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• A new method is proposed to calculate characteristic chemical reaction time scales by partition PCA method for MILD combustion. • The partition PCA method segments combustion regions based on reaction intensity and extracts characteristic chemical time scales for each region. • Revealed a closer alignment with the inherent nature of MILD combustion, by applying the method to a CH4/H2 mixture in both MILD and standard combustion processes. MILD combustion represents a more moderated reaction process in contrast to traditional combustion. The employment of hydrogen-containing syngas as fuel introduces a spectrum of intricate and diverse chemical reactions. This complexity renders traditional reliance on characteristic chemical timescales less appropriate for the analysis and modeling of Moderate or Intense Low-oxygen Dilution (MILD) combustion phenomena. In response to this inadequacy, a new technique named the partition Principal Component Analysis (PCA) method was developed. This method begins by segmenting combustion regions based on the reaction intensity, then extracts characteristic chemical time scales for each of these individual regions through the application of the PCA method. The innovative method was subsequently applied to investigate the chemical traits of the CH 4 /H 2 mixture in both MILD and standard combustion processes with respect to the time scale. The insights obtained from this novel approach demonstrate that the characteristic chemical time scales (τ c) deduced through this methodology exhibit a more accurate representation of the intrinsic characteristics of MILD combustion within the reaction region. This approach enhances the comprehension of the interplay between turbulence and chemistry in MILD combustion contexts. Furthermore, it establishes a solid groundwork for forthcoming research endeavors in the field of MILD combustion. Furthermore, the τ c calculations presented in this paper have been derived mathematically, confirming their widespread applicability. [ABSTRACT FROM AUTHOR]

• A novel full 3D Eulerian porous medium model is developed for the CO 2 capture process in a RPB. • The hydrodynamics, thermodynamics and chemical-enhanced mass transfer in the RPB are effectively and accuartely analyzed. • The mass transfer in the packing region and outer cavity zone is quantitatively evaluated under various operating conditions. • The model paves the way for scaling up and process optimization of RPBs for industrial post-combustion carbon capture. Rotating packed bed (RPB) technology shows great potential for post-combustion capture. However, the capture process inside the full RPB is difficult to simulate, due to the complexity of the process and the neglect of the CO 2 capture in the outer cavity zone. In this paper, a full 3D CFD model, including the packing and the inner and outer cavity zones, has been established employing the Eulerian porous medium method coupled with various sub-models. The CO 2 capture performance in the packing and outer cavity zones has been quantitatively analyzed under different operating conditions. The simulation results show good agreement with the experimental data, and the contribution of the outer cavity zone to the CO 2 capture of the RPB is in the range of 28 %∼42 %. This work provides a new approach to efficiently simulate the mass transfer process in the RPB. [ABSTRACT FROM AUTHOR]