印尼某红土矿硫酸加压浸出矿物组成变化研究

印尼苏拉威西岛La-paopao矿区红土镍矿储量约7326万吨,含镍约为1.25%,以此红土镍矿为对象,系统分析了矿样中主要矿物的种类、赋存状态及产出特征。结果表明:矿样含Fe(40.15%),Ni(1.42%),Co(0.15%),Mg(0.37%),SiO₂(6.92%)(质量分数),是典型的褐铁型红土镍矿;组成矿物主要为针铁矿、水针铁矿、高岭石、硬锰矿等;镍钴主要以类质同象或在结晶过程中以机械夹杂形式分布于褐铁矿中,其次分布于硬锰矿中,还有部分以独立矿物镍钴土矿形式存在。基于矿物特征,采用硫酸高压浸出工艺处理该红土镍矿,在最佳工艺条件下,镍浸出率超过96%,钴浸出率在97%以上,铁浸出率小于1%,实现了镍钴选择性提取。最后分析了渣中残余镍、钴未能浸出的原因以及各金属的浸出行为。未浸出镍钴部分可能存在于锰土矿中,另一部分则在Fe³⁺和Al³⁺高温水解沉淀过程中被夹带进入浸出渣。在高温下Fe³⁺强烈水解并释放出酸,Al³⁺大部分水解并释放出酸,并沉淀入渣。

Mineral Components Transformation of a Laterite from Indonesia by Sulfuric Acid Pressure Leaching

With the gradual depletion of nickel sulfide ore,the supply of nickel was gradually changing to nickel laterite ore,and the proportion was increasing year by year,which reached more than 50%.High pressure acid leaching(HPAL)had become a hot spot in the treatment of low-grade nickel laterite ore in recent years.HPAL could recover nickel,cobalt and other elements efficiently and comprehensively,and the product could be either nickel(cobalt)metal or nickel(cobalt)sulfate,which could be used in steel enterprises or battery industry.However,the composition of laterite ore in different areas was complex and changeable.It was necessary to systematically explore the changes of composition minerals before and after leaching in order to obtain the optimum conditions when HPAL was used to treat nickel laterite ore.The nickel laterite ore deposit in La-paopao mining area on Sulawesi Island of Indonesia had a reserve of about 73.26 million tons,containing about 1.25%nickel,which had important development and use value.The types,occurrence states and production characteristics of the main minerals in the samples were systematically analyzed by means of chemical analysis,X-ray diffraction(XRD)analysis,microscope analysis,scanning electron microscope(SEM)and energy dispersive spectroscopy(EDS)analysis.In addition,the effects of leaching temperature,sulfuric acid dosage,leaching duration and slurry liquidsolid ratio on the leaching process were explored.Based on the analysis of the metals leaching behavior and the mineral composition changes of raw materials and leach residue,the optimum conditions for treating nickel laterite ore deposit in La-paopao mining area by HPAL were determined.The results showed that the ore sample was a typical limonitic laterite ore containing Fe(40.15%),Ni(1.42%),Co(0.15%),Mg(0.37%),Si O2(6.92%)(mass fraction).The main components of minerals were goethite,hyrogoethite,kaolin,and psilomelane etc.Nickel and cobalt were mainly distributed in limonite in the form of isomorphism or mechanical inclusion via the crystallization process,followed by psilomelane,and nickel and cobalt could also be found in nickel asbolane as the independent mineral.The leaching rates of Ni and Co in nickel laterite ore were obviously affected by temperature.With the increase of temperature,the leaching rate of Ni and Co increased significantly and reached a peak at 255℃.At this time,the leaching rates of Ni and Co were 96.1%and 97.7%,respectively.When the sulfuric acid dosage reached 330 kg·t-ore^-1,the leaching rates of Ni and Co tended to stabilize,and the leaching rates of Ni and Co were 95.8%and 97.2%,respectively.When the leaching duration was 45 min,the leaching rates of Ni and Co were 95.8%and 97.2%,respectively.With the extension of leaching duration,the leaching rates of Ni and Co tended to be stable.When the slurry liquid-solid ratio was 2 m³-water·t-ore^-1,the leaching rates of Ni and Co were higher than 96%.The leaching rates of Mn and Mg were sensitive to temperature changes.The leaching rate of Al decreased as the temperature increased,and the leaching rate of Fe was about 1%.By comparing the composition minerals before and after leaching,the optimum conditions of HPAL were determined as follows:sulfuric acid dosage of 330 kg·t-ore^-1,leaching temperature of 255℃,leaching duration of 45 min and slurry liquid-solid ratio of 2 m³-water·t-ore^-1.It had been experimented that under the optimal technological conditions,the leaching rates of Ni,Co could be more than 96%and 97%,while that of Fe was less than 1%,which ensured the selective extraction of Ni and Co.In the process of HPAL,the leaching rates of Ni,Co and Mn were almost the same with the change of conditions,this was because they had a common carrier mineral,which was manganite.When the temperature was lower than 220℃,the structure of laterite was not completely destroyed,which leaded to the failure leaching of part of nickel and cobalt.After the temperature raised,the structure of the nickel-cobalt-containing iron minerals that were difficult to handle under normal temperature and pressure could be destroyed,thereby increasing the nickel and cobalt leaching rates.When the leaching rate of nickel and cobalt reached the peak,it did not change much with the increase of acid dosage,temperature and leaching duration.At this time,the part of non-leaching nickel and cobalt might exist in the manganese ore,and the other part might be into the leach residue because of the Fe³⁺and Al³⁺hydrolysis and precipitation.When the leaching duration was 30 min,most of the nickel and cobalt existing in the iron mineral had been leached,and the leaching rate of nickel and cobalt was about 90%,which indicated that the iron mineral was decomposed rapidly by sulfuric acid under high temperature and high pressure.But the leaching rate of Fe always remained at a low level,which was due to the Fe³⁺had been transformed into hematite precipitation at a low temperature(180℃)and short time(30 min).