Investigation On Technology And Mechanism Of Ignition Of Iron Ore Sintering By Microwave Heat Airflow

Sintering process is one of the energy consumptions throughout the steel industry which accounts for 8.3%of total energy consumption.And the consumption of ignition accounts for 5%-10%in sintering process.At present iron ore sintering ignition both at home and abroad all adopts mixed gas or coke oven gas,etc.with higher calorific value.Such sintering ignition consumes more gas,produces a large amount of emissions,and also pollutes environment.Howerver,microwave heat airflow ignites by heating air which can enhance the oxygen content and get the aim of energy saving with non-polluting.So,it has important economic and environmental significance.This paper calculated by modeling microwave heat airflow ignition and combining with Baosteel's raw materials conditions and the result shows that the minimum ignition temperature is 638.54℃and the minimum ignition energy is 25625.00kJ/m~2 in the 1.5min ignition time.In the condition of ignition temperature of 800℃,the sinter temperature of the surface sinter layer can reach 1252.88℃,which is as much as the sinter temperature by gas igniton.The oxygen content in the ignition airflow is 21.00%by microwave heat airflow ignition.However,the oxygen content is only 8.95%by gas ignition.Effect of oxygen content in the ignition airflow on sintering shows the indexes of sinter increase rapidly as the content of oxygen.TheΦ150×650mm sinter cup by Laboratory microwave heat airflow ignition can get excellent sintering indexes under the conditions of igniting temperature of 760℃,igniting time of 1.5min,heat airflow temperature of 330℃,igniting airflow speed of 0.53m/s.And the sintering indexes are that the speed of vertical sintering is 24.23mm/min, drum strength is 59.50%,the production rate is 76.60%,and the utilization factor of sintering cup is 1.833t/(m~2·h).Extended experiment of microwave heat airflow ignition can get successful under the conditions that output microwave power is 72 kW, ignition temperature is 714℃,ignition time is 1.5min,heat preservation time is 5 min,ignition airflow volume is 930 Nm~3/m~2·h,ignition negative pressure is 1.2 kPa,sintering negative pressure is 4 kPa.The sintering indexes are that the speed of vertical sintering is 19.35 mm/min,and the drum strength is 69.4%.In addition,the ignition energy consumption is 25.56 MJ/m~2.High content of oxygen in microwave heat airflow is in favor of developing hematite.So microwave heat airflow ignition can get sinter with better micro-structure.The number of hematite in sinter is high,the number of magnetite is low and calcium ferrite is widely distributed with full crystal shape in the sinter obtained by microwave heat airflow ignition,whose indexes are better than sinter gained by gas ignition.The microstructure of middle layer and underlayer sinter obtained from microwave heat airflow ignion is similar with the sinter gained by gas ignition.