还原剂及脱磷剂对高磷鲕状赤铁矿直接还原-磁选影响的研究进展

这是一篇矿业工程领域的文章。综述了还原剂及脱磷剂对高磷鲕状赤铁矿直接还原的影响,从煤和其他还原剂两个方面归纳了还原剂对高磷鲕状赤铁矿还原影响的研究现状,从单一脱磷剂和组合脱磷剂两种使用方式总结了脱磷剂的研究进展。指出了高磷鲕状赤铁矿直接还原-磁选工艺存在的问题,根据目前存在问题提出了未来针对高磷鲕状赤铁矿直接还原-磁选研究方向的建议。

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

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.

Behaviors of vanadium and chromium in coal-based direct reduction of high-chromium vanadium-bearing titanomagnetite concentrates followed by magnetic separation

The reduction behaviors of FeO·V2O3 and FeO·Cr2O3 during coal-based direct reduction have a decisive impact on the efficient utilization of high-chromium vanadium-bearing titanomagnetite concentrates. The effects of molar ratio of C to Fe n(C)/n(Fe) and temperature on the behaviors of vanadium and chromium during direct reduction and magnetic separation were investigated. The reduced samples were characterized by X-ray diffraction(XRD), scanning election microscopy(SEM) and energy dispersive spectrometry(EDS) techniques. Experimental results indicate that the recoveries of vanadium and chromium rapidly increase from 10.0% and 9.6% to 45.3% and 74.3%, respectively, as the n(C)/n(Fe) increases from 0.8 to 1.4. At n(C)/n(Fe) of 0.8, the recoveries of vanadium and chromium are always lower than 10.0% in the whole temperature range of 1100-1250 °C. However, at n(C)/n(Fe) of 1.2, the recoveries of vanadium and chromium considerably increase from 17.8% and 33.8% to 42.4% and 76.0%, respectively, as the temperature increases from 1100 °C to 1250 °C. At n(C)/n(Fe) lower than 0.8, most of the FeO·V2O3 and FeO·Cr2O3 are not reduced to carbides because of the lack of carbonaceous reductants, and the temperature has little effect on the reduction behaviors of FeO·V2O3 and FeO·Cr2O3, resulting in very low recoveries of vanadium and chromium during magnetic separation. However, at higher n(C)/n(Fe), the reduction rates of FeO·V2O3 and FeO·Cr2O3 increase significatly because of the excess amount of carbonaceous reductants. Moreover, higher temperatures largely induce the reduction of FeO·V2O3 and FeO·Cr2O3 to carbides. The newly formed carbides are then dissolved in the γ(FCC) phase, and recovered accompanied with the metallic iron during magnetic separation.

Synchronous enrichment of phosphorus and iron from a high-phosphorus oolitic hematite ore to prepare Fe-P alloy by direct reduction-magnetic separation process

In this study,direct reduction-magnetic separation process was applied to enrich phosphorus and iron to prepare Fe-P crude alloy from a high phosphorus oolitic hematite ore(HPOH).The results show that at lower temperatures and with absence of any of additives,Fe cannot be effectively recovered because of the oolitic structure is not destroyed.In contrast,under the conditions of 15%Na_(2)SO_(4)and reducing at 1050℃ for 120 min with a total C/Fe ratio(molar ratio)of 8.5,a final Fe-P alloy containing 92.40%Fe and 1.09%P can be obtained at an overall iron recovery of 95.43%and phosphorus recovery of 68.98%,respectively.This metallized Fe-P powder can be applied as the burden for production of weathering resistant steels.The developed process can provide an alternative for effective and green utilization of high phosphorus iron ore.

Effect of reducing agents on reducing atmosphere in coal-based direct reduction of beach titanomagnetite

Beach titanomagnetite(TTM)provides a cheap alternative source of Fe and Ti,but this ore is difficult to process to make suitable concentrates for the blast furnace.Recently studies showed that it is feasible to separate Fe and Ti by coal-based direct reduction.In this study,beach TTM was selected as the research object,the effects of reducing agents on reducing atmosphere in coal-based direct reduction of beach TTM were analyzed,and the role of volatiles was also studied.The results showed that when bitumite and coke were used as reducing agents of TTM,the CO produced from volatiles was involved in the reduction reaction,and the generated CO_(2) provided the raw material for the reaction of TTM.The reduction effect of bitumite was better than that of coke.The reason is that bitumite+TTM had a higher gas generation rate and produced a higher CO partial pressure,while coke+TTM had a lower gas generation rate and produced a lower CO partial pressure.When graphite was used as a reducing agent,there was a solid-solid reaction in the early stage in the reaction.With the continuous accumulation of CO_(2),the Boudouad reaction started and accelerated.Graphite+TTM also produced a higher CO partial pressure.

Pilot scale test of producing nickel concentrate from low-grade saprolitic laterite by direct reduction-magnetic separation

The enrichment of Ni from a low-grade saprolitic laterite ore,which has been pre-treated by high pressure grinding roller（HPGR） to be 74% passing 0.074 mm and contains 0.92% Ni,18.47% Fe,10.61% MgO and 42.27% SiO2,was conducted by using pelletizing,rotary kiln reduction and magnetic separation process on a semi industrial scale,and the effects of reduction duration,mass ratio of coal to pellets（C/P）,the types of magnetic separator,the sections of grinding-separation and the grinding fineness on the recovery of Ni and Fe were examined.It is shown that nickel concentrate containing 3.13 % Ni and 59.20 % Fe was achieved at recoveries of 84.36 % and 71.51% for Ni and Fe,respectively under the following conditions：reducing at （1120±40） ℃ for 120 min,C/P being 1.0,wet grinding of reduced pellets up to 70%-87% passing 0.074 mm and a magnetic field intensity of 238.8 kA/m during the first section of grinding-magnetic separation,and a grinding fineness of 84%-91% passing 0.045 mm and a magnetic intensity of 39.8 kA/m during the second section of grinding-magnetic separation.The enriched Ni containing concentrate has a low content of S and P,and can be used for further processing to produce high-grade ferronickel alloy.