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Moisture Measurement in Paper
Pulp Using Fringing Field Dielectrometry
Kishore Sundara-RajanXiaobei Li
Nick SemenyukAlexander Mamishev
Department of Electrical Engineering,University of Washington, Seattle,USA.
Sensors
, Ene
rgy,
and Automation Laboratory
SE A L
Maver ickTeam
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 2
Outline
Motivation Introduction to FEF Sensors Experimental Setup Experimental Results Data Analysis Conclusion
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 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
Wet End Calendaring Dry end
Sensors
FEF Sensors
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 4
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.
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 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.
Drive
Sense Guard
16 cm
4 cm
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 6
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
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 7
Electrical Measurements
All electrical parameters are near-linearly dependent on moisture concentration.
104
9294
96
2468
10
x 106
Frequency (Hz)Moisture (%)
Ad
mit
tan
ce (
S)
104
9294
96-87.6-87.4-87.2
-87-86.8
Frequency (Hz)Moisture (%)
Ph
ase
(deg
)
104
9294
96
18
19
20
Frequency (Hz)Moisture (%)
Cap
acit
ance
(p
F)
104
9294
965
6
7
x 10-12
Frequency (Hz)Moisture (%)
Co
nd
uct
ance
(m
ho
/Hz)
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 8
Cole-Cole Plots
The phase variation is inadequate to obtain a semi-circle Greater frequency range is required.
0 2 4 6
x 10-7
0
2
4
6
8
10
12x 10
6
Re[Y], [ohms]
Im[Y
], [
oh
ms]
91 %92 %93 %94 %95 %96 %
0 2 4 6
x 10-19
0
0.2
0.4
0.6
0.8
1x 10
-5
Re[Z], [ohms]-I
m[Z
], [
oh
ms]
91 %92 %93 %94 %95 %96 %
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 9
Choice of Parameter
Very small resolution required Higher error
5.2 5.4 5.6 5.8 6 6.2 6.4 6.6 6.8 7 7.2
x 10-12
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
Conductance (mho/Hz)
Mo
istu
re C
on
ten
t (%
)
1.000e+0031.600e+0032.500e+0034.000e+0036.300e+0031.000e+004
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 10
Choice of Parameter
18.8 19 19.2 19.4 19.6 19.8 20 20.24
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
Capacitance (pF)
Mo
istu
re C
on
ten
t (%
)
1.000e+0031.600e+0032.500e+0034.000e+0036.300e+0031.000e+004
Better slope as compared to that of conductance.
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 11
Measurement Accuracy
91 92 93 94 95 96
19.4
19.45
19.5
19.55
19.6
19.65
19.7
Moisture Concentration (%)
Cap
acit
ance
(p
F)
Standard deviation is two orders of magnitude lower than the mean.
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 12
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.
P m C k= × +
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 13
Goodness of Fit
Average normalized error of 1.7%, 2.1% being state of the art.
90 92 94 96 98
90
92
94
96
98
Actual Moisture Content (%)
Es
tim
ate
d M
ois
ture
Co
nte
nt
(%)
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 14
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.
10/23/2003 SEAL Lab, Dept. of EE, University of Washington. 15
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
