Experimental Study On Nitrogen Oxide Emissions And Its Factors During Iron Ore Sintering

With the rapid development of China’s iron and steel industry, the environmental problems have become more and more serious. Iron ore sintering production is an important part of the steel industry, the sintering process poses a series of environmental pollution, including NOx pollution. The NOx emissions generated from the sintering production process have accounted for more than half of the total NOx emissions in iron and steel industry,which has attracted the public attention.From the source of NOx emissions in iron ore sinter, this paper studied the factors which affect coke combustion and fuel nitrogen release.The influences of temperature and coke particle during coke conbustion were studied on a horizontal tube furnace. The char-N conversion rate increased with increasing temperature when temperature was below1000℃and decreased with increasing temperature if it was higher than1000℃. When the particle size of coke was between1.0mm and2.0mm, it burn the most intense,which lead to the highest char-N conversion rate compareing to other particle size of coke. The effects of alkali metal on NOx release curve and char-N conversion rate were studied. The results show that alkali metal can decrease the NOx emissions released from coke combustion and the extent of the contact between additives and coke was: K2C03>Na2C03>KCl>NaCl.An experimental study of the effects of ignition process and batching process parameters on NOx emissions during the sintering process was carried out by sinter pot test. The results show that improving the ignition time could increase the concentration of NOx emissions, but the char-N conversion rate remain basically unchanged. Improving the ignition suction could increase the concentration of NOx emissions and char-N conversion rate at the same time. When coke content increased from4.05%to4.35%and4.6%, the concentration of NOx emissions and char-N conversion rate increase followed a positive correlation relationship. Basicity also played an important role on NOx emissions,the increase of basicity directly lead to the increase of the concentration of NOx emissions and char-N conversion rate increase. The moisture content changed between6.0%and7.0%, NOx emission concentrations were positively correlated with moisture content, char-N conversion rate was negatively correlated with moisture content. Return fine affect the NOx emissions with the calcium ferrite it included. The char-N conversion rate decrease directly when return fine content increase. Changing the bed height would affect the sinter regenerative effect,with the increasing height of the bed, NOx emissions concentration decreased while the char-N conversion rate increased.