STUDY OF NO_x EMISSION AT BURNING NATURAL GAS AND FUEL OIL FOR A 32 MW STEAM GENERATOR

摘要

In this work has been developed a study of thermal processes and formation of pollutants in the furnace of a 32 MW steam generator that burns both fuel oil and natural gas. This steam generator is currently working in the thermoelectric plant "Ing. Jorge Luque Loyola" of Mexico City. The calculations were done varying the operation parameters in order to analyze the behavior of NO_x emissions. To achieve this purpose, the thermal calculations were carried out in the active burning zone (ABZ) corresponding to the furnace of the steam generator. The main parameters of operation that were analyzed are the following ones: the consumption of different fuels (fuel oil and natural gas), the variation of thermal load for steam generator from 50 percent until 100 percent and the variation of the quantity of recirculation gases from 0 percent up to 28 percent. As main results of this work it was found that changing the fuel oil to natural gas it was obtained a relative reduction of 29 percent. The best fuel was the natural gas. Also, the recirculation of gases in the duct of hot air has an effect of NO_x reduction. As reference and in order to compare the obtained results for natural gas, it was considered the case when the steam generator operates without recirculation gases and with a thermal load of 100 percent where NO_x emission is the highest value and it corresponds to 123 ppm. On the other hand, for the same thermal load and applying recirculation gases of R=0 .28, the NO_x emission was 27 ppm. Comparing the two cases it was obtained a relative reduction of 78 percent. To increase the quantity of recirculation gases provokes a decrease of NO_x emission, but it affects the operation conditions of the steam generator and the operation expenses increases. This paper presents the information of the optimum recirculation value to get lower NO_x emission than permissible limits settled down by the Environment Secretary of Mexico.