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Published byLucinda Andrea Edwards Modified over 9 years ago
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Sorting Technologies for CCA Treated Wood
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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
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Automated System Designed using x-ray fluorescence technology or Designed using laser induced breakdown spectroscopy technology
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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
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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
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Automated System –X-ray fluorescence –Laser induced breakdown spectroscopy Training and monitoring –chemical stains
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Chemical Stains Chrome Azurol S PAN Indicator Rubeanic Acid
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Performance on whole wood 0.25 pcf 0.6 pcf 2.5 pcf
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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
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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
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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
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Current Practical Applications Sorting Small Quantities of Treated from Untreated Wood Screening Fuel Quality Training Tool
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Design for Shelter
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Detector Mounting Design
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XRF Based on emission of x-rays Characteristic x-ray emitted by the element is read by the instrument
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Model 400 No special training required User friendly Printout or output easy to read and understand Head Analyzer
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XRF Instruments Low maintenance, few consumables, easy cleaning No repetitive calibration necessary (6 mo. to 2 yrs.) Life span of 10 years
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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)
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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
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LIBS Based on creation of microplasma by the use of a high-power laser A signal from emitted light transmitted to a detector
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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
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LIBS Instruments Flash lamp replacement cost of ~ $1,000 (replacement every 3 to 6 months) No licensing required
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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
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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 “
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Air Conveyor Belt Air-Tight Box Laser Lens Mirror Puff of Air Laser Beam Up to 12” Detector To PC Glass Window Fiber-optic Cable
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