With natural gas that contains even low quantities of water, natural gas hydrates have a tendency to form when temperatures drop. As well as absorbing water from the wet gas stream, the glycol solution occasionally carries with it small amounts of methane and other compounds found in the wet gas. After liquid removal, the dry gas then travels back through the heat exchanger and is warmed by the incoming wet gas. Natural gas gathering and processing is a significant part of the operations of many midstream master limited partnerships. Major transportation pipelines usually impose restrictions on the make-up of the natural gas that is allowed into the pipeline. In fact, associated hydrocarbons, known as ‘natural gas liquids’ (NGLs) can be very valuable by-products of natural gas processing. The primary process for sweetening sour natural gas is quite similar to the processes of glycol dehydration and NGL absorption. While some of the needed processing can be accomplished at or near the wellhead (field processing), the complete processing of natural gas takes place at a processing plant, usually located in a natural gas producing region. Natural gas processing consists of separating all of the various hydrocarbons and fluids from the pure natural gas, to produce what is known as ‘pipeline quality’ dry natural gas. Spanning the entire NG processing chain, we have delivered everything from standardized, modular designs to world-scale, stick-built NGL plants. In these cases, separation of oil and gas is relatively easy, and the two hydrocarbons are sent separate ways for further processing. Gas separated in this unit is sent to acid gas recovery; the condensate or the oil recovered is usually sent to a refinery for processing, while water is disposed, or treated as wastewater. Natural Gas Processing and Treating. Natural gas - Natural gas - Field processing: Sometimes field-production gas is high enough in methane content that it can be piped directly to customers without processing. This is a precursor to LPG gas manufacturing process (LPG production process). A generalized natural gas flow diagram is shown in Figure 12.2 [7]. After removing the acid gases, the natural gas stream is sent to a dehydration unit to remove water typically by absorption in a glycol unit, followed by mercury removal (by adsorption on activated carbons or other sorbents), and nitrogen rejection either cryogenically, or by adsorption, or absorption depending on the nitrogen concentration. Natural gas from some wells contains significant amounts of sulfur and carbon dioxide. This natural gas, because of the rotten smell provided by its sulfur content, is commonly called ‘sour gas’. Once the natural gas has been fully processed, and is ready to be consumed, it must be transported from those areas that produce natural gas, to those areas that require it. In order to process and transport associated dissolved natural gas, it must be separated from the oil in which it is dissolved. Extraction of the other, heavier NGLs can be close to 100 percent using this process. They usually liquefy at the surface (at atmospheric pressure) and are produced separately as natural gas liquids (NGLs), either in field separators or in gas processing plants. In addition, the sulfur that exists in the natural gas stream can be extracted and marketed on its own. As the wet gas passes around the particles of desiccant material, water is retained on the surface of these desiccant particles. For the Qatar region, natural gas processing is of crucial importance. Printed: 26 April 2004 - [Natural Gas Processing Principles and Technology - Part I.doc] University of Calgary Natural Gas Processing Principles and Technology - Part I April 2004 Author: Dr. A.H Younger, P.Eng Revised and Prepared by: Dr Harald F. Thimm & Jason Sullivan Thimm Engineering Inc. 214, 3916 64th Avenue SE Calgary, Alberta T2C 2B4 Once the gas stream has had the acid gases and water vapor removed, it is now classified as dry, sweet gas, and is suitable for even further processing. Most of the liquid, free water associated with extracted natural gas is removed by simple separation methods at or near the wellhead. In addition to losing a portion of the natural gas that was extracted, this venting contributes to air pollution and the greenhouse effect. Most often, however, the gas contains unacceptable levels of higher-weight hydrocarbon liquids as well as impurities, and it is available only at very low pressures. In addition, raw natural gas contains water vapor, hydrogen sulfide (H2S), carbon dioxide, helium, nitrogen, and other compounds. The Pennsylvania State University © 2020. Natural gas from gas and condensate wells, in which there is little or no crude oil, is termed ‘nonassociated gas’. Note that the fractionation unit may also include a butane splitter or deisobutanizer to separate n-butane and iso-butane. Sulfur can be sold and used if reduced to its elemental form. This process is known simply as the ‘amine process’, or alternatively as the Girdler process, and is used in 95 percent of U.S. gas sweetening operations. An example of absorption dehydration is known as Glycol Dehydration. M.R. Wet natural gas is passed through these towers, from top to bottom. However, if it is economic to extract ethane and other lighter hydrocarbons, cryogenic processes are required for high recovery rates. Natural Gas Processing; We offer reliable solutions across the natural gas value chain through a broad technology portfolio that includes gas conditioning and treating, fractionation, deep ethane extraction and LPG recovery, and liquid product treating. In certain instances, however, specialized equipment is necessary to separate oil and natural gas. Two or more towers are required due to the fact that after a certain period of use, the desiccant in a particular tower becomes saturated with water. 