Natural gas reforming for LNG and methanol production: Sustainability and economic viability

This study proposes a novel and integrated polygeneration system that simultaneously produces methanol, liquefied natural gas (LNG), crude helium, and electricity through an advanced natural gas reforming process. The system combines several subunits, including a cryogenic LNG and helium recovery unit, a syngas and methanol synthesis train, a sour water recovery section, and dual organic Rankine cycles, into a unified structure aimed at maximizing resource utilization and minimizing environmental impact. A comprehensive thermodynamic, economic, and environmental analysis reveals that the integration of a cascade of heat exchangers significantly enhances thermal performance, achieving energy and exergy efficiencies of 95.30 % and 77.17 %, respectively. While chemical reactors are identified as the primary contributors to exergy destruction (∼60 %), the sour water recovery unit demonstrates a notable sustainability benefit by providing 85.66 % of the freshwater required for reforming and synthesis processes. The system's carbon intensity is calculated at 0.11 kg CO2/kg, with indirect emissions accounting for 91 % of the total. Economically, the annual operational cost is estimated at 356.76 $M, and the methanol production cost is competitively low at 0.062 $/kg. A multi-objective optimization using the Dragonfly Algorithm further improves the system's performance, increasing energy and exergy efficiencies to 96.005 % and 79.166 %, respectively, while reducing the methanol production cost to $0.0579/kg. The proposed framework not only introduces a novel integration of resource streams but also establishes a pathway toward economically and environmentally sustainable fuel and chemical production.