高温快速煅烧石灰的物化性质及微观结构的研究

Study on the physico-chemical properties and microstructure of lime rapidly calcined at high temperature

转炉炼钢用石灰石代替活性石灰造渣是钢铁工业低碳和节能减排的重要举措。研究了粒径为12.5~15 mm的石灰石在1 450℃下快速煅烧5~15 min时得到的石灰的物理化学性质、活性度及其与微观结构变化之间的关系。结果表明:石灰石在1 450℃下煅烧5~10 min后,CO_2逸出留下的微气孔十分发达;继续延长煅烧时间CaO再结晶长大使微气孔逐渐消失,石灰结构致密化。反映在物化性质上,随着煅烧时间延长,石灰的气孔率迅速增加,10 min时达到最大值,之后迅速下降;体积密度的变化规律刚好相反;比表面积则随煅烧时间延长而下降。石灰的活性度在煅烧10 min时达到最大值。在高温快速煅烧条件下,CaCO_3分解由表及里,表层的CaO晶粒已经开始再结晶长大而致密化,颗粒内部CaCO_3仍在分解留下大量微气孔。

Active lime was replaced by limestone in converter steelmaking processes,which was a vital measure of low-carbon,energy-saving and emission reduction for iron and steel industry. The relationships between activity,physico-chemical properties of lime and changes of microstructure were investigated respectively. The limestone whose particle size was between 12. 5- 15 mm was calcined fast at 1 450 ℃for 5 min to 15 min. The results showed that CO2 escaped,leaving highly developed micropore after calcining at 1 450 ℃ for 5 min to 10 min. With the extension of calcining time,CaO recrystallized and grew up,resulting disappearance of micropore and densification for structure of lime. Reflecting on the physic-chemical properties,with the extension of calcining time,the porosity of lime quickly increased at first and then decreased,which reached the maximum when calcined for 10 min. However,the variation of bulk density was opposite. The specific surface area of lime decreased with the extension of calcining time.The activity of lime reached the maximum when calcined for 10 min. In the condition of high temperature and fast calcination,CaCO3 decomposition was from the outside to the inside. CaO grain on the surface of lime had recrystallized,grown up and become dense,but CaCO3 was decomposed inside of lime,leaving a lot of micro-pores.