2217 Earth and Engineering Sciences Building, University Park, Pennsylvania 16802 Adsorption occurs when the water vapor is condensed and collected on the surface. The gas/oil mixture is piped out of the well and into a gas trap, natural gas processing separates the stream into crude oil and "wet" gas, which contains LPG and natural gas. Gas Processing Journal is devoted to aspects of production, processing and transmission of natural gas with scientific research certification from MSRT. Natural gas withdrawn from natural gas or crude oil wells is called wet natural gas because, along with methane, it usually contains NGL—ethane, propane, butanes, and pentanes—and water vapor. Absorption occurs when the water vapor is taken out by a dehydrating agent. It consists of a simple closed tank, where the force of gravity serves to separate the heavier liquids like oil, and the lighter gases, like natural gas. The extracted NGL, on the other hand, is sent to a fractionation unit that operates like Light Ends Unit in a refinery, as discussed in Lesson 5, separating ethane, propane, butane, and naphtha (>C5, natural gasoline). The only company worldwide with the know-how and experience to design and operate hydrogen and syngas plants based on proprietary technologies. This rapid expansion of the gas allows for the lowering of the temperature in the separator. Natural gas processing consists of separating all of the various hydrocarbons and fluids from the pure natural gas, to produce what is known as ‘pipeline quality’ dry natural gas. There are two principle amine solutions used, monoethanolamine (MEA) and diethanolamine (DEA). An example of this type of equipment is the Low-Temperature Separator (LTX). This solution has an affinity for sulfur, and absorbs it much like glycol absorbing water. These processes are dictated by the profitability metric referred to … Department of Energy’s Office of Fossil Energy, Natural Gas – From Wellhead to Burner Tip. It is now a mixture of absorption oil, propane, butanes, pentanes, and other heavier hydrocarbons. Natural gas hydrates are crystalline ice-like solids or semi-solids that can impede the passage of natural gas through valves and pipes. Natural gas is considered the dominant worldwide bridge between fossil fuels of today and future resources of tomorrow. Two basic steps: 1) Extraction, 2) Fractionation. That means that before the natural gas can be transported it must be purified. These separators use pressure differentials to cool the wet natural gas and separate the oil and condensate. Following the NGL extraction, the treated natural gas stream that is, now, mostly methane, or a gas compliant with the natural gas specifications is sent to the pipeline for transmission to the point of use. According to the Gas Processors Association, these two processes account for around 90 percent of total natural gas liquids production. Should these hydrates accumulate, they can impede the passage of natural gas through valves and gathering systems. This process allows for the recovery of about 90 to 95 percent of the ethane originally in the gas stream. Gas wells typically produce raw natural gas by itself, while condensate wells produce free natural gas along with a semi-liquid hydrocarbon condensate. The rich oil is fed into lean oil stills, where the mixture is heated to a temperature above the boiling point of the NGLs, but below that of the oil. After natural gas is processed, it's then transported to market via pipelines. Gas Processing . Once absorbed, the glycol particles become heavier and sink to the bottom of the contactor where they are removed. Methane is the gas found in natural gas, and natural gas processing is used to remove other gases and impurities. The basic absorption process above can be modified to improve its effectiveness, or to target the extraction of specific NGLs. Second, the contaminants, which include hydrogen sulphide (H 2 S), carbon dioxide (CO 2 ), mercaptans, carbonyl sulphide (COS) and mercury, must be removed. Most produced gas must be treated before the consumer can use it, and there were nearly 2,000 gas processing plants operating around the world as of mid-2006. Vista completed the detailed engineering design and procurement of a grassroots gas processing facility handling 20 MMSCFD (566 103 Std. The extraction of NGLs from the natural gas stream produces both cleaner, purer natural gas, as well as the valuable hydrocarbons that are the NGLs themselves. The behavior of natural gas, whether pure methane or a mixture of volatile hydrocarbons and the nonhydrocarbons nitrogen, carbon dioxide, and hydrogen sulfide, must be understood by the engineer who is designing the operating equipment for its production, processing, and transportation. The heaters ensure that the temperature of the gas does not drop too low. m3/day) of sweet natural gas. When this natural gas and oil is produced, it is possible that it will separate on its own, simply due to decreased pressure; much like opening a can of soda pop allows the release of dissolved carbon dioxide. These hydrates are solid or semi-solid compounds, resembling ice like crystals. PETROGAS has been a recognized leader since 1975 in the design, manufacturing, and operation of gas … The last step in the processing sequence is the Natural Gas Liquids (NGL) extraction, fractionation, and treatment, as described in Figure 12.4. Source: Duke Energy Gas Transmission Canada. According to the American Gas Association’s Gas Facts 2000, there was an estimated 36,100 miles of gathering system pipelines in the U.S. in 1999. Gas processing plants are intended to help you meet pipeline sales specifications and/or recover valuable marketable liquids from natural gas. The type and extent of natural gas processing depend on the original gas composition and the specifications of the consumer. Use industry-leading technologies for CO₂ and H₂S removal Acid gas treatment and removal technologies separate sour gases—highly corrosive CO 2 and often deadly H 2 S acid gases—from saleable natural gas streams in a process known as gas sweetening. In order to decrease the amount of methane and other compounds that are lost, flash tank separator-condensers work to remove these compounds before the glycol solution reaches the boiler. In certain instances, it is economic to simply leave the lighter NGLs in the natural gas stream. Natural Gas Processing And Dew Point Control. Typical desiccants include activated alumina or a granular silica gel material. There are two principle techniques for removing NGLs from the natural gas stream: the absorption method and the cryogenic expander process. Glycol, the principal agent in this process, has a chemical affinity for water. There are a number of different ways of chilling the gas to these temperatures, but one of the most effective is known as the turbo expander process. By varying the pressure of the gas in various sections of the separator, it is possible to vary the temperature, which causes the oil and some water to be condensed out of the wet gas stream. 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