## 5 Conclusions  
A dynamic adsorption model for a lean hydrogen mixture (N\({}_{2}\)/CO\({}_{2}\)/H\({}_{2}\)/CO = 44.6 /35.4/19.9/0.1 mol%) on an AC/zeolite 13X layered bed was developed and validated against experimental data. Building on this, a dual-bed, six-step PSA cycle model was implemented using the Aspen Adsorption platform to study the influence of key operating parameters, including the feed pressure, flow rate, AD time, P/F ratio, and AC/zeolite 13X ratio. The following conclusions are drawn:  
1. Increasing the feed pressure and decreasing the feed flow rate delay the breakthrough of impurity gases in the adsorption bed. A higher pressure enhances impurity gas adsorption and improves purity but reduces recovery due to greater feed gas consumption. A higher feed flow rate boosts recovery by processing more gas but reduces purity due to insufficient gas-adsorbent contact.
2. Extending the AD time improves recovery but may lead to early adsorbent saturation and reduced purity. A higher P/F ratio increases hydrogen usage during the purge step, enhancing purity but lowering recovery.
3. The performance of a layered bed is superior compared with that of an AC or zeolite 13X single-layer bed. Within a certain range, increasing the proportion of zeolite 13X on the layered bed can enhance the dynamic separation of impurity gases across the entire adsorption bed, further improving the overall purification performance. The highest purity of 97.38% and highest recovery of 49.13% occur at AC/zeolite 13X ratios of 5:5 and 3:7, respectively. This study offers guidance for designing operation parameters and bed structures in PSA processes. Future work will expand the scope of parameter studies to better reflect  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Run**} & \multicolumn{2}{c}{**Operating Condition**} & \multicolumn{3}{c}{**Bed Configuration**} & \multicolumn{2}{c}{**Performance**} \\ \cline{2-9}  & **Feed Pressure [Bar]** & **Feed Flow Rate [LSTP/min]** & **AD Time [s]** & **P/F Ratio** & **AC/Zeolite 13X** & **Purity [\%]** & **Recovery [\%]** \\ \hline  
\hline \hline \end{tabular}
\end{table}
Table 4: Summary of the results of parametric studies.  
industrial-scale conditions and evaluate PSA performance from multiple perspectives, including hydrogen productivity and energy consumption. Moreover, the commonly observed trade-off between purity and recovery highlights the need for further multi-objective optimization.  
Conceptualization, C.L. and L.T.; methodology, T.Y. and Z.Y.; software, Z.Y.; validation, X.L.; formal analysis, B.C.; investigation, B.C.; resources, C.Y. and J.X.; data curation, L.T.; writing--original draft preparation, T.Y. and Z.Y.; writing--review and editing, C.L. and J.X.; visualization, Y.Y.; supervision, C.Y.; project administration, T.Y. and Y.Y.; funding acquisition, C.L., L.T., and X.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Natural Science Foundation of Hubei Province of China (2025 AFB665), the National Natural Science Foundation of China (52176191 and 51476120), the Master's and Doctoral Special Project (2023 whcvc605), and the Research Innovation Team Project of Wuhan City Polytechnic (2023 whcvcTD01 and 2023 whcvcTD02).  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.  
The authors declare no conflicts of interest.