DESARROLLO DE UN MÉTODO PARA DISMINUIR LA FORMACIÓN DE NOx EN EL HORNO DE UN GENERADOR DE VAPOR DE 350 MW

Abstract

This thesis presents the development of a method whose purpose is to reduce emissions of nitrogen oxides (NOx) in combustion of fuel in a steam generator of 350 MW. Two such units are installed in the power plant "Villa de Reyes" in the state of San Luis Potosi, Mexico. Analysis was performed for different operating thermal loads (MRC, 100%, 75%, 50% and 25%). The proposed method employs the principle of non-stoichiometric combustion, which organizes the active combustion zone (ZCA) in the furnace of the steam generator into two combustion zones, fuelrich zone (zone I) and a zone rich in air (zone II). Two cases (case A and case B) were considered in the method. In Case A, the distribution of fuel oil is equally at the two combustion zones, while the air distribution will be non-uniformly, such that the zone I have an excess air ratio less than one, αzona_I < 1 and zone II have a coefficient of excess air greater than one, αzona_I > 1. The analysis of case B is similar to case A, the difference is that in this case the air distribution will be uniform in the two combustion zones, while the distribution of fuel oil will be uneven. The main objective of this work is to reduce maximum temperatures and thereby reduce NOx emissions. The first analysis performed in this investigation is on the distribution of air and fuel oil in the two cases (case A and case B). Then, the thermal effect is studied that the product of non-stoichiometric combustion of fuel. The final analysis is devoted to the four main parameters that influence the NOx formation and their total concentration in each case with different combinations of excess air in the combustion zones. Results obtained from the calculation of NOx concentration are compared with other techniques proposed to reduce the concentration of NOx and with the concentration of NOx when the steam generator operates without any reduction technique. The results show that the maximum reduction of NOx happens when you apply a uniform air distribution for the two combustion zones (case B), with a coefficient of excess air in zone I, αzona_I = 0.8 and a coefficient of excess air in zone II, αzona_II = 1.25