Comparative Study And Mechanism Of Reduction Methods For Recovering Titanium And Iron From Beach Titanomagnetite By Direct Reduction-magnetic Separation

Beach titanomagnetite(TTM)is an ore with abundant reserves and low mining cost.However,it is difficult to separate Fe and Ti effectively from TTM by traditional mineral processing techniques because the resulting iron concentrate has high TiO2 content,which can cause wasting of Ti resources in TTM.Recently,studies showed that it is feasible to separate Fe and Ti by coal-based direct reduction followed by a magnetic separation technique.However,some problems remain unsolved,such as low TiO2 content in the non-magnetic product.Some researchers found a new method,i.e.,embedding coal-based direct reduction followed by magnetic separation,to recover Ti resources and avoid the effect of coal ash on product metrics.However,there are some problems such as high coal consumption and difficulties in practical application.To achieve satisfying results concerning the recovery of Fe and Ti,a type of Indonesian beach TTM with 58.58%TFe and 12.04%TiO2 was selected in this thesis as sample.The coal-based direct reduction and embedding coal-based direct reduction techniques were compared to elucidate the differences in the recovery of Fe and Ti,and then the effects of factors such as reductant type and additive on the separation and recovery of Fe and Ti were also studied.Results indicate that from the perspective of product metrics and dosage of reductant,coal-based direct reduction was a better way to recover Fe and Ti.TTM samples were treated by reduction roasting with 4%CaCO3 and 12%graphite powder at 1300 ? for 60 min,followed by magnetic separation.Direct reduction iron power(DRIP)featuring 92.58%TFe and 0.87%TiO2 with an iron recovery of 90.72%,and titanium concentrate featuring 45.39%TiO2 with a TiO2 recovery of 80.34%,were obtained.Concentration of CO and CO2 in reaction gas,gas generation rate of reductant,and the occurrence state of iron and titanium were employed to study the reduction mechanism.Results show that the reduction mechanism of graphite powder was different with bituminous coal and coke because,in the early reaction stage,solid-solid reduction reaction was the main reaction way,but along with the acceleration of the gasification reaction,indirect reduction reaction became the main reaction way.Consequently,a small dosage of graphite power can provide satisfying reduction effects.However,the entire reduction process of bituminous coal and coke is mainly indirect reduction reaction.Tests also revealed that CaO decomposed from CaCO3 changed the reduction process because Ca2+replaced the Fe2+in titanium-containing minerals,which generated some CaTiO3.In addition,CaCO3 also promoted the growth of metallic iron particles.Consequently,DRIP with high iron recovery and low content of TiO2 was obtained through a magnetic separation process.In coal-based direct reduction process,we also found that CaO and CO2 decomposed from CaCO3 can promote the gasification reaction because CaO improved the gasification rate and CO2 was supplied for the gasification reaction.Besides,by comparing different measurement methods of iron particle size,we found that the area method was more suitable for the measurement of irregular-shaped metallic iron particles generated in the reduction of TTM.