Date post: | 13-Dec-2015 |
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Sorting Technologies for CCA Treated Wood
Objective
To design and implement an automated system to effectively sort CCA treated wood from other wood types at facilities such as C&D
facilities
Automated System
• Designed using x-ray fluorescence technology
or
• Designed using laser induced breakdown spectroscopy technology
Motivation• CCA treated wood => ~ 6 % of all wood waste
at C&D facilities
• Amounts of CCA treated wood at C&D facilities increasing
• At 6 % level, cannot be used as mulch or burned to generate fuel
Sorting Studies• Chemical stain method
– laboratory results– field results from pilot studies
• X-ray fluorescence (XRF)– laboratory results
• Laser Induced Breakdown Spectroscopy (LIBS)– laboratory results
• Automated System– X-ray fluorescence– Laser induced breakdown spectroscopy
• Training and monitoring– chemical stains
Chemical Stains
• Chrome Azurol S
• PAN Indicator
• Rubeanic Acid
Performance on whole wood0.25 pcf 0.6 pcf 2.5 pcf
Laboratory Results• Colors get darker with increasing retention
levels
• Chrome Azurol and PAN indicator performed best:
• colors not usually found in C&D waste materials• reacted fastest and easy to apply
• Rubeanic acid:• green color could be mistaken for other material• inconvenience of spraying with two different
solutions
Field Studies
• Performed to determine if chemical stains could be used at C&D facilities to sort CCA treated wood from other wood types
• Three facilities studied
Findings from Field Studies• PAN indicator and Chrome Azurol S performed
best
• Time and labor intensive
• Assumed untreated wood waste piles contained
9 % to 30 % of CCA treated wood
• CCA treated wood found mostly in construction type debris
• Demolition debris contains increasing amounts of CCA treated wood
Current Practical Applications
• Sorting Small Quantities of Treated from Untreated Wood
• Screening Fuel Quality
• Training Tool
Design for Shelter
Detector Mounting Design
XRF
• Based on emission of x-rays
• Characteristic x-ray emitted by the element is read by the instrument
Model 400
• No special training required
• User friendly
• Printout or output easy to read and understand
Head
Analyzer
XRF Instruments
• Low maintenance, few consumables, easy cleaning
• No repetitive calibration necessary
(6 mo. to 2 yrs.)
• Life span of 10 years
XRF Instrument
• Cost range from $20,000 - $100,000
• Detector replacement cost of $1,800 - $2,400
(life span of 5 years)
• Licensing may be required
• Sensor protected by a small beryllium window
($100 for replacement)
Results of XRF Studies• Arsenic is the best indicator metal, although
all three metals can be analyzed for
• Optimum count time of 2 seconds, would be even less for on-line analysis
1,800 ft/hr for detection of 1-ft board (2 s)
3,600 ft/hr for detection of 1-ft board (1 s)
• Detection of CCA for Model 400 is possible at 1 inch distance with a plastic shield
LIBS
• Based on creation of microplasma by the use of a high-power laser
• A signal from emitted light transmitted to a detector
LIBS Instruments• Detectors
– Continuum Minilite ($50,000)• More sensitive• Monitors one element at a time
– Ocean Optics ($2,000)• Not as sensitive• Monitors more than one element at a time
• Laser
LIBS Instruments
• Flash lamp replacement cost of ~ $1,000 (replacement every 3 to 6 months)
• No licensing required
LIBS Results
• Elements with higher wavelength more sensitive to analysis– Chromium (425 nm): detected– Copper (327nm and 324 nm): detected, smaller
signal– Arsenic (200 nm): not detected
• Chromium best indicator metal
LIBS Results
• Shortest analysis time 1/5 of a second (200 ms)
4,500 ft/hr for detection of 1-ft board
• Spacing detector and wood being analyzed could be 12 “
Air
Conveyor Belt
Air-Tight Box
Laser
Lens Mirror
Puff of Air
Laser BeamUp to 12”
Detector
To PC
Glass
Window
Fiber-optic Cable
Questions?