The arch-fired boiler studied in this project suffered from a high material fatigue in certain parts due to the high temperatures achieved by the combustion gases, which in turn forced to make non-planned stops of the station. Besides avoiding this problem, we aimed to lower the nitrogen oxides (NOx) emission by means of primary measures (changes in the operating conditions) or modifications requiring a low investment.
In this project we collaborated directly with the technical staff at the power station regarding the decision making. To this end, we developed a CFD model that involved the simulation of the secondary air distribution in the windbox and the combustion in the furnace. The model allowed to evaluate the effect of the options considered regarding the fatigue problems in the boiler and the NOx emissions.
In a short lapse of time, a number of measures were virtually tested using the computational simulation tool, choosing the most effective ones to be implemented. Thus, during a service stop, several minor modifications were carried out in the windbox and the boiler operation conditions (damper positions in the windbox and primary air/coal distribution) were modified. As a result, the NOx emissions were reduced by a 40%, while keeping unaltered the thermal efficiency, besides avoiding the previous fatigue problems.
Moreover, after the end of the project, the technical staff at the plant has at their disposal a simulator that allows them to analyze possible future changes in the boiler operation.