Hydrocarbon gas liquid
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Hydrocarbon gas liquids (HGL) occur as liquids under higher pressures and as gases at atmospheric pressure. They are found in crude oil and natural gas, which consist of mixtures of hydrocarbons (molecules of carbon and hydrogen). The type of HGL determines the specific temperatures and pressures at which the gas becomes a liquid. HGLs can also be liquefied by cooling. HGLs are generally considered either light or heavy depending on the number of hydrogen and carbon atoms in each hydrocarbon gas liquid molecule.[1]
Background
Hydrocarbon gas liquids (HGL) are extracted during oil and natural gas production; HGLs are extracted during the oil refining process (when oil is refined into a petroleum product) and during natural gas processing at a natural gas plant. According to the U.S. Energy Information Administration, natural gas plant liquids (a form of hydrocarbon gas liquids) accounted 82 percent of all HGL production in the United States as of December 2015; oil refinery production accounted for the remainder. HGL use represented 13 percent of total U.S. petroleum consumption in 2014.[1]
Production
HGLs are naturally present as gases in natural gas deposits. The HGLs are extracted at natural gas processing plants. HGL compounds are removed through the process of fractionation in which hydrocarbons are removed and separated into distinct compounds, mainly propane, butane, and ethane. These compounds, known as purity products, consist of at least 90 percent of one type of HGL molecule. Propane and propylene are the main HGLs extracted during oil refining. HGLs from oil can be sold for use in gasoline or petrochemical production, or they can be burned as fuel at oil refineries.[1]
Uses
HGLs have a high energy density (the amount of energy stored in a given space per volume) and multiple uses due to their ability to become liquids or gases. HGLs are used in the following ways:Cite error: Closing </ref> missing for <ref> tag
Most HGLs produced in the United States are delivered by pipelines. The pipelines deliver the HGLs from the production site to areas where they will be stored for later distribution. Most HGLs delivered through a pipeline are Y-grade quality, which includes raw, unseparated HGL. Separate HGL products such as propane and butane are transported through pipelines as liquefied petroleum gas.[2]
After being transported by pipelines, HGLs are primarily delivered by trucks and railroads since several regions in the United States, such as New England and Florida), do not have nearby HGL pipelines. Wholesale and bulk purchasers receive HGLs from railroads, which are able to deliver large volumes of HGL. The most common HGL consumer product is propane, which is delivered by truck in pressurized tanks to homes, farms, and businesses. Consumers use HGLs for crop drying, space and water heating, engine fuel, and cooking. Imports and exports of HGL to and from the United States are carried by gas tankers. These ships keep HGL in liquid form through pressurization, refrigeration, or both.[2]
Because HGL is produced at a level greater than can be transported, it must be stored. Seasonal demand for HGL can also shift. For example, demand for propane is typically lower in warmer months and generally higher in colder months. HGLs are stored in underground caverns. The HGL takes the form of a pressurized liquid when it is stored. The caverns are located primarily in salt formations, though some storage caverns are created in granite, shale, and limestone rock. Aboveground tanks may be used if an area's geology, such as in New England, is incompatible with underground storage.[2]
See also
Footnotes
