Natural gas removal of hydrogen sulphide and mercaptans

Methane is the main component of natural gas but not the only one. In fact in natural gas are usually present also higher alkanes (ethane, propane, butane, and pentanes), water, nitrogen carbon dioxide and sulphur containing molecules.Within sulphur containing molecules the most abundant is hydrogen sulphide, but mercaptans, elemental sulphur and, less frequently, carbonyl sulphide may also be present.The treatment of natural gas in order to remove sulphur containing compounds is dependent not only on the quantity of these compounds but also on the volume of natural gas to be treated.In this review, will be illustrated the main industrial processes to remove H2S, in large (more than 20 ton sulphur/day), intermediate (20 kg sulphur/day < quantity <20 ton sulphur/day) and small amounts (lower than 20 kg sulphur/day). Mercaptans removal methods according to their molecular weight and content will be discussed.

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► Processes for removal of H2S from natural gas can be divided according to the quantities of H2S (large, medium, small).
► Large quantities of H2S are removed through Claus and related processes (Superclaus, SCOT).
► Intermediate quantities are removed through liquid phase (Locat, Sulferox, Sulfint, Bio-redox, Chemical redox etc.) or non aqueous phase processes (Sulfatreat DO, Crystasulf etc.).
► Small quantities are removed by scavengers.
► Large quantities of mercaptans are removed through extraction processes (Merox extraction, Merichem extraction) while small quantities are removed by scavengers.