by Applied Analytics
Natural gas for direct consumption is odorized for safety reasons. In
the odorizing process, a substance with extremely high odor is added to
natural gas in a controlled method.
Figure 1 visualizes how the OMA-300 sees the absorbance spectra of (a) un-odorized natural gas, (b) natural gas odorized with THT, and (c) 5 ppm THT in span gas. Sales-quality natural gas contains mostly methane, which does not absorb in the UV range. The absorbance curve seen in Figure 1 from 245-285 nm is the fingerprint of the aromatic compounds often present in low amounts in natural gas. To isolate THT absorbance, the unit is calibrated to the aromatic background. This procedure for interference-free, reliable odorant measurement is only possible with a multi-wavelength instrument that can properly subtract the aromatic absorbance.
Figure 1: UV absorbance spectra of un-odorized natural gas, odorized natural gas, and THT in span gas.
Each of the measurement checkpoints at this site receives natural gas flowing from a different source, such that each analyzer is being fed a stream with unique gas background matrix.
Figure 2 shows the absorbance spectra measured by the OMA-300 at various checkpoints. Table 1 shows the actual readings of THT in these natural gas streams.
Figure 2: UV absorbance spectra of THT in different natural gas sources.
|Table 1: THT readings obtained from the lab and the online OMA-300 Process Analyzer.|
At this site, the OMA-300 has simplified pipeline operation by
providing interference-free, automated odorant monitoring, giving the
operators at-a-glance odorant levels at multiple checkpoints. Applied
Analytics technology is trusted with the critical task of ensuring gas
safety downstream into populated areas.