Extraction of Iron from Refractory Titanomagnetite by Reduction Roasting and Magnetic Separation

Abstract

The abundant refractory titanomagnetite (TTM) provides a cheap alternative source of iron, but this ore contains impurities and is difficult to process to make suitable concentrates for the blast furnace. In this study, reduction roasting of a primary TTM concentrate followed by magnetic separation was investigated to understand the effects of reduction time, coal dosage, and CaF 2 addition on the reduction behavior of TTM and growth mechanism of iron particles. The phase composition of reduced samples was characterized by X-ray diffraction. The size distribution of iron particles was quantitatively examined using image analysis. Results showed that CaF 2 can help improve the reduction degree and particle size of metallic iron. The metallization degree increased from 85.5% to 89.5% when the CaF 2 dosage increased from 0% to 4%, while a minor increase was observed when the CaF 2 dosage exceeded 4%. Accordingly, the TTM samples were treated by reduction roasting with 4% CaF 2 and 25% coal at 1 200°C for 60 min followed by magnetic separation. A magnetic concentrate with an iron content of 91.1% and a recovery of 92.9% was achieved. In addition, the relationship between the size distributions of iron particles and grinding fineness was also studied. The size distribution using data from the diameter of iron particles was found to be close to the actual grinding fineness.

Effect of Initial Temperature on Iron Nugget Formation in Fluxless Processing of Titanomagnetite Under Isothermal – Temperature Gradient Profiles

“…A similar experiment was carried out by Geng et al [13] and found that the phases in pellets reduced by embedding in the coal were metallic iron, ilmenite and pseudobrookite (FeTi 2 O 5 ). Recently, Zhao et al [21,23] reported that the phases in the reduced mixture consisting of ISC and 25% coal at 1200-1300°C were metallic iron, ilmenite, and anosovite ((Fe,Mg)Ti 2 O 5 ). From the experiments mentioned above, the iron nuggets were not formed, the metallic iron was still attached to other oxides.…”

“…[17,21] The addition of sodium sulfate, sodium carbonate and calcium uorite as additives was also investigated to promote the migration, accumulation, and growth of iron into larger particles. [10,13,16,18,23] The nugget formation with a treatment time of 440 min and temperatures up to 1350°C was observed by Hu et al [8] , but in experiments using a laboratory scale rotary hearth furnace at a temperature of 900 -1350°C which was divided into three zones, no nuggets formation was reported [12] .…”

“…[6] Alternatively, many studies have focused on direct reduction in the solid state of TTM by carbonaceous materials wherein iron can be separated from other oxides using magnetic separators. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Coal as reducing agent had shown better performance than coke, graphite or biochar. [22] The addition of coal can be done simultaneously through mixing with TTM or also by immersing pellets or briquettes into the coal bed or coal embedding.…”

Effect of temperature patterns on iron nugget formation in fluxless processing of titanomagnetite

“…Alternatively, many studies have focused on direct reduction in the solid-state of TTM by carbonaceous materials wherein iron can be separated from other oxides using magnetic separators 7 – 23 . Coal as a reducing agent had shown better performance than coke, graphite, or biochar 21 .…”

Reduction of New Zealand Titanomagnetite Ironsand pellets in H2 Gas at High Temperatures

“…More than 1.2 million tonnes of ironsand are mined annually in NZ [7]. Secondly, the ironsand is also regarded as a cheap source of iron units for steel making [8].…”