Migration behavior of solid fuel particles during granulation process and its influence on combustion property

Iron ore sintering process is the main CO₂ emission source throughout the integrate steelworks, which primarily comes from the combustion of solid fuels. Improving the combustion efficiency and reducing the solid fuel consumption are important ways to reduce the CO₂ emission in the sintering process. Around the efficient combustion of fuel, the migration behavior and combustion characteristics of solid fuel in the granulation process were investigated. The results indicated that during the granulation process, fuel particles with size less than 0.5 mm mainly migrated into the granules with grain size of 1–3, 3–5 and 5–8 mm; fuel particles with size of 0.5–1 mm mainly migrated into granules of 1–3 mm; fuel particles with size of 1–3, 3–5 and 5–8 mm mainly entered the granules with the same grain size. With the increase in fuel particles grain size from − 0.5 to  + 8 mm, the combustion efficiency exhibited a firstly-increasing and then decreasing tendency, while the NO_x exhibited a decreasing tendency. Potential reason can be described that finer fuel particles (− 1 mm) easily distributed in the outer layer of the granules, which combusted fiercely due to its larger specific surface area, leading to the development of incomplete combustion and the conversion of fuel nitrogen; the combustion efficiency of larger fuel particles was restricted by the inner diffusion of O₂, which then contributed to the reduction of NO_x under the inadequate combustion atmosphere.