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| Application
of the Month |
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Moisture
Measurement of Wood Chips using Microwave and Radiometric
Technologies |
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Berthold LB 456
MicroMoist with
Density Compensation
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| Non-contacting,
non-intrusive technology for accurate measurement of wood chips
on a conveyor belt. |
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A major pulp and
paper producer processes both hard and soft wood chips at the
same location, and had tried several on-line moisture systems
(infrared, neutron backscatter, etc.), and nothing seemed to
work. They wanted to measure the moisture in their wood chips to
control the addition of white liquor to their Kamyr digesters.
There are three belts at this location, two for soft wood
(mostly pine) and one for a hard wood mix. The following are
some of their specs: |
- Belt speed is 380
feet/min.
- Belt material is
rubber
- Belt width is 30
inches
- Wood chip bed depth is
between 3 to 6 inches
- Particle size 7/8 X 7/8 X
1/8 inches
- Moisture range: 40 to 55
%
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The company
purchased a Micro-Moist System, and it was installed on the hard
wood chip belt . This belt was chosen because they will run both
types of wood on it. Spiral horns were used as well as
radiometric mass compensation. Over the next two months the
Micro-Moist was operating on both hard and soft wood chips and
data was collected for fine tuning the calibration. In May it
was decided to have two separate calibrations, one for hard wood
and one for soft. The system operated without problem. The
accuracy of the Micro-Moist on hard wood chips was better than +
/- 1 %. Based upon initial results on soft wood, the expected
accuracy would be between 1 to 1. 5 %, which is very acceptable.
The 4 to
20 mA signal from the Micro-Moist is connected to their
Honeywell distributed control system and is controlling the
addition of white liquor to the digester. They have improved
their Kappa number by better than 0.2. This company has since
purchased two additional Micro-Moist systems for soft wood
chips. |
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For literature on the LB 456
MicroMoist Click Here. |
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