Sour gas
Sour gas is natural gas or any other gas containing significant amounts of hydrogen sulfide (H2S). Natural gas is usually considered sour if there are more than 5.7 milligrams of H2S per cubic meter of natural gas, which is equivalent to approximately 4 ppm by volume.[1][2]. On the other hand, natural gas that does not contain significant amounts of hydrogen sulfide is called "sweet gas."
Although the terms acid gas and sour gas are sometimes used interchangeably, strictly speaking, a sour gas is any gas that specifically contains hydrogen sulfide in significant amounts, whereas an acid gas is any gas that contains significant amounts of acidic gases such as carbon dioxide (CO2) or hydrogen sulfide. Thus, carbon dioxide by itself is an acid gas, not a sour gas. In addition to being toxic, hydrogen sulfide in the presence of water also damages piping and other equipment handling sour gas by sulfide stress cracking. Natural gas can contain several ppm of volatile sulfur compounds, but gas from some wells have been known to contain 90% hydrogen sulfide.[3]
Methods for sweetening
Before a raw natural gas containing hydrogen sulfide or carbon dioxide can be used, the raw gas must be treated to remove those impurities to acceptable levels by H2S scavengers, commonly through an amine gas treating process for high gas rates.[1][4] The removed H2S is most often subsequently converted to by-product elemental sulfur in a Claus process or it can be treated in a WSA Process unit where the by-product is sulfuric acid. Alternatively, the highly H2S concentrated gas, the by-product of the amine treatment plant, can be recompressed by compressor units specifically designed to handle highly toxic gas and injected in the reservoir.
Within oil refineries or natural gas processing plants, the removal of organosulfur compounds and hydrogen sulfide is referred to as "sweetening". The sweetened products lacks the sour, foul odors of mercaptans and hydrogen sulfide. Another product removed in sweetening is carbonyl sulfide.[3]
See also
References
- ↑ 1.0 1.1 NaturalGas.org website page Processing Natural Gas
- ↑ Air Dispersion Modeling Conversions and Formulas
- ↑ 3.0 3.1 Georg Hammer, Torsten Lübcke, Roland Kettner, Mark R. Pillarella, Herta Recknagel, Axel Commichau, Hans-Joachim Neumann and Barbara Paczynska-Lahme "Natural Gas" in Ullmann's Encyclopedia of Industrial Chemistry, 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a17_073.pub
- ↑ Energy Information Agency website page Natural Gas Processing: The Crucial Link Between Natural Gas Production and Its Transportation to Market
