PURPOSE: To reduce the amt. of NOX in waste gases of sintering of sintering raw materials obtained by classifying calcareous raw materials to two, mixing coarse grains with the raw materials at the inlet of a mixer and granulating the mixture then adding fine grains in the suitable position behind the mixer and mixing and granulating these.

CONSTITUTION: Calcareous raw materials such as limestone, quicklime, and slaked lime of about ≤5mm which are usually used are classified to ≥1mm and ≤1mm. All of the ≥1mm grains or those added with a part of ≤1mm are added to raw materials such as ore at the inlet of a mixer, by which they are mixed and granulated. The remaining ≤1mm calcareous raw materials are added to the granulating raw materials in the position behind the mixer where 10W50% residence time of the entire mixing and granulating time of the compounded raw materials is obtained, and these are again mixed and granulated. Then, the granules of the sintering raw materials of high dropping strength and a high effect of reducing NOX are obtained.