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?