海滨钛磁铁矿包埋法直接还原—磁选钛铁分离工艺及机理

发布时间：2018-06-09 20:51

本文选题：海滨钛磁铁矿 + 直接还原-磁选　；参考：《北京科技大学》2017年博士论文

【摘要】：海滨钛磁铁矿储量丰富,采选成本低廉,但用常规的选矿方法得到的铁精矿中铁品位低、TiO_2含量高,冶炼难度大,并且钛进入了高炉渣,导致钛资源的浪费。研究表明,内配煤直接还原-磁选工艺可以实现钛磁铁矿中钛、铁的有效分离,但煤中所含的灰分会进入到非磁性产品(即钛产品)中,导致钛产品中的TiO_2品位低,未实现钛的有效富集。因此,本论文采用包埋法直接还原-磁选工艺,即只将海滨钛磁铁矿压成球,煤不与钛磁铁矿混合,而是包埋在球团的周围进行直接还原焙烧,目的是实现铁和钛的同时回收。以铁品位57.29%、TiO_2品位11.42%的印尼某海滨钛磁铁矿弱磁选精矿为试样,系统研究了包埋法直接还原-磁选钛铁分离工艺及机理。考察了添加剂种类及用量、还原剂种类及用量、还原时间和温度等对包埋法直接还原-磁选钛铁分离并分别富集效果的影响。结果表明,无论加入硫酸钠或萤石,还原铁产品铁回收率和钛产品TiO_2品位均较低,不能达到目标要求。还原剂影响钛铁分离效果,烟煤为还原剂得到的还原铁产品和钛产品的各指标较无烟煤和焦炭的好。延长还原时间能够提高还原铁产品中的铁品位和铁回收率,以及钛产品中的TiO_2品位。在最佳工艺条件下,得到了铁品位为90.48%、铁回收率为90.12%、TiO_2含量为0.93%的还原铁产品和TiO_2品位为45.58%、TiO_2回收率为95.35%的钛产品,实现了钛铁分离并分别富集。采用X射线粉晶衍射、扫描电镜、能谱分析和烟气分析等方法进行了机理研究。研究表明,加入添加剂硫酸钠或萤石不仅引入杂质,而且对钛磁铁矿的还原不利。包埋法的还原效果取决于还原剂反应性,气化反应性好的还原剂还原效果更好。原因是反应性好的烟煤,较低温度下能够提供更强的还原气氛,抑制铁橄榄石的生成;而反应性差的无烟煤和焦炭则相反,最终导致铁橄榄石的生成,不仅降低铁回收率,还促进液相产生,不利于还原气体扩散,抑制了还原反应的进行。通过对还原时间和温度的研究,确定了含有Mg类质同象的钛磁铁矿还原历程为Fe_2(Mg,Fe)_(0.75)Ti_(0.25)O_4→(Fe,Mg)_2TiO_4→(Fe,Mg)TiO_3→(Fe,Mg)Ti_2O_5→MgTi_2O_5+Ti_3O_5。
[Abstract]:Seaside titanomagnetite is rich in reserves and low in cost of mining and dressing. However, the iron concentrate obtained by conventional dressing method has high iron grade and high content of TiO-2, and it is difficult to smelt, and titanium enters into blast furnace slag, which leads to the waste of titanium resources. The results show that the direct reduction and magnetic separation process can effectively separate titanium and iron from titanomagnetite, but the ash contained in the coal will enter into non-magnetic products (i.e. titanium products), resulting in the low grade of TiO2 in titanium products. The effective enrichment of titanium was not realized. Therefore, in this paper, the direct reduction-magnetic separation process is adopted, that is, only the beachfront titanomagnetite is pressed into a ball, the coal is not mixed with the titanomagnetite, but is buried around the pellet for direct reduction roasting, in order to realize the simultaneous recovery of iron and titanium. The separation process and mechanism of titanium-iron by direct reduction magnetic separation were systematically studied with a weak magnetic concentrate of a seaside titanomagnetite in Indonesia with iron grade 57.29 and TiO-2 grade 11.42%. The effects of additives, amount of additives, reduction time and temperature on the separation and enrichment of iron titanate by direct reduction and magnetic separation were investigated. The results show that the iron recovery rate of iron products and the TiO-2 grade of titanium products are lower than those of titanium products, and can not meet the requirements of the target, regardless of the addition of sodium sulfate or fluorite. Reducing agent affects the separation effect of iron and titanium. Bituminous coal is better than anthracite and coke in each index of reducing iron product and titanium product. Prolonging the reduction time can improve the iron grade and iron recovery rate in the reductive iron product and the tio _ 2 grade in the titanium product. Under the optimum technological conditions, the products with iron grade 90.48, iron recovery 90.12% TiO2 0.93% and TiO2 45.58% TiO2 recovery 95.35% were obtained. The mechanism was studied by means of X-ray powder diffraction, scanning electron microscope, energy spectrum analysis and flue gas analysis. The results show that the addition of sodium sulfate or fluorite is not only impurity, but also disadvantageous to the reduction of titanomagnetite. The reduction effect of the entrapped method depends on the reactivity of the reductant, and the reduction effect of the reductant with good gasification reactivity is better. The reason is that the bituminous coal with good reactivity can provide a stronger atmosphere of reduction and inhibit the formation of iron olivine at lower temperature, whereas the unreactive anthracite and coke, on the contrary, lead to the formation of iron olivine, which not only reduces the recovery rate of iron, but also decreases the rate of iron recovery. It also promotes the production of liquid phase, which is unfavorable to the diffusion of reducing gas and inhibits the process of reduction reaction. Based on the study of reduction time and temperature, the reduction process of magnetite containing mg type magnetite is determined to be: the reduction process of Fe2MgTi2O5 MgTi2O5 Ti3O5 structure is as follows: titio 0.75TiO4 titio 0.25TiO4 tio 0.75TiO4 titio 0.75 tio _ 2tio _ 4 titio _ (0.75) tio _ (2tio) tio _ (5) tio _ (tio _ 2O _ 5).
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TD951

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