Preparation Of Magnesium Flux Pellets And Its Reduction Behaviors In COREX Process

Abstract:Acidic pellets and lump ores are the chief iron-bearing burden for COREX process which tends to swell, disintegrate and burden cohesion during reduction. This will result in poor work status in shaft furnace. In order to strengthen the COREX prereduction process and reduce energy consumption of COREX, limestone and magnesite were added to mixed concentrates comprising of Brazilian PFCJ hematite, CSN hematite and Peru magnetite to prepare magnesium flux pellets and its reduction behaviors was examined. This is significant to strengthen COREX smelting reduction process.Optimal preparation technology parameters of preparation pellets were as follows:at1.0%dosage of bentonite, balling moisture of about8.48%, balling for12min, preheating at1150℃for12mm, roasting at1250℃for15min. The roasted pellets with basicity (0.8-1.2) and MgO content (0.5%～2.5%) were recommended to produce. Compressive strength of the pellets was more than2500N/per. The iron grade ranged from60.8%to63.0%, and reduction degree was higher than80%. The RSI of pellets was below12.0%. The RDI-3.15mm was under6.2%. All the indicators of the flux pellets meet the production requirement of COREX.Suitable prereduction process parameters:reduction at800℃for3h, ratio of H2to CO was set to1/3. The metallic pellet, with metallization rate at87.8%, reduction degree at80.1%, compressive strength at640N/per and RSI at9.0%was achieved. The elevating reduction temperature and molar ratio of hydrogen is beneficial to improve metallization rate, reduction degree and compressive strength of prereduction pellets.Process parameters for smelting were optimized as follows: reduction temperature at1450℃for15min, graphite dosage is1.56%for metallization rate of91.2%of prereduction pellet. The pigiron with iron grade of98.70%, C0.62%, Si0.04%, Mn0.29%, P0.005%, and S0.002%was obtained and iron recovery was99.72%. As metallization rate of prereduction pellet became higher, iron recovery of pig iron increased slightly, but the dosage of graphite fell dramatically. There are28figures,23tables and97references in this paper.