| Controlling the emission of nitrogen oxide (NOx) has become apriority due to the implement of the new National Emission Regulation.Circulating fluidized bed (CFB) boilers are known as the most practicalclean combustion technology owing to its high efficiency and low pollution.However, in order to meet the new requirement of100mg/m3, it is necessaryto apply NOx abatement technologies to CFB boilers, among whichselective non-catalytic reduction (SNCR) technology is preferred as its lowcost and considerable removal efficiency.In this work, a bench-scale testing system was used to simulate the flueenvironment of CFB, besides, ammonia and/or additives injected into thesimulated CFB flue gas at the reactor exit. Some key parameters in SNCRprocess, such as temperature, normalized stoichiometric ratio (NSR),residence time, and additives, were investigated to achieve the optimumreaction conditions and the effects of additives. Optimum reactionconditions were obtained as below, temperature of920°C, residence time of0.6s and a NSR of1.5. H2, as an additive, made a shift of170°C towardslower temperature, while CH4or CO made a shift of80°C. In addition, thereaction under the presence of ash and the feasibility of the synthesis gasdenitrification were explored.Meanwhile, the detailed mechanism, which involved the reactions ofadditives, was selected to simulate the SNCR process and the SNCR processwith single or compound additives. Combined with an experimental data,these chemical reactions were in-depth analyzed. Finally, the detailed mechanism was simplified into a called33-99simplified mechanism, including33ingredients and99steps. Simulationresults of simplified mechanism were compared with the results of detailedmechanism and experiments. The comparison show that the33-99simplified mechanism can replace the detailed mechanism to predictcharacteristics of selective non-catalytic reduction reaction of flue gas ofcirculating fluidized bed. |
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