转炉渣中镁铁尖晶石的形成机理及磁选提铁研究

发布时间：2018-08-20 16:03

【摘要】：对于已磁选出金属铁的冷态工业转炉渣,渣中铁氧化物中的铁的回收一直是冶金领域的一个难题。本文的研究思路是将其转变成镁铁尖晶石(MgFe_2O_4尖晶石相),然后磁选选出从而回收再利用。主要研究内容如下:MgFe_2O_4尖晶石相的可分离性研究、合成转炉渣中MgFe_2O_4尖晶石相的形成影响因素研究以及工业转炉渣改质、磁选和经济性分析。通过烧成试验,即采用化学纯试剂Fe_2O_3和MgO在1400℃空气气氛下煅烧2h合成MgFe_2O_4尖晶石相。结果表明,试验合成了 MgFe_2O_4尖晶石相,其Fe与Mg原子百分比之比为2.48～2.65。此外,MgFe_2O_4尖晶石相的颗粒为不规则的多面体,平均尺寸为12.89μm。Factsage热力学模拟结果显示MgFe_2O_4尖晶石相主要在900℃～1400℃通过固相反应形成,在1716.76℃开始出现液相,说明其为高熔点物质。对MgFe_2O_4尖晶石相进行了磁化特性测试,并对其磁性来源进行了理论分析。结果表明,MgFe_2O_4尖晶石相的比磁化率为(8.03～206.84)×10-5m3/kg,属于强磁性矿物,其磁性来源于A离子(Mg_(0.1)~(2+)Fe_(0.9)~(3+))和B离子(Mg_(0.68)~(2+)Fe_(0.22)~(2+)Fe_(1.1)~(3+))未抵消的平行反向磁矩,分子磁矩为1.88μB。相比之下,工业转炉渣的比磁化率仅为(0.024～0.136)×10-5m3/kg,属于弱磁性矿物,因此工业转炉渣中的MgFe_2O_4尖晶石相具有可分离性。采用化学纯试剂CaO、SiO_2、Fe_2O_3和MgO在不同的煅烧温度,空气气氛下煅烧2h合成了转炉渣,研究了煅烧温度对渣中MgFe_2O_4尖晶石相形成过程的影响。结果表明,理想的煅烧温度为1250℃和1300℃,渣中只含有β-C2S和MgFe_2O_4尖晶石相,为工业转炉渣磁选MgFe_2O_4尖晶石相提供了可行性。在1200℃～1300℃,MgFe_2O_4尖晶石相生成反应的化学反应活化能Ea为54.30kJ·mol-l。提高煅烧温度有利于MgFe_2O_4尖晶石相的形成和长大,其平均直径与煅烧温度呈指数增加的关系。研究了恒温时间对合成转炉渣中MgFe_2O_4尖晶石相形成过程的影响。结果表明,在1300℃空气气氛下煅烧并恒温不同的时间,合成转炉渣中只含有β-C2S和MgFe_2O_4尖晶石相。假设MgFe_2O_4尖晶石相由固相反应形成,则其形成动力学过程受扩散控制,满足Glinstling方程,并且反应的速率常数为9.51202×10-4s-1。增加恒温时间有利于MgFe_2O_4尖晶石相颗粒的长大,其平均直径与恒温时间t1/2呈线性增加的关系。研究了主要化学成分对合成转炉渣中MgFe_2O_4尖晶石相形成过程的影响。结果表明:1)碱度对MgFe_2O_4尖晶石相的形成有重要的影响,试验中合适的渣碱度为2;2)合成转炉渣中Fe_2O_3的含量较高时有利于提高其熔化性,能够促进MgFe_2O_4尖晶石相的形成、长大和聚集。试验中合适的Fe_2O_3含量为33.30%和38.67%;3)合成转炉渣中MgO的含量较低时渣的熔化性较好。试验中合适的MgO含量为3.95%和5.80%;4)MgFe_2O_4尖晶石相的生成量随合成转炉渣中Fe_2O_3与MgO总量的增加而增加,并且当总量为30.31%～55.07%时,MgFe_2O_4尖晶石相的生成率在80%以上;5)不论转炉渣中铁含量的高低,均可通过适当地改质使其形成MgFe_2O_4尖晶石相,这种方法对转炉渣具有普遍适用性。对工业转炉渣进行了改质、磁选并分析了其经济性。结果表明,向工业转炉渣中加入质量分数为6%的SiO_2来降低渣碱度,在1400℃空气气氛下恒温15min,然后以1℃/min的速度缓慢冷却到1270℃,可使改质转炉渣形成MgFe_2O_4尖晶石相,其颗粒尺寸大于30μm。干法磁选后,磁性渣中的全铁含量从工业转炉渣中的21.20%增加到37.00%,提高了 15.80%,比未经改质直接磁选渣中铁氧化物的效果(仅提高了 1.55%～8.10%)要好,说明本试验的研究方法有利于冷态工业转炉渣中铁氧化物中铁的回收。非磁性渣可用于生产高附加值的建筑材料。改质1吨工业转炉渣,需要投入159.62元,但可节省其他费用373.83元,合计节省214.21元。此外,采用该方法还可节省大量的自然资源和占地面积,减少了CO2的排放。由此可见,对工业转炉渣进行改质磁选MgFe_2O_4尖晶石相的方法具有巨大的经济效益和环境效益,有利于实现钢铁工业的可持续发展。
[Abstract]:The recovery of iron from iron oxide in cold industrial converter slag has always been a difficult problem in metallurgical field. The research idea of this paper is to transform it into mafic spinel (MgFe_2O_4 spinel phase) and then select it by magnetic separation for recycling. Separation study, formation of MgFe_2O_4 spinel phase in Synthetic Converter slag, modification of industrial converter slag, magnetic separation and economic analysis were carried out. MgFe_2O_4 spinel phase was synthesized by calcining chemical pure reagent Fe_2O_3 and MgO in air atmosphere at 1400 C for 2 hours. The ratio of Fe to Mg atoms is 2.48 to 2.65. In addition, the particles of MgFe_2O_4 spinel phase are irregular polyhedron with an average size of 12.89 micron. Factsage thermodynamic simulation results show that MgFe_2O_4 spinel phase is mainly formed by solid-state reaction at 900 ~1400 ~1716.76 ~C, indicating that MgFe_2O_4 spinel phase is a high melting point material. Magnetization characteristics of MgFe_2O_4 spinel phase were tested and its magnetic source was theoretically analyzed. The results show that the specific susceptibility of MgFe_2O_4 spinel phase is (8.03~206.84)*10-5m3/kg, which belongs to strong magnetic mineral. The magnetic properties of MgFe_2O_4 spinel phase come