Development of hydrocarbon vapor imagingsystems for petroleum and natural gas
fugitive emission sensing
Thomas J. Kulp, Karla Armstrong, Ricky Sommers,Uta-Barbara Goers, and Dahv Kliner
Sandia National LaboratoriesLivermore, CA 94551-0969
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
Gas plume
Laser radiationtuned to gasabsorption
Imaging lidar is a powerful tool for gas leak detection
0102030405060708090
100
0-99 ppm 500-999ppm
10,000-49,999
ppm
>100,000ppm
%Total Count
% Total Emissions
*7 Refineries (all components and services)
Source: API Publication 310, November 1997
Measured Leak Rate Distribution Data*
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
- field evaluations
Smart LDAR concept: Rapid surveys focusing on strong leakers
800,000-900,000 leaks addressed each year
200-300 leaks result in accidents
Safety issues
Surveys mandated annually
Surveying costs of $1.6 billion annually
Cost & Efficiency
Production, Processing,Transportation Hardware
750 processing plants3000 compressor stations
103 Bscf (1.98 Tg) / yr.
Transportation
400,000 miles of pipeline
6 Bscf (0.12 Tg) / yr.
Distribution
1,400,000 miles of pipeline
42 Bscf (0.8 Tg) / yr.
Industry-wide losses of natural gas
Losses represent a significant product cost and a significant contribution to greenhouse gas flux
Motivation for leak sensing in the US natural gas industry
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0.6
0.4
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0.0
Atm
osp
heri
c abso
rbti
on
350030002500200015001000500
Frequency in wavenumbersFrequency (cm-1)
Absorption by the atmosphere
Frequency (cm-1)3500 3000 2500 2000 1500 1000
Opt
ical
dep
th Butane absorption
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
0.12
0.10
0.08
0.06
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0.02
0.00
Abso
rbance
3.53.43.33.23.1
Wavelength (µm)Wavelength (µm)
Opt
ical
dep
th Methaneabsorption
Scanned imager
Laser beam
Detector field-of-view
Tunable CW laser
Scanner
Solution: We have developed imagers that use nonlinear conversion to generate tunable mid-IR (3-5 µm) light
Beam formatter
Tunable pulsed laser
Snapshot-modefocal-plane array
Pulsed imager
CW optical parametric oscillator (OPO)
Pulsed DFG-OPA laser
Nonlinear conversion shifts light from one wavelength to another
Optical parametric oscillator (OPO)
• Signal (or idler) wave resonated• Pthr = Watts Pout = 100’s mW - W’s
Optical parametric generation
Pump
Nonlinear crystal
IdlerSignal
pump = signal + idler
New microengineered nonlinear crystals improve efficiency —> smallerand more tunable systems
Multi-grating PPLN crystal
Close-upWide-view
Example: Periodically-poled lithium niobate (PPLN)
• Engineered optical axis inversion
• 15X more gain than ordinary crystal
• Tunable over 1.3 - 4.4 µm
The first hydrocarbon imager was a pulsed system
Methane plume at 20 m
Nd:YAG pumped dye laser (repetition rate 30 Hz) Beam formatter
Amber ProViewFPA controller
Video display256 x 256 snapshot-modeInSb focal-plane array camera
HS
VB
Computer withframe grabber board
and WIT software
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)
Differential imaging was demonstrated to improve gasplume visibility for the pulsed imaging system
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0.5
Tran
smit
tan
ce
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Methane spectrum
Laser Energy (wavenumbers)
Scale, Ratio, log
Processing
Single-wavelength image Differential image
Methane imaging against grass
Powers, Kulp, and Kennedy, Applied Optics 39 1440-1448 (2000)
Next step in evolution — Development of CW systems
Breadboard pulsed imager
Fieldable pulsed prototype
Developmentof a CW OPO
Field test van-mounted
system
FY98
FY98
FY99 Developmentof operator-
portable system
FY00-01
CW systems offer:• Less expensive imager (scanner vs array)
• Clear commercialization path
• Upgrade to diodes• Less susceptible to damage
Idler @ ~ 3.3 µm
Signal - wavemeter
Pump @ 1.064 µm
PPLN CrystalSignal - power monitor
Pump dump
Solid etalon
A PPLN-based OPO was developed for scanned cw imaging
Two periods created: 29.3 - 30.1 µm 29.7 - 30.0 µm
PPLN fan-out grating used200x10-6
150
100
50
0
Ab
sorp
tion
In
ten
sit
y
3100305030002950290028502800
Wavenumbers [cm-1
]
n-hexane n-pentane n-butane propane
Wavenumbers [cm-1]
Abs
orp
tion
Inte
nsity
“Generic” refinery wavelength
Idler tuning range: 2820-3150 cm-1
Nd:YAG laser
Scanner
FOVrotations
Turret
3-µm beam
Nd:Y
AG
lase
r
PPLN
OPO
IR image seen by the
operator
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
• 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
April 1999 field demonstration
• 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
Gas imaging found high leakers in three process areas
Full results tabulated in a report located on the EPA Website
Restricted access during test motivated the developmentof an operator-portable imaging system
Goal: Develop an imaging lidar for leak detection that can be battery operated and carried by the system user
Nd
:YA
G la
ser
PPLN
OPO
• Van-mounted imager successfully tested in natural gas distribution and petroleum refinery applications. However, access restrictions prohibits vehicle use in many cases.
Van-mounted and operator-portableraster-scanned imaging lidars
Natural gas leak in Atlanta Ga
Approach: Develop a system based on a compact CW OPO pumped by a Yb-doped fiber amplifier
Miniature Nd:YAG
seed laser
Fiber Optic Amplifier
Compact SR-OPO
Consolidatedscanner
(single unit)
VanSystem
Water-cooled Nd:YAG laser
“Breadboard”OPO system
3-componentscanner
• 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
The Yb-doped fiber amplifier produces high output powerin a compact and efficient format
• Present diode (JDS) requirement - 4V @ 3.5 A to achieve 4W output
• No visible SBS with a single-mode seed
5
4
3
2
1
0
Out
put P
ower
(W
)
543210
Pump Diode Current (A)
Initial system - Polaroid pump diodes
