Pressure acid leaching of arid-region nickel laterite ore: Part II. Effect of ore type

A comparison of the leach chemistry and residue mineralogy has been carried out on the pressure acid leaching of nontronite, limonite and saprolite ores, using hypersaline water. Results are also compared with a typical arid-region laterite feed from Bulong, which consists of a blend of these ore types. Particular emphasis is placed on the influence of ore type on liquor analysis of iron, aluminium and magnesium, residue mineralogy and nickel extraction. Microprobe evidence is presented that incomplete nickel extraction results from the presence of unreacted minor phases present in the original ore, or from the presence of nickel in the amorphous silica, in apparent association with magnesium.     

The kinetics of the sulphuric acid leaching of nickel and magnesium from reduction roasted serpentine

Nickel may be extracted with partial selectivity over magnesium from laterites containing serpentine by reduction roasting followed by sulphuric acid leaching. This paper describes the results of a kinetic study of the sulphuric acid leaching of nickel and magnesium from the reduction roasted serpentine component of a typical laterite. The serpentine used in this work analyzed 1.65% nickel, 20.2% magnesium and 6.10% iron.Initially, leaches were carried out at temperatures of 30, 50 and 70° C to determine the acid requirement for complete nickel extraction using practical leaching conditions (25% solids) under which the acidity drops to a low level. A minimum acid addition of 60 g/l was needed, which gave 80% to 83% nickel extraction from material in which 85% of the nickel was reduced using hydrogen at 700° C. Under these conditions, about 17% of the magnesium was leached at each of the temperatures studied.To facilitate an understanding of leaching kinetics, leaches were then performed using constant acidities (0.1% solids) of 60, 30 and 15 g/l acid at temperatures of 30, 50 and 70° C. Closely sized particles (?65 + 100 mesh) were leached so that magnesium dissolution rates could be tested against established “shrinking core” models.The main conclusions are that, under the experimental conditions, nickel dissolution rates were chemically controlled by either $\text{2}\text{H}{}^{\mathrm{+}}\text{+}\text{1}\text{2}\text{O}{}_2\text{+ 2e →}\text{H}{}_2\text{O}$ or 2 H⁺ + 2e → H₂ occurring at the surfaces of the 40% nickel/iron alloy platelets formed during reduction. The rate controlling process had an activation energy of 11kcal/mole.During extraction of metallic nickel, the dissolution of magnesium follows a “shrinking core” kinetic model, which assumes the reaction is unimpeded by a surface layer of silica - a reaction product. Rates of magnesium dissolution during this stage of the reaction (up to 25% dissolved) were chemically controlled with an activation energy of 12 kcal/mole.At magnesium extractions above 25%, at which point all the metallic nickel had been extracted, the rate of silicate attack was limited by diffusion through a silica coating attached to particle surfaces.The results indicate that selectivity for nickel dissolution over that of magnesium does not depend strongly on acidity and temperature at the levels investigated.     

Characterization of scales obtained during continuous nickel laterite pilot-plant leaching

The processing of nickel by pressure acid leaching nickel laterite ores at 250 °C results in liquors supersaturated with respect to aluminum, iron, and silica. These can precipitate from the liquor and onto the autoclave interior (scaling). This reduces the availability of the autoclave. This article presents a methodology for characterizing scale using X-ray powder diffraction (XRPD), Rietveld analysis of the XRPD trace, and scanning electron microscopy/microprobe. This methodology is then used to characterize three scales formed during the continuous (pilot plant) pressure acid leaching of nickel laterites. Scales formed during the leaching of Western Australian ore, from an acid environment in hypersaline process water, contain mainly sodium alunite/jarosite as a solid solution together with minor hematite and amorphous silica. Scales formed during leaching of tropical nickel laterite, in low salinity process water, consist of an aluminum-rich hydronium alunite with hematite and low concentrations of amorphous silica. Ore mineralogy, leach liquor composition, acidity, and temperature, as well as precipitation kinetics, all appear to influence the scale mineralogy. This article discusses the influence of these factors on the formation of three scales.     

