Gasification Behavior of Phosphorus during Pre-reduction Sintering of Medium-high Phosphorus Iron Ore

• Published in: ISIJ International 2021/05/15, Vol.61(5), pp.1459-1468
• Main Authors: Chen, Yanbiao, Zuo, Haibin
• Format: Article
• Language: English
• Subjects: carbothermic reduction; dephosphorization agent; phosphorus gasification; pre-reduction sintering; reduction time
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.ISIJINT-2020-564

The effects of dephosphorization agents (SiO2, Na2CO3 and Al2O3) and reduction time on phosphorus gasification during pre-reduction sintering gasification dephosphorization were studied. The results indicate that the dephosphorization rate of apatite by carbothermal reduction is 23%, the dephosphorization rate of adding SiO2 and Al2O3 is 25%, and the optimal dephosphorization rate is 36% by adding SiO2 and Na2CO3. The dephosphorization rate increased from 13% to 31% with the reduction time increased from 20 min to 60 min. Thermodynamic analysis shows that the promotion effect of Na2CO3 on apatite reduction is stronger than that of Al2O3, and the thermodynamic conditions of apatite reduction are optimized to the greatest extent by adding SiO2 and Na2CO3, with the starting temperature of carbothermal reduction of apatite decreased from 1464°C to 746°C. P and C have the same variation and change trend, and the migration of phosphorus ito metallic iron is related to the carburizing reaction. The good heat storage of the sinter layer in pre-reduction sintering increases the time for maintaining the apatite reaction temperature and promotes the occurrence of dephosphorization reaction, however part of the phosphorus gas is absorbed by liquid metallic iron to form stable iron phosphorus compounds,which leads to the decrease of dephosphorization rate. Besides addition of dephosphorization agent, restricting migration of phosphorus into iron phase is the key point to increase gasification dephosphorization efficiency in sintering process.