Abatement of NOx emissions at burning fuel oil in the power boiler

Abstract

Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.

This paper presents investigations towards finding new ways for the minimization of NOx emissions in the power boiler. These analyses were done in two directions: two stages of combustion into the furnace and a new system of re­-circulating gases. The purpose of carrying out both analyses had the objective of diminishing the emission of nitrogen oxides during the combustion processes. Both analyses were developed in a steam generator that currently working in the power plant "Villa de Reyes", Mexico. This steam generator Mitsubishi Heavy Industries of 350 MW is equipped with four levels of tangential burners and it bums fuel oil (C23 H37.29) during its operation. These analyses were carried out from the point of view of decreasing temperatures in the active burning zone (ABZ). The methodology is based on four main parameters related to combustion process in the furnace active burning zone (ABZ). Such parameters are the following: air excess coefficient in ABZ, average temperature in ABZ, reflected heat in ABZ and the residence time of combustion products in the ABZ. Two stage of combustion is achieved by having three levels of burners in the bottom operate rich and the top level supply air only. The first volume bums 100% of fuel oil with 75% of air. In the second volume bums 00/o of fuel and is introduced 25% of air. As a result, the decrease of NOx formation is up to 25% in comparison to current emissions. On the other hand, the thermal calculation of furnace was done, and with the results it would be possible to change the place of recirculation gases to the hot air, changing the combustion processes and move the flame core position. The changes of the parameters to calculate NOx formation are the following: different thermal loads of the power boiler from 50%, 75%, 100% and maximum load. Different fractions of recirculation gases are introduced from 23% up to 61%. As result, it is possible to decrease NOx emission up to 50% in comparison to current emissions.