散装红土镍矿取制样方法研究

针对红土镍矿的地质化学特性,结合我国进口的红土镍矿主要为高铁低镁的褐铁矿型特点, 参照ISO、中国和日本相关制取样标准,通过大量现场试验的统计数据,建立了精密度较高、科学可行的散装红土镍矿取制样方法。用该方法对一船由印尼进口的红土镍矿制取样,然后进行检测,根据样品中镍、铁、水分检测结果得到的制取样方法精密度（β_S）值和总精密度（β_SPM）值均较小,且符合货物的品质波动规律,表明制得的样品具有较好代表性和可靠性,方法可用于我国进口的红土镍矿取制样。     

Key factors affecting nickel recovery during the segregation of laterite ores

The segregation process as applied to nickel laterite ores involves the formation of gaseous nickel and iron chlorides which are subsequently reduced to form ferronickel on the surface of a solid carbon reductant. A fundamental study of the process has been carried out using limonite, nontronite and garnierite ores. The study highlighted the significant impacts that ore mineralogy and carbon addition have on the amount of nickel which is segregated rather than retained within the ore due to in situ reduction. These important aspects affecting nickel recovery and the success of the process are discussed in this paper.     

低品位褐铁矿型红土镍矿资源化利用与新技术研发现状

在分析新能源车发展现状以及对镍钴需求现状的基础上,详细分析了褐铁矿型红土镍矿资源化利用技术原理、重要技术指标及技术特点,探讨了现有方法的缺点及褐铁矿型红土镍矿资源化利用急需解决的关键技术难题,指出了其未来资源化利用新方向,同时给出了镍铁分离新技术研发现状以及存在的主要问题。     

印尼某褐铁矿型红土镍矿原矿微观结构的探讨

研究对象印尼某红土镍矿为褐铁矿型红土镍矿,具有品位低、成分复杂等特点。为了查明印尼某红土镍矿的微观结构特征从而达到合理且最大程度地回收矿物中Ni、Fe组分,实验利用偏光显微镜、扫描电镜(SEM)、X射线衍射(XRD)和矿物自动解理系统(MLA)等多种测试分析手段对原矿的物相组成、主要矿物的嵌布特征等展开研究。结果表明:100~900℃的温度梯度范围内,该褐铁矿型红土镍矿先后经历了针铁矿脱羟基转变成赤铁矿和铁橄榄石相的形成过程。该印尼红土镍矿中金属矿物主要由针铁矿、铬铁矿、赤铁矿等氧化物组成,脉石矿物主要由石英、铁橄榄石和绿泥石等硅酸盐组成。针铁矿是Ni、Cr、Co、Al的主要赋存矿物,且都是以类质同象的形式代替Fe元素形成的固溶体矿物,该矿物也是后期Ni、Fe分离的目的矿物。     

Pressure Acid Leaching of Nickel Laterites: A Review

Abstract

A review of the literature over the past 30 years on the processing of nickel laterites by high temperature acid leaching has been carried out to provide a better understanding of the mineralogy, leaching process chemistry and effect of operating conditions on nickel recovery, residue properties and scaling. Particular attention is paid to the leaching experience of the commercial Moa Bay plant and to the recently reported testwork and flowsheets associated with the three Western Australia lalerite plants that will be operating in 1999.

It is shown that laterites can vary significantly in their mineralogy according to location, climate and depth, and that the main host minerals for nickel and cobalt can be either goethite (iron oxide) or nontronite (clay) or manganese oxides. The mechanism of leaching involves acid dissolution of the host mineral lattice followed by hydrolysis and precipitation (transformation) of a variety of insoluble oxides and sulphates of iron, aluminium and silica under the high temperature conditions. Optimum leaching conditions and final liquor composition varies according to the ore mineralogy. More fundamental studies have demonstrated that the rate of leaching and character of the residue is dependent upon the level of Mg, Mn and Cr in the ore, the Eh of the slurry and salinity of the process water.

