Heat integration of an advanced reformer system for Gas-to-Liquid (GTL) plant: techno-economic and carbon intensity assessment

The gas-to-liquid (GTL) process remains commercially attractive for producing ultra-clean fuels from natural gas, but it is highly energy- and carbon-intensive. Natural gas reforming is the most energy- and cost-intensive process in GTL plants; therefore, this work aimed to evaluate the role of heat integration in reducing plant energy and cost requirements and in mitigating the carbon intensity of GTL fuels and other products. The study evaluates the impact of systematic heat-integration methods on two industrial-scale (50,000 bbl/day) GTL configurations: a conventional autothermal reformer (ATR) and a novel Advanced Reformer System (ARS)-based GTL plant. The ARS exhibits a substantially larger recoverable heat inventory due to internal CO₂ recycling and higher circulating mass flow, making it inherently more responsive to integration strategies. Pinch analysis and heat exchanger network synthesis were applied to both configurations, followed by a techno-economic evaluation using a 25-year discounted cash-flow model. Heat integration reduced external heating demand from 4.63 to 1.87 GW in the ATR-GTL plant case and from 9.57 to 4.39 GW in the ARS-GTL plant case, thereby significantly lowering indirect CO₂ emissions in both cases. However, only the ARS-GTL configuration yields a neutral-to-negative carbon intensity after heat integration, demonstrating that efficiency gains are achieved in sequestering CO₂ as solid carbon. Economically, heat integration increased the IRR of the ATR-GTL plant from 7% to 14%. In contrast, the ARS-GTL plant achieved an IRR of 24% by selling the carbon material (multi-walled carbon nanotubes (MWCNT)) at a conservative price of $10/kg. Sensitivity analysis revealed that the MWCNT market price has a dominant influence on profitability, whereas the heat exchanger capital cost has a minimal impact on the full-scale GTL plant. The results demonstrate that integrating heat with carbon-valorization reforming technology is essential to achieving both environmental and economic sustainability for GTL plants.