Study On Mechanism Of NO_x Reduction In Cement Calciner

At prement,the emission of NO_x for the new dry process cement production line of2000-5000 t/d in China is generally greater than 850 mg/Nm³,resulting the cement industry to become the third largest nitrogen oxides emission source.Currently,the national standard stipulates that the emission of NO_x is not more than 400 mg/Nm³ in China.Therefore,the cement industry is facing a serious problem of NO_x removal.Staged combustion and Selective non-catalytic reduction?SNCR?technology are considered as economical and effective denitration methods,which are widely applied in utility boilers.But the application in cement kiln is less,and the efficiency of NO reduction is low.high concentrations of calcium based materials?especially CaO?and high concentration of CO₂ may be affect the application in cement kiln.Therefore,it possesses important academic significance and engineering application value to study NO_x reduction by CO and NH₃ in high concentration CaO and CO₂ atmosphere.The study of NO_x reduction by CO and NH₃ was carried out in a high temperature fluidized bed reactor,and the exhaust gas was measured and analysed by FTIR gas analyzer of DX-4000 type,Germany maded.The effect of CaO?CO₂ concentration?O₂concentration and temperature for the N₂O production and NO_x reduction by CO and NH₃ was studied to provide a theoretical basis for the application of staged combustion and SNCR technology in cement precalciner.On the one hand,the effect of CaO?COconcentration and temperature for the N₂O production and NO_x reduction by CO was studied under the atmosphere of CO₂?N₂ and NO.The result showed that CaO has positive catalytic effect on the NO reduction by CO,and is beneficial to inhibit the formation of N₂O.The increase of temperature leads to the enhancement of catalytic activity of CaO,and the increase of CO concentration promotes NO_x reduction.The application of staged combustion in cement precalcinercan effectively reduce the emission of NO_x.On the other hand,the effect of CaO?CO₂ concentration?O₂ concentration and temperature for the N₂O production and NO_x reduction by NH₃ was studied under the atmosphere of CO₂?N₂?O₂ and NO.The result showed that CaO has an obvious inhibitory effect on the generation of N₂O and the NO reduction by NH₃.The high CO₂concentration is not conducive to the application of SNCR technology,when the oncentrationexceedes 25%,especially.The optimum temperature of NO_x reduction towards to the low temperature about 50 ^oC.Thus,the application of SNCR technology in calciner should consinde the effect of CaO?CO₂ concentration?O₂ concentration and temperature.