Decarbonizing the Gas-to-Liquid (GTL) Process Using an Advanced Reforming of Methane Process

Abstract

The gas-to-liquid (GTL) process is a promising technology for converting natural gas into synthetic fuels and chemicals. However, its high carbon dioxide (CO₂) emissions present significant challenges. Methane reforming contributes up to 60% of GTL’s CO₂ emissions, necessitating decarbonization. Dry reforming of methane (DRM) shows potential for CO₂ conversion. Still, it faces challenges such as high energy requirements, catalyst deactivation, and an incompatible hydrogen-to-carbon monoxide (H₂/CO) ratio for GTL processing, requiring extensive research. A previous study proposed a two-reactor system known as CARGEN that co-produces solid carbon (in the form of multiwalled carbon nanotubes [MWCNTs]) and syngas, reducing CO₂ emissions by 40% compared to the benchmark autothermal reforming (ATR) process through life cycle assessment (LCA) studies. This paper presents a comprehensive simulation of the advanced DRM process used to retrofit an existing ATR-based GTL plant─initially, a 50,000 bbl./day ATR-based GTL plant is simulated. The advanced reformer process replaces ATR through retrofitting. Comparative analysis shows a remarkable 73% reduction in net CO₂ emissions and the potential coproduction of 243 kg of MWCNTs per barrel of syncrude, equivalent to 12,150 tons/day of MWCNTs. However, the advanced reformer-based GTL plant requires 61% more natural gas feedstock while utilizing 79% less oxygen than the ATR-based plant. Furthermore, a separate techno-economic analysis examines the advanced reformer-based GTL plant based on a calculation for 13,100 tons/day of CO₂ feedstock to co-produce 3,277 tons/day of MWCNTs and 50,000 barrels/day of syncrude. This analysis, considering a 25% tax rate, 25-year plant life, and zero salvage value, demonstrates an attractive 10-year payback period at selling prices of 80 USD/bbl. for syncrude and 10 USD/kg for MWCNTs. These results provide a process system-level perspective, showcasing the advanced reformer-based GTL plant (CARGEN Process) as an effective solution for low-carbon GTL production.