The GPA 2186-02 method can be performed on two separate gas chromatographs, but is more typically done on a single chromatograph with two channels. The method uses both a packed column and a capillary column for the separations, and then combines the two analyses into a single report by using the pentane peaks to calculate a bridge factor. The sample is injected into the two columns simultaneously by rotating valves. Nitrogen/carbon dioxide through n-pentane are separated isothermally on a packed column and detected with a thermal conductivity detector (TCD), while the C6+ hydrocarbons are separated on a capillary column and detected with a flame ionization detector (FID). A third valve is used to backflush the packed column to the TCD after the pentanes have eluted. Chromatograms and a chromatography data system (CDS) are used to calculate weight percentage, mole percentage, and liquid volume percentage of each component. N-pentane and isopentane peaks are used to bridge weight percentages to combine results from both chromatograms into a single report using a custom report generator, which will be demonstrated in this presentation along with the CDS. The chromatographic results are then normalized and summed. Any residual due to rounding errors is subtracted from the largest component so that the sum is exactly 100.00%.
- Understand why the GPA 2186 method provides a more thorough characterization of y-grade natural gas liquids that better reflects the quality and market value of the product.
- Learn why the calibration of the method can be very tedious and require a day or more of an analyst's time.
- Discover why automation is required to manage the extensive calculations that involve numerous physical constants in addition to the chromatograms.
- Discover how custom calculations work with Microsoft Excel ™ and OpenLabs CDS to provide automated analysis and custom report generation.
Brandt Hutchison is a lab specialist-SME lead at Mid-America Pipeline. He studied engineering at Southwest Missouri State and received a BA in industrial engineering from McPherson College. He served in the U.S. Navy, where he trained in nuclear power technology.