Study on a Recycling Solution of Basic Oxygen Furnace Slag in Pelletizing Process

Abstract

Basic oxygen furnace slag (BOF slag) contains high amount of useful oxides such as CaO, MgO, SiO2, etc., therefore, a solution of the slag recycling would be used as a flux in pelletizing process. To understand role of slag in the pellet, this research examines the mechanical, chemical and microstructure properties of the pellets containing various amount of the slag. In the experimental process, the green pellets were made from a mixture of bentonite, iron ore and the slag. The green pellets were sintered in the resistance heating furnace maintaining temperature at 1200 °C for 120 minutes. Then the fired pellet was tested strength and observed microstructure with variation of the slag amount in the pellets. The result shown that cold compression strength of the pellets containing from 1.06 to 18.45 mass% slag was higher values than 200 kg/p, hence, the pellet was able to charge the pellets into the blast furnace. The highest strength was 342 kg/p with 5.08 mass% slag in the pellet. Besides, optical observed microstructure of the pellet indicated the phases of magnetite, hematite and silicate. In addition, the obtained results shown that there was a deterioration of porosity with increasing the slag amount. Accordingly, the porosity got a slight decrease when the slag amount increased from 1.06 to 5.08 mass% in the pellet. Once the amount of the slag was higher than 5.08 mass%, the porosity significantly reduced with increasing the slag amount; the porosity decreased from 23 to 12 %.