Fundamental Study on Preparing High-Quality Raw Materials of Purified Steel Production by New Process of High Grade Iron Concentrate Direct Reduction-Smelting Separation
摘要：Pure iron with high-quality and low-cost is the superior iron-bearing material for purified steel production. The pure iron prepared by the innovative process of low temperature selective reduction-pollution-control smelting, could reach a grade of Fe grade higher than 99.90 % and total residual elements content less than 0.05 %. Using high-quality pure iron as raw materials of purified steel smelting could effectively solve such problems as uncontrollable residual element content, high carbon emission and steel product structure optimization on contrast to that of hot metal and scrap. In this study, an innovative process of high pure iron preparing by high-grade iron concentrate direct reduction-smelting separation has been put forth and studied by laboratory experiments and pilot test. Firstly, common magnetite with TFe 65 %, large particle size and good grindability was treated by fine grinding and dressing to produce high-grade iron concentrate with TFe 71.50 % ～ 72.00 % and SiO2 content 0.15 % ～ 0.20 %. Next, the high-grade iron concentrate was reduced at 1000～1100 ℃ for 5～8 h by using coal-based direct reduction technology, with the products of direct reduction iron with metallization ratio higher than 95 %. Finally, the direct reduction iron was further processed by smelting separation technology under the conditions including 1625 ℃, 45 min duration and CaO flux adding ratio 9.3 %, contributing the high pure iron with Fe purity up to 99.947 % and C, Si, Mn and P contents as low as 8 ppm, 6 ppm, 14 ppm and 15 ppm, respectively, which could be used as excellent base burden for purified steel production. The corresponding pilot test with the scale of 0.01 Mt/a high pure iron has been finished. Generally speaking, the above new process owes the remarkable advantages such as high iron recovery, low economic cost and low carbon emission.