Reliable natural gas quality analysis is critical to minimizing safety, operability and financial problems across the value chain. Variability in gas quality can create a variety of challenges for large-scale users, particularly for use as a fuel for gas turbines or sophisticated fired heaters, where the BTU rating (calorific value) is critical. For gas turbines, the Wobbe index indicates additional characteristics affecting its suitability as a fuel. For some users, contaminants can be just as important.
To meet gas quality measurement requirements, operators have traditionally used multiple gas analyzers with different technologies, or relied on conventional air-bath oven gas chromatographs which are complex large platforms unsuitable for field-installation without elaborate analyzer shelters, adding significant capital and operating costs.
In a Gas Processing and LNG magazine article, Jason and I explain how to streamline complex gas quality analysis while saving costs and footprint using new field-deployable gas chromatographs (GCs) that deliver a single, compact and cost-effective solution to report on the contents of natural gas supplies.
Today’s gas chromatographs are no longer one-size-fits-all. They are designed to fit the list of components that operators specify for their routine applications. For example, a basic GC can typically handle a fixed proportion of hydrocarbon components as outlined by Gas Processors Association (GPA) Midstream Standard 2261.
For many applications, such as when a facility operating a gas turbine must ensure that the pipeline supply meets essential Wobbe Index requirements, this methodology is often sufficient.
For users needing to quantify additional components, including heavier hydrocarbons for critical dew points, a C9+ GC uses a double-column/detector set in a two-stage configuration. Quantifying contaminants, such as sulfur in its various forms is a different matter. Traditionally, total sulfur measurements were typically made using separate, dedicated analyzers employing different technologies. Another option relied on a flame photometric detector (FPD) in conjunction with the conventional air-bath oven gas chromatographs which are too large and expensive for field use.
With traditional analyzer technologies, measuring quantitative values of BTU content, hydrocarbon dewpoint, total sulfur, and hydrogen sulfide have often required up to four analyzers using different analysis methods. However, the development of:
…a micro-flame photometric detector (µFPD) makes it possible to include this technology on smaller, less-expensive, transmitter-style GCs. It is now possible to enclose the hardware for all measurement stages in a single, airless oven, minimizing size and complexity.
Leveraging the micro-flame photometric detector, Emerson’s Rosemount 700XA GC, an explosion-proof analyzer designed for in-situ or close-to-tap field mounting, can measure hydrogen sulfide (H2S), energy content, hydrocarbon dewpoint, as well as trace-level speciation and quantification of total sulfur compounds in a single compact solution. ATEX/IECEX safety rated, the Rosemount 700XA GC doesn’t require a shelter, even in Class 1, Division 1 areas, thereby eliminating the need for air purged enclosures.
To avoid the cost of using multiple analyzers for complex natural gas analysis, read the article for ways to use the Rosemount 700XA GC for extended gas composition analysis, streamlining measurements, and saving CAPEX and footprint. The article also describes how automated processing and remote connectivity of the Rosemount 700XA reduce the need for specialized training.
Visit the Gas Analysis pages at Emerson.com for more on technologies and solutions for quality and content evaluation. You can also connect and interact with other engineers in the Oil & Gas and Chemical Groups at the Emerson Exchange 365 community.
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