采用硝酸介质加压浸出处理红土镍矿，考察了初始硝酸浓度、浸出温度、保温时间和液固比对有价组分浸出率的影响，确定了该工艺的可行性。得到优化工艺条件为初始硝酸浓度330 kg/t，浸出温度190℃，保温时间60 min，液固比1.5:1~1.7:1 mL/g。最优工艺条件下，镍、钴的浸出率均大于85%，镁浸出率为80%，铝的浸出率大于60%，铁的浸出率低于1%，产出了含铁55%的富铁渣。对浸出液采用氧化镁梯级沉淀的方法，控制温度85℃、pH?3.0，可除掉95%的铁；控制pH=4.0~4.3，可除掉99%以上的铝，原矿中约90%以上的钪随铝进入渣相，得到含钪近1000 g/t的铝钪富集物；调节pH=7.5~8.0，溶液中的镍钴沉淀完全，得到含镍24.8%和含钴2.3%的氢氧化镍钴渣，实现了镍、钴与铁、铝高效分离和富集。梯级沉淀后的硝酸镁溶液蒸发结晶，在500℃下煅烧，得到轻质氧化镁；回收热分解产生的氮氧化物气体再生硝酸，常压下再生率达92%以上，实现了红土镍矿中有价组分的高效分离和浸出介质的循环利用。
The treatment of laterite ore by pressure leaching using nitric acid medium was studied. The nitric acid pressure leaching of nickel laterite was feasible based on series experiments for valuable components of initial concentration of nitric acid, leaching temperature, leaching duration, and liquid to solid ratio of the process. More than 85% Ni and Co, 80% Mg, over 60% Al and less than 1% Fe were extracted, and iron slag including 55% Fe was produced followed by optimal conditions of leaching temperature of 190℃, leaching duration of 60 min, initial concentration of nitric acid of 330 kg/t and liquid to solid ratio ranged from 1.5:1 to 1.7:1 mL/ g. Then Fe, Al and Ni, Co in the leaching solution were separated and enriched further, by the step of replenishing MgO. When the temperature was 85℃ and the pH was around 3.0, 95% Fe was removed. Then with controlled pH among 4.0~4.3, more than 99% Al was removed and more than 90% Sc was in the slag with Al which contained nearly 1000 g/t Sc. With increased pH among 7.5~8.0, Ni and Co were precipitated completely to produce hydroxide Ni, Co slag including 24.8% Ni and 2.3% Co. The residual Mg(NO3)2 solution was first evaporated and then thermal decomposed at 500℃ to obtain MgO. The nitrogen oxide gas generated by thermal decomposition was recovered to regenerate HNO3. The efficiency of recycled HNO3 was more than 92% in the atmospheric pressure.
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