Effect Of Cement Raw Meal On SNCR Denitration Process

Nitrogen oxides?NO_x? is one of the main air pollution sources and cement industry NO_x emission is large in China. Selective non-catalytic reduction?SNCR? is a widely applied to denitration technology and the use of utility boiler has matured. However, the application in cement kiln is not good, in which it causes the lower denitration rate and the more consumption of ammonia. It indicates that the use on cement kiln is more complicated than on utility boiler. The presence of high concentration cement raw meal, which includes various high activity oxides, may be affects the SNCR denitration reaction process. Hence the study of the effect of cement raw meal for research to improve de NO_x rate on cement decomposing furnace is important.Studied the effect of cement raw meal and its major oxides Ca O, Si O₂, Al₂O₃, Fe₂O₃ by SNCR denitration process, DRIFTS and multiple catalytic reaction kinetics calculations.At the same time studied the effect of gas component by SNCR denitration process and XRD.The results showed that cement raw meal adsorbed NH₃ and promoted NH₃ to be oxided to NO and H₂ O, which inhibited denitration reaction. The situ diffuse reflectance infrared spectroscopy showed that the main reaction on the surface of cement raw meal was NH₃ oxidated by O₂ to NO and H₂ O. Under different conditions of temperature and NSR,Ca O, Al₂O₃, Fe₂O₃, same as cement raw meal, also inhibited denitration reaction. When NSR=1, Si O₂ promoted the denitration reaction, but when NSR was 1.5, Si O₂ inhibited the denitration reaction.The effect of cement raw meal under different concentrations of O₂, CO₂, SO₂ on SNCR denitration processs were studied. The results showed that when O₂ concentration was 0, the denitration rate was the highest more than 80%. As O₂ concentration increased the dehydrogenated NH₃ would react with O₂ to NO, which affected the denitration reaction. CO₂ also inhibited reaction of O₂ in the surface of cement raw meal, which inhibited production of NO. CO₂ concentration was between 20%-30% in cement decomposing furnace and the denitration rate was higer inhibited when CO₂ concentration was 20%. SO₂ also inhibited the influence of cement raw meal for the denitration reaction, which due to SO₂ reacted with Ca O to Ca SO4 with cement raw meal. SO₂ reacted with NH₃ to?NH4?2SO3·H₂O and?NH4?2SO4, which could caused arthrodern and obstruction,so the less the SO₂ content, the better.Made multiple catalytic reaction kinetics calculations were used for cement raw meals analysis Ca O, Si O₂, Al₂O₃, Fe₂O₃, the fitting denitration reaction of NO concentration was obtained and the correlation was better fitting. Therefore, form the analysis of kinetic parameters, the decreasions of surface area and apparent density and the increasion of the average particle size of cement raw material could decrease the NO reduction and improve the denitration rate in industrial application. From the fitting surface reaction rate of NO on Cement raw meal and Ca O, Si O₂, Al₂O₃, Fe₂O₃, the increasions of alumina modulus at 750?-970? and lime saturation factor at 970?-1100?, could increase the SNCR denitration rate of cement raw meal.