Acid gas
Acid gasis a particular typology ofnatural gasor any othergasmixturecontaining significant quantities ofhydrogen sulfide(H2S),carbon dioxide(CO2), or similaracidicgases. A gas is determined to beacidicor not after it is mixed with water. ThepH scaleranges from 0 to 14, anything above 7 is basic while anything below 7 is acidic. Water has a neutral pH of 7 so once a gas is mixed with water, if the resulting mixture has a pH of less than 7 that means it is an acidic gas.[1]
The term/sacid gasandsour gasare 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 ofacidicgases such ascarbon dioxide(CO2) or hydrogen sulfide. Thus, carbon dioxide by itself is an acid gas but not a sour gas.
Dangers of acid gas
[edit]Once a process burns a gas containing an acidic mixture, that acid gas is released into the atmosphere. This causes one of manufacturing's most detrimental effects on the environment,acid rain.The acidic gases burned from onepower plantcan travel hundreds of miles after the gas mixes with water molecules in the atmosphere. The compounds then fall to the earth again in different forms of precipitation (acid rain) and can cause respiratory health issues in humans, kill plants and wildlife, erode structures and buildings, and contaminate water sources.[2]
Acid gases are also hazardous in other ways than polluting the environment. Acid gases can be extremelyflammableandexplosiveunder pressure, so must be kept away from heat, sparks, or open flames.[3]
Hydrogen sulfide is atoxicgas, it can cause breathing problems and asphyxiation. It also is very corrosive to metals[3]which restricts the materials that can be used forpipingand other equipment for handling sour gas, as many metals are sensitive tosulfide stress cracking.
Carbon dioxide at concentrations of 7% to 10.1% causes dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour. Concentrations above 17% are lethal when exposed for more than one minute.[4]
Processing and safety
[edit]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 anamine gas treatingprocess.[5][6]There are physical and chemical absorption processes to removing the toxic properties of these gases, both of which involve thesyngasbeing washed with a lean solvent in an absorber to remove the H2S.[7]Once the toxic gas leaves the bottom of the absorber it is sent to a regenerator where the solution is further stripped with steam under extremely lower pressures to remover thesulfurfrom the gas.[8]The removed H2S is most often subsequently converted to by-product elementalsulfurin aClaus processor alternatively converted to valuablesulfuric acidin aWSA Processunit.
Processes within oil refineries ornatural-gas processingplants that removemercaptansand/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.
See also
[edit]References
[edit]- ^"Acidic Gases Examples and List | Gaseous Acids".
- ^"Acid Rain | Adirondack Council".
- ^ab"Safety Data Sheet: Whiting Acid Gas"(PDF).Whiting.Archived(PDF)from the original on 2022-05-21.Retrieved2022-10-31.
- ^ U.S. Environmental Protection Agency:"Carbon Dioxide as a Fire Suppressant: Examining the Risks"
- ^NaturalGas.org website pageArchived2011-01-01 at theWayback MachineProcessing Natural Gas
- ^Energy Information Agency website pageArchived2011-03-04 at theWayback MachineNatural Gas Processing: The Crucial Link Between Natural Gas Production and Its Transportation to Market
- ^"6.2.1. Acid Gas Removal (AGR)".
- ^"6.2.1. Acid Gas Removal (AGR)".