A big amount of sulphur's derivative is recovered every year without the formation of elemental sulphur. In such operations sulphur dioxide (SO2) are the main derivative instead of H2S. This SO2 is usually converted into sulphuric acid. It is not reduced elemental form because of high expensiveness. Main sources of this SO2 are nonferrous sulfides ores including nickel, zinc, copper lead etc. Recovery of contained sulphur is increasing continuously because of the air quality requirement at nonferrous smelters.
Another source of SO2 is pyrites. Particularly China, Spain and some other parts of world, Pyrites have been a main source of sulphur. Currently it is playing main role in sulphur production in the countries including China, Finland and Russia. In recent years, for economic reasons it has been declined as a source of sulphur values.
H2S is another source but its not used directly to be converted to elemental sulphur. It's first converted to sulphuric acid or used as starting material in suflur compounds. Only acid plants capable of sing wet SO2 streams can use H2S directly.