(en) In the combustión process, the formation of NOx is caused by a Chemical reaction of oxygen with nitrogen present in both air and fuel during combustión. Depending on the source of nitrogen, two mechanisms have been proposed : (i) thermal NOx, (ii) fuel NOx. The formation of thermal NOx takes place through the reaction between N2 and O2 at high temperature. The rate of thermal NOx formation depends on temperature and oxygen concentration. By increasing the fíame temperature and oxygen concentration, the contribution of thermal NOx represents most of the total NOx formed for fuel containing no inherent nitrogen. For coal and heavy fuel oil combustión, approximately 20-50% of total NOx is due to the thermal NOx mechanism
Jung, S. M. (2001). Development of high temperature De-NO(x) catalysts suitable for simultaneous DE-NO(x) and DE-SO(x) process. https://hdl.handle.net/2078.5/124223