Figure 4. The SpectraSensors
SS2100 using TDL technology s
through the lead acetate tape, which
changes color when reacting with sulfur.
The system analyzes the color change with
a photometer. However, the lead acetate
tape is a consumable that is directly
exposed to the gas stream. Tape reels
must be changed periodically (weekly or
monthly), and if there is a system leak, it
exposes the whole tape. Also, the used tape
is considered hazardous waste, and must be
disposed of accordingly.
Some processors use a UV photometer
for measuring H₂S. Natural gas may have
varying percentages of methane, propane
and possibly more than a dozen other components. The measurements results of UV
photometers are susceptible to gas composition changes. When the background matrix
of the gas changes, that often causes erroneous readings and consequential problems.
For H₂S applications, the TDL-based analyzer measures sour gas going into processing, and sweetened gas coming out. Fast
analyzers enable better control of processes
by letting the processor know instantly how
much processing is needed and provides
for faster shut-off when the sweetened gas
is not up to required standards. Changes in
gas concentrations can be seen immedi-
ately with TDL analyzers preventing false
alarms, false readings and unwarranted
shutdowns.
LNG Applications
The presence of even trace amounts of H₂O
or CO₂ can threaten the integrity of processing
equipment during compression and liquefaction of natural gas due to ice formation. It is
essential to have very fast H₂O or CO₂ detection in order to improve the life of the desiccant while retaining product quality.
In the past, LNG (liquid natural gas) and NGL
(natural gas liquids)gas processors have relied
on surface based analyzers such as electrochemical and quartz crystal cells to measure
trace amounts of moisture in process streams.
Although these devices may perform with
acceptable accuracy at first, the confidence
level in their measurements soon becomes
low, due to drift, the inability to read high concentrations of moisture, and the tendency for
their sensor probes to become desensitized
by the gas streams they are measuring. Such
20
March/April 2008
Ultra-High Purity
Gas Panels, Cabinets, GIB’s
Chemical Delivery Systems
Electro-Mechanical Assemblies
Semiconductor Hardware and Components
UHP Welded Assemblies
Exhaust Manifolds with Pulled Ports
625 Wool Creek Dr. 9025 S. W. Hillman Court, St# 3132,
San Jose, CA 95112 Wilsonville, OR 97070
Ph: 408-350-0244 Ph: 503-682-4080
Fax: 408-350-0229 Fax: 503-682-4067
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SemiSystems
a division of MDC Vacuum Products, LLC
See us at SVC TechCon Chicago
Booths 1215 & 1217, April 21-22
www.itwsemisystems.com
Gases&Instrumentation
