Study on differential effects of supersonic separation technology in the decarbonization processes of two typical clean energy sources: Hydrogen and natural gas

Abstract

This study investigates the differential effects of supersonic separation technology on decarbonization processes in hydrogen and natural gas systems by developing a multi-physics numerical model incorporating nucleation-droplet growth dynamics. Focusing on the thermodynamic-kinetic coupling mechanisms during CO₂ non-equilibrium condensation, the research reveals how carrier gas properties (hydrogen and methane-dominated natural gas) govern phase transition efficiency under supersonic conditions. Key findings demonstrate that, due to hydrogen's high thermal conductivity and weak intermolecular interactions, hydrogen-rich systems are more prone to forming a large number of small-radius CO₂ liquid droplets in supersonic nozzles compared to natural gas systems. When the inlet temperature is maintained at 270 K, during the process where the molar fraction of CO₂ increased from 0.25 to 0.35, the liquid phase mass fraction of carbon dioxide in the natural gas system increased by 1.44 times, significantly higher than 1.21 times in the hydrogen-rich system. Under a constant CO₂ concentration of 0.3, when the inlet gas temperature decreases from 275 K to 265 K, the growth rate of liquid-phase components in hydrogen-rich systems shows a 20.5 % reduction compared to natural gas systems. Natural gas systems leverage nucleation-density coarsening trade-offs for rapid efficiency gains, while hydrogen systems face diffusion-limited growth constraints. The work establishes a supersonic carbon capture framework rooted in phase-change dynamics, proposing specific strategies: cryogenic process intensification for natural gas decarbonization and supersonic-driven thermal balancing for hydrogen purification, to address nucleation suppression and mass transfer constraints inherent to supersonic separation systems, thereby enhancing CO₂ condensation efficiency under non-equilibrium conditions.