NO_x and N₂O Emissions During Fluidized Bed Combustion of Leather Wastes

Transformation of hide (animal skins) into leather is a complicated process during which a significant amounts of wastes are generated. Fluidized bed combustion has been extended to burn different wastes that have problems with their disposal showing its technical feasibility. Considering the characteristics of the leather waste, especially the heating value (12.5–21 MJ/kg), it is a fairly good fuel. Moreover, leather waste has a high volatile matter, 65%, similar to other biomasses and an unusual high nitrogen content, 14%. The first objective of this work is to study the fluidized bed combustion of leather wastes presenting experimental results regarding NOx and N₂O emissions. A series of experiments have been carried out in a fluidized bed pilot plant to understand the importance of operating parameters such as furnace temperature, oxygen content in gases, staged combustion and residence time on the NOx and N₂O emission level. Despite having high nitrogen content, low conversion of N-fuel to NOx and N₂O was measured during the combustion of leather waste in BFB. Bed temperature and oxygen content were found as the most important single parameters on N₂O emission and only oxygen content has a significant influence on NOx emission. Leather waste exhibits a great NOx/O₂ trend; NOx decreases as the oxygen concentration decreases and the effect of the combustion temperature on NOx is insignificant. Staged combustion does not give a reduction in NOx.