.4.2 Comparative Operating Conditions
10.4.3 Comparative Residence Time Distribution
10.5 Further Considerations for Extrusion Scale-Up
10.6 Quantifying the Energy Inputs
10.7 Extrusion Scale-Up via Process Optimisation

11. Scale-Up for Heat Transfer Controlled Extrusion Processes
11.1 Introduction
11.2 An Analysis of the Role of Viscous Dissipation in an Extruder
11.3 Order of Magnitude Calculations for Extruder Barrel Heat Transfer
11.4 Simple Methods for Scale-Up for Constant Heat Transfer
11.4.1 Method of Rauwendaal
11.4.2 Scale-Up Rule for Low Shear Single Screw Extruders

12. Scale-Up for Mixing in Extrusion
12.1 Defining the Mixing Process
12.1.1 Distributive Mixing
12.1.2 Dispersive Mixing
12.2 Understanding the Role of Laminar Mixing
12.3 Scale-Up for Mixing
13. Scale-Up via Empirical Models
13.1 Introduction
13.2 A Simple Model for Standard Extruder Geometries (SSE & TSE)
13.3 Simple Models for Non-Standard Extruder Geometries (SSE & TSE)
13.4 Scale-Up via the Method of J.M. Harper
13.5 Simplified Scale-Up Rules

14. Scale-Up via Supplier Data & Recommendations
14.1 Introduction
14.2 Wenger Manufacturing
14.3 Brabender
14.4 Baker-Perkins Extruders
14.5 Thermo-Scientific
14.6 Clextral Extruders
15. Scale-Up of Extruders via Dimensional Analysis
15.1 Introduction
15.2 The Ideal Screw Model

SECTION 4: Application of the Principles of Dimensional Analysis in Extrusion Processing

16. Use of Dimensional Analysis – The Operational Characteristics of Extruders
16.1 Introduction
16.2 Use of the Ideal Screw Model
16.3 Alternative Models for the Screw Conveying Characteristics
17. Use of Dimensional Analysis - The Scale-Up of Extrusion Dies
17.1 Strain within the Die
17.2 Modelling Die Output Capacity
17.3 Die Pressure Drop – The Die Entrance Effect
17.4 Calculating the Die Pressure Drop (The Resistance Factor Method)
17.5 A General Procedure for the Scale-Up of Extrusion Dies

18. The Use of Dimensional Analysis - The Prediction of Product Bulk Density
18.1 Introduction
18.2 The Product Expansion Process
18.3 Elastic Effects & Die Swell
18.4 Process Control & Product Expansion
18.5 Application of Dimensional Analysis to Predict Product Bulk Density
19. Use of Dimensional Analysis – The Extruder Venting Process
19.1 Introduction
19.2 Dimensional Analysis of Extruder Venting
19.3 A Simplified Model for the Venting Section
19.4 Some Comments Regarding the Scale-Up & Operation of the Venting Process

SECTION 5: Application of the Principles of Extrusion Process Scale-Up

20. Scale-Up of Single Screw Extruders – Pasta Press Scale-Up
20.1 Introduction
20.2 The Pasta Extrusion Process
20.3 Impact of Process Interactions on the Product Quality
21. Scale-Up of Twin Screw Extruders – The Manufacture of Crisp Bread
21.1 Background
21.2 Process Description
21.3 Product Quantification

Appendix 1 - Application of the Buckingham π Theorem
The Buckingham π Theorem

Appendix 2 - Rules of Thumb for Dimensional Analysis
A Summary of the Application of the Principles of Dimensional Analysis
The Do’s & Don’ts of Process Scale-Up
Rules of Thumb for Dimensional Analysis
Basic Rules for Extruder Scale-Up

Appendix 3 - A List of Common Dimensionless Groups

Appendix 4 - A List of Dimensionless Groups for the Analysis of Extrusion Technology

Appendix 5 - Estimation of Material Thermal Properties

Nomenclature & Symbols

Technical References

Index