Moisture Measurement in Paper Pulp Using Fringing Field Dielectrometry

1
Moisture Measurement in Paper Pulp Using Fringing
Field Dielectrometry

• Kishore Sundara-Rajan
• Xiaobei Li
• Nick Semenyuk
• Alexander Mamishev
• Department of Electrical Engineering,
• University of Washington, Seattle,USA.

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Outline

• Motivation
• Introduction to FEF Sensors
• Experimental Setup
• Experimental Results
• Data Analysis
• Conclusion

3
Motivation

• Annual worldwide paper production is nearly 312
  million tons ? Huge application market.
• Machine controlled using feedback systems ?
  Stable, but slow.

• 10 sec delay on a 2000 m/min machine leads to
  over 0.2 miles of bad quality paper !!
• Solution Incorporate Feed Forward Control

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Fringing Field Interdigital Sensor

• For a semi-infinite homogeneous medium placed on
  the surface of the sensor, the periodic variation
  of the electric potential along the X-axis
  creates an exponentially decaying electric field
  along the Z-axis, which penetrates the medium.

5
Experimental Setup

• Pulp is blended using a blender to a consistency
  of a suspension.
• Sensor is attached to the outer side of the base
  of an acrylic tray.
• A guard plane is placed underneath the sensor
  electrodes to provide shielding from external
  electric fields.

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Experimental Setup

• Sensor Used
• Spatial Wavelength 40 mm
• Finger Length 160 mm
• Penetration Depth 8 mm
• Wall thickness of the tray 5 mm
• RCL Meter (Fluke Manufactured, Model PM6304)
• Single Channel Measurements
• One Volt RMS Sinusoidal AC Voltage
• 50 Hz to 100 kHz Frequency Range

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Electrical Measurements

• All electrical parameters are near-linearly
  dependent on moisture concentration.

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Cole-Cole Plots

• The phase variation is inadequate to obtain a
  semi-circle ? Greater frequency range is required.

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Choice of Parameter

• Very small resolution required ? Higher error

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Choice of Parameter

• Better slope as compared to that of conductance.

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Measurement Accuracy

• Standard deviation is two orders of magnitude
  lower than the mean.

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Data Fitting

• m is the slope ( / pF)
• k is the offset ()
• C is the measured capacitance (pF)
• P is the estimated moisture content ()
• m and k are determined by least square fit.

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Goodness of Fit

• Average normalized error of 1.7, 2.1 being
  state of the art.

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Conclusion

• The ability of the sensor to accurately measure
  moisture concentration of paper pulp, even in the
  presence of additives, was demonstrated.
• The algorithms were developed to estimate the
  concentrations of the constituents of the pulp.
• The measurements and the estimation algorithms
  were validated.

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Acknowledgements

• A special thanks goes out to

• Sponsors
• Centre for Process Analytical Chemistry, UW
• Electric Energy Industrial Consortium, UWEE
• National Science Foundation
• Undergraduate Research Assistants
• Leslie Byrd II
• Nick Semenyuk
• Cheuk Wai-Mak
• Alexei Zyuzin