Development of CO_2 Tolerant LNG Production System

摘要

During LNG liquefaction, CO_2 component in natural gas has to be removed completely to prevent icing andrnplugging in the system. The CO_2 removal system may be the most important part in gas treatment system.rnAcceptable CO_2 level of typical 50 ppm in feed gas is very stringent and hard to meet. H_2O in feed gas is relativelyrneasily removed by molecular sieve type dehydration system. However, CO_2 removal system requires complicatedrnamine contactor and regeneration system with substantial heat source. Especially in floating environmentrnoperation, reducing CO_2 level could be the most critical part of the FLNG availability, consequently, continuationrnof LNG liquefaction operation in severe weather condition may be determined by the CO_2 removal capability,rnwhereas the cryogenic liquefaction part may affect production performance only. DSME has developed highlyrnefficient and CO_2 tolerant LNG liquefaction system called "Cluster LNG" with increased pressure liquefaction andrnassociated containment system. The developed system accepts approximately 1% of CO_2 for the liquefaction andrnrelated systems. The CO_2 tolerant characteristics of the liquefaction process will provide multifold safety marginrnagainst CO_2 problems in cryogenic systems and valves. Moreover, when CO_2 level is less than 1%, the CO_2rnremoval system may be eliminated from the liquefaction plant. Extensive verification tests of different CO_2rncontents in the developed process have been carried out, and found that experimental results are well coincidentrnwith theoretical expectations. In addition, CO_2 removal system and related tests have been carried out. From thernexperiment, possibility of CO_2 removal system (CO2 2 ～ 5%) other than traditional amine base system has beenrninvestigated and new concept CO_2 removal system is being developed. The non-conventional CO_2 removalrnsystem, which includes icing and solid removal with hydro-cyclone, is being tested in a bench scale pilot plant.rnThe new CO_2 removal system combined with increased pressure liquefaction process will bring competitivenessrnin natural gas liquefaction. The developed system may accelerate monetization of stranded gas fields with lowrnunit liquefaction and gas treatment cost.