Acid gas
Encyclopedia
Acid gas is natural gas
or any other gas mixture which contains significant amounts of hydrogen sulfide
(H2S), carbon dioxide
(CO2), or similar contaminants. The terms acid gas and sour gas are often incorrectly treated as synonyms. Strictly speaking, a sour gas
is any gas that specifically contains hydrogen sulfide in significant amounts; 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 but not a sour gas.
Before a raw natural gas containing hydrogen sulfide and/or carbon dioxide can be used, the raw gas must be treated to reduce impurities to acceptable levels and this is commonly done with an amine gas treating
process. The removed H2S is most often subsequently converted to by-product elemental sulfur
in a Claus process
or alternatively converted to valuable sulfuric acid
in a WSA Process unit.
Processes within oil refineries or natural gas processing plants that remove mercaptans and/or hydrogen sulfide are commonly referred to as sweetening processes because they result in products which no longer have the sour, foul odors of mercaptans and hydrogen sulfide.
Hydrogen sulfide is a toxic gas. It also restricts the materials that can be used for piping
and other equipment for handling sour gas, as many metals are sensitive to sulfide stress cracking.
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
or any other gas mixture which contains significant amounts of hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
(H2S), carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
(CO2), or similar contaminants. The terms acid gas and sour gas are often incorrectly treated as synonyms. Strictly speaking, a sour gas
Sour gas
Sour gas is natural gas or any other gas containing significant amounts of hydrogen sulfide . 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...
is any gas that specifically contains hydrogen sulfide in significant amounts; an acid gas is any gas that contains significant amounts of acidic gases such as carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
(CO2) or hydrogen sulfide. Thus, carbon dioxide by itself is an acid gas but not a sour gas.
Before a raw natural gas containing hydrogen sulfide and/or carbon dioxide can be used, the raw gas must be treated to reduce impurities to acceptable levels and this is commonly done with an amine gas treating
Amine gas treating
Amine gas treating, also known as gas sweetening and acid gas removal, refers to a group of processes that use aqueous solutions of various alkylamines to remove hydrogen sulfide and carbon dioxide from gases...
process. The removed H2S is most often subsequently converted to by-product elemental sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
in a Claus process
Claus process
The Claus process is the most significant gas desulfurizing process, recovering elemental sulfur from gaseous hydrogen sulfide. First patented in 1883 by the scientist Carl Friedrich Claus, the Claus process has become the industry standard....
or alternatively converted to valuable sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
in a WSA Process unit.
Processes within oil refineries or natural gas processing plants that remove mercaptans and/or hydrogen sulfide are commonly referred to as sweetening processes because they result in products which no longer have the sour, foul odors of mercaptans and hydrogen sulfide.
Hydrogen sulfide is a toxic gas. It also restricts the materials that can be used for piping
Piping
Within industry, piping is a system of pipes used to convey fluids from one location to another. The engineering discipline of piping design studies the efficient transport of fluid....
and other equipment for handling sour gas, as many metals are sensitive to sulfide stress cracking.
See also
- Natural gas processingNatural gas processingNatural-gas processing is a complex industrial process designed to clean raw natural gas by separating impurities and various non-methane hydrocarbons and fluids to produce what is known as pipeline quality dry natural gas.-Background:...
- Oil refineryOil refineryAn oil refinery or petroleum refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas...
- RectisolRectisolRectisol is the trade name for an acid gas removal process that uses methanol as a solvent to separate acid gases such as hydrogen sulfide and carbon dioxide from valuable feed gas streams. By doing so, the feed gas is made more suitable for combustion and/or further processing...
- SelexolSelexolSelexol is the trade name for an acid gas removal solvent that can separate acid gases such as hydrogen sulfide and carbon dioxide from feed gas streams such as synthesis gas produced by gasification of coal, coke, or heavy hydrocarbon oils...
- WSA Process