This project had as a main objective the reduction, by means of primary measures (changes in the operation) or minor modifications, of the NOx emission in a front-wall-fired coal boiler of a power station. Besides, the reduction of the emissions should not affect its efficiency (heat transfer, unburnt coal).
To this end, we supported the technical staff at the power station regarding the decision making based on simulations made with CFD models, evaluating different options considered. A comprehensive model was developed, including the windbox air distribution, the combustion in the furnace and the heat transfer at the heat recovery zone.
This model was used as a boiler simulator that allowed to evaluate any change in the operating conditions or geometrical modifications, such as changes in the air rotation, air and coal distribution among the burners or the use of other types of coal, thus allowing to study their influence on the NOx emission and the heat transfer.
Then, previous to the implementation of changes in the plant operation, their effect was tested with the virtual model of the boiler. This allowed us to choose the optimal actions and reduce the execution times, besides providing confidence to the technical staff responsible for the decision making.
This project, executed in a relatively short period of time, managed to reduce the emission of NOx in the boiler over a 50% in respect to the original operation, keeping unaltered the thermal performance and all with minimal investment requirements. Besides, after finishing the project, the power plant staff has at their disposal a simulator capable of analyzing future modifications in the operation or the geometry of their boiler.
The complexity (and accuracy) of the model developed encouraged us to present it to the 10th European Conference on Industrial Furnaces and Boilers, where it was accepted for one of the oral sessions.