Helium star transform into a red giant after losing its hydrogen envelope in the future. Helium star A helium star or helium strong star is a class O or B star (blue), which has extraordinarily strong helium lines and weaker than normal hydrogen lines, indicating strong stellar winds and a mass loss of the outer envelope. "Extreme helium stars" (EHe) entirely lack hydrogen in their spectra. Previously, a "helium star" was a synonym for a B class star, but this usage is considered obsolete. A "helium star" is also a term for a hypothetical star that could occur if two helium white
Acid gas 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 HS 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