Sustainable offshore natural gas processing with thermodynamic gas-hydrate inhibitor reclamation: Supersonic separation affords carbon capture

• Published in: Chemical engineering research & design 2022-05, Vol.181, p.55-73
• Main Authors: Teixeira, Alexandre Mendonça, Arinelli, Lara de Oliveira, de Medeiros, José Luiz, Araújo, Ofélia de Queiroz F.
• Format: Article
• Language: English
• Subjects: Carbon sequestration; Cleaner natural gas processing; CO2 capture; Combustion; Dew; Dew point; Emissions control; Ethanol; Gas hydrates; Inhibitors; Liquefied natural gas; Multi-criteria sustainability analysis; Multiple criterion; Natural gas; Offshore drilling rigs; Post-combustion carbon capture; Power consumption; Profitability; Reclamation; Separation; Separators; Supersonic separator; Sustainability; Thermodynamic hydrate inhibitor; Thermodynamics; Water injection
• ISSN: 0263-8762; 1744-3563
• DOI: 10.1016/j.cherd.2022.03.006

[Display omitted] •Gas-processing routes studied: conventional and SS-THI-Reclamation with CO2 capture.•SS-THI-Reclamation recovers methanol/ethanol/MEG from gas via supersonic separation.•SS-THI-Reclamation has −41% power demand, +10% revenues and +3% net present value.•SS-THI-Reclamation leverage affords post-combustion capture of 43% of CO2 emissions.•SS-THI-Reclamation with carbon capture is the most sustainable raw-gas processing. Dew-point adjustments and reclamation of thermodynamic gas-hydrate inhibitors injected in subsea flowlines are common operations in offshore natural gas rigs characterized by high costs, power consumption and carbon emissions. Typically, offshore plants employ triethylene-glycol absorption for water dew-point adjustment and Joule–Thomson expansion for hydrocarbon dew-point adjustment, while hydrate inhibitor reclamation is applied only on aqueous-inhibitor streams for re-concentration. To implement economically sustained post-combustion carbon capture on offshore rigs, a more efficient gas processing is necessary. This work contemplates a new process – supersonic separator inhibitor-reclamation – which recovers inhibitors from saturated raw-gas via supersonic separation with liquid-water injection additionally yielding exportable liquefied-petroleum-gas and natural gas with adjusted dew-points. This process dramatically improves profitability for thermodynamic inhibitors methanol, ethanol and monoethylene-glycol, creating an economic leverage that affords a post-combustion capture plant avoiding about 43% of carbon emissions. Even including post-combustion capture penalties, the supersonic separator inhibitor-reclamation process achieves a higher net value than the conventional gas processing without carbon capture. A multi-criteria sustainability assessment, based on quantitative metrics and qualitative aspects over all sustainability dimensions, evinces the supersonic separator inhibitor-reclamation process with carbon capture as more sustainable than the conventional counterpart for all inhibitors, whereas among the three inhibitors, the gas processing with monoethylene-glycol was ranked as the more sustainable for offshore rigs.