Phase transformation of nickel laterite ores in the selective reduction roasting process
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摘要: 針對傳統選礦方法難以回收低品位紅七鎳礦中有價金屬鎳的問題,采用選擇性還原焙燒法研究了不同焙燒溫度以及不同焙燒時間條件下紅土鎳礦(Ni品化為1.49%)中發生的微觀結構變化以及相變轉化.通過X射線衍射、掃描電鏡及X射線能譜分析等測試手段分析表明,在不同焙燒溫度及不同時間條件下經選擇性還原后的紅土鎳礦中,鎳氧化物逐漸被還原成鎳鐵合金相,鐵氧化物主要轉變成浮氏體相,硅酸鹽主要以橄欖石形式存在.最后通過還原焙燒磁選試驗證實,還原劑為煙煤,添加劑為NCS,兩者用量分別為原礦質量的2%和7%,在1200℃條件下焙燒50min,磁選分離得到鎳鐵產品中鎳品位為9.78%,鎳的回收率為92.06%,鎳鐵回收率差為62.51%,實現了紅土鎳礦中鎳鐵的選擇性還原.Abstract: Since it is difficult to extract nickel from laterite ores with low nickel grade by traditional beneficiating methods, the microstructure and phase transformation of a nickel laterite ore with the nickel grade of 1.49% were investigated by using a selective reduction roasting method at different roasting temperatures and time. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) results show that after selective reduction roasting at different roasting temperatures and time, nickel-ferrous minerals in the nickel laterite ore are reduced to ferronickel gradually, while ferrous minerals are mainly transformed to wustite. Silicate nfinerals exist in the formation of olivine in the roasted ore. Reduction roasting and magnetic separation experiments illustrate that when the nickel laterite ore with the addition of 7% NCS as the additive and 2% soft coal as the reductant roasts for 50 min at 1200℃, the ferronickel product obtained from magnetic separation has the nickel grade of 9.78% with the nickel recovery of 92.06%, and the recovery difference of nickel and iron is 62.51%. The experimental result indicates that nickel-ferrous and ferrous minerals were reduced selectively.
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Key words:
- nickel ore treatment /
- ore reduction /
- ore roasting /
- magnetic separation /
- phase transitions
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