CaO对海滨钛磁铁矿精矿直接还原-磁选工艺中还原气氛的影响

Effect of CaO on reducing atmosphere in the direct reduction and magnetic separation process of beach titanomagnetite concentrate

以铁品位为58.58%、TiO2品位为12.04%的海滨钛磁铁矿精矿为试样,进行煤基直接还原–磁选试验.从反应产生的CO和CO2气体组成、总反应的气化速率、CO分压值、金属化率、矿物组成等角度进行分析,查明了CaO在海滨钛磁铁矿精矿直接还原-磁选工艺中的作用机理.研究结果表明,CaO可以提高还原剂的气化速率,促进钛磁铁矿的还原,增加CO_2气体的产生量,从而降低CO分压值.同时发现CaO可以参与固固反应,降低含钛矿物中的FeO含量,也有利于钛、铁组分的迁移和富集,促进金属铁颗粒的聚集长大.因此,添加CaO有利于通过磨矿-磁选促进钛铁分离与回收.

The exploitation of refractory iron ores has become increasingly important around the world because of the rapid depletion of easy-to-process iron ores.Ironsand is extensively distributed in the coastal areas of Indonesia,China,and New Zealand,and can provide an alternative to conventional iron ores.Although the composition of ironsand is partially dependent on its location and position,it approximates that of titanomagnetite(Fe3-xTixO4)containing^60%total Fe(TFe).However,the conventional smelting route for smelting beach titanomagnetite concentrate with carbon uses a blast furnace to produce pig iron and titanium slag,which has many disadvantages.First,the smelting process requires lots of coke and a high temperature.Second,sinter blend allows for the addition of only a small amount of beach titanomagnetite concentrate to ensure the desired sintering characteristics.Therefore,in order to efficiently utilize beach titanomagnetite,the processes of direct reduction followed by magnetic separation are generally applied to recover iron.In addition,additives such as CaO,CaCO3,and NaCO3 are often used in the reduction roasting process.These additives may improve the reduction characteristics or facilitate the growth of iron particles to some extent.In order to study the effect of the additive CaO on the direct reduction and magnetic separation of beach titanomagnetite concentrate which contains 58.58%of TFe and 12.04%of TiO2,the mechanisms were investigated by gas composition of CO and CO2,gasification rate of total reaction,CO partial pressure,metallization rate,mineral composition and so on.The results indicate that adding CaO can improve the gasification rate of reductant and facilitate the reduction of titanomagnetite,which improves the generation of CO2 gas and decreases the CO partial pressure.Besides,CaO can participate in solid-solid reaction,reduce FeO content in Ti-containing mineral and facilitate the migration and enrichment of Ti and Fe components,which promote the growth of metallic iron particles.Thus,adding CaO is good for the separation and recovery of Fe and Ti by grinding and magnetic separation.