February 21, 2012

Selection of a novel mine tracer gas for assessment of ventilation systems in underground minesSusanne Underwood, Rosemary Patterson, Kimberly Jackson, Kray Luxbacher, Harold McNair

Acknowledgements

This publication was developed under Contract No. 200-2009-31933, awarded by the National Institute for Occupational Safety and Health (NIOSH). The findings and conclusions in this report are those of the authors and do not reflect the official policies of the Department of Health and Human Services; nor does the mention of trade names, commercial practices, or organizations imply endorsement by the U.S. Government.

Outline

• Ventilation surveys using trace analysis• Tracer characteristics• Previous uses of considered tracer elements

Background

• Results of tracer analysis• Selection of a tracer element• Development of analysis method

Application

• Future work• Conclusions

Summary

Project ObjectiveBackground

• To select a safe novel tracer• Novel tracer must have similar sensitivity to

current tracers• Develop one analysis method to allow for

concurrent deployment of tracers

Tracer TechniqueBackground

• Directly measures air quantity• When traditional point measurement of

velocity cannot be used including– Where cross-sectional area cannot be easily

measured– Locations deemed unsafe due to emergency– Places with very low or irregular flow

How does the tracer technique work?Background

• Tracer is directly released into atmosphere• Gas chromatography analysis• Two methods

– Continuous tracer release– Pulse tracer release

• Limited applications due to time

How will a novel tracer help?Background

• Increase ventilation survey versatility• Simultaneous analysis of airways/leakages• Reduces the time limitations of traditional

tracer analysis

Tracer RequirementsBackground

• Easily detected and analyzed• Absent from mine air• Nonreactive, nontoxic, noncorrosive, nor

explosive• Readily attainable• Easily transported• Highly sensitive

Tracers ConsideredBackground

• Industry standard is Sulfur Hexafluoride (SF6)• Freons

– Carbon Tetrafluoride (CF4)– Octofluoropropane (C3F8)

• Perfluorocarbon tracers

Previous Tracer ApplicationsBackground

• Freon testing in mines• Perfluorocarbon Tracers

– Urban environments– European Tracer Experiment– Oil and gas reservoirs– Home ventilation systems– No evidence that PFTs have been used in mines

PMCH CharacteristicsBackground

• C7F14

• Volatile liquid• Boiling point of 67⁰C• Biologically inert• Molecular weight of 350 g/mol• Very low ambient backgrounds

Experimental DesignApplication

• Shimadzu 2014 Gas Chromatograph• Electron Capture Detector• Columns tested for Freons

– SBP-1 Sulfur– ZB-624– TG Bond Q+– TG Bond Q

• PMCH tested using HP-AL/S column

GoalsApplication

• Achieve separation between peaks• Attain Gaussian shaped peaks• Apply an acceptable method

O2 SF6 CF4 C3F8 PMCH

40 1.1 1.22 1.1 1.2 ---20 1.08 1.19 1.1 1.24 ---40 2.14 2.22 --- 2.23 ---20 2.14 2.22 --- 2.27 ---0 2.14 2.24 --- 2.17 ---

40 1.94 2.22 2.12 3.49 ---20 1.96 5.22 --- 5.22 ---0 1.96 9.65 --- 9.84 ---

60 2.3 3.1 --- 3,09 ---50 2.33 3.42 --- 3.41 ---40 2.24 3.88 --- 3.88 ---20 2.27 5.74 --- 5.7 ---0 2.27 10.6 --- --- ---

70 2.09 2.43 --- --- 9.6167 2.07 2.44 --- --- 9.69

65 2.08 2.48 --- --- 9.74

Column Temperature (

⁰

C)Column

SBP-1 Sulfur Column

ZB-624 Column

TG Bond Q+ Column

TG Bond Q Column

HP-AL/S Column

Average Retention Time (min)

SF6 CF4 C3F8 PMCH

40 8.91x107 1.43x104 1.44x104 ---20 7.69x107 1.56x104 1.30x104 ---40 5.93x107 2.07x103 1.02x104 ---20 6.12x107 --- 8.63x103 ---0 6.57x107 --- 2.20x105 ---40 5.93x107 2.79x103 1.15x105 ---20 1.091x108 --- 6.15x104 ---0 1.100x106 --- 4.13x104 ---60 2.56x107 --- 3.34x105 ---50 2.60x107 --- 4.18x105 ---40 7.26x106 --- 3.88x103 ---20 4.50x106 --- 1.960x103 ---0 3.70x106 --- --- ---70 3.44x107 --- --- 4.95x107

67 4.24x107 --- --- 6.34x107

65 6.18x107 --- --- 7.97x107

Column Column Temperature (

⁰

C)Average Peak Area of Gases

SBP-1 Sulfur Column

ZB-624 Column

TG Bond Q+ Column

TG Bond Q Column

HP-AL/S Column

Chromatogram ResultsApplication

µV(x10,000)

min

Chromatogram ResultsApplication

µV(x100,000)

min

Chromatogram ResultsApplication

Column Name HP-AL/SColumn Type Capillary

Column Length 30 mInner Diameter 0.250 mmFilm Thickness 5 µm

Split Injector Temperature 150⁰CSplit Ratio 50:1Pressure 16.2 psi

Carrier Gas HeTotal Flow 60.8 mL/min

Make Up Gas N2

Column Flow 1.15 mL/minLinear Velocity 30 cm/s

Septum Purge Flow 2.0 mL/minDetector Temperature 200⁰C

Initial Column Temperature 67⁰C hold 2.75 minRamp 120⁰C/min

Final Column Temperature 180⁰C hold 12.30 minTotal Program Time 15.99 min

µV(x10,000,000)

min

Future WorkSummary

• PMCH vulnerabilities to sample loss• Methods of release

– Permeation tubes– Fluoroelastomer plug source– Gas Cylinders

ConclusionsSummary

• Unsuccessful separation when using Freon gases

• PMCH is a favorable tracer selection– Successful separation– Encouraging previous applications

• A simple GC method has been developed

Thank youSummary

Questions?