A number of studies are reviewed on the chemistry and precipitation of iron, aluminium, magnesium and silica to understand how the process conditions affect the solubility of the species and the nature of the scale which they form. Early work at Moa Bay indicates that the incorporation of chromium into alunite scale also affects the incorporation of silica and nickel and the settling of the residues. Various types of scale have been identified during different stages of leaching and possible means of minimising scale are discussed.

The clay-rich nickel laterites in Western Australia differ from Moa Bay laterite in mineralogy and have comparatively high silica and low chromium content. Since no commercial plant has previously processed such ores or used saline process water, there is little published in this area. It is therefore recommended that further research be carried out on understanding the process chemistry and species equilibrium from various ore types under autoclave conditions.     

Particulates in hydrometallurgy: Part I. Characterization of laterite acid leach residues

Two different laterite samples, designated as Ore No. 1 and Ore. No. 2, respectively, were leached with sulfuric acid in the temperature range of 25°C to 275°C, in order to evaluate the effects of ore type and leaching conditions (e.g., temperature and solid/liquid ratio) on the settling behavior of the leach residues. The initial solids, as well as the leach residues, were characterized by chemical and physical techniques such as X-ray diffraction, electrophoretic mobility, particle size, and chemical analyses. Spectrochemical and X-ray analyses determined that Ore No. 1 was a limonitic-type (iron oxide-rich ore) material, whereas Ore No. 2 was a transitional laterite ore (silicate-rich, iron oxidecontaining material). By means of X-ray diffraction analysis, it was found that the conversion of goethite to hematite was enhanced as the temperature and/or leaching time was increased. Moreover, it was determined by chemical analysis that as the leaching temperature increased, the concentrations of Ni and Co progressively increased in solution, whereas the impurities (Fe and Al) rose through a maximum and then decreased. This behavior is attributed to the reprecipitation of iron and aluminum from solution as hydrolysis products of hematite and aluminum sulfates. The particle size studies revealed a particle size growth with temperature increase, which is attributed to the deposition of reprecipitation products onto the surface of the solid residues. Investigations of the surface chemistry of the coated particlesvia the electrophoretic mobility technique revealed that the 275°C leach residues (Ore No. 2, pzc ∼2) exhibited a point of zero charge (pzc) near pH 2, which is probably due to the redeposition of the dissolved silica. In contrast, the 250°C leach residues (Ore No. 1, iron oxide-rich ore, pzc∼2) had a pzc value of about 3.8. This shift in mobility to less acidic values suggests that in this case, the insoluble iron and aluminum oxide products on the particles dominate the surface chemistry.     

Preconcentration of Nickel Values from Lateritic Chromite Ore Overburden,Sukinda, Orissa,India

The nickeliferrous chromite ore overburden of Sukinda, Orissa, contains about 0.55% Ni, and forms an important resource for nickel in India. This deposit has hitherto evaded exploitation because of its lean grade and complex mineralogy. The techno-economics of the metallurgical extraction process developed for recovering nickel from this laterite requires a minimum of 1% Ni; hence there is need for preconcentration. This paper presents the results of batch and semi continuous pilot plant scale preconcentration studies carried out on a representative overburden sample. Two alternative flowsheets involving classification and classification-flotation were developed for preconcentrating the nickel rich iron oxide fines (?37 µm). The first flowsheet gave preconcentrate analysing 1% Ni with 50% recovery and with the use of a hydrocyclone of d₅₀(, =30 µm, it should be possible to increase the recovery to > 60%. The second flowsheet gave a preconcentrate analysing 1% Ni with 65% recovery.     

