A multi-scale model for syngas combustion on NiO oxygen carrier for chemical looping combustion: The role of nearest neighbors

Abstract

A multi-scale modelling study was conducted to determine the neighboring effects on syngas combustion on a NiO oxygen carrier-based CLC process. According to the activation energy analysis, CO oxidation was slightly weakened by CO neighbors and enhanced by H2 neighbors. The three-step H2 oxidation process generally benefits from the neighboring effects. A combined electronic analysis confirmed these observations. A DFT-based kMC multi-scale model, verified by experimental results, was developed to estimate the neighboring effects under practical operating conditions. The results showed that the system was most significantly affected by the neighboring effects on CO adsorption, whereas the neighboring effects on the CO oxidation led to an almost negligible change. The effects caused by the neighboring effects showed that this phenomenon is critical to capture the system performance. A DFT-based MF multi-scale model that considers neighboring effects was built to quantitatively predict the system's behavior at larger time scales.