A thermodynamic analysis of the fuel synthesis system with CO₂ direct captured from atmosphere

Hydrocarbon fuel synthesis with renewable energy and captured CO₂ is a promising option for CCU and an important approach to sustainable energy. Like photosynthesis of plants, the technology of CO₂ direct captured from atmosphere with CO₂ utilization would close the carbon cycle thoroughly. Because of the dilute CO₂ in the atmosphere, the air capture process faces the challenge of high energy penalty. However, integrated with fuel synthesis process, the air capture process can take advantage of the waste heat produced by syngas production process and the transportation of CO₂ can also be avoided. In this study, a thermodynamic model of the fuel synthesis system is built through energy and exergy analysis. The thermodynamic contribution of three typical CO₂ capture technologies, moisture swing air capture, high-temperature swing air capture and traditional amine-based flue gas capture, is studied using the model built. Furthermore, by the sensitivity analysis of the critical parameters of the capture, electrolysis and heat exchange process, the influence of each process on the performance of fuel synthesis system is examined and the approach to improve the efficiency of the total system is proposed.