While most of us consider our jobs to include varying degrees of pressure, some days more than others, have you ever wondered how your level of pressure compares to other occupations? Like an air traffic controller or a “natural gas energy broker.” A what? What if it was your role to make the decision on what natural gas to buy and sell? What if hundreds of thousands of dollars change hands based upon the result of your assay. A plant many miles away sets up production based on your analysis. New contracts, more samples, and new labs open, promising faster turnaround times. There is constant pressure to be accurate, responsive and competitive. Intrigued?
A natural gas energy broker deals with the buying and selling of natural gas, such as methane and propane. Following well extraction, natural gas changes hands several times before reaching the end user. And each time it changes hands it’s tested twice using a natural gas analyzer, once by the seller and separately by the buyer. Test results are compared and if they match, the gas changes hands. But what do they test for?
Simply put, natural gas testing involves determining the number of components and compositional ranges of natural gas (NG), natural gas liquid (NGL), liquefied natural gas (LNG), and liquefied petroleum gas (LPG). Yes, there are different types of natural gas and many components besides methane and propane, but more on that later. The number of components and compositional range defines the suitability of the gas for specific applications. A particularly important application is determining the calorific (or BTU) value of NG and NGL for use in home heating and cooking. The higher the BTU rating the more valuable the fuel is and the higher price it commands. Natural gas is sold in lot sizes of 1 million BTU’s, today at about $3.00 per lot. However, it is delivered by volume, typically 100K cu ft. So as a broker, you have storage for 10 million cu ft., a constant, but what you will pay varies as the composition, hence BTU, changes. A mistake on your part of getting accurate BTU measurements can cost you thousands of dollars! Having the confidence in the value and the performance of your analytical instrument to make the call on buying several tank loads of natural gas can take a toll on your liver.
What is natural gas?
Natural gas or NG, as it comes out of the well, is a naturally occurring hydrocarbon gas mixture consisting primarily of methane but also including longer chain alkanes, carbon dioxide, nitrogen, hydrogen sulfide and helium.
The three natural gas types classified by their vapor pressure are the following;
Low vapor pressure = condensate
- NGL is an acronym for Natural Gas Liquids – are the heavier hydrocarbons that remain after the methane (natural gas) is removed. NGL’s include propane, butane, isobutane, and pentanes, hexanes, heptanes, and octanes. These are heavier liquid hydrocarbons with typically 5-10 carbon atoms in length. NGLs are much more valuable as raw material for further processing than as fuel for simple combustion.
Intermediate vapor pressure = natural gas
- LNG is an acronym for liquefied natural gas. It is methane cooled to -161oC & 1 atm. This makes for a more efficient way to move, transport and handle large, bulk quantities of natural gas instead of trying to store it in a gaseous state at elevated pressures.
High vapor pressure = liquid petroleum gas
- LPG is an acronym for liquefied petroleum gas. LPG is a group of flammable hydrocarbon gases formed through pressurization and commonly used as fuel. LPG includes propane, butane, isobutane, as well as a mixture of these three gases.
How do I test natural gas?
Natural gas testing depends on the gas type. Not surprisingly, because there are many components of interest, there are many standard methods, governed by regulatory bodies such as the GPA (gas processors association). As the analytes are volatile, the technology of choice is gas chromatography (GC).
Continuing with the example of determining the calorific value of natural gases, there are two separate methods for NG and NGL, GPA 2286 and GPA 2186, respectively. Each method tests a separate set of components;
- GPA 2286: analyzes for C6+ regroup, Nitrogen, Carbon Dioxide, Methane, Ethane, i-Butane, n-Butane, i-Pentane n-Pentane, and detailed hydrocarbons from C6-C14.
- GPA 2186: analyzes for C7 regroup, Nitrogen, Carbon Dioxide, Methane, Ethane, Propane, i-Butane, n-Butane, i-Pentane, n-Pentane but also 2,2-Dimethylbutane, 2-Methylpentane, 3-Methylpentane, n-Hexane, and detailed hydrocarbons from C7-C14.
Figures 1 and 2 provide chromatographic results of the analysis of Natural Gas (NG) and Natural Gas Liquid (NGL) samples to determine the BTU content. Result show clear separation of the components of interest. Analysis was performed using the Thermo Scientific™ TRACE™ 1310 gas chromatograph equipped with two channels and two detectors, TCD and FID.
Yet, even though regulated, proven, and in use today, that doesn’t necessarily mean the methods are easy to perform. For example, the calibration method for analysis of NGL by GPA 2186 is considered to be very complicated and can take hours or more too complete by even well trained technicians. Additional pressure is applied as the results must be accurate and delivered on time – every time. Maximum uptime and easy maintenance is key to relieving pressure in the lab and ensuring quality results. The TRACE 1300’s innovative Instant Connect detector modules allow replacement in minutes – not hours or days with conventional GC’s. In addition, no expensive service call is required replacement is as simple as removing three screws popping the module out and putting a new one back. This is where innovation, simplicity, and robustness can make a difference in their implementation.
So next time you feel the pressures of your job, take relief in considering the pressures of a natural gas energy broker. Or consider the operator with P&L responsibility for maintaining a refinery fully operational and holds in the balance expenses that can reach a million dollars a day. But that’s a story for another time.
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