In order to optimize the added moisture content to match the raw material mix conditions, the necessary moisture content for the iron ore in the raw materials and so on must be determined in advance. Accordingly, the authors conducted a study of the necessary moisture content for each brand of iron ore, in order to stabilize the granularity of the sinter ore raw material and the permeability of the packed bed and maintain these values at a high level regardless of the conditions of sinter mix.
When the particle size distribution was constant, the added moisture volume such that the permeability of the packed bed (made up of quasi-particles) for each type of ore after granulation was the maximum value (=optimal moisture value) tended to be lower than the saturation moisture content for all types of ore. Moreover, when the quantity of coarse-grained particles in the ore increased, the optimal moisture value tended to shift to the low moisture side. The application of the optimal moisture value enables the added moisture content to be reduced as compared to the conventional method, without adversely affecting granularity or the permeability of the packed bed.