Published May 2015
Natural gas is generally defined as a naturally occurring mixture of gases containing both hydrocarbon and non-hydrocarbon gases. The hydrocarbon components are methane and the small presence of higher hydrocarbons. The non-hydrocarbon components are mainly the acid gases hydrogen sulfide (H2S ) and carbon dioxide (CO2 ) along with other sulfur species such as mercaptans (RSH), organic sulfides (RSR) and carbonyl sulfide (COS). Nitrogen (N2 ) and helium (He) can also be found in some natural gas fields. Natural gas must be purified before it is liquefied, sold or transported to commercial gas pipe line due to toxicity and corrosion-forming components. H2S is highly toxic in nature. The acid gases H2S and CO2 both form weak corrosive acids in presence of small amounts of water that can lead to first corrosion and later rupture and fire in pipelines. CO2 is usually a burden during transportation of natural gas over long distances. CO2 removal from natural gas increases the heating value of the natural gas as well as reduces its green-house gas content. Separation of methane from other major components contributes to significant savings in the transport of raw materials over long distances as well as saves from technical difficulties such as corrosion and potential pipeline rupture.
Natural gas processing projects are facing challenges due to stringent sales gas specifications and increasingly impure natural gas. The impurities such as CO2S, N2, COS, water, mercaptans and organic sulfides need to be removed from natural gas prior to its liquefaction or sales. Many natural gas resources do not contain harmfully large amounts of hydrogen sulfide but contain significant amounts of CO2 . Removal of CO2 from natural gas is a challenge in the presence of H2S , COS, and mercaptans. The conventional amine absorption methods are not suitable for natural gases containing substantial amounts of CO2 in presence of H2S , COS and mercaptans. To meet the natural gas treating challenges, Shell Global Solutions developed their second generation hybrid solvent, which is a mixture of chemical and physical solvents.
This review presents our techno-economic evaluation of Shell Global Solution’s latest natural gas treating technology, Sulfinol-X, for CO2, H2S, COS and R-SH removal from natural gas. This review also gives an overview of conventional treating technologies and the latest treating technologies for CO2 removal, mainly using absorption processes.