The continual movement, processing and storage of natural gas, natural gas liquids and liquefied petroleum gas products requires that critical analyses are regularly conducted. This ensures product quality, operator safety and process efficiency.
In a previous post, we explored the benefits our G908™ device can bring to operators in the upstream sector, specifically as it relates to production and the environment. As a next step, it is important to examine some of the benefits this device brings to the midstream sector. Let’s explore how two G909 analyzers – NatGas and Sulfur – assist midstream operators with ensuring process stability and product consistency.
Rapid extended natural gas analysis for accurate compositional, BTU and HCDP calculation
Natural gas, consisting primarily of methane, with smaller fractions of ethane, propane, butanes, pentanes, higher hydrocarbons and small amounts of impurities such as hydrogen sulfide, is a valuable natural resource used to generate electricity and heat buildings. It is also fractionated to produce liquid natural gas (LNG), a feedstock for a multitude of industrial chemical processes.
The dollar value of natural gas is determined by its chemical composition. However to be sellable, it must first meet calorific and purity specifications. The standard “C6 plus” (C6+) compositional analysis calculates hydrocarbon components (in mole percent), theoretical yield of liquid hydrocarbons, in gallons per thousand cubic feet (GPMs), and heating capacity in BTUs. Extended compositional analyses, such as the C9+ or C12+, produce a more detailed identification profile. This is used to improve BTU values and determine the Hydrocarbon Dew Point (HCDP), a critical measurement that indicates temperatures at which heavier hydrocarbon components condense out of the gaseous phase, so-called hydrocarbon liquid dropout.
Managing HDCP prevents hydrocarbons from condensing in pipeline cold spots under rivers and lakes where dropout liquids collect and then move through the system, over pressuring pipelines, and overpowering liquid handling facilities. Because natural gas contains a range of hydrocarbons, accurate measurement of the HCDP is challenging. HCDP is sensitive to specific components of a gas stream and is strongly influenced by the concentration of heavier hydrocarbons, especially C6+ which increase the HCDP and can lead to under prediction of this value. G908, with integrated gas & liquid sample valving and MS/TCD detection, has been designed to provide operators with an easy to use tool for rapid extended natural gas analysis up to C12+, that has integrated reporting of Mol%, GPM, BTU, Wobbe, and HCDP values.
Accurately Determining Sulfur Species
Hydrogen sulfide and other sulfur containing compounds exist naturally in natural gas fields throughout the world. While certain sulfur species need to be removed from sour gas streams (>4ppm H2S) to reduce corrosion in pipelines, meet contractual obligations, and for public safety, other sulfur compounds including iso-propyl mercaptan, n-propyl mercaptan, tert-butyl mercaptan and thiophene are commonly added as odorants to alert users to leaks in distribution systems and natural gas fueled home appliances. Rapid, accurate measurement of sulfur species by G908, enables operators to constantly monitor pipeline gas streams for sulfur species content – including H2S, COS, mercaptans and sulfides, disulfides and thiopenes.
The integrated G908 separates and quantifies sulfur species at low-ppm to ppb levels in under 5 minutes. Operating this analyzer in single ion mode (SIM), significantly increases selectivity and sensitivity. What’s more, G908 units can be connected to sampling points at pipeline compressor/pumping stations, for on-line/at line product purity testing. Once connected, this device will run an analysis every few minutes, reporting results across SCADA/DCS and alarming if any sulfur species are detected above a specified upper control limit.
As the natural gas market continues to fluctuate, purpose-built and user-centric analytical tools, like G908, will be instrumental in helping operators ensure product quality and purity remains consistent during transmission. Such tools help operators achieve critical measurements with ease and confidence, leading to substantial time and cost savings.
Be sure to check back for our next – and final – post of this series, which will explore how G908 can be applied to meet the needs of the downstream sector.