Sorting Technologies for CCA Treated Wood

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

Current Practical Applications

• Sorting Small Quantities of Treated from Untreated Wood

• Screening Fuel Quality

• Training Tool

Wood Encountered at C&D Facilities

Design for Shelter

Cost Estimate - Shelter

• Trident $9,600 - $11,500

Update on Building

• Tasks & Timeline

• Current Contacts

30’

7’

3’

4’

2’

14’

5’ 18’40’

Inp ut Wo o dSto ra g e

Pile

Tre a te dPile

Untre a te dPile

De te c to rC o nve yo rWo o d Inp ut

Untre a te d Wo o d

C o ntro l Ro o m

Wind o w

30’

15’

7’ 3’ 4’ 16’

ControlRoom

ClosedIn

WoodPile

ConveyorDetector

Team ReviewsDesign

Building ContractorDevelops Design

Drawing

2 Wk

1 Wk

4-6 Wks

3 D

Building ContractorSeals Building Design

Building Fabrication

1 Wk

Get Building ContractorUnder Contract

? Wks

Apply for Permit

Concrete Slab

Erect Building

Timeline

Building Contractors Contacted

• Trident -- Met with on June 7• Estimate: $9,600 - $11,500

• Anderson and Ellis Construction• Job too small

• Bob Howard Construction– Contacted

• John F. Swift, Inc.– Contacted

Concrete Contractors Contacted

• Fred Derr Concrete

• Prestige Concrete

• John F. Swift

Initial Detector Mounting Design

Conveyor Design #1

Table

Wood Piece

Movable holding arm

Top View

Wood Piece

Table

Movable holding arm3/4 “ to 2”

Cross-Sectional View

X-rays

Detector mounting

Movable holding arm

Wood Piece

Conveyor Surface

Cost Estimates – Conveyor

• American Conveyor, Miami $11,038

• Powerscreen, Lakeland $24,500

Conveyor Design #2

Table

Holding arm

X-ray

Wood

Top View

Wood

Table

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

X-Ray Technology

• Analysis Time < 2 seconds

• Best Metal for Analysis, As

• Largest Separation Between Sample and Detector is 1 inch

XRF - Collaboration

• ASOMA Inc (1 inch diameter face & strip model)

• Jordan Valley (Hand-held unit, 3 in x 3 in face)

Laser Technology

• Analysis Time < 1 second

• Best Metal for Analysis, Cr

• Tolerance, 12 inches

On-line Sorting Technologies

Custom LIBS Commercial XRF(Asoma)

Custom XRF

Cost $36K $20 to $30K $100K

Detection As, Cr, Cu As, Cr, Cu As, Cr, Cu

Analysis time 3 ms @ 10 Hz 50 to 100 s 100 to 500 ms

Spatial resolution(1 ft/sec)

Point1.25" samples

Start/stop mode Continuous2.5" to 12" samples

Standoff distance(Detector-to-wood)

Variable10-12" window

FixedNear contact

~FixedClose proximity

Other issues Laser beam X-ray source X-ray source

Maintenance $400 flashlamp~35 weeks

- - X-ray tube

Laser-induced Breakdown Spectroscopy (LIBS)

Pulsedlaser

Laser-inducedplasma

Atomicemissioncollection

Spectrometer Detector

Wavelength (nm)

Inte

nsity

205 210 215 220 225 230 235 240 245

Cd

Cd

Cd

Be

Line intensity providesspecies concentration

Line position providesspecies identification

Fiberoptic

Sample Configuration of LIBS Probe

Spectrometer/Detector

Collection Optics Assembly

Plasma

Nd:YAGLaser

To LaptopComputer

WoodSample

Experiments with LIBS

• Sample 1: 0.25% CCA

• Sample 2: 2.5% CCA

• Sample 3: Weathered CCA

• Sample 4: Weathered Utility Pole

• Sample 5: New untreated

• Sample 6: Weathered untreated

LIBS Spectrum of CCA-treated Wood

0

2000

4000

6000

8000

10000

12000

14000

410 415 420 425 430 435 440

Em

issio

n I

nte

nsity

Wavelength (nm)

Calcium(422.67)

Chromium425.54427.48428.97

Weathered

LIBS-based Sorting

0

10

20

30

40

50

60

0 1 2 3 4 5 6 7

LIB

S C

hro

miu

m S

ign

al

Wood Sample

CCA-treated Wood

Untreated Wood

Questions?