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

摘要

The effects of dephosphorization agents (SiO_(2), Na_(2)CO_(3) and Al_(2)O_(3)) 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 SiO_(2) and Al_(2)O_(3) is 25%, and the optimal dephosphorization rate is 36% by adding SiO_(2) and Na_(2)CO_(3). 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 Na_(2)CO_(3) on apatite reduction is stronger than that of Al_(2)O_(3), and the thermodynamic conditions of apatite reduction are optimized to the greatest extent by adding SiO_(2) and Na_(2)CO_(3), 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.