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Acknowledgements
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3
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Contents
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9
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List of Figures
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13
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Abbreviations and Notations
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19
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Introduction
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21
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1
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Electrostatic Separation Processes: Control Variables and Measurement Techniques
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25
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1.1
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Electrostatic separation: a multifactor process
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26
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1.1.1
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Roll-type corona-electrostatic separation
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26
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1.1.2
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Free fall tribo-electrostatic separation
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28
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1.2
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Measurement techniques for electrostatic processes
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32
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1.2.1
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Charge measurements
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33
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1.2.2
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High voltage measurements
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34
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1.2.3
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Surface potential measurement
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35
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1.3
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Virtual instruments
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38
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1.3.1
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Data acquisition techniques
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39
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1.3.2
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Graphical programming
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39
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1.3.3
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Developing virtual instruments in LabVIEW
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40
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2
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Charge Measurements of Finely Divided Matter
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43
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2.1
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Charge of insulating particles
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43
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2.1.1
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Experimental set-up for measuring the charge of insulating particles in roll-type corona separators
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46
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2.1.2
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Virtual instrument for single particle charge measurement
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47
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2.1.3
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Discharge of insulating particles on the surface of the grounded roll electrode of a corona separator
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54
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2.2
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Charge of insulating powders
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59
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2.2.1
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Experimental setup for measuring the tribocharge of insulating powder
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59
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2.2.2
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Virtual instrument for powder charge measurements
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62
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2.2.3
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Variables that express the charge of insulating powders
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64
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2.3
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Statistical control of tribocharging processes
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67
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2.3.1
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Capability of a tribocharging device
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69
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2.3.2
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Charts for the statistical control of a tribocharging process
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72
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2.3.3
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Monitoring tribocharging processes - perspectives
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76
|
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Conclusions to Chapter 2
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77
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3
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Surface Potential Measurement of Insulating Granular Layers
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79
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3.1
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Surface potential of insulating granular layers
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80
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3.1.1
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Experimental set-up for surface potential measurements of charged insulating granular layers
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80
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3.1.2
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Virtual instrument for surface potential decay measurement
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83
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3.1.3
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Surface potential decay of charged insulating granular layers
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84
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3.2
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Charge decay characteristics of insulating granular layers at the surface of grounded electrodes
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86
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3.2.1
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Discharge of insulating particles in contact with a grounded electrode
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86
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3.2.2
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Charge decay as function of the nature of the granular material
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89
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3.2.3
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Charge decay as function of ambient conditions
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92
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3.3
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Method for evaluating the feasibility of corona-electrostatic separation of granular insulators
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94
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3.3.1
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Experimental procedure
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95
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3.3.2
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Surface potential decay of HDPE and PVC granular layers
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96
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3.3.3
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Corona-electrostatic separation of PE and rubber
|
101
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Conclusions to Chapter 3
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103
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4
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High Voltage Measurement in Corona Electrostatic Separators
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105
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4.1
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High-voltage energizing of corona electrodes
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106
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4.1.1
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Experimental set-up for measuring the high voltage in corona separators
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107
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4.1.2
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Spark discharge monitoring
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108
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4.1.3
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High-voltage supply response to spark discharges
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109
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4.2
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High-voltage sensing of the metal content in granular mixtures
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112
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4.2.1
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Virtual instrument for high voltage measurements
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114
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4.2.2
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Statistical analysis of high-voltage measurement data
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115
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4.3
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Measurement of low metal contents in granular mixtures using a high-voltage sensor
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123
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4.3.1
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High-voltage signal processing
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124
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4.3.2
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Monitoring metal content in granular mixtures processed by electrostatic separation
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127
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Conclusions to Chapter 4
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133
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5
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Modelling Metal / Insulator Separation Process
|
135
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5.1
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A linear-interaction model for electrostatic separation processes
|
136
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5.1.1
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Problem formulation using Taguchi methodology
|
137
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5.1.2
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Experimental implementation of Taguchi methodology
|
144
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5.1.3
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Interpreting the linear-interaction model
|
147
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5.2
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Robust control of electrostatic separation processes
|
150
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5.2.1
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Taguchi's approach to robust design
|
151
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5.2.2
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Experimental setup and results
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154
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5.2.3
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Model for a robust electrostatic separation process
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157
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5.3
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Effect of ambient humidity on the outcome of electrostatic separation processes
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161
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5.3.1
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Formulation of the robust design problem
|
162
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5.3.2
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The classic analysis approach
|
166
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5.3.3
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The interaction analysis approach
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168
|
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Conclusions to Chapter 5
|
175
|
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Conclusion and Contributions
|
177
|
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References
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181
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Appendix A: Charge measurements: LabVIEW instrument implementation
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197
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Appendix B: Discharge graph identification: results for insulating particles on a grounded plate
|
203
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