Investigation Of NO_x Hazard Control From Sintering Flue Gas Based On Sintering Sensible Heat Recovery Process

NOXis one of the main atmospheric pollutants, which is harmful to human healthand ecological environment. Coal is a necessary raw material of the sintering process,and NOXfrom coal combustion is one of the main pollutants in iron and steel industry.With the implementation of new acts or regulations, NOXemission standard is morestringent. For example,―Discharge standard of air pollutants for iron and steel industry‖regulates that NOXemission from the sintering process must be below300mg/Nm3since2013.As the selective catalytic reduction (SCR) technology for sintering flue gas has theshortcomings of high investment cost and catalyst deactivation, a new NOXremovalmethod was proposed in this paper according to the characteristic of the sintering fluegas. The sintered ore was performed as catalyst to remove NOXin the annular coolingmachine, which realized the first level of denitration. At the same time, the temperatureof flue gas after desulfurization was heated to the SCR temperature window by the hotsintered ore, and the second level of denitration was realized.Experimental studies were done about SCR of NOXby ammonia with threedifferent sintered ore catalysts. Effects of reaction temperature, molar ratio of NH3/NO,space velocity, the particle size, O2concentration, NO concentration, H2O and SO2onthe sintering flue gas NH3-SCR denitration were studied. The reaction mechanism ofNH3and NOXover sintered ore catalysts was obtained. The experimental resultsindicated that the temperature windows of sintered ore catalysts were in the range of350-450°C. With the increase of the molar ratio of NH3/NO, the denitration efficiencytends to increase. However, with the increase of space velocity and the particle size, thedenitration efficiency tends to decrease. Oxygen played an important role in the SCR,but high oxygen content had a negative effect on NO reduction. H2O had a positiveeffect on the denitration process in the absence of SO2, while SO2inhibited the catalyticactivity of the sintered ore. In the presence of H2O and SO2, the catalytic activity ofsintered ore was suppressed obviously. On the condition that the reaction temperaturewas450°C, the molar ratio of NH3/NO was0.5, the space velocity was3000h-1, theparticle size in range of0.2~1.0mm and the O2concentration was15%, the denitration efficiency of sintered ore catalysts were40.33%、35.22%and27%respectively, whichmeans that the NO concentrations in flue gas have reached the limit of nationalpollutants emission standard of China.On the basis of energy calculation, it was found that the temperature of flue gascould be heated to380°C, which reached to the temperature window of SCR.