某红土型镍矿中镍钴的赋存状态对其回收的影响

褐铁矿型红土镍矿是一种富含镍、钴、铁的重要资源,综合利用价值巨大。探究红土型镍矿中镍和钴的赋存状态,以深入了解赋存状态对镍和钴回收利用的影响。通过详细的工艺矿物学研究,明确镍和钴主要赋存于褐铁矿、锰的水合氧化物和锰镍矿中,根据该红土型镍矿特征判断最佳冶炼回收方法为高压酸浸工艺。研究为红土型镍矿的资源高效利用提供了重要参考,为相关工业应用和环境保护提供了有益启示。     

Sulfuric acid pressure leaching of nickeliferous limonites

This laboratory study examines the sulfuric acid pressure leaching characteristics of nickeliferous limonite samples from South New Caledonia. The effect of temperature (225°C to 300°C), acid-to-ore ratio (0.21 to 0.30), pct solids (10 to 45), particle size (-20 to -270 mesh), and agitation (50 to 600 rpm) on nickel extraction and selectivity are discussed. For overall improvement of the leach response, leaching is best conducted at temperatures higher than 250°C and at solids less than 33 pct. Variation of goethite, hematite, and basic aluminum sulfate content of the leach residue was determined semiquantitatively as a function of leaching time. Sulfate content of the residue rises sharply during the first several minutes of leaching, then falls, and finally equilibrates at five to six percent. This change in sulfate analysis can be explained by assuming a series of consecutive iron and aluminum hydrolysis reactions.     

镁质氧化镍矿矿相分析及处理工艺选择

借助XRD、TG-DSC、SEM、ICP-OES、光学显微镜和必要化学方法分析云南代表性镁质氧化镍矿。结果表明,矿中氧化镁含量高达31.49%,87%矿物为蛇纹石,铁氧化物仅10%,大于83%的镍以类质同象和吸附方式赋存于硅酸盐矿物中。因含镁量较高,硫酸直接浸出该矿酸耗高达吨矿1.15t。基于该氧化镍矿矿相组成,提出促进剂作用下煤基较低温金属化还原-磁选回收镍铁新技术,镍铁回收率分别从40.27%和42.30%提高到83.46%和74.50%。     

Pressure acid leaching of a Chinese laterite ore containing mainly maghemite and magnetite

The high pressure acid extraction of nickel and cobalt from a Chinese laterite containing mainly maghemite and magnetite was studied. X-ray diffraction (XRD) and scanning electron microscopy/X-ray energy dispersive spectroscopy (SEM/EDS) were employed to characterize the residues. The factors influencing the dissolution of maghemite and magnetite, nickel and cobalt extractions and iron precipitation were investigated. The results show that after 75 min at 270 °C with an acid/ore ratio of 0.55, maghemite and magnetite completely dissolved, liberating 98% Ni and 88% Co into the leach liquor. EDS analysis reveals that some nickel may be associated with the amorphous silica and/or basic ferric sulfate, resulting in a minor loss of nickel. The presence of a cobalt-containing phase in the residues, believed to be ringwoodite, is mainly responsible for the incomplete extraction of cobalt. Both maghemite and magnetite dissolved gradually with the increase in temperature from 200 to 270 °C. Maghemite dissolved more slowly than magnetite at 270 °C which also produced ferrous sulfate in the leach liquor and increased the total iron extraction. Increasing temperature and/or agitation accelerated the hydrolysis of ferric sulfate. The leaching of maghemite and magnetite corresponds to a dissolution-precipitation mechanism. In both high and low acidic environments, the precipitation of ferric sulfate proceeds through the initial formation of basic ferric sulfate and its conversion to hematite. The extent of conversion depends largely upon residual acidity and reaction time.     

Pressure acid leaching of arid-region nickel laterite ore: Part I: effect of water quality

The effect of water salinity on the reactions occurring during pressure acid leaching of an arid-region laterite ore, using hypersaline water, seawater, sub-potable water and tap water, is examined. Particular emphasis is placed on the mineralogy of the residue and its implications with regard to residue volume/mass, overall acid consumption and nickel extraction. Analysis of a pressure acid leach residue by electron microprobe indicates that the residual nickel is present in phases that contain silicon and varying concentrations of aluminium, but are deficient in sulphur. Incomplete extraction of nickel from the ore may not be attributed to any one mineral phase.     

