Per: andrielly moutinho knupp (Vale sA), Leandro Resinentti Zanon (vale), Rossano Augusto Nunes Pilon (VALE), Ana Paula Pacheco Buzatti (VALE), Renata Favalli (FCT), Ricardo de Paula Costa (FCT), Diego Biaseto Bernhard (FCT)
Abstract:
The NOx (nitrogen oxides) emissions of anthropogenic origin are mainly the result of burning of fossil fuels at high temperatures. In pelletizing furnaces, mineral coals are added to the pellets and natural gas is fired in the combustion chambers, with both processes contributing to nitrogen oxides emissions. Vale has a target to reduce 10% of all NOx emissions by 2030. Given this scenario and aiming to reduce NOx emissions at the Tubarão Unit – Vitoria, Espirito Santo/Brazil, a case study is proposed for the development of a low NOx burner for pelletizing furnaces. To better understand NOx formation in pellet furnaces, as well as what can be done to reduce NOx emissions in existing plants, a series of CFD (Computation Fluid Dynamics) modelling scenarios are studied. Besides the base case, four different scenarios were evaluated for a 4,9 MW burner firing 3MW of natural gas, considering water injection considering different water flow rates droplet size and injection angle. For the CFD modelling, the geometric void model of a whole combustion was considered. Regarding NOx modelling, only thermal NOx generation was considered as this is the main mechanism of NOx formation in pelletizing furnaces. With the modelled scenarios, no significant changes in flame shape, as per iso-surfaces of carbon monoxide (CO), were observed due to water addition. Up to 50°C reduction in peak temperatures in the flame core and a reduction in the range of 30% to 50% in NOx emission were observed.