Structure model of granules,boundary value of nucleus and powder,and the relationship between granulation efficiency and boundary value were investigated.Granules of sintering mixtures are composed of adhesive powder and nucleus.In the mixtures,particles larger than 1.00 mm act as nucleus and particles smaller than 0.25 mm act as adhesive powder.Particles with size between 0.25-1.00 mm can be adhesive powder as well as nucleus depending on the granulation conditions.When the boundary value is close to 0.25 mm,the granulation efficiency is lower than 50%.When the boundary value is close to 1.00 mm,the granulation efficiency is above 90%.The boundary value is influenced by the iron ore type,granulation moisture,fineness of raw materials and burnt-lime activity.Good adhesive capability,suitable moisture content,appropriate particle size distribution and high burnt-lime activity make the boundary value move towards 1.00 mm and improve the granulation efficiency.
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