The objective of this paper is to present new improvements in the knowledge of the performance of an Acid Gas Removal Unit (AGRU) installed on a floating gas production facility, thanks to a R&D program testing the influence of 3D motions and accelerations.

The accurate design of the Acid Gas Removal Unit has a great importance for the profitability and success of a FLNG project. In order to limit both weight and footprint, it shall rely on the lowest possible solvent flowrate and on the minimal and optimum equipment size to treat the feed gas while taking into account motions of the floating support. The proposed paper will demonstrate how a tight but safe design of an amine unit can be proposed thanks to the results of an extensive experimental program.

Total, Prosernat and IFPEN have conducted a four-year R&D program at Heriot-Watt University based on pilot tests aiming at modelization of mass transfer and hydraulics of tilting and moving towers. This program has included the testing of multiple parameters such as liquid/gas flowrates, liquid viscosity, diameter of towers, height of packing beds, packing efficiency. This has been done under various conditions: static tilt, pitch and 3D motions generated by a hexapod robot with six degrees of freedom. The motion conditions tested were similar to those experienced by a column installed on a floating gas production support or on a FLNG.

The collected information on hydraulics and mass transfer showed a significant impact of motions on liquid and gas distribution along the packing beds that can, under conditions of loads of gas and liquids, lead to a significant loss of absorption performances. An in-depth analysis of the large experimental data set with a comprehensive understanding of the phenomena in place allowed the development team to propose a robust model. This model is now embedded in a rated base mass transfer proprietary simulator of AGRU that can predict with good accuracy the impact of motions of the floating support on the performance of the unit.

This paper will present key results accumulated along the program about the impact of motions on liquid/gas maldistribution along a packing bed. It will explain how the accumulated knowledge enables to size tight but reliable AGRU's for installation on a floating support, in the presence of CO2, but also of other contaminants like H2S. The discussion will be supported by comprehensive examples of degradation of the absorption performances on real cases affected by sea motion.

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