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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]

Compared with other natural gas processing methods, supersonic separation technology has the advantages of small floor space, no internal moving components, and no chemical additives. At present, the research on supersonic separation technology mainly focuses on dehydration and heavy hydrocarbon removal, and there is little research on the use of supersonic separator to separate CO 2 from natural gas. In order to study the influence of nozzle structure on the supersonic swirling condensation characteristics of CO 2 , a CO 2 –CH 4 mixed gas condensation flow model was established, and the swirling condensation process of CO 2 in the supersonic nozzle was simulated by the Fluent software. The results show that the liquefaction efficiency and separation efficiency of the separator increase with the increase of the nozzle expansion section length. When there is no back pressure at the nozzle outlet, increasing the nozzle expansion angle will increase the liquefaction efficiency but decrease the separation efficiency. The nozzle designed with Witoszynski curve has the highest CO 2 liquefaction efficiency. Considering the above factors, the nozzle expansion length and angle are finally determined to be 100 mm and 3°. • The swirling condensation process of CO 2 in supersonic nozzle was simulated for the first time. • A mathematical model of condensation flow of CH 4 –CO 2 two-component mixed gas was established. • Distribution of gas parameters and CO 2 condensation parameters under different nozzle structures was studied. • Effect of nozzle structure on the liquefaction and separation properties of CO 2 was clarified. [ABSTRACT FROM AUTHOR]

Supersonic swirl separation technology has been widely used in natural gas processing and has achieved good results. However, there are few studies on the application of supersonic separation technology to the removal of CO 2 from natural gas, and the condensation rule of CO 2 under supersonic swirling flow condition is still unclear. In order to study the supersonic swirling condensation characteristics of CO 2 in Laval nozzle, the Euler mathematical model of the condensation flow of CO 2 –CH 4 two-component mixed gas was established, and the feasibility of CO 2 removal by supersonic separation technology was verified by numerical simulation. The results show that, in the process of axial flow and swirling flow, the variation trend of CO 2 condensation parameters is basically the same along the axial direction of the nozzle, but the distribution of parameters is significantly different along the radial direction. The increase of swirl intensity will increase the nozzle's liquefaction efficiency and reduce the working flow of the nozzle. The inlet temperature and inlet pressure had a significant influence on the liquefaction efficiency of the nozzle, while the inlet CO 2 content had little influence on the liquefaction efficiency. • The condensation characteristics of CO 2 in Laval nozzle under supersonic swirling flow were simulated. • The effect of cyclone on CO 2 condensation parameters was studied. • The distribution of CO 2 condensation parameters was compared in the process of swirl and axial flow. • The increase of swirl intensity will advance the condensation of CO 2 and increase the liquefaction efficiency. • The inlet temperature and pressure of supersonic nozzle affect the liquefaction efficiency. [ABSTRACT FROM AUTHOR]