MgO对赤铁矿粉矿烧结产物低温还原过程的影响

Effect of MgO on low temperature reduction process of hematite fines sinter

铁矿粉烧结中添加MgO有助于稳定磁铁矿和抑制二次赤铁矿的形成,可以改善烧结矿低温还原粉化性能,但其对烧结矿低温还原过程的影响尚不是十分明确。通过热重法测定不同MgO含量的烧结产物在550℃还原过程中质量的变化,定量地了解MgO对烧结产物低温还原性的影响。同时结合XRD和光学显微镜跟踪试样在还原前后矿物组成、结构及裂纹的变化,揭示了MgO改善烧结矿低温还原粉化的机理。结果表明,MgO对烧结产物低温还原过程的影响与Al_2O_3含量有关,不含Al_2O_3时,MgO抑制烧结产物的低温还原,添加Al_2O_3后,MgO对烧结产物低温还原的抑制作用减弱。另外,烧结产物还原过程中裂纹的形成与烧结产物的矿物组成及结构有关,适当的孔隙有利于减少裂纹的形成,这很好地解释了实际铁矿石烧结生产中添加少量的MgO可以改善烧结矿的低温还原粉化性。

The addition of MgO in the sintering of iron ore fines can help to stabilize the magnetite and inhibit the formation of secondary hematite, which can improve the pulverization performance of sintered ore at low temperature, hut its influence on the low temperature reduction process of sinter is not very clear. The mass changes of sintered products with different MgO contents during reduction process at 550 ℃ were measured by thermogravimetric method to understand the effect of MgO content on low temperature reducibility of sinter quantitatively, simultaneously the X-ray diffraction （XRD） and optical microscopy were used to follow the changes of mineral phase, microstructures and cracks in samples for revealing the mechanism of improvement of the low temperature reduction degradation by adding MgO. The results show that the effect of MgO on low temperature reducibility of sin- tered products is related to Al2O3 content. When sample does not contain Al2 O3, MgO inhibits the low temperature reduction of the sintered product. After adding Al2O3, the inhibitory effect of MgO on the low temperature reduction of the sintered product is weakened. The formation of cracks in sintered products during low temperature reduction process is influenced by the reduction ratio of sintered products, mineral phase and microstructures of sintered products, proper porosity is beneficial to reduce the formation of cracks. Then the low temperature reduction degradation of sintered products can he improved by adding a small amount of MgO.