Development of hydrocarbon vapor imaging

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Development of hydrocarbon vapor imaging systems
for petroleum and natural gas fugitive emission
sensing
Thomas J. Kulp, Karla Armstrong, Ricky
Sommers, Uta-Barbara Goers, and Dahv
Kliner Sandia National Laboratories Livermore, CA
94551-0969 tjkulp_at_sandia.gov
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Imaging lidar is a powerful tool for gas leak
detection

• A laser illuminates the scene as it is
• imaged in the infrared
• Gases are visualized when they absorb
• the backscattered radiation
• Conventional leak detection is carried out
• using handheld sensors
• Imaging allows rapid broad area coverage
• and easy recognition of plume presence
• and source location

Solid surface
Laser radiation tuned to gas absorption
Gas plume
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Gas imaging offers to accelerate leak
surveillance, thus decreasing the cost of
environmental compliance

• Typical refinery spends 1M
• per year for leak detection and
• repair (LDAR)
• Currently hand-held sniffers
• are used according to EPA
• Method 21
• The technology in this project is
• now being considered as a viable
• alternative to Method 21 by a
• working group of EPA, API, DOE,
• and petroleum industry members
• Acceptance will require approval
• as an alternative work practice
• - laboratory testing

Measured Leak Rate Distribution Data
Smart LDAR concept Rapid surveys focusing on
strong leakers
7 Refineries (all components and
services) Source API Publication 310, November
1997
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Motivation for leak sensing in the US natural gas
industry
Safety issues
800,000-900,000 leaks addressed each year
200-300 leaks result in accidents
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Problem There has been a lack of BAGI
instrumentation that sees hydrocarbons
critical to the gas and oil industries

• Operation near 3.3 µm favored due to
• gas and atmospheric absorption
• Broad (100-200 cm-1) tuning desirable
• to access multiple species
• BAGI instruments commercially available
• at 9-11 µm but not at 3.3 µm
• Basic limitation has been the lack of
• suitable laser sources

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Solution We have developed imagers that use
nonlinear conversion to generate tunable mid-IR
(3-5 µm) light
Scanned imager
CW optical parametric oscillator (OPO)
Pulsed imager
Pulsed DFG-OPA laser
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Nonlinear conversion shifts light from one
wavelength to another
Optical parametric oscillator (OPO)
Optical parametric generation

• Signal (or idler) wave resonated
• Pthr Watts Pout 100s mW - Ws

New microengineered nonlinear crystals improve
efficiency gt smaller and more tunable systems

• Example Periodically-poled
• lithium niobate (PPLN)
• Engineered optical axis inversion
• 15X more gain than ordinary crystal
• Tunable over 1.3 - 4.4 µm

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The first hydrocarbon imager was a pulsed system
Range - 70 m Sensitivity - 36 ppm-m methane
0.02 scf/hr leak rate
Kulp, Powers, Kennedy, and Goers Applied Optics
37 3912-3922 (1998)
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Differential imaging was demonstrated to improve
gas plume visibility for the pulsed imaging system
Powers, Kulp, and Kennedy, Applied Optics 39
1440-1448 (2000)
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Next step in evolution Development of CW systems

• CW systems offer
• Less expensive imager
• (scanner vs array)
• Clear commercialization path
• Upgrade to diodes
• Less susceptible to damage

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A PPLN-based OPO was developed for scanned cw
imaging
NdYAG laser
Generic refinery wavelength
Two periods created 29.3 - 30.1 µm 29.7 -
30.0 µm
Idler tuning range 2820-3150 cm-1
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A van-mounted scanned system employing the PPLN
OPO was field tested at a refinery during April,
1999
Gas plume

• System tested in parallel
• to EPA Method 21
• Imager operated well in
• the field environment
• Results motivated the
• development of a portable
• system

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April 1999 field demonstration

• M21 team independently monitored process areas
  first
• - Measured 1,464 components, primarily valves and
  pump seals
• - All components part of existing LDAR program
• Gas Imaging team monitored independently next
• - Observed estimated 6,600 components, all types
• - All visible parts observed, regardless of
  whether tagged or not
• - Followed-up leak discoveries with vapor
  analyzer
• - Gas Imaging leak discoveries video-taped
• Both teams tested seven process areas

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Gas imaging found high leakers in three process
areas

• High leakers above 100,000 ppm were identified
  by current prototype
• Lowest leak independently found was 28,000 ppm
• Some leaks at about 30,000 ppm were missed
• Did not find leaks below 10,000 ppm in the
  refinery setting
• Lower detection limit currently appears to be
  between 25,000
• and 50,000 ppm

Restricted access during test motivated the
development of an operator-portable imaging system
Full results tabulated in a report located on the
EPA Website
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Goal Develop an imaging lidar for leak detection
that can be battery operated and carried by the
system user
Van-mounted and operator-portable raster-scanned
imaging lidars

• Van-mounted imager successfully tested in
  natural gas distribution
• and petroleum refinery applications. However,
  access restrictions
• prohibits vehicle use in many cases.

Natural gas leak in Atlanta Ga
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Approach Develop a system based on a compact CW
OPO pumped by a Yb-doped fiber amplifier
Miniature NdYAG seed laser
Fiber Optic Amplifier
Compact SR-OPO
Consolidated scanner (single unit)

• Primary technology competition is diode lasers
  which cannot produce
• sufficient 3.3 µm power at narrow linewidth and
  require cryogenic cooling
• Yb-doped fiber amplifiers demonstrated 45
  electrical-optical conversion
• CW OPO capable of converting 60-90 of pump
  output to signal idler
• Fiber amplifier inherently rugged

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The Yb-doped fiber amplifier produces high output
power in a compact and efficient format

• Present diode (JDS) requirement - 4V _at_ 3.5 A to
  achieve 4W output
• No visible SBS with a single-mode seed