红土镍矿内配煤压块还原特性及高温熔分制备镍铁

Reduction characteristics of coal-bearing briquettes of nickel laterite ores and preparation of Fe-Ni alloy by high temperature melting and separation

采用内配煤压块预还原-高温熔分工艺从红土镍矿中提取镍铁合金。研究了褐铁矿型和腐泥土型2种不同性质红土镍矿的矿物特性及其对内配煤压块在不同温度下的还原过程中含铁、镍氧化矿物还原失氧的影响规律,分析了预还原产物高温熔分制备镍铁合金产品的含镍品位和有价元素综合收得率与红土镍矿性质和压块C、O原子物质的量之比n(C)/n(O)之间的关系。结果表明,还原温度对腐泥土型红土镍矿内配煤压块的还原影响很大,n(C)/n(O)为1.2的试样在1 200℃下还原30 min后,含铁、含镍矿物才能被充分还原成金属铁和镍,在较低温度(1 100~1 150℃)下即使延长还原时间也不能进一步提高还原率;褐铁矿型红土镍矿内配煤压块在1 150~1 200℃下还原10 min后,含铁、含镍矿物的还原率分别达到90%以上。红土镍矿内配煤压块在1 200℃预还原30 min后,升温到1 600℃保温30 min进行熔分,获得镍铁合金。用褐铁矿型红土镍矿内配煤压块预还原-熔分得到的镍铁合金中,镍含量随压块n(C)/n(O)增加而下降;相反,用腐泥土型红土镍矿内配煤压块预还原-熔分得到的镍铁合金中,镍含量随压块n(C)/n(O)增加而升高。缺碳配煤(n(C)/n(O)≤1.0)可抑制腐泥土型红土镍矿中含铁矿物的还原,但对含镍矿物还原的抑制作用更强,最终影响镍的综合收得率,降低了镍铁合金的镍含量。本研究可为开发新的红土镍矿火法提取技术、高效利用红土镍矿生产镍铁提供指导。

Fe-Ni alloy was prepared from carbon-bearing briquettes with nickel laterite ores by the process of carbothermal reduction and high temperature melting. The different mineral properties between limonite laterite ore and saprolite laterite ore and their effects on the oxygen-loss rate of iron and nickel-bearing minerals in the process of carbothermal reduction of the carbon-bearing briquettes at different temperatures were studied. The relationship between Ni content and the comprehensive yield rate of valuable elements in Fe-Ni alloy products prepared by high temperature melting with pre-reduction products and the properties of nickel laterite ore and the C/O molar ratio in coal-bearing briquettes had been analyzed. The results show that the reduction temperature has a great influence on the carbothermal reduction of saprolite laterite ore. Sample with C/O molar ratio 1.2 can be fully reduced to metal Fe and Ni only after 30 min reduction at 1 200 ℃. At a lower temperature as 1 100-1 150 ℃, even if the reduction time is infinitely extended, the reduction rate couldn′t be further improved. But for the carbon-bearing briquette of limonite laterite ore, it can reach a reduction rate both Fe and Ni above 90% after carbothermal reduction at 1 150-1 200 ℃ for 10 min. After the carbon-bearing briquette is pre-reduced at 1 200 ℃ for 30 min, then heated to 1 600 ℃ melting for 30 min, the Fe-Ni alloy is separated out from melting slag. The Ni content of Fe-Ni alloy separated from carbon-bearing briquette of limonite laterite ore by pre-reduction and melting is decreased with the increase of the C/O molar ratio. On the contrary, the Ni content of Fe-Ni alloy separated from carbon-bearing briquette of sapropelic laterite ore by pre-reduction and melting is increased with the increase of the C/O molar ratio. The carbon-bearing briquette with the C/O molar ratio less than 1.0 could inhibit the reduction of iron-bearing minerals in sapropelic laterite ore, but it has a stronger inhibition on the reduction of nickel-bearing minerals, which ultimately affects the comprehensive yield rate of nickel and reduces the Ni content in Fe-Ni alloy. This study can provide guidance for the development of new pyrometallurgical extraction technology of nickel laterite ore and the efficient utilization of nickel laterite ore to produce Fe-Ni alloy.