Efficient Scheme for Native Carbon Dioxide Recovery from Sulphur Recovery Unit Tail Gas

Abstract

Oil and Gas operators are more and more interested in developing and improving native CO2 recovery technologies as capturing native CO2 can drastically reduce the greenhouse gases emission and at the same time can be valorized for enhanced oil recovery. While considering CO2 emission from a gas plant, native CO2 significantly contributes to the total amount. Usually when natural gas contains both CO2 and H2S, they are removed together and sent to an air fueled Sulfur Recovery Unit (SRU) resulting in a tail gas containing mainly nitrogen and CO2. The native CO2 can then be separated by the use of a chemical solvent such as Monoethanolamine (MEA) for example. TOTAL and Air Liquide Engineering & Construction have developed and patented an innovative process scheme for recovering the native CO2 and reducing the overall operating and investment costs of such process. This patented innovative process scheme consists in a Claus unit, fed with pure oxygen or enriched air instead of air, which leads to a tail gas stream containing mainly CO2 and H2 but no or only little nitrogen. A CO2 purification unit allows a CO2 rich stream to be recovered with a purity level reaching even 99.9%, while producing valuable by-products such as pure nitrogen and a hydrogen-rich stream, both of which can be used as utilities in other process units depending upon selected technology. This also reduces continuous emissions from the gas plant by eliminating the continuous operation of an incineration system. The CO2 purification unit can be either membrane, cryogenic or adsorption technologies. This paper also discusses the integration of the technologies of Air Liquide Engineering & Construction: OxyClausTM, Tail Gas Treatment Unit (TGTU) and CryoCapTM, a very efficient CO2 purification technology. The scheme has been studied in detail for specific application to optimize the overall integration. It has been also compared to conventional CO2 capture schemes.