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A hydrogen purification system with a supersonic nozzle pretreatment process is proposed to improve the performance of traditional CO 2 removal processes from hydrogen-rich streams. A mathematical model of the H 2 –CO 2 double-component condensation was established to investigate the feasibility of CO 2 capture in a hydrogen-rich stream using a supersonic nozzle. Compared to the single-phase model, this model is more similar to the objective flow facts and can effectively correct the deviation of the single-phase flow model by 21.4%. Furthermore, the parameters in the H 2 –CO 2 double-components spontaneous condensation process in the nozzle were analyzed, and the microscopic mechanism of CO 2 spontaneous condensation was clarified. Finally, the effects of the inlet parameters on the carbon capture efficiency were analyzed. The results indicated that the nozzle is more suitable for purifying hydrogen-rich streams with low temperatures and high carbon content, confirming the possibility of using a supersonic nozzle as a carbon capture method. • Propose a novel CO 2 removal process in H 2 -rich streams by a supersonic Laval nozzle. • Develop a nonequilibrium condensation numerical model of CO 2 in H 2 -rich streams. • H 2 –CO 2 condensation flow model effectively corrects H 2 -rich stream flow behavior. • The H 2 -rich stream with high carbon content and low temperature is purified better. [ABSTRACT FROM AUTHOR]

Supersonic condensation separation is a potential environmentally friendly technology for hydrogen purification and CO 2 capture. The nozzle plays a crucial role in achieving CO 2 capture in practical applications. It requires specific pressure recovery abilities to deliver pre-purified hydrogen-rich fuel through downstream pipelines efficiently. However, excessive pressure recovery can quickly induce shock waves. Therefore, it is necessary to clarify the mechanisms involved in this process. This paper establishes a mathematical model for H 2 –CO 2 mixture gas condensation. It examines the energy separation effect and the interaction mechanism of boundary layer/shock wave/CO 2 phase change condensation in the pressure recovery process. The results indicate that the interaction between the boundary layer and shock wave is essential for inducing the energy separation effect. As pressure recovery increases, shock waves appear and move toward the throat, which hinders carbon capture. The maximum carbon capture efficiency decreases from 33.1% to 0%. Therefore, maintaining a pressure recovery efficiency between 33.3% and 50% is more conducive to considering nozzle pressure recovery and CO 2 condensation separation. [Display omitted] • Develop a nonequilibrium condensation numerical model of CO 2 in H 2 -rich fuel. • Potential hydrogen purification and carbon capture approach. • Clarify the energy separation effect and the interaction mechanism in Laval nozzle. • Reducing pressure recovery efficiency conduces to improve carbon capture effect. [ABSTRACT FROM AUTHOR]