A two-stage thermal upgrading process for nickeliferous limonitic laterite ores

Sulphide ore deposits are becoming increasingly less viable as a source of nickel, driving recent interest in the development of nickel laterite deposits. The difficulties with the current methods of nickel metal production from these oxide ores arise mainly from the inability to produce a concentrate analogous to that obtained in the flotation of sulphide ores, resulting in high production costs. In this work, a two-stage reduction and thermal growth process is proposed for the treatment of the nickeliferous limonitic laterite ores to produce a ferronickel product, recoverable by magnetic separation. An initial reduction roast of the ore with 6% coal and 4% sulphur additions at 600°C for 1?h, followed by particle growth for 1?h at 1000°C, produced a ferronickel concentrate with a nickel grade of 4% and a nickel recovery of 93·2%. The impact of particle growth temperature and retention time at temperature on the ferronickel particle size was also studied. For the control conditions, typical ferronickel particles produced were 10–20?μm in size. The particle size did not significantly change at temperatures higher than 1200°C or for retention times beyond 60?min.     

Sulfuric acid pressure leaching of nickeliferous limonites

This laboratory study examines the sulfuric acid pressure leaching characteristics of nickeliferous limonite samples from South New Caledonia. The effect of temperature (225°C to 300°C), acid-to-ore ratio (0.21 to 0.30), pct solids (10 to 45), particle size (−20 to −270 mesh), and agitation (50 to 600 rpm) on nickel extraction and selectivity are discussed. For overall improvement of the leach response, leaching is best conducted at temperatures higher than 250°C and at solids less than 33 pct. Variation of goethite, hematite, and basic aluminum sulfate content of the leach residue was determined semiquantitatively as a function of leaching time. Sulfate content of the residue rises sharply during the first several minutes of leaching, then falls, and finally equilibrates at five to six percent. This change in sulfate analysis can be explained by assuming a series of consecutive iron and aluminum hydrolysis reactions.     

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...     

La Lixiviation de concentres de sulfures de nickel par le chlorure ferrique

The effectiveness of ferric chloride leaching of nickel sulphide concentrates and of a nickel sulphide matte has been demonstrated. Ferric chloride concentrations ranged from 1 M to 5.7 M for treatment of the concentrates and 0.6 M to 3.8 M for that of the matte; experiments were carried out at 80 ± 1°C.The rate of the reaction was markedly slower after the dissolution of ～ 70% of the Ni. Concentrations of ferric chloride have a significant effect upon the quantity of elemental sulphur obtained. During leaching, a part of the iron from the leachant precipitated out. β-NiS is formed during the treatment of a nickel sulphide matte with ferric chloride.The reaction was followed by continuous measurements of pH, conductivity, redox potential and spectrophotometric intermittent measurements concerning nickel concentrations.     

Precipitate flotation of nickel from acidic laterite leach solutions

Precipitate flotation has been used to preferentially concentrate nickel over iron dissolved in solutions obtained by sulfuric acid leaching of a selectively reduced laterite. Leach solutions, containing about 3 g/L nickel, 0.5 g/L ferrous, 0.5 g/L magnesium, were neutralized using sodium carbonate to give mixed precipitates of a basic nickel carbonate and mainly non-carbonate iron compounds. At the optimum pH of 8.2, stage additions of sodium oleate and Dowfroth 250 (Dow Chemical Company product) totalling 0.07 g/g total nickel and 0.08 g/L solution, respectively, gave flotation recoveries of 93% nickel and 36% iron into concentrates analyzing 41% nickel and 2.8% iron. By neutralizing with sodium hydroxide instead of sodium carbonate, non-selective flotation of nickel and iron is obtained with increased consumption of collector and frother.