Technical Evaluation of the Applicability of Gas-Liquid Membrane Contactors for CO₂ Removal from CO₂ Rich Natural Gas Streams in Offshore Rigs

Abstract

This work aimed to fulfill a technical evaluation of the applicability of gas-liquid membrane contactors (GLMC) to remove CO2 from CO2 rich natural gas in offshore rigs. For this purpose, a simulation case in HYSYS 8.8 (AspenTech) was performed to remove CO2 from a natural gas stream with concentration of 40% mol CO2 using an aqueous solution of monoethanolamine (MEA) 30% w/w. GLMC unit operation is not available in HYSYS, though. Hence, it was necessary to develop a mathematical model based on log-mean of differences of CO2 fugacities in both phases. Moreover, a GLMC Unit Operation Extension (UOE) was created for GLMC units to run in the process simulator HYSYS 8.8 using its thermodynamic infrastructure. The developed GLMC unit operation extension performed accordingly to the expected behavior. For a gas feed flow rate of 5 MMNm3/d (typical from FPSO's), the calculated total GLMC mass transfer area was 1,986 m2, which requires 14 GLMC modules. Consequently, this operation showed to be a feasible option for CO2 removal in natural gas conditioning on offshore rigs. The heat ratio in the reboilers of CO2 stripping columns was found to be 167 kJ/mol, compatible with data found in the literature of CO2-MEA-H2O systems.