高温快速加热煅烧石灰的活性及其晶粒度研究

Reactivity and Grain Size of Lime Calcined Rapidly at High temperature

在转炉炼钢中用石灰石部分或者全部替代活性石灰可实现冶金过程的低碳和节能。本文研究了石灰石在远高于活性石灰最佳煅烧温度的条件下,被闪速升温快速煅烧后得到的石灰的活性度及Ca O晶粒度变化规律。用盐酸滴定法测定石灰的活性度,在电镜下分析Ca O晶粒度。实验结果表明：当煅烧温度在1200～1300℃时,石灰的活性度随着煅烧时间的延长逐渐增加;当煅烧温度超过1300℃后,随煅烧时间的延长石灰的活性度达到某一峰值后开始下降;煅烧温度越高,石灰活性度峰值出现的越早。电镜检测结果表明随着煅烧温度的升高和煅烧时间的延长,Ca O晶粒不断长大而使其活性度降低。煅烧温度越高,初生Ca O晶粒越细,融合长大的推动力越大。当煅烧温度在1250～1350℃时,合适的煅烧时间为10～15 min;当煅烧温度超过1400℃后,合适的煅烧时间为8～10 min。

In low-carbon energy-efficient basic oxygen furnace （BOF） steelmaking processes, limestone partly or completely replaces the active lime. The reactivity of lime and the variation of CaO grain size were investigated. The lime was obtained by calcining the limestone rapidly at the temperature which is much higher than the best calcining temperature of active lime. The lime reactivity was tested by the titration of hydrochloric acid. Then the grain size of lime was analyzed under the electron microscopy. The results revealed that when the calcination temperature is between 1200℃ and 1300℃, the reactivity of lime gradually increases with prolonged time of calcination. When the temperature exceeded 1300℃, the reactivity decreased after an appearance of maximum. The higher temperature is the earlier the peak of reactivity appears. The electron microscopy testing result shows that at a too high calcination temperature, the continual grows of the grains of CaO which leads to the decreasing of lime activity as the extension of calcination temperature and calcination time. The higher calcination temperature and the finer primary grain of CaO have a greater integration grew impetus. To obtain active lime calcined at ultra-high temperature by flash heating, the calcination condition should be at 1250-1350℃ for 10-15 min or at the temperature of 1400℃ for 8-10 min.