Effects of impurities in lime used for iron ore sintering on its hydration characteristics

The effects of SiO2, Al2O3 and MgO on the hydration of lime were investigated by isothermal calorimetry, and the results were validated by 5 types of lime used in the sintering plant. It is found that the total hydrating heat of lime has positive relationship with CaO content, and decreases with increasing SiO2, Al2O3 and MgO contents. The contents of SiO2, Al2O3 and MgO also have important effect on the hydrating speed of lime. When the mass fraction of SiO2 increases to 1%, the hydrating speed of lime dramatically decreases, and then slowly drops with increasing SiO2 content. A small amount of Al2O3 has no significant effect on the hydrating speed of lime, but when the mass fraction of Al2O3 is more than 2%, the hydrating speed of lime sharply decreases. With the increase of MgO content, the hydrating speed of lime significantly decreases.