(55a) Optimizing Environmental and Energy Efficiency While Enhancing Product Selectivity in a Gas-to-Liquid (GTL) Process

Refineries contribute towards approximately 1.3 billion metric tons of CO₂ emissions annually, representing about 4-6% of global emissions. Achieving net-zero targets and advancing energy transition goals requires reducing the carbon intensity of these refining processes. One potential solution involves retrofitting existing refineries to run on renewable energy sources and produce sustainable, non-combustible products and intermediates. This approach aligns with the vision of the "refinery of the future," which focuses on reducing environmental impact while addressing future energy demands and product requirements.

The Gas-to-Liquid (GTL) process begins with a reforming step, where natural gas is converted into syngas, a mixture of carbon monoxide and hydrogen. The produced syngas is then directed to the Fischer-Tropsch (FT) synthesis unit, which transforms it into longer-chain hydrocarbons. These hydrocarbons are subsequently refined into fuels and value-added chemicals that can be used in a variety of applications, including transportation, industrial operations, petrochemical feedstocks, lubricants, and specialty chemicals. Among these stages, reforming is the largest source of emissions, contributing approximately 50-60% of the total CO₂ emissions in the GTL plant. This makes the reforming step a prime target for emission reduction efforts within the GTL process.

This study investigates the development of retrofit scenarios aimed at decarbonizing the reforming sections of existing Gas-to-Liquid (GTL) plants from their direct and indirect emissions. Moreover, the downstream refining and upgrading processes are modified for further CO₂ reduction. Multiple process scenarios are explored and evaluated based on their technical and economic feasibility, as well as their environmental impact. The scenarios include innovative approaches such as feedstock modification for the provision of syngas, carbon capture, utilization and storage (CCUS), and the integration of renewable energy sources. Initial assessment of the base case scenario’s CO₂ emissions shows that 91.09 kgCO₂e/MJ is produced. Preliminary results suggest adding a CCUS unit reduced the emissions by 60.73%. Moreover, the integration of an electrolyzer into the system can further reduce emissions. Current efforts include evaluating the emissions to compare the different retrofit scenarios and evaluating their emissions. This analysis not only identifies key parameters and configurations for effective decarbonization of the GTL process but also provides a foundation for future advancements in carbon-neutral refinery technologies.