from A ion (Mg_ (0.1)~ (2+) Fe_ (0.9)~ (3+) and B ion (Mg_ (0.68)~ (2+) Fe_ (0.22)~ (2+) Fe_ (1.1+) Fe_ (1). In contrast, the specific magnetic susceptibility of industrial converter slag is only (0.024-0.136)*10-5m3/kg, so the MgFe_2O_4 spinel phase in industrial converter slag is separable. Chemical pure reagents CaO, SiO_2, Fe_2O_3 and MgO are used at different calcination temperatures in air. The converter slag was synthesized by calcination in atmosphere for 2 h. The effect of calcination temperature on the formation of MgFe_2O_4 spinel phase in the slag was studied. The results show that the ideal calcination temperature is 1250 C and 1300 C, and the slag contains only beta-C2S and MgFe_2O_4 spinel phase. It is feasible for magnetic separation of MgFe_2O_4 spinel phase from industrial converter slag. The activation energy Ea of spinel formation reaction is 54.30 kJ The spinel phase of MgFe_2O_4 is assumed to be formed by solid state reaction. The formation kinetics of spinel phase is controlled by diffusion, and the reaction rate constant is 9.51202 6550 The average diameter of Fe_2O_4 spinel phase increases linearly with the constant temperature time t_1/2. The effect of main chemical composition on the formation of MgFe_2O_4 spinel phase in converter slag was studied. The results show that: (1) basicity has an important effect on the formation of MgFe_2O_4 spinel phase, and the suitable basicity of slag is 2; When the content of Fe_2O_3 in converter slag is high, the meltability of the slag can be improved, and the formation, growth and aggregation of MgFe_2O_4 spinel phase can be promoted. The amount of spinel formation increases with the increase of the total amount of Fe_2O_3 and MgO in the converter slag, and when the total amount of Fe_2O_3 and MgO is 30.31%-55.07%, the formation rate of MgFe_2O_4 spinel phase is above 80%. 5) Regardless of the iron content in the converter slag, the spinel phase of MgFe_2O_4 can be formed by proper modification, which is generally suitable for the converter slag. The results show that adding 6% SiO_2 into the converter slag can reduce the basicity of the slag. The slag is cooled at 1400 C for 15 min and then slowly cooling to 1270 C at 1 C/min. The MgFe_2O_4 spinel phase is formed in the converter slag. After dry magnetic separation, the total iron content in magnetic slag increased from 21.20% to 37.00% and 15.80% respectively, which was better than that of iron oxide in direct magnetic separation slag without modification (only 1.55% ~ 8.10%). It shows that the research method of this experiment is beneficial to iron oxide in cold industrial converter slag. Recovery. Non-magnetic slag can be used to produce high value-added building materials. Modification of one ton of industrial converter slag requires investment of 159.62 yuan, but other costs can be saved by 373.83 yuan, a total of 214.21 yuan. In addition, this method can save a lot of natural resources and land area, and reduce CO2 emissions. Modified magnetic separation of MgFe_2O_4 spinel phase has great economic and environmental benefits and is conducive to the sustainable development of iron and steel industry.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2018
【分类号】：TD951;TD924

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