Capturing in Gas Treating Plants Technology Review and Selection

Abstract Increase in the requirement of reduction of CO2 emission / carbon footprint demands the need for CO2 capturing units in existing gas treatment facilities. The location of the CO2 capturing unit in the sour gas treating plant have economic impact with respect to CO2 recovery and unit technical cost (UTC). A case study is presented to demonstrate the optimum location of the CO2 recovery unit with available licensed technology. Based on production profile and composition for Asab 1 & 2, the potential acid gas removed from acid gas removal unit (AGRU) is quantified. The amount of CO2 in acid gas to be recovered in view to having a SRU unit, had the choice of CO2 recovery from: (1) low pressure amine based CO2 capturing units, (2) high pressure CO2 capturing units based on amine / physical solvents, or (3) CO2 recovery from tail gas of sulphur recovery unit (SRU). A technology selection study was carried out to select appropriate technology for CO2 capture with optimum unit technical cost (UTC). The study findings are summarized as below: Low pressure amine based CO2 recovery unit, along with the tri-ethylene glycol (TEG) based CO2 dehydration and conditioning and CO2 pumping / compression units configuration, is considered to have optimum unit technical cost (UTC). The low pressure amine based CO2 recovery unit acts as an acid gas enrichment (AGE) unit upstream of the sulphur recovery unit (SRU). As the CO2 is recovered, the total enriched acid gas feed (with higher H2S concentration) to sulphur recovery unit will reduce, hence the size of the sulphur recovery unit (SRU) will come down.Tri-ethylene glycol (TEG) based CO2 drying technology is considered with advantage over other available technologies like mole sieves, membrane based process etc. The CO2 capturing unit scheme selected during the conceptual design stage will be further developed in detail during the FEED stage. The CO2 recovered will be utilized for enhanced oil recovery, which will aid increased oil production and value to the company. As the CO2 recovery unit is planned along with SRU, the CO2 emission from the SRU unit will also be reduced.