2.2 Processing a Sample
A natural gas sample is extracted from the pipeline, processed for particulate
removal and phase integrity by the sample conditioning module (optional as
required), transported to the NGC and injected onto the chromatographic columns
where component separation occurs.
The NGC analyzes each sample, utilizing established chromatographic
techniques. The resulting information consists of mole percent values for each
component. These values are used to perform energy calculations. Calculated
values include: gas compressibility, real relative density, Btu/CV value, liquid
GPM, Wobbe index, methane number and several other optional calculated
values. Gas compressibility selections include NX-19, AGA-8 detail, single virial
summation factor, ISO summation factor and none (a factor of one is used).
The processed sample is then vented with the carrier gas and results are stored in
memory and communicated to other devices, as needed. All of these values, as
well as composition, are available on various Modbus communication protocols.
2.2.1 Hydrocarbons
To further define the natural gas components, Table 2–1
gives additional details
for each hydrocarbon. Among the key information is the boiling point of the
component. The boiling point of each component correlates to the order each
component will exit the column.
Table 2–1 Hydrocarbons
C1H4 C1 Methane -161.60
C2H4 C2= Ethylene -103.75
C2H6 C2 Ethane -88.65
C3H6 C3= Propylene -47.65
C3H8 C3 Propane -42.05
C4H10 IC4 Isobutane -11.65
C4H8 C4= Butylene -6.95
C4H10 C4 Butane -.45
C5H12 NeoC5 Neopentane 9.85
C5H12 IC5 Isopentane 27.85
C5H12 C5 Pentane 34.85
C6H14 C6 Hexane 68.85
C7H16 C7 Heptane 97.85
C8H18 C8 Octane 125.55
C9H20 C9 Nonane 150.95
C10H22 C10 Decane 173.95
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