Investigations on NO reduction with biomass char: Char structural changes during the heat treatment in N₂ and subsequent NO/O₂ gasification

NO reduction with biomass char was studied from considering its structural properties. Raman, XPS and XRD were employed to characterize the char structure. Three types of biomass chars were used for NO reduction at a fixed bed reactor in NO/O₂ at 900 ℃. The results showed that the heat treatment led to an obvious reordering of structures in all chars. There were significant differences between NO and O₂ reaction in terms of the char structural changes in aromatic systems, surface groups and crystalline developments. New O-containing groups were formed and could be present as C-O and –COO groups in both the NO and O₂ reactions. Two different pathways for char-NO and char-O₂ reaction were given, respectively. It is proposed that the reaction channel of NO would be blocked as carbon molecular was firstly surrounded by O₂ during NO/O₂ reaction. The denitration performance of biomass char should be linked to the structural features of char-HT and the behaviors of char structural changes in the subsequent gasification in NO/O₂.