Thermodynamic assessment of a novel liquid direct air capture system integrated with natural gas reforming for synergistic methanol production

초록

This study encompassed the development and evaluation of an integrated steam methane reforming (SMR)-direct air capture (DAC)-methanol system, wherein reformer-derived heat and gas streams are utilized to intensify DAC regeneration and enhance carbon supply for methanol synthesis. Four configurations, SMR-methanol, sweep gas-assisted SMR-DAC (SG-DAC), thermally coupled SMR-DAC (TC-DAC), and dual-mode SMR-DAC (DM-DAC), were assessed using a coupled thermodynamic and techno-economic framework, with reformer temperature and steam-to-carbon ratio identified as key operating variables. DAC integration was found to increase carbon throughput and methanol production from 275.7 mol/s in the baseline SMR-methanol case to over 371.1, 375.2, and 397.4 mol/s in the SG-DAC, TC-DAC, and DM-DAC configurations, respectively. This corresponds to production increases of 34.6%, 36.1%, and 44.1%. However, this gain shifted the system from hydrogen-surplus to hydrogen-deficient operation. Consequently, external hydrogen demand reached 25.6 mol/s in SG-DAC, 37.9 mol/s in TC-DAC, and 104.4 mol/s in DM-DAC, reflecting the increasing stoichiometric requirement associated with elevated CO2 incorporation. These process-level effects are directly reflected in the economic performance of the systems. The baseline SMR-methanol configuration remained the most favorable, with an NPV25 of $398.78millionandaTACof$86.26 million/year, whereas the DAC-integrated systems exhibited reduced profitability, with NPVs between $88.54and$210.73 million. Overall, DAC integration shifts the governing constraint from carbon availability to hydrogen supply, indicating that optimal system design requires balancing carbon utilization, hydrogen provision, thermal integration, and economic viability.

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