The effects of heterogeneous reactions on the reduction of NO in petroleum-coke-fired fluidized beds

摘要

Because of high heating value, low volatile, high nitrogen content and high sulfur content, some kinds of petroleum coke are only suitable for use as fuel, especially combusted in fluidized beds. Based on experiments in a 1t/h fluidized bed, we found that lots of NO and N_2O were emitted, and they reached to 780ppm and 150ppm respectively. By analyzing the contributions of char-N and volatile-N to the formation of NO and N_2O, we also found it was more important to control the combustion of char to reduce the emission of NO and N_2O. This paper tried to find a denitrification agent that could work as desulfuration agent in fluidized beds. We chose Fe as the denitrification agent. The influence of iron on the reduction of NO was studied on. The effects of petroleum-coke char, CO and limestone on the reaction of iron and NO were investigated in a bench scale fluidized bed. Quantitative Fe and petroleum coke char were added into a quartz sand bed respectively, the conversions of NO between these conditions were compared with. The results showed that the ability of Fe to reduce NO was much stronger than the char, and the conversion of NO almost reached to 100%. After minutes that depended on the amount of Fe, Fe was oxidized to oxide of Fe, and the conversion of NO decreased. Petroleum coke char could deoxidize the oxide of Fe. Fe that mixed with petroleum coke char could apparently increase the reaction time of Fe and NO. CO was also a reductive agent of the oxide of Fe, but the effect was not strong as char. Limestone little increased the conversion of NO. From the experiments, we suggested that iron or its oxides would be a possible denitrification agent to reduce NO in fluidized beds in situ.