Slag/metal Separation Process of Gas-reduced Oolitic High-phosphorus Iron Ore Fines

Slag/metal separation process of the highly reduced oolitic high-phosphorus iron ore fines was investigated. Samples were prepared using the reduced ore fines （metallization rate： 88%） and powder additives of CaO and Na2CO3. Slag/metal separation behavior tests were conducted using a quenching method and the obtained metal parts were subjected to direct observation as well as microstructure examination with SEM and EDS; iron recovery and phosphorus distribution tests were conducted using a Si-Mo high temperature furnace and the obtained metal parts were examined by ICP-AES analysis and mass measurement. Thermodynamic calculation using coexistence theory of slag structure was also performed. Results show that temperature for slag/metal separation must be higher than 1823 K and a satisfying slag/metal separation of the highly reduced ore fines needs at least 4 min; phosphorus con- tent of hot metal is mainly determined by thermodynamics; temperature of 1823-1873 K and Na2CO3 mixing ratio of about 3 % are adequate for controlling phosphorus content to be less than 0.3 mass% in hot metal; temperature, time and Na2CO3 mixing ratio do not have significant effect on iron recovery, and iron recovery rate could be higher than 80% as long as a good slag/metal separation result is obtained.

Migration behaviors and kinetics of phosphorus during coal-based reduction of high-phosphorus oolitic iron ore

To understand the migration mechanisms of phosphorus(P)during coal-based reduction,a high-phosphorus oolitic iron ore was reduced by coal under various experimental conditions.The migration characteristics and kinetics of P were investigated by a field-emission electron probe microanalyzer(FE-EPMA)and using the basic principle of solid phase mass transfer,respectively.Experimental results showed that the P transferred from the slag to the metallic phase during reduction,and the migration process could be divided into three stages:phosphorus diffusing from the slag to the metallic interface,the formation of Fe P compounds at the slag metal interface and P diffusing from the slag metal interface to the metallic interior.The reduction time and temperature significantly influenced the phosphorus content of the metallic and slag phases.The P content of the metallic phase increased with increasing reduction time and temperature,while that of the slag phase gradually decreased.The P diffusion constant and activation energy were determined and a migration kinetics model of P in coal-based reduction was proposed.P diffusion in the metallic phase was the controlling step of the P migration.