Experimental Study And Chemical Kinetics Modeling Of Advanced Natrual Gas Reburning Nitrogen Oxides Reduction Mechanism

NOx (Nitrogen Oxides), which is one of major air pollutants emitted by coal combustion, is becoming an increasing threat to environment, weather and human health. Besides, with the increasing demand of environment protection, it's necessary to develop effective NOx control technologies.Advanced reburning is a technical improvement from the base reburning. It not only possesses the advantage of low cost and high efficiency like that of base reburning, but is able to reach more than 85% NOx reduction as well. So, compared with other De-NOx technologies, advanced reburning has more predominant technical superiorities.This paper summarized the research work and conclusions done by others on reburning and advanced reburning, based on which, NOx reduction by advanced reburning are studied deeply through experimental research and chemical kinetics modeling.The paper firstly presents the experimental research of advanced natural gas reburning which carried on a 20 kW multi-function low-NOx test rig. The factors we concern in this experiment are primary fuel characteristics, the temperature of reburn zone (T2), the stoichiometric ratio of reburn zone (SR2), nitrogen stoichiometric ratio (NSR=NH3/NOin) and promoter. The volatile content of primary fuel affects NOx reduction greatly, with advanced reburning, Shenmu bituminous coal's NOx reduction is greater than Lu'an sub-bituminous coal's, anthracite's is the lowest. The results of advanced reburning reveal that the effect of NOx reduction is sensitive to T2, the NOx reduction could only be improved under certain temperature range. Ammonia injection is most beneficial generally when following a reburning zone which is slightly rich (SR2=0.95), but is not very effective when SR2=0.90 and SR2=0.99. At one advanced reburning condition (T2=1250℃, SR2=0.95, NSR=1.5, with promoter) over 90% NOx reduction was obtained.Then, the paper explicates the build of the chemical kinetic modeling for nitric oxide reduction by natural gas advanced reburning which will be used for late reburning mechanism analysis. The model includes the base assumption, control equation, model of chemical reaction mechanism, model of chemical kinetics, method of chemical kinetics analysis and initial parameters. The validity of the model is also validated by experimental data.Finally, the paper employs sensitivity analysis on the reburn zone and advanced reburn zone, on the basis of the model built in this paper. The results show that NO reduction is sensitive to some elementary reactions. The impacts of important elementary reactions and important reactants on NO reduction are studied by rate of production analysis, the NO reduction processes are described by the normalized rate of production. NO reduction paths of the two reductive regions are given, and get the conclusion that the oriented reactions of reburning and advanced reburning are different, the reburning are hydrocarbon reduction reaction-oriented, and the advanced reburning processes are amidogen-oriented.