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'''Amine gas treating''' refers to a group of processes that use aqueous solutions of various [[amine]]s to remove [[hydrogen sulfide]] (H<sub>2</sub>S) and [[carbon dioxide]] (CO<sub>2</sub>) from gases.  It is a common [[unit process]] used in [[oil refinery|refineries]], [[petrochemical]] plants, [[natural gas processing|natural gas processing plants]] and other industries. The process is also known as '''Acid gas removal''' and '''Gas sweetening'''.


Processes within oil refineries or natural gas processing plants that remove hydrogen sulfide and/or [[mercaptans]] are commonly referred to as '''''sweetening''''' processes because they results in products which no longer have the sour, foul odors of mercaptans and hydrogen sulfide.
There are many different amines used in gas treating:
*[[Ethanolamine|Monoethanolamine]] (MEA)
*[[Diethanolamine]] (DEA)
*[[MDEA|Methyldiethanolamine]] (MDEA)
*[[Diisopropylamine]] (DIPA)
*Diglycolamine (DGA)
The most commonly used amines in industrial plants are the alkanolamines MEA, DEA, and MDEA.
Amines are also used in many oil refineries to remove [[sour gas]]es from liquid hydrocarbons such as [[liquified petroleum gas]] (LPG).
==Description of a typical amine treater==
Gases containing H<sub>2</sub>S or both H<sub>2</sub>S and CO<sub>2</sub> are commonly referred to as ''[[sour gas]]es'' or ''[[acid gas]]es'' in the [[hydrocarbon]] processing industries. 
A typical amine gas treating process (as shown in the [[Process Flow diagram|flow diagram]] below) includes an '''absorber''' unit and a '''regenerator''' unit as well as accessory equipment.  In the absorber, the downflowing amine solution absorbs H<sub>2</sub>S and CO<sub>2</sub> from the upflowing sour gas to produce a sweetened gas stream (i.e., an H<sub>2</sub>S-free gas) as a product and an amine solution rich in the absorbed acid gases.  The resultant "rich" amine is then routed into the regenerator (a stripper with a [[reboiler]]) to produce regenerated or "lean" amine that is recycled for reuse in the absorber. The stripped overhead gas from the regenerator is concentrated H<sub>2</sub>S and CO<sub>2</sub>. In oil refineries, that stripped gas is mostly H<sub>2</sub>S, much of which often comes from a sulfur-removing process called [[hydrodesulfurization]].  This H<sub>2</sub>S-rich stripped gas stream is then usually routed into a [[Claus process]] to convert it into elemental [[sulfur]]. In fact, the vast majority of the 64,000,000 metric tons of sulfur produced worldwide in 2005 was byproduct sulfur from refineries and other hydrocarbon processing plants. <ref>[http://minerals.usgs.gov/minerals/pubs/commodity/sulfur/sulfumcs06.pdf Sulfur production report] by the [[United States Geological Survey]]</ref><ref>[http://www.agiweb.org/geotimes/july03/resources.html Discussion of recovered byproduct sulfur]</ref>  In some plants, more than one amine absorber unit may share a common regenerator unit.
[[Image:AmineTreating.png|frame|center|380px|{{#ifexist:Template:AmineTreating.png/credit|{{AmineTreating.png/credit}}<br/>|}}Schematic flow diagram of a typical amine gas treating unit used in industrial plants.]]
In the [[steam reforming]] process of hydrocarbons to produce gaseous [[hydrogen]] for subsequent use in the industrial synthesis of [[ammonia]], amine treating is one of the commonly used processes for removing excess carbon dioxide in the final purification of the gaseous hydrogen.
== New amine-based materials for gas processing ==
In recent years, interest in the development of new materials and technologies for the 'capture' of carbon dioxide (CO<sub>2</sub>) has increased significantly.  This development appears to be driven largely by increasing concerns about the impact of rising CO<sub>2</sub> emissions on climate change (specifically global warming).  One outcome has been the introduction of new reactive amines which have chemical structures in which the CO<sub>2</sub>-reactive part of the molecule (the amine group) is tethered to an ionic (salt-like) structural element.  The ionic nature of these hybrids makes them less likely to be lost to evaporation during CO<sub>2</sub> capture operations, and as a result it may be possible to suppress the typical amine loss in scrubbing systems of about four pounds of amine per ton of CO<sub>2</sub> captured.  While systems involving the use of certain simple amine-salt solutions in water were first evaluated for CO<sub>2</sub> capture decades ago, it was only in 2002 <ref>Bates, E. D.; Mayton, R. D.; Ntai, I.; Davis, J. H., Jr., ''CO<sub>2</sub> Capture by a Task-Specific Ionic Liquid'', Journal of the American Chemical Society, 2002, Vol. 124, No. 6, 926-927</ref> that systems of pure, CO<sub>2</sub>-reactive liquid salts (amine-appended ''task-specific ionic liquids'' called TSILs) were first introduced.  Recently, the researchers responsible for that development have reported improved approaches<ref>Soutullo, M. D.; Odom, C. I.; Wicker, B. F.; Henderson, C. N.; Stenson, A. C.; Davis, J. H., Jr., ''Reversible CO<sub>2</sub> Capture by Unexpected Plastic-, Resin, and Gel-like Ionic Soft Materials Discovered During the Combi-Click Generation of a TSIL Library'', Chemistry of Materials, 2007, Vol. 19, No. 15, 3581-3583</ref> (e.g., the use of [[Click chemistry]] and commodity chemicals) for the preparation of CO<sub>2</sub>-reactive salts, procedures which result in salts that are much less expensive to prepare than the earlier first-generation of materials.  Interestingly, the library of new compounds obtained in this fashion also included CO<sub>2</sub>-reactive salts that are plastic-, resin- and gel-like in character.
==See also==
*[[Ammonia production]]
*[[Hydrodesulfurization]]
*[[Claus process]]
*[[Selexol]]
*[[Rectisol]]
*[[Amine]]
*[[Ionic liquid]]s
==References==
{{Reflist}}
==External links==
*[http://www.bre.com/technicalpapers/technicalpaper.asp?articlenumber=52 Selecting Amines for Sweetening Units], Polasek, J. (Bryan Research & Engineering) and Bullin, J.A. (Texas A&M University), Gas Processors Association Regional Meeting, Sept. 1994.
*[http://www.naturalgas.org/naturalgas/processing_ng.asp Natural Gas Supply Association] Scroll down to ''Sulfur and Carbon Dioxide Removal''
*[http://www.bre.com/technicalpapers/technicalpaper.asp?articlenumber=14 Sweetening LPG's with Amines], Holmes, J.W. (Bryan Research & Engineering), Spears, M.L. (Bryan Research & Engineering), and Bullin, J.A. (Texas A&M University), ''Chemical Engineering Progress'', May 1984
*[http://www.gulfpub.com/default.asp?page=14&productID=2743&VS=  Description of the classic book on gas treating] by {{cite book|author=Arthur Kohl & Richard Nielsen |title=Gas Purification|edition=Fifth Edition|publisher=Gulf Publishing|year=|id=ISBN 0-88415-2200}}
[[Category:Chemical engineering]]
[[Category:Chemical processes]]
[[Category:Oil refineries]]
[[Category:Unit processes]]
[[Category:Acid gas control]]
[[Category:Natural gas]]

Revision as of 21:47, 7 February 2008

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