Effect of metal oxide on the emission of N₂O and NO in fluidized bed temperature range using pyridine as a nitrogenous model fuel

Pyridine has been chosen as the nitrogenous model fuel to research the effect of metal oxide (CaO, MgO and Fe₂O₃) on the emission of nitrogen oxides in the range of fluidized bed combustion temperature. The experiment was presented in a fixed bed reactor with metal oxide layer, and FT-IR gas analyzer was used to monitor the emission of N₂O and NO. When there is no metal oxide loaded, results show that the maximum peak of N₂O is at 725°C. Under the rich oxygen condition, NO increases monotonically with temperature increasing, however, under the lean oxygen condition there is a maximum peak of NO at 675°C, NO decreases to a minimum value at 725°C, and then increases slowly. With the addition of metal oxide, the loaded experimental results show that the addition will not change the general trend of nitrogen oxides, but it affects the emission in a certain extent and the effect has relation to temperature, oxygen atmosphere and metal oxide added. Under the lean oxygen condition, both CaO and Fe₂O ₃ inhibit the formation of N₂O and NO in all temperature range; the effect of Fe₂O₃ on NO is negligible above 900°C; MgO inhibits N₂O at temperature higher than 725°C, and inhibits NO only from 625°C to 700°C. Under the rich oxygen condition, CaO and MgO decrease the N₂O emission efficiently, but Fe ₂O₃ can only act at the temperature higher than 700°C. For the NO emission, CaO and MgO inhibit NO just above 775°C, however, Fe₂O₃ promotes NO greatly especially below 700°C, and it even promotes NO2 to 122.65ppm at 625°C. The results and discussion are helpful to demonstrate the effect of metal elements on the emission of nitrogen oxides in fluidized bed combustion.