Effects of Particle Sizes of Iron Ore and Coal on the Strength and Reduction of High Phosphorus Oolitic Hematite-coal Composite Briquettes

This study presents a process with coal-based direct reduction of high-phosphorus oolitic hematite before magnetic separation for producing direct reduction iron (DRI), where Ca(OH)(2) and Na2CO3 were used as additives in order to inhibit the reduction of fluorapatite and promote the reduction of hematite. The effects of particle sizes of iron ore and coal on the strength and reduction of cold-bonded composite briquettes were investigated. It showed that the decrease of the particle sizes of iron ore and coal increased the strength of composite briquettes. At the temperature of 1 200 degrees C, a sizable increase of recovery and iron content of DRI was observed when the particle size of iron ore decreased from -4 mm to -0.1 mm, however, the phosphorus content of DRI obtained from -0.1 mm iron ore was much higher than that from coarser iron ore. The results of SEM-EDS analyses showed that the reduction of fluorapatite in the iron ore was activated when using -0.1 mm iron ore and the reduced phosphorus melting into metallic iron. Moreover, the particle size of coal has less effect on the direct reduction-magnetic separation than iron ore within the scope of the study.