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Mitigating Sloshing Impacts on Gas Pre-Treatment In Flng Using CFD-HYSYS Coupled Analysis: A Case Study of Agung II Field

Proceedings Title : Proc. Indon. Petrol. Assoc., 48th Ann. Conv., 2024

Indonesia, with its topography characterized by an extensive land area and hundreds of islands, requires the use of a Floating Liquefied Natural Gas (FLNG) facility to process and distribute its reserves. FLNG technology offers a much smaller environmental footprint than land-based LNG plants which require major infrastructure works. A potential field for FLNG development is Agung II, a new field located offshore north of Lombok Island in an area of 7.97 sq.km. Sloshing, the movement of liquids within liquid container due to hull motions in FLNG can significantly reduce product quality particularly in the three-phase separators (TPS) and the absorber column. Previous research has demonstrated that baffle implementation in the TPS can lead to a 38% decrease in drag coefficient, as shown through Computational Fluid Dynamics (CFD) analysis. This paper further analyses the influence of baffles on TPS performance, specifically examining the impact on liquid carryover in the gas flow during sloshing conditions. CFD analysis using Ansys Fluent was conducted on TPS using two scenarios (non-baffled sloshing and baffles-controlled sloshing) that included two major stages of analysis. The gas stream coming from TPS was then introduced into the HYSYS to determine the acid gas removal efficiency. The absorption efficiency using methyl diethanolamine (MDEA) with and without an additional solvent known as piperazine (PZ) was compared. To obtain the input data for sloshing, a 100-year wave period and wind rate were forecasted. The data was used to perform analysis using Ansys Hydrodynamic Diffraction to define the response of FLNG to its environmental condition. This study found that by implementing a baffle system in the TPS, the optimal volume liquid fraction at gas outlet decreases from 0.035 to 0.008. This modification demonstrates a significant decrease of 77.7% in the sloshing impact. Additionally, combining MDEA and PZ for acid gas absorption solvent has proven to enhance the removal efficiency to 87% and 100% for CO2 and H2S, respectively.

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