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Simulation-Based Techno-Economic Assessment of a Water-Lean Solvent for Natural Gas Sweetening Technology.
* 1 , 1 , 2
1  Nile University of Nigeria
2  African University of Science & Technology (AUST)
Academic Editor: Manoj Gupta


Water-lean solvents are thought to deliver promising benefits to include enhanced mass transfer properties, increased absorption capacities and lower solvent regeneration heat duties in natural gas sweetening process. Acid gas (H2S and CO2) removal is an essential piece of the natural gas value chain due to the corrosive effect on pipeline and process equipment, impact on environment and reduction in methane heating value. A number of solvents have been used for this process in the past. However, low acid gas pickup, high cost per unit separation and high regeneration heat duties forms the basis for which we considered a water-lean solvent in this study. This study employs ASPEN HYSIS V12.1 to model natural gas sweetening process of a hypothetical non- associated sour gas well with a novel water-lean solvent (50% wt. MDEA + 30% wt. DIPA + 15% wt. DMSO + 5% wt. H2O). Theoretical solvent screening was carried out to select the most promising water-lean solvent, following a flowsheet design, modeling and result validation. The process economic analysis was carried out using Aspen Process Economic Analyzer to determine the unit separation cost and profitability indicators. Results show that the solubility of CO2 was found to be lower in water-lean solvents. The mass transfer seem not to be better. This was generally difficult to be taken into consideration and assessed properly in Aspen as there is no literature data with DMSO to fit the model parameters. DMSO reacts with H2S, leading to loss of solvent. Although, mass transfer improved with physical co-solvent, acid gas solubility decreased, resulting in more solvent consumption and impacting the capital expenditure. Economic analysis showed that the equipment cost of the proposed solvent is 1.4 M USD/yr higher than that of the aqueous MDEA commercially in use. As such, the it is not considered economically viable.

Keywords: Natural gas sweetening; separation process; solvent; Absorption; Mass Transfer