MgO含量和来源对球团焙烧特性及冶金性能的影响

Effect of magnesium oxide and its occurrence on the roasting and metallurgical performance of magnetite pellets

分别以5种不同的含镁添加剂(高镁磁铁矿、镁橄榄石、白云石、菱镁石和氧化镁粉)制备镁质球团,阐述MgO含量和来源对磁铁矿球团焙烧特性及冶金性能的影响.研究结果表明:不同的含镁添加剂对于生球的落下强度有着一定影响,其中氧化镁粉与高镁磁铁矿均能够提高球团的落下强度.相同的预热焙烧制度下,提高MgO含量会增加球团孔隙率,降低预热和焙烧球团的抗压强度,其中白云石对焙烧球团强度的不利影响最小.增加预热球团的氧化度有利于促进镁质焙烧球团固结,提高其抗压强度.在MgO来源相同的情况下,MgO含量的增加会导致球团孔隙的增减,降低了球团强度,而配加不同种类的含镁添加剂,均能不同程度改善球团的还原膨胀性、低温还原粉化性和还原性,其中配加高镁磁铁矿的球团的还原膨胀性和低温还原粉化性均优于于其他含镁球团.

Increased Al2O3 content in blast furnace slag in China presents adverse effects in blast furnace smelting.In response to this problem and to improve fluidity of blast furnace slag,MgO pellets are added.Blast furnace can be operated smoothly,but on the other hand,higher MgO content is unfavorable to the pelletizing property and pellet roasting performance of raw materials.Five kinds of pellets containing high-magnesium magnetite,forsterite,dolomite,magnesite,and magnesia powder,respectively,were made to investigate the effect of MgO content and its occurrence on induration behavior and metallurgical performance of pellets.Results show that various magnesium-containing fluxes have different influences on the quality of green balls.Both magnesia powder and high-magnesium magnetite can improve the drop numbers of green balls,which is due to their chemical properties and specific surface areas.With fixed firing temperature and time,increasing MgO content leads to lowered compressive strength of the preheated and fired pellets,with the lowest impact from dolomite observed.With the oxidation degree elevation of preheated pellets,compressive strength of roasted pellets improves,which indicates that we can increase the preheating time in actual production to improve the roasting performance of magnesium magnetite pellets.Under the same source of MgO,increasing MgO content will lead to an increase in porosity of pellets,which presents a negative effect on the strength of pellets.For five kinds of fired pellets,increased MgO content improves the reduction swelling index,low temperature degradation indices,and reduction degree.The reduction swelling index and low temperature degradation indices of pellets with high-magnesium magnetite are observed to be better than those of other magnesium-containing pellets.