Lime calcined in a rotary kiln or a new shaft kiln (sleeve kiln) at a temperature of 1050-1150 ° C, which has high volume density, high porosity, high specific surface area and fine grain size. Lime is called active lime, also known as soft burnt lime.

Active lime has a water activity of more than 310ml, a small bulk density of about 1.7-2.0g/cm3, a porosity of more than 40%, a specific surface area of 0.5-1.3cm2/g, a fine grain size, a fast melting rate and a strong reaction capability. . The use of active lime can reduce the consumption of lime, fluorite and converter slag, which is beneficial to improve the desulfurization and dephosphorization effects, reduce the heat loss of the converter and the erosion of the furnace lining. It is also difficult to form dense dicalcium silicate hard on the lime surface. The shell helps to accelerate the slag of lime.