The Influence of CaO Content in Limestone on Lime Activity
Lime activity is an important indicator for measuring the reactivity of lime, which directly affects its application effects in metallurgy, building materials, and environmental protection. The content of CaO in limestone is one of the key factors determining its activity, and its influence is mainly reflected in the following aspects.
The higher the CaO content in limestone, the lower the impurity content (such as SiO ₂, MgO, etc.). High purity CaO is more likely to form lightly calcined lime with higher porosity during the calcination process, which has a larger specific surface area and smaller grain size, thereby significantly enhancing the activity of lime. Experiments have shown that when the CaO content in limestone exceeds 95%, the activity of the obtained lime can reach over 350 mL (4N HCl titration method).
The CaO content affects the kinetics of the calcination process. The thermal decomposition of high CaO limestone is more uniform, resulting in a loose CaO crystal structure with more defects, and a faster reaction rate with water. However, low CaO limestone is prone to over burning or under burning due to impurity interference, forming dense crystals and significantly reducing activity.
However, CaO content is not the only determining factor. If the calcination temperature is too high (>1200 ℃), even if the CaO content is high, the activity will decrease due to sintering phenomenon. Therefore, in actual production, it is necessary to balance the purity of raw materials and process control to achieve optimal activity. In summary, the CaO content in limestone is positively correlated with lime activity, but it can only be fully reflected under suitable calcination conditions.
