The range of activity for calcining lime in a lime vertical kiln
When calcining lime in a vertical kiln, activity is a key indicator for measuring its quality. Activity generally refers to the rate and exothermic capacity of lime reacting with water, usually expressed in milliliters (mL) of 40 ℃ water consumed within 4 minutes.
In the calcination process of lime vertical kiln, the activity is affected by various factors, including calcination temperature, time, raw material quality, etc. Generally speaking, the activity level of high activity lime should be ≥ 300mL, while the activity level of ordinary lime is between 200-280mL.
The calcination temperature is a key factor affecting the activity of lime. When the calcination temperature is between 900-1100 ℃, limestone decomposes fully, and the resulting CaO crystal structure is loose, with a large specific surface area and high activity. If the temperature is too low, the decomposition of limestone will not be complete, and the residual CaCO3 will reduce the activity; When the temperature is too high, CaO crystals sinter and become denser, resulting in a decrease in specific surface area and activity.
In addition, the quality of raw materials also has a significant impact on the activity level. High purity limestone (CaCO3 ≥ 95%) has low impurities and high activity after calcination; Low grade limestone contains impurities such as SiO ₂ and Al ₂ O3, which can easily form low melting point compounds, leading to CaO sintering and a decrease in activity.
Therefore, in the calcination process of lime vertical kiln, it is necessary to control the calcination temperature and time reasonably, select high-quality raw materials to produce high activity lime.
