SiO_2基酸化剂高温消解转炉钢渣中游离CaO的研究

Research on Stabilization of Free CaO in Basic Oxygen Furnace Slag with SiO_2 Bearing Acidifier at High Temperature

转炉钢渣中游离CaO的水化膨胀是导致转炉钢渣体积安定性不良的重要原因。通过高温配加SiO_2基酸化剂,改变w(SiO_2)/w(CaO)对转炉钢渣进行稳钙改质处理。利用化学检测分析、X射线衍射和场发射扫描电子显微镜对SiO_2基酸化剂高温消解转炉钢渣中游离CaO的效果和特征进行研究。结果表明,改质后的转炉钢渣的w(SiO_2)/w(CaO)在0.37以上,就能满足钢渣中f-CaO低于3%的水泥和混凝土行业使用标准,且消解率达到60%以上,而当w(SiO_2)/w(CaO)为0.67时,f-CaO低于1%,且消解率达到90%以上;改质前后转炉钢渣的矿相组成有明显差异,改质后转炉钢渣以硅酸二钙、镁黄长石、镁铁尖晶石、磁铁矿和铁铝酸钙相为主,并且镁黄长石相随着w(SiO_2)/w(CaO)的增大而增多;转炉钢渣酸化稳钙前f-CaO被紧密包裹在矿相基体中,高温酸化改质后,团簇状聚集的f-CaO颗粒会嵌在硅酸盐相间,无明显包裹现象,尺寸为0.5~2μm。

The hydration expansion of free CaO(f-CaO)is the key reason for the volume instability of basic oxygen furnace(BOF)slag.BOF slag was modified at high temperature with the addition of SiO 2 bearing acidifier by changing w(SiO 2)/w(CaO).The stabilization effect and characteristics of f-CaO in BOF slag was studied through the methods of chemical determination analysis,X-ray diffraction and field emission scanning electron microscope.The results showed that when w(SiO 2)/w(CaO)was more than 0.37,the f-CaO content in modified BOF slag was lower than 3%,which met the stated standard of steel slag powder used for cement and concrete in China,and the elimination rate could exceed 60%.When w(SiO 2)/w(CaO)was 0.67,f-CaO content was lower than 1%,and the elimination rate could reach above 90%.Compared with the initial composition,the mineralogical composition of BOF slag after modification was obviously different,which mainly consisted of dicalcium silicate,akermanite,magnesium iron spinel,magnetite and iron aluminum calcium phase,and the content of akermanite phase increased with the increase of w(SiO 2)/w(CaO).Before modification,f-CaO was surrounded tightly by other mineralogical phases,while after modification f-CaO particles were not obviously surrounded but clustered together with silicate phases nearby,and the size of these f-CaO particles was from 0.5μm to 2μm.