镁铝对烧结矿中铁酸钙的矿物学特性影响

Influences of MgO and Al2O3 on the mineralogical properties of calcium ferrite in iron ore sinter

铁酸钙是高碱度烧结矿中的主要黏结相矿物,它的含量、结晶形态、化学成分及晶体结构等矿物学特性对烧结矿质量起着关键性作用,而烧结原料中各组分的含量直接影响着铁酸钙的生成。以Fe3O4、SiO2、CaO、MgO、Al2O3的化学纯试剂为原料,在实验室进行微型烧结实验,运用XRD、偏光显微镜、电子探针等手段,定量分析研究了原料组分中MgO、Al2O3对烧结矿中铁酸钙的生成及其矿物学特性的影响。原料中MgO含量的增加对铁酸钙的生成有一定抑制作用,尤其在MgO含量为2.0%~3.0%时,烧结矿中铁酸钙含量明显减少,其晶体形态也从以板柱状和针状为主逐渐过渡为它形不规则状;原料中Al2O3的增加,对烧结矿中铁酸钙的形成具有促进作用,即随着Al2O3的增加铁酸钙含量呈明显增加趋势,且铁酸钙的形态也由以柱状和针状为主向板柱状变化。电子探针成分分析及矿物化学式计算结果表明,铁酸钙是由Fe2O3、CaO、SiO2、Al2O3及MgO组成的复杂结晶体,其化学通式为Ca2.60Mg0.44Si1.07Al0.96Fe8.92O20。原料中MgO、Al2O3含量的变化,对铁酸钙的化学成分中Fe2O3/CaO摩尔分数比影响不大,均接近3∶2。上述研究结果对于深刻理解烧结工艺条件下铁酸钙晶相的晶体化学特征及其对烧结矿质量的影响具有重要指导意义。

Calcium ferrite is the main binder phase mineral in high basicity sintered ore.Its mineralogical characteristics such as content,crystal form,chemical composition and crystal structure play a key role in the quality of the sintered ore.The content directly affects the formation of calcium ferrite.In this paper,we used the chemically pure reagents of Fe3O4,SiO2,CaO,MgO,and Al2O3 as raw materials and carried out micro-sintering experiments in the laboratory.Using XRD,polarizing microscope,electron microprobe and other means we performed quantitative analyses of MgO and Al2O3 in the raw material components to investigate the formation of calcium ferrite in sintered ores and its influence on mineralogical properties.The results showed that the increase of MgO content in the raw material had a certain inhibitory effect on the formation of calcium ferrite,especially when the MgO content was 2.0%to 3.0%.The calcium ferrite content in the sinter was significantly reduced,and its crystal morphology also changed from plate columnar and needle-like shape gradually transitioning to an irregular shape.The increase in Al2O3 in the raw material promoted the formation of calcium ferrite in the sinter as calcium ferrite content increased significantly with increasing Al2O3 and ferric acid contents.The morphology of calcium also changed from columnar and needle-shaped to columnar.Electronic probe composition analysis and mineral chemical formula calculation results show that calcium ferrite is a complex crystal composed of Fe2O3,CaO,SiO2,Al2O3 and MgO,and its chemical formula is Ca2.60Mg0.44Si1.07Al0.96Fe8.92O20.The changes in MgO and Al2O3 contents in the raw materials had little effect on the mole fraction ratio of Fe2O3 to CaO in the chemical composition of calcium ferrite,both were close to 3∶2.The above research results are of great guiding significance for an in-depth understanding of the chemical characteristic of calcium ferrite crystal phase under sintering process conditions and its effect on the quality of sinter.