An experimental study on nitrous oxide (N2O) reduction with circulating ashes of circulating fluidized bed (CFB) boilers was conducted for the development of an effective and economical technology to reduce the N2O emission from CFB boilers. The experiments were conducted with three kinds of circulating ashes, by using a fixed bed reactor with a diameter of 25mm, under various conditions of different operational temperatures, initial N2O concentrations, NH3 additions and O2 concentrations. The effects on N2O reduction were compared that with quartz sand. The experimental results showed that circulating ashes may possess remarkable catalytic effect on N2O reduction and the intensity of the catalytic effect strongly depends on operational parameters such as reaction temperature and O2 concentration. It was also found nitric oxide (NO) was produced during the process of N2O reduction and its concentration also strongly affected by reaction temperature and O2 concentration. The mechanisms of N2O reduction were discussed. The study confirmed the feasibility of injecting NH3 at the cyclone entrance of CFB boiler to form a selective catalytic reduction (SCR) process for N2O emission without using extra catalyst and provided some guidance to choose the operational parameters for N2O reduction with circulating ashes.

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