Research on Reaction Mechanism of Vacuum Carbon Thermal Reduction and Dephosphorization in High Phosphate Iron Ore

Abstract

According to the mineral composition characteristics of high-phosphorus iron ore, the reaction mechanism of fluorapatite was investigated using pure substance and gangue under vacuum carbon thermal reduction (VCTR) conditions. The effects of reduction temperature, basicity, and C/O ratio on the metallization ratio, dephosphorization ratio, and phosphorus content of pellets were studied. The reaction process of fluorapatite in high-phosphorus iron ore was investigated. The results showed that when the metallization ratio of pellets reached maximum (95%), the dephosphorization ratio was only 5.6%, thus indicating adverse result. The reduction processes of high-phosphorus iron ore under vacuum and nitrogen environment were, respectively, compared under the optimal condition. It was found that the metallization ratio of pellets in the vacuum condition was higher than that under the nitrogen condition, while the dephosphorization ratio showed an opposite result. This indicated that in the process of vacuum reduction, fluorapatite not only reacted with carbon to form gaseous phosphide, but also with iron to form compounds containing the Fe⁻P bond. Therefore, a new mechanism of reduction of fluorapatite was proposed as follows: 2Ca5(PO4)3F + 12Fe + 9SiO2 + 15C = 9CaSiO3 + 6Fe2P + 15CO + CaF2.

Keywords

• high-phosphorus iron ore
• vacuum carbon thermal reduction
• fluorapatite
• reaction mechanism