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通过热解重量分析、X 射线衍射分析、能量分散 X 射线分析和金相分析,研究了南非 Transvaal 的 Bushveld 杂岩的天然铬铁矿在1416℃用石墨还原时的行为。试验期达120分钟,得到了99%还原。此项研究的特定目的就是描绘出用石墨还原铬矿的还原机理,在还原度达70%的部分还原的铬铁矿里观察到分区现象。其内核富铁,而外核的铁被消耗殆尽。能量分散 X 射线分析表明,Fe~(2+)和 Cr~(3+)离子已向外扩散,而 Cr~(2+)、Al~(3+)和 Mg~(2+)离子已向内扩散。根据随着还原程度的加大尖晶石相的组成仍保持其化学计量这一假设,提出了下述还原机理:(a)起初,在铬铁矿颗粒表面的 Fe~(3+)和 Fe~(2+)离子被还原成金属状态;此后紧接着 Cr~(3+)离子被还原成二价状态;(b)向颗粒中心扩散的 Cr~(2+)离子在内核与外核间的交界处将颗粒表面下尖晶石中的 Fe~(3+)还原成 Fe~(2+),Fe~(2+)离子向表面扩散,在表面被还原成金属钛:(c)当铁被完全还原之后,cr~(3+)和任何存在的 Cr~(2+)被还原成金属状态,剩下一种无铁和铬的尖晶石 MgAl_2O_4。
The results of gravimetric analysis, X-ray diffraction analysis, energy dispersive X-ray analysis and metallographic analysis were used to study the behavior of natural chromite in Bushveld complex in Transvaal, South Africa, with graphite at 1416 ℃. The test period of 120 minutes, got 99% reduction. The specific purpose of this study was to characterize the reduction mechanism of chromium ore with graphite and the zoning phenomenon was observed in partially reduced chromite ore with a reduction of 70%. The core is iron-rich, while the outer core of iron is depleted. Energy dispersive X-ray analysis shows that Fe 2+ and Cr 3+ ions have been diffused outward while Cr 2+, Al 3+, and Mg 2+ ions have been diffused Within the proliferation. Based on the assumption that the composition of the spinel phase retains its stoichiometry as the degree of reduction increases, the following reduction mechanisms are proposed: (a) Initially, Fe 3+ and Fe on the surface of chromite particles Ions are reduced to the metal state; Cr ~ (3 +) ions are reduced to the divalent state immediately afterwards; (b) Cr ~ (2+) ions diffused into the center of the particle (3+) in the spherulites below the grain surface to Fe2 + and Fe2 + ions diffuses to the surface and is reduced to titanium metal on the surface: (c) when After iron is completely reduced, cr ~ (3+) and any existing Cr ~ (2+) are reduced to the metal state, leaving an iron- and chromium-free spinel MgAl 2 O 4.