INFLUENCE OF FURNACE COMBUSTION CONDITIONS ON NOX EMISSION FROM LIGNITE FLAMES

Coal combustion in boiler furnaces is followed by emission of pollutan ts, i.a. NOx compounds. The appropriate activities have been conducted lately for lowering this emission and satisfying the ecology requirem ents. Therefore, the knowledge of NOx formation mechanism in furnace c onditions is of great importance. In the paper presented are the resul ts of an application of the developed model on the computation of the chemithermodynamic equilibrium of a system formed by compounds and ele ments contained in the Kolubara basin lignite and the combustion air, at temperatures from 800 to 1700 K, pressure 1 bar, for two lignite co mpositions at excess air alpha = 1,25. The briefly outlined developed mathematical model used for shaping the computation algorithm takes in to account only the thermal oxides formation mechanism which is for Ko lubara lignites, having low nitrogen content, the dominant NOx formati on mechanism even at lower combustion temperatures. The results obtain ed are of use, as thermodynamic indicators, for lowering NOx emission by adequately organizing and conducting the combustion process, i.e. b y preventing formation of temperature zones with NOx emission above th e allowed values. A sample computation of the equilibrium composition of the system has been performed for the stoichiometric combustion cas e, thus illustrating the possibility of NOx emission lowering by apply ing the so-called sub-stoichiometric combustion.