these intermediates are oxidized into NOx promptly during the volatile combustion via the schematic reaction (5). Meanwhile, partial NOx can be reduced into N2 by NH3, HCN, CxHy and Char via the schematic reaction (6) and, during the char combustion the char-N is then oxidized into NOx through the schematic reaction (7) which also can be partially reduced into N2 via the schematic reaction (6).