烧结矿气-固还原过程的矿物组成和显微结构变化

Change of Mineral Composition and Microstructure in Sinter During the Gas-Solid Reduction

利用热重分析方法研究了烧结矿与CO气体的气-固还原反应特征,重点考察了反应的不同阶段烧结矿矿物组成和显微结构的变化以及还原过程烧结矿孔隙率的变化。研究发现:由于烧结矿内矿物组成的改变,随着还原度的增加,烧结矿还原速率逐渐减缓。还原前期主要发生赤铁矿→磁铁矿和铁酸钙→磁铁矿的转变,并且赤铁矿的还原速率要高于铁酸钙。当还原度达到70%时,烧结矿内的赤铁矿、铁酸钙和磁铁矿全部被还原为浮士体和金属铁;根据还原过程烧结矿内部结构和孔隙率的变化,发现还原过程中试样的孔隙率由原来的12.43%增加至53.44%,其中大部分的增加量集中在反应的前期。另外,发现存在微气孔的区域更有利于烧结矿的还原。

Characteristics of the gas-solid reduction reaction between sinter and CO gas were investigated with thermal-gravity analyzer.The study mainly focused on the mineral composition,microstructure and porosity during various stages of the reaction.It is found that the reduction rate decreases with higher reduction degree due to the mineral composition changes during the reduction.In the early stage of reduction,the reaction of hematite→magnetite,calcium ferrite→magnetite occurs,and the reduction rate of hematite is higher than that of calcium ferrite.At the reduction degree of 70%,all the hematite,calcium ferrite and magnetite were reduced to wustite.According to the analysis of microstructure and porosity,the porosity of the sample increases from 12.43% to 53.44% after reduction,and most of the increment happens in the early stage of the reduction.It was also found that the reduction is promoted in the area of